Copland, John A.

Bromodomains (BD) are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation of several genes including protooncogene cellular myelocytomatosis (c-Myc). c-Myc is difficult to target directly by agents due to its disordered alpha helical protein structure and predominant nuclear localization. The epigenetic targeting of c-Myc by BD inhibitors is an attractive therapeutic strategy for prostate cancer (PC) associated with increased c-Myc upregulation with advancing disease. MT-1 is a bivalent BD inhibitor that is 100-fold more potent than the first-in-class BD inhibitor JQ1. MT-1 decreased cell viability and causes cell cycle arrest in G0/G1 phase in castration-sensitive and resistant PC cell lines in a dose-dependent fashion. The inhibition of c-Myc function by MT-1 was molecularly corroborated by the de-repression of Protein Kinase D1 (PrKD) and increased phosphorylation of PrKD substrate proteins: threonine 120, serine 11, and serine 216 amino acid residues in β-Catenin, snail, and cell division cycle 25c (CDC25c) proteins, respectively. The treatment of 3D cell cultures derived from three unique clinically annotated heavily pretreated patient-derived PC xenografts (PDX) mice models with increasing doses of MT-1 demonstrated the lowest IC50 in tumors with c-Myc amplification and clinically resistant to Docetaxel, Cabazitaxel, Abiraterone, and Enzalutamide. An intraperitoneal injection of either MT-1 or in combination with 3jc48-3, an inhibitor of obligate heterodimerization with MYC-associated protein X (MAX), in mice implanted with orthotopic PC PDX, decreased tumor growth. This is the first pre-clinical study demonstrating potential utility of MT-1 in the treatment of PC with c-Myc dysregulation.

Abstract Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer. Tyrosine kinase inhibitors (TKIs) are approved as a first-line treatment for unresectable HCC. Lenvatinib and cabozantinib are two of the most used TKIs, but the therapeutic duration is limited due to the development of drug resistance. Therefore, understanding the mechanisms of resistance and combining TKIs with other drugs antagonizing resistance should lead to antitumor synergy, eliminating drug resistance. It turns out that the simultaneous use of TKIs together with an inhibitor of stearoyl-CoA desaturase 1 (SCD1) prevents the development of drug resistance, leading to a durable response. SCD1 is the enzyme responsible for de novo fatty acid (FAs) synthesis, converting saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs). MUFAs are an alternative energy source to glucose, integral to cellular membranes, and prevent endoplasmic reticulum (ER) stress and other signaling pathways. In our laboratory, we developed a novel, highly specific SCD1 inhibitor - SSI-4. We have tested the biological activity of SSI-4 against different HCC cell lines and patient-derived xenografts (PDX) mouse models. Of the twelve tested HCC cell lines, four were highly sensitive to SSI-4 (IC50 1-50 nM). Other cell lines showed moderate or no sensitivity to SSI-4. We tested the concomitant use of SSI-4 with lenvatinib and cabozantinib, tyrosine kinase inhibitors (TKIs) FDA-approved for HCC, in HCC cell lines in vitro and using HCC PDX in vivo mouse models. Our studies showed that the combination of the SCD1 inhibitor with both lenvatinib and cabozantinib showed a highly synergistic effect and no development of drug resistance i.e. durable response versus single TKI therapy. Ongoing mechanistic studies are examining whether known molecular targets of tested TKI’s such as VEGFR1, 2, and 3, PDGFRα, FGFR, KIT, and RET dominate in HCC drug resistance to lenvatinib and cabozantinib, and how the use of SSI-4 overcomes the phenomenon of resistance. Citation Format: Justyna J. Gleba, Aylin Alasonyalilar-Demirer, Matthew L. Pawlush, Ahmet Bilgili, Peyton G. Hickman, Kabir Mody, Lewis R. Roberts, Steven R. Alberts, Mark J. Truty, Tushar C. Patel, Han W. Tun, John A. Copland. Synergistic activity of SCD1 blockade in combination with tyrosine kinase inhibitors lenvatinib and cabozantinib in hepatocellular carcinoma (HCC). [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 5489.

