bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of High cis-Polybutadiene in Styrene Solution with Neodymium-Based Catalysts: Towards the Preparation of HIPS and ABS via In Situ Bulk Polymerization
Authors: Díaz de León Ramón , Soriano Corral Florentino , Enríquez-Medrano Francisco Javier , Bosques Ibarra Gabriela , de León Martínez Patricia , Hernández Gámez Francisco , López-González Héctor Ricardo , Ramos de Valle Luis Francisco
Published: November 2016

In a first step, 1,3-butadiene was selectively polymerized at 60°C in styrene as solvent using NdV3/DIBAH/EASC as the catalyst system. The catalyst system activation process, the addition order of monomers and catalyst components, and the molar ratios [Al]/[Nd] and [Cl]/[Nd] were studied. The catalyst system allowed the selective 1,3-butadiene polymerization, reaching conversions between 57.5 and 88.1% with low polystyrene contents in the order of 6.3 to 15.4%. Molecular weights ranging from 39,000 to 150,000 g/mol were obtained, while cis-1,4 content was found in the interval of 94.4 to 96.4%. On the other hand, the glass transition temperatures of synthesized materials were established in the range of −101.9 to −107.4°C, explained by the presence of polystyrene segments in the polybutadiene chains; in the same sense, the polybutadienes did not show the typical melting endotherm of high cis-polybutadienes. In a second step, the resulting styrene/high cis-1,4 polybutadiene solutions were used to synthesize ABS (adding a fraction of acrylonitrile monomer) and HIPS via in situ bulk polymerizations and the results were discussed in terms of morphological development, molecular parameters, dynamical mechanical behavior, and mechanical properties.
Abstract A02: Cyclin A2 and CDK2 as Novel Targets of Aspirin and Salicylic acid: a Potential Role in Cancer Prevention
Authors: Dachineni Rakesh , Ai Guoqiang , D Ramesh Kumar , Sadhu Satya , Tummala Hemachand , Gunaje Jayarama B.
Published: November 2016

Data emerging from the past 10 years have consolidated the rationale for investigating the use of aspirin as a chemopreventive agent; however, the mechanisms leading to its anti-cancer effects are still being elucidated. We hypothesized that aspirin's chemopreventive actions may involve cell cycle regulation through modulation of the levels or activity of cyclin A2/cyclin dependent kinase-2 (CDK2). In this study, HT-29 and other diverse panel of cancer cells were used to demonstrate that both aspirin and its primary metabolite, salicylic acid, decreased cyclin A2 (CCNA2) and CDK2 protein and mRNA levels. The down regulatory effect of either drugs on cyclin A2 levels was prevented by pretreatment with lactacystin, an inhibitor of proteasomes, suggesting the involvement of 26S proteasomes. In-vitro kinase assays showed that lysates from cells treated with salicylic acid had lower levels of CDK2 activity. Importantly, three independent experiments revealed that salicylic acid directly binds to CDK2. Firstly, inclusion of salicylic acid in naïve cell lysates, or in recombinant CDK2 preparations, increased the ability of the anti-CDK2 antibody to immunoprecipitate CDK2, suggesting that salicylic acid may directly bind and alter its conformation. Secondly, in 8-anilino-1-naphthalene-sulfonate (ANS)-CDK2 fluorescence assays, pre-incubation of CDK2 with salicylic acid, dose-dependently quenched the fluorescence due to ANS. Thirdly, computational analysis using molecular docking studies identified Asp145 and Lys33 as the potential sites of salicylic acid interactions with CDK2. These results demonstrate that aspirin and salicylic acid down-regulate cyclin A2/CDK2 proteins in multiple cancer cell lines, suggesting a novel target and mechanism of action in chemoprevention.

Citation Format: Rakesh Dachineni, Guoqiang Ai, Ramesh Kumar D, Satya Sadhu, Hemachand Tummala, Jayarama B. Gunaje. Cyclin A2 and CDK2 as Novel Targets of Aspirin and Salicylic acid: a Potential Role in Cancer Prevention. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A02.
Abstract A03: SCFCyclin F connects AKT signaling to the core cell cycle oscillator
Authors: Emanuele Michael J. , Choudhury Rajarshi , Kernan Jennifer , Mills Christine Allie , Lahiri Debojyoti , Burke Daniel J.
Published: November 2016

Cell proliferation is governed by the presence of growth factors, and in their absence normal cells cease to progress through the cell cycle. The waves of Cyclin Dependent Kinase (CDK) activity constituting the core of the cell cycle oscillator are driven by cyclin synthesis and its subsequent destruction by the Anaphase Promoting Complex/Cyclosome (APC), a multi-subunit E3 ubiquitin ligase that controls degradation of Cyclins A and B. How growth factor signaling is integrated into the core cell cycle machinery remains largely elusive. Modular Cullin RING ubiquitin ligases (CRLs) represent the largest E3 ligase family in humans, and control the destruction of hundreds of proteins involved in virtually all aspects of cellular physiology. Here we establish a bi-directional ubiquitylation circuit between the APC substrate receptor Cdh1, and Cyclin F, a substrate receptor for the SCF (Skp1-Cul1-F box) family of CRL E3 ubiquitin ligases. We demonstrate that Cdh1 is regulated by SCF(Cyclin F), and conversely, Cyclin F is regulated by APC(Cdh1). AKT modulates the circuit by phosphorylating Cyclin F, enhancing SCF(Cyclin F) ligase assembly, and thereby catalyzing Cdh1 degradation. Later in the cell cycle, CDK phosphorylates Cdh1, preventing its degradation by altering its localization, and allowing both proteins to accumulate. The mutually antagonistic relationship between Cdh1 and Cyclin F represents the first described direct, reciprocal ubiquitylation circuit. Further, phospho-dependent ligase assembly signifies a novel regulatory mechanism for SCF ligases. We propose that AKT is part of a positive feedback loop involved in cell cycle control. This discovery connects growth factor signaling to the core cell cycle machinery, and has potential implications in malignancies where AKT is activated.

