PRKD1 and metastatic melanoma: The comparison of the target spectrum of these two PKC inhibitors indicates that these observations are not the consequence of the inhibition of cPKCs, but identifies a novel serine/threonine kinase, i.e. PKCμ isoform (also known as PKD1), whose specific inhibition by shRNAs induces E-cadherin expression and reverses the metastatic phenotype in all metastatic melanoma cell lines tested.