Tea polyphenols inhibit the proliferation, migration, and invasion of melanoma cells through the down-regulation of TLR4.

Melanoma is the most common skin cancer and malignant melanoma which can cause skin cancer-related deaths. Toll-like receptor 4 (TLR4) had been reported to play an important role in melanoma, and tea polyphenol (TP) is regarded as an anticancer substance. However, the relationship between TP and TLR4 in melanoma is not well explored. Therefore, our aim is to figure out how TP has an influence on melanoma. Melanoma cell lines (B16F10 and A375) were treated with TP and lipopolysaccharides (LPS). Western blot assay was used to examine TLR4 expression, and MTT assay was conducted to assess proliferation. Wound healing assay was conducted to evaluate the migration of melanoma cells, and transwell assay was used to examine the melanoma cells' invasiveness. Besides, in vivo experiments were practiced for TP function in mice with melanoma cells. TP inhibited the proliferation, migration and invasion ability of melanoma cells, which displayed a dosage and time dependence. TLR4 was highly expressed in melanoma cells compared with normal skin cells. TP could suppress TLR4 expression both in normal melanomas and in stimulated melanomas by TLR4 agonist LPS. Suppressing TLR4 in melanomas could inhibit cell function (proliferation, migration, and invasion), and blocking the expression of 67LR could abolish TP function on TLR4. TP can inhibit melanoma (B16F10) growth in vivo.