These results indicate that the positive transcriptional regulation of RET is closely associated with early neuronal differentiation and suggest that a negative regulatory factor/s controls RET transcription in neuroblastoma cells.
These analyses were performed using both RET cDNA cloned from a pheochromocytoma library and reverse transcriptase PCR products generated using RNA from a neuroblastoma cell line (LA-N-2).
The level of tyrosine phosphorylation of the 150 kDa proto-Ret protein was approximately 10-fold higher than that of the 170 kDa proto-Ret protein, although both proteins were expressed at similar levels in neuroblastoma cells.
The anti-RET antibodies were reactive with 64-kDa (p64ptc-1) and 81-kDa (p81ptc-2) proteins from lysates of ptc-1 and ptc-2 transformed cells, respectively, and identified two proteins of 140 kDa and 160 kDa from extracts of SK-N-SH, a neuroblastoma cell line previously shown to express two differently glycosylated forms of the normal RET product.
Identification and analysis of the ret proto-oncogene promoter region in neuroblastoma cell lines and medullary thyroid carcinomas from MEN2A patients.
Furthermore, the antibodies detected a unique 190 kd protein as well as 150 kd protein in a cell lysate from THP-1 human monocytic leukemia cell line, suggesting that glycosylated forms of the c-ret protein are different between neuroblastoma and leukemia cells.