bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract 798: Androgen receptor, PI3K/mTOR and PSMA: Exploring and exploiting the interplay between therapeutic targets in prostate cancer
Authors: Murga Jose D. , Magargal Wells W. , Moorji Sameer M. , DiPippo Vincent A. , Olson William C.
Published: May 2015

Introduction: Androgen receptor (AR), the PI3K/mTOR signaling pathway and prostate-specific membrane antigen (PSMA) represent significant potential targets for prostate cancer therapy. The present study examined the cross-regulation and co-targeting of these molecular pathways.

Methods: Cytotoxicity and the kinetics of antigen expression were evaluated in prostate cancer cell lines (LNCaP and C4-2) that vary according to androgen dependence. Expression of PSMA, prostate-specific antigen (PSA), and AR was evaluated in cells cultured in rapamycin and AR inhibitors. Cells were tested for susceptibility to PI3K/mTOR inhibitors used alone and in combination with PSMA ADC, a fully human PSMA monoclonal antibody conjugated to the microtubule disrupting agent monomethyl auristatin E (MMAE). Potential drug synergy or antagonism was evaluated using the Bliss independence method.

Results: In androgen-dependent LNCaP cells, rapamycin exerted antiproliferative effects that were accompanied by an increase in AR expression and signaling in the absence of any significant effect on PSMA expression. In androgen-independent C4-2 cells, rapamycin increased AR expression/signaling and PSMA expression in the absence of any significant anti-proliferative effect. AR inhibitors synergized with PSMA ADC in LNCaP and C4-2 cells, but PI3K/mTOR pathway inhibitors synergized with PSMA ADC in C4-2 cells only. More modest synergy was observed by combining non-targeted microtubule inhibitors with inhibitors of AR or mTOR. Compared with rapamycin, GDC0941 (PI3K inhibitor) and MK-2206 (Akt inhibitor), both upstream of mTOR, synergized less strongly with PSMA ADC in C4-2 cells.

Conclusions: In this study, AR and PI3K/mTOR pathways exhibited cross-regulation impacting PSMA expression. PSMA ADC synergized with AR and mTOR inhibitors via a multimodal mechanism involving increased PSMA expression and disruption of microtubule function. The findings support clinical exploration of regimens combining PSMA-targeted therapies with inhibitors of the AR and/or PI3K/mTOR signaling pathways.

Citation Format: Jose D. Murga, Wells W. Magargal, Sameer M. Moorji, Vincent A. DiPippo, William C. Olson. Androgen receptor, PI3K/mTOR and PSMA: Exploring and exploiting the interplay between therapeutic targets in prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 798. doi:10.1158/1538-7445.AM2014-798
Abstract 80: Activated SHP2 collaborates with MYCN in neuroblastoma tumorigenesis
Authors: Zhang Xiaoling , Yang Guang , Look A.Thomas , Neel Benjamin G. , Zhu Shizhen (Jane)
Published: May 2015

Neuroblastoma, an embryonic tumor of peripheral sympathetic nervous system (PSNS), accounts for 10% of all childhood cancer deaths. We recently developed a robust zebrafish model of neuroblastoma and demonstrated that activated ALK synergizes with MYCN by inhibiting a developmentally-timed apoptotic response that is otherwise induced by MYCN. Genomic studies show that PTPN11 (encoding SHP2) is the second most frequently mutated genes in high-risk neuroblastoma. We have now used our zebrafish model to ask whether mutationally activated SHP2 functions as an oncogene in neuroblastoma. We developed a transgenic line in which ptpn11E69K is overexpressed in the PSNS under control of the dopamine-beta-hydroxylase promoter. Interestingly, ptpn11E69K synergized with MYCN to accelerate the onset of neuroblastoma in the interrenal gland (IRG), the zebrafish analogue of the adrenal medulla. Tumors began to appear at 15 weeks in transgenic fish overexpressing MYCN alone, whereas latency was shortened to 7 weeks and the penetrance was increased more than four-fold in transgenic fish coexpressing MYCN and ptpn11E69K. Coexpression of ptpn11E69K and MYCN also induced ganglioneuroma in the sympathetic ganglia, an outcome that has not been observed in transgenic fish overexpressing MYCN and activated ALK. In addition, coexpression of ptpn11E69K and MYCN induced adrenal neuroblastic hyperplasia in the IRG of all the transgenic fish at 5 weeks of age, a phenotype that has only been observed in about 50% of transgenic fish overexpressing activated ALK and MYCN or MYCN alone. Thus, these results suggest that activated SHP2 can collaborate with MYCN in neuroblastoma tumorigenesis via mechanisms different from those of activated ALK. Thus, zebrafish appears to provide a robust model system for functional genomic analysis and for the investigation of the mechanisms and pathways underlying genetic alterations identified in integrative genomic studies.

