Abstract 4760: KDM4A promotes NEPC progression through regulation of MYC expression

Despite advancements in treatment, prostate cancer (PCa) remains the second leading cause of death among men. Neuroendocrine prostate cancer (NEPC) represents one of the most lethal forms of PCa and lacks life-prolonging treatment. Here we identified histone lysine demethylase KDM4A as a driver in NEPC progression and an effective therapeutic target. KDM4A mRNA and protein are overexpressed in human and mouse NEPC compared to adenocarcinoma. Knockdown or knockout of KDM4A in NEPC cell lines suppressed cancer cell growth in vitro and in vivo. Importantly, the inactivation of Kdm4a in a genetically engineered mouse model of prostate cancer reduces tumor burden, reduces the incidence of NEPC, and prolongs overall survival. Mechanistically, KDM4A directly regulates the transcription of MYC, which is hyper-activated in human and mouse NEPC. Furthermore, a potent pan-KDM4 inhibitor QC6352 significantly reduces NEPC cell growth in vitro and in vivo. Taken together, we demonstrate that KDM4A promotes NEPC progression through regulation of MYC expression and targeting KDM4A can be an effective therapeutic strategy for NEPC.

Citation Format: Celia Sze Ling Mak, Ming Zhu, Xin Liang, Feng Wang, Anh G. Hoang, Xinzhi Song, Peter Shepherd, Derek Liang, Jessica Suh, Jiwon Park, Miao Zhang, Eric Metzger, Roland Schule, Abhinav K. Jain, Ellen Karasik, Barbara A. Foster, Min Gyu Lee, Paul Corn, Christopher J. Logothetis, Ana Aparicio, Nora Navone, Patricia Troncoso, Jianhua Zhang, Sue-Hwa Lin, Guocan Wang. KDM4A promotes NEPC progression through regulation of MYC expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4760.

Abstract 5788: Single-cell and spatial transcriptomic mapping of human renal cell carcinoma brain metastases uncovers actionable immune-resistance targets

Introduction: The discovery of immune checkpoint inhibitors has revolutionized metastatic renal cell carcinoma (RCC) treatment. However, in patients with RCC brain metastases, response rates are low and survival outcomes poor. To understand the tumor microenvironmental differences between primary kidney tumors, extracranial metastases, and brain metastases, we developed a detailed single-cell atlas of RCC brain metastases along with their matched extracranial and primary tumors.

Methods: We performed single-nucleus RNA-seq on 27 samples (nearly 200,000 cells) from RCC patients; samples included 14 brain metastases, 8 matched primary kidney tumors, and 5 matched extracranial metastases. We performed multiplex IHC to validate selected transcriptomic findings. We used Nanostring CosMx 960-plex RNA spatial molecular imaging technique on selected samples to validate cellular interactions in a spatial context.

Results: We established a multi-tissue single-cell atlas of RCC brain metastases by identifying 9 major and 37 minor malignant, immune, and stromal cell clusters. Brain metastases had higher neuronal and glial cells interacting with immune and tumor cells. Brain metastasis tumor cells were also transcriptomically reprogrammed to adapt to the brain microenvironment through enrichment of MYC targets, MTORC1 signaling, epithelial-mesenchymal transition, fatty-acid metabolism, oxidative phosphorylation, and reactive oxygen species pathways. Moreover, cell-to-cell communication and downstream target gene expression analyses showed that brain metastasis tumor cells expressed ligands and receptors that induce tumor cell proliferation in both autocrine and paracrine fashions. Among T-cell populations, we found fewer proliferating cytotoxic T lymphocytes in the brain than in other sites. Moreover, T cells in brain metastases expressed higher levels of several targetable inhibitory checkpoints than did extracranial metastases. In addition, we found that naïve/memory T cells in brain metastases were a favorable prognostic marker for overall survival after craniotomy. Our characterization of myeloid cell populations across the 3 disease sites found fewer dendritic cells and monocytes in the brain compared to other sites. Macrophages in brain metastases more highly expressed an M2 immunosuppressive gene signature than did those in primary RCC tumors.

