Accelerated growth of syngeneic tumors in mice treated with methylcholanthrene.

BALB/c and C3H- mice were given a single injection of methylcholanthrene (MCA) and were tested at various times thereafter for immunologic reactivity and resistance to syngeneic tumor challenge. MCA treatment did not affect the rejection of H-2-incompatible tumor allografts, the rejection of H-2-compatible skin allografts, or the induction of delayed hypersensitivity to DNCB as measured by footpad challenge. In contrast, mice treated with MCA exhibited an increase susceptibility to challenge with several syngeneic ultraviolet-induced and MCA-induced fibrosarcomas. These studies demonstrate that in the autochthonous host the measurement of host immune status by in vivo cell-mediated immune responses to exogenous antigens does not necessarily predict the host response to tumor growth.