Sanchez, G. J. | Search bioRxiv

bioRxiv2026

PRDX6 Modulates Immune Checkpoint Inhibitor Response by Antagonizing Ferroptosis Induced By HDAC Inhibitors

Therapeutic resistance limits the efficacy of histone deacetylase (HDAC) inhibitors and immune checkpoint therapies in cancer. While HDAC inhibitors can induce ferroptosis, tumor cells often evade this cell death via antioxidant defenses. Here we identify peroxiredoxin 6 (PRDX6) as a critical modulator of resistance to HDAC inhibitor largazole by suppressing ferroptosis through its phospholipase A2 activity and maintaining GPX4 expression. Using genome-wide CRISPR activation screening, biochemical assays, and syngeneic tumor models, we show that PRDX6 depletion enhances largazole-induced lipid peroxidation, ferroptotic stress, and reshapes the tumor microenvironment to promote T-cell infiltration and inflammatory cytokine release. Importantly, combining PRDX6 knockdown with HDAC inhibition potentiates anti-PD-L1 immunotherapy efficacy and prolongs survival in vivo. These findings reveal PRDX6 as a redox gatekeeper linking ferroptosis resistance to immune evasion and suggest that co-targeting PRDX6 and HDAC pathways may improve responses to cancer immunotherapy.

cancer biology↗

bioRxiv2025

Histone Deacetylase Inhibitor Largazole Deactivates A Subset of Superenchancers and Causes Mitotic Chromosome Mis-alignment by Suppressing SP1 and BRD4

Histone deacetylase inhibitors have been investigated as potential therapeutic agents for cancer and other diseases. HDIs are known to promote histone acetylation, resulting in an open chromatin conformation and generally increased gene expression. In previous work, we reported that a subset of genes, particularly those regulated by superenhancers, can be suppressed by the HDAC inhibitor largazole. To elucidate the molecular mechanisms underlying gene repression by largazole, we conducted transposase-accessible chromatin sequencing, ChIP-seq, and RNA-seq studies. Our findings revealed that while largazole treatment generally enhances chromatin accessibility, it selectively decreases the accessibility of a subset of superenhancer regions. These genomic regions, showing the most significant changes in the presence of largazole, were enriched with transcription factor binding motifs for SP1, BRD4, CTCF, and YY1. ChIP-seq analysis confirmed reduced binding of BRD4 and SP1 at their respective sites on chromatin, particularly at superenhancers regulating genes such as ID1, c-Myc and MCMs. Largazole exerts its effects by inhibiting DNA replication, RNA processing, and cell cycle progression, partially through the suppression of SP1 expression. Depletion of SP1 by shRNA mimics several key biological effects of largazole and increases cellular sensitivity to the drug. Specific to cell cycle regulation, we demonstrated that largazole disrupts G/M transition by interfering with chromosome alignment during metaphase, a phenotype also observed with SP1 depletion. Our results suggest that largazole exerts its growth-inhibitory effect by suppressing BRD4 and SP1 at super-enhancers, leading to cytostatic responses and mitotic dysfunction.

cancer biology↗