[Bone Morphogenetic Proteins from CT26 Regulate the Expression of PD-L1 in Murine Dendritic Cells and Macrophages].

OBJECTIVES: To analyze the influence of bone morphogenetic proteins (BMPs) from CT26 on PD-L1 of dendritic cells and macrophages.

METHODS: In vivo, we respectively inoculated CT26 colon cancer cells subcutaneously and intraperitoneally to BALB/c mice.The mice were randomly assigned to three groups and treated with normal saline; BMPs inhibitor LDN193189; BMPs inhibitor LDN193189 combined with paclitaxel, respectively. The treatments started on the eighth day after inoculating, when the tumor volume reached 150 mm3 or the abdominal circumference was greater than 6 cm. After 2 weeks of treatments, the mice were sacrificed.The counts of dendritic cells and macrophages and the expression of PD-L1 in tumors or ascites were detected by flow cytometry (FCM). In vivo, the dendritic cells and macrophages from normal BALB/c mice bone marrow were exposed to: no treatment; CT26 supernatant; CT26; CT26 supernatant and LDN193189; CT26 and LDN193189; CT26 supernatant, LDN193189 and paclitaxel; CT26, LDN193189 and paclitaxel. BMPs from CT26 was detected by ELISA.The counts of dendritic cells and macrophages and their PD-L1 expressions were detected by FCM. IRF-1 expression was detected by real-time (RT)-PCR and Western blot.

RESULTS: In vivo, LDN193189 treated mice had the greatest tumor size or abdominal circumference, with least dendritic cells andCM(155.3mm]macrophages and expressions of PD-L1. In vivo, ELISA test results showed that the concentration of BMPs in CT26 supernatant was (0.59±0.09) ng/mL. FCM, RT-PCR and Western blot showed that dendritic cells and macrophages exposed to CT26 supernatant and LDN193189 or CT26 and LDN193189 expressed the least PD-L1 and IRF-1, which was close to those without treatment. While added the PTX to the above treatment, the expressions of PD-L1 and IRF-1 increased in the test results.

CONCLUSIONS: BMPs from CT26 up-regulate the expression of PD-L1 in murine dendritic cells and macrophages.