The Sonic Hedgehog Pathway Stimulates Prostate Tumor Growth by Paracrine Signaling and Recaptures Embryonic Gene Expression in Tumor Myofibroblasts

The Hedgehog (Hh) pathway contributes to prostate cancer growth and progression. The presence of robust Shh expression in both normal prostate and localized cancer challenged us to explain the unique growth promoting effect in cancer. We show here that paracrine Hh signaling exerts a non-cell autonomous effect on xenograft tumor growth and that Hh pathway activation in myofibroblasts alone is sufficient to stimulate tumor growth. Nine genes regulated by Hh in the mesenchyme of the developing prostate were found to be regulated in the stroma of Hh over-expressing xenograft tumors. Correlation analysis of gene expression in matched specimens of benign and malignant human prostate tissue revealed a partial 5 gene fingerprint of Hh-regulated expression in stroma of all cancers and the complete 9 gene fingerprint in the subset of tumors exhibiting a reactive stroma. No expression fingerprint was observed in benign tissues. We conclude that changes in the prostate stroma due to association with cancer result in an altered transcriptional response to Hh that mimics the growth promoting actions of the fetal mesenchyme. Patients with an abundance of myofibroblasts in biopsy tissue may comprise a sub-group that will exhibit a particularly good response to anti-Hedgehog therapy

Regulation of Phosphatase Homologue of Tensin Protein Expression by Bone Morphogenetic Proteins in Prostate Epithelial Cells

Phosphatase homologue of tensin (PTEN) is the key endogenous inhibitor of phosphoinositide signaling and is the most commonly mutated gene in human prostate cancer. The bone morphogenetic proteins (BMPs) are secreted developmental signaling molecules known to promote differentiation in the prostate. BMP ligands have been shown to inhibit prostate cancer cell line proliferation and tumor growth and expression of BMPs, BMP ligands, receptors and signaling effectors are diminished in prostate cancer. A previous report in the colon led us to investigate the potential mechanistic relationship between PTEN and BMP signaling in prostate epithelial cells. We show here that BPM signaling positively regulates PTEN in normal and malignant prostate cells by increasing mRNA expression and stabilizing PTEN protein. Further, we show that BMP attenuates prostate cell growth at least in part through its effects on PTEN. BMP treatment did not further inhibit the growth of conditional PTEN over-expressing cells, and stable shRNA-PTEN transfectants were refractory to BMP-mediated growth inhibition. Loss-of-function of PTEN in prostate cancer cells may render them insensitive to the normal differentiating and growth-inhibitory effects of BMPs. These data are the first to identify a mechanistic linkage between BMP signaling and PTEN in normal prostate epithelial cells and to suggest coordinate dysregulation in prostate cancer

Comment on basal epithelial stem cells as efficient targets for prostate cancer initiation

Human prostate adenocarcinoma is a multicentric disease with histological heterogeneity and variation in biological features. The present study showed that a cell with stem properties undergoing oncogenic transformation can produce prostate mouse lesions with varied histological phenotypes that resemble different grades of human prostate cancer. This powerful observation is consistent with the notion that a complex spectrum of prostate neoplasms may arise from a common cell of origin, facilitating future studies to understand the development of prostate disease. Even so, it must be noted that there is no conclusive evidence that stem cells are the source of human prostate cancer, and therefore additional studies are required comparing features and natural history of tumors generated by this approach with the process of oncogenesis in the human prostate

The role of prostate inflammation and fibrosis in lower urinary tract symptoms

Lower urinary tract symptoms (LUTS) in aging men are extremely common. They have historically been attributed to benign prostatic hyperplasia (BPH), enlargement of the prostate, and bladder outlet obstruction. However, recent studies have revealed acute and chronic inflammation to be highly associated with LUTS, correlated with prostatic enlargement, and implicated as a cause of prostatic fibrosis that contributes to bladder outlet obstruction. This review examines the evidence implicating inflammation and fibrosis in BPH/LUTS. It identifies potential mechanisms by which inflammation may drive nociceptive signaling as well as hyperplastic growth and fibrosis and identifies targets for pharmacological intervention. This is a promising area for research and development of novel therapies to prevent or more effectively treat LUTS in aging men

Second-harmonic generation microscopy analysis reveals proteoglycan decorin is necessary for proper collagen organization in prostate.

