One of the functions of adenomatous polyposis coli (APC) in colorectal cancers is regulation of c-myc gene expression. However, the role of APC in lung cancers has not been elucidated. In the present study, the levels of APC and c-myc mRNA were determined in one strain of normal human bronchial epithelial (NHBE) cells, an SV-40-immortalized non-tumorigenic human bronchial epithelial cell line (BEAS-2B), 13 non-small cell lung cancer cell lines, and 4 small cell lung cancer cell lines. To establish a relationship between c-Myc and APC, we determined the ratio of c-myc and APC mRNA levels in different lung cancer cell lines. Out of 19 lung cancer cell lines, we found that 13 exhibited c-myc/APC mRNA ratio of more than two. Among the cell lines CaLu-3, NCI-H82, A427 and SW900 showed a very low level of APC mRNA and a high level of c-myc mRNA. The ratio of c-myc/APC mRNA in these cell lines was 48, 127, 325 and 708, respectively. The results of these analyses revealed an inverse relationship between APC and c-myc mRNA levels, suggesting that APC may regulate c-myc expression in lung cancer cells in a manner analogous to its role in colon cancer.

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