Figure 4.

Per2 is required for LDR-induced adaptive radioprotection (see also Figure S5)

(A and B). Per2 expression in mouse BMMNCs and MEFs (A) and in human mammary epithelial MCF-10A cells and skin keratinocytes HK18 (B) at different times after LDR.

(C-E) Western blot of Per2 in primary cultured epithelial cells derived from healthy human mammary tissues 12 h following exposure to LDR. Cell apoptosis (D) and clonogenic survival (E) of MCF-10A cell exposed to Sham, LDR, HDR or LDR 8 h before HDR. Data are represented as mean ± SEM, n = 3; ∗∗p < 0.01, Student’s t test.

(F) LDR-induced radioprotection was measured by apoptosis with flow cytometry in Per2^wt and Per2^def BMMNCs 24 h after HDR or LDR 8 h before HDR. Data are represented as mean ± SEM, n = 6, ∗p < 0.05, ∗∗p < 0.01, ANOVA two-way test was applied.

(G–I) LDR-induced radioprotection was measured by GM-CFU assay in Per2^wt and Per2^def BMMNCs after HDR or LDR 8 h before HDR. Data are represented as mean ± SEM, n = 3, ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ANOVA two-way test was applied. Cell proliferation (H) and clonogenic survival (I) of MCF-10A cells transfected with siPer2 or scrambled siPer2 following exposure to Sham, LDR, HDR or LDR 8 h before HDR. Data are represented as mean ± SEM, n = 3, ∗∗p < 0.01, ns p > 0.05, ANOVA two-way test was applied.