PTEN and neoplasm: Using a signature derived from single-cell analysis of transformed melanocytes in the BrafV600E; PTEN model [6], we confirmed decreased differentiation in VPr tumors (Extended Data Fig. 3a, b), indicating that chronic vemurafenib treatment reduces melanocyte marker gene expression heterogeneity either by directly impacting tumor cells or by enriching for a pre-existing cell state within the tumor.