Resistance Mechanisms最新文献

{"title":"Abstract A43: Increased cyclin A expression is associated with antiprogestin resistance and progesterone receptor isoforms ratio in experimental models of breast cancer","authors":"Marina Ayre, M. Bilinski, B. Jacobsen, C. Lanari, V. Fabris","doi":"10.1158/1557-3125.ADVBC17-A43","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A43","url":null,"abstract":"Deregulation of cyclin A expression has been associated with prognosis and tamoxifen responsiveness in breast cancer. We have previously reported an overexpression of cyclin A in two antiprogestin-resistant tumors derived from a hormone-dependent mammary carcinoma induced by medroxyprogesterone acetate (MPA). MPA-induced tumors show high levels of estrogen (ER) and progesterone receptors (PR) and transit through different stages of hormone dependency. Taking into account that antiprogestin-sensitive tumors show higher levels of PR isoform A (PRA) than isoform B (PRB), and that the opposite ratio is observed in the antiprogestin-resistant tumors, we decided to examine the expression of cyclin A in other experimental models containing different PRA/PRB ratios. An increase in cyclin A expression was observed by Western blot (WB) in the acquired antiprogestin-resistant variant C7-2-HIR and in the constitutive resistant C7-HI tumor (1.7 fold and 1.5 fold, respectively) compared to the antiprogestin-responsive tumor C7-2-HI (p Citation Format: Marina Ayre, Melina E. Bilinski, Britta M. Jacobsen, Claudia Lanari, Victoria T. Fabris. Increased cyclin A expression is associated with antiprogestin resistance and progesterone receptor isoforms ratio in experimental models of breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A43.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"1207 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85124209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A37: Combined targeting of estrogen receptor alpha and nuclear transport pathways remodels metabolic pathways to induce apoptosis and overcome tamoxifen resistance","authors":"E. K. Cotul, Kinga Wrobel, L. Yosef, Zeynep Madak-Erdogan","doi":"10.1158/1557-3125.ADVBC17-A37","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A37","url":null,"abstract":"Majority of breast cancer specific deaths occur in women with recurrent, ERα (+), metastatic tumors that are endocrine therapy resistant. There is a critical need for novel therapeutic approaches to resensitize recurrent ERα (+) tumors to endocrine therapies. The objective of this study was to elucidate mechanisms of improved effectiveness of combined targeting of ERα and XPO1, a nuclear transport protein in overcoming endocrine resistance. Using Cignalfinder pathway profiling, Seahorse metabolic profiling, and GC/MS whole metabolite profiling, we found that combination of 4-OH-Tam and selinexor (SXR), an XPO1 antagonist being evaluated in multiple later-stage clinical trials in patients with relapsed and /or refractory hematologic and solid tumor malignancies, inhibited Akt phosphorylation by changing the localization of the kinase. Since we observed dramatic changes in Akt activity, we hypothesized that glucose utilization pathways and consequently metabolic profile of breast cancer cells would change in the presence of 4-OH-Tam and SXR. These cells were more dependent on mitochondria for energy production. Their glucose and fatty acid dependency decreased in the presence of SXR and cells were more dependent on glutamine as the mitochondrial fuel source. In order to examine metabolites that might result in the observed phenotype, we performed whole metabolite profiling and identified proline metabolic pathways to be upregulated when cells were treated with SXR+4-OH-Tam. We demonstrated that combined targeting of XPO1 and ERα rewires metabolic pathways, increases demand on mitochondria, and causes increased production of ROS that would eventually lead to apoptosis. Remodeling metabolic pathways to regenerate new vulnerabilities in endocrine-resistant tumors is novel, and given the need for better strategies for improving therapy response of relapsed ERα(+) tumors, our findings show great promise for uncovering the role ERα-XPO1 crosstalk plays in reducing cancer recurrences. Citation Format: Eylem Kulkoyluoglu Cotul, Kinga Wrobel, Landesman Yosef, Zeynep Madak-Erdogan. Combined targeting of estrogen receptor alpha and nuclear transport pathways remodels metabolic pathways to induce apoptosis and overcome tamoxifen resistance [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A37.