Therapeutic mechanisms of targeting WRN in MSI colorectal cancer.

/ABSTRACT Synthetic lethality is a powerful strategy for targeting oncogenic drivers in cancer. Recent studies have shown that colorectal cancer (CRC) cells with microsatellite instability (MSI) rely on Werner (WRN), a RecQ family DNA helicase, for survival. Inhibiting WRN has emerged as a promising approach for treating a significant subset of MSI CRCs that are resistant to standard therapies, including immune checkpoint inhibitor (ICI) therapy. Several highly potent small-molecule WRN inhibitors have been developed and under clinical evaluation. However, the mechanisms by which WRN targeting triggers cell death and elicits a therapeutic response in MSI CRCs remain poorly understood. Our preliminary studies reveal that WRN depletion or inhibition activates the cell death regulator PUMA in MSI CRC cells. Deletion or knockdown of PUMA inhibits cell death and diminishes both in vitro and in vivo therapeutic responses in WRN-targeted MSI CRC cells. Furthermore, we have identified robust immunogenic effects in dying WRN-targeted MSI CRC cells, mediated by extrachromosomal circular DNA (eccDNA) released from these cells. Based on these findings, we propose to test the hypothesis that WRN targeting suppresses MSI CRCs through PUMA-mediated cell death and eccDNA-triggered antitumor immune response. Aim 1. Delineate the mechanisms of cell death induced by WRN targeting in MSI CRC cells. Aim 2: Identify the molecular determinants of therapeutic response to WRN inhibition in MSI CRCs. Aim 3: Elucidate the immunological effects of cell death induced by WRN targeting in MSI CRCs. We will use mouse tumor models because they closely mirror human tumor biology and treatment response, providing the most appropriate in vivo systems for the proposed experiments. The proposed studies will provide critical mechanistic insights into synthetic lethality and therapeutic response in WRN-targeted MSI CRC cells. These studies will establish rationales and identify novel biomarkers for targeting WRN in MSI CRCs, potentially paving the way for more effective therapies against MSI CRCs and other cancers. Project Number: 1R01CA312130-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Lin Zhang | Institution: UNIVERSITY OF SOUTHERN CALIFORNIA, Los Angeles, CA | Award Amount: $581,548 | Activity Code: R01 | Study Section: Mechanisms of Cancer Therapeutics A Study Section[MCTA] View on NIH RePORTER: https://reporter.nih.gov/project-details/11343411