Resistant Xenografts Research Articles

TMIC-42. LOCAL TISSUE METABOLOMICS BASED BIOMARKERS OF RESPONSE TO THERAPY FOR GLIOBLASTOMA

Abstract Glioblastoma (GBM) is a common deadly malignant brain cancer of the central nervous system (CNS), with a median survival of 12–15 months. Scientific advancements are lacking in developing effective therapies for both primary GBM, as well as secondary GBMs, that typically originate as malignant transformation of lower-grade isocitrate dehydrogenase (IDH) 1-mutant tumors. The unique metabolomic profile of IDH1-mutant tumors may present opportunities to develop biomarker signatures of therapeutic efficacy. Microdialysis is an extracellular fluid sampling collection technique utilizing a perfused semipermeable catheter to permit diffusion of molecules between brain interstitium and the perfusate. We hypothesized that microdialysis may identify a metabolomics-based biomarker response to therapy in IDH1-mutant tumors. To test this hypothesis, orthotopic xenografts were generated from two patient-derived GBM lines harboring mutations in IDH1. Perfusates were collected from intra-cranial tumors in aythmic nude mice sampled at baseline and 72h post treatment with temozolomide, an oral alkylating agent used to treat IDH1-mutant gliomas, compared with vehicle treatment, and TMZ-treated non-tumor bearing animals. Perfusates were analyzed via unsupervised metabolomic profiling using both gas and liquid chromatography-mass spectrometry (GC/LC-MS). Tumor specific metabolites such as carnitine and pyruvic acid were detected in microdialysate from tumor bearing mice compared to non-tumor bearing mice. Microdialysis is a feasible technology to identify metabolomics-based biomarker in IDH1-mutant PDX. This work is complemented by parallel analysis of non-IDH1-mutant and TMZ resistant xenografts to yield predictive in vivo tissue biomarkers of drug responsiveness translatable to clinical practice.

Phloretin attenuates STAT-3 activity and overcomes sorafenib resistance targeting SHP-1\u2013mediated inhibition of STAT3 and Akt/VEGFR2 pathway in hepatocellular carcinoma

BackgroundHepatocellular carcinoma (HCC) is the most common primary liver malignancy. Phloretin (PH) possesses anticancer, antitumor, and hepatoprotective effects, however, the effects and potential mechanisms of phloretin remain elusive.MethodsFive HCC cells were tested in vitro for sensitivity to PH, Sorafenib (Sor) or both and the apoptosis, signal transduction and phosphatase activity were analyzed. To validate the role of SHP-1, we used PTP inhibitor III and SHP-1 siRNA. Further, we used purified SHP-1 proteins or HCC cells expressing deletion N-SH2 domain or D61A point mutants to study the PH efficacy on SHP-1. The `in vivo studies were conducted using HepG2 and SK-Hep1 and Sor resistant HepG2SR and Huh7SR xenografts. Molecular docking was done with Swiss dock and Auto Dock Vina.ResultsPH inhibited cell growth and induced apoptosis in all HCC cells by upregulating SHP-1 expression and downregulating STAT3 expression and further inhibited pAKT/pERK signaling. PH activated SHP-1 by disruption of autoinhibition of SHP-1, leading to reduced p-STAT3Tyr705 level. PH induced apoptosis in two Sor-resistant cell lines and overcome STAT3, AKT, MAPK and VEGFR2 dependent Sor resistance in HCCs. PH potently inhibited tumor growth in both Sor-sensitive and Sor-resistant xenografts in vivo by impairing angiogenesis, cell proliferation and inducing apoptosis via targeting the SHP-1/STAT3 signaling pathway.ConclusionOur data suggest that PH inhibits STAT3 activity in Sor-sensitive and -resistant HCCs via SHP-1–mediated inhibition of STAT3 and AKT/mTOR/JAK2/VEGFR2 pathway. Our results clearly indicate that PH may be a potent reagent for hepatocellular carcinoma and a noveltargeted therapy for further clinical investigations.Graphical abstract

Tie2-FGFR1 Interaction Induces Adaptive PI3K Inhibitor Resistance by Upregulating Aurora A/PLK1/CDK1 Signaling in Glioblastoma.

