bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract B155: The E3 ubiquitin protein ligase MDM2 dictates all-trans retinoic acid induced osteoblastic differentiation of osteosarcoma cells by modulating the degradation of RARα
Authors: Ying Meidan , Zhou Qian , Shao Xuejing , Cao Ji , Zhu Hong , Yang Bo , He Qiaojun
Published: May 2016

Retinoic acid receptor alpha (RARα) plays a critical role in the differentiation process of osteosarcoma cells induced by all-trans retinoic acid (ATRA). However, degradation of RARα through ubiquitin proteasome pathway weakens the differentiation efficiency of osteosarcoma cells. In this study, we discover that murine double minute-2 (MDM2) acts as an E3 ubiquitin ligase to target RARα for degradation. We observe that MDM2 is required for RARα polyubiquitination and proteasomal degradation because downregulation of MDM2 by shRNA results in the accumulation of RARα, and MDM2 overexpression promotes the degradation of RARα. We also demonstrate that the N-terminal domain of MDM2 (amino acids 1-109) is the major RARα-binding site. Importantly, endogenous MDM2 levels are not only upregulated in human primary osteosarcoma blasts, but they are also inversely correlated with the level of OPN, which is a marker of bone differentiation. Moreover, MDM2 impairs the ATRA-induced osteoblastic differentiation of osteosarcoma cells, whereas an inhibitor of the MDM2 ubiquitin ligase synergises with ATRA to enhance the differentiation of osteosarcoma cells and primary osteosarcoma blasts. Therefore, our study indicates that MDM2 serves as an E3 ubiquitin ligase to regulate the degradation of RARα and suggests that MDM2 is a novel therapeutic target for ATRA-based differentiation therapeutic approaches in osteosarcoma.

Citation Format: Meidan Ying, Qian Zhou, Xuejing Shao, Ji Cao, Hong Zhu, Bo Yang, Qiaojun He. The E3 ubiquitin protein ligase MDM2 dictates all-trans retinoic acid induced osteoblastic differentiation of osteosarcoma cells by modulating the degradation of RARα. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B155.
Abstract B157: YAP is a promising target in cutaneous melanoma
Authors: Tang Jian zhong , Zhang Xiaomeng , Vergara Ismael , Papenfuss Anthony , Harvey Kieran , Shackleton Mark
Published: May 2016

The transcriptional regulator YAP (Yes-associated protein) has been implicated in tissue development and homeostasis and in cancer growth (Harvey et al. 2013). In uveal melanoma, YAP mediates oncogenic signaling of mutated G-proteins, driving tumor growth in a therapeutically exploitable manner (Yu et al. & Feng et al. 2014). The role of YAP in cutaneous melanoma (CM) is less well defined, although previous studies implicating YAP in metastasis and disease maintenance/progression (Nallet-Staub et al. 2014; Menzel et al. 2014), and encouraging data suggesting synergism between combination targeting of YAP and the Mitogen-Activated Protein Kinases (MAPK) pathway (Lin et al. 2015).

Here we show that YAP is a critical mediator of disease maintenance and progression in some but not all CMs. In a primary CM we identified novel YAP mutations, which are rare in human cancer but are predicted to relieve YAP from inhibition by the Hippo pathway. By quantifying YAP expression by immunofluorescence, we found YAP was increased early in human melanocytic transformation, being elevated in nevi and in over 50% of primary CMs. Gene targeting of YAP with inducible shRNAs induced profound proliferative arrest and death in cultured CM cells (measured by MTT assay, EdU incorporation and propidium iodide staining respectively). The dependency on YAP of melanoma maintenance was validated in vivo using xenograft models of cell lines and of early passage patient-derived melanomas. Further, efficacy of YAP targeting synergized with MAPK inhibition in BRAF mutant CMs. However, some CMs were resistant to YAP targeting independent of BRAF/NRAS genotype and of levels of YAP protein expression or activation.

These data compel the development of anti-YAP therapies in CM and the identification of biomarkers that predict response to YAP targeting.

Citation Format: Jian zhong Tang, Xiaomeng Zhang, Ismael Vergara, Anthony Papenfuss, Kieran Harvey, Mark Shackleton. YAP is a promising target in cutaneous melanoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B157.
Abstract B166: A RNA helicase siRNA screen to identify potential therapeutic targets in castration-resistant prostate cancer
Authors: Wang Hannah , de Billy Emmanuel , de Bono Johann , Workman Paul
Published: May 2016

Castration-resistant prostate cancers (CRPC) are resistant to androgen-deprivation therapies commonly used to treat carcinoma of the prostate, resulting in death from this disease. CRPC can remain AR-driven through upregulation of the expression of wild-type, mutated or alternatively spliced constitutively active AR. Targeting both full-length AR and AR splice variants may overcome endocrine resistance. Since RNA helicases play crucial roles in various aspects of RNA metabolism including transcription, pre-mRNA splicing, translation, RNA export and RNA decay, we evaluated potentially druggable RNA helicases implicated in the regulation of AR and AR-V7 expression. We performed an siRNA screen targeting RNA helicases in which the readout was the expression of AR and AR-V7 mRNA as determined by quantitative RT-PCR. Out of the 75 human RNA helicases silenced, we identified 11 that induced a 50% or greater decrease in both AR and AR-V7 mRNA expression. These included 3 RNA helicases that have no known described function, 2 that regulate ribosomal RNA transcription, 3 required in nuclear export of spliced and unspliced mRNA, 2 in translation initiation and the DEAD-box helicase EIF4A3 involved in nonsense-mediated decay. Among these, only EIF4A3 reduced cell numbers by 40% in addition to decreasing AR and AR-V7 expression. Silencing EIF4A3 resulted in a 50-80% inhibition of cell proliferation and between 2- to 11-fold induction of apoptosis in a panel of 6 prostate cancer cell lines. Inhibiting EIF4A3 in CRPC may block the expression of important oncogenes including AR and counteract the emergence of splice variants involved in resistance mechanisms.

