Thyroid hormone receptor alpha 1 (c-erb A alpha 1) suppressed transforming phenotype of nasopharyngeal carcinoma cell line.

Only three thyroid hormone receptor (TR) isoforms, alpha 1, beta 1, and beta 2, bind thyroid hormone (TH) and are considered to be true TRs. TR alpha 2, unable to bind TH, binds to TH response element on DNA and has been shown to exert dominant negative action on TR alpha1. TR alphas regulate many important processes such as proliferation, differentiation and apoptosis. To find out if TR alphas played roles in growth control of nasopharyngeal carcinoma cells, transfectant with inducible expression of TR alpha 1 was generated from NPC-TW 04 cell lines. Induced expression of TR alpha 1 in nasopharyngeal carcinoma cell reduced proliferation and colony-formation ability in agar. Tumor formation ability in nude mice was reduced in NPC cells with TR alpha 1 expression than those without expression or vector-transfected cells. Our results supported the hypothesis that TR alpha 1 functions as a tumor suppressor gene in nasopharyngeal carcinoma tumorigenesis.