Effect Of Butyric Acid On Immune Function Of Mice With Colorectal Cancer Liver Metastasis Implanted In Situ

Objective:To observe the effect of butyric acid on immune function and inflammatory response in mice with liver metastasis of colorectal cancer implanted in situ and to investigate the inhibitory effect of butyric acid on liver metastasis of colorectal cancer in mice and its possible mechanism.Methods:In order to build the orthotopic transplantation model of colorectal liver metastasis,60 male BALB/C mice were inoculated with exponentially growing 0.2 mL CT26 cells(1~*10~6)at the cecum wall under the serosa.Tumor bearing mice were divided into four groups with 15 mice of each,including the control group and three experimental groups,based on the randomized blocks method by weight right the third after the model-building surgery.The experimental groups were treated continuously with one dose daily by gavage of tributyrin of 0.3 g/(kg·d),1 g/(kg·d)and 3 g/(kg·d),respectively.The control group were treated of normal saline.All the tumor bearing mice were executed 40 days after treatment.The liver metastasis rate,thymus index,and spleen index of each mouse in four groups were calculated.The flow cytomertry was performed to detect the T lymphocyte subsets in the mouse peripheral blood,the neutral red intake assay to examine the phagocytic function of macrophages in spleen,the MTT assay to test the killing function of NK cell,and the ELISA method to test concentrations of IL-2,IL-10 and IL-12 in blood serum.The expressions of NF-?B,COX-2 and TNF-?mRNA and protein in mouse tumor tissues were detected by RT-PCR and Western Blot.Results:The liver metastasis rate was 30.77%for the control group,and the rate was 7.14%,0%,and 14.29%for the group of tributyrin with 0.3 g/(kg·d),1 g/(kg·d)and 3 g/(kg·d),respectively.Compared to the mice in control group,the liver metastasis for the mice treated of tributyrin was inhibited.The thymus index and spleen index for the mice in experimental groups were higher than those for the mice in control group(P<0.05).The CD3~+CD4~+T cell,CD3~+CD8~+T cell and CD3~+CD4~+/CD3~+CD8~+ratio in mouse peripheral blood for the mice treated of tributyrin were higher than those for the mice in control group(P<0.05).The NK cell killing function of experimental group mice was better than that of control group mice,while the difference was proved with no statistically significance(P>0.05).Compared to the mice in control group,the phagocytic function of macrophages was effectively enhanced for the mice treated of tributyrin of 0.3 g/(kg·d)and1 g/(kg·d)(P<0.05),and that was slightly better for the mice treated of tributyrin of 3g/(kg·d)with no statistically significance(P>0.05).The IL-2 and IL-12 concentration in blood serum was obviously higher for the experimental group mice than the control group mice.In the contrast,IL-10 concentration for the experimental group mice was quite lower than that for the control group mice with statically significant(P<0.05).Compared to the control group,the expression levels of NF-?B,COX-2 and TNF-?mRNA and protein in the butyric acid treatment group decreased(P<0.05).Among the above results,the effect of medium-dose butyric acid group was better than that of the other two groups.Conclusion:Butyric acid can inhibit liver metastasis of colorectal cancer in mice,its mechanism may be related to enhancing the immune function of mice.