Bone morphogenetic proteins (BMPs), belonging to the
transforming growth factor-beta (
TGF-beta) superfamily, are multifunctional molecules that regulate bone induction and organ development. Among BMPs,
BMP-6 has been shown to be overexpressed in
prostate cancer and is speculated to be associated with bone-forming skeletal
metastasis. We investigated the regulatory mechanism of the
BMP-6 gene expression in
prostate cancer cell lines DU-145, LNCaP, PC-3, and PC-3M with regard to the methylation status of the CpG island in the 5' flanking region of the human
BMP-6 gene. By sequence-specific analysis of methylated cytosines, we show here that the methylation status of the CpG loci around the Sp1 site of the
BMP-6 promoter is related to its steady-state expression and an alternative splicing of
messenger RNA (
mRNA) in
prostate cancer cell lines. Furthermore, a study of clinical cases of benign and malignant prostate lesion by in situ hybridization showed that
BMP-6 expression was high at both primary and secondary sites in cases of advanced
cancer with
metastasis. Demethylation of the CpG loci around the Spl binding site was shown in cases with high
BMP-6 expression by sequencing analysis of the methylated
cytosine from
paraffin-embedded materials. Our results suggested that during
cancer progression, besides inactivation of tumor suppressor genes by hypermethylation, activation of certain genes like
BMP-6 by selective demethylation was a common epigenetic event giving a variable character to the invading and metastasizing
cancer cells.