TLR1 and melanoma: The TLR1/2 agonist Pam3CSK4 can promote the differentiation of monocytic MDSCs into M2-type macrophages with highly immunosuppressive functions in patients with colon, prostate, pancreas, or liver cancer (Wang et al., 2015); in melanoma, Pam3CSK4 upregulated the expression of PD-L1 (CD274) on immature myeloid cells (Fleming et al., 2019), in agreement to our findings presented here.