Citation Format: Hannah Wang, Emmanuel de Billy, Johann de Bono, Paul Workman. A RNA helicase siRNA screen to identify potential therapeutic targets in castration-resistant prostate cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B166.
Abstract B194: Tivantinib in combination with erlotinib vs erlotinib alone for EGFR mutant NSCLC: Subgroup results from the phase 3 MARQUEE study
Authors: Scagliotti Giorgio V. , Orlov Sergey , von Pawel Joachim , Shepherd Frances A. , Akerley Wallace , Ross Jeffrey S. , Shuster Dale , Wang Qiang , Schwartz Brian , von Roemeling Reinhard
Published: May 2016

This abstract has been withheld from publication due to its inclusion in the AACR-NCI-EORTC Molecular Targets Conference 2015 Official Press Program. It will be posted online at the time of its presentation in a press conference or in a session: 10:00 AM ET Saturday, November 7.

Citation Format: Giorgio V. Scagliotti, Sergey Orlov, Joachim von Pawel, Frances A. Shepherd, Wallace Akerley, Jeffrey S. Ross, Dale Shuster, Qiang Wang, Brian Schwartz, Reinhard von Roemeling. Tivantinib in combination with erlotinib vs erlotinib alone for EGFR mutant NSCLC: Subgroup results from the phase 3 MARQUEE study. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B194.
Abstract B48: Identification of potent, cell active MTH1 inhibitors and their use in target validation studies
Authors: Leo Elisabetta , Petrocchi Alessia , Bardenhagen Jennifer , Alimova Maria , Shi Xi , Parker Connor , Reyna Naphtali , Hamilton Matthew , Felix Edward , Mazan Andrzej , Dillon Christian , Mseeh Faika , Marszalek Joseph R. , Toniatti Carlo , Draetta Giulio , Jones Phil , Lewis Richard T.
Published: May 2016

MTH1 is a protein that sanitizes oxidized dNTPs in the cell. It preferentially hydrolyzes 8-oxo-dGTP and 2-OH-dATP to their corresponding monophosphates and thereby prevents the incorporation of oxidized nucleotides into DNA or RNA. The functional result is a reduction in down-stream mutations, or DNA damage, thus preventing cell death. Recent publications suggest that MTH1 is a non-essential enzyme in normal cells, but is required for the survival of cancer cells as a consequence of being subjected to high levels of oxidative stress; hence its relevance as an oncology target. Gad et al., 2014

The interesting target rationale combined with a perceived high chemical tractability of the target resulting from availability of x-ray crystallographic information for the protein, led to a decision to undertake, in parallel, target validation, assay development and drug discovery. This effort resulted in the structure-based design of potent, cell active MTH1 small molecule inhibitors. This poster will describe the discovery and optimization of these inhibitors, and their use to evaluate the potential of MTH1 as an oncology target. This work was complemented by parallel genetic studies. Pharmacodynamic evaluation of target engagement using proximal biomarkers will be presented, as will phenotypic responses across a range of cancer cell lines.

Citation Format: Elisabetta Leo, Alessia Petrocchi, Jennifer Bardenhagen, Maria Alimova, Xi Shi, Connor Parker, Naphtali Reyna, Matthew Hamilton, Edward Felix, Andrzej Mazan, Christian Dillon, Faika Mseeh, Joseph R. Marszalek, Carlo Toniatti, Giulio Draetta, Phil Jones, Richard T. Lewis. Identification of potent, cell active MTH1 inhibitors and their use in target validation studies. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B48.
Abstract B55: High expression of CDK6 protects breast cancer cells from fulvestrant-mediated apoptosis and is a predictor of resistance to fulvestrant treatment in estrogen receptor-positive metastatic breast cancer
Authors: Alves Carla L. , Elias Daniel , Lyng Maria , Bak Martin , Lykkesfeldt Anne , Ditzel Henrik J.
Published: May 2016

Resistance to endocrine therapy in estrogen receptor-positive (ER+) breast cancer remains a major clinical problem. Recently, the CDK4/6 inhibitor palbociclib combined with letrozole was approved for treatment of ER+ advanced breast cancer, and other CDK4/6 inhibitors are also being investigated in clinical trials in combination with different endocrine treatments, including fulvestrant. However, the role of CDK4/6 in endocrine resistance and their potential as predictive biomarkers of endocrine treatment response remains to be defined. We evaluated the expression of genes of the cyclin D/CDK4-6/p16INK4A/Rb pathway in a panel of endocrine-resistant breast cancer cell lines by gene array and found increased expression of CDK6 in two fulvestrant-resistant cell models vs. sensitive cells. Reduction of CDK6 expression by specific gene knockdown impaired fulvestrant-resistant cells growth and induced apoptosis by reducing p70 ribosomal S6 kinase 2 activity. Treatment with palbociclib re-sensitized fulvestrant-resistant cells to fulvestrant through alteration of retinoblastoma phosphorylation. Evaluation of CDK6 expression levels in metastatic samples from breast cancer patients treated with fulvestrant (N = 45) showed that high levels of CDK6 correlated significantly with shorter progression-free survival (PFS) (p = 0.0006), while no association was observed between CDK6 levels and PFS in patients receiving other endocrine treatments (N = 41, p = 0.874). Our results indicate that upregulation of CDK6 may be an important mechanism in overcoming fulvestrant-mediated growth inhibition in breast cancer cells. Patients with advanced ER+ breast cancer exhibiting high CDK6 expression in the metastatic lesions show shorter PFS upon fulvestrant treatment and thus may benefit from the addition of CDK4/6 inhibitors in their therapeutic regimens.

