Detection of Differentially Expressed Genes in Esophageal Carcinoma Using Non-RI Differential Display with High Specificity

Differentially expressed genes in human esophageal carcinoma/normal tissue pairs were identified by means of a modified differential display technique to overcome the limitations of the conventional technique. Out of the eight cDNAs isolated, three were novel. The other five clones consisted of cDNA encoding cytokeratin 13, complement 7, KIAA1160, expression sequence tag (EST)-Hs110855 and EST-Hs13662. Quantitative reverse transcriptionPCR (RT-PCR) for 10 carcinoma/normal tissue pairs confirmed down-regulation of cytokeratin 13, complement 7 and KIAA1160 mRNAs in carcinoma tissue and up-regulation of EST-Hs110855 mRNA. EST-Hs13662 mRNA also seemed to increase in carcinoma tissues but not to a statistically significant extent. In situ hybridization confirmed that cytokeratin 13 mRNAs localized in differentiating keratinocytes of normal epithelia and had disappeared in carcinomas, suggesting that this down-regulation reflects de-differentiation during carcinogenesis. The functions of complement 7 and KIAA1160 mRNAs are unclear in normal tissue but their down-regulation in carcinoma tissue may help the development of esophageal carcinoma. The expression of EST-Hs110855 mRNA reportedly observed in carcinomas of different origins suggests that this EST is a carcinogenesis-related gene. Our modified technique, which eliminates the source of false-positives, reduces the screening time, and dispense with the radioisotope, was found to be useful for isolating differentially expressed genes from clinical specimens with apparently genetically distant cellular populations and a very limited mass.