Introduction: More than 14,000 people die from invasive transitional cell carcinoma (InvTCC) of the urinary bladder each year in the US, and more effective therapies are needed. Naturally-occurring canine InvTCC very closely resembles the disease in humans and serves as a highly relevant translational model for novel therapy of human InvTCC. Work was undertaken to identify new entry points for anticancer therapy in dogs with the goal of translating successful therapeutic strategies into humans with InvTCC. Methods: Microarray expression analyses were conducted on canine normal bladder from dogs with no urinary tract disease (n=4) and InvTCC tissues (n=4) using Genome Array 1.0 and analyzed by GeneSpring GX 11, with the stringency of p < 0.02 and a ≥2-fold change. The genes thus identified were further analyzed for functional and pathway analysis using PANTHER (Protein ANalysis THrough Evolutionary Relationships) Classification System. In selecting genes for further study, consideration was also given for evidence of a role of the gene in human InvTCC. From these analyses, DNA methyltransferase 1 (DNMT1) was selected for further study. Immunohistochemistry (IHC) of canine normal bladder and InvTCC tissues was performed to confirm the microarray expression analyses. The effects of targeting DNMT1 in vitro was assessed through MTT assay and Western blot of canine InvTCC cells treated with 5-azacitidine (5-azaC) and trichostatin A (TSA). Results: DNMT1 was expressed in 0 of 6 normal canine bladder samples and in 10 of 22 (45%) canine InvTCC samples. The proliferation of canine InvTCC cells was inhibited by 5-azaC (at concentrations > 5µM) and by TSA (at concentrations > 0.1µM). Western blot results were supportive of DNMT1-related effects having a role in the antiproliferative activity. Discussion and Conclusions: Microarray expression analyses on canine tissues identified DNMT1 as a potentially “targetable” gene. Expression of DNMT1 in canine InvTCC was confirmed by IHC, and in vitro studies confirmed that drugs that inhibit DNMT1 have antiproliferative effects. These findings are similar to those recently reported by Wu et al. (Cancer, 2011) in human InvTCC. These findings are also in line with results of a pre-clinical (pre-human) trial of 5-azaC in dogs with naturally-occurring InvTCC, in which remission or cancer control occurred in 72% of dogs. In conclusion, DNMT1 has excellent potential as a target for InvTCC therapy in humans.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1048. doi:1538-7445.AM2012-1048