Effect Of Microsatellite Instability On Immunological Microenvironment Of Colorectal Cancer

Objective:A new era of immunotherapies was unleashed in 2010 with the Food and Drug Administration (FDA) approval of the first therapeutic cancer vaccines. Current research has found that colorectal cancer patients respond inconsistently with this promising line of treatments. Recent findings have linked this phenomenon to the immune microenvironment of the tumors themselves; highlighting the important role with which specific immunol checkpoints may play in the tumor microenvironment. Our study aims to analyze the relationship between MSI (microsatillite instability) and the immune microenvironment in colorectal cancers which may provide guidance to clinical decisions of immunotherapies in patients with colorectal cancer.Methods:We include the patients diagnosed with colorecal cancers who have accepted the resection from 2014-11 to 2015-12 in Peking Union Hospital. All of the patients included have accepted the test of MMR protein expression through immuno histochemistry. We analyse the relation between microsatillite status and the clinical pathological characteristics, as well as the expression level of immunol checkpoints including PD-1、 PD-L1、IDO、CD8 through immuno histochemistryResults:. Compared to MSS group, MSI group intends to be located in the proxismal part of colon, larger tumor diameters, and TNM stageⅡ. Bisides, the expressions of PD-1 and PD-L1 on TIL(tumor infiltrating lymphcytes)are both uprugulated compared to MSS group, while the PD-L1 expression on tumor tissue is not. There are no prominant differences between IDO and CD8 expression levels.Conclusion:In our research we find that microsatellite status does influence immunol checkpoint expression leading to differentiated immunotherapy responses. Our results may provide basis on how to select the potential patients who may benefit from immunotherapies.