Conclusion: Our findings from the largest single-cell atlas of RCC brain metastases with matched primary and extracranial metastases suggest several unique targetable, immunosuppressive biological mechanisms in the brain microenvironment. These results provide a foundation for a deeper understanding of RCC brain metastasis biology and can serve as a resource for the scientific community to further explore therapeutically targetable tumor and immune-related mechanisms.

Citation Format: Elshad Hasanov, Truong Nguyen Anh Lam, Jerome Lin, Patrick K. Reville, Merve Hasanov, Anna K. Casasent, David Shih, Sahin Hanalioglu, Mehmet Asim Bilen, Omar Alhalabi, Berrin Babaoglu, Baylar Baylarov, Adeboye O. Osunkoya, Lisa M. Norberg, Joy Gumin, Tuan M. Tran, Jianzhuo Li, Anh G. Hoang, Haidee D. Chancoco, Brittany C. Parker Kerrigan, Erika J. Thompson, Betty YS Kim, Dima Suki, Melike Mut, Figen Soylemezoglu, Giannicola Genovese, Kadir C. Akdemir, Hussain A. Tawbi, Nizar M. Tannir, Florencia McAllister, Michael A. Davies, Padmanee Sharma, Jason Huse, Frederick Lang, Nicholas Navin, Eric Jonasch. Single-cell and spatial transcriptomic mapping of human renal cell carcinoma brain metastases uncovers actionable immune-resistance targets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5788.

MTAP deficiency creates an exploitable target for antifolate therapy in 9p21-loss cancers

Methylthioadenosine phosphorylase, an essential enzyme for the adenine salvage pathway, is often deficient (MTAPdef) in tumors with 9p21 loss and hypothetically renders tumors susceptible to synthetic lethality by antifolates targeting de novo purine synthesis. Here we report our single arm phase II trial (NCT02693717) that assesses pemetrexed in MTAPdef urothelial carcinoma (UC) with the primary endpoint of overall response rate (ORR). Three of 7 enrolled MTAPdef patients show response to pemetrexed (ORR 43%). Furthermore, a historic cohort shows 4 of 4 MTAPdef patients respond to pemetrexed as compared to 1 of 10 MTAP-proficient patients. In vitro and in vivo preclinical data using UC cell lines demonstrate increased sensitivity to pemetrexed by inducing DNA damage, and distorting nucleotide pools. In addition, MTAP-knockdown increases sensitivity to pemetrexed. Furthermore, in a lung adenocarcinoma retrospective cohort (N = 72) from the published BATTLE2 clinical trial (NCT01248247), MTAPdef associates with an improved response rate to pemetrexed. Our data demonstrate a synthetic lethal interaction between MTAPdef and de novo purine inhibition, which represents a promising therapeutic strategy for larger prospective trials.

Prostate cancer castrate resistant progression usage of non-canonical androgen receptor signaling and ketone body fuel

Prostate cancer (PCa) that progresses after androgen deprivation therapy (ADT) remains incurable. The underlying mechanisms that account for the ultimate emergence of resistance to ADT, progressing to castrate-resistant prostate cancer (CRPC), include those that reactivate androgen receptor (AR), or those that are entirely independent or cooperate with androgen signaling to underlie PCa progression. The intricacy of metabolic pathways associated with PCa progression spurred us to develop a metabolism-centric analysis to assess the metabolic shift occurring in PCa that progresses with low AR expression. We used PCa patient-derived xenografts (PDXs) to assess the metabolic changes after castration of tumor-bearing mice and subsequently confirmed main findings in human donor tumor that progressed after ADT. We found that relapsed tumors had a significant increase in fatty acids and ketone body (KB) content compared with baseline. We confirmed that critical ketolytic enzymes (ACAT1, OXCT1, BDH1) were dysregulated after castrate-resistant progression. Further, these enzymes are increased in the human donor tissue after progressing to ADT. In an in silico approach, increased ACAT1, OXCT1, BDH1 expression was also observed for a subset of PCa patients that relapsed with low AR and ERG (ETS-related gene) expression. Further, expression of these factors was also associated with decreased time to biochemical relapse and decreased progression-free survival. Our studies reveal the key metabolites fueling castration resistant progression in the context of a partial or complete loss of AR dependence.

