FETAL ISOFORM OF HUMAN RETINOIC ACID RECEPTOR-BETA EXPRESSED IN SMALL-CELL LUNG-CANCER LINES

The retinoic acid receptor type beta (RARbeta) complementary DNA from a small cell tumor line was amplified, sequenced, and found to be homo logous to the murine RARbeta1. Seventeen lung tumor lines were analyze d. Five of seven small cell lung carcinoma lines expressed RARbeta1, b ut only one other line (epidermoid) expressed the isoform, and this wa s at trace levels. Two other epidermoid lines, as well as three adenoc arcinoma, two adenosquamous, and two large cell-derived lines did not express RARbeta1. Nine adult human tissues, including lung, were analy zed, and in contrast to what has been reported for the mouse, undetect able or barely detectable levels were observed. On the other hand, a t otal of 13 different fetal tissues, at three different developmental s tages, all expressed RARbeta1. RARbeta1 may be a master developmental gene in humans, and the remarkably specific association with small cel l lung carcinoma suggests a molecular link between this type of cancer and development.