LACK OF PTC GENE (RET PROTOONCOGENE REARRANGEMENT) IN HUMAN THYROID-TUMORS

PTC gene, which is derived from the rearranged form of the ret proto-o ncogene, was originally discovered in human thyroid papillary carcinom as. This gene has been thought to act as a tumorigenetic factor in thy roid carcinoma, although the action of PTC oncogene products is still unknown. To study the frequency of the PTC gene present in human thyro id carcinomas, we investigated four cell lines derived from thyroid ca rcinoma and 22 thyroid tumor tissue specimens. The reverse transcripta se-polymerase chain reaction (RT-PCR) method was performed to detect p utative PTC mRNA. The presence of the PTC gene in genomic DNA was anal yzed by Southern blot hybridization. PTC mRNA was detected by the RT-P CR method in only one papillary carcinoma cell line (TPC-1 cell). Sout hern gel analysis confirmed the rearrangement of the ret proto-oncogen e in this cell line. In the other three cell lines and 22 tumor tissue specimens, however, neither the PTC gene or mRNA was detected. These results demonstrate that the prevalence of the PTC gene in thyroid tum or is low and may not be essential for human thyroid tumorigenesis. Th at our present results conflict with previous reports may be due to ge neral differences in genetic background among races.