Citation Format: Carla L. Alves, Daniel Elias, Maria Lyng, Martin Bak, Anne Lykkesfeldt, Henrik J. Ditzel. High expression of CDK6 protects breast cancer cells from fulvestrant-mediated apoptosis and is a predictor of resistance to fulvestrant treatment in estrogen receptor-positive metastatic breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B55.
Abstract B65: High levels of expression of P-glycoprotein/multidrug resistance protein result in resistance to vintafolide
Authors: Guertin Amy D. , O'Neil Jennifer , Stoeck Alexander , Reddy Joseph A. , Cristescu Razvan , Haines Brian B. , Hinton Marlene C. , Dorton Ryan , Bloomfield Alicia , Nelson Melissa , Vetzel Marilynn , Lejnine Serguei , Nebozhyn Michael , Zhang Theresa , Loboda Andrey , Picard Kristen L. , Schmidt Emmett V. , Dussault Isabelle , Leamon Christopher P.
Published: May 2016

Targeting surface receptors overexpressed on cancer cells is one way to specifically treat cancer versus normal cells. Vintafolide (EC145), which consists of folate linked to a cytotoxic small molecule, desacetylvinblastine hydrazide (DAVLBH), takes advantage of the overexpression of folate receptor (FR) on cancer cells. Once bound to FR, vintafolide enters the cell by endocytosis, and the reducing environment of the endosome cleaves the linker, releasing DAVLBH to destabilize microtubules. Vintafolide has shown efficacy and improved tolerability compared to DAVLBH in FR-positive preclinical models. As the first FR-targeting drug to reach the clinic, vintafolide has achieved favorable responses in Phase II clinical trials in FR-positive ovarian and lung cancer. However, some FR-positive patients in these clinical trials do not respond to vintafolide. We sought to identify potential biomarkers of resistance to aid in the future development of this and other FR-targeting drugs. Here, we confirm in both in vitro and in vivo preclinical models that high P-glycoprotein (P-gp) expression was the strongest predictor of resistance to DAVLBH in a panel of 359 cancer cell lines. Furthermore, targeted delivery of DAVLBH via the FR as in vintafolide fails to overcome P-gp mediated efflux of DAVLBH as seen in FR-expressing engineered cell lines and in vivo models. Therefore, we suggest that patients whose tumors express high levels of P-gp be excluded from future clinical trials for vintafolide as well as other FR-targeted therapeutics bearing a P-gp substrate.

Citation Format: Amy D. Guertin, Jennifer O'Neil, Alexander Stoeck, Joseph A. Reddy, Razvan Cristescu, Brian B. Haines, Marlene C. Hinton, Ryan Dorton, Alicia Bloomfield, Melissa Nelson, Marilynn Vetzel, Serguei Lejnine, Michael Nebozhyn, Theresa Zhang, Andrey Loboda, Kristen L. Picard, Emmett V. Schmidt, Isabelle Dussault, Christopher P. Leamon. High levels of expression of P-glycoprotein/multidrug resistance protein result in resistance to vintafolide. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B65.
Abstract B95: PDL-1 is more frequently expressed on circulating epithelial tumor cells (CETCs) in metastatic than in non-metastatic breast cancer patients and could be a crucial factor in the inhibition of immune response to CETCs during metastasis formation
Authors: Pizon Monika , Zimon Dorothea , Pachmann Ulrich , Pachmann Katharina
Published: May 2016

Background:

Analysis of CETCs is a promising diagnostic field for estimating the risk for metastatic relapse and progression. The phenotypic characterization of CETCs may provide real time information and can be of great value in therapy monitoring. Programmed cell death ligand 1 (PDL-1) is an important protein frequently upregulated in a number of different cancers. Cancer cells expressing PDL-1 inhibit immune-modulatory T-cell activation allowing disease progression. Therefore this immune checkpoint has emerged as an important target for immune therapy. The purpose of the current study was to identify potential patients who may benefit from PDL-1 targeted immunotherapies.

Methods:

CETCs were determined from blood of 22 (69%) non-metastatic and 10 (31%) metastatic breast cancer patients. The number of vital CETCs and the expression of PDL-1 were investigated using the maintrac® method.

Results:

PDL-1 expressing CETCs were detected in 94% of breast cancer patients; however the fraction varied between 30 to 100% in individual patients. There was no association between the frequency of PDL-1 positive CETCs and chemotherapy. Interestingly, we found a relationship between the frequencies of PDL-1 positive CETCs and progression of disease. Patients with metastatic disease had more PDL-1 positive CETCs as compared to patients without metastasis.

Conclusion:

Metastatic breast cancer patients have an elevated fraction of PDL-1 positive CETCs as compared to non-metastatic patients. These cells have the capacity to block the immune system and therefore may be a promising target for anticancer therapies. Monitoring the frequency of PDL-1 positive CETCs could contribute to individual patient's response for to anti-PDL-1 therapy.