Citation Format: Michael J. Emanuele, Rajarshi Choudhury, Jennifer Kernan, Christine Allie Mills, Debojyoti Lahiri, Daniel J. Burke. SCFCyclin F connects AKT signaling to the core cell cycle oscillator. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A03.
Abstract A07: The identification of combinations for the CDK4 and CDK6 inhibitor, abemaciclib
Authors: Xueqian Gong , Chio Li-Chun , Webster Yue , Lallena Maria Jose , Boehnke Karsten , Torres Raquel , Iversen Phil , Dios Alfonso De , Smith Ian , Reinhard Christoph , Peng Sheng-Bin , Dempsey Jack , Burke Teresa , Chen Shih-Hsun , Stewart Trent , Beckmann Richard , Wu Wenjuan , Buchanan Sean G.
Published: November 2016

We developed a combination screening protocol to look for synergistic interactions with abemaciclib, an inhibitor of cyclin dependent kinases 4 and 6 (CDK4 and CDK6). Abemaciclib (LY2835219), has shown cytostatic effects in some cell lines while inducing senescence and apoptosis in particularly sensitive cell lines. Abemaciclib, combined with various compounds, was screened across panels of genomically characterized tumor cells. These screens identified several synergistic interactions that improved the activity of abemaciclib in cancer cells lines that respond to abemaciclib monotherapy (e.g. mantle cell lymphoma, ER+ breast cancer) but additionally revealed certain combinations with synergy in Rb wild-type cancers that do not respond optimally to single agent abemaciclib treatment. Most interestingly, MEK inhibitors and LY3009120, a novel Raf dimer inhibitor that inhibits all three Raf isoforms (Cancer Cell 28:384-98) were found to potentiate the cytostatic effects of abemaciclib in these cell lines leading to apoptosis in vitro and tumor regression in vivo. Further analysis of the effects of combined inhibition of CDK4 and CDK6 and Raf isoforms on downstream signaling pathways provides mechanistic clues that may help explain the observed synergy.

Citation Format: Gong Xueqian, Li-Chun Chio, Yue Webster, Maria Jose Lallena, Karsten Boehnke, Raquel Torres, Phil Iversen, Alfonso De Dios, Ian Smith, Christoph Reinhard, Sheng-Bin Peng, Jack Dempsey, Teresa Burke, Shih-Hsun Chen, Trent Stewart, Richard Beckmann, Wenjuan Wu, Sean G. Buchanan. The identification of combinations for the CDK4 and CDK6 inhibitor, abemaciclib. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A07.
Abstract A15: Sin3B: a non-classical tumor suppressor
Authors: Bainor Anthony J. , Ueberheide Beatrix , David Gregory
Published: November 2016

Perturbations in cell cycle regulators elicit hyperproliferation and the inability of cells to exit the cell cycle, which are common occurrences in cancer. Recently, we have demonstrated that Sin3B, an essential component of the mammalian histone deacetylase repressor complex, is required for oncogene-induced senescence both in vitro and in vivo. Surprisingly, primary Sin3B-null cells are not readily transformed upon ectopic expression of oncogenic Ras. Thus, these observations indicate that loss of Sin3B uncouples the ability to undergo senescence from the sensitivity to transformation in primary cells. To better understand the relationship between Sin3B, senescence and transformation, we have generated novel immortalized cell lines genetically inactivated for Sin3B. Our results indicate that in these Sin3B-deleted cells, expression of oncogenic Ras promotes transformation and provides a proliferative advantage. Interestingly, we have demonstrated that the paired amphipathic helix 2 (PAH2) domain is crucial for the tumor suppressive nature of Sin3B. To elucidate the molecular bases for these effects, immunoprecipitation and mass-spectrometry was performed to identify the proteins associated with Sin3B and its loss-of-function mutants. We have now identified novel interactors of the Sin3B complex and defined crucial domains responsible for the complex's assembly. These observations suggest that Sin3B functions as a non-classical tumor suppressor which serves to limit the transformative potential of cancer cells. The restoration of Sin3B functionality and downstream pathways may prove useful in the design of targeted therapies to treat advanced disease.

