Abstract B092: Mechanisms of PARP7 inhibition-induced tumor cell death: A novel therapeutic for non-small cell lung cancer with tumor-intrinsic and immune-dependent pathways
Authors: Coleman Nalani J. , Lee Ji-Ann , Dumitras Camelia , Gusain Gauri , Conklin Dylan , Palazzolo Michael , Kahangi Bitta P. , Rennels Austin K. , Abascal Jensen , Crosson William P. , Oh Michael S. , Reyes Edgar Perez , Botero Carlos , Jiang Hong , Lavalle Alvaro Chumpitaz , Tappuni Shahed , Aslanian Emily Melik , Deng Jie , Salehi-Rad Ramin , Tran Linh M. , Krysan Kostyantyn , Liu Bin , Dubinett Steven M. 
Published: February 2025

Abstract
Poly-adenosine diphosphate (ADP)-ribose polymerase 7 (PARP7) is an enzyme that postranslationally modifies target proteins with an ADP-ribose group, which is required for multiple cellular processes, including DNA repair, immune function, and cellular metabolism. Recent studies have identified a subset of non-small cell lung cancer (NSCLC) exhibiting cancer dependency to PARP7, suggesting that PARP7 may be a therapeutic target for NSCLC. In addition, PARP7 was recently identified as an immune evasion mechanism for cancer cells to escape immune surveillance by dampening the type I interferon (IFN) response to nucleic acid sensors. Targeted inhibition of PARP7 by a small molecule inhibitor, RBN-2397, restored type I IFN signaling to nucleic acid sensing signals, inducing both tumor intrinsic cell death and immune activation that together led to tumor regression. However, the specific signaling mediators of PARP7 inhibition (PARP7i)-mediated tumor cell death and host immune activation remain unknown. In addition, because PARP7 dependency in NSCLC is not driven by genomic mutations, biomarkers of sensitivity/resistance to PARP7 have not been identified. Thus, there is a critical demand for mechanistic studies of PARP7i and biomarker identification of PARP7 sensitivity for patient stratification of future trials. To identify the mechanistic signaling mediators involved in tumor regression mediated by PARP7i, we performed a single cell RNA-sequencing assay on PARP7 sensitive and resistant NSCLC cell lines treated with RBN-2397, and identified top 10 candidate differentially expressed genes (DEGs) that may play a role in the PARP7i-induced killing of tumor cells. We established single gene knockouts (KO) of the top 3 genes in a NSCLC sensitive cell line using the CRISPR-Cas9 technology to determine the functional role of these DEGs in PARP7i-induced tumor intrinsic cytotoxicity. Preliminary data suggests there are multiple pathways involved in PARP7i-mediated tumor cell death. In parallel, we designed a CRISPR pool library KO screen to probe hundreds of candidate signaling molecules using an enrichment-based assay. To identify potential biomarkers of PARP7 dependency in human NSCLC patients, we assessed PARP7 dependency of primary tumor surgical resections from NSCLC patients in both 2D cell culture and 3D Patient Derived Organoids (PDOs) using an optimized drug dose response proliferation assay. We will further probe for molecular and genetic differences between PARP7 dependent vs independent phenotypes to identify potential biomarkers for PARP7 dependency. These studies will elucidate the signaling mediators and uncover new mechanisms by which PARP7i leads to anti-tumor effect via both tumor-intrinsic and immune regulatory pathways, and identify potential biomarkers of PARP7 dependency that will facilitate effective patient stratification for future trials evaluating PARP7 inhibitors as a potential therapy for NSCLC.
Citation Format: Nalani J. Coleman, Ji-Ann Lee, Camelia Dumitras, Gauri Gusain, Dylan Conklin, Michael Palazzolo, Bitta P. Kahangi, Austin K. Rennels, Jensen Abascal, William P. Crosson, Michael S. Oh, Edgar Perez Reyes, Carlos Botero, Hong Jiang, Alvaro Chumpitaz Lavalle, Shahed Tappuni, Emily Melik Aslanian, Jie Deng, Ramin Salehi-Rad, Linh M. Tran, Kostyantyn Krysan, Bin Liu, Steven M. Dubinett. Mechanisms of PARP7 inhibition-induced tumor cell death: A novel therapeutic for non-small cell lung cancer with tumor-intrinsic and immune-dependent pathways [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B092.