In humans, the cytosolic glutathione S-transferase (GST) family of proteins is encoded by 16 genes presented in seven different classes. GSTs exhibit remarkable structural similarity with some overlapping functionalities. As a primary function, GSTs play a putative role in Phase II metabolism by protecting living cells against a wide variety of toxic molecules by conjugating them with the tripeptide glutathione. This conjugation reaction is extended to forming redox sensitive post-translational modifications on proteins: S-glutathionylation. Apart from these catalytic functions, specific GSTs are involved in the regulation of stress-induced signaling pathways that govern cell proliferation and apoptosis. Recently, studies on the effects of GST genetic polymorphisms on COVID-19 disease development revealed that the individuals with higher numbers of risk-associated genotypes showed higher risk of COVID-19 prevalence and severity. Furthermore, overexpression of GSTs in many tumors is frequently associated with drug resistance phenotypes. These functional properties make these proteins promising targets for therapeutics, and a number of GST inhibitors have progressed in clinical trials for the treatment of cancer and other diseases.

Melanoma is a highly aggressive and metabolically adaptable cancer that often resists conventional therapies. Targeting core bioenergetic pathways may, therefore, represent an effective strategy to improve therapeutic responses, particularly in tumors dependent on mitochondrial function. SC18 is an imidazolidine-2,4-dione compound that binds the NADH-binding pocket of voltage-dependent anion channels (VDACs), inducing mitochondrial dysfunction. VDAC expression is increased in melanoma and strongly associated with advanced disease stage and poor prognosis. In this study, we evaluated the effects of SC18 in melanoma cell lines with distinct pigmentation states, including melanin-rich melanotic human MNT-1 and mouse B16-F1, as well as low/amelanotic human SKMel28 and mouse YUMM cells. VDAC1, VDAC2 and VDAC3 were highly expressed across these melanoma lines, all of which relied on both glycolysis and mitochondrial oxidative phosphorylation for ATP production. SC18 reduced mitochondrial membrane potential and oxygen consumption rates, accompanied by declines in intracellular ATP levels and TCA cycle substrate utilization. SC18 also increased reactive oxygen species, mitochondrial superoxide, and lipid peroxidation, indicating enhanced oxidative stress. These metabolic and redox disturbances were associated with reduced cell viability and significantly impaired migration in multiple melanoma cell lines, supporting a potential anti-metastatic effect. In addition, SC18 showed synergistic cytotoxicity when combined with other chemotherapeutic agents. Overall, SC18 disrupted mitochondrial metabolism, induced oxidative stress, and impaired survival and motility pathways, with more pronounced effects in low/amelanotic than in melanotic melanoma cells. Together, these findings support the further development of SC18 as a mitochondrial metabolic disruptor that targets redox vulnerabilities in melanoma.

Voltage dependent anion channels (VDACs 1, 2 and 3) in the outer mitochondrial membrane control the flux of anions and oxidizable substrates that sustain mitochondrial metabolism. NADH closes VDAC by binding to a pocket, conserved in all isoforms, located in the inner wall of the channel. Previously, we identified the small molecule SC18 that targets the NADH-binding pocket of VDAC1 employing computational analysis. Here, we explored the interaction between SC18 and VDAC1 using High-resolution Nuclear Magnetic Resonance spectroscopy and Molecular Dynamics simulations. Atomically resolved data precisely confirmed the computational results, showing that SC18 binds to a site on VDAC1 that partially overlaps with the NADH binding pocket. SC18, in the presence of NADH blocked the conductance of VDAC1 reconstituted in lipid bilayers. To determine the metabolic effect of SC18, we combined readouts of mitochondrial metabolism and glycolysis with functional metabolomics and proteomics. Short-term treatment with SC18 inhibited mitochondrial metabolism and ATP production. Treatment over 24 h and 48 h further reduced mitochondrial uptake of pyruvate and glutamine, utilization of tricarboxylic acid cycle intermediates, as well as lipid, DNA and amino acid synthesis. Concomitant with the inhibition of mitochondrial metabolism, cellular uptake of glucose and glutamine increased in parallel with augmented lactate release. These results indicate that compensatory enhanced glycolysis sustains ATP production after impaired mitochondrial function induced by SC18 blockage of VDAC1. Our work set a mechanistic foundation for VDAC1 inhibition as a novel strategy to target and reprogram cancer metabolism through modulation of the biosynthetic ability of mitochondria.

Extracellular vesicles (EVs) carry surface proteins that reflect the molecular signatures of their originating cells. However, their low abundance and the modest sensitivity of current EV detection methods in complex biological environments limit access to EV surface biology in the native biological context. Here, we present a near‐infrared optical nanosensor comprising a quantum well defect functionalized carbon nanotube coupled with integrin‐recognition RGD tripeptide to detect surface integrins on EVs in a human plasma background. The nanosensor achieved sub‐picomolar detection of three integrin subunits (α5β1, αVβ1, and αVβ3) and quantified glioblastoma, ovarian cancer, and fibroblast‐derived EVs at concentrations as low as 10 ⁴ EVs·mL ⁻¹ . Molecular dynamics simulations indicated that the RGD‐coupled quantum defect stably engages the canonical integrin‐binding pocket, localizing the binding event at the defect site and providing a structural basis for the selective response. Interestingly, the nanosensor detected comparable responses from fibroblast‐ and cancer‐derived EVs, and the finding was independently validated by surfaceome proteomics, which confirmed that RGD‐receptor integrins are present at comparable levels across all three EV populations. Our result indicates that RGD‐receptor integrins define a broadly distributed adhesion‐associated EV phenotype shared between cancer and stromal cell types, with implications for EV‐mediated tumor‐stromal interactions.