Citation Format: Xiaoling Zhang, Guang Yang, A.Thomas Look, Benjamin G. Neel, Shizhen (Jane) Zhu. Activated SHP2 collaborates with MYCN in neuroblastoma tumorigenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 80. doi:10.1158/1538-7445.AM2014-80
Abstract 800: Synergistic effects of CBL0137 and gemcitabine against non-small cell lung and pancreatic cancer xenografts
Authors: Burkhart Catherine , Kohrn Rachael , Walker Brittany , Meyer David , Gurova Katerina , Gudkov Andrei
Published: May 2015

CBL0137 represents a novel class of small molecules that simultaneously activate p53 and inhibit cancer-associated stress response pathways, such as NF-κB and HSF-1. The effects of CBL0137, culminating in tumor cell death, are mediated by the inhibition of FACT, a chromatin remodelling factor complex composed of SSRP1 and SPT16 subunits, that is involved in the transcription of genes with highly ordered chromatin structure, replication, and mitosis. FACT is expressed during early embryogenesis and in undifferentiated progenitors and stem cells of adult tissues while protein levels of both FACT subunits are almost undetectable in differentiated cells and tissues. FACT is expressed in several tumor types compared to equivalent normal tissues. In particular, SSRP1 is expressed in a high proportion of lung and pancreatic cancers (∼45-63%). FACT positive tumors are associated with an aggressive malignant phenotype (high grade, metastatic disease, worse overall survival). Therefore, FACT represents a potentially important target for cancer therapy. We investigated the effect of CBL0137 and its combination with gemcitabine a nucleoside analog used in treatment of non-small lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDA). We found that CBL0137 had significant antitumor activity against a H1975 NSCLC xenograft model (89.6% growth inhibition) as well as a patient-derived PDA (PDA#2) model (70.4% growth inhibition). Furthermore, CBL0137 acted synergistically with gemcitabine against both tumor types as evidenced by increased median survival time compared to each drug administered as a single agent (increase in survival time: H1975- >47 days combination vs 24 days CBL0137 only, 32.5 days gemcitabine only; PDA#2- >42 days combination vs 28 days CBL0137 only, 30.5 days gemcitabine only). Preliminary investigation into the mechanism underlying the synergy of this combination suggest that CBL0137 may enhance gemcitabine activity in part by abrogating the expression of modulators of gemcitabine response, such as cytidine deaminase and ribonucleotide reductase. Together, these data indicate that CBL0137 may provide a clinical benefit for the treatment of both NSCLC and PDA when combined with standard agent gemcitabine.

Citation Format: Catherine Burkhart, Rachael Kohrn, Brittany Walker, David Meyer, Katerina Gurova, Andrei Gudkov. Synergistic effects of CBL0137 and gemcitabine against non-small cell lung and pancreatic cancer xenografts. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 800. doi:10.1158/1538-7445.AM2014-800
Abstract 810: O6 methylguanine DNA methyltransferase inhibition sensitizes pancreatic cancer cells to temozolomide
Authors: Bobustuc George C. , Ticku Jonathan , Patel Anand , Srivenugopal Kalkunte S. , Konduri Santhi D.
Published: May 2015

O6 methylguanine DNA methyltransferease (MGMT) is overexpressed in majority of cancers including pancreatic cancer. MGMT has been the focus of significant research for its role in the repair of DNA damage caused by alkylating agents. In the present study, we tested the administration of the MGMT inhibitor O6-benzylguanine (BG) at non-toxic doses in combination with an alkylator TMZ (temozolomide) on pancreatic cancer cells (L3.6 pl and PANC1) in cell culture and xenograft model. Here, we report that TMZ decreases pancreatic cancer cell growth in a dose dependent manner. BG further sensitizes pancreatic cancer cells to TMZ and significantly inhibits pancreatic cancer growth. We also report that BG, either alone or in combination with TMZ, inhibits the expression of MGMT, Ki-67 and BIRC5 (survivin), which are involved in pancreatic tumorigenesis and cell division, and induces the expression of p21cip1 cell cycle inhibitor. Microarray analysis revealed that BG significantly decreased the transcription of a group of proto-oncogenes, growth factors, cell cycle and overall transcription regulators involved in tumorigenesis like ARHGDIB, IGFL1, KIF20A, CA9, MMP10 and E2F2 and increased the transcription of a variety of genes involved in tissue differentiation, cell cycle regulation and invasion inhibitors like GDF15, CDKN1A and TIMP1. In our pancreatic cancer xenograft model, BG +/- TMZ significantly inhibited pancreatic tumor growth in vivo compared to single agent TMZ or controls. Further, BG promotes p53 function leading to growth inhibition, in part substantiating the underlying mechanism of BIRC5 (survivin) inhibition and p21cip1 induction. In conclusion, our findings suggest that MGMT inhibition may potentially provide a novel therapeutic approach in pancreatic cancer by opening the option of using (oral) alkylators like TMZ.

Citation Format: George C. Bobustuc, Jonathan Ticku, Anand Patel, Kalkunte S. Srivenugopal, Santhi D. Konduri. O6 methylguanine DNA methyltransferase inhibition sensitizes pancreatic cancer cells to temozolomide. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 810. doi:10.1158/1538-7445.AM2014-810
Abstract 814: Novel aspirin based selenium compounds as therapy against pancreatic cancer
Authors: Karelia Deepkamal N. , Pandey Manoj K. , Plano Daniel , Amin Shantu , Sharma Arun K.
Published: May 2015

