cDNA representational difference analysis of differentially expressed cDNAsequences in human nasopharyngeal carcinoma

Objective To search differentially expressed sequences correlated with path ogenesis of human nasopharyngeal carcinoma (NPC), including the candidates of tumor suppressor genes. Methods Representational difference analysis (RDA) was performed to isolate differentially expressed sequences between cDNA from normal human primary cultures of nasopharyngeal epithelial cells and cDNA from NPC cell line HNE 1. The source of differentially expressed products were proved by Southern blot, Northern blot and in situ hybridization. The fragments were cloned wi th pGEM-T easy kit and sequenced by the chain termination reaction. Results Four differentially expressed cDNA fragments were isolated in the f ourth subtractive hybridization using cDNA from normal human nasopharyngeal epithelial cells as tester amplicon and cDNA from NPC cell line HNE1 as dr iver amplicon by cDNA RDA. These differential cDNA fragments revealed that they really came from the tester amplicon and were not expressed or down-re gulated in the NPC HNE1 cells. Some of the genes were expressed only in hum an nasopharyngeal epithelial cells but deleted or downregulated in the biop sies of NPC. Of these obtained clones, some were the sequences of the human known genes including house-keeping genes, the others represented novel ge ne sequences. Conclusion The differentially expressed products including the candidates o f tumor-suppressor genes may be associated with the initiation of the NPC.