Citation Format: Monika Pizon, Dorothea Zimon, Ulrich Pachmann, Katharina Pachmann. PDL-1 is more frequently expressed on circulating epithelial tumor cells (CETCs) in metastatic than in non-metastatic breast cancer patients and could be a crucial factor in the inhibition of immune response to CETCs during metastasis formation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B95.
Abstract C104: TAS-121, a highly potent and mutant-specific EGFR inhibitor, modulates the immune system, resulting in anti-tumor immune responses
Authors: Fukaya Satoshi , Aoyagi Yoshimi , Katoh Masanori , Itoh Kimihiro , Shibutani Toshihiro , Tanaka Nozomu , Haruma Tomonori , Hashimoto Akihiro , Miyadera Kazutaka , Matsuo Kenichi , Iwasawa Yoshikazu , Utsugi Teruhiro , Yonekura Kazuhiko
Published: May 2016

Background:

TAS-121 is one of the 3rd generation EGFR TKI, which specifically inhibits mutant EGFRs, and it leads to high cellular selectivity and potent antitumor activity in various in vivo models. TAS-121 is being investigated in patients with non-small cell lung cancer (NSCLC) harboring not only active mutant EGFR, but also acquired resistance mutation T790M in phase I study. immune-related events observed during treatment with TAS-121 in preclinical and clinical studies suggested that TAS-121 could modulate the immune system and, consequently, might partially contribute to anti-tumor effect. To prove this hypothesis, we examined the immuno-modulating potential of TAS-121 using MLR assay, TCR stimulation assay and in vivo syngeneic tumor models.

Material and methods:

Immune cell proliferation and cytokine production were confirmed by the CFSE dilution using flow cytometry, and ELISA assay, respectively. Anti-tumor immune response was analyzed in syngeneic models bearing with MC38 murine colon carcinoma cell line.

Results:

TAS-121 strongly induced the proliferation of CD4 T cells and CD8 T cells as well as stimulating cytokine production. Other EGFR TKIs, including 1st generation to 3rd generation agents, didn't show these effects. TAS-121 inhibited the growth of syngeneic tumor, MC38 in vivo, while no growth inhibition was observed in vitro. These data demonstrate that TAS-121 can induce anti-tumor immune responses.

Conclusions:

These findings suggest that TAS-121 could specifically modulate the immune system including T cells, leading to the anti-tumor immune responses. Therefore, TAS-121 has a unique profile among the 3rd generation EGFR-TKI. Considering this immune-modulating profile, combination with immune checkpoint blockade agent such as anti-PD1 monoclonal antibody might be beneficial for NSCLC patients harboring mutant EGFR.

Citation Format: Satoshi Fukaya, Yoshimi Aoyagi, Masanori Katoh, Kimihiro Itoh, Toshihiro Shibutani, Nozomu Tanaka, Tomonori Haruma, Akihiro Hashimoto, Kazutaka Miyadera, Kenichi Matsuo, Yoshikazu Iwasawa, Teruhiro Utsugi, Kazuhiko Yonekura. TAS-121, a highly potent and mutant-specific EGFR inhibitor, modulates the immune system, resulting in anti-tumor immune responses. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C104.
Abstract C134: Alternative pathways associated with resistance to tyrosine kinase inhibitors in glioblastoma
Authors: Aljohani Hashim M. , Koncar Robert F. , Zarzour Ahmed , Sun Park Byung , Lee So Ha , Bahassi El Mustapha
Published: May 2016

Glioblastoma (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. The majority of GBM tumors show a mutated or overexpressed EGFR. However, the kinase domain mutations that usually correlate with response to the tyrosine kinase inhibitors in other cancers are infrequent in glioblastomas and phase II trials of the tyrosine kinase inhibitor (TKI), gefitinib showed no survival benefit in glioblastoma. Furthermore, tumors treated with the TKIs will inevitably recur, highlighting the need to identify signaling pathways involved in GBM resistance to TKIs. We isolated and developed gefitinib-resistant cell lines and subjected those cell lines to RNA sequencing. By evaluating transcriptomic profiles of the resistant cell lines, we were able to identify several upregulated genes, including a number of other tyrosine kinase receptors such as ROS1, DDR1 and PDGFRA that are known to control pathways downstream of EGFR. The upregulation of these genes was confirmed at the protein level by western blot. Treatment with our highly specific pyrazole ROS1 inhibitor in ROS1-overexpressing cell lines led to sensitization to low doses of gefitinib. Combined treatment with gefitinib and ROS1 inhibitor induced massive cell death by apoptosis following a prolonged cell cycle arrest in S phase. Our current study led to the discovery of alternative pathways used by GBM cells to evade cell death following treatment with gefitinib and identifies new therapeutic targets to prevent GBM cell resistance to the drug.

