KIBRA impairs DNA damage repair and suppresses osteosarcoma progression by inhibiting the Wnt/β-catenin signaling activity.

Kidney and brain expressed protein (KIBRA) has been implicated in various cancers, but its mechanisms in osteosarcoma remain poorly understood. KIBRA expression was analyzed in osteosarcoma datasets and cell lines. Functional assays, including Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine staining, wound healing, Transwell, and flow cytometry, were performed to assess proliferation, migration, invasion, and apoptosis in osteosarcoma cells after KIBRA overexpression. A subcutaneous xenograft model was established to evaluate tumor growth in vivo. DNA damage response was examined via immunofluorescence staining of the phosphorylated form of histone H2AX (γH2AX) foci and Western blot analysis of RAD51 Recombinase (RAD51) and γH2AX. KIBRA was significantly downregulated in osteosarcoma tissues and cell lines. Overexpression of KIBRA suppressed proliferation, migration, invasion, and DNA damage repair, while promoting apoptosis in osteosarcoma cells. In vivo, KIBRA overexpression inhibited tumor growth and impaired DNA damage repair, as evidenced by increased γH2AX foci and decreased RAD51 expression. Mechanistically, KIBRA inhibited the Wnt/β-catenin signaling activity, and activating this pathway by SKL2001 reversed the inhibitory effects of KIBRA on osteosarcoma progression and DNA damage repair. Therefore, KIBRA acts as a tumor suppressor in osteosarcoma by inhibiting the Wnt/β-catenin signaling activity, thereby impairing DNA damage repair and suppressing malignant progression.