PI3K-targeting therapy represents one of the most sought-after therapies for glioblastoma (GBM). Several small-molecule inhibitors have been evaluated in clinical trials, however, the emergence of resistance limits treatment potential. Here, we generated a patient-derived glioma sphere-forming cell (GSC) xenograft model resistant to the PI3K-specific inhibitor BKM-120. Integrated RNA sequencing and high-throughput drug screening revealed that the Aurora A kinase (Aurora A)/Polo-like kinase 1 (PLK1)/cyclin-dependent kinase 1 (CDK1) signaling pathway was the main driver of PI3K inhibitor resistance in the resistant xenografts. Aurora kinase was upregulated and pCDK1 was downregulated in resistant tumors from both xenografts and tumor tissues from patients treated with the PI3K inhibitor. Mechanistically, the tyrosine kinase receptor Tie2 physically interacted with FGFR1, promoting STAT3 phosphorylation and binding to the AURKA promoter, which increased Aurora A expression in resistant GSCs. Concurrent inhibition of Aurora A and PI3K signaling overcame PI3K inhibitor-induced resistance. This study offers a proof of concept to target PI3K and the collateral-activated pathway to improve GBM therapy. SIGNIFICANCE: These findings provide novel insights into the mechanisms of PI3K inhibitor resistance in glioblastoma.

Deciphering the transcriptional modulation program of trabectedin in sensitive and resistant patient derived xenograft models of myxoid liposarcoma

Deciphering the transcriptional modulation program of trabectedin in sensitive and resistant patient derived xenograft models of myxoid liposarcoma

Glutamine Metabolism Drives Growth in Advanced Hormone Receptor Positive Breast Cancer.

Dependence on the glutamine pathway is increased in advanced breast cancer cell models and tumors regardless of hormone receptor status or function. While 70% of breast cancers are estrogen receptor positive (ER+) and depend on estrogen signaling for growth, advanced ER+ breast cancers grow independent of estrogen. Cellular changes in amino acids such as glutamine are sensed by the mammalian target of rapamycin (mTOR) complex, mTORC1, which is often deregulated in ER+ advanced breast cancer. Inhibitor of mTOR, such as everolimus, has shown modest clinical activity in ER+ breast cancers when given with an antiestrogen. Here we show that breast cancer cell models that are estrogen independent and antiestrogen resistant are more dependent on glutamine for growth compared with their sensitive parental cell lines. Co-treatment of CB-839, an inhibitor of GLS, an enzyme that converts glutamine to glutamate, and everolimus interrupts the growth of these endocrine resistant xenografts. Using human tumor microarrays, we show that GLS is significantly higher in human breast cancer tumors with increased tumor grade, stage, ER-negative and progesterone receptor (PR) negative status. Moreover, GLS levels were significantly higher in breast tumors from African-American women compared with Caucasian women regardless of ER or PR status. Among patients treated with endocrine therapy, high GLS expression was associated with decreased disease free survival (DFS) from a multivariable model with GLS expression treated as dichotomous. Collectively, these findings suggest a complex biology for glutamine metabolism in driving breast cancer growth. Moreover, targeting GLS and mTOR in advanced breast cancer may be a novel therapeutic approach in advanced ER+ breast cancer.

Targeting cyclin-dependent kinase 9 by a novel inhibitor enhances radiosensitization and identifies Axl as a novel downstream target in esophageal adenocarcinoma.

Cyclin-dependent kinase 9 (CDK9) transcriptionally regulates several proteins and cellular pathways central to radiation induced tissue injury. We investigated a role of BAY1143572, a new highly specific CDK9 inhibitor, as a sensitizer to radiation in esophageal adenocarcinoma. In vitro synergy between the CDK9 inhibitor and radiation was evaluated by clonogenic assay. In vivo synergy between the CDK9 inhibitor and radiation was assessed in multiple xenograft models including a patient’s tumor derived xenograft (PDX). Reverse phase protein array (RPPA), western blotting, immunohistochemistry, and qPCR were utilized to identify and validate targets of the CDK9 inhibitor. The CDK9 inhibitor plus radiation significantly reduced growth of FLO-1, SKGT4, OE33, and radiation resistant OE33R xenografts and PDXs as compared to the cohorts treated with either single agent CDK9 inhibitor or radiation alone. RPPA identified Axl as a candidate target of CDK9 inhibition. Western blot and qPCR demonstrated reduced Axl mRNA (p = 0.02) and protein levels after treatment with CDK9 inhibitor with or without radiation in FLO-1 and SKGT4 cells. Axl protein expression in FLO-1 xenografts treated with combination of CDK9 inhibitor and radiation was significantly lower than the xenografts treated with radiation alone (p = 0.003). Clonogenic assay performed after overexpression of Axl in FLO-1 and SKGT4 cells enhanced radiosensitization by the CDK9 inhibitor, suggesting dependency of radiosensitization effects of the CDK9 inhibitor on Axl. In conclusion, these findings indicate that targeting CDK9 by BAY1143572 significantly enhances the effects of radiation and Axl is a novel downstream target of CDK9 in esophageal adenocarcinoma.

