[No point mutation of the 2.8 kb EcORI fragment of the nasopharyngeal carcinoma transforming gene TX in nasopharyngeal carcinoma].

We have previously cloned a nasopharyngeal carcinoma transforming gene from human nasopharyngeal carcinoma cell line CNE-2 using mouse JB6 cell line as the recipient cells. This transforming gene, designated Tx, exhibits moderate transforming activity upon transfection into JB6 cells. Several lines of evidence indicate that the 2.8 kb EcoRI fragment which lies in the middle of the Tx gene is responsible for the transforming activity. The sequence of the 2.8 kb EcoRI fragment was determined, which showed striking homology with the human immunoglobulin light chain C region gene. Using the modified polymerase chain reaction-single strand conformation polymorphism analysis (PCR-SSCP) silver staining technique, we studied the possible point mutations of the nasopharyngeal carcinoma gene Tx in nasopharyngeal carcinoma. No mobility shift was detected in eleven paired cases of nasopharyngeal carcinoma biopsies suggesting that in most cases of nasopharyngeal carcinoma, the Tx gene is not activated via a mode of point mutation. Taken together with the previously obtained results we have found that the Tx gene is not activated by gene rearrangement or gene amplification. Therefore, we consider that the Tx gene may have been activated by its interaction with other regulatory factors.