Abstract
Purpose:
CBLB502, an agonist of toll-like receptor 5, is a polypeptide drug derived from Salmonella flagellin that binds to Toll-like receptor 5 (TLR5) and activates nuclear factor-kB signaling, and has been shown to have an effect on several animal models of liver metastasis, regardless of TLR5 expression. In this study, we investigate whether CBLB502 can inhibit hepatic metastases in a mouse model with ocular melanoma.
Methods:
To know whether CBLB502 is able to activate TLR5 in melanoma cells, an in vitro P65 translocation response was checked. Mouse melanoma cell lines B16LS9 and Queens were cultured and treated with 100ng/ml of CBLB502 or 10ng/ml of TNF alpha or PBS for 30 minutes, fixed and stained with anti-P65 antibody, and the intracellular location of P65 were determined by confocal microscopy. B16LS9 cells were inoculated into the choroid of right eye in C57BL/6 mice. 40 mice were divided into 4 groups including a PBS control group (n=10), CBLB502 starting at the day before tumor inoculation (n=10), CBLB502 starting at the day of tumor inoculation (n=10), CBLB502 starting at 3 day after tumor inoculation (n=10). Each mouse received sc 1ug/100ul of CBLB502 or PBS every 3 days. The inoculated eye was removed at 7 day and checked tumor growth with histology methods. The liver was collected at 21 days and the number of metastasis were microscopically enumerated. IHC for S100 and CD49b was performed.
Results:
After CBLB502 or positive control TNF alpha treatment, P65 was observed to translocate from the cytoplasm to the nucleus in B16LS9 and Queens cells. Animal experiments showed that CBLB502 significantly decreased the number of hepatic metastasis in three treatment groups compared with the PBS group. S100 staining confirmed the metastases were from ocular melanoma. We observed CD49b+ cells in liver or hepatic metastases in the treatment groups but not in the control group.
Conclusions:
The agonist of toll-like receptor 5, CBLB502 is able to activate TLR5 in melanoma cells, and suppress hepatic metastasis from ocular melanoma in a mouse model through attracting natural killer cells to the liver. CBLB502 may be a potential treatment for metastastic uveal melanoma to the liver.
Keywords: 589 melanoma •
745 uvea