Citation Format: Anthony J. Bainor, Beatrix Ueberheide, Gregory David. Sin3B: a non-classical tumor suppressor. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A15.
Abstract A17: Cell cycle control through DREAM and MMB complexes
Authors: Guiley Keelan , Rubin Seth M.
Published: November 2016

The loss of cell cycle control is the most recognized trait of cancer cells. The ability of cells to exit the cell cycle has recently been shown to be dependent upon a large multi-protein repressor complex called DREAM. This complex represses the expression of all cell cycle genes during reversible cell cycle exit. In cycling cells, DREAM is disassembled and some of DREAM associated proteins form a new complex to promote cell cycle gene expression. These proteins that can act together both as repressors and activators of cell cycle gene expression are called the MuvB core. The MuvB core interacts with B-Myb during S phase to promote late cell cycle gene expression. This activator complex is called MMB and its integrity is required for proper cell division. The purpose of this project is to determine how the MuvB core interacts with B-Myb, and if MuvB can be targeted by therapeutics to restore proper cell cycle control in cancer. We have structurally and functionally characterized the mechanism of DREAM assembly and regulation, however MMB regulation remains poorly understood. DREAM has been suggested as a therapeutic target in cancer cells that arrest in response to drug treatment to evade apoptosis. Disruption of DREAM could force evasive cancer cells back into the cell cycle and elicit a response to chemotherapeutic treatment. Until recently, a DREAM interface to target was unavailable. I solved the x-ray crystal structure of MuvB core protein LIN52 complexed with RB tumor suppressor protein p107 and functionally characterized how this interaction is regulated in DREAM assembly. This is a suitable DREAM interface to target given disruption of this interface drives cell cycle entry. I have found that LIN52 also interacts with B-Myb and have obtained crystals of this subcomplex that diffract to 2.4 Å resolution. Therefore, I hypothesize that the MuvB core protein LIN52 mediates interactions with various transcription factors throughout the cell cycle to drive gene specificity through cooperative binding. I will test this hypothesis with two aims: 1) solve the x-ray crystal structure of B-Myb complexed with the MuvB core and investigate the cooperative DNA binding of MuvB and B-Myb; 2) Disrupt LIN52 interactions to disassemble DREAM in drug resistant cancer cells. Completion of these aims will unveil the mechanism of B-Myb activation in cancer and determine if LIN52 is a viable cancer therapeutic target.

Citation Format: Keelan Guiley, Seth M. Rubin. Cell cycle control through DREAM and MMB complexes. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A17.
Abstract A27: Cell cycle control and drugs targeting the bioenergetics of cancer
Authors: Shorr Robert
Published: November 2016

Differences in responsiveness to chemotherapeutics among patients may be associated with multiple cell types that can be found in tumors and the circulation. Recurrent or refractory disease may result from natural selection of cells in response to therapy. To design new drugs and make better use of existing drugs differences between diseased and disease causing cells in response to a specific drug requires investigation. The Warburg Effect is characteristic of the majority of cancer cell types both in tumors and the circulation. Drugs that target the underlying biochemistry of essential bioenergetic processes unique to cancer have been shown to have activity against a broad scope of cell types and disease indications while maintaining a favorable safety profile. Recent studies have shown that CPI 613 may have concentration dependent differences in the nature of response, cell death or cell cycle arrest, when tested against H460, BXPC3 and SF539 cancer cells. Understanding the mechanisms of cell cycle arrest is an important factor in choosing other drugs to be used in combination to maximize patient benefit. Results evaluating drug effects on G2/M control proteins will be presented.

Note: This abstract was not presented at the conference.

Citation Format: Robert Shorr. Cell cycle control and drugs targeting the bioenergetics of cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A27.
Abstract A34: Estrogen induces RAD51C expression and localization to sites of DNA damage
Authors: Holz Marina K.
Published: November 2016

Homologous recombination (HR) is a conserved process that maintains genome stability and cell survival by repairing DNA double-strand breaks (DSBs). The RAD51-related family of proteins is involved in repair of DSBs, consequently, deregulation of RAD51 causes chromosomal rearrangements and stimulates tumorigenesis. RAD51C has been identified as a potential tumor suppressor and a breast and ovarian cancer susceptibility gene. Recent studies implicated estrogen as a DNA-damaging agent that causes DSBs. We found that in estrogen receptor (ER)α-positive breast cancer cells, estrogen transcriptionally regulates RAD51C expression in ERα-dependent mechanism. Moreover, estrogen induces RAD51C assembly into nuclear foci at DSBs, which is a precursor to RAD51 complex recruitment to the nucleus. These findings provide insight into the mechanism of genomic instability in ERα-positive breast cancer and suggest that individuals with mutations in RAD51C that are treated with estrogen would be more susceptible to accumulation of DNA damage, leading to cancer progression.

Citation Format: Marina K. Holz. Estrogen induces RAD51C expression and localization to sites of DNA damage. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr A34.
Abstract B01: pRb activates mitochondrial metabolism and promotes differentiation through the histone demethylase Kdm5a
Authors: Váraljai Renáta , Islam Abul B.M.M.K. , Dyson Nicholas J. , Benevolenskaya Elizaveta V.
Published: November 2016

