Nearly all melanoma patients with a BRAF‐activating mutation will develop resistance after an initial clinical benefit from BRAF inhibition (BRAFi).,The aim of this work is to evaluate whether metabolic imaging using hyperpolarized (HP) 13C pyruvate can serve as a metabolic marker of early response to BRAFi in melanoma, by exploiting the metabolic effects of BRAFi.,Mice bearing human melanoma xenografts were treated with the BRAFi vemurafenib or vehicle.,In vivo HP 13C magnetic resonance spectroscopy was performed at baseline and 24 hours after treatment to evaluate changes in pyruvate‐to‐lactate conversion.,Oxygen partial pressure was measured via electron paramagnetic resonance oximetry.,Ex vivo qRT‐PCR, immunohistochemistry and WB analysis were performed on tumour samples collected at the same time‐points selected for in vivo experiments.,Similar approaches were applied to evaluate the effect of BRAFi on sensitive and resistant melanoma cells in vitro, excluding the role of tumour microenvironment.,BRAF inhibition induced a significant increase in the HP pyruvate‐to‐lactate conversion in vivo, followed by a reduction of hypoxia.,Conversely, the conversion was inhibited in vitro, which was consistent with BRAFi‐mediated impairment of glycolysis.,The paradoxical increase of pyruvate‐to‐lactate conversion in vivo suggests that such conversion is highly influenced by the tumour microenvironment.
The importance of mitochondria as oxygen sensors as well as producers of ATP and reactive oxygen species (ROS) has recently become a focal point of cancer research.,However, in the case of melanoma, little information is available to what extent cellular bioenergetics processes contribute to the progression of the disease and related to it, whether oxidative phosphorylation (OXPHOS) has a prominent role in advanced melanoma.,In this study we demonstrate that compared to melanocytes, metastatic melanoma cells have elevated levels of OXPHOS.,Furthermore, treating metastatic melanoma cells with the drug, Elesclomol, which induces cancer cell apoptosis through oxidative stress, we document by way of stable isotope labeling with amino acids in cell culture (SILAC) that proteins participating in OXPHOS are downregulated.,We also provide evidence that melanoma cells with high levels of glycolysis are more resistant to Elesclomol.,We further show that Elesclomol upregulates hypoxia inducible factor 1-α (HIF-1α), and that prolonged exposure of melanoma cells to this drug leads to selection of melanoma cells with high levels of glycolysis.,Taken together, our findings suggest that molecular targeting of OXPHOS may have efficacy for advanced melanoma.