Abstract 3185: CAR-T cells can eradicate human uveal melanoma and immune-therapy resistant malignant melanoma in IL-2 transgenic NOD/SCID IL2 receptor gamma knockout mice

Abstract Immune therapies including checkpoint blockade and adoptive T cell transfer show great promise for the treatment of melanoma, with long-term effects in some patients. However, not all patients respond to current immune therapies and are in need of other treatment strategies. For example, around half of the patients with metastatic malignant melanoma will not be cured with available therapies today. For metastatic uveal melanoma (a rare melanoma of the eye) available immune therapies have less effect, and there is currently no approved therapy for these patients. Our objective is to find novel immune therapies with the potential to treat immune-therapy resistant melanoma, with the use of chimeric antigen receptor T cells (CAR-T). So far, no CAR-T therapy is approved for use in solid tumors. We have previously developed a humanized mouse model, where tumor cells and T cells from the same patient are grafted in IL-2 transgenic NOD/SCID IL2 receptor gamma knockout (NOG) mice, and found that responses in the mouse model correlated to responses in the corresponding patients in a clinical trial of adoptive T cell transfer (Jespersen et al, Nature Communications, 2017). In order to test the potential for CAR-T therapy in immune-therapy resistant melanoma in this mouse model, we used TCGA to determine the expression in melanoma biopsies of targets for commercially available CAR-T cells. Interestingly, we were able to use this model to treat immune-therapy resistant malignant melanoma and uveal melanoma patient-derived xenografts with human CAR-T cells and obtain curative responses, but only in IL-2 transgenic mice and not in regular NOG mice. These findings prove potential for the use of CAR-T cell therapy in immune-therapy resistant melanoma, and indicate the utility of this mouse model in the translation of CAR-T therapies. We are currently working on the development of CAR-T cells derived from patient-specific T cells. Citation Format: Elin Forsberg, Mattias Lindberg, Henrik Jespersen, Samuel Alsén, Roger Olofsson Bagge, Marco Donia, Inge Marie Svane, Ola Nilsson, Lars Ny, Lisa Nilsson, Jonas Nilsson. CAR-T cells can eradicate human uveal melanoma and immune-therapy resistant malignant melanoma in IL-2 transgenic NOD/SCID IL2 receptor gamma knockout mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3185.

Abstract 216: pro-Pyrrolobenzodiazepine (pro-PBD) bioconjugates, the legacy: Design and synthesis of pro-PBD conjugates containing self-immolative substituted disulfide linkers

Abstract Naturally occurring pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are a group of highly potent antitumor antibiotics, isolated from various streptomycin species. PBDs covalently bond and cross-link with discrete sequences of base pairs in the minor groove of DNA. A wide range of synthetic PBDs and PBD dimers have been shown to be highly potent cytotoxic agents, and have been used as payloads in antibody drug conjugates (ADCs). However, all PBDs as stand-alone agents or as delivered via small molecule drug conjugates (SMDCs), cause undesired off-target toxicity. Recently, we designed folate conjugated pro-PBDs, masking the imine moiety with its synthetic precursors: namely, 1,3-oxazolidine carbamate and an aromatic amine. The 1,3-oxazolidine carbamate provided a conjugation site for attachment of pro-PBD to a targeting ligand. After delivery to the targeted cell and internalization, reductive cleavage of the linker system results in the generation of a 1,3-oxazolidine. The oxazolidine reacts with water to form an aldehyde which subsequently reacts intramolecularly to ultimately form the PBD diazepine ring. Herein, we report the design and synthesis of folate conjugates of pro-PBDs and self-immolative sterically hindered disulfide linker systems, which pave the way toward novel, highly-specific therapeutics which have the potential to minimize off-target toxicities. One of the so designed conjugates, EC2629, satisfied all of our criteria for selection for pre-clinical development: • EC2629 shows high affinity towards FR mediated binding. • Cross-links DNA only following self-immolative release of free drug. • Picomolar potency against FR-expressing cells. • Curative activity with no weight loss in animal models. • Active against drug resistant tumor xenograft models in-vivo. • EC2629 is active against patient derived xenograft models in-vivo. • Based on high cytotoxicity and minimal off target toxicity (in-vitro & in-vivo), EC2629 is selected for pre-clinical development. • Biological evaluation of EC2629 was presented at World ADC, Berlin, Germany (March, 2018). Citation Format: Iontcho Vlahov, Longwu Qi, Hari K. Santhapuram, Garth Parham, Kevin Wang, Jeremy F. Vaughn, Spencer J. Hahn, Marilynn Vetzel, Melissa Nelson, Joseph A. Reddy, Christopher P. Leamon. pro-Pyrrolobenzodiazepine (pro-PBD) bioconjugates, the legacy: Design and synthesis of pro-PBD conjugates containing self-immolative substituted disulfide linkers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 216.