Citation Format: Hashim M. Aljohani, Robert F. Koncar, Ahmed Zarzour, Byung Sun Park, So Ha Lee, El Mustapha Bahassi. Alternative pathways associated with resistance to tyrosine kinase inhibitors in glioblastoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C134.
Abstract C138: Targeting macropinocytosis in pancreatic cancer
Authors: Hunt James , Ng Serina , Whatcott Clifford , Von Hoff Daniel D. , Han Haiyong
Published: May 2016

Pancreatic cancer is the fourth-leading cause of cancer-related deaths in the United States with a 5-year survival rate of <5%. The deadly nature of this disease compounded by a lack of effective treatment options highlights a need for new therapeutics. Past studies have suggested that pancreatic cancer cells acquire the nutrients needed for cell growth through macropinocytosis, an endocytic process by which protrusions from the cell membrane create large vesicles that transport extracellular fluid along with the constituent proteins and lipids into the cell. Additionally, several studies have suggested that macropinocytosis is regulated in part by various genes including p21 protein (Cdc42/Rac)-activated kinase1 (PAK1), ADP-ribosylation factor 6 (ARF6), and sorting nexin 5 (SNX5). In this study, we investigated the effects of knockdown of these three genes on the macropinocytic activity of pancreatic cancer cells. The goal of this study is to assess whether PAK1, ARF6, or SNX5 may serve as potential targets for the suppression of macropinocytosis in pancreatic cancer, which would hamper the cells' uptake of nutrients thus starving the cancer cells and hindering tumor growth. We carried out this study using MIA PaCa-2 pancreatic cancer cells, which are known to exhibit relatively high levels of macropinocytosis. Treatment of cells with siRNA sequences specific to the three genes resulted in a significantly decreased uptake of FITC-labeled dextran as compared to cells treated with non-targeting siRNA and cells that received no treatment, indicating that inhibiting the expression of each of the genes correlates to a reduction in macropinocytic activity. Among the three genes, PAK1 siRNAs exhibited the most significant and consistent inhibitory effect on macropinocytic activity of MIA PaCa-2 cells. We, therefore, further tested the effect of two small-molecule PAK1 inhibitors, namely IPA-3 and PF-03758309, on macropinocytosis. Treatment of cells with the inhibitors resulted in a dose-dependent decrease in the uptake of FITC-labeled dextran and FITC-labeled albumin. The inhibitors also showed potent anti-proliferative activity in pancreatic cancer cell lines. The results of this study indicate that inhibition of PAK1, ARF6, or SNX5 all resulted in reduced macropinocytic activity of pancreatic cancer cells, with PAK1 showing the most promise as a potential therapeutic target for pancreatic cancer.

Citation Format: James Hunt, Serina Ng, Clifford Whatcott, Daniel D. Von Hoff, Haiyong Han. Targeting macropinocytosis in pancreatic cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C138.
Abstract C143: Utility of growth modulation index and tumor growth rate to evaluate efficacy in metastatic gastric cancer patients
Authors: Beom Seung-Hoon , Jung Minkyu , Kim Hyo Song , Ahn Joong Bae , Rha Sun Young , Chung Hyun Cheol
Published: May 2016

Background

Growth modulation index (GMI) and tumor growth rate (TGR) have been proposed as signs of activity in early phase clinical trials. We explored utility of the efficacy end points in metastatic gastric cancer.

Patients and Methods

We carried out a retrospective study in metastatic gastric cancer patients receiving weekly paclitaxel regimen as second or more line treatment between 2005 and 2013 in Yonsei Cancer Center, and evaluate the association of GMI and TGR with efficacy outcomes respectively. The growth modulation index (GMI) was defined the ratio of time to progression with the nth line (TTPn) of therapy to the TTPn−1 with the n-1th line. TGR was computed during the pretreatment period (reference) and the experimental period. Comparisons used chi-squared and log-rank tests.

Results

A total of 133 patients were enrolled in this study. The median TTPn was 2.7 months, whereas the median TTPn−1 was 5.3 months. Thirty-one patients experienced GMI > 1.2 (23.3%). Median OS was highly correlated with GMI: 6.3 and 7.5 months with GMI ≤ 1.2 and GMI > 1.2 (P = 0.0009). TGR could be evaluated in 52 patients. Among them, 37 patients (71.1%) exhibited a decrease in TGR. The decrease of TGFR was associated with PFS (P = 0.043) and OS (P = 0.045).

Conclusions

GMI and TGR seem to be interesting end points that provides additional information compared with classical criteria. GMI >1.2 and decrease of TGR are associated with significant OS improvement.

Citation Format: Seung-Hoon Beom, Minkyu Jung, Hyo Song Kim, Joong Bae Ahn, Sun Young Rha, Hyun Cheol Chung. Utility of growth modulation index and tumor growth rate to evaluate efficacy in metastatic gastric cancer patients. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C143.
Abstract C150: High expression of SNAI2 is associated with the emergence of a highly motile fulvestrant-resistant phenotype and is an indicator of poor response to endocrine treatment in estrogen receptor-positive metastatic breast cancer
Authors: Alves Carla L. , Elias Daniel , Lyng Maria , Bak Martin , Lykkesfeldt Anne E. , Ditzel Henrik J.
Published: May 2016

Endocrine resistance is a major clinical problem and is associated with the acquisition of aggressive tumor spread and invasion. To investigate the association between endocrine resistance and tumor cell migration and invasion, we evaluated a panel of MCF7-based cell line models resistant to either tamoxifen, aromatase inhibitors or fulvestrant. Fulvestrant-resistant cell lines showed a significantly higher migration capacity than the parental fulvestrant-sensitive cell line. Gene expression profiling and data analysis using Ingenuity Pathway Analysis (IPA) of these fulvestrant-resistant/fulvestrant-sensitive cell lines identified potential genes involved in the promotion of invasive and aggressive characteristics in the fulvestrant-resistant phenotype, including SNAI2, a transcription repressor that promotes epithelial-mesenchymal transition and tumor metastasis. The higher gene and protein expression levels of SNAI2 in fulvestrant-resistant cells were confirmed by RT-qPCR, Western blotting and immunocytochemistry. Specific gene silencing using small interfering RNA (siRNA) against SNAI2 decreased the migratory capacity of fulvestrant-resistant cells in vitro. Clinical evaluation of SNAI2 expression in estrogen receptor-positive (ER+) metastatic tumor samples from patients treated with endocrine drugs in the advanced setting (N = 86) showed that tumors with higher expression of SNAI2 correlated significantly with shorter progression-free survival (p = 0.001). Our results suggest that upregulation of SNAI2 is associated with the emergence of a highly motile fulvestrant-resistant phenotype in vitro and may be a potential therapeutic target in combination with endocrine therapies in tumors expressing high levels of SNAI2.