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"199 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86231983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract B35: Palbociclib treatment activates FAK and use of palbociclib in combination with the FAK inhibitor PF-562,271 enhances antitumor activity in ER-positive breast cancer cells","authors":"Grant A. Howe, V. Allen, C. Addison","doi":"10.1158/1557-3125.ADVBC17-B35","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-B35","url":null,"abstract":"Cell survival and proliferation is tightly regulated by a number of interacting coordinated signaling proteins including the cyclin-dependent kinases (CDK). Palbociclib, a CDK4/6 inhibitor, has recently been shown to be very effective in the treatment of estrogen receptor (ER) positive breast cancer; however, many patients develop an acquired resistance through as yet incompletely characterized mechanisms. One recently proposed mechanism is compensation by CDK2 (Herrera-Abreu et al., Can Res 2016;76:2301). Focal adhesion kinase (FAK) is a tyrosine kinase that plays a central role in signaling pathway crosstalk and cell survival and invasion. FAK has been previously shown to activate CDK2 in hepatocytes (Flinder et al., J Cell Phys 2013;228:1304), and given its important role in mediating cell survival, we were interested in determining whether FAK-mediated upregulation of CDK2 occurs in palbociclib-treated breast cancer cells, thereby limiting its efficacy. ER-positive MCF7, MDA-MB-134VI, and T47D breast cancer cell lines were thus treated with increasing doses of palbociclib. We observed dose-dependent increases in phospho-FAK Y397, a marker of the active kinase, following palbociclib treatment. We thus used PF-562,271, a selective FAK tyrosine kinase inhibitor, in combination with palbociclib and, not surprisingly, observed an enhanced ability to inhibit cell viability as compared to use of either drug alone. This was concomitant with observed increases in the CDK4/6 inhibitor p27, and with decreases in phospho-RB, which are indicative of reduced CDK2 activity, following treatment with PF-562,271. Our results highlight an unexpected side effect of palbociclib treatment, namely FAK activation, which could potentially contribute to resistance due to activation of CDK2 and inhibition of p27. The mechanism by which palbociclib activates FAK is currently under investigation. Citation Format: Grant Howe, Victoria Allen, Christina L. Addison. Palbociclib treatment activates FAK and use of palbociclib in combination with the FAK inhibitor PF-562,271 enhances antitumor activity in ER-positive breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr B35.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86642742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A48: MET and EGFR interaction promotes acquired resistance to kinase inhibition in TNBC","authors":"Elizabeth A. Tovar, Curt J. Essenburg, Anderson Peck, L. Turner, Z. Madaj, Matthew C. P. Smith, J. Christensen, M. Melnik, E. Haura, Matthew R. Steensma, Carrie Graveel","doi":"10.1158/1557-3125.ADVBC17-A48","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A48","url":null,"abstract":"Triple-negative breast cancer (TNBC) has the worst prognosis of all breast cancers, and the molecular heterogeneity within TNBC heightens the challenge of developing effective targeted therapies. Receptor tyrosine kinases (RTKs), in particular MET and EGFR, are promising therapeutic targets for TNBC due to their high expression in multiple molecular TNBC subtypes and the tendency for cancers to become “kinase addicted.” We and others have demonstrated that MET is highly expressed in TNBC and its expression correlates with poor prognosis. EGFR expression is also elevated in up to 72% of TNBCs and correlates with poor prognosis in TNBC patients. Recently, we demonstrated that MET and EGFR are coordinately and highly expressed across all TNBC subtypes and the efficacy of combined MET and EGFR inhibition in TNBC patient-derived xenograft (PDX) models. Even though MET and EGFR receptors are actionable targets due to their high activity in TNBC, crosstalk between MET and EGFR has been implicated in therapeutic resistance to kinase inhibitors in several cancer types and needs to be evaluated in TNBC. There is strong evidence demonstrating the critical role of redundant RTK signaling networks in resistance to tyrosine kinase inhibitors (TKIs). Specifically, crosstalk between MET and EGFR has been implicated in therapeutic resistance to EGFR or MET inhibitors in colon, gastric, and lung cancers. Since MET and EGFR are highly expressed in a substantial proportion of TNBCs, we used TNBC PDX models and TNBC cell lines to interrogate mechanisms of resistance to MET and EGFR kinase inhibition. We hypothesized that coexpression, interaction, and activation of MET and EGFR promote acquired TKI resistance and an adaptive kinome response in TNBC. Using TNBC PDX models that highly express