Abstract 3508: Combination of the Chk1 inhibitor (prexasertib) with a PI3K/mTOR inhibitor (LY3023414) induces synergistic anti-tumor activity in triple negative breast cancer (TNBC) models

Abstract TNBC, the most aggressive subtype of breast cancer, is characterized by high level of genomic instability, defects in DNA damage response (DDR) and increased replication stress (RS). The current treatment options for TNBC are limited and new approaches are needed. Checkpoint kinase 1 (Chk1) is a key protein kinase that regulates the cell cycle, DNA damage and RS response, and has emerged as an attractive target for anticancer therapy. Prexasertib, an ATP-competitive inhibitor of Chk1 has demonstrated activity in vitro and in vivo across a variety of tumor histologies. Prexasertib is being evaluated in patients with TNBC in a Phase II study sponsored by NCI (NCT02203513). The preliminary results reported in 2016 showed modest single agent activity. PI3K/AKT/mTOR is a critical pathway with key roles on cancer cell survival, homologous recombination repair and drug resistance. Our previous study indicated the expression level of genes related to PI3K/AKT signaling is elevated in prexasertib resistant TNBC patient-derived xenograft (PDX) models. It is hypothesized that inhibiting both the Chk1 and PI3K/AKT pathway may improve prexasertib efficacy. In this study, we evaluated the combination effect of prexasertib with a PI3K/mTOR inhibitor (LY3023414, a selective dual inhibitor of PI3K and mTOR, which is being investigated in Phase 2 clinical trials) in TNBC in vitro and in vivo. The prexasertib/LY3023414 combination induced the synergistic or additive inhibition on cell proliferation in 10 of 12 TNBC cell lines. The prexasertib/LY3023414 combination enhanced DNA damage (γH2AX), replication stress (phospho-RPA32) and proliferation inhibition in MDA-MB-231 cells when compare with single agent treatment. In three TNBC xenograft models (HCC1806, HCC1187 and MX-1) LY3023414 induced 0%, 62% and 24% tumor inhibition; prexasertib induced 94%, 78% and 96% tumor inhibition; and the combination led to 35%, 61% and 21% tumor regression, respectively. The prexasertib/LY3023414 combination also increased the inhibition of both primary tumor growth and spontaneous lung metastasis in a MDA-MB-231 mammary fat pad orthotopic model when compared with the respective single agent activity. The efficacy of prexasertib/LY3023414 combination was further assessed in 38 TNBC PDX models, and the combination showed a synergistic effect in 8 of 38 models and an additive effect in 22 of 38 models. Overall, the combined inhibition of Chk1 and PI3K/mTOR pathway enhanced antitumor activity in TNBC models. Taken together, these data will inform the clinical development of potential combination of Chk1 inhibitor prexasertib with a PI3K/mTOR inhibitor in the treatment of TNBC patients. The safety of this combination is being assessed in an ongoing Phase 1b clinical trial (NCT02124148), which includes an expansion cohort focused on patients with TNBC. Citation Format: Wenjuan Wu, Greg Donoho, Philip Iversen, Jack Dempsey, Andrew Capen, Mark Castanares, Jennifer Stephens, Karsten Boehnke, Christoph Reinhard Reinhard, Aimee Lin. Combination of the Chk1 inhibitor (prexasertib) with a PI3K/mTOR inhibitor (LY3023414) induces synergistic anti-tumor activity in triple negative breast cancer (TNBC) models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3508.