Citation Format: Carla L. Alves, Daniel Elias, Maria Lyng, Martin Bak, Anne E. Lykkesfeldt, Henrik J. Ditzel. High expression of SNAI2 is associated with the emergence of a highly motile fulvestrant-resistant phenotype and is an indicator of poor response to endocrine treatment in estrogen receptor-positive metastatic breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C150.
Abstract C163: Understanding the mechanism for synergistic anti-tumor activity of a meosthelin-targeted immunotoxin and taxanes
Authors: Alewine Christine Campo , Kolyvas Emily , Pastan Ira
Published: May 2016

Recombinant immunotoxins (RITs) are antibody-based therapies that carry a bacterial toxin payload. RG7787 is a next generation RIT that targets the cancer antigen mesothelin (MSLN) to deliver a recombinantly engineered variant of Pseudomonas exotoxin A (PE) into the cell cytosol. PE irreversibly modifies elongation factor-2 (EF-2) by catalyzing addition of an ADP-ribose moiety. This causes EF-2 inactivation, inhibition of new protein synthesis, and a drop in the short-lived pro-survival factor mcl-1, triggering apoptosis. Combination of RG7787 with paclitaxel or nab-paclitaxel results in boosted anti-tumor efficacy in several mouse models. In the KLM1 pancreatic cancer xenograft model, either drug alone halts tumor growth while the combination produces complete regressions. Here, we show that enhanced efficacy is also seen using an identically structured RIT that targets the transferrin receptor instead of mesothelin (LMB-74), but is not seen when RIT is combined with gemcitabine, suggesting that the effect is specific to both taxane and PE. Further, we have found that the interaction of RG7787 and taxane can be modeled in vitro. Under these conditions, the interaction is dependent on the dose of RG7787, and cannot be replicated by a chemical inhibitor of protein synthesis. Co-treatment with taxane does not affect the depth, rate of onset or recovery of cells from RG7787-mediated protein synthesis inhibition. Tumor cell killing occurs over a delayed time course and is not associated with an early drop in mcl-1 levels as is seen when using a cytotoxic dose of RG7787 alone. Taken together, these data suggest that PE treatment sensitizes cancer cells to taxane-mediated killing.

Citation Format: Christine Campo Alewine, Emily Kolyvas, Ira Pastan. Understanding the mechanism for synergistic anti-tumor activity of a meosthelin-targeted immunotoxin and taxanes. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C163.
Abstract C169: ER maleate is a novel anticancer agent in oral cancer cells: Implications for cancer therapy
Authors: Fu Guodong
Published: May 2016

ER maleate was investigated as a novel anticancer agent for oral squamous cell carcinoma (OSCC), the most common head and neck squamous cell carcinoma (HNSCC). We identified its putative molecular targets, demonstrated their clinical relevance, and showed its chemosensitization potential for platinum drugs to aid in HNSCC management. Biologic effects of ER maleate were determined on cell proliferation, spheroid/colony formation, caspase activity, cell migration and invasion in vitro and using oral tumor xenografts in vivo. mRNA profiling, real time PCR and western blot suggested ER maleate modulated the expression of polo-like kinase 1 (PLK1) and spleen tyrosine kinase (Syk). Their clinical significance was determined in oral SCC patients by immunohistochemistry and correlated with prognosis by Kaplan-Meier survival analysis. ER maleate induced cell apoptosis, inhibited proliferation, colony formation, migration and invasion in oral cancer cells. Imagestream analysis revealed cell cycle arrest in G2/M phase and increased polyploidy, unravelling deregulation of cell division and cell death. Mechanistically, ER maleate decreased expression of PLK1 and Syk, induced cleavage of PARP, caspase 9 and caspase 3 and increased chemosensitivity to carboplatin; significantly suppressed tumor growth and increased antitumor activity of carboplatin in tumor xenografts. ER maleate treated tumor xenografts showed reduced PLK1 and Syk expression; clinical investigations revealed overexpression of PLK1 and Syk in oral SCC patients that correlated with disease prognosis. In conclusion, our in vitro and in vivo findings provide a strong rationale for pre-clinical efficacy of ER maleate as a novel anti-cancer agent and chemosensitizer of platinum drugs for OSCC.

Citation Format: Guodong Fu, Sr.. ER maleate is a novel anticancer agent in oral cancer cells: Implications for cancer therapy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C169.
Abstract C174: RAF kinase dimerization mediates clinical acquired resistance to RAF/EGFR inhibition in BRAF V600E colorectal cancer
Authors: Yaeger Rona , Yao Zhan , Hyman David M. , Hechtman Jaclyn F. , Vakiani Efsevia , Cercek Andrea , Baselga Jose , DeStanchina Elisa , Saltz Leonard , Berger Michael F. , Solit David B. , Rosen Neal
Published: May 2016

Background: RAF and EGFR inhibitor combinations have shown promising clinical activity in patients with BRAF V600E colorectal cancer, but resistance invariably develops.

