Objective: To study the expression of the gene and coding protein of catechol o-methyltransferase (COMT) in the colorectal cancer and distant normal mucosa.
Methods: The tumor tissues and distant normal mucosa of 22 patients with colorectal cancer received surgical treatment from January to August 2009 were collected. Total RNA and protein were extracted and tested using reverse transcription polymerase chain reaction (RT-PCR), Western blot was used to detect the expression of COMT in the tumor tissue and normal mucosa. Tissue array was performed to verify the COMT protein expression. The gray scale scan was used to differentiate the COMT expression level of the mRNA and protein between the two groups.
Results: The tested mean light density of COMT mRNA was 53 514 +/- 15 513 in the tumor tissue group and 4529 +/- 1698 in the normal mucosa group, the expression of COMT gene in colorectal cancer tissue was significantly higher than that in the normal mucosa (P < 0.05). Western blot results showed that the expression level of soluble COMT protein in the colorectal cancer tissue was significantly higher than that in the corresponding distant normal mucosa (mean light density 54 967 +/- 11 919 vs. 25 962 +/- 6713) (P < 0.05), but the expression of membrane-bound COMT protein was not statistically different between the two groups. Tissue array revealed that the COMT protein mainly located in the cytoplasm, and it was significantly over-expressed in the colorectal cancer tissue than in the normal mucosa (P < 0.05).
Conclusions: The COMT gene and encoding protein is over-expressed in the colorectal cancer tissue than in the distant normal mucosa. The COMT gene might be involved in the biological behavior of the colorectal cancer.