Abstract 1320: Preclinical evaluation of TQB3804, a potent EGFR C797S inhibitor

Abstract Objective: Osimertinib is the 3rd generation EGFR inhibitor, which has been approved for the treatment of NSCLC patients with EGFRT790M. More recently, a tertiary EGFRC797S mutation was reported as the dominant resistance (40~20%) mechanism to Osimertinib. The emergence of C797S mutation prevent covalent bond formation with Osimertinib, and caused the drug resistance. So, it’s an urgent demand for new EGFR inhibitors that can effectively inhibit EGFR triple mutant, d746-750/T790M/C797S & L858R/T790M/C797S. Here, we disclose our clinical candidate, TQB3804, as a novel 4th generation inhibitor that potently inhibits triple mutants. Methods: The enzyme activities of TQB3804 for EGFRd746-750/T790M/C797S, EGFRL858R/T790M/C797S, EGFRd746-750/T790M, EGFRL858R/T790M, and EGFRWT were measured with corresponding kinase assays. The anti-proliferative activity was evaluated in Ba/F3 (EGFRd746-750/T790M/C797S), NCI-H1975 (EGFRd746-750/T790M/C797S), PC9 (EGFRd746-750), and A431 (EGFRWT) cell lines, and the phosphorylation of EGFR was also evaluated in Ba/F3 (EGFRd746-750/T790M/C797S) cell line. Antitumor activity of TQB3804 was evaluated in three triple mutant cell-derived tumor xenograft (CDX) models Ba/F3 (EGFRd746-750/T790M/C797S), NCI-H1975 (EGFRd746-750/T790M/C797S), and PC9 (EGFRd746-750/T790M/C797S) and one Osimertinib resistant patient-derived xenograft (PDX) model of NSCLC (LUPF104, EGFRd746-750/T790M/C797S). Results: TQB3804 displayed potent enzymatic activities for EGFRd746-750/T790M/C797S, EGFRL858R/T790M/C797S, EGFRd746-750/T790M, and EGFRL858R/T790M with IC50 of 0.46, 0.13, 0.26, and 0.19 nM respectively, and has similar enzymatic activity for EGFRWT (IC50 = 1.07) to Osimertinib. It also showed expected anti-proliferative activity in 4 cell lines, Ba/F3 (EGFRd746-750/T790M/C797S), NCI-H1975 (EGFRd746-750/T790M/C797S), PC9 (EGFRd746-750), and A431 (EGFRWT), with IC50 of 26.8, 163, 45, and 147 nM, respectively. The phosphorylation for EGFR in Ba/F3 (EGFRd746-750/T790M/C797S) cell line was potently inhibited with IC50 =18.5 nM. TQB3804 significantly inhibited tumor growth in the triple mutant Ba/F3 (EGFRd746-750/T790M/C797S), NCI-H1975 (EGFRd746-750/T790M/C797S), and PC9 (EGFRd746-750/T790M/C797S) CDX models, as well as in the LUPF104 PDX model. Western blot analysis of the tumor samples in the Ba/F3 (EGFRd746-750/T790M/C797S) CDX model showed that TQB3804 inhibited p-EGFR, p-AKT and p-ERK indicating that the tumor growth inhibition was through inhibition of the resistant triple mutant EGFR. Conclusions: We have identified a potent orally active 4th generation EGFR inhibitor, TQB3804. It can inhibit the activity of Osimertinib resistant triple mutant EGFR, and showed strong antitumor activity in corresponding in vitro and in vivo preclinical assays. These results are considered highly promising and warrant moving the compound forward to clinical investigation. Citation Format: Xile Liu, Xiquan Zhang, Ling Yang, Xin Tian, Tiantian Dong, Charles Z Ding, Lihong Hu, Lingyu Wu, Lele Zhao, Jun Mao, Qusheng Ji, Shaoyu Yan, Zhenzhen Zhu, Yuanfeng Xia, Chichung Chan, Shuhui Chen. Preclinical evaluation of TQB3804, a potent EGFR C797S inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1320.

Abstract 3113: Regulation of TOR complex 1 by the BRAFV600EMutant determines response and development of resistance to MEK inhibition by trametinib in glioma models

Abstract Pediatric Low-Grade glioma (PLGG) is the most common brain tumor in children. Current treatment protocols, particularly those involving high dose radiation therapy are associated with neurocognitive and neuroendocrine dysfunction. Genomic studies have revealed that PLGG are characterized by activation of the MAPK cascade. Recently, the value of selumetinib, an allosteric inhibitor of MEK1/2 has been demonstrated in PLGG. However, drug resistance will inevitably limit the efficacy. Trametinib is a more potent MEK1/2 inhibitor with better brain penetration than selumetinib. Here we have attempted to identify the mechanism/s of the resistance to trametinib that PLGG developes, and to explore combination treatments that may retard or prevent emergence of trametinib resistance in animal models. In BT-40 (childhood anaplastic astrocytoma with BRAFV600E mutation) xenografts, trametinib caused complete tumor regressions, followed by tumor regrowth at the end of treatment. Trametinib treatment rapidly induced pSTAT3(Y705), that was blocked by the JAK1/2 inhibitor, ruxolitinib. Agaist BT-40 xenografts, ruxolitinib slightly enhanced the antitumor response to trametinib. The combination of trametinib with rapamycin was more active in each xenograft line than either single agent alone and in both subcutaneous and intracranial BT-40 models. In BT-40 xenografts, resistance to trametinib was consistently induced within 3 or 4 6-week cycles of treatment similar to that for the trametinib + ruxolitinib combination. In contrast, resistance to combined trametinib and rapamycin was not developed. Rapamycin prevented emergence of trametinib resistance, but did not reverse resistance to trametinib, once acquired. Inhibition of MAPK signaling by trametinib was similar in parental and trametinib-resistant BT-40 xenografts, however, trametinib reistant tumor cells failed to undergo apoptosis. Cells freshly isolated from trametinib resistant BT-40 xenografts had a higher apoptotic threshhold, whereas cells isolated from BT-40 xenografts after 3 cycles of trametinib + rapamycin, remained equally sensitive to parental BT-40 cells, as determined by BH3 profiling. This study reveals a potential new therapeutic use of rapamycin, preventing emergence of resistance to trametinib. Potentially, addition of rapamycin to MEK inhibitor therapy children with BRAF-driven low-grade glioma may be of value. Citation Format: Fuyang Li. Regulation of TOR complex 1 by the BRAFV600EMutant determines response and development of resistance to MEK inhibition by trametinib in glioma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3113.

