Expression changes of cell-cell adhesion-related genes in colorectal tumors

Epithelial tissues achieve a highly organized structure due to cell-cell junction complexes. Carcinogenesis is accompanied by changes in cell interactions and tissue morphology, which appear in the early stages of benign tumors and progress along with invasive potential. The aim of the present study was to analyze the changes in expression levels of genes encoding intercellular junction proteins that have been previously identified to be differentially expressed in colorectal tumors compared with normal mucosa samples (fold change, >2.5) in genome-wide expression profiling. The expression of 20 selected genes was assessed using quantitative reverse transcription polymerase chain reaction in 26 colorectal cancer, 42 adenoma and 24 normal mucosa samples. Between these tissue types, differences were observed in the mRNA levels of genes encoding adherens junction proteins (upregulation of CDH3 and CDH11, and downregulation of CDH19 and PTPRF), tight junction proteins (upregulation of CLDN1 and CLDN2, and downregulation of CLDN5, CLDN8, CLDN23, CLDN15, JAM2 and CGN) and desmosomes (upregulation of DSC3 and DSG3, and downregulation of DSC2), in addition to a decrease in the expression of certain other genes involved in intercellular connections: PCDHB14, PCDH7, MUPCDH and NEO1. The differences between tissue types were statistically significant, and separate clustering of normal adenoma and carcinoma samples was observed in a hierarchical clustering analysis. These results indicate that the morphological changes in neoplastic colon tissue that occur during the 'adenoma-carcinoma sequence' are accompanied by specific changes in the expression of multiple genes encoding the majority of cell-cell junction complexes. The particular differential expression patterns appear to be consistent among patients with cancer and adenoma, in addition to normal mucosa samples.