Impaired tumor phenotypes in class II major histocompatibility complex antigen-inducible cells originated from human lung adenocarcinoma.

The class II major histocompatibility complex (MHC) antigens play important roles in T cell activation and are thought to be involved in tumor development. Using anti-class II antibodies with interferon gamma (IFN-gamma), we have here selected class II MHC antigen positive cancer cells from the human lung adenocarcinoma cell line A549, which is originally negative (> 95%) for the antigens. A part of the class II antigen-positive cells presented a flat morphology, which was not observed in the parental A549 cells. Class II antigen expression in these flat cells was IFN-gamma inducible; there was a correlation between the inducibility and phenotypic changes. A class II antigen-inducible flat subline restored the ability of contact inhibition and anchorage-dependent growth as well as lost tumorigenicity in athymic mice.