(A) Effects of cisplatin and/or UV-C on cell proliferation markers, phospho-Rb and cyclin D1 in human colorectal cancer cells. SW480, DLD-1, HT29 and HCT116 cells were first exposed to 10 J/m² of UV-C or not, and then treated with 10 μM of cisplatin for the indicated periods. Protein extracts were harvested and examine by Western blotting using anti-phospho-Rb and anti-cyclin D1 antibodies. (B) Effects of cisplatin and/or UV-C on colony formation in SW480, DLD-1, HT29 and HCT116 human colorectal cancer cells. The attached human colorectal cancer cells were first exposed to the indicated doses UV-C (0 or 10 J/m²), just after the aspiration of the growth medium. The cells were then incubated in normal growth media with/without 10 μM cisplatin for 24 h. After trypsinization, the counted cells (3 x 103) were re-seeded into new culture dishes and incubated for 7 days. The cells were then fixed with clonogenic reagent (see Materials and methods) and the average number of colony from 5 randomly chosen fields (x 20) were counted, respectively. Bars designate SD of triplicate assay. The asterisks (* and **) indicate significant decrease (p < 0.05) as compared to the control and UV-C alone, respectively.