In search of a possible pathway that would explain, at least in part, the properties of BCG as the gold standard treatment for bladder cancer, we used a combination of SSH, differential display, and Virtual Northern and discovered three major groups of genes: members of the small GTPase signaling molecules; those involved in antigen presentation (HLAs); and genes down-regulated by BCG, including uroplakin 3a and uroplakin 2. This evidence concerns the gene UPK2 and urinary bladder cancer.