Abstract 385: MTAP gene deficiency creates vulnerability to anti-folate therapy in urothelial bladder carcinoma

Background: The methylthioadenosine phosphorylase (MTAP) gene encodes an essential enzyme for the salvage pathway of adenosine synthesis and is frequently lost in different types of cancer including urothelial bladder carcinoma. Therefore, MTAP-deficient tumors are theoretically very sensitive to anti-folate agents such as pemetrexed that can effectively block the de novo pathway of adenosine synthesis and as a result, create a state of synthetic lethality. We thus hypothesize that tumor MTAP gene deficiency is associated with response to pemetrexed therapy in bladder cancer.

Methods: In this study, we investigated MTAP gene deficiency rates in the TCGA database and confirmed MTAP protein loss by immunohistochemistry using a tumor tissue microarray containing bladder tumor tissues from 151 patients. We then performed in vitro and in vivo studies using MTAP-proficient and MTAP-deficient human bladder cancer cell lines. Functional loss of MTAP was verified with mass spectrometry, which detects its substrate methylthioadenosine (MTA) levels. We also correlated these pre-clinical studies with clinical response data on patients with metastatic bladder cancer treated with pemetrexed.

Results: We identified that 27.8% bladder cancer patients have MTAP protein deficiency, which is consistent with exome sequencing data from the TCGA database. In vitro data showed MTAP-deficient human bladder cancer cell lines were significantly more sensitive to pemetrexed, with IC50 at least 40 times lower than MTAP-proficient cell lines. Subsequent knockdown of the MTAP gene in MTAP-proficient cell lines increased sensitivities to pemetrexed treatment. Consistent with the in vitro data, pemetrexed significantly inhibited the growth of MTAP-deficient or knockdown xenograft tumors but not MTAP-proficient tumors. Furthermore, 4 of 4 (100%) patients with MTAP-deficient metastatic bladder cancer responded to pemetrexed treatment, whereas only 1 of 11 (9%) patients with MTAP-proficient metastatic bladder cancer responded to pemetrexed.

Conclusion: Our data demonstrate that MTAP gene loss in urothelial bladder cancer leads to a metabolic state of synthetic lethality with pemetrexed therapy. Therefore, bladder tumor MTAP loss should be further investigated as a potential biomarker for selection of patients for anti-folate therapy.

Citation Format: Jianfeng Chen, Omar Alhalabi, Guangchun Han, Wei-Lien Wang, Xin-Qiao Zhang, Jian H. Song, Lidia P. Lopez, Sumankalai Ramachandran, Anh G. Hoang, Tyrone Garnett, Matthew Campbell, Amishi Y. Shah, Jennifer Wang, Arlene O. Siefker-Radtke, Shi-Ming Tu, Mark Titus, Charles C. Guo, Gary E. Gallick, Eleni Efstathiou, William F. Benedict, Christopher J. Logothetis, Thai H. Ho, Linghua Wang, Jianjun Gao. MTAP gene deficiency creates vulnerability to anti-folate therapy in urothelial bladder carcinoma [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 385.

