Increased expression of putative cancer stem cell markers in primary prostate cancer is associated with progression of bone metastases

BACKGROUND A number of putative stem cell markers have been associated with aggressiveness of prostate cancer, including alpha 2 and alpha 6 integrin and c‐met. The study aimed to test the hypothesis that the development of bone metastasis correlates with the proportion of prostate cancer stem cell‐like cells present in the primary tumor. METHODS Prostate tissue samples were obtained from patients with high‐risk prostatic adenocarcinoma. Prostate cancer tumor tissue samples underwent immunohistochemical staining for alpha 2 and alpha 6 integrin and c‐met; positive and negative controls were included. Samples were scored as positive if >5% of cells within the sample stained positively. Survival and bone metastasis‐free survival curves on the patient cohort were estimated by the actuarial method of Kaplan–Meier. RESULTS A total of 62 patients were included in the study. Bone metastases progression rate was 46% at 105 months with a median time of 46 months (95% CI: 1–62.5 months); prostate cancer‐specific survival was 33% at 122 months with a median survival time of 69.4 months (95% CI: 63.5–109.4 months). Survival curves show that c‐met‐, alpha 2, and alpha 6 integrin‐positive tumors were positively associated with the occurrence of bone metastasis‐free survival. There was a higher level of significance when at least c‐met and either alpha 2 or alpha 6 integrin was positive. CONCLUSION It can be concluded that percentage of stem cell‐like prostate cancer cells has a prognostic impact especially on the risk of metastatic bone progression. Prostate 72:713–720, 2012. © 2011 Wiley Periodicals, Inc.