Identification of differentially expressed genes of acute hypoxia-treated HepG2 cells and hypoxia-acclimatized HepG2 cells / 生理学报

To provide necessary information for further understanding of molecular mechanism of hypoxia acclimatization, the differentially expressed genes of HepG2 cells exposed to normoxia, acute hypoxia-treated cells which were exposed to 1% oxygen for 48 h, and hypoxia-acclimatized HepG2 cells which were cultured for 6 circles of alternate low oxygen (1% oxygen for 24 h) and normal oxygen (21% oxygen for 24 h), were identified respectively by combining the suppression subtractive hybridization (SSH) and cDNA microarray. Thirty-seven genes were expressed differentially in cells exposed to 1% oxygen for 48 h compared with those in cells exposed to normoxia. The expression of all these 37 genes was down-regulated, including the genes participating in cell cycle, cell response to stimulus, and cell signal transduction, and cell cytoskeleton formation, the genes associated with transcription and cell metabolism, 4 expressed sequence tags (ESTs), and 12 genes of which the functions are not known. There is a novel gene sequence, which has not been found in existing databases. There were only 6 genes differentially expressed in the hypoxia-acclimatized cells compared with cells exposed to normoxia, including two mitochondrion genes, metalloprotease-1 gene, ferritin gene, thymosin beta-4 and TPT1 genes. The expressions of mitochondrion ND4, ferritin, thymosin beta-4 and TPT1 were up-regulated, while the expressions of mitochondrion ND1 gene and metalloproease-1 gene were down-regulated. Cell tolerance to hypoxia increased after the cells were hypoxia-acclimatized. The different gene expression patterns of the acute hypoxia-treated cells and the hypoxia-acclimatized cells may be related to the increased tolerance of the cells to hypoxia.

Construction of subtracted cDNA libraries of gastrocarcinoma and normal tissue with suppression subtractive hybridization and their quality analysis / 军事医学科学院院刊

Objective: To construct subtracted cDNA libraries of stomach tumors and normal stomach tissue using suppression subtractive hybridization(SSH).Methods: cDNA Library subtraction was performed using the protocol described in the Clontech PCR-Select cDNA Subtraction Kit. cDNA was synthesized from 2 μg of poly A+RNA from the tumor and normal tissues using AMV reverse transcriptase. The tester and driver cDNAs were digested with RsaⅠ, a four-base-cutting restriction enzyme that yields blunt ends. The tester cDNA was then subdivided into two portions, and each was ligated with different cDNA adaptor. Two hybridizations were performed. In the first, an excess of driver was added to each sample of tester. Hybridization kinetics led to equalization and enrichment of differentially expressed sequences. During the second hybridization, the two primary hybridization samples were mixed together without denaturing and thus the templates were generated from differentially expressed sequences for PCR amplification. Using suppression PCR, only differentially expressed sequences were amplified exponentially and after second PCR amplification the background was reduced and differentially expressed sequences were further enriched. The cDNAs were then directly inserted into a T/A cloning vector to generate a stomach tumor-specific subtracted cDNA library. Results: The amplified library contained 800 positive clones. Plasmid inserts were PCR amplified and showed 250－700 bp inserts. Conclusions: The successfully constructed subtracted cDNA library of gastrocarcinoma and normal tissue enables us to compare two populations of mRNA and obtain clones of genes that expressed in one population but not in the other.The characterization of these genes will allow them to be exploited for their diagnostic and therapeutic potentials.