Retinoic Acid Induces Changes in c- fgr Proto-Oncogene mRNA Levels in Burkitt's Lymphoma Cells

Abstract

The c- fgr proto-oncogene is expressed in Burkitt's lymphoma (BL) cells and cell lines derived from them. When Epstein-Barr virus (EBV)-negative BL cell lines that contain low levels of c- fgr mRNA are infected with EBV, transcription of the c- fgr gene is further induced. In this paper we show that treatment of EBV-negative and EBV-positive BL cell lines with all- trans retinoic acid also stimulates an increase in c- fgr mRNA levels, varying between 2- and 13-fold depending on the cell line. An increase is detectable 12 to 48 h after treatment, depending on the cell line, suggesting that the c- fgr gene is not regulated directly by retinoic acid but responds to other retinoic acid-induced changes in the cell. We also show that treatment of BL cell lines with all- trans retinoic acid either results in a dose-dependent decrease in growth rate, or has no effect on growth, depending on the cell line. It has previously been suggested that the c- fgr gene product might have a role in regulating the growth of BL cells, since treatment of the EBV-positive BL cell line Daudi with α-interferon results in a decrease in c- fgr mRNA levels followed by a decrease in growth rate. Our data indicate that there is no general correlation between c- fgr mRNA levels and growth rate in BL cells and so argue against a role for the c- fgr gene product in growth regulation in these cells.