Abstract 5264: Metabolic reprogramming with β-alanine to overcome chemotherapy resistance in pancreatic cancer

Abstract Background: Increased aerobic glycolysis (Warburg effect) leading to acidic microenvironment confers chemoresistance to weakly basic Gemcitabine, the standard treatment in Pancreatic ductal adenocarcinoma (PDAC). Metabolomic perturbations in two PDAC cell lines having differential sensitivity to Gemcitabine was investigated by profiling over 40 metabolites using 1H-NMR spectroscopy. Notably, a significant decrease in the concentration of β-alanine (βA) was observed in Gem resistant compared to Gem sensitive cell line, suggesting βA may have a role in chemotherapy response. We aimed to evaluate the role of βA supplementation in improving Gem efficacy in Gem resistant cell lines Methods: PDAC Panc-1 cell line extracts treated with Gem with and without βA supplementation were analysed via 1H-NMR spectroscopy. Aerobic glycolysis was quantified by measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) using the Seahorse XF analyser platform. Global mRNA profiling was done by Next Generation Sequencing. Proliferation, migration and cell cycle analysis was measured by Xcelligence real time cell analysis system and flow cytometry, respectively. PANC-1 and BxPC-3 tumor xenografts treated with Gemcitabine with and without βA for 4 weeks and the tumor volumes and weights were measured. Results: βA supplementation in Gem resistant cells results in: (1) decreased basal glycolytic rate, proton leak and ATP production; (2) increased pyruvate, decreased lactic acid and NAD+ concentrations with decreased LDH-A transcription; also increased carnosine levels with a more basic pH in the conditioned media; (3) enhanced sensitivity to Gem treatment, with a significant reduction in proliferation, cell migration, and increased apoptosis and relative hENt-1 mRNA levels and (5) xenograft tumor volumes and weights were significantly reduced upon βA supplementation. Conclusion: βA supplementation reprograms cell metabolism by normalizing energy production and reducing microenvironment acidification, thus enhancing chemo-sensitivity in Gem resistant PDAC cells and xenografts. βA can be potentially used as a co-therapeutic in PDAC. Note: This abstract was not presented at the meeting. Citation Format: Danny Yakoub, Smitha T. Totiger, Alexandra Moran, Sujit Suwal, Julio Pimentel, Lauren O'Donell, Jamie Walls, Nagaraj Nagathihalli, Nipun Merchant. Metabolic reprogramming with β-alanine to overcome chemotherapy resistance in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5264.

Enzyme-mediated depletion of l-cyst(e)ine synergizes with thioredoxin reductase inhibition for suppression of pancreatic tumor growth

Perturbing redox homeostasis potentially constitutes a selective cancer-killing strategy. An engineered human enzyme, cyst(e)inase that degrades extracellular cysteine (l-Cys) and cystine (CSSC) leading to depletion of intracellular l-Cys and glutathione (GSH) was evaluated for its effects on pancreatic cancer cell lines. Cyst(e)inase caused oxidative stress and apoptosis in only Panc1 cells, whereas MIA-PaCa2 and BxPC3 cells demonstrated survival under conditions of cyst(e)inase-mediated l-Cys depletion through maintenance of mitochondrial metabolism and lower levels of reactive oxygen species (ROS). A correlation was also observed between thioredoxin 1 protein levels and resistance to cyst(e)inase treatment. Notably, cyst(e)inase in combination with auranofin, a thioredoxin reductase inhibitor, caused a synergistic increase in mitochondrial ROS and apoptosis and inhibition of mitophagy in the more resistant cells. In addition, auranofin treatment sensitized the more resistant pancreatic cancer xenografts to cyst(e)inase without systemic toxicity. These data provide strong rationale to further investigate therapeutic strategies that target multiple antioxidant pathways for treatment of pancreatic ductal adenocarcinoma.

Combined Targeting of Estrogen Receptor Alpha and XPO1 Prevent Akt Activation, Remodel Metabolic Pathways and Induce Autophagy to Overcome Tamoxifen Resistance.

