Differential expression of osteonectin/SPARC during human prostate cancer progression

The precise mechanism(s) involved in invasion and metastasis of prostate ca ncer (CaP) is poorly understood. Osteonectin [ON (also known as SPARC or BM -40)] is an antiadhesive protein known to be involved in cell-matrix intera ctions, migration, and angiogenesis. In this report, we studied the express ion of ON in human prostate cell lines, primary tumors, and metastatic foci of Cap, Reverse transcription-PCR and nonradioactive in situ hybridization (ISH) techniques were used to determine ON gene expression. Immunohistoche mistry was carried out using the polyclonal antibody LF37 and/or the monocl onal antibody ON-mAb, Low to moderate levels of ON mRNA and protein were ob served in glandular epithelial cells of normal tissue as well as a few prim ary CaPs, However, high levels of ON mRNA and protein were observed in most of the Cap metastatic foci, both osseous and nonosseous. This correlated w ell with our findings that multiple different CaP cell lines including four CaP cell lines derived from metastases show high levels of ON gene express ion. Furthermore, ISH analyses and cell-specific reverse transcription-PCR evaluation showed that both the luminal and basal cells express the ON gene . We conclude that the differential pattern of ON expression suggests that it may play an important role in the progression of CaP.