While largely studied for its role in cell cycle progression, pRb tumor suppressor is also responsible for differentiation. Cells isolated from Rb knockout animals (Rb1-/-), when induced for differentiation, display defects in induction of differentiation markers. Previous studies in our laboratory identified a critical pRB-interacting protein, Kdm5a, which loss rescued the differentiation defect. Kdm5a is a histone demethylase that is specific to the chromatin modification characteristic of active chromatin, histone H3 lysine 4 trimethylation. We found that Kdm5a binds to many genes with function in the mitochondria. Analysis of Rb1-/- mouse embryonic fibroblasts (MEFs) revealed that the mitochondrial genes were down-regulated, but expression of these genes was rescued upon knockout of Kdm5a. Strikingly, overexpression of the factor required for mitochondrial biosynthesis Pgc-1α or the mitofusin protein Mfn2, was sufficient to rescue the differentiation defect in Rb1-/- MEFs. The rescue of differentiation by loss of Kdm5a or by activation of mitochondrial biogenesis revealed the mitochondrial activation as an essential step in restoring differentiation. Here we investigate which specific mitochondrial function is involved in the differentiation rescue, using metabolic flux analysis and gas chromatography tandem mass spectrometry. We present the evidence that Rb1-deficient MEFs have a decreased oxidative capacity compared to the wild type MEFs, while loss of Kdm5a results in a highly increased respiration and TCA cycle metabolites. Overexpression of Pgc-1α and Mfn2 increased oxidative capacity in parallel with the differentiation rescue. In contrast, knockdown of Mfn2 inhibited oxidation as well as differentiation. Similar experiments conducted in Pgc-1α-/- MEFs were consistent with the role for Pgc-1α in increasing oxidative capacity. The data on establishing the link between mitochondrial function and differentiation are important because they may have implications in developing restorative, differentiation-based therapies.

Citation Format: Renáta Váraljai, Abul B.M.M.K. Islam, Nicholas J. Dyson, Elizaveta V. Benevolenskaya. pRb activates mitochondrial metabolism and promotes differentiation through the histone demethylase Kdm5a. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B01.
Abstract B03: Physical and functional interactions between two tumor suppressors, BIN1 and RB1
Authors: Folk Watson P. , Kumari Alpana , Cassimere Erica , Johnson Joanna , Sakamuro Daitoku
Published: November 2016

The bridging integrator 1 (BIN1) protein was originally identified as a cellular adaptor protein that interacts with the transcription factor c-MYC and inhibits cell proliferation. However, BIN1 inhibits tumor cell growth by both a BIN1 MYC-binding domain (MBD)-dependent mechanism and an MBD-independent mechanism. Consistently, BIN1 promotes skeletal muscle differentiation in vitro where c-MYC is not detectable, suggesting that an undefined BIN1-interacting protein other than c-MYC determines BIN1-mediated growth arrest in an MYC-independent manner.

Here we show the functional interplay between BIN1 and the RB1 tumor suppressor for growth arrest. BIN1 interacts with RB1 in differentiated (i.e. growth-arrested) C2C12 skeletal myotube cells, whereas such interaction was largely reduced in undifferentiated (i.e. actively proliferating) C2C12 myoblast cells. Acting through the coiled-coil BAR domain, an essential effector region for BIN1-mediated growth suppression, BIN1 physically interacts with the C pocket domain of RB1 in vitro and in vivo. The RB1-BIN1 protein-protein interaction is functionally germane. First, adenovirus E1A viral oncoprotein, which is known to stimulate cell proliferation in rodent fibroblast model systems by interacting with RB1, disrupted the RB1-BIN1 interaction in vitro. Second, the cancer suppression mediated by overexpressed BIN1 was partly attenuated by the co-transfection of short-hairpin RNA against RB1. Third, an MBD-independent BIN1-associated transcriptional corepressor activity was attenuated when endogenous RB1 was silenced. Fourth, serum stimulation-dependent phosphorylation of the RB-C pocket domain at serine 807/811, critical phosphorylation sites for RB1 inactivation by cyclin-dependent kinases 4 and 6 (CDK4/6), was largely reduced in BIN1-proficient cells. Conversely, the effect of PD-0332991, a chemical inhibitor of CDK4/6, on the growth suppression of RB-proficient cancer cells was more profound in BIN1-deficient cancer cells. Collectively, these data suggest that BIN1 and RB1 physically interact with one another and cooperate to induce growth arrest during cellular differentiation and cancer suppression.

Citation Format: Watson P. Folk, Alpana Kumari, Erica Cassimere, Joanna Johnson, Daitoku Sakamuro. Physical and functional interactions between two tumor suppressors, BIN1 and RB1. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B03.
Abstract B14: Feedback regulation between atypical E2Fs and APC/CCdh1 coordinates cell cycle progression.
Authors: Boekhout Michiel , Yuan Ruixue , Wondergem Annelotte P. , Segeren Hendrika A. , Liere Elsbeth A. van , Awol Nesibu , Jansen Imke , Wolthuis Rob MF , Bruin Alain de , Westendorp Bart
Published: November 2016

E2F transcription factors control the oscillating expression pattern of multiple target genes during the cell cycle. Activator E2Fs, E2F1-3, induce an upswing of E2F targets, which is essential for the G1-to-S phase transition, whereas atypical E2Fs, E2F7 and E2F8, mediate a downswing of the same targets during late S, G2, and M phase. Expression of atypical E2Fs is induced by E2F1-3, but it is unknown how atypical E2Fs are inactivated in a timely manner. Using molecular assays, time lapse microscopy, and flow cytometry we now demonstrate that E2F7 and E2F8 are substrates of the Anaphase Promoting Cyclosome/Complex (APC/C). Removal of CDH1, or mutating the CDH1-interacting KEN boxes, stabilized E2F7/8 from anaphase onwards and during G1. Expressing KEN-mutant E2F7 during G1 severely impairs S-phase entry and eventually results in cell death. Furthermore, we show that E2F8, but not E2F7, interacts also with APC/CCdc20. Importantly, atypical E2Fs can activate the APC/CCdh1 by repressing its inhibitors Emi1, cyclin A, and cyclin E. In conclusion, we uncovered a feedback loop between atypical E2Fs and APC/CCdh1, which ensures balanced expression of cell cycle genes and normal cell cycle progression.