A majority of breast cancer specific deaths in women with ERα (+) tumors occur due to metastases that are resistant to endocrine therapy. 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 the nuclear transport protein XPO1 in overcoming endocrine resistance. Selinexor (SEL), an XPO1 antagonist, has been evaluated in multiple late stage clinical trials in patients with relapsed and/or refractory hematological and solid tumor malignancies. Our transcriptomics analysis showed that 4-Hydroxytamoxifen (4-OHT), SEL alone or their combination induced differential Akt signaling- and metabolism-associated gene expression profiles. Western blot analysis in endocrine resistant cell lines and xenograft models validated differential Akt phosphorylation. Using the Seahorse metabolic profiler, we showed that ERα-XPO1 targeting changed the metabolic phenotype of TAM-resistant breast cancer cells from an energetic to a quiescent profile. This finding demonstrated that combined targeting of XPO1 and ERα rewired the metabolic pathways and shut down both glycolytic and mitochondrial pathways that would eventually lead to autophagy. Remodeling metabolic pathways to regenerate new vulnerabilities in endocrine resistant breast tumors is novel, and given the need for better strategies to improve therapy response in relapsed ERα (+) tumors, our findings show great promise for uncovering the role that ERα-XPO1 crosstalk plays in reducing cancer recurrences.

Improved in vivo targeting of BCL-2 phenotypic conversion through hollow gold nanoshell delivery.

Although new cancer therapeutics are discovered at a rapid pace, lack of effective means of delivery and cancer chemoresistance thwart many of the promising therapeutics. We demonstrate a method that confronts both of these issues with the light-activated delivery of a Bcl-2 functional converting peptide, NuBCP-9, using hollow gold nanoshells. This approach has shown not only to increase the efficacy of the peptide 30-fold in vitro but also has shown to reduce paclitaxel resistant H460 lung xenograft tumor growth by 56.4%.

Abstract P5-04-23: Enhancing the activity of a novel estrogen receptor coregulator binding modulator (ERX-11) against ER-positive therapy resistant breast cancer

Abstract Background:We had previously reported a novel small molecule, ERX-11, that directly interacts with ER and blocks the interaction between a subset of coregulators with both native and mutant forms of ER. ERX-11 effectively blocks ER oncogenic signaling and has potent anti-proliferative activity against therapy-sensitive and therapy-resistant human breast cancer cells. To enhance the clinical translation of ERX-11, we sought to pursue both lead optimization and evaluate combinations of ERX-11 with other approved agents in breast cancer. Methods: We designed, synthesized and tested 500 derivatives of ERX-11 in multiple models of ER+ breast cancer. We also tested combinations of ERX-11 with multiple agents, including other ER targeting agents, chemotherapies and CDK4/6 inhibitors. We tested the effect of combination therapy using breast cancer cells with acquired resistance (Tamoxifen, Letrozole, Ribociclib resistant) and engineered models that express ER mutations. In vitro activity was tested using Cell titer glo, MTT, and apoptosis assays. Mechanistic studies were conducted using Western blot, reporter gene assays and RNA-seq analysis. Xenograft, patient derived xenograft (PDX), patient derived explant (PDE) and xenograft derived explant (XDE) models were used for preclinical evaluation and toxicity. Result: Evaluation of 500 analogs of ERX-11 identified a number of leads with differential activity against ER+ and ER- breast cancer cells, identified several analogs including ERX-144, 208, 296, 315 with nanomolar potency against ER+ and therapy-resistant ER+ breast cancers. Validation of the mechanism of action of these analogs is ongoing. The combination of ERX-11 and palbociclib significantly blocked ER-mediated and ER-coregulators mediated oncogenic signaling and showed potent anti-proliferative activity against both endocrine therapy-sensitive and resistant breast cancer cells. In addition, ERX-11 inhibited ribociclib-resistant ER+ cell proliferation in a dose dependent manner. Mechanistic studies using IP-Mass spectrometry demonstrated that ERX-11 and palbociclib blocks the interaction between larger subset of coregulators with ER in therapy resistant breast cancer models. ERX-11 and palbociclib both exhibited potent anti-proliferative activity against therapy-sensitive and therapy-resistant ER+ve breast cancer cells, in xenograft models and in PDEs. Importantly, combination therapy of ERX-11 and palbociclib synergistically reduced the growth of tamoxifen and letrozole resistant xenograft tumors compared to either drug alone. Mass spec based DIA analyses and RNA-seq studies revealed that combinational treatment uniquely activated p53, unfolded response mediated apoptotic pathways, altered DNA damage response and suppressed E2F and Myc target genes. Biochemical studies confirmed combination therapy significantly altered E2F1, ER and DNA damage response pathways. Conclusion: We have successfully pursued two avenues to improving ERX-11 for clinical translation. We have developed ERX-11 analogs with higher potency against ER+ breast cancer. We have shown that combinational treatment with ERX-11 and palbociclib may overcome endocrine therapy resistance and CDK4/6 inhibitor (ribociclib) resistance. Citation Format: Viswanadhapalli S, Ma S, Lee T-K, Sareddy GR, Liu X, Ekoue D, Alluri A, Luo Y, Kassees K, Arteaga C, Alluri P, Weintraub SE, Tekmal RR, Ahn J-M, Raj GV, Vadlamudi RK. Enhancing the activity of a novel estrogen receptor coregulator binding modulator (ERX-11) against ER-positive therapy resistant breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-23.