both MET and EGFR, we evaluated MET and EGFR activity, localization, and interaction after 3 days or 3 weeks of treatment with MET (glesatinib, crizotinib) and/or EGFR inhibitors (erlotinib). After 3 weeks of dual MET and EGFR inhibition in TNBC PDXs, only a small population of “resistant” cells remained. In these resistant populations, we observed increased MET and EGFR colocalization and increased MET and EGFR activation. To understand how colocalization of MET and EGFR promotes signaling redundancy and crosstalk, we asked whether MET and EGFR directly interact in TNBC PDX using a proximity ligation assay (PLA). PLA uses antibody specificity to detect direct protein-protein interactions at physiologic levels in vitro and in vivo. We observed a significant increase in MET EGFR interactions only in resistant cell populations that had been treated with both MET and EGFR inhibitors. AKT and ERK signaling were also increased in TKI-resistant cells, indicating that these are key survival pathways in resistance. Interestingly, we did not observe an increase in MET-EGFR activity or interaction in PDX tumors treated for only 3 days. Even though TNBC cells (HCC70) showed increased colocal","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83823569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A39: Estrogen-driven noncanonical WNT4 signaling is essential for proliferation and survival in lobular carcinoma cells","authors":"Deviyani M. Rao, Rebecca L. Ferguson, Matthew J. Sikora","doi":"10.1158/1557-3125.ADVBC17-A39","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A39","url":null,"abstract":"Invasive lobular carcinoma (ILC) is the second most common histologic subtype of breast cancer. Though >90% of ILC tumors are estrogen receptor (ER)-positive, ILC patients have poorer outcomes than others with ER-positive tumors, suggesting ER biology is unique in ILC cells. We previously identified the Wnt ligand WNT4 as an ILC-specific ER transcriptional target that is critical for both estrogen-induced growth and antiestrogen resistance in ILC cells. We hypothesize that characterizing the WNT4 signaling network in ILC cells will identify novel biomarkers and therapeutic targets for ILC patients. WNT4 signals in a paracrine manner in normal mammary gland and in breast cancer tissues, via secretion from luminal cells to nearby basal or basal-like cells. Inhibiting Wnt secretion with Porcupine-inhibitors (PORCNi) in these contexts blocks WNT4-driven phenotypes. However, we have observed that PORCNi have no effect on ILC cell proliferation. Further, PORCNi combined with siRNA knockdown of PORCN completely suppress secretion of overexpressed WNT3A but not of WNT4. These observations suggest that WNT4 engages its signaling cascade via an atypical mechanism in ILC cells, where WNT4 signals in an autocrine or intracellular manner or is secreted via PORCN-independent mechanisms. Understanding how WNT4 activates signaling is vital to developing appropriate therapeutic strategies, especially as PORCNi have been tested clinically for ILC patients. In both the normal mammary gland and in breast cancer cells, WNT4 engages the canonical Wnt pathway and activates β-catenin-mediated gene regulation. However, ILC cells and tumors lack β-catenin protein (related to loss of E-cadherin); WNT4 must be activating an alternative signaling cascade in ILC cells. To define downstream WNT4 signaling in ILC cells, we utilized reverse phase protein arrays (RPPA) and identified ER-mediated protein changes blocked by concurrent WNT4 knockdown. These experiments identified putative targets that link WNT4 signaling to control of proliferation and cell cycle as well as apoptosis and cell survival. In the former, coordinate suppression of p21 and induction of FOXM1 control G1/S and G2/M transitions, respectively, and WNT4 knockdown engages both checkpoints to halt cellular proliferation. In the latter, WNT4 activates distinct components of Akt/mTOR signaling in ILC versus IDC cells, as E2 treatment increases phosphorylation of mTOR/Rictor but not of Akt in ILC cells. Activation of mTOR correlates with post-transcriptional regulation of levels of the anti-apoptotic BCL2-family protein MCL-1; E2-mediated suppression of MCL-1 protein levels via mTOR may regulate cell survival and sensitivity to apoptotic stimuli. WNT4 mediates a critical ER-driven pathway in ILC cells, but the WNT4 signaling network has not been characterized to identify putative therapeutic approaches for ILC patients. Our data suggest that targeting FOXM1, mTOR, or BCL2-family proteins may modulate ER/WNT4 signal","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87803595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A46: KLF4 overcomes tamoxifen resistance by suppressing MAPK