Hypoxia is a common phenomenon in solid tumors and is strongly linked to hallmarks of cancer. Recent evidence has shown that hypoxia promotes local immune suppression. Type I IFN supports cytotoxic T lymphocytes by stimulating the maturation of dendritic cells and enhancing their capacity to process and present antigens. However, little is known about the relationship between hypoxia and the type I IFN pathway, which comprises the sensing of double-stranded RNA and DNA (dsRNA/dsDNA) followed by IFNα/β secretion and transcriptional activation of IFN-stimulated genes (ISG). In this study, we determined the effects of hypoxia on the type I IFN pathway in breast cancer and the mechanisms involved. In cancer cell lines and xenograft models, mRNA and protein expressions of the type I IFN pathway were downregulated under hypoxic conditions. This pathway was suppressed at each level of signaling, from the dsRNA sensors RIG-I and MDA5, the adaptor MAVS, transcription factors IRF3, IRF7, and STAT1, and several ISG including RIG-I, IRF7, STAT1, and ADAR-p150. Importantly, IFN secretion was reduced under hypoxic conditions. HIF1α- and HIF2α-mediated regulation of gene expression did not explain most of the effects. However, ATAC-seq data revealed in hypoxia that peaks with STAT1 and IRF3 motifs had decreased accessibility. Collectively, these results indicate that hypoxia leads to an overall downregulation of the type I IFN pathway due to repressed transcription and lower chromatin accessibility in an HIF1/2α-independent manner, which could contribute to immunosuppression in hypoxic tumors. Significance: These findings characterize a new mechanism of immunosuppression by hypoxia via downregulation of the type I IFN pathway and its autocrine/paracrine effects on tumor growth.

B-cell lymphomas represent a diverse group of neoplasms classified primarily by histopatholgy and are often challenging to accurately diagnose. Despite having been recognized less than 20 years ago, microRNAs (miRNAs) have emerged as one of the most promising class of cancer molecular biomarkers and are particularly attractive as they can be readily detected in formalin-fixed paraffin-embedded biopsy material and biological fluids such as blood. Many of the identified B-cell lymphoma miRNA biomarkers also play crucial regulatory roles in normal B-cell development. Below we consider the identity, function, and biomarker potential of miRNAs in B-cell lymphoma and most importantly the barriers that remain to be overcome if they are really to become part of routine clinical practice.

The cellular response to hypoxia is driven by hypoxia-inducible factors (HIF), which regulate genes involved in glycolysis, angiogenesis, and cell proliferation, as well as inflammation and tumor progression. HIF activation is well characterized and is primarily regulated by oxygen-dependent prolyl hydroxylation and subsequent degradation. SET1B, a histone H3 lysine 4 methyltransferase, has recently emerged as a key modulator of HIF target gene transcription, but evidence suggests that it plays a broader role in modulating HIF transcriptional activity beyond histone methylation. In this study, we revealed that SET1B interacts with RNA polymerase II to coordinate sustained HIF-mediated transcriptional activity through multiple functional domains. In clear-cell renal cell carcinoma (ccRCC), SET1B is critical for sustained HIF activity, and SET1B expression correlated with disease progression and metastasis in patient samples. Moreover, SET1B depletion enhanced the efficacy of HIF2 inhibitors. These findings establish SET1B as a driver of tumor progression and potential therapeutic target in ccRCC. Significance: SET1B functions as a key regulator of HIF-dependent transcription and cancer growth under low-oxygen conditions, revealing a therapeutic target to enhance treatment efficacy and potentially slow disease progression in kidney cancer.