Figure 6. SPINK1 decreases radiation-induced DNA damage and enhances radioresistance of cancer cells in a NRF2-dependent manner.

(A and B) Four days after being transfected with either pcDNA4/SPINK1 (SPINK1) or its EV, DU145 cells were subjected to qPCR. (C–I) HeLa/scramble cells and HeLa/shSPINK1-1, HeLa/shSPINK1-2, and HeLa/shSPINK1-3 cells were cultured under severe hypoxic conditions (O₂ < 0.1%) for 48 hours, irradiated with 0 (C, D, and I) or 4 (E–I) Gy of γ-rays and subjected to qPCR (C–H) or the DCFDA cellular ROS assay (I). Cells were irradiated in the presence or absence of the EGFR-I III (G and H). (J) DU145 cells were irradiated with γ-rays in the presence or absence of 100 ng/mL rSPINK1 in combination with DMSO or 2 μM ML385 and subjected to the colorimetric cell viability assay. Data are represented as mean ± SD (n = 3 in A–J). Two-tailed Student’s t test (A, B, and J). One-way ANOVA with Dunnett’s test (C–I). *P < 0.05, **P < 0.01, ***P < 0.001. SPINK1, serine peptidase inhibitor Kazal type 1; EV, empty vector; DCFDA, dichlorodihydrofluorescein diacetate; EGFR-I III, EGFR Inhibitor III.