Abstract A039: A whole genomic CRISPR-Cas9 screen identifies the LAT3 (SLC43A1) neutral amino acid transporter as a major determinant of oxaliplatin resistance in colorectal cancer cells

Abstract Colorectal cancer (CRC) is the second leading cause of cancer deaths, with a five-year survival rate of 65%. Oxaliplatin was the first platinum drug shown to improve CRC patient outcomes and is now a common adjuvant therapy for advanced disease, yet 90% of patients develop resistance. Oxaliplatin was developed as a third-generation derivative of cisplatin, but recent evidence points to divergent modes of action. Genome-wide CRISPR activation and knockout screens were conducted to identify genetic changes that confer resistance to oxaliplatin in two CRC cell lines with distinct molecular backgrounds (SW620 and RKO). Guide RNAs corresponding to the neutral amino acid transporter SLC43A1 (LAT3) were the most significantly enriched in knockout screens and depleted in activation screens, suggesting a potential role for LAT3 in modulating oxaliplatin resistance. In vitro CRISPR knockout and overexpression of LAT3 in SW620 and RKO cell lines confirm increased resistance or sensitivity to oxaliplatin, respectively, and this correlated with levels of intracellular accumulation of oxaliplatin and DNA damage, demonstrating that enhanced LAT3-mediated uptake of oxaliplatin can exert its expected mechanism of action and induce cytotoxicity. Further studies to investigate the specificity of this mechanism of resistance to oxaliplatin in CRC and other cancers are ongoing to clarify the molecular basis of oxaliplatin resistance. These findings suggest a novel use for LAT3 as a potential biomarker and predictor of oxaliplatin sensitivity and can provide insights into the interplay between essential nutrient uptake and drug transport. Citation Format: Nisha R. Pawar, Heidi M. Wade, Allison V. Mitchell, Connor P. Jewell, Lisa M. Jenkins, Robert W. Robey, Michael M. Gottesman. A whole genomic CRISPR-Cas9 screen identifies the LAT3 (SLC43A1) neutral amino acid transporter as a major determinant of oxaliplatin resistance in colorectal cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A039.