B7-H3 Expression in Merkel Cell Carcinoma-Associated Endothelial Cells Correlates with Locally Aggressive Primary Tumor Features and Increased Vascular Density

PURPOSE

Merkel cell carcinoma (MCC) is an aggressive cutaneous malignancy whose pathogenesis and prognosis are related to the integrity of the host immune system. Despite promising clinical responses to immune-checkpoint blockade, response and resistance remain unpredictable, underscoring a critical need to delineate novel prognostic biomarkers and/or therapeutic targets for this disease.Experimental Design: Expression of immune-regulatory markers (PD-L2, B7-H3, B7-H4, IDO-1, ICOS, TIM3, LAG3, VISTA, and OX-40) was assessed using singlet chromogenic IHC in 10 primary MCCs. Multiplex immunofluorescence quantified CD31 and B7-H3 expression in 52 primary and 25 metastatic MCCs. B7-H3 and CD31 expressions were tabulated as a series of independent (X,Y) cell centroids. A spatial G-function, calculated based on the distribution of distances of B7-H3+ (X,Y) cell centroids around the CD31⁺ (X,Y) cell centroids, was used to estimate a colocalization index equivalent to the percentage of CD31-positive cell centroids that overlap with a B7-H3-positive cell centroid.

RESULTS

Primary and metastatic MCCs exhibit a dynamic range of colocalized CD31 and B7-H3 expression. Increasing colocalized expression of B7-H3 with CD31 significantly associated with increased tumor size (P = 0.0060), greater depth of invasion (P = 0.0110), presence of lymphovascular invasion (P = 0.0453), and invasion beyond skin (P = 0.0428) in primary MCC. Consistent with these findings, increasing colocalized expression of B7-H3 and CD31 correlated with increasing vascular density in primary MCC, but not metastatic MCC.

CONCLUSIONS

Our results demonstrate that colocalized expression of B7-H3/CD31 is a poor prognostic indicator and suggest therapies targeting B7-H3 may represent an effective approach to augmenting immune-activating therapies for MCC.

Integrating Murine and Clinical Trials with Cabozantinib to Understand Roles of MET and VEGFR2 as Targets for Growth Inhibition of Prostate Cancer

PURPOSE

We performed parallel investigations in cabozantinib-treated patients in a phase II trial and simultaneously in patient-derived xenograft (PDX) models to better understand the roles of MET and VEGFR2 as targets for prostate cancer therapy.

EXPERIMENTAL DESIGN

In the clinical trial, radiographic imaging and serum markers were examined, as well as molecular markers in tumors from bone biopsies. In mice harboring PDX intrafemurally or subcutaneously, cabozantinib effects on tumor growth, MET, PDX in which MET was silenced, VEGFR2, bone turnover, angiogenesis, and resistance were examined.

RESULTS

In responsive patients and PDX, islets of viable pMET-positive tumor cells persisted, which rapidly regrew after drug withdrawal. Knockdown of MET in PDX did not affect tumor growth in mice nor did it affect cabozantinib-induced growth inhibition but did lead to induction of FGFR1. Inhibition of VEGFR2 and MET in endothelial cells reduced the vasculature, leading to necrosis. However, each islet of viable cells surrounded a VEGFR2-negative vessel. Reduction of bone turnover was observed in both cohorts.

CONCLUSIONS

Our studies demonstrate that MET in tumor cells is not a persistent therapeutic target for metastatic castrate-resistant prostate cancer (CRPC), but inhibition of VEGFR2 and MET in endothelial cells and direct effects on osteoblasts are responsible for cabozantinib-induced tumor inhibition. However, vascular heterogeneity represents one source of primary therapy resistance, whereas induction of FGFR1 in tumor cells suggests a potential mechanism of acquired resistance. Thus, integrated cross-species investigations demonstrate the power of combining preclinical models with clinical trials to understand mechanisms of activity and resistance of investigational agents.

Targeting the interleukin-11 receptor α in metastatic prostate cancer: A first-in-man study

BACKGROUND

Receptors in tumor blood vessels are attractive targets for ligand-directed drug discovery and development. The authors have worked systematically to map human endothelial receptors (“vascular zip codes”) within tumors through direct peptide library selection in cancer patients. Previously, they selected a ligand-binding motif to the interleukin-11 receptor alpha (IL-11Rα) in the human vasculature.

