In‐Tumor <scp>CRISPR</scp> ‐Cas9 Knockout Screening and Novel Therapy Development for Malignant Transformation of Ovarian Teratoma

Malignant transformation of mature cystic teratoma (MTMCT) of the ovary is a rare but aggressive malignancy for which no standardized chemotherapy or effective targeted therapies currently exist. To identify therapeutic vulnerabilities in MTMCT, we performed a genome-wide CRISPR-Cas9 knockout screen using the MTMCT-derived NOSCC1 cell line. Two parallel selective pressures were applied: in vivo tumorigenicity in immunodeficient mice and cisplatin exposure in vitro. From this screen, 67 negatively selected genes were identified, among which SOD1 and NDUFB4 emerged as top candidates based on high basal expression levels and clinical relevance. Integration with spatial transcriptomic data from three independent MTMCT patient tumors further supported the prioritization of these targets. SOD1 was selected for further investigation due to the availability of known pharmacological inhibitors. Both siRNA-mediated knockdown and small-molecule inhibition of SOD1 using LCS-1 significantly suppressed MTMCT cell proliferation in vitro by inducing oxidative stress and impairing cell cycle progression. This antiproliferative effect was reversed by co-treatment with N-acetylcysteine, a reactive oxygen species scavenger. In vivo validation using patient-derived xenograft models demonstrated that oral administration of LCS-1 led to significant tumor growth suppression and increased expression of apoptotic and DNA damage markers, including cleaved caspase-3 and γH2AX. These findings establish SOD1 as a critical vulnerability in MTMCT and provide preclinical evidence supporting redox modulation as a therapeutic strategy for this highly chemoresistant and understudied ovarian cancer subtype. Our integrative approach combining functional genomics, spatial transcriptomics, and pharmacologic validation offers a framework for the discovery of novel targets in rare gynecologic malignancies.