Citation Format: Michiel Boekhout, Ruixue Yuan, Annelotte P. Wondergem, Hendrika A. Segeren, Elsbeth A. van Liere, Nesibu Awol, Imke Jansen, Rob MF Wolthuis, Alain de Bruin, Bart Westendorp. Feedback regulation between atypical E2Fs and APC/CCdh1 coordinates cell cycle progression.. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B14.
Abstract B19: The oncogenic TBX2 activates the ATM-CHK2-p53 axis to confer cisplatin resistance in breast cancer and melanoma
Authors: Kimani Serah , Wansbelen Sabina , Davis Emily , Peres Jade , Prince Sharon
Published: November 2016

A prominent mechanism through which tumors develop resistance to DNA damaging chemotherapeutic agents is by cancer cells preferentially arresting in S-phase, thereby acquiring the ability to repair drug-induced DNA damage and consequently evading apoptosis. Combining DNA damaging therapies with targeted approaches that disrupt the DNA damage repair process may therefore prove to be more effective against such tumors. The developmentally important transcription factor TBX2 has been suggested as a novel anti-cancer drug target, as it is overexpressed in several cancers and possesses strong anti-senescence and pro-proliferative functions. Indeed, when TBX2 is silenced, we are able to reverse several features of transformation in both breast cancer and melanoma cells. We and others have previously showed that ectopic expression of TBX2 confers resistance to DNA damaging chemotherapeutic drugs, cisplatin and doxorubicin. However, whether endogenous TBX2 confers resistance to these DNA damaging agents in TBX2-driven cancers and the mechanism(s) by which this may occur have not been reported. To address this, we have silenced TBX2 in cisplatin-resistant breast cancer and melanoma cells and we show that knocking down TBX2 sensitizes the cells to cisplatin by disrupting the ATM-CHK2-p53 signalling cascade. Cell cycle analyses demonstrate that when TBX2 is knocked down there is an abrogation of an S-phase arrest but a robust G2/M arrest that correlates with a reduction in p-CHK2 and p53 levels. This prevents DNA repair resulting in TBX2 deficient cells entering mitosis with damaged DNA and consequently undergoing mitotic catastrophe. These results provide compelling evidence that targeting TBX2 in combination with chemotherapeutic drugs such as cisplatin could improve their efficacy and that it may be a viable treatment of TBX2-driven cancers.

Citation Format: Serah Kimani, Sabina Wansbelen, Emily Davis, Jade Peres, Sharon Prince. The oncogenic TBX2 activates the ATM-CHK2-p53 axis to confer cisplatin resistance in breast cancer and melanoma. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B19.
Abstract B22: IT-141, a stabilized polymer micelle formulation, prolongs the pharmacodynamic effect of SN-38
Authors: Sethuraman Jyothi , Costich Tara Lee , Carie Adam , Buley Taylor , Ellis Tyler , Semple J. Edward , Vojkovsky Tomas , Sill Kevin , Bakewell Suzanne
Published: November 2016

IT-141 is a formulation of SN-38 encapsulated in an iron-stabilized polymer micelle. SN-38 is the active metabolite of irinotecan (CPT-11) which in combination with 5-FU and leucovorin is first-line FDA approved therapy for metastatic colorectal cancer. Although SN-38 is 1,000 times more potent than irinotecan alone, there is about 100-fold lower concentration of SN-38 in plasma from irinotecan. In the clinic only 2% to 10% of the administered dose of irinotecan is converted by carboxylesterases to SN-38 and there is great interpatient variability with toxicity. In vitro, IT-141 demonstrated nanomolar IC50s against a panel of human cancer cell lines in comparison to irinotecan's micromolar IC50 concentrations. SN-38 binds to the topoisomerase I-DNA complex resulting in double stranded breaks and cell death. We compared the mechanism of action of IT-141 compared to irinotecan treatment in HT-29 xenografts tumors. We demonstrated the incidence of double stranded breaks by immunohistochemistry (IHC) of γ- H2AX expression in tumors treated with IT-141 compared to irinotecan treatment at different time points (24, 48, 72 and 144 hours). In irinotecan treated tumors, γ- H2AX expression peaked at 72 hours followed by a sharp decrease in expression at 144 hours. In IT-141 treated tumors, γ- H2AX positive staining increased steadily from 24 through 144 hours. This shift in the kinetics of the mechanism corroborates the biodistribution studies where IT-141 delivered 34-fold more SN-38 to the tumor compared to irinotecan. The AUC and Cmax in IT-141 treated tumors was 30.9 μg*h/g and 12.2 μg/g respectively compared to an AUC of 1.1 μg*h/g and a Cmax of 0.2 μg/g in the irinotecan treated tumors. In an HT-29 xenograft model IT-141 inhibited tumor growth by 157% compared to a 57% with irinotecan. IT-141 demonstrates successful encapsulation of SN-38 leading to a safer, more effective formulation. Our DNA damage assay demonstrated that IT-141 extended the pharmacodynamic effect over irinotecan in treated tumors. Further studies are required to determine the duration of IT-141's pharmacodynamics effect. This data validates the increased tumor accumulation of SN-38 and increased efficacy of IT-141 over irinotecan.

