Gene expression profiling of colorectal normal mucosa, adenoma and adenocarcinoma tissues

Approximately two decades ago, Vogelstein and Fearon proposed the adenoma-carcinoma sequence of sporadic CRC development and illustrated the accumulation of genetic alterations during the stepwise progression, thereby providing a guideline for clinical practice. Although the detection and excision of precancerous lesions could prevent colorectal cancer and reduce mortality, 6% of adenomas will ultimately develop into colorectal cancer. Thus, this genetic model for colorectal tumorigenesis may not completely reflect the complex essence of the disease and whether the mode of initiation of the events in the multistep progression affects the outcome of CRC is still unknown. In this study, mRNA and miRNA expression profiling was performed with human colorectal tissues, including normal mucosa, adenoma and adenocarcinoma. Then, an integrated approach was adopted to establish the regulatory interaction networks that were correlated with colorectal carcinogenesis. Finally, a 55-gene signature whose expression was down-regulated in precancerous lesions compared to normal tissue was identified as a potential early indicator of CRC survival. The results suggested that genes related to immunity and homeostasis played a critical role in protection against adenoma initiation and that the altered molecular events that influence colorectal cancer prognosis may be set in an early, precancerous stage. Four types of human colorectal tissues were selected by colonoscopic resection or colorectal surgery, including 12 normal mucosae, 21 low-grade adenomas (mild or moderate atypical hyperplasia), 30 high-grade adenomas (severe atypical hyperplasia or carcinoma in situ) and 25 adenocarcinomas. Gene expression profiling analysis of these samples was performed using Agilent 4x44K human whole genome gene expression microarray (G4112F).