signaling pathway in breast cancer","authors":"Yunlu Jia, Wang Linbo","doi":"10.1158/1557-3125.ADVBC17-A46","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A46","url":null,"abstract":"Kruppel-like factor 4 (KLF4) has critical roles in breast cancer development and progression and several solid tumors. Tamoxifen (TAM) resistance represents a daunting challenge to the successful treatment of breast cancer. KLF4 expression, function, and regulation in the efficacy of TAM therapy in breast cancer have yet to be demonstrated. Here, we investigated the clinical significance and biologic effects of KLF4 in breast cancer. Firstly, higher expression of KLF4 was correlated with increased TAM sensitivity in breast cells, and analysis of GEO datasets indicated that KLF4 expression was positively correlated with ERa and enhanced expression of KLF4 sensitized breast cancer patients to endocrine therapy. Knockdown of KLF4 in MCF-7 and BCAP37 cells led to increased TAM resistance, while ectopic KLF4 expression promoted the responsiveness of MCF-7/TAM and T47D cells to TAM. Secondly, ectopic KLF4 overexpression suppressed MCF-7/TAM cell growth, invasion, and migration ability. Besides, KLF4 expression was downregulated in breast cancer tumor tissues and high expression of KLF4 linked to favorable outcome. Mechanistically, KLF4 may enhance the responsiveness of breast cancer cells to TAM through suppressing mitogen-activated protein kinase (MAPK) signaling pathway. We found that ERK and P38 were relatively activated in MCF-7/TAM compared with MCF-7, and treatment with MAPK-specific inhibitors can significantly suppress cell viability. Knockdown of KLF4 activated ERK and P38 and drove MCF-7 cells to become resistant to TAM. Conversely, overexpression of KLF4 in MCF-7/TAM cells suppressed ERK and P38 signaling and resulted in enhanced sensitivity to TAM. Therefore, our findings suggest that KLF4 contributes to TAM efficiency in breast cancer via phosphorylation modification of ERK and P38 signaling. Collectively, this study highlighted the significance of KLF4/MAPK signal interaction in regulating TAM resistance of breast cancer, and suggested that targeting the KLF4/MAPK signaling may be a potential therapeutic strategy for breast cancer treatment, especially for TAM-resistant patients. Note: This abstract was not presented at the conference. Citation Format: Yunlu Jia, Wang Linbo. KLF4 overcomes tamoxifen resistance by suppressing MAPK signaling pathway in breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A46.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82621981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A35: Characterizing the role of the nuclear coactivator AIB1 in triple-negative breast cancer","authors":"F. Saenz, A. Wellstein, A. Riegel","doi":"10.1158/1557-3125.ADVBC17-A35","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A35","url":null,"abstract":"Individuals diagnosed with triple-negative breast cancer (TNBC), a highly invasive and frequently metastatic breast cancer subtype, do not benefit from targeted therapies. TNBC is a heterogenous disease and can be further subdivided by intrinsic molecular subtyping into basal-like 1 or 2 (BL-1, BL-2), immunomodulatory (IM), mesenchymal (M), mesenchymal stem-like (MSL), and luminal androgen receptor (LAR). Amplified in Breast Cancer 1 (AIB1) is an oncogene that is frequently overexpressed in higher-grade and invasive breast cancers. AIB1 regulates the transcription of several genes through hormone or growth factor signaling. Many of these signaling pathways are involved in cellular growth, differentiation, migration, and metabolism—all of which become deregulated during oncogenesis. In this study, we silence AIB1 by shRNA and study the phenotypic effects in a panel of TNBC cell lines from different TNBC subtypes in vitro. We have established TNBC HCC1806 cell lines expressing low levels of AIB1 and have characterized their phenotype compared to scramble control cells. We observe significant reduction in AIB1 message and protein as detected by RT-qPCR and Western blot. shAIB1 TNBC cells have a significant reduced survival following the initial knockdown. However, serial passaging of surviving cells show differences in proliferation, especially in low serum conditions. These AIB1LOW cells have a significant increase in motility shown in chemotaxis experiments. However, we observe delayed adhesion of AIB1LOW cells when seeded onto plastic culture vessels. Furthermore, when grown onto Matrigel, AIB1LOW cells have a significant reduced tube formation capacity related to their delayed adhesion or reduced motility on substratum. Additionally, AIB1LOW cells have a differential expression of cell surface markers associated with cancer stem cells (i.e., CD24, CD44, CD133). Consistent with these findings, AIB1LOW cells generate tumorspheres more efficiently under serum free in suspension and when embedded in Matrigel. Moreover, AIB1LOW cells develop aggressive phenotypically different tumors in the cleared mammary fat pad of nude mice compared to controls. The AIB1LOW cells are significantly less sensitive to chemotherapy agents and may represent a resistant population that emerges from cancer stem cells following therapy. Interestingly, AIB1LOW cells have a different regulation of genes associated with hypoxia, glycolysis, and apoptosis and these changes may give guidance as to therapy following emergence of resistance in TNBC patients. Citation Format: Francisco R. Saenz, Anton Wellstein, Anna T. Riegel. Characterizing the role of the nuclear coactivator AIB1 in triple-negative breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A35.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83893020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A36: Chemosensitivity to trastuzumab emtansine (T-DM1) differs in naturally or transduced HER2-overexpressing human breast cancer cells","authors":"Jeffrey H. Wu, L. Muldoon, E. Neuwelt","doi":"10.1158/1557-3125.ADVBC17-A36","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A36","url":null,"abstract":"Human epidermal growth factor receptor-2 (HER2) is overexpressed in 25-30% of breast cancers and is associated with distant metastasis and poor survival. Trastuzumab emtansine (T-DM1), an antibody-drug conjugate of anti-HER2 mAb trastuzumab linked to microtubule-targeting agent mertansine, has been approved for the treatment of HER2-positive metastatic breast cancer. Chemoresistance has been a major obstacle to T-DM1 treatment, and mechanisms remain incompletely understood. We tested T-DM1 chemosensitivity in vitro and in vivo using two human breast cancer cell lines, MDA-MB-231BR-HER2 (triple-negative cells stably transfected with HER2 plasmid) and HCC1954 (natural HER2 overexpression), which show equivalent HER2 and αv integrin protein levels. MDA-MB-231BR-HER2 was strongly resistant to T-DM1, with doses as high as 1 µg/ml failing to induce apoptosis indicated by the presence of cleaved PAPR protein. In contrast, HCC1954 cells are sensitive to T-DM1, with doses as low as 10 ng/mL causing cytotoxicity in a dose-dependent manner. Cellular internalization of trastuzumab-pHrodo conjugates was significantly higher in HCC1954 than MDA-MB-231BR-HER2, but no difference was found in anti-EGFR-Ab-pHrodo conjugates internalization. Endocytosis-related proteins caveolin-1 and rab5, but not early endosome antigen, were diminished in HCC1954 cells. Consistently, single-dose treatment with T-DM1 (3.6 mg/kg, IV) significantly reduced brain tumor volume in rats inoculated with HCC1954 but not MDA-MB-231BR-HER2 cells in an intracerebral xenograft breast cancer brain metastasis model. In conclusion, our findings suggest that rab5 and caveolin-1 proteins mediating antibody internalization and/or natural vs transduced HER2 overexpression may provide possible mechanisms in resistance of T-DM1 and should be investigated when HER2-positive cancer patients fail T-DM1 HER2-targeted therapy in clinical settings. Citation Format: Jeffrey Wu, Leslie Muldoon, Edward Neuwelt. Chemosensitivity to trastuzumab emtansine (T-DM1) differs in naturally or transduced HER2-overexpressing human breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A36.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85052093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A49: Modeling “decathlon winner” cancer cells that drive therapy resistance and metastasis in triple-negative breast cancer","authors":"Balraj Singh, V. Sarli, A. Lucci","doi":"10.1158/1557-3125.ADVBC17-A49","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-A49","url":null,"abstract":"Introduction: There is a pressing need for reliable models for testing potential therapeutic drugs that accurately predict how drugs will act in cancer patients. Cancer resembles an evolution-like process in the body involving epigenetic and genetic alterations in tumor cells accompanied by a selection for their fitness to survive multiple challenges in the body. Therefore, we are developing an approach designed to test whether a therapy would affect most adaptable/evolvable cancer cells. We hypothesize that there is a two-way linkage between the regulatory state and the metabolic state, which can be exploited for selecting highly adaptable “decathlon winner” cancer cells. Methods: To model the intrinsic resistance in triple-negative breast cancer that often overwhelms currently offered therapies, we selected rare cancer cells (0.01% in population) based on their ability to survive a severe metabolic challenge, i.e., a