Citation Format: Jyothi Sethuraman, Tara Lee Costich, Adam Carie, Taylor Buley, Tyler Ellis, J. Edward Semple, Tomas Vojkovsky, Kevin Sill, Suzanne Bakewell. IT-141, a stabilized polymer micelle formulation, prolongs the pharmacodynamic effect of SN-38. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B22.
Abstract B23: The deubiquitinating enzyme USP37 stabilizes Chk1 to promote the cellular response to replication stress
Authors: Singh Mayank , Pal Debjani , Burrows Amy C. , Messina Abbey , Dickson Andrew , Summers Matthew K.
Published: November 2016

Ubiquitin-mediated proteolysis is a key regulatory process in cell cycle progression. Recently, we identified mutual antagonism between the deubiquitinase USP37 as and the tumor suppressor APCCdh1 to regulate S-phase entry. Here we report that elevated USP37 expression correlates with cellular transformation. Depletion of USP37 leads to diminished cellular proliferation and loss of viability in tumor cells. USP37-depleted cells exhibit altered replication kinetics and increased levels of the DNA damage markers γH2AX and 53BP1 as well as increased sensitivity to agents that induce replication stress. Underlying the increased sensitivity, we find that USP37 interacts with the checkpoint kinase Chk1 and its binding partner Claspin and promotes the response to replication stress by stabilizing the active form of Chk1. In turn, activation of Chk1 promotes the down-regulation of APCCdh1 activity, which requires checkpoint mediated weakening of the USP37-APCCdh1 interaction. Our data suggest a model whereby the temporally regulated interplay of USP37, APCCdh1, and the replication checkpoint machinery promotes the ability of tumor cells to survive their intrinsic replication stress by enhancing replication checkpoint activity and driving the G1/S transition. These data provide an improved understanding of the replication checkpoint, control of APCCdh1, and maintenance of genome stability.

Citation Format: Mayank Singh, Debjani Pal, Amy C. Burrows, Abbey Messina, Andrew Dickson, Matthew K. Summers. The deubiquitinating enzyme USP37 stabilizes Chk1 to promote the cellular response to replication stress. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B23.
Abstract B28: FKBP6 gene is involved in progression of cervical cancer
Authors: Ili Carmen Gloria , Viscarra Tamara , Araya Juan Carlos , Lopez Jaime , Mora Barbara , Retamal Javier , Aedo Susana , Bellolio Enrique , Roa Juan Carlos , Brebi Priscilla
Published: November 2016

Introduction: Cervical Cancer (CC) is an important heath problem in developing countries. The silencing of tumor suppressor genes (TSG) could be implied in cervical carcinogenesis. Methylation microarray showed an aberrant hypermethylation of FKBP6, a potential TSG gen in CC. The aim of this study was to characterizer FKBP6 role in cervical carcinogenesis.

Materials and methods: ECT1 E6/E7 (immortalized normal squamous epithelia cell line) and three CC cell lines: SiHa, C-4I and C-33A were cultivated for experiments. FKBP6 expression was determined by qRT-PCR and western blot. Treatment with 10 μM 5-aza-2′deoxycytidine (5-aza) was performed to evaluate a possible epigenetic regulation. Transfection with pCMV6-FKBP6-GFP (FKBP6) and pCMV6-GFP (Empty) was carried out in SiHa cell line through lipofection followed by G418 selection to obtain stable transfection. Viability and clonogenic assay was performed to evaluate transfected cell behaviour. In other hand, 497 biopsy samples of the cervix were analyzed by FKBP6 immunohistochemistry (48 normal; 192 low-squamous intraepithelial lesions; 200 high- squamous intraepithelial lesions and 57 squamous cervical cancers).

Results: FKBP6 mRNA and protein expression was significantly downregulated in all cervical cancer cell lines respect to ECT1 E6/E7. In western blot, also could be observed a variant of FKBP6 mainly in C-4I cell line. After treatment with 5-aza, mRNA (p<0.001) and protein expression of FKBP6 of all CC cell lines were restored. FKBP6 transfected SiHa showed a significant colony formation (p<0.05) decrease. However, cell viability was found incremented (p<0.001) compared with SiHa transfected with the empty vector. Immunohistochemistry showed an increased expression of FKBP6 in cervical cancer compared with normal (p<0.001).

Conclusions: There is a FKBP6 dysregulation in CC cell lines, and the inactivation mechanism seems to be methylation. Restored expression of FKBP6 in SiHa cell line modifies the tumor phenotype, decreasing colony formation, but increasing cell viability. These results suggest that FKBP6 could be implied in cervical progression, but more studies are necessary to evaluate FKBP6 functions in cervical cancer.