Inflammation plays an important role in tumor growth promotion and has been linked to several human cancers. Evidences have demonstrated that inflammation has a high correlation with pancreatic cancer (PC) growth and promotion. An important mediator of inflammatory process is Cyclooxygenase 2 (COX-2) protein, which has been shown to be over-expressed in PC. Another major pathway which is crucial for inflammatory responses, cell proliferation, and resistance to apoptosis is the nuclear factor κB (NF-κB) pathway. It has been demonstrated that NF-κB pathway is responsible for drug resistance in PC. Aspirin, a well-known non-steroidal anti-inflammatory drug (NSAID), has been shown to have anti-cancer effects against PC. The mechanism of action of aspirin against PC is partially dependent on COX inhibition, as well as COX independent mechanism. Through extensive structure-activity relationship studies on Se-NSAID compounds, we have recently identified two Se-Aspirin compounds, ASD-43 and ASD-49, designed by incorporating selenium (Se) into salicylic acid structure, rendering it lethal to cancer cells. Previously, we had reported that Se-aspirin hybrid compounds were effective in different cancers, including PC. In this study we sought to evaluate the mechanism of action of these compounds in inhibiting the growth of PC. Since aspirin induces its effect partially by inhibiting COX, we hypothesized that these agents (ASD-43 and ASD-49) showed their anti-cancer activity by potently inhibiting COX activity as well as by modulating the inflammatory NF-κB pathway. Our studies, in Panc-1 cells, have shown that both ASD-43 and ASD-49 inhibited the degradation of IκB-alpha, which inhibits NF-κB from going into the nucleus, in presence of tumor necrosis factor (TNF). Upon treatment with ASD-43 and ASD-49, NF-κB regulated proteins like survivin and Bcl-xL expression was down regulated. Furthermore, a dose dependent induction of apoptosis in these cells was detected by activation of caspase-3 and PARP cleavage. Taken together, these results suggest that both ASD-43 and ASD-49 may represent potentially promising therapeutic agents for PC that induce apoptosis via the inhibition of COX and NF-κB pathways. Detailed investigations regarding the efficacy and mechanism of action of these compounds will be presented.

Citation Format: Deepkamal N. Karelia, Manoj K. Pandey, Daniel Plano, Shantu Amin, Arun K. Sharma. Novel aspirin based selenium compounds as therapy against pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 814. doi:10.1158/1538-7445.AM2014-814
Abstract 815: CBL0137 demonstrates significant antitumor activity against hepatocellular carcinoma alone and in combination with sorafenib
Authors: Burkhart Catherine , Kohrn Rachael , Walker Brittany , Gurova Katerina , Purmal Andrei , Gudkov Andrei
Published: May 2015

Primary hepatocellular carcinoma (HCC) is the 6th most common malignancy diagnosed worldwide with an incidence that continues to rise. Even with the use of the current standard of care drug sorafenib, survival of patients remains at ∼10-11 months and sorafenib toxicity results in dose interruptions and delays. Therefore, tolerable, effective therapies against HCC are greatly needed. CBL0137 represents a novel class of small molecules that simultaneously activate p53 and inhibit cancer-associated stress response pathways, such as NF-κB and HSF-1, and has demonstrated broad range antitumor activity against pre-clinical tumor models. The effects of CBL0137 are mediated by the inhibition of the chromatin remodelling factor FACT (FAcilitates Chromatin Transcription) comprised of SSRP1 and SPT16 subunits. FACT is expressed in undifferentiated progenitors and stem cells of adult tissues, but is almost undetectable in differentiated cells. It is expressed in many tumor types, including HCC, and is correlated with high grade and worse overall survival. Thus, FACT represents a potentially important target for cancer therapy. We investigated the effect of CBL0137 on HCC using HepG2 and Hep3B xenograft models. Treatment of tumor bearing mice intravenously with 60-70 mg/kg CBL0137 every 4th day resulted in ∼88-94% tumor growth inhibition in both models, including tumor regression in 60-80% of tumors during the course of treatment. Furthermore, combination of suboptimal doses of CBL0137 with sorafenib had greater efficacy compared to either drug alone (tumor growth inhibition: HepG2- 87.9% combination vs 73.6% CBL0137 only (P=0.0014), 75.7% sorafenib only (P=0.0006); Hep3B- 79.6% combination vs 38.2% CBL0137 only (P=0.003), 51.4% sorafenib only (P=0.032)). Although the mechanism resulting in the combination effect is unknown, in vitro analysis of markers of CBL0137 and sorafenib activity revealed that both drugs caused a marked decrease in the basal and induced expression of NF-κB target genes (IL-8 and TNF). Furthermore, the combination of CBL0137 and sorafenib almost completely abolished the expression of these genes in both HCC cell lines, suggesting that the combination effect may be in part mediated through inhibition of the NF-κB pathway. Together, these data indicate that CBL0137 may provide a clinical benefit for the treatment of HCC both alone and in combination with sorafenib.

Citation Format: Catherine Burkhart, Rachael Kohrn, Brittany Walker, Katerina Gurova, Andrei Purmal, Andrei Gudkov. CBL0137 demonstrates significant antitumor activity against hepatocellular carcinoma alone and in combination with sorafenib. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 815. doi:10.1158/1538-7445.AM2014-815
Abstract 817: Sepantronium is a DNA damaging agent that potentiates PLK1 inhibitor volasertib
Authors: Hong Mei , Ren Mingqiang , Silva Jeane , Hao Zhonglin
Published: May 2015

