Analysis of L1CAM-regulated signaling pathways and cellular responses to anti-L1CAM radioimmunotherapy in human ovarian cancer cells

L1 cell adhesion molecule (L1CAM) is overexpressed in various solid tumors, and its overexpression is linked to increased invasion, metastasis, angiogenesis, cancer stemness, and therapy resistance. However, the mechanisms of L1CAM-mediated carcinogenesis and radioresistance, particularly in high-grade serous ovarian carcinoma (HGSOC), the most common and lethal type of ovarian cancer, remain insufficiently understood. Anti-L1CAM radioimmunotherapy (RIT) using the radioisotopes Terbium-161 (Tb-161) and Lutetium-177 (Lu-177) has shown that Tb-161 is more cytotoxic than Lu-177, due to its distinct radioactive properties. Moreover, we identified a population of L1CAM+/CD133+ cells as cancer stem cells (CSCs) in ovarian cancer and demonstrated L1CAM's association with radioresistance. Understanding L1CAM-regulated downstream signaling and cellular responses to anti-L1CAM RIT with Tb-161, compared to Lu-177, is now critical. To address this, we established CRISPR-Cas9-mediated L1CAM knock-out (ΔL1CAM) in human ovarian cancer cells (OVCAR8) alongside a control cell line with a knockout of the nonessential gene AAVS1 (ΔAAVS1). In this study, quantitative phosphoproteomics, coupled with matching proteomics, revealed (i) L1CAM-dependent signaling pathways and biological processes by comparing ΔL1CAM with wild-type cells, and (ii) cellular responses to anti-L1CAM RIT with Tb-161 and Lu-177 in L1CAM-expressing ovarian cancer cells.