Dr. metastatic prostate cancer. Here we will review these data and highlight Hederasaponin B areas of active clinical research as they relate to Hedgehog pathway inhibition in prostate cancer. Rabbit Polyclonal to NOTCH2 (Cleaved-Val1697) or gain-of-function mutations in mRNA localized to the stromal compartment while SHH localized to the prostatic epithelium, indicating active paracrine Hh signaling from the tumor in the surrounding stroma. [8] However, in a study evaluating human prostate tissue, hybridization of GLI1 mRNA localized to the epithelium but not to the surrounding stroma and was co-expressed with PTCH1 and SHH, suggesting autocrine Hh signaling [8,9]. Tzelepi found that epithelial expression of GLI1, SHH, SMO, and PTCH by immunohistochemistry was higher in primary prostate carcinomas compared with non-neoplastic peripheral zone tissue, but was lower in the surrounding stromal tissue. Higher-grade and higher-stage prostate cancers demonstrated even lower stromal localization of PTCH, with the lowest expression occurring in metastatic bone lesions [10]. Thus, the Hh pathway components appear to be differentially expressed in the tumor microenvironment as compared to benign tissues. The issue of whether clinically relevant Hh signaling in prostate cancer occurs via an autocrine or paracrine model remains an open question. The Hh pathway may be particularly active in men with hormone-na?ve localized prostate cancer at high risk for metastatic spread compared with low-risk tumors. Gene expression profiles from localized high-grade prostate tumors differed in men who either rapidly developed metastases within the first 5 years following radical prostatectomy those men who were metastasis-free for >5 years after surgery. In men who developed early metastases, embryonic stem cell pathways, including the Hh and Notch pathways, were highly differentially expressed compared with the metastasis-free group as determined by gene expression profiling, and was up-regulated 3.7-fold in the early-metastasis cohort, suggesting increased Hh signaling in localized prostate cancer with metastatic potential [11]. Similarly, Kim evaluated 155 radical prostatectomy specimens from men with localized prostate cancers via immunohistochemistry and found increased expression of multiple components of the Hh pathway, including SHH, PTCH1, SMO, and GLI. In Hederasaponin B a multivariate model, increased Hederasaponin B SHH expression was an independent prognostic factor for biochemical Hederasaponin B recurrence beyond clinical factors that included Gleason score, stage, tumor volume, and pretreatment PSA [12]. Cross-talk between the Hh and androgen signaling pathways has been noted both and in human radical prostatectomy specimens (Figure 1). For example, administration of dihydrotestosterone (DHT) to pregnant mice with caused downregulation of androgen-regulated genes in prostate cancer cells while administration of exogenous GLI1 allowed cell growth in an androgen-deficient medium [14]. In addition, Hh signaling may promote the development of castration resistance through induction of steroidogenic activity in prostate cancer cells via paracrine signaling. For example, Levina demonstrated increased gene expression of cholesterol/steroid biosynthetic pathways following administration of a Hh agonist and further demonstrated the subsequent increased output of testosterone from the adrenal precursor: dihydroepiandrosterone (DHEA) [15]. Similarly, Sirab demonstrated the mutual interaction between the androgen receptor (AR) and Hh pathways. Dihydrotestosterone (DHT) administration inhibits SHH in prostate cancer cell lines while administration of cyclopamine modulates the activity of the androgen receptor and can attenuate cell proliferation and AR signaling induced by dihydrotestosterone [16]. This interaction may occur at the level of GLI1 and GLI2 given that co-immunoprecipitation experiments have demonstrated that these transcription factors can bind directly to the androgen receptor protein [17]. Open in a separate window Figure 1 Putative mechanisms of crosstalk between the androgen receptor (AR) and Hh pathways. The correlation between advanced.