The Inhibitory Effect Of L.paracasei Subp. Paracasei X12 Peptidoglycan On Tumor-bearing BALB/c Mice Andits Immune Mechanisms

Some drugs such as oxaliplatin can induce the immunogenic tumor cell death which can activate the immune system to kill cancer cells and avoid the damage brought by the traditional chemotherapy drugs and radiation, thus it is an important strategy to develop the novel active substance which can induce the immunogenic cell death to prevent cancers. In the previous studies, we found that L.paracasei subp. paracasei X12 peptidoglycan could induce the ICD, but it is not clear that whether the ICD induced by peptidoglycan can inhibit the cancer in vivo. In this study, we used the L.paracasei subp. paracasei X12 peptidoglycan to induce the ICD in murine colon carcinoma CT-26 cells, and then inoculated the cells into BALB/c mice subcutaneously, and injected the cells again on the other side of the line after 7 days, and then observed the growth of the tumors. In vitro, we used the human colon cells HT-29 as the study model to explore the mechanism at the molecular level. The main findings are as follows:(1) In this study, we used the TCA method to extract the L.paracasei subp. paracasei X12 peptidoglycan, and the extraction rate was 14.4%, and the ultraviolet-visible spectroscopy result determines its identity.(2) In this study, we determined the optimum dose(800 μg/m L) and time(48 h) of peptidoglycan by MTT. We found that the PG-induced ICD in CT-26 cells can prevent the immunocompetent BALB/c against tumor. The PG group performs better than the positive model group but is weaker than the OXP group in tumor growth and size, and all these results are consistent with the subsequent immunological parameters outcomes such as the IL-10、IL-12、IFN-γ、TNF-α.(3) In this study, we found that the PG(200-800 μg/m L) can induce the ICD marker CRT/ERp57 to expose on the cell surface and the HMGB1 to release outside the membrane. Besides, the m RNA expression of endoplasmic reticulum stress marker e IF2α, PERK and ATF6 treated by different concentrations of peptidoglycan all increased by using the RT-PCR technique, and the fluorescence didn’t find the exposure of CRT on the cell surface after adding the GSH.Conclusion: the L.paracasei subp. paracasei X12 can induce the ICD, and the mechanism is closely related with the regulation of ER. This study will provide the basic information for the development of paracasei peptidoglycan function and application.