CD40 and melanoma: To determine whether induction of CD40 expression was required for melanoma tumor cell response to RGS, we next knocked down the expression of CD40 in YUMM3.3 melanoma cells (CD40KD) by targeting either the coding sequence (CDS) or the 3′ untranslated region (UTR) to achieve ~ 60% knockdown of CD40 mRNA (Suppl.Fig. 11) and protein expression (Fig. 5 j).