Methods: To define mechanisms of resistance to RAF/EGFR inhibition, we analyzed pre-treatment and disease progression samples from patients with BRAF mutant colorectal cancer using our custom next-generation sequencing platform, MSK-IMPACT (Integrated Mutation Profiling of Actionable Cancer Targets). Cell line and patient derived xenograft models were generated to investigate the effects of the genetic alterations identified at disease progression.

Results: We identified alterations predicted to result in RAF dimerization and re-activation of ERK signaling in seven of eight post-progression tumors. These alterations included an intragenic deletion in BRAF encompassing the RAS binding domain, KRAS and NRAS mutations, and KRAS, NRAS, and BRAF amplifications. Notably, these alterations were rapidly enriched in the presence of drug treatment but selected against in the absence of drug exposure. A novel RAF inhibitor, that equipotently inhibits RAF mutant monomers and dimers, effectively suppressed ERK signaling in the RAF/EGFR resistant colorectal tumors at drug doses that did not inhibit ERK signaling in RAS/RAF wild-type cells. Treatment with this novel RAF inhibitor was able to overcome resistance in cell line and patient derived xenograft models.

Conclusions: Our data suggest that alterations that promote RAF dimers, which are resistant to first generation RAF inhibitors, are a unifying mechanism of RAF/EGFR inhibitor resistance in patients with BRAF mutant colorectal cancer. These results support the testing of RAF dimer inhibitors in combination with EGFR inhibitors in patients with BRAF V600E colorectal cancer.

Citation Format: Rona Yaeger, Zhan Yao, David M. Hyman, Jaclyn F. Hechtman, Efsevia Vakiani, Andrea Cercek, Jose Baselga, Elisa DeStanchina, Leonard Saltz, Michael F. Berger, David B. Solit, Neal Rosen. RAF kinase dimerization mediates clinical acquired resistance to RAF/EGFR inhibition in BRAF V600E colorectal cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C174.
Abstract C183: Pomhex: a cell-permeable high potency Enolase inhibitor with in vivo anti-neoplastic activity
Authors: Lin Yu-Hsi , Marszalek Joe , Sun Yuting , Hammoudi Naima , Leonard Paul , Maxwell David , Satani Nikunj , Zhang Peng , Link Todd , Lee Gilbert , Di Francesco Maria E. , Czako Barbara , Want Alan Y. , DePinho Ronald A. , Muller Florian L.
Published: May 2016

Glycolysis inhibition is an active area of investigation in cancer. However, few compounds have progressed beyond the cell culture stage. We have recently demonstrated that genomic passenger deletion of the glycolytic enzyme Enolase 1 (ENO1) leaves gliomas harboring such deletions with less than 10% of normal enzymatic activity, rendering them exquisitely sensitive to enolase inhibitors. However, the tool compound that we employed for these in vitro studies, Phosphonoacetohydroxamate (PhAH), has very poor pharmacological properties and was ineffective in vivo. We performed a SAR studies to increase inhibitor specificity towards ENO2 as well as pro-druging to increase cell permeability. The lead compound generated by these efforts, termed POMHEX, is selectively active against ENO1-deleted glioma cells in culture at ∼35nM (versus μM for PhAH). Using an orthotopic intracranial xenografted model where tumor growth and response to therapy are monitored by MRI, we show that POMHEX is capable of eradicating intracranial ENO1-deleted tumors, with mice remaining recurrence-free even after treatment discontinuation. Taken together, these results reinforce that glycolysis is a viable target and provide in vivo proof-of-principal for the concept of using passenger deletions as targetable vulnerabilities in cancer therapy.

Citation Format: Yu-Hsi Lin, Joe Marszalek, Yuting Sun, Naima Hammoudi, Paul Leonard, David Maxwell, Nikunj Satani, Peng Zhang, Todd Link, Gilbert Lee, Maria E. Di Francesco, Barbara Czako, Alan Y. Want, Ronald A. DePinho, Florian L. Muller. Pomhex: a cell-permeable high potency Enolase inhibitor with in vivo anti-neoplastic activity. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C183.
Abstract C189: Defective S phase cell cycle checkpoint: A potential culprit and target in melanoma
Authors: Oo Zay Y. , Daignault Sheena , Chen James , Gabrielli Brian
Published: May 2016

The S phase cell cycle checkpoint is critical for maintaining genomic integrity. This checkpoint is triggered in response to DNA damage and replication stresses to control cell cycle progression, halting DNA replication and allowing the time to repair to maintain genomic integrity. If this checkpoint is defective, cells lose their ability to ensure the fidelity of replication and repair any damage, resulting in replicative stress and genomic instability which will subsequently increase the risk of cancer. We have discovered that a large proportion of melanoma cell lines lose the ability to halt replication when challenged with high dose hydroxyurea-induced replicative stress, despite normal cell cycle checkpoint signalling. We found that failure in the crosstalk between ATR-CHK1 checkpoint signalling and the cell cycle mechanism in destabilization of CDC25A. Although CHK1-dependent phosphorylation of CDC25A which triggers its degradation was detected, the S phase checkpoint defective melanoma cell lines fail to destabilize CDC25A, maintaining normal activation of CDK2/Cyclin E. The melanoma cells with this S phase checkpoint defect are also hyper-sensitive to killing by CHK1 inhibitor. We have previously shown that melanoma with high levels of replicative stress are very sensitive to CHK1 inhibitors. I will report our studies investigating whether CHK1 inhibitor sensitivity is a direct outcome of the replicative stress arising from the S phase checkpoint defect, or whether the loss of the ATR-CHK1-CDC25A dependent S phase checkpoint signalling mechanism is directly responsible for the hyper-sensitivity to CHK1 inhibitors.

