DKK1 and ocular melanoma: Next, hPDLSCs pre-treated with IL-6 at 20 ng/mL were treated for 24 h with the inhibitors Dickkopf-1 (DKK1), SP600125, SB431542, and DAPT (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-s-phenylglycinet-butyl ester) specific to the canonical Wnt, non-canonical Wnt, TGF-β1, and Notch pathways, respectively, and then cultured in OM for 21 days (Fig. 5A).