PMEL and cancer: Cells in cluster 5 had lower expression of SOX10 and PMEL but high expression of the GLUT1 glucose transporter, NQO1 (NAD(P)H quinone oxidoreductase 1), and COX4 (a mitochondrial cytochrome c oxidase); all three proteins are associated with a metabolically active state and in some cases metastasis and poor prognosis (Fig. 6c, d).(30,31) These cells were primarily found adjacent to necrotic regions, which represents a hypoxic environment sometimes associated with increased cancer aggressiveness (Fig. 6e, f).(32)