Figure 5.

Effect of CTSL inhibition on DNA repair and genomic stability in BOGA cells. (A) Neutral comet assays after 8 Gy of IR show higher olive moments, and thus defects in the fast phase of DNA repair in BOGA cells. Inhibition of CTSL activity by treatment with vitamin D (10⁻⁷ M) 24 h before IR rescues defects in DNA DSB repair. (B) Control and BOGA cells were incubated with vehicle control (C) or vitamin D (VD) for 24 h before IR with 2 Gy (IR). Cells collected 24 h after IR were analyzed for genomic instability by quantitating the percentage of metaphases presenting with chromosomal aberrations, as shown in the images. N, number of independent experiments (50 metaphases analyzed per condition in each experiment). (C) Control and BOGA cells were incubated with the cathepsin inhibitor (E-64) or vehicle control (C) for 24 h before IR, and the extent of genomic instability was assessed as in B. (D) Graph shows relative numbers of BOGA cells 4 d after treatment with IR, vitamin D, or a combination of both. Treatment protocol as in B. (E) Graph shows relative numbers of BOGA cells 4 d after treatment with IR, E-64, or a combination of both. Treatment performed as in C. All values expressed as mean ± SD. N, number of independent experiments. Asterisk denotes a p-value of statistical significance (*, P ≤ 0.05). Bars, 10 µm.