METHODS

The authors generated a ligand-directed, peptidomimetic drug (bone metastasis-targeting peptidomimetic-11 [BMTP-11]) for IL-11Rα–based human tumor vascular targeting. Preclinical studies (efficacy/toxicity) included evaluating BMTP-11 in prostate cancer xenograft models, drug localization, targeted apoptotic effects, pharmacokinetic/pharmacodynamic analyses, and dose-range determination, including formal (good laboratory practice) toxicity across rodent and nonhuman primate species. The initial BMTP-11 clinical development also is reported based on a single-institution, open-label, first-in-class, first-in-man trial (National Clinical Trials number NCT00872157) in patients with metastatic, castrate-resistant prostate cancer.

RESULTS

BMTP-11 was preclinically promising and, thus, was chosen for clinical development in patients. Limited numbers of patients who had castrate-resistant prostate cancer with osteoblastic bone metastases were enrolled into a phase 0 trial with biology-driven endpoints. The authors demonstrated biopsy-verified localization of BMTP-11 to tumors in the bone marrow and drug-induced apoptosis in all patients. Moreover, the maximum tolerated dose was identified on a weekly schedule (20-30 mg/m²). Finally, a renal dose-limiting toxicity was determined, namely, dose-dependent, reversible nephrotoxicity with proteinuria and casts involving increased serum creatinine.

CONCLUSIONS

These biologic endpoints establish BMTP-11 as a targeted drug candidate in metastatic, castrate-resistant prostate cancer. Within a larger discovery context, the current findings indicate that functional tumor vascular ligand-receptor targeting systems may be identified through direct combinatorial selection of peptide libraries in cancer patients. Cancer 2015;121:2411–2421. © 2015 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.

The authors report on the development of a new ligand-directed peptidomimetic (termed bone metastasis-targeting peptidomimetic-11) for interleukin-11 receptor-based human vascular targeting, including the translation from preclinical studies to a first-in-class, first-in-man clinical trial in patients with metastatic, castrate-resistant prostate cancer.

Cadherin-11 in renal cell carcinoma bone metastasis

Bone is one of the common sites of metastases from renal cell carcinoma (RCC), however the mechanism by which RCC preferentially metastasize to bone is poorly understood. Homing/retention of RCC cells to bone and subsequent proliferation are necessary steps for RCC cells to colonize bone. To explore possible mechanisms by which these processes occur, we used an in vivo metastasis model in which 786-O RCC cells were injected into SCID mice intracardially, and organotropic cell lines from bone, liver, and lymph node were selected. The expression of molecules affecting cell adhesion, angiogenesis, and osteolysis were then examined in these selected cells. Cadherin-11, a mesenchymal cadherin mainly expressed in osteoblasts, was significantly increased on the cell surface in bone metastasis-derived 786-O cells (Bo-786-O) compared to parental, liver, or lymph node-derived cells. In contrast, the homing receptor CXCR4 was equivalently expressed in cells derived from all organs. No significant difference was observed in the expression of angiogenic factors, including HIF-1α, VEGF, angiopoeitin-1, Tie2, c-MET, and osteolytic factors, including PTHrP, IL-6 and RANKL. While the parental and Bo-786-O cells have similar proliferation rates, Bo-786-O cells showed an increase in migration compared to the parental 786-O cells. Knockdown of Cadherin-11 using shRNA reduced the rate of migration in Bo-786-O cells, suggesting that Cadherin-11 contributes to the increased migration observed in bone-derived cells. Immunohistochemical analysis of cadherin-11 expression in a human renal carcinoma tissue array showed that the number of human specimens with positive cadherin-11 activity was significantly higher in tumors that metastasized to bone than that in primary tumors. Together, these results suggest that Cadherin-11 may play a role in RCC bone metastasis.