Citation Format: Zay Y. Oo, Sheena Daignault, James Chen, Brian Gabrielli. Defective S phase cell cycle checkpoint: A potential culprit and target in melanoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C189.
Abstract C193: Combining ibrutinib with Chk1 inhibitors as a new therapeutic strategy for mantle cell lymphoma
Authors: Restelli Valentina , Vagni Micaela , Lupi Monica , Bertoni Francesco , Damia Giovanna , Carrassa Laura
Published: May 2016

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma characterized by an initial high response to first line treatment, followed by a continuous relapse, resulting in a discouraging long term outcome. Recently a novel potent inhibitor of BTK, ibrutinib, was found to induce impressive response in B-cell malignancies and has been approved for therapy of refractory mantle cell lymphoma. BTK (bruton's tyrosine kinase) is required for B cell receptor signaling (BCR) and is essential for B cell development, differentiation, signaling and survival. Despite its unprecedented clinical activity, acquired resistance to ibrutinib also develops, pushing the evaluation of new drug combinations. We have recently shown that Chk1 inhibitors (PF-00477736) not only are very effective as single agents in MCL but are strongly synergistic with Wee1 inhibitors. We tested ibrutinib in combination with PF-00477736 in different MCL cell lines (JVM2, JEKO-1, MAVER-1, GRANTA-519, REC1), finding that the combination is synergistic in all these cell lines, with Combination Index values, evaluated at the IC50 doses, ranging from 0.5 to 0.7. The combination was also very active in a JEKO-1 cell line made resistant to PF-00477736. The synergistic effect of the combination was also observed using another Chk1 inhibitor (AZD-7762). Western Blot Analysis revealed that the combined treatment at concentrations of ibrutinib and PF-00477736 not toxic as single agents, neutralized the increase in phosphor-ERK observed after PF-00477736 treatment, and led to a substantial decrease in the active phosphorylated form of BTK in Y223. Cell cycle analysis and apoptosis are undergoing to try to dissect the cytotoxic mechanisms induced by the combination along with studies aiming at elucidating the molecular mechanisms at the basis of this combination. These data would suggest that ibrutinib in combination with Chk1 inhibitors could be a new and effective therapeutic strategy to test in clinical setting in MCL.

Citation Format: Valentina Restelli, Micaela Vagni, Monica Lupi, Francesco Bertoni, Giovanna Damia, Laura Carrassa. Combining ibrutinib with Chk1 inhibitors as a new therapeutic strategy for mantle cell lymphoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C193.
Abstract C194: Repression of tumor survival pathways by novel and selective inhibitors of MNK1 and MNK2 kinases in cancer
Authors: Rzymski Tomasz , Dreas Agnieszka , Wincza Ewelina , Fabritius Charles-Henry , Kulesza Urszula , Kucwaj- Brysz Katarzyna , Milik Mariusz , Gołas Aniela , Windak Renata , Żyłkiewicz Eliza , Wróbel Anna , Sułkowski Maciej , Brzózka Krzysztof
Published: May 2016

Herewith, we report development of small molecule inhibitors of MNK1 and MNK2 kinases and their cellular activity. MNK1 and 2 are MAP kinase-interacting kinases are activated by RAS and MAPK signaling pathways, and are involved in regulation of translation. Both kinases phosphorylate translation initiation factor eIF4e on a conserved serine 209. eIF4E can contribute to the oncogenic transformation both in vitro and in vivo and is highly expressed in diverse types of cancer. Interestingly, mice that lack both Mnk1 and Mnk2 do not have any apparent phenotype. Recently first dual MNK1/MNK2 inhibitors have entered clinical trials as a combinational therapy with docetaxel in NSCLC.

SEL201 is a series of small molecule inhibitors which inhibit activity of both MNK1 and MNK2 in a low nM range and high selectivity confirmed in kinome panels. Analysis of SEL201 cellular activity indicated potent inhibition of eIF4e Ser209 in vitro in cancer cells and in vivo after oral administration in xenograft tumors. Repressed phosphorylation of eIF4e resulted in impaired translation of several proteins involved in metastasis and activation of immune cells. High potency, selectivity and favorable ADME/PK profile indicates that SEL201 inhibitors would be useful tools in probing molecular consequences of eIF4e Ser209 inhibition in cancer cells. SEL201 in vitro and in vivo activities on viability and metastasis will be presented in cellular and in vivo models of solid tumors and hematological malignancies. SEL201 series is further developed as a cancer therapy with a good therapeutic window.

Citation Format: Tomasz Rzymski, Agnieszka Dreas, Ewelina Wincza, Charles-Henry Fabritius, Urszula Kulesza, Katarzyna Kucwaj- Brysz, Mariusz Milik, Aniela Gołas, Renata Windak, Eliza Żyłkiewicz, Anna Wróbel, Maciej Sułkowski, Krzysztof Brzózka. Repression of tumor survival pathways by novel and selective inhibitors of MNK1 and MNK2 kinases in cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C194.