Gene Expression Differences Between Colon and Rectum Tumors
A partir de données portant sur 460 tumeurs du côlon et 100 tumeurs du rectum, cette étude analyse les différences d'expression de gènes en fonction de la localisation tumorale
BACKGROUND: Colorectal cancer studies typically include both colon and rectum tumors as a common entity, though this assumption is controversial and only minor differences have been reported at the molecular and epidemiological level. We performed a molecular study based on gene expression data of tumors from colon and rectum to assess de degree of similarity between these cancer sites at transcriptomic level. METHODS: A pooled analysis of 460 colon tumors and 100 rectum tumors from four datasets belonging to three independent studies was performed. Microsatellite instable tumors were excluded since these are known to have a different expression profile and have a preferential proximal colon location. Expression differences were assessed with linear models and significant genes were identified using adjustment for multiple comparisons. RESULTS: Minor differences at a gene expression level were found between tumors arising in the proximal colon, distal colon or rectum. Only several HOX genes were found to be associated with tumor location. More differences were found between proximal and distal colon that between distal colon and rectum. CONCLUSION: Microsatellite stable colorectal cancers do not show major transcriptomic differences for tumors arising in the colon or rectum. The small but consistent differences observed are largely driven by the HOX genes. These results may have important implications in the design and interpretation of studies in colorectal cancer.