Primarily screening and analyzing ESTs differentially expressed in rats' primary liver cancer

Objective: To screen and analyze key express sequence tags (ESTs) which were differentially displayed in every period of SD rats' primary hepatic carcinoma and reveal the molecular mechanism of carcinogenesis. Methods: Using diethylnitrosamine (DENA) as a cancerigenic agent, animal models with different phases of primary hepatic cancer were constructed in SD rats. Rats were respectively sacrificed at d 14, d 28, d 56, d 77, d 105 and d 112 after the rats received DENA by gavage, then the livers were harvested. One part of the livers was classified according to their pathological changes, while the other was reserved for molecular mechanism studies on hepatocarcinogenesis. The differentially expressed genes were isolated from both normal and morbid tissues by mRNA differential display technique (DDRT-PCR). After the fragments were sequenced, bioinformatics were used to analyze the results. Results: Twelve differentially expressed cDNA fragments were obtained. Nine fragments had the homology with known cDNA clones, especially EST-7 was similar to BN/SsNHsdMCW mitochondrion gene and the identity was 100% which suggested EST-7 may be the part of BN/SsNHsdMCW mitochondrion gene. In contrast, other three fragments (EST-1, EST-3 and EST-5) had extremely low identity to any genes registered in GENBANK databases. Conclusions: BN/SsNHsdMCW mitochondrion gene was expressed in different periods of hepatocarcinogenesis. Moreover, EST-1, EST-3 and EST-5 were suggested to contribute to the development of rat hepatocarcinogenesis, and thus may be candidates of new targets of oncogenes or cancer suppressor genes.