Urwyler, M. | bioRxiv Science

bioRxiv2025

Inhibition of 3-mercaptopyruvate sulfurtransferase enhances CD8⁺ T-cell antitumor immunity

Hydrogen sulfide (H2S) is a redox-active gasotransmitter implicated in tumor progression and immune regulation. The enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) is a key contributor to endogenous H2S and polysulfide production, but its role in tumor-immune interactions remains poorly defined. Here, we show that 3-MST is the most abundantly expressed H2S-synthesizing enzyme in human renal cell carcinoma cells (RCC) and that high 3-MST expression correlates with reduced patient survival. Pharmacological inhibition of 3-MST lowered intracellular H2S levels in Renca renal carcinoma cells, suppressed proliferation, induced apoptosis, and increased surface expression of the immunogenic markers CD70, CD86, and PD-L1. In immune cells, partial inhibition of 3-MST promoted T cell activation, as evidenced by increased CD69 expression on both CD4 helper and CD8 cytotoxic T cells. In contrast, complete inhibition of 3-MST, achieved by high concentrations of the inhibitor, modestly reduced CD8 T cell proliferation. Functionally, 3-MST inhibition potentiated antigen-specific CD8 T cell-mediated killing of tumor cells, an effect further amplified by PD-L1 blockade. These results establish 3-MST as a redox-sensitive metabolic driver of tumor growth and immune evasion in RCC and demonstrate that its inhibition can boost antitumor immune responses, offering a potential avenue for combination immunotherapy.

pharmacology and toxicology↗

bioRxiv2024

Selective molecular inhibition of the HDAC6 ZnF-UBP binding domain impairs multiple myeloma cell proliferation

Multiple myeloma is a plasma cell malignancy with poor prognosis despite the recent development of new therapeutic options. Histone deacetylase 6 (HDAC6) is overexpressed in multiple myeloma patients and may be involved in the acquisition of resistance to conventional anti-proteasome treatments. Beyond displaying a deacetylase catalytic activity, HDAC6 can recognize ubiquitinated motifs from misfolded proteins through its C-terminal ZnF-UBP binding domain and send the defective proteins to the aggresome for degradation. Here, we explore the role of the ZnF-UBP binding domain of HDAC6 in the function of multiple myeloma cells. A non-functional ZnF-UBP domain containing a 2-residue mutation in the binding site was designed and the absence of ubiquitin binding was confirmed in a cell-free assay. Molecular docking simulations and electrostatic calculations revealed a significant decrease in the electrostatic potential of the mutated peptide, which is crucial for the stability of the complex with ubiquitin. A multiple myeloma cell line containing the non-functional ZnF-UBP domain was then engineered. Although the deacetylase activity of HDAC6 was maintained in these cells, they showed reduced cell growth, impaired aggresome formation and a dysregulated gene expression profile that was more pronounced than cells entirely deficient in HDAC6. These results indicate that a non-functional ZnF-UBP binding domain impacts the function of multiple myeloma cells. Based on these findings, a series of quinazolinylpropanoic acid derivatives was synthesized to explore the inhibitory activity of small molecules to this domain. We propose that ZnF-UBP binding domain inhibitors should be further evaluated as potential therapeutic agents in multiple myeloma.

cancer biology↗