TRIM35 functions as a novel tumor suppressor in breast cancer by inducing cell apoptosis through ubiquitination of PDK1.

Breast cancer is the most common cancer in women. Novel mechanisms and targets are urgently needed to understand and treat this disease due to the complexity of breast cancer. In this study, we evaluated the expression level of tripartite motif-containing (TRIM) 35 in various breast cancer cell lines by qPCR and immunoblot. Cell proliferation assay and flow cytometry were performed upon overexpression and depletion of TRIM35. Xenograft tumor model was applied to validate the findings observed in vitro. The correlation between TRIM35 and outcomes of breast cancer patients was investigated by analyzing The Cancer Genome Atlas database. We observed differential expression of TRIM35 in various breast cancer cell lines. Overexpression of TRIM35 significantly inhibited cell proliferation and promoted cell apoptosis. On the contrary, depletion of TRIM35 exerted the opposite effects on cell proliferation and apoptosis. Mechanistically, TRIM35 reduced PDK1 by ubiquitination, resulting in the degradation of PDK1. Overexpression of TRIM35 significantly suppressed ZR7530 cell line-derived xenograft tumor growth by inducing apoptosis. Finally, a lower level of TRIM35 was associated with a poor prognosis in patients. In conclusion, TRIM35 functions as a tumor suppressor to suppress breast cancer proliferation by inactivating AKT signaling through the increased ubiquitination of PDK1, resulting in the promotion of apoptosis.