The Expression Of DGAT1and FAAH And Their Clinical Significances In Colorectal Cancer

Colorectal cancer is one of the most common malignant tumors, ranking fourth infrequency in China. With the change of the dietary constituents and environment, theincidence rates have increased year after year. Tumor proliferation and invasion are criticalfactors that affect the prognosis of cancer patients. To improve the prognosis of cancerpatients, it has clinic importance to investigate the mechanisms of tumor proliferation andinvasion.The increase of de novo fatty acid synthesis has been confirmed as a commonphenomenon of many malignancies, including breast, prostate and colorectal cancer. As animportant organelle in lipid metabolism，lipid droplet has been found in various tumor cellssuch as colorectal cancer cells with an increasing quantity, which is related to manybiological behaviors such as tumor invasiveness. Diacylglycerol acyltransferase-1(DGAT1)is a key enzyme for the synthesis of lipid droplets, however, the expression status as well asthe biological actions of DGAT1in colorectal cancer have not been reported.The changes of lipid metabolism in cancer cells include alterations of various enzymes.Anandamide (AEA) and2-arachidonoylglycerol (2-AG) are two lipids that inhibitproliferation of cancer cells, which are inactivated through fatty acid amide hydrolase(FAAH). he expression status of FAAH in colorectal cancer have not been reported.This work was aimed to investigate the expressions of DGAT1and FAAH in colorectalcancer which influence the proliferation and invasion of cancer cells during the process oflipid metabolism, and to analyze the relationship between these two enzymes and clinicalparameters, which may offer some hints for further research on cancer therapy.Objective: To observe the expressions of DGAT1and FAAH in colorectal cancer andnormal intestinal mucosa, explore its clinical significance, and investigate the influence ofinhibiting DGAT1activity on invasion and migration of colon cancer cells.Methods: Colorectal cancer tissues, corresponding normal intestinal mucosa as well as 6colon cancer cell lines (HT-29、CaCo2、SW-480、SW-620、HCT-116and LoVo) were used.This work includes three parts.Part Ⅰ: To investigate the expression status of DGAT1in colorectal cancer cell linesand colorectal cancer tissues, and the relationship between DGAT1expressions and clinicalparameters in colorectal cancer patients. The mRNA and protein levels of DGAT1inHT-29、CaCo2、SW-480、SW-620、HCT-116and LoVo cell lines were determined byRealtimePCR and western blot, respectively. In addition, immunohistochemical assay ofDGAT1expression in tissue microarray composed of103colorectal cancer tissues and38normal intestinal mucosa was carried out, followed the analyses of the relationship betweenDGAT1expressions and clinical parameters in tumor patients.Part Ⅱ: To add DGAT1inhibitor to colon cancer cell lines HT-29, HCT-116, SW-480,and observe the changes of migration and invasion ability.Part Ⅲ: To investigate the relationship between FAAH protein expression in colorectalcancer tissues and clinical parameters. Immunohistochemical assay of FAAH expression intissue microarray composed of169colorectal cancer tissues and38normal intestinalmucosa was carried out, followed the analyses of the relationship between FAAHexpressions and clinical parameters in tumor patients.Results:1. DGAT1was highly expressed in aggressive colon cancer cell line HT-29, with arelative low-expression status in non-aggressive colon cancer cell lines like CaCo2andSW-480. Compared to normal intestinal mucosa, DGAT1was highly expressed incolorectal cancer tissues (77.7%vs.44.7%, P<0.01). Additionally, the expression status ofDGAT1was correlated with tumor grade (P<0.01).2. After DGAT1inhibitor treatment, the migration abilities of HT-29、HCT-116、SW-480cell were decreased. HT-29, with the highest expression of DGAT1, was observedto be inhibited at the most remarkable ratio. Moreover, the HT-29invasiveness was alsosuppressed.3. The expression of FAAH in colorectal cancer was lower than that in normalintestinal mucosa. Compared to normal intestinal mucosa, FAAH was lowly expressed incolorectal cancer tissues (56.8%vs.97.4%, P<0.001). Additionally, the expression status ofFAAH was correlated with tumor grade (P<0.01). Conclusion:1. The expression level of DGAT1is significantly difference between colorectal cancerand normal intestinal mucosa, and the expression status of DGAT1is correlated with tumorgrade. The expression status of DGAT1in aggressive colon cancer cell line HT-29is higherthan non-aggressive cell lines, which implies that DGAT1may play critical role in invasionand progression of colorectal cancer.2. The migration and invasion ability of colon cell lines can be inhibited by DGAT1inhibitor, which demonstrates that DGAT1facilitates the migration and invasion ofcolorectal cancer.3. The expression level of FAAH is significantly difference between colorectal cancerand normal intestinal mucosa, and the expression status of FAAH is correlated with tumorgrade. FAAH may play important role in proliferation of colorectal cancer.