The microRNA miR-181c enhances chemosensitivity and reduces chemoresistance in breast cancer cells via down-regulating osteopontin

Acquired resistance to chemotherapy is a frequent challenge in cancer care and one of the leading causes for failing breast cancer therapies. There is accumulative clinical and experimental evidence indicating that microRNAs (miRNAs) play a crucial role in developing therapeutic resistance in cancer cells. We aimed to explore key miRNAs and associated mechanisms by which breast cancer develops chemoresistance. In this study, we found that a particular miRNA species, miR-181c, was significantly low-expressed in breast cancer cell line MCF-7 which developed chemoresistance towards doxorubicin (Adriamycin, ADR, subclone renamed as MCF-7/ADR) than in the wild-type MCF-7 cells. Induced overexpression of miR-181c significantly inhibited cell proliferation, reversed the chemoresistance towards doxorubicin, and reduced the growth of resistant breast cancer xenograft tumors in vitro and in vivo. Using a bioinformatics approach, we also identified osteopontin (OPN) as a direct target of miR-181c. In contrast to low miR-181c expression in MCF-7/ADR cells, OPN showed a reversely high expression in resistant MCF-7/ADR cells. Our results suggest that miR-181c may regulate chemosensitivity and chemoresistance by downregulating OPN, resulting in enhanced p53-dependent transactivation and apoptosis in resistant breast cancer cells. This study provides new insights to develop effective interventions for cancer patients with acquired resistance to chemotherapy.

Phase 1 Study of MDR1 Inhibitor Plus Brentuximab Vedotin in Relapsed/Refractory Hodgkin Lymphoma

Phase 1 Study of MDR1 Inhibitor Plus Brentuximab Vedotin in Relapsed/Refractory Hodgkin Lymphoma

Glutathione-Responsive Prodrug Nanoparticles for Effective Drug Delivery and Cancer Therapy

Spurred by recent progress in medicinal chemistry, numerous lead compounds have sprung up in the past few years, although the majority are hindered by hydrophobicity, which greatly challenges druggability. In an effort to assess the potential of platinum (Pt) candidates, the nanosizing approach to alter the pharmacology of hydrophobic Pt(IV) prodrugs in discovery and development settings is described. The construction of a self-assembled nanoparticle (NP) platform, composed of amphiphilic lipid-polyethylene glycol (PEG) for effective delivery of Pt(IV) prodrugs capable of resisting thiol-mediated detoxification through a glutathione (GSH)-exhausting effect, offers a promising route to synergistically improving safety and efficacy. After a systematic screening, the optimized NPs (referred to as P6 NPs) exhibited small particle size (99.3 nm), high Pt loading (11.24%), reliable dynamic stability (∼7 days), and rapid redox-triggered release (∼80% in 3 days). Subsequent experiments on cells support the emergence of P6 NPs as a highly effective means of transporting a lethal dose of cargo across cytomembranes through macropinocytosis. Upon reduction by cytoplasmic reductants, particularly GSH, P6 NPs under disintegration released sufficient active Pt(II) metabolites, which covalently bound to target DNA and induced significant apoptosis. The PEGylation endowed P6 NPs with in vivo longevity and tumor specificity, which were essential to successfully inhibiting the growth of cisplatin-sensitive and -resistant xenograft tumors, while effectively alleviating toxic side-effects associated with cisplatin. P6 NPs are, therefore, promising for overcoming the bottleneck in the development of Pt drugs for oncotherapy.

New naphthopyran analogues of LY290181 as potential tumor vascular-disrupting agents

A series of 19 analogues of the antiproliferative naphthopyran LY290181 were prepared for structure–activity relationship studies. We found the best activities for test compounds bearing small substituents at the meta position of the phenyl ring. The mode of action of LY290181 and eight new analogues was studied in detail. The compounds were highly anti-proliferative with IC50 values in the sub-nanomolar to triple-digit nanomolar range. The new analogues led to G2/M arrest due to interruption of the microtubule dynamics. In 518A2 melanoma cells they caused a mitotic catastrophe which eventually led to apoptosis. The naphthopyrans also induced a disruption of the vasculature in the chorioallantoic membrane (CAM) of fertilized chicken eggs as well as in xenograft tumors in mice. In a preliminary therapy trial, the difluoro derivative 2b retarded the growth of resistant xenograft tumors in mice.