prolonged lack of glutamine in culture medium of SUM149 and FC-IBC02 triple-negative Inflammatory Breast Cancer (IBC) cell lines. The rationale is that if a cancer cell can survive such a severe challenge, it can survive all other challenges encountered in the body. Results: The rare metabolically adaptable (MA) cancer cells, which survive and grow without glutamine indefinitely, are resistant to chemotherapeutic drugs, and highly metastatic to multiple organs—lungs, liver, brain, and skin—from fat pad xenografts in nude mice (Singh et al., PLoS ONE, 2012). The MA cells are resistant to most drugs tested thus far as single agent, supporting the validity of our cell-based model for testing new therapies (Singh et al., PLoS ONE, 2014). We have strong evidence of epithelial-to-mesenchymal transition (EMT) in MA cells, as indicated by reduced expression of GRHL2, increased expression of ZEB1, and reduced expression of ESRP1 (epithelial splicing regulatory protein 1) and a consequently increased level of CD44s, to name a few critical alterations. There is a strong correlation between EMT and a progenitor-like cell state. Investigating the molecular characteristics of SUM149-MA cells, we found that MA cells produced a very low level of TET2 methylcytosine dioxygenase (5- to 10-fold reduction) compared with the parental SUM149 cell line. TET2 could represent a link between the metabolic state and the epigenetic state in progenitor-like MA cells; its activity could be regulated both in terms of expression levels and by allosteric regulation with metabolites. We have recently reported that an RNA demethylase, FTO, which is important in organismal survival under food shortages and also controls obesity, plays an important role in the survival of MA cells (Singh et al., PLoS ONE, 2016). We also observed that SUM149-MA cells overexpress ADARB2, an RNA-editing adenosine deaminase converting adenosine to inosine, which is interestingly associated with extreme old age in humans. ADARB2 can also influence lifespan in Caenorhabditis elegans . These","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87205251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract B38: The role of BQ323636.1, a novel splice variant of NCOR2, in modulation of oxidative stress in breast cancer","authors":"M. Leung, H. Tsoi, E. Man, E. Lam, U. Khoo","doi":"10.1158/1557-3125.ADVBC17-B38","DOIUrl":"https://doi.org/10.1158/1557-3125.ADVBC17-B38","url":null,"abstract":"Breast cancer is the most common type of female cancer. Reactive oxygen species (ROS) plays an important role in the signaling pathways governing survival and proliferation of breast cancer cells. Several chemotherapeutic drugs, such as taxanes, platinum compounds, and anthracyclines, induce cell death by enhancing the levels of ROS. Nuclear factor erythroid 2-related factor 2 (NRF2) is the master transcription factor regulating antioxidative responses against ROS. Overexpression of NRF2 has been found in breast cancer and it modulates oxidative stress response, leading to drug resistance in cancers. Our previous splice array study identified a novel splice variant of NCOR2, BQ323636.1 (BQ), as predictor of tamoxifen resistance in breast cancer. In the current study, we show overexpression of BQ could promote cell proliferation and protect cells from oxidative stress. In addition, overexpression of BQ could reduce the levels of ROS in breast cancer cells. We therefore hypothesized that BQ could compromise oxidative stress via the NRF2 pathway. By qPCR assay, several downstream targets of NRF2 were found to be upregulated in BQ-overexpressing cells. This suggested that NRF2 transcriptional activity could be modulated by BQ. The results from luciferase reporter assay confirmed that NCOR2 could repress the transcriptional activity via antioxidant response element (ARE), the primary binding site of NRF2 in promoter region. BQ could reverse the repressive effect of NCOR2 on ARE, suggesting that BQ might modulate NRF2 activity via NCOR2. Co-immunoprecipitation indicated NCOR2 interacted with NRF2. BQ overexpression might inhibit such an interaction. Taken together, our results suggest that BQ regulates NRF2 signaling pathway via interfering with NCOR2 activity. Our findings reveal a novel role for BQ as a modulator of NRF2 and oxidative stress in breast cancer. Citation Format: Man Hong Leung, Ho Tsoi, Ellen Pui Sum Man, Eric Wing-Fai Lam, Ui Soon Khoo. The role of BQ323636.1, a novel splice variant of NCOR2, in modulation of oxidative stress in breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr B38.","PeriodicalId":20897,"journal":{"name":"Resistance Mechanisms","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87466179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}