THE MURINE FC-GAMMA (FC-GAMMA) RECEPTOR-TYPE-II B1 IS A TUMORIGENICITY-ENHANCING FACTOR IN POLYOMA-VIRUS-TRANSFORMED 3T3 CELLS

The murine receptor for the pc portion of IgG is a molecule expressed by cells of the immune system. This study suggests the hypothesis that Fc gamma receptor type II BI (Fc gamma RIIBI) functions as a progress ion-enhancing factor when expressed ectopically on non-lymphoid tumor cells. It has been shown previously that BALB/c 3T3 cells transformed in vitro with polyoma virus (pyV) do not express Fc gamma RII but acqu ire the expression of this receptor following an in vivo passage in sy ngeneic mice. The specific Fc gamma RII transcript present in tumor ce lls was identified in this report as Fc gamma RIIBI (BI). In order to determine whether or not the ectopically expressed Fc gamma RII plays a role in the progression of these transformed cells, PyV-transformed 3T3 cells were transfected with BI-cDNA. The BI transfected cells were tested for their ability to form local tumors in syngeneic mice, as c ompared to transfected cells which express the co-transfecting neomyci ne resistance (neo(res)) DNA alone or together with the lacZ gene. Fc gamma RIIBI expressors exhibited a significantly higher tumorigenic ph enotype than FcR-negative controls, though both types of cells exhibit ed the same growth curve in vitro. The ability of Fc gamma RIIBI to ac t as a potentially tumorigenicity-enhancing factor was also demonstrat ed as Fc gamma RII was expressed by tumor cells, originating from inoc ulated Fc gamma RIIBI-transfected cells, or from inoculation of a mixt ure of receptor-positive and -negative cells. BI-expressing cells domi nated the tumor-cell population over non-expressors. This dominance st rengthened the hypothesis that FcR plays a role in tumor progression i n vivo. (C) 1996 Wiley-Liss, Inc.