Abstract
BACKGROUND: The phosphatase and tensin homolog (PTEN) is a classical tumor-suppressor gene. Its expression deficiency concurrently drives disease progression in approximately 30% of melanomas and is closely associated with radiotherapy tolerance. However, there is a lack of systematic evidence regarding whether and how PTEN regulates the radiosensitivity of melanoma. METHODS: The expression of PTEN was validated using TCGA database, clinical tissue microarrays, and multiple melanoma cell lines. PTEN knockdown (PTEN-KD) and PTEN overexpression (PTEN-OE) stable cell lines were constructed using lentiviral vectors. CCK-8, colony formation assay, annexin V/PI flow cytometry, neutral comet assay, cell-cycle analysis, and Western blotting were used to assess the biological changes in cells after 0 Gy-8 Gy γ-ray irradiation (IR). A cell-derived xenograft model was established, and the tumor volume was observed after local 10 Gy IR for 28 days; in addition, H&E, Ki67, and TUNEL evaluations were performed. RESULTS: The expression of PTEN in melanoma tissues and cell lines was significantly lower than that in normal controls. IR could induce a transient upregulation of PTEN followed by rapid downregulation. PTEN-OE significantly inhibited proliferation, reduced the clone survival rate, increased apoptosis, and weakened radiation-induced G(2)/M phase arrest; however, the opposite was true for PTEN-KD. Mechanistically, PTEN-OE inhibited the DNA-PKcs axis, reduced NHEJ-mediated rapid repair, and increased the persistent expression of γ-H2AX. PTEN-KD activated the p-ATM/p-Chk2 signaling. Animal experiments confirmed that the tumor volume in the PTEN-OE + IR group was significantly lower than that in the NC + IR group, with an expanded necrotic area, a decreased Ki67 index, and an increased TUNEL-positive rate. CONCLUSION: PTEN enhances the radiosensitivity of melanoma by inhibiting the DNA-PKcs signal, weakening NHEJ repair, and delaying cell-cycle recovery. PTEN can serve as a biomarker for radiotherapy response prediction and a target for sensitization intervention, providing an experimental basis for precise radiotherapy strategies for melanoma.