In a search for novel agents that boost the anti-neoplastic effects of polo-like kinase 1(PLK1) inhibitor volasertib, we found that a sepantronium and volasertib combination at the nano mole concentration potently inhibited growth of various non-small cell lung cancer (NSCLC) cell lines than either drug alone in vitro. Combination use of volasertib with sepantronium inhibited adaptation of cells to polo arrest. Addition of sepantronium to volasertib prevented accumulation of survivin and cyclin B protein at a concentration causing no appreciable survivin down regulation. Sepantronium, was originally developed as a survivin inhibitor. However, sepantronium induced cell cycle arrest from G1 or G2/M phase. Further studies demonstrated DNA damage of cancer cells when they are treated with sepantronium, which is evidenced by induction of phospho-gammaH2AX. In line with induction of a DNA damage response in cancer cells, known DNA damage response sensors and transducers ATM, ATR, CHK1, CHK2, p53 are phosphorylated following drug treatment. Meanwhile, expression of CDKN1A, BAX and XRCC5 are induced at the mRNA level as determined by quantitative real time PCR. A single cell electrophoresis assay (Comet assay) of cells treated with sepantronium revealed severe DNA strand breaks. M-phase arrest does not increase the lethality of DNA damage by sepantronium as compared to G1 phase arrest. Knock down of survivin did not cause DNA damage. Hence, sepantronium is a DNA damaging agent that synergizes with volasertib and down- regulation of survivin is likely the consequence of DNA damage induced by sepantronium.

Citation Format: Mei Hong, Mingqiang Ren, Jeane Silva, Zhonglin Hao. Sepantronium is a DNA damaging agent that potentiates PLK1 inhibitor volasertib. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 817. doi:10.1158/1538-7445.AM2014-817
Abstract 819: A novel small molecule cytidine analog, RX-3117, shows potent efficacy in xenograft models, even in tumors that are resistant to treatment with gemcitabine
Authors: Yang Mi Young , Lee Young Bok , Kim Deog Joong , Ahn Chang-Ho , Kaye Joel , Fine Tania , Kashi Rina , Ohne Osnat
Published: May 2015

RX-3117 (fluorocyclopentenylcytosine) is a novel small-molecule chemotherapeutic agent that belongs to the class of cytotoxic antimetabolite cytidine analogs. Cytidine analogs, including gemcitabine, have been widely used for the treatment of various types of cancer, both hematologic as well as solid. However, despite the success of gemcitabine, there is no oral formulation of gemcitabine and drug resistance is common. Thus, RX-3117 was synthesized as a oral formulation to overcome gemcitabine resistance with a better pharmacologic profile. In this study, the efficacy of RX-3117 was examined in 12 different human tumor (colon, non-small cell lung, small cell lung, pancreatic, renal, ovarian and cervical) xenograft models, grown subcutaneously in athymic nude mice. Not only has RX-3117 demonstrated potent efficacy in several cancer xenograft models but also oral treatment with RX-3117 results in dose-dependent tumor growth inhibition (TGI), even in tumors that are only moderately sensitive or resistant to gemcitabine. In the Colo-205, H460, H69 and CaSki models, gemcitabine treatment resulted in 28%, 14%, 25%, and 0% TGI, respectively, whereas oral treatment with RX-3117 induced 93%, 91%, 62%, and 66% TGI, respectively. This indicates that RX-3117 may have the potential to be used for the treatment of tumors that do not respond to gemcitabine. In order to extend the results established in cell line xenograft models, and to test efficacy in a potentially more clinically relevant system, RX-3117 was evaluated in a single primary low passage human pancreatic Tumorgraft™CTG-0298, which is resistant to gemcitabine and has a favorable RX-3117 activating enzyme profile. Treatment with RX-3117 resulted in dose dependent TGI and was superior to the standard of care agent gemcitabine. This study successfully demonstrated preliminary efficacy and therapeutic potential of RX-3117.

Citation Format: Mi Young Yang, Young Bok Lee, Deog Joong Kim, Chang-Ho Ahn, Joel Kaye, Tania Fine, Rina Kashi, Osnat Ohne. A novel small molecule cytidine analog, RX-3117, shows potent efficacy in xenograft models, even in tumors that are resistant to treatment with gemcitabine. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 819. doi:10.1158/1538-7445.AM2014-819
Abstract 821: Fusogenic liposomes: A novel therapeutic strategy to efficiently target and destroy prostate cancer
Authors: Mriouah Jihane , Nesbitt Rae-Lynn , Pink Desmond , Duncan Roy , Zijlstra Andries , Lewis John D.
Published: May 2015

Prostate cancer is the most common malignancy in North American men. While patients have benefited from advances in androgen deprivation therapy, prostate cancer ultimately evolves to a metastatic or castrate-resistant state that makes it the second-leading cause of cancer mortality in males. In the past 3 years, new chemotherapeutic drugs with efficacy in advanced disease have been introduced. Yet their efficacy is limited by dose-limiting toxicities and side effects due primarily to suboptimal biodistribution - they do not target tumors directly. To overcome these limitations, we have developed a novel drug encapsulation system for efficient and specific delivery of chemotherapeutic agents to prostate tumors. The reptilian reovirus-derived fusion-associated small transmembrane (FAST) protein (p14) increases the fusion of liposomes to cell membranes. In this study, we combine these fusogenic liposomes with peptides targeted to gastrin-releasing peptide receptors (GRPR) to improve the delivery of chemotherapeutic payloads specifically to prostate cancer cells while sparing normal tissue.

