Abstract 6130: Cancer sensitivity to therapy is constrained by apoptosis regulation in cells of origin
Authors: Fraser Cameron , Qin Xingping , Shimada Kenichi , Spetz Johan , Florido Mary Heather , Singh Rumani , Yu Stacey , Presser Adam , Inde Zintis , Joshi Gaurav , Guerriero Jennifer , Sanchez-Rivera Francisco , Karst Alison , Lopez Omar , Li Chendi , Winter Peter , Yue Ying , Sorger Peter , Cheng Jingwei , Lossos Izidore , Hata Aaron , Drapkin Ronny , Palmer Adam , Decaprio James , Thakuria Manisha , Yoon Charles , Matulonis Ursula , Meyerson Matthew , Stover Elizabeth , Cardona Diana , Wood Kris , Sarosiek Shayna , Kirsch David , Mancias Joseph , Cherniack Andrew , Letai Anthony , Sarosiek Kristopher 
Published: April 2023

Abstract
Many chemotherapeutic agents target cellular components or processes that are present in all cancers, yet clinical responses to these agents vary greatly between cancer types and even patient age - the basis for these broad-scale differences are unclear. The vast majority of targeted and cytotoxic cancer therapies including ionizing radiation produce pro-apoptotic signaling in exposed cells, suggesting that the mitochondrial apoptosis sensitivity of cancer cells could act as a central signaling “node” to broadly impact therapy outcomes. To test this, we used BH3 profiling and complementary chemosensitivity assays to analyze hundreds of primary cancer specimens across twelve major cancer types. We find that cancers with typically favorable outcomes including certain hematologic malignancies, testicular cancer, and some pediatric cancers contain mitochondria that are highly primed for apoptosis, which renders them hypersensitive to cytotoxic as well as targeted agents and radiation therapy. Priming levels in many epithelial cancers including ovarian cancer and non-small cell lung cancer are highly heterogeneous, mirroring their variability in clinical outcomes. Finally, many tumor types that are typically chemoresistant including adult soft tissue sarcomas, hepatocellular carcinoma and pancreatic cancer are almost completely resistant to pro-apoptotic signaling. By analyzing in vitro and in vivo pancreatic, ovarian, hepatocellular and sarcoma tumorigenesis models, we find that apoptotic priming generally increases during neoplastic transformation, in part due to consistent upregulation of pro-apoptotic proteins BAX and BAK. However, the level of apoptotic priming in cancer cells is constrained by the baseline apoptosis sensitivity of normal cells prior to transformation. Remarkably, we find that apoptotic priming is dynamically regulated by cell lineage and differentiation state but can also be modulated by oncogenes. For instance, Myc activation typically increases apoptotic priming while activation of mutant Ras signaling decreases it - these changes in priming alter the chemosensitivity of cancer cells. Finally, we use inducible mouse tumor models to demonstrate that neoplastic transformation of cells from developmentally immature tissues yields pediatric tumors that are more primed for apoptosis than equivalent tumors arising in adults. This difference in priming causes pediatric tumors to be more sensitive to front-line therapies and BH3 mimetics targeting pro-survival BCL-2 family proteins in vitro and in vivo. Thus, lineage-determined regulation of apoptosis prior to and during neoplastic transformation leads to broad-scale differences in cancer cell chemosensitivity and can be exploited therapeutically by targeting BCL-2 family proteins.
Citation Format: Cameron Fraser, Xingping Qin, Kenichi Shimada, Johan Spetz, Mary Heather Florido, Rumani Singh, Stacey Yu, Adam Presser, Zintis Inde, Gaurav Joshi, Jennifer Guerriero, Francisco Sanchez-Rivera, Alison Karst, Omar Lopez, Chendi Li, Peter Winter, Ying Yue, Peter Sorger, Jingwei Cheng, Izidore Lossos, Aaron Hata, Ronny Drapkin, Adam Palmer, James Decaprio, Manisha Thakuria, Charles Yoon, Ursula Matulonis, Matthew Meyerson, Elizabeth Stover, Diana Cardona, Kris Wood, Shayna Sarosiek, David Kirsch, Joseph Mancias, Andrew Cherniack, Anthony Letai, Kristopher Sarosiek. Cancer sensitivity to therapy is constrained by apoptosis regulation in cells of origin. [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 6130.