The role of NO in dermal fibroblast proliferation has been previously described by Chen et al [32], who suggested that inhibition of dermal fibroblast proliferation by UV light, might be related to the up-regulation of iNOS gene expression and thus to NO over-secretion In agree with these results, we may suggest that NO production is a negative regulator of fibroblast proliferation and activation when BCG is used in bladder cancer therapy. The gene discussed is NOS2; the disease is urinary bladder cancer.