A fusion protein containing p14 and a C-terminal bombesin peptide was produced in a baculovirus expression system and incorporated into liposomes. The targeting and fusogenic properties of the p14-bombesin protein-containing liposomes were confirmed using flow cytometry. These experiments demonstrated improved delivery to cancer cells in vitro (PC3, LNCaP), compared to non-tumoral cells (BPH). The specificity of targeted fusogenic liposomes was confirmed by knockdown of GRPR and by blocking with free bombesin peptides. We then used intravital imaging in an avian xenograft model to measure the accumulation and specific uptake of the fusogenic targeted liposomes in prostate tumors compared to benign (BPH) and normal tissue, and found a significant increase in uptake in GRPR-expressing prostate cancer tumors using the bombesin-targeted fusogenic liposomes compared to controls. As a further proof of principle, we modified a commercial formulation of Doxil to incorporate our p14-bombesin fusion protein. This formulation showed significantly enhanced cancer-specific cytotoxicity in vitro and increased efficacy in xenograft models.

Taken together, these studies demonstrate that molecular-targeted fusogenic FAST liposomes are a promising platform for improving the efficacy of chemotherapies that should show enhanced activity in advanced and metastatic prostate cancers.

Citation Format: Jihane Mriouah, Rae-Lynn Nesbitt, Desmond Pink, Roy Duncan, Andries Zijlstra, John D. Lewis. Fusogenic liposomes: A novel therapeutic strategy to efficiently target and destroy prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 821. doi:10.1158/1538-7445.AM2014-821
Abstract 830: Disulfiram is a potent inhibitor of topoisomerase II
Authors: Wu Xing , Yalowich Jack C. , Patel Daywin , Hasinoff Brian B.
Published: May 2015

Disulfiram is used in the treatment of alcoholism. It has also shown promise as an anticancer drug. The disulfide bond in disulfiram is metabolized in vivo to diethyldithiocarbamate (DDTC) which forms an extremely strong complex with copper(II) through which it may exert its cytotoxicity. Both disulfiram and diethyldithiocarbamate inhibited K562 cell growth in the low nanomolar range. The addition of the copper(II) chelators Trien and ammonium tetrathiomolybdate to the cell culture medium significantly reduced the cytotoxicity of disulfiram and diethyldithiocarbamate towards K562 cells, which suggests that their cytotoxicity is mediated by uptake of trace amounts of copper from the culture medium. Disulfiram, but not DDTC, strongly inhibited the decatenation activity of topoisomerase IIα in the low micromolar concentration range. Disulfiram, but not DDTC, also was shown to be a topoisomerase IIα poison as evidenced by its ability to induce formation of linear DNA. However, the K/VP.5 cell line, a K562-derived etoposide-resistant cell line with reduced levels of topoisomerase II, was not cross-resistant to either disulfiram or DDTC. K562 cells depleted in GSH levels by treatment with buthionine sulfoximine did not show increased sensitivity to disulfiram or DDTC. Disulfiram and DDTC also did not increase dichlorofluorescein fluorescence in K562 cells. These latter two results suggest that copper-mediated oxidative stress may not be a significant factor in their cytotoxicity. In summary, these results showed that while disulfiram and DDTC inhibited topoisomerase IIα, this inhibition may be only partly responsible for their cytotoxicity. Support: CIHR, a Canada Research Chair in Drug Development to B.B.H., and a National Institutes of Health grant CA090787 to J.C.Y.

Citation Format: Xing Wu, Jack C. Yalowich, Daywin Patel, Brian B. Hasinoff. Disulfiram is a potent inhibitor of topoisomerase II. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 830. doi:10.1158/1538-7445.AM2014-830
Abstract 834: The microtubule-disrupting drug BNC105 is a potent inducer of acute apoptosis in CLL
Authors: Bates Darcy J.P. , Feris Edmundo J. , Danilov Alexey V. , Eastman Alan
Published: May 2015

The cytotoxicity of microtubule-disrupting drugs such as the vinca alkaloids has generally been considered to occur during mitosis. However, we have reported that vinca alkaloids can induce apoptosis rapidly (<6 h) from all phases of the cell cycle, and even in post-mitotic quiescent cells such as peripheral chronic lymphocytic leukemia (CLL). Microtubule disruption still appears to be required as acute apoptosis also occurs with combretastatin A4 (CA4) which targets the colchicine-binding site on tubulin, but not with paclitaxel which stabilizes microtubules. The mechanism of this rapid apoptosis is associated with two different pathways: induction of the pro-apoptotic BCL2 family member NOXA and activation of c-Jun N-terminal kinase (JNK). A proof-of-concept clinical trial revealed that vincristine activated JNK in peripheral lymphocytes of patients with CLL, but failed to induce NOXA or apoptosis, suggesting that this might not be the best microtubule disruptor to use clinically. Further investigation revealed that the vascular disrupting agent BNC105 (provided by Bionomics Ltd), which also targets the colchicine-binding site on tubulin, is a much more potent activator of JNK and inducer of NOXA in various leukemia cell lines and freshly isolated CLL cells. BNC105 induced ATF3, phospho-ATF2 and NOXA proteins and activated JNK at low nM concentrations. As a single agent, BNC105 induced JNK-dependent apoptosis in CLL cells ex vivo at clinically achievable concentrations, and much more potently than either vinblastine or CA4. The combination of BNC105 with the BCL2 inhibitor

ABT-199 increased apoptosis levels in CLL cells and various leukemia cell lines. Furthermore, the addition of BNC105 partially overcame stroma-mediated resistance to ABT-199 in CLL cells suggesting potential efficacy of this combination in the lymph node microenvironment. Survival of normal lymphocytes was not affected by BNC alone or in combination, even though JNK was activated. These results suggest BNC105 is an excellent candidate for clinical trials to induce acute apoptosis in hematopoietic malignancies.

