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 α2 (TR-α2 or c-erb A-α2) was identified in NPC cell lines. Northern blot analysis using the 130 bp cDNA fragment and a TR-α2 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-α2 in NPC cell lines but not in normal nasal epithelial cells. RNA in situ hybridization was used to detect TR-α2 expression in clinical biopsies obtained from NPC patients and non-tumour controls. TR-α2 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-α2 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-α2 in the pathogenesis process of NPC was discussed. (C) 2000 Cancer Research Campaign.
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