[A nasopharyngeal carcinoma negatively related EST on 7q32]

To isolate and clone the tumor suppressor gene on chromosomal region 7q32 that corelated with the occurrence of human NPC, we detected the genotype of polymorphic microsatellite markers on 7q32 in 24 nasopharyngeal carcinoma biopsies and matched normal lymphocyte DNA. LOH was found in 30% biopsies. Using differential RT-PCR and Northern hybridization we compared the expression level of 20 EST on 7q32 between NPC cell line HNE1 and primary culture of normal nasopharyngeal epithelial cell, and found AA070437 EST expressed high in primary culture of normal nasopharyngeal epithelial cell, but very low in HNE1. Differential RT-PCR (dRT-PCR) analysis showed that the expression level of AA070437 was lower in 30.7% NPC biopses than in normal cell. Differential PCR (dPCR) showed that allelic loss of AA070437 was observed in 29.1% NPC biopses. This EST is a part of sequence of a new gene compared with GeneBank database. Our results showed that AA070437 EST negatively related with the occurrence of human NPC is a candidate of tumor suppressor gene of NPC on 7q32.