We found that excess HH signaling in prostate stromal cells has an inhibitory effect on cancer progression, potentially owing to maintenance of SM that might prevent micro-invasion of tumors
We found that excess HH signaling in prostate stromal cells has an inhibitory effect on cancer progression, potentially owing to maintenance of SM that might prevent micro-invasion of tumors. and tumors, whereas in PCa they expand little and stromal cells invade into intraductal adenomas. Fate mapping of SMCs showed that in tumors the cells are depleted, whereas they expand in tumors and interestingly contribute to the stromal cells in intraductal adenomas. Hedgehog (HH) ligands secreted by epithelial cells are Secretin (human) known to regulate prostate mesenchyme expansion differentially during development and regeneration. Any possible role of HH signaling in stromal cells during PCa progression is poorly understood. We found that HH signaling is high in SMCs and fibroblasts near tumor cells in all models, and epithelial expression is decreased whereas and are increased. In human primary PCa, expression of is the highest of the three genes, and elevated HH signaling correlates with high stromal gene expression. Moreover, increasing HH signaling in the stroma of PCa resulted in more intact SMC layers and decreased tumor progression (micro-invasive carcinoma). Thus, we propose HH signaling restrains tumor progression by maintaining the smooth muscle and preventing invasion by tumor cells. Our studies highlight the importance of understanding how HH signaling and stromal composition impact on PCa to Secretin (human) optimize drug treatments. and expression is dependent on GLI2 and GLI3 activators, it is a sensitive readout of high-level HH signaling (Bai et al., 2002, 2004). The HH signaling pathway has stage-specific roles during prostate development (Berman et al., 2004; Peng and Joyner, 2015; Yu and Bushman, 2013). LIF During embryonic development HH signaling acts on the mesenchyme to promote ductal extension and branching, whereas at the early postnatal stage HH plays an inhibitory role on ductal morphogenesis. In the adult mouse Secretin (human) prostate, our previous study showed that SHH is secreted by basal epithelial cells and signals to progenitors of all four stromal subtypes (Peng et al., Secretin (human) 2013). A separate study using an knock-in allele revealed that during adult prostate regeneration is preferentially expressed by epithelial cells between growing buds, and functional studies indicate that IHH negatively regulates epithelial bud formation by downregulating stromal (Lim et al., 2014). However, it has not been addressed experimentally whether any specific function of HH signaling is involved in the stromal changes seen during PCa progression. Several studies have provided evidence for paracrine HH signaling in human and mouse PCa (Fan et al., 2004; Ibuki et al., 2013; Shaw et al., 2009), a cellular relationship resembling the epithelial-to-stromal HH signaling in developing and adult mouse prostates (Berman et al., 2004; Peng et al., 2013). Autocrine HH signaling in PCa epithelial cells has also been reported (Chen et al., 2009; Karhadkar et al., 2004; Sanchez et al., 2004), particularly in advanced and metastatic PCa specimens (Chen et al., 2009; Sheng et al., 2004; Tzelepi et al., 2011). Given the questionable reliability of antibodies to HH pathway components, the highly heterogeneous nature of PCa, and the difficulty of effectively separating tumor cells from the stroma, we have taken advantage of mouse genetic tools to study HH signaling during PCa progression in mouse models. Several recent functional studies using mouse genetic carcinoma models found that stromal HH signaling reduces pancreas and bladder cancer progression (Lee et al., 2014; Mathew et al., 2014; Rhim et al., 2014; Shin et al., 2014), consistent with the poor outcomes of HH inhibitors in pancreas cancer clinical trials (Rosow et al., 2012). Specifically, genetic deletion of in pancreatic cancer cells decreases survival and enhances tumor progression (Lee et al., 2014; Rhim et al., 2014), and deletion of in bladder stromal cells promotes carcinogenesis (Shin et al., 2014). In addition, pharmacological modulation of the HH pathway in mice revealed accelerated or delayed pancreatic cancer development following SMO inhibitor or HH agonist treatment, respectively (Lee et al., 2014; Rhim et al., 2014). In a xenograft model, ablation of the HH co-receptors and in mouse embryonic fibroblasts (MEFs) promoted the co-injected human pancreatic cancer cell lines to grow pancreatic tumors, whereas elimination of HH signaling by deletion of and in MEFs inhibited pancreatic tumor growth, indicating a dose-dependent role.