Citation Format: Darcy J.P. Bates, Edmundo J. Feris, Alexey V. Danilov, Alan Eastman. The microtubule-disrupting drug BNC105 is a potent inducer of acute apoptosis in CLL. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 834. doi:10.1158/1538-7445.AM2014-834
Abstract 836: Potent antitubulin and antitumor activities influenced by the 3-D conformational shape of bicyclic fused pyrimidines
Authors: Gangjee Aleem , Xiang Weiguo , Mooberry Susan L. , Hamel Ernest
Published: May 2015

Compounds that bind to the tubulin colchicine site cause microtubule depolymerization, inhibit the polymerization of purified tubulin and cause cancer cells to accumulate in mitosis. Some colchicine-site agents additionally have the ability to overcome multiple drug resistance mechanisms, including those mediated by the expression of P-glycoprotein (Pgp) or expression of the β-III isotype of tubulin. We have reported a series of aniline substituted pyrimidines and fused bicyclic and tricyclic pyrimidine compounds that bind to the colchicine site. These compounds are single to triple digit nanomolar inhibitors of cancer cell proliferation. We hypothesized that the conformational orientation of the 4-aniline and the fused pyrimidine scaffold plays an important role in the biological activity of these compounds. In this study, we utilized NMR (NOESY) and molecular modeling to compare the lowest energy conformation of different 4-substituted 2-methyl cyclopenta[d]pyrimidines and their microtubule depolymerizing, colchicine site binding and antiproliferative activities. Among the 4-position substituents were N-methyl-4’-methoxynaphthyl-1’-amino (1), N-methyl-6’-methoxynaphthyl-1’-amino (2) and N-methyl-5’-methoxy-2’-amino (3). The IC50 values towards the MDA-MB-435 tumor cell line were 250 nM for 1 and 10 nM for 3. NMR (NOESY) demonstrated that compound 2 lost the free rotation of the naphthyl ring attached to the cyclopenta[d]pyrimidine ring due to 5-H steric hindrance and did not cause microtubule depolymerization. Compounds 1 and 3 retain the ability to rotate the naphthyl ring even though they adopt slightly different stable conformers. The stable conformational differences of these three compounds afford different binding poses in docking to the colchicine site on tubulin (PDB: 1SA0, MOE 2012), which explains the significant differences in antiproliferative activity, microtubule depolymerizing and inhibition of colchicine binding. This study affords a lead compound that defines a 104o (orthogonal) orientation of the naphthyl ring to the cyclopenta[d]pyrimidine scaffold for the best biological activities.

Citation Format: Aleem Gangjee, Weiguo Xiang, Susan L. Mooberry, Ernest Hamel. Potent antitubulin and antitumor activities influenced by the 3-D conformational shape of bicyclic fused pyrimidines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 836. doi:10.1158/1538-7445.AM2014-836
Abstract 838: Establishment, identification and treatment data of TCGA glioblatoma xenograft subtypes
Authors: Keir Stephen T. , Rasheed B Ahmed , Hoadley Katherine A. , Roskoski Martin A. , Gasinski Danuta , Killela Patrick J. , Yan Hai , Kwatra Madan M. , Friedman Henry S. , Bigner Darell D.
Published: May 2015

The Cancer Genome Atlas (TCGA) Network recently catalogued recurrent genomic abnormalities in glioblastoma (GBM). This genomic profiling lead to the molecular classification of GBMs into four subtypes: Proneural, Neural, Classical and Mesenchymal. The importance of identifying these subtypes helps researchers and clinicians to better understand GBMs with the potential to personalize treatment options and explore different therapeutic approaches that each subtype may require. In addition, the TCGA identified possible mechanisms that can cause some GBM tumors to become resistant to therapy, including the standard of care alkylating agent temozolomide (TMZ).

For this project, we established xenografts using patient derived tissue and passaged these xenografts until reliable growth characteristics were obtained. Established GBM xenografts were classified into TCGA-defined subtypes first by obtaining global gene expression data using the GeneChip Human Genome U133A 2.0 array from Affymetrix. Microarray data was then quantile normalized and probes were summarized as gene expression levels using RMA. Then data was log2 transformed and genes median centered. Xenografts were subsequently classified into one of four previously defined subtypes as described using Classification to the Nearest Centroid (ClaNC) with the TCGA GBM data as the training dataset.

Using established xenografts from each subtype, a panel of standard of care treatment agents (including TMZ) was assessed by delay in tumor growth and by tumor regression. Statistical analysis was performed using a SAS statistical analysis program, the Wilcoxon rank order test for growth delay, and Fisher's exact test for tumor regression. Data regarding each xenografts BRAF, EGFR, EGFRvIII, IDH1, PIK3CA, PIK3R1, PTEN, RB1, TERT and TP53 status is reported within.

The identification of these valid xenograft models represents an important contribution toward the ability of studying GBM subtypes, in particular for modeling and predicting therapeutic response.

