Melanoma tumors exhibit a variable but distinct metabolic signature

The Warburg theory of cancer postulates that an important driver of tumorigenesis is insufficient respiration due to mitochondrial defects, and concomitant enhancement of lactate production due to increased aerobic glycolysis. We analysed 48 melanoma samples by immunohistochemistry and found that 38% of melanomas are characterized by areas of isolated or combined deficiencies of complexes of the oxidative phosphorylation (OXPHOS) system, whereby the incidence of OXPHOS-deficient areas is associated with an increased Breslow index; 62% of melanomas showed high expression of all OXPHOS complexes. Expression of carbonic anhydrase IX was low, indicating that melanomas generally are well-oxygenated. Expression of HIF-1α and MCT4 was high, which might be a consequence of increased lactate dehydrogenase A levels in melanomas. Our data indicate that there are two types of melanomas: one that features a classic Warburg effect, whereas the other one, despite being glycolytic, maintains a high level of OXPHOS complexes.