Modulation of the cluster 1 and mucin antigens in human small cell lung cancer and other epithelial tumour cell lines after treatment with the differentiation inducing agent, sodium butyrate.

The expression of the human small cell lung cancer (SCLC) cluster 1 antigen and the human milk fat globule membrane (HMFG) antigen were studied in three SCLC, three lung adenocarcinoma, six ovarian adenocarcinoma and three colorectal adenocarcinoma cell lines before and after culture in the presence of the differentiation inducing agent, sodium butyrate. Before treatment, only SCLC and well differentiated ovarian cell lines expressed the cluster 1 antigen. After 4 days culture with sodium butyrate, expression of cluster 1 antigen was induced in poorly differentiated ovarian, colorectal and lung adenocarcinoma cell lines whereas existing antigen expression was enhanced in SCLC and well differentiated ovarian cell lines. The expression of the HMFG antigen was also modified. Induction of cluster 1 antigen correlated with increased levels of alkaline phosphatase in the treated cell lines, this enzyme being associated with a more differentiated state in colon and ovarian carcinoma cell lines. The pattern of induction of cluster 1 antigen expression suggests that several different epitopes of this antigen are recognised by the ten SCLC cluster 1 antibodies studied.