Acknowledgments: FONDECYT N°3130630, Project Corfo N° 09CN14-5960, Project Corfo N°12IDL2-18157. Project FONDECYT N° 11150802, Project FONDECYT N°1115062

Citation Format: Carmen Gloria Ili, Tamara Viscarra, Juan Carlos Araya, Jaime Lopez, Barbara Mora, Javier Retamal, Susana Aedo, Enrique Bellolio, Juan Carlos Roa, Priscilla Brebi. FKBP6 gene is involved in progression of cervical cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B28.
Abstract B29: ZNF516 a potential tumor suppressor gene candidate is implied in tumor progression in cervical cancer
Authors: Ili Carmen Gloria , Viscarra Tamara , Araya Juan Carlos , Lopez Jaime , Mora Barbara , Retamal Javier , Bellolio Enrique , Aedo Susana , Roa Juan Carlos , Brebi Priscilla
Published: November 2016

Background: In Cervical Cancer (CC) the role of HPV is fundamental; however, not all HPV infected women will develop this disease. Therefore, other mechanisms, such as silencing of tumor suppressor genes (TSG), could be implied in cervical carcinogenesis. In a previous study, we constructed methylation microarrays, where we found promoter aberrant hypermethylation of ZNF516 gen in CC, postulating it as TSG candidate. The aim of this study was to characterizer ZNF516 role in cervical carcinogenesis and cell cycle.

Materials and methods: ECT1 E6/E7 (immortalized normal squamous epithelia cell line) and three CC cell lines: SiHa, C-4I and C-33A were cultivated for experiments. ZNF516 expression was determined by qRT-PCR and western blot. Treatment with 10 μM 5-aza-2′deoxycytidine (5- aza) was performed to evaluate a possible epigenetic regulation. Transfection with pCMV6-ZNF516-GFP (ZNF516) and pCMV6-GFP (Empty) was carried out in C-33A cell line through lipofection followed by G418 selection to obtain stable transfection. Viability and clonogenic assay was performed to evaluate transfected cell behaviour. Also, immnunohistochemical analysis was performed in 509 cervical biopsy tissues (55 normal; 188 low-squamous intraepithelial lesions; 205 high- squamous intraepithelial lesions and 57 squamous cervical cancers).

Results: ZNF516 mRNA expression was significantly downregulated in SiHa (p<0.01) and C-33A (p<0.001) respect to ECT1 E6/E7. Western blot showed a deregulated protein expression of ZNF516 in all CC cell lines. After treatment with 5-aza, mRNA (p<0.05) and protein expression of ZNF516 of all CC cell lines were restored. ZNF516 transfected C-33A showed a significant colony formation (p<0.01) and viability (p<0.01) decrease compared with C-33A transfected with the empty vector. Nuclear expression of ZNF516 in cervical biopsies showed a diminished expression in SCC respect to normal epithelia (p<0.001)

Conclusions: There is a clear ZNF516 dysregulation in CC cell lines, and the inactivation mechanism seem to be methylation. Restored expression of ZNF516 in C-33A cell line modifies the tumor phenotype, decreasing cellular viability and colony formation. These results suggest that ZNF516 could be a TSG, and its inactivation promotes CC developing.

Citation Format: Carmen Gloria Ili, Tamara Viscarra, Juan Carlos Araya, Jaime Lopez, Barbara Mora, Javier Retamal, Enrique Bellolio, Susana Aedo, Juan Carlos Roa, Priscilla Brebi. ZNF516 a potential tumor suppressor gene candidate is implied in tumor progression in cervical cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B29.
Abstract IA04: The Targeting of CDK4/6: Have we gone full circle?
Authors: Schwartz Gary K.
Published: November 2016

Cyclin Dependent kinase 4 (CDK4) is a critical kinase that regulates the G1/S phase transition within the cell cycle. There has been a major effort to develop drugs that inhibit this kinase. The first CDK4 inhibitor to be approved is Palbociclib. It is approved in combination with letrozole for the treatment of postmenopausal women with metastatic estrogen receptor (ER)-positive breast cancer as initial endocrine-based therapy. In this study Palbociclib (Palbo) improved median progression free survival (mPFS) from 10.2 months with letrozole alone to 20.2 months with Palbo in the combination therapy [Hazard Ratio (HR) 0.488 (95% CI 0.319, 0.748)]. Response rates were 55.4% with the combination and 39.4% with letrozole alone. Palbo has been tested in other disease including dedifferentiated and well-differentiated liposarcoma where CDK4 is amplified. In this disease Palbo has been reported to increase the PFS at 12 weeks to 66% surpassing the primary end of 40% in patients who had progressed on at least one primary regimen. The major toxicity is neutropenia. Other CDK4 inhibitors are in clinical trial, including LEE001 (Novartis) and LY2835219 (Eli Lilly). These agents exhibit a somewhat different toxicity profile with neutropenia and QTc prolongation with LEE001 and gastrointestinal toxicity with LY2835219. Recently, CDK4 inhibition has been shown to induce either a reversible cell cycle arrest or an irreversible senescent state. The proteolytic turnover of MDM2 appears to be critical for cellular senescence induced by CDK4 inhibition in liposarcoma, breast, lung and glioma cell lines. MDM2 turnover depends on its E3 ligase activity and expression of ATRX. In a small series of liposarcoma patients treated with Palbo the suppression of MDM2 expression correlated with improved clinical outcome suggesting that loss of MDM2 by inhibition of CDK4 could be a predictive biomarker for improved clinical outcome with this class of drugs.

