Cell culture
The murine B16 melanoma cell line was purchased from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China). The B16 cells were cultured in HG-DMEM (Gibco Life Technologies, Waltham, MA, USA). Wnt3a was added (2 ng/mL) to the media, followed by supplementation with 10% FBS (BI, Biological Industries), penicillin G (100 U/mL), and streptomycin (100 µg/mL) (Gibco-BRL, Grand Island, NY, USA). The cells were maintained in a humidified incubator under 5% CO2 at 37 °C, and they were sub-cultured every 2 days to maintain logarithmic growth.