Expression of bone morphogenetic protein in human adenocarcinoma cell line

A subclone termed as HSG-S8 was previously isolated from human salivary adenocarcinoma cell line, HSG, and proliferated in a serum-free culture. When HSG-S8 and parental HSG cells were transplanted into nude mice i.m. or s.c., both cells reproducibly induced adenocarcinoma. Furthermore, injection of HSG-S8 consistently induced formation of cartilage i.m. or bone s.c. in tumors, but did not parental HSG cells. The cytoplasm of HSG-S8 cells was specifically immunostained by anti-bone morphogenetic protein (BMP)-2 antibody. The conditioned medium of HSG-S8 cells contained a protein of M(r) 18,000 which specifically reacted with anti-BMP-2 protein antibody. Northern blot analysis also revealed that HSG-S8 cells expressed transcripts for BMP-2. On the other hand, parental HSG cells gave a very slightly positive signal only in Northern blot analysis. These results indicate that HSG-S8 cells synthesize and secrete BMP-2 protein, which is probably involved in the formation of cartilage and bone in the tumor tissues in nude mice.