OBJECTIVETo explore the inhibitory effect of combined administration of bear bile powder (BBP) and cyclophosphamide (Cytoxan, CTX) on colorectal cancer liver metastasis by regulating tumor promotion inflammation microenvironment.

METHODThe CRC liver metastasis mode in mice was established through in situ spleenic injection of SL4 tumor cells into spleens. The mice were randomly divided into 5 groups: the model group, the CTX (80 mg x kg(-1)) treatment group, the CTX + BBP high dose (300 mg x kg(-1)) group, the CTX + BBP middle dose (150 mg x kg(-1)) group and the CTX + BBP low dose (75 mg x kg(-1)) group. Mice were orally administered with drugs for 12 days, and sacrificed on the 13'h day for weighing their spleens and lives, HE staining, and immunofluorescence analysis. Their peripheral blood, and metastatic tumor in spleens and lives were analyzed with flow cytometry.

RESULTSpleen and liver weights of the: CTX treatment group and other doses groups were significantly lower than that of the model group. HE staining and immunofluorescence analysis showed that lymphocyte infiltration was detected in normal tissues, and macrophages infiltration was observed around the tumor tissues. Flow cytometry analysis showed that the number of T-lymphocytes in peripheral blood of different doses groups were much higher than that of the CTX treatment group (P < 0.05), with the rise in the ratio of CD4/CD8; the total number of lymphocytes in spleen cell suspension increased in different doses groups, compared to the CTX treatment group, with notable increase in B cells (P < 0.05) and significant decrease in CD11b, F4/80 cells (P < 0.05). The combined treatment showed less monocyte macrophages in liver metastasis than that of the CTX treatment group.

CONCLUSIONThe combined treatment of bear bile powder and cyclophosphamide has the effect in not only protecting liver and increase immunity, but also in anti-inflammation and antitumor by regulating tumor microenvironment and reducing the collection of mononuclear macrophages. Particularly, the combined administration of low dose of bear bile powder and CTX shows the most significant effect in reducing inflammatory cell infiltration.