Citation Format: Gary K. Schwartz. The Targeting of CDK4/6: Have we gone full circle? [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr IA04.
Abstract IA10: The senescence response - yin and yang
Authors: Campisi Judith
Published: November 2016

Cellular senescence is a stress response that irreversibly arrests cell proliferation and engages a complex senescence-associated secretory phenotype (SASP). The senescence growth arrest prevents the development of cancer by halting cells at risk for malignant transformation. The SASP, which comprises numerous cytokines, chemokines, growth factors, proteases and small metabolites, serves to optimize tissue repair and regeneration in the face of damage. Despite these beneficial effects, the SASP can be deleterious, especially when senescent cells are chronically present such as when they accumulate during aging and at sites of age-related pathology. In addition, persistent senescent cells can stimulate hyperplastic pathologies, including, ironically, cancer metastases. Recent findings using complex cell culture models and genetically modified mice have provided new insights into the dual nature of the senescence response. Together, these new results hold both enormous promise as well as formidable challenges to developing approaches for maintaining the beneficial effects, while minimizing the deleterious effects, of this complex stress response – with the ultimate goal of delaying or preventing a host of age-related diseases.

Citation Format: Judith Campisi. The senescence response - yin and yang. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr IA10.
Abstract IA12: Targeting the cell cycle in pediatric solid tumors
Authors: Dyer Michael
Published: November 2016

My lab is interested in understanding how proliferation and differentiation are coordinated during development and how those processes become uncoupled in pediatric solid tumors. We are also interested in identifying tumor vulnerabilities that can be exploited therapeutically. We have developed a unique resource for studying the developmental origins of childhood solid tumors and this resource is shared freely with no obligation to collaborate through the Childhood Solid Tumor Network (www.stjude.org/cstn). We have also developed a rigorous and comprehensive preclinical phase I/II/III testing program (Langenau et al. Cancer Research, 2015) that recapitulate many of the features of human clinical trials. In my presentation, I will compare and contrast cell cycle and checkpoint vulnerabilities across 4 pediatric solid tumor types including ongoing efforts to exploit those vulnerabilities in preclinical studies and clinical trials. These examples will provide a foundation for targeting the cell cycle across diverse cancer types.

Citation Format: Michael Dyer. Targeting the cell cycle in pediatric solid tumors. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr IA12.
Abstract PR06: Sox2 functions as a critical oncogene in Rb loss initiated tumors
Authors: Kareta Michael S. , O'Brien Megan , Wernig Marius , Sage Julien
Published: November 2016

Tumor suppressors, while important proteins to in the context of tumor formation, are difficult to target for therapeutic purposes. The Rb tumor suppressor, which is lost or functionally inactivated in nearly every human tumor type, is not unique in that regard because restoration of the loss of Rb function has been challenging. Using cellular reprogramming to iPS cells as a model for tumor formation, we identified Sox2 as a direct target of Rb repression. Sox2 is a core pluripotency member with strong reprogramming abilities, and as such, is a potent oncogene in some cellular contexts. Using mouse genetics and genomic analysis we have confirmed that Sox2 does indeed promote tumor formation upon Rb loss. We have also investigated the consequence of Sox2 suppression in tumors initiated by Rb loss, including small cell lung cancer. This raises the possibility of using Sox2 inhibition as a more clinically feasible form of treatment than restoration of Rb loss.

This abstract is also being presented as Poster B05.

Citation Format: Michael S. Kareta, Jr., Megan O'Brien, Marius Wernig, Julien Sage. Sox2 functions as a critical oncogene in Rb loss initiated tumors. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr PR06.
Targeted Therapies in HER2-Overexpressing Metastatic Breast Cancer
Authors: Labidi Soumaya , Mejri Nesrine , Lagha Aymen , Daoud Nouha , El Benna Houda , Afrit Mehdi , Boussen Hamouda
Published: November 2016

Human epidermal growth factor receptor-2 (HER2) is amplified in 25-30% of breast cancers and is associated with aggressive disease and poorer survival. Multiple anti-HER2 targeted therapies have dramatically changed management and outcome of this subgroup, both in adjuvant and metastatic settings. Despite the improvement of survival thanks to trastuzumab, unclear mechanisms of resistance occur, which has led to the development of new anti-HER2 therapies such as lapatinib, pertuzumab, and trastuzumab emtansine (T-DM1). The optimal sequence of the available drugs is still not well established. All this progress raises the question of toxicity that need to be managed, especially with longer survival of patients. In this article, we review different anti-HER2 therapies used in HER2-positive m etastatic breast cancer.
A Rare Case of Mycosis Fungoides in the Oral Cavity and Small Intestine Complicated by Perforation
Authors: Emge Drew Arthur , Bassuner Juri , Lewis Daniel J. , Duvic Madeleine
Published: November 2016

Extracutaneous involvement in mycosis fungoides (MF) carries a poor prognosis. Oral and gastrointestinal (GI) tract lesions are both rare locations of disease. We describe the clinical findings of one case with oral and GI MF complicated by perforation after systemic antineoplastic treatment, and review the relevant literature. The patient had a 1-year history of MF before development of tongue and palate tumors. He was treated with local electron beam radiation, but re-presented to the hospital after what was found to be small intestine perforation following systemic antineoplastic therapy. The case reveals key insights into the progression and complications of lymphomas with GI tract involvement.