Abstract Bromodomains (BD) are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation of protooncogene cellular myelocytomatosis (c- Myc) and other genes. Because c-Myc cannot be directly targeted by small molecular inhibitors due to disordered alpha helical structure, epigenetic targeting of c-Myc by BD inhibitors is an attractive therapeutic strategy for diseases such as prostate cancer (PC) associated with increased c-Myc upregulation with advancing disease. We studied the efficacy of MT1, a novel bivalent BD inhibitor that is 100-fold more potent than the first in class BD inhibitor JQ1, at inhibiting PC growth. We tested the effect on viability by MT-1 on PC cell lines, 3D spheroids derived from clinically annotated drug resistant patient derived xenografts (PDX), mice PDX models and corroborated the molecular mechanism of MT1 down regulation of Myc leading to downstream Myc-dependent up regulation of Protein Kinase D1 (PrKD) substrate phosphorylation by western blot. MT-1 inhibited growth of PC in castration sensitive (LNCaP) and resistant PC cells (PC-3). MT-1 treatment upregulated PrKD expression and phosphorylation of known PrKD substrates: threonine 120 (Thr-120) residues in beta-catenin and the serine 216 in Cell Division Cycle 25 (CDC25C) in PC-3 cells. Moreover, MT-1 was effective in inhibition of 3D spheroids growth at IC 50 between 0.27-0.92µM in Abiraterone, Enzalutamide, Docetaxel, Cabazitaxel metastatic castrate resistant PCa patient-derived tumor 3D spheroids. Additionally, MT1 was effective in inhibiting the tumor growth in PDX mice model. A combined intra-peritoneal administration of MT-1 with another c-Myc inhibitor (3JC48-3), an obligate c-Myc and MYC-associated protein X (MAX) heterodimerization inhibitor, increased the efficacy of inhibiting the PDX growth in mice. This study provides strong pre-clinical in vitro and in vivo evidence for advancing MT- 1 as a novel c-Myc targeting drug in PC. The MT-1 drug development will likely be highly impactful as c-Myc is dysregulated in three fourths of men with advanced PC. Citation Format: Sanjeev Shukla, Mohammed Al-Toubat, Allison H. Feibus, Ahmed Elshafei, Carlos Riveros, Nathalie Meurice, Justyna Gleba, Jonathan Chardon-Robles, Adam M. Kase, John A. Copland III, Joachim L. Petit, Teruko Osumi, K.C. Balaji. Bromodomain inhibitor: MT1 and its potential role in modulation of prostate cancer progression [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 2475.

Abstract Targetable drivers governing to 5-fluorouracil and cisplatin (5FU+CDDP) resistance remain elusive due to the paucity of physiologically and therapeutically relevant models. Accordingly, we established 5FU+CDDP resistant intestinal subtype GC patient-derived organoid lines. JAK/STAT signaling and its downstream, adenosine deaminases acting on RNA 1 (ADAR1), are shown to be concomitantly upregulated in the resistant lines. ADAR1 was demonstrated to confer chemoresistance and self-renewal in an RNA editing-dependent manner. WES-seq coupled with RNA-seq identified enrichment of hyperedited lipid metabolism genes in the resistant lines. Mechanistically, ADAR1-mediated A-to-I editing on 3’UTR of stearoyl-CoA desaturase (SCD1) increased binding of KH domain-containing, RNA-binding, signal transduction-associated 1 (KHDRBS1), thereby augmenting SCD1 mRNA stability. Consequently, SCD1 facilitates lipid droplet formation to alleviate chemotherapy-induced ER stress and enhances self-renewal through increasing β-catenin expression. Pharmacological inhibition of SCD1 abrogated chemoresistance and tumor-initiating cell frequency. Clinically, high proteomic level of ADAR1 and SCD1, or high SCD1 editing/ADAR1 mRNA signature score predicts a worse prognosis. Together, we unveiled a novel actionable target to circumvent chemoresistance. Citation Format: Jia Jian Loh, Tin Lok Wong, Shixun Lu, Helen HN Yan, Hoi Cheong Siu, Ren Xi, Dessy Chan, Max JF Kam, Lei Zhou, Man Tong, John A. Copland, Leilei Chen, Jingping Yun, Suet Yi Leung, Stephanie Ma. ADAR1-mediated RNA editing of SCD1 links lipid metabolism to gastric cancer drug resistance and self-renewal [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 1755.

