Hedgehog pathway activity in the LADY prostate tumor model

Background: Robust Hedgehog (Hh) signaling has been implicated as a common feature of human prostate cancer and an important stimulus of tumor growth. The role of Hh signaling has been studied in several xenograft tumor models, however, the role of Hh in tumor development in a transgenic prostate cancer model has never been examined. Results: We analyzed expression of Hh pathway components and conserved Hh target genes along with progenitor cell markers and selected markers of epithelial differentiation during tumor development in the LADY transgenic mouse model. Tumor development was associated with a selective increase in Ihh expression. In contrast Shh expression was decreased. Expression of the Hh target Patched (Ptc) was significantly decreased while GliI expression was not significantly altered. A survey of other relevant genes revealed significant increases in expression of Notch-I and Nestin together with decreased expression of HNF3a/FoxAI, NPDC-I and probasin. Conclusion: Our study shows no evidence for a generalized increase in Hh signaling during tumor development in the LADY mouse. It does reveal a selective increase in Ihh expression that is associated with increased expression of progenitor cell markers and decreased expression of terminal differentiation markers. These data suggest that Ihh expression may be a feature of a progenitor cell population that is involved in tumor development.