Analysis of stroma-derived factors with potential prognostic and therapeutic significance in prostate cancer

Abstract: Prostate cancer is the most common malignancy in Sweden with about 9000 new cases diagnosed every year. New markers are needed to improve diagnostic accuracy. The most commonly used tissue-biomarkers are basal cell markers and AMACR, often used in combination. We identified three potential tissue biomarkers, CYCS, ICK and IKBKB, by using the Human Protein Atlas database and investigated their diagnostic accuracy. The potential of these biomarkers was also compared with AMACR. Immunohistochemical analysis of the markers was performed on a tissue microarray (TMA) consisting of tissue from 40 prostate specimens, including benign prostatic tissue, atrophy, high-grade prostatic intraepithelial neoplasia (HGPIN) and prostate cancer. In addition, qRT-PCR analysis of malignant and benign frozen tissue samples from 32 radical prostatectomy specimens was performed. All four biomarkers showed a higher protein expression in prostate cancer and HGPIN than in benign tissue. The prognostic accuracy was highest for AMACR, but the results indicate that in some cases CYCS, ICK and IKBKB may serve as additional diagnostic markers. It is known that prognostic information can also be derived from tumor stroma. The prognostic value of stromal expression of PDGFR? was therefore evaluated by immunohistochemical analysis of PDGFR? on a TMA containing cancer and non-malignant tissue from more than 300 prostate cancer patients. The association between stromal staining intensity and a number of clinical characteristics were then analyzed. Expression of PDGFR? in non-malignant and tumor stroma was associated with high Gleason grade and reduced cancer specific survival. Cancer associated fibroblasts (CAFs) are found in many solid tumors and promote tumor growth and progression. Identification and inhibition of molecules mediating these interactions constitute an attractive strategy for development of new cancer therapies. By comparative analyses of CAFs and normal fibroblasts from prostate tissue we have identified a number of genes upregulated in prostate CAFs. CXCL14, an orphan chemokine, was the most upregulated transcript. Overexpression of CXCL14 in fibroblasts increased their proliferation and migratory capacity. Also over-expression in fibroblasts of CAF led to increased ability of these cells to stimulate proliferation and migration of prostate cancer cells. Furthermore, fibroblasts overexpressing CXCL14 enhanced tumor growth, vascularisation and macrophage infiltration in a stroma-dependent prostate cancer model. Another transcript identified to be upregulated in prostate CAFs was GDF15, a member of the TGF? superfamily. GDF15 was shown to stimulate fibroblast proliferation and enhanced growth, migration and invasion of prostate cancer cells. Fibroblasts over-expresssing GDF15 was also able to stimulate prostate xenograft growth when co-injected with prostate cancer cells. Interestingly, these fibroblasts also increased the ability of tumor xenograft to promote growth at a distant site suggesting direct or in-direct systemic pro-tumoral effects of fibroblast-derived GDF15. These studies thus identify a set of new diagnostic and prognostic markers for prostate cancer and stromaderived potential therapeutic targets.