ABSTRACT
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.