Citation Format: Stephen T. Keir, B Ahmed Rasheed, Katherine A. Hoadley, Martin A. Roskoski, Danuta Gasinski, Patrick J. Killela, Hai Yan, Madan M. Kwatra, Henry S. Friedman, Darell D. Bigner. Establishment, identification and treatment data of TCGA glioblatoma xenograft subtypes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 838. doi:10.1158/1538-7445.AM2014-838
Abstract 840: Enhancement of antitumor effect of platinum complexes by PXR antagonist
Authors: Kishimoto Shuichi , Bou Erika , Higashi Kaho , Suzuki Ryosuke , Fukushima Shoji
Published: May 2015

The goal of this study was to evaluate the enhancing ability of PXR antagonists for the antitumor effect of platinum complex. Cell lines used in this study were human hepatoma cell line HepG2, human ovarian cancer cell line 2008 and human colon cancer cell line HCT116. Changes in mRNA expression were assessed by real-time RT-PCR, and the ability of apoptosis induction was assessed as caspase-3 activity. Cytotoxicity of platinum complexes was assessed by SRB assay, and IC75 and IC90 values of them were determined. They did not induce apoptosis at IC75 but did it markedly at IC90. Previously, we reported that though apoptosis in HepG2 was induced by IC90 dose of CDDP, addition of a PXR agonist, rifampicin, from 24-hr before treatment and during treatment with CDDP was almost suppressed. Moreover, we found that apoptosis in 2008 and HCT116 induced by IC90 dose of CDDP or oxaliplatin was suppressed by rifampicin. That suggests a nuclear receptor PXR affects on the cytotoxicity of platinum complexes for cancer cells other than HepG2. Ketoconazole (KTZ) and phenethyl isothiocyanate (PEITC) were selected as PXR antagonists that were added with platinum complex. Both drugs at 30 μM induced cytostatic cell growth inhibition in HepG2, 2008 and HCT116 but did not affect on caspase-3 activity compared with control in those cells. When these PXR antagonists at 30 μM were added to cancer cell lines from 24-hr before treatment and during treatment with CDDP at IC75, caspase-3 activity was significantly increased compared with that in CDDP alone. Also, when cells were exposed to CDDP and a PXR antagonist without PXR antagonist pretreatment, caspase-3 activity was increased but the level was reduced compared with that in the combination with pretreatment. Similarly, oxaliplatin in combination with KTZ or PEITC markedly induced apoptosis in HCT116. In HepG2, KTZ reduced the level of MRP2 mRNA. That suggests that pretreatment with KTZ might increase the intracellular platinum content and enhance the cytotoxicity of platinum complex. We concluded that PXR antagonist can be an agent enhancing the antitumor activity of platinum complex, and one of the mechanism is to suppress the expression of the platinum efflux transporter.

Citation Format: Shuichi Kishimoto, Erika Bou, Kaho Higashi, Ryosuke Suzuki, Shoji Fukushima. Enhancement of antitumor effect of platinum complexes by PXR antagonist. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 840. doi:10.1158/1538-7445.AM2014-840
Abstract 842: DNA opilymerase β participates in the repair of DNA damage from topoisomerase II
Authors: Sun Yilun , Bertram Sule , Nitiss John L.
Published: May 2015

DNA topoisomerase II (Top2) is the target of several important anti-cancer agents, including doxorubicin and etoposide. Clinically active Top2 agents, termed Top2 poisons, act by blocking the enzyme reaction at a step where the protein is covalently bound to DNA. This leads to the accumulation of Top2/DNA complexes that act as DNA damaging agents that interfere with DNA metabolism and trigger cell death. The mechanisms leading to tumor specific killing by Top2 poisons remain poorly understood, and have been hypothesized to result in part from DNA repair defects that arise during tumorigenesis. If this hypothesis is correct, then targeting repair pathways important for topoisomerase mediated cell killing could be used to enhance the activity of Top2 poisons. Similar reasoning has led to extensive trials of agents such as PARP inhibitors, and other DNA repair inhibitors. The DNA repair pathways that have been examined for sensitization to Top2 poisons include homologous recombination, non-homologous end-joining, proteasome mediated degradation, and nucleolytic activities that may participate in the removal of protein/DNA adducts (such as Tdp1 and Tdp2). We have been studying the repair of damage from Top2 poisons, and have optimized a quantitative assay for Top2/DNA covalent complexes in cultured mammalian cells. This assay, termed the ICE assay, detects Top2 covalent complexes by DNA purification followed by antibody detection of protein adducts. Using this assay, we have demonstrated a role of the MRN complex in processing Top2/DNA adducts, using both MRN knockdowns and small molecule inhibitors of the Mre11 nuclease activities. We also confirmed the importance of proteolytic pathways in repairing Top2 damage. A surprising candidate protein for participation in repair of damage from Top2 poisons is DNA polymerase β (pol β), an “X” family polymerase critical for base excision repair. Recent results have implicated pol β in processing of protein/DNA adducts (1). We found that the pol β inhibitor pamoic acid (4-[(3-Carboxy-2-hydroxynaphthalen-1-yl)methyl]-3-hydroxynaphthalene-2-carboxylic acid) and etoposide led to a large increase in Top2/DNA covalent complexes compared to etoposide alone. We are currently validating these results using other pol β inhibitors and gene knockdown approaches. We speculate that the dRP lyase activity may play a role in processing DNA damage arising from Top2 poisons.

Literature cited:

1. Lawson, M.H., et al. (2011) Two Novel Determinants of Etoposide Resistance in Small Cell Lung Cancer. Cancer Res, 71, 4877-4887.

