Colitis-Associated Colorectal Cancer-STAT3 Inhibition as a Preventive Strategy

Colorectal cancer (CRC) occurs with higher frequency in patients with inflammatory bowel disease (IBD) and has increased morbidity and mortality compared with CRC in patients in the general population. STAT3 has been implicated in CRC development, but strategies to target it have yet to be employed to prevent its occurrence in groups at high risk for CRC. Our group developed TTI-101, a small-molecule STAT3 inhibitor, which was effective in treating colitis in the dextran sodium sulfate (DSS) mouse model. In the current study, we examined the ability of TTI-101 to prevent CRC in the azoxymethane (AOM)-DSS mouse model of CRC. Mice received AOM followed by DSS and were treated with either TTI-101 or vehicle control for 10 weeks. While vehicle-treated AOM-DSS mice developed polyps and adenocarcinomas, TTI-101-treated AOM-DSS mice did not. Levels of activated STAT3 (pY-STAT3) were increased in both the epithelial and stromal compartments of adenocarcinomas vs. normal colon mucosa and correlated with adenocarcinoma burden. Pharmacologically relevant concentrations of TTI-101 were detected in plasma and colon; plasma levels correlated with colon levels and correlated inversely with adenocarcinoma number. Transcriptomic analyses revealed that TTI-101 normalized expression of AOM-DSS-induced CRC-associated genes in the colon, many of which are regulated by STAT3. The addition of DSS to AOM resulted in a distinct cecal microbiome diversity and composition that was muted by the addition of TTI-101. Thus, TTI-101 prevented colitis-associated CRC in the AOM-DSS model through targeting STAT3's pro-oncogenic effects on the colon transcriptome and modulating colitis-associated dysbiosis; targeting STAT3 in patients with IBD merits consideration for CRC prevention, as well as IBD treatment.