Tumor suppression by pyran copolymer: correlation with production of cytotoxic macrophages.

Intraperitoneal administration of pyran copolymer (pyran-2-succinic anhydride-4,5-dicarboxytetrahydro-6-methylanhydride polymer) protected C3H/HeN male mice against tumor development after intradermal challenge with cells of the transplantable, methylcholanthrene-induced, syngeneic fibrosarcoma 1038. Peritoneal cells from pyran-treated but not from normal animals suppressed tumor development in local passive-transfer experiments. Adherent peritoneal cells from pyran-treated mice were cytotoxic in vitro to several syngeneic murine tumor cell lines including 1038.