Citation Format: Yilun Sun, Sule Bertram, John L. Nitiss. DNA opilymerase β participates in the repair of DNA damage from topoisomerase II. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 842. doi:10.1158/1538-7445.AM2014-842
Abstract 848: Galectin-1 mediates radiation-related lymphopenia in non-small cell lung cancer and attenuates tumor radiation response
Authors: Kuo Peiwen , Bratman Scott , Shultz David , Eyben Rie von , Chan Cato , Wang Ziwei , Say Carmen , Gupta Aparna , Loo Bill W. , Giaccia Amato , Koong Albert , Diehn Maximilian , Le Quynh-Thu
Published: May 2015

Decreased circulating lymphocytes after tumor irradiation has been linked to worse outcomes in several cancers treated with fractionated radiotherapy. The mechanism underlying radiation (RT)-induced lymphopenia is not well understood. Here, we show that lymphopenia also occurs after stereotactic ablative radiotherapy for early stage non-small cell lung cancer, and that it is associated with reduced survival. We provide evidence that RT-induced secretion of Galectin-1 (Gal-1), a b-galactoside binding protein, can potentially explain for this phenomenon. Using matched Gal-1 wild type and null mice together with Lewis lung carcinoma cells stably knocked-down of Gal-1 or scramble control, we show that irradiation of Gal-1 expressing tumor increases Gal-1 secretion in the blood and that it is linked to decreased circulating T-lymphocytes. This was ablated by either genetic down regulation of Gal-1 in the tumor or inhibition of Gal-1 activity by TDG. Moreover, Gal-1 down regulation resulted in enhanced radiation sensitivity in vitro as well as less intratumoral T cell apoptosis and angiogenesis in vivo, resulting in marked tumor growth delay and reduced spontaneous lung metastases when combined with radiotherapy. Similar results were noted when Gal-1 function was inhibited with TDG in vivo. Together, our data identify Gal-1 as an important mediator of RT-related lymphopenia and its proangiogenic and T cell proapototic effect may explain for the poorer outcome associated with RT-related lymphopenia. Gal-1 is therefore a new potential therapeutic target to combine with radiotherapy.

Citation Format: Peiwen Kuo, Scott Bratman, David Shultz, Rie von Eyben, Cato Chan, Ziwei Wang, Carmen Say, Aparna Gupta, Bill W. Loo, Amato Giaccia, Albert Koong, Maximilian Diehn, Quynh-Thu Le. Galectin-1 mediates radiation-related lymphopenia in non-small cell lung cancer and attenuates tumor radiation response. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 848. doi:10.1158/1538-7445.AM2014-848
Abstract 849: Profiling signaling networks using reverse phase protein arrays: validating FOXM1 as a potential target to radiosensitize glioblastoma (GBM) stem cells
Authors: Maachani Uday Bhanu , Tandle Anita T. , Shankavaram Uma , Meushaw Tamalee , Tofilon Philip J. , Camphausen Kevin A.
Published: May 2015

Glioblastoma multiforme (GBM) continues to be the most frequently diagnosed and lethal primary brain tumor. Adjuvant chemo-radiotherapy remains the standard of care following surgical resection. In this study, using reverse phase protein arrays (RPPAs), we assessed the biological effects of radiation on signaling pathways to identify potential radiosensitizing molecular targets. We examined levels of 172 phosphorylated and non-phosphorylated proteins under conditions of Ionizing radiation (IR) in patient derived GBM stem cells and established U251, U87 GBM cell lines in vitro and in an in vivo orthotropic mouse model. We identified subsets of proteins with clearly concordant/discordant behavior between GBM cells in vitro and in vivo. In general, molecules involved in anti-apoptotic, cell-cycle, survival pathways, tumor metastasis and DNA repair were affected. Comparing in vivo and in vitro samples after IR, 9 proteins were commonly elevated; phospho(p)-STAT3, CDC2, CyclinB1, BAX, pEIF4BP1, pAKT, pRB, pMEK1, and FOXM1. Conversely, 4 other proteins were commonly decreased; pPRKCA, pPRKCD, pNDRG1 and pRPS6. Recent evidence of FOXM1 as a master regulator of metastasis and its important role in maintaining neural, progenitor, and GBM stem cells intrigued us to validate it as a radiosensitizing target. We show high expression of FOXM1 across different patient derived stem cells. When GBM stem cells (NSC11, GBAM1) were differentiated in serum, we observed a decrease in FOXM1 levels, attaining more differentiation markers. In both differentiated and un-differentiated GBM stem cells, treatment with IR resulted in an increase of FOXM1 expression. However, inhibition of FOXM1 was only seen to have an effect on un-differentiated GBM stem cells, and resulted in reduced cell viability, a significant reduction in clonogenicity, and anchorage-independent growth, along with enhanced radiosenstivity with IR. Importantly, the combination of IR with FOXM1 inhibition showed these same effects irrespective of serum-differentiation. These results clearly suggest, inhibition of FOXM1 leads to radiosensitization. Since GBM stem cells, which comprise a subpopulation of tumor cells, maybe responsible for therapeutic resistance, we show that FOXM1 inhibition stands as a potential cancer stem-cell specific chemo-radio therapeutic target for GBM.

Citation Format: Uday Bhanu Maachani, Anita T. Tandle, Uma Shankavaram, Tamalee Meushaw, Philip J. Tofilon, Kevin A. Camphausen. Profiling signaling networks using reverse phase protein arrays: validating FOXM1 as a potential target to radiosensitize glioblastoma (GBM) stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 849. doi:10.1158/1538-7445.AM2014-849