Expression of chloramphenicol acetyltransferase (CAT) from rodent type I collagen promoters in transfected osteosarcoma cells in vivo

Abstract

We examined the osteoblastic phenotype of permanently transfected ROS 17/2.8 cells in culture and in vivo, in order to evaluate their relevance for studies of the regulation of gene expression and gene function in osteoblastic cells. Recent reports indicate that the progeny transfected cells may substantially vary and differ from the parental cell line in their phenotype, particularly in their tumorigenicity. ROS 17/2.8 cells were transfected with genetic constructs expressing the CAT gene from either the rat α1(I) or the mouse α2(I) collagen promoters. Fortyfour clonal cell lines display a range of CAT expression from the transfected collagen promoters in culture. Four of these cell lines were further characterized. Alkaline phosphatase activity in these four cell lines is higher than in fibroblastic cells. These four cell lines are tumorigenic in immunocompatible ACI rats and form calcified tumors similar to those formed by ROS 17/2.8. CAT expression could be demonstrated in tumor extracts of two of the four cell lines, which also expressed higher CAT levels in culture. We conclude that permanently transfected ROS 17/2.8 derived cell lines maintain their tumorigenicity and their osteoblastic-like phenotpye, and thus may provide a useful system for studies of gene function and regulation in osteoblast-like cells and bone-like tissue in vivo.