Collagen remodeling occurs in many prostate pathologies; however, the underlying structural architecture in both normal and diseased prostatic tissues is largely unexplored. Here, we use second-harmonic generation (SHG) microscopy to specifically probe the role of the proteoglycan decorin (Dcn) on collagen assembly in a wild type (wt) and Dcn null mouse (Dcn  -    /    -  ). Dcn is required for proper organization of collagen fibrils as it regulates size by forming an arch-like structure at the end of the fibril. We have utilized SHG metrics based on emission directionality (forward-backward ratio) and relative conversion efficiency, which are both related to the SHG coherence length, and found more disordered fibril organization in the Dcn  -    /    -  . We have also used image analysis readouts based on entropy, multifractal dimension, and wavelet transforms to compare the collagen fibril/fiber architecture in the two models, where all these showed that the Dcn  -    /    -   prostate comprised smaller and more disorganized collagen structures. All these SHG metrics are consistent with decreased SHG phase matching in the Dcn  -    /    -   and are further consistent with ultrastructural analysis of collagen in this model in other tissues, which show a more random distribution of fibril sizes and their packing into fibers. As Dcn is a known tumor suppressor, this work forms the basis for future studies of collagen remodeling in both malignant and benign prostate disease

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 Gli1 expression was not significantly altered. A survey of other relevant genes revealed significant increases in expression of Notch-1 and Nestin together with decreased expression of HNF3a/FoxA1, NPDC-1 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

Hedgehog pathway responsiveness correlates with the presence of primary cilia on prostate stromal cells

<p>Abstract</p> <p>Background</p> <p>Hedgehog (Hh) signaling from the urogenital sinus (UGS) epithelium to the surrounding mesenchyme plays a critical role in regulating ductal formation and growth during prostate development. The primary cilium, a feature of most interphase vertebrate cell types, serves as a required localization domain for Hh signaling transducing proteins.</p> <p>Results</p> <p>Immunostaining revealed the presence of primary cilia in mesenchymal cells of the developing prostate. Cell-based assays of a urongenital sinus mesenchymal cell line (UGSM-2) revealed that proliferation-limiting (serum starvation and/or confluence) growth conditions promoted cilia formation and correlated with pathway activation associated with accumulation of Smoothened in primary cilia. The prostate cancer cell lines PC-3, LNCaP, and 22RV1, previously shown to lack demonstrable autocrine Hh signaling capacity, did not exhibit primary cilia even under proliferation-limiting growth conditions.</p> <p>Conclusion</p> <p>We conclude that paracrine Hedgehog signaling activity in the prostate is associated with the presence of primary cilia on stromal cells but that a role in autocrine Hh signaling remains speculative.</p

Establishment and characterization of immortalized Gli-null mouse embryonic fibroblast cell lines

<p>Abstract</p> <p>Background</p> <p>Hedgehog (Hh) signaling is a conserved morphogenetic pathway which plays critical roles in embryonic development, with emerging evidence also supporting a role in healing and repair processes and tumorigenesis. The Gli family of transcription factors (Gli1, 2 and 3) mediate the Hedgehog morphogenetic signal by regulating the expression of downstream target genes. We previously characterized the individual and cooperative roles of the Gli proteins in Hh target gene regulation using a battery of primary embryonic fibroblasts from Gli null mice.</p> <p>Results</p> <p>Here, we describe the establishment of spontaneously immortalized mouse embryonic fibroblast (iMEF) cell lines lacking single and multiple Gli genes. These non-clonal cell lines recapitulate the unique ligand mediated transcriptional response of primary MEFs. While loss of Gli1 had no effect on target gene induction, Gli2 null cells demonstrated reduced target gene induction while Gli3 null cells exhibited elevated basal and ligand-induced expression. Target gene response in <it>Gli1</it>^-/-<it>2</it>^-/-iMEFs was severely reduced while <it>Gli2</it>^-/-<it>3</it>^-/-iMEFs were incapable of ligand-induced transcriptional response. However, we found that both <it>Gli1</it>^-/-<it>2</it>^-/-and <it>Gli2</it>^-/-<it>3</it>^-/-iMEFs exhibited robust leukotriene synthesis-dependent migration responses to Hh ligand, demonstrating that this response is not transcriptionally-dependent.</p> <p>Conclusion</p> <p>This study provides fundamental characterizations of the transcriptional and non-transcriptional Hh responsiveness of a battery of Gli-null iMEFs. Moving forward, these cell lines should prove a valuable tool set to study the unique functional regulation of the Gli proteins in a Hh-responsive cell-type.</p