The Action Of PARG Resulted In Immune Response Changes Of Localtumor In Metastasis Of Colon Carcinomaand Its Mechanism

Objective: To investigate the action of PARG resulted in immuneresponse changes of local tumor in metastasis of colon carcinoma and itspossible mechanism.Methods: Both the CT26cells without any treatment and CT26cellswhich were treated with Lentivirus empty vector served as control groupand CT26cells transfected with Lentivirus PARG-shRNA (Short hairpinRNA) served as experiment group. Animal models for liver metastases ofcolon carcinoma were established by splenic subcapsular inoculation oftumor cells in BALB/c mice. The changes of liver metastases carcinomanodules were observed and the alteration of survival times of mice bornetumor. The numbers of B220~+DEC205~+dendritic cell (B220~+DEC205~+DC)and CD11c~+CD11b~+dendritic cell (CD11c~+CD11b~+DC) in the spleen andliver were measured by immunofluorescence double labeling assay.CD4~+T cells and CD8~+T cells in the spleen and liver were tested byimmunofluorescence single staining. All of these cells were observed by confocal laser scanning microscope. The expression of PARG, PARP andnuclear factor-kappa B (NF-κB) proteins in spleen transplant tumor andliver metastases carcinoma were detected by Western blot. Enzyme-linkedimmunosorbent assay (ELISA) was used for detecting the levels of IL-10and TGF-β in serum and supernatant of tumor cells in three groups.Results: The numbers and grading of metastatic liver nodules inPARG-silenced group were obviously lower than that in the control groups(P<0.05）. The survival time of PARG-silenced group mice was clearlylonger than that in the control group (P<0.05). In PARG-silenced group,the numbers of B220~+DEC205~+DC were less and the amounts ofCD11c~+CD11b~+DC were more in spleen and liver than that in the controlgroup. The ratio of CD4~+/CD8~+in spleen and liver in PARG-silencedgroup was increased compared to that in the control group (P<0.05). Theexpressions of PARG, PARP and NF-κB in spleen transplant tumor andliver metastatic carcinoma were reduced and the levels of IL-10andTGF-β in serum and supernatant of tumor cells were decreased inPARG-silenced group compared to that in the untransfected group andempty vector control group (P<0.05).Conclusion: These studies proved that silencing PARG could restrainthe liver metastases of colon carcinoma, which is possibly bound up withthe following process where there is down-regulating of both PARP andNF-κB by PARG and then restraint of IL-10and TGF-β; finally, having the impact on the proliferation and differentiation of DC and T cells.