Interferon-mediated in vivo induction of beta 2-microglobulin on small-cell lung cancers and mid-gut carcinoids.

Selected neuroendocrine tumors, such as small cell lung cancer (SCLC), and neuroblastoma express markedly diminished class I major histocompatibility complex (MHC) antigens (HLA framework and beta 2-microglobulin, beta 2m). Another neuroendocrine tumor, mid-gut carcinoid, also expresses reduced beta 2m antigen as demonstrated herein. Antigen expression is greatly enhanced on SCLC cell lines by in vitro exposure to interferon (IFN). To determine whether IFN mediates similar effects in vivo, we examined by immunoperoxidase staining beta 2m expression in paraffin-embedded tumor tissue sections obtained from 4 SCLC and 7 mid-gut carcinoid patients before and after receiving partially purified human leukocyte IFN-alpha therapy. Before IFN treatment, 3/4 SCLC tumors and 5/7 mid-gut carcinoids did not express beta 2m. By contrast, all tumors showed considerable expression of beta 2m after IFN therapy. Induction of class I antigens on tumor cells deficient in such expression may be one mechanism by which IFN exerts antitumor effects. We believe this is the first report of in vivo induction of class I MHC antigens in epithelial tumor cells in humans.