CPT inhibits expression of COL1A2 mRNA in SSc and healthy control fibroblasts. SSc and healthy control cells were incubated with various concentrations of CPT (10-9 to 10-6 mol/l) and analyzed by northern blotting. (a) Representative northern blot. (b, c) Summary of quantitative analysis of northern blots from healthy control and SSc cell lines, respectively. All values were corrected for loading differences as determined by intensity of GAPDH mRNA. Values from the CPT-treated cells indicate band density relative to that of untreated cells ('None'), which was set at 100. Bars show means ± SEMof the COL1A2/GAPDH ratio from 13 independent experiments using seven different pairs of SSc and healthy control fibroblasts. COL1A2 = type α2(I) collagen; CPT = camptothecin; GAPDH = glyceraldehyde-3-phosphate dehydrogenase; SSc = systemic sclerosis. *P < 0.01, **P < 0.005.