Bone morphogenetic proteins (BMPs) have multiple
biologic functions, including bone formation and embryonic induction. One of these
proteins,
BMP-6, was reportedly expressed at high levels in human
prostate cancers that had also metastasized to bone. This study investigated both
BMP-6 mRNA and
protein expression in normal and malignant rat and human prostate tissues.
BMP-6 was detected in both rat normal prostate and in Dunning rat-prostate
adenocarcinoma sublines. The levels of
BMP-6 mRNA and
protein were similar for normal and malignant rat prostate, regardless of the metastatic potential. Moreover,
castration had no apparent effect on
BMP-6 production in rat normal ventral prostate, suggesting an
androgen-independent gene regulation of this
protein.
BMP-6 mRNA and
protein were also produced by normal and neoplastic human
prostate cancer (radical
prostatectomy specimens and human
carcinoma cell lines DU145 and PC3).
BMP-6 mRNA and
protein expression, however, was higher in
prostate cancer as compared with adjacent normal prostate, with higher-grade
tumors (Gleason score of 6 or more) having greater
BMP-6 immunostaining than the lower-grade
tumors (Gleason score of 4 or less). Taken together, these results suggest that
BMP-6 protein expression may serve as a potential marker for
prostate cancer but not as a metastatic marker. Moreover,
BMP-6 may contribute to prostate neoplastic behavior even in the absence of
androgens.