Abstract Thyroid cancer is the most common endocrine cancer in the US, and its incidence is rising. Most thyroid cancer deaths are attributed to treatment-refractory, metastatic tumors. Thyroid stimulating hormone receptor (TSRH) expression is largely limited to the thyroid gland and is abundantly expressed on thyroid tumor cells, making TSRH a compelling target for advanced thyroid cancer diagnostics and therapeutics. Therefore, we developed a novel TSHR-targeted chimeric antigen receptor (CAR) T cell therapy to treat aggressive thyroid cancers. TSHR-CAR constructs were cloned into a lentiviral CAR construct containing 4-1BB and CD3ζ. First, we demonstrated potent TSHR-CART antigen-specific anti-tumor activity in vitro. Then, NOD-SCID-γ-/- (NSG) mice were inoculated subcutaneously with TSHR+ tumor cells and randomized by tumor volume to treatment with TSHR-CART cells or control Untransduced T cells (UTD). Treatment with TSHR-CART cells resulted in dose-dependent antitumor activity and prolonged survival. De-differentiated anaplastic thyroid cancers (ATC) downregulate TSHR. Our TSHR immunohistochemistry results corroborated these findings and displayed minimal TSHR protein expression, precluding successful TSHR-CART treatment. We therefore sought to sensitize these tumors with MAPK inhibitors, as a strategy to upregulate TSHR expression in patients with metastatic thyroid cancer. TSHR expression was upregulated in patient-derived xenograft (PDX) ATC models after one week of daily administration of the MAPK inhibitors (p=0.0024). After confirming that MAPK inhibition does not dampen TSHR-CART effector functions, we tested sequential and combination therapy of TSHR-CART with MEK and BRAF inhibition in vivo. NSG mice were engrafted with ATC BRAF-mutant PDX tumors and randomized by tumor volume to daily oral treatment with placebo or trametinib (MEK inhibitor) plus dabrafenib (BRAF inhibitor). One week later, mice received either UTD or TSHR-CART. Mice conditioned with trametinib plus dabrafenib (p=0.0018) and subsequently treated with TSHR-CART showed superior antitumor activity. However, the improved antitumor activity in this setting was transient. We therefore tested the durability of TSHR upregulation following MEK/BRAF inhibition and demonstrated that TSHR upregulation lasts less than 48-72 hours after discontinuation. Finally, we tested the combination of TSHR CART cells with MEK/BRAF inhibitors in ATC BRAF-mutant PDX tumors. Here, combining TSHR-CART cells with MEK/BRAF inhibitors result in durable control of the tumors. Collectively, our findings indicate that MEK/BRAF inhibition of de-differentiated thyroid cancers upregulated TSHR expression and enhanced TSHR-CART antitumor activity. This work represents a viable strategy to improve outcomes of patients with aggressive, metastatic thyroid cancers. Citation Format: Claudia Manriquez Roman, Kendall J. Schick, Justyna J. Gleba, Truc N. Huynh, Elizabeth L. Siegler, James L. Miller, Aylin Alasonyalilar Demirer, Matthew L. Pawlush, Ahmet Biligili, Long K. Mai, Erin Tapper, Leo R. Sakemura, Michelle J. Cox, Carli M. Stewart, Ismail Can, Ekene J. Ogbodo, Gaofeng Cui, Georges Mer, Gloria R. Olivier, Yushi Qiu, Robert C. Smallridge, Zubair C. Abba, Han W. Tun, John A. Copland, Saad S. Kenderian. Addition of MAPK inhibitors to prime and sensitize poorly differentiated thyroid cancers as a strategy to improve TSHR-CART cell therapy antitumor activity. [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 5074.

Abstract Purpose: Development of B-cell lymphoma 2 (BCL-2)–specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein–protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575). Experimental Design: Computational modeling was used to design “lead” compounds. Biochemical binding, mitochondrial BH3 profiling, and cell-based viability or apoptosis assays were used to determine the selectivity and potency of BCL-2 inhibitor lisaftoclax. The antitumor effects of lisaftoclax were also evaluated in several xenograft models. Results: Lisaftoclax selectively binds BCL-2 (Ki < 0.1 nmol/L), disrupts BCL-2:BIM complexes, and compromises mitochondrial outer membrane potential, culminating in BAX/BAK-dependent, caspase-mediated apoptosis. Lisaftoclax exerted strong antitumor activity in hematologic cancer cell lines and tumor cells from patients with chronic lymphocytic leukemia, multiple myeloma, or Waldenström macroglobulinemia. After lisaftoclax treatment, prodeath proteins BCL-2‒like protein 11 (BIM) and Noxa increased, and BIM translocated from cytosol to mitochondria. Consistent with these apoptotic activities, lisaftoclax entered malignant cells rapidly, reached plateau in 2 hours, and significantly downregulated mitochondrial respiratory function and ATP production. Furthermore, lisaftoclax inhibited tumor growth in xenograft models, correlating with caspase activation, poly (ADP-ribose) polymerase 1 cleavage, and pharmacokinetics of the compound. Lisaftoclax combined with rituximab or bendamustine/rituximab enhanced antitumor activity in vivo. Conclusions: These findings demonstrate that lisaftoclax is a novel, orally bioavailable BH3 mimetic BCL-2–selective inhibitor with considerable potential for the treatment of certain hematologic malignancies.