Expression of hedgehog pathway components in prostate carcinoma microenvironment: shifting the balance towards autocrine signalling

Abstract

Aims: The hedgehog (Hh) signalling pathway has been implicated in the pathogenesis and aggressiveness of prostate cancer through epithelial-mesenchymal interactions. The aim of this study was to elucidate the cell-type partitioned expression of the Hh pathway biomarkers in the non-neoplastic and tumour microenvironments and to correlate it with the grade and stage of prostate cancer.

Methods and results: Expression of the Hh pathway components (Shh, Smo, Ptch, Gli1) in the microenvironment of non-neoplastic peripheral zone (n = 119), hormone-naive primary prostate carcinoma (n = 141) and castrate-resistant bone marrow metastases (n = 53) was analysed using immunohistochemistry in tissue microarrays and bone marrow sections. Results showed that epithelial Shh, Smo and Ptch expression was up-regulated, whereas stromal Smo, Ptch, and Gli1 expression was down-regulated in prostate carcinomas compared to non-neoplastic peripheral zone tissue. Ptch expression was modulated further in high-grade and high-stage primary tumours and in bone marrow metastases. Hh signalling correlated with ki67 and vascular endothelial growth factor (VEGF) but not with CD31 expression.

Conclusion: Our results highlight the importance of Hh-mediated epithelial-mesenchymal interactions in the non-neoplastic prostate and imply that shifting the balance from paracrine towards autocrine signalling is important in the pathogenesis and progression of prostate carcinoma.

Figure 1

Western blot analysis of IMR-32 cell lysate using the anti-Shh and anti-Ptch antibodies (1 = molecular weight marker, 2 = IMR-32 cell lysate).

Figure 2

Representative images of Shh (A–C), Smo (D–F), Ptch (G–I) and Gli1 (J–L) expression in non-neoplastic peripheral zone (D, G, J), low-grade prostate carcinoma [Gleason scores 6 and 7 (3+4)] (A, B, E, H, K) and high-grade carcinoma [Gleason scores 7 (4+3), 8 and 9] (C, F, I, L). Arrows in A and B depict the non-neoplastic epithelium. Note that epithelial Shh (A–C), Smo (D–F) and Ptch (G–I) expression is increased and stromal expression is decreased in tumours compared to non-neoplastic tissue. Ptch expression is increased in epithelial cells and decreased in stromal cells of high-grade compared to low-grade tumours (H, I). Stromal expression of Gli1 (J–L) is down-regulated in carcinomas compared to peripheral zone tissue.

Figure 3

A–E, Expression of ki67, CD31 and vascular endothelial growth factor (VEGF) in non-neoplastic peripheral zone (PZ) and primary prostate carcinoma. Expression of Ki67 is lower in non-neoplastic PZ (A) compared to prostate carcinoma (B). Number of CD31-positive vessels increases from non-neoplastic prostate (C) to prostate carcinoma (D). Low expression levels of VEGF in adjacent non-neoplastic epithelium compared to the malignant cells (E). F–H, Expression of Ptch (F), Shh (G) and Gli1 (H) in bone marrow metastases. Note that Ptch expression in epithelial cells of a metastatic tumour is higher than that in primary carcinomas in Figure 2H and 2I.