Recently, a study by Péter Nagy's team [1] published in Cell Metabolism identified that the upregulation of cystathionine γ-lyase (CSE) and the inhibition of cystathionine β-synthase (CBS) are key factors contributing to the development of resistance to B-Raf proto-oncogene, serine/threonine kinase (BRAF) inhibitors (BRAFi) in treatment. Coadministration of the CSE inhibitor d,l-propargylglycine (PAG) with BRAFi significantly improved therapeutic efficacy and delayed the onset of resistance, offering a novel therapeutic strategy for patients with BRAF V600E-mutant (a valine-to-glutamic acid substitution at position 600 in the BRAF protein) melanoma.
Malignant melanoma is a highly aggressive tumor originating from melanocytes, with approximately 50% of patients harboring the BRAF V600E mutation [1]. This mutation leads to the activation of the downstream mitogen-activated protein kinase kinase/extracellular-signal-regulated kinase (MEK/ERK) signaling pathway, which in turn results in an increase in aerobic glycolysis, thereby supporting the proliferation of melanoma cells [2]. BRAF V600E inhibitors, such as vemurafenib (V) and dabrafenib (D), have been approved by the Food and Drug Administration (FDA) for the treatment of melanoma. However, resistance to these therapies often develops. Even when combining dabrafenib with the MEK inhibitor trametinib, resistance remains an inevitable challenge [3].
Existing research has indicated that treatment with dabrafenib-trametinib (DT) inhibits the BRAF/MEK/ERK pathway, leading to a shift in melanoma cell metabolism from aerobic glycolysis to mitochondrial respiration, which is unfavorable for melanoma cell proliferation [4]. Concurrently, the increased mitochondrial oxidative phosphorylation and electron transport chain (ETC) pathways result in enhanced reactive oxygen species (ROS) production. Excessive ROS production can disrupt the cellular redox balance and trigger oxidative stress responses. Building on this, the study discovered significant expression of cytochrome P (CYP)450 enzymes in dabrafenib- and trametinib-treated cells (DTC), with upregulation of CYP1B1 and CYP2F1 in dabrafenib- and trametinib-double resistant cells (DTR). These enzymes contribute to ROS production. To counteract the effects of ROS accumulation, antioxidant enzymes, such as superoxide dismutase 2 (SOD2), thioredoxin reductase 1 (TrxR1), catalase, 14-kDa human thioredoxin (Trx)-related protein (TRP14), glucose-6-phosphate dehydrogenase (G6PD), and glutathione (GSH) peroxidase 1 and 4 (GPX1, 4), are upregulated in DTC. However, this antioxidant response is limited, and the cells become more sensitive to exogenous oxidants, making them more susceptible to oxidative stress-induced damage. To support the function of antioxidant enzymes, DTC increasingly rely on the pentose phosphate pathway (PPP) to generate more nicoti
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