Epigenetic regulation of mammalian Hedgehog signaling to the stroma determines the molecular subtype of bladder cancer.

Abstract

In bladder, loss of mammalian <i>Sonic Hedgehog</i> (<i>Shh</i>) accompanies progression to invasive urothelial carcinoma, but the molecular mechanisms underlying this cancer-initiating event are poorly defined. Here, we show that loss of <i>Shh</i> results from hypermethylation of the CpG shore of the <i>Shh</i> gene, and that inhibition of DNA methylation increases <i>Shh</i> expression to halt the initiation of murine urothelial carcinoma at the early stage of progression. In full-fledged tumors, pharmacologic augmentation of Hedgehog (Hh) pathway activity impedes tumor growth, and this cancer-restraining effect of Hh signaling is mediated by the stromal response to Shh signals, which stimulates subtype conversion of basal to luminal-like urothelial carcinoma. Our findings thus provide a basis to develop subtype-specific strategies for the management of human bladder cancer.