Elevated expression of thyroid hormone receptor alpha 2 (c-erb A- alpha 2) in nasopharyngeal carcinoma

Differential display was used to identify genes differentially expressed between cultured normal nasal epithelial cells and nasopharyngeal carcinoma (NPC) cell lines. A 130 bp cDNA fragment showing homology with thyroid hormone receptor alpha2 (TR-alpha2 or c-erb A-alpha2) was identified in NPC cell lines. Northern blot analysis using the 130 bp cDNA fragment and a TR-alpha2 specific cDNA containing part of the coding region as probes, we were able to detect a 2.7 kb transcript corresponding to that of TR-alpha2 in NPC cell lines but not in normal nasal epithelial cells. RNA in situ hybridization was used to detect TR-alpha2 expression in clinical biopsies obtained from NPC patients and non-tumour controls. TR-alpha2 mRNA was detected in 1 out of 24 (4.2%) normal nasopharynx epithelium biopsies, in 5 out of 27 (18.5%) primary and 15 out of 24 (62.5%) recurrent tumours. The positive rate of TR-alpha2 expression in recurrent NPC biopsies was significantly higher than that in normal nasopharynx epithelium (P<0.00001). The relevance of the elevated expression of TR-alpha2 in the pathogenesis process of NPC was discussed.