Leukemia stem cells (LSC) possess distinct self-renewal and arrested differentiation properties that are responsible for disease emergence, therapy failure, and recurrence in acute myeloid leukemia (AML). Despite AML displaying extensive biological and clinical heterogeneity, LSC with high interleukin-3 receptor (IL3R) levels are a constant yet puzzling feature, as this receptor lacks tyrosine kinase activity. Here, we show that the heterodimeric IL3Rα/βc receptor assembles into hexamers and dodecamers through a unique interface in the 3D structure, where high IL3Rα/βc ratios bias hexamer formation. Importantly, receptor stoichiometry is clinically relevant as it varies across the individual cells in the AML hierarchy, in which high IL3Rα/βc ratios in LSCs drive hexamer-mediated stemness programs and poor patient survival, while low ratios mediate differentiation. Our study establishes a new paradigm in which alternative cytokine receptor stoichiometries differentially regulate cell fate, a signaling mechanism that may be generalizable to other transformed cellular hierarchies and of potential therapeutic significance.
Stemness is a hallmark of many cancers and is largely responsible for disease emergence, progression, and relapse. Our finding that clinically significant stemness programs in AML are directly regulated by different stoichiometries of cytokine receptors represents a hitherto unexplained mechanism underlying cell-fate decisions in cancer stem cell hierarchies. This article is highlighted in the In This Issue feature, p. 1749.
©2023 The Authors; Published by the American Association for Cancer Research.

Rotavirus (RV) is the leading cause of acute gastroenteritis and watery diarrhea in children under 5 years accounting for high morbidity and mortality in countries with poor socioeconomic status. Although vaccination against RV has been implemented in more than 100 countries, the efficacy of vaccine has been challenged in low-income settings. The lack of any FDA-approved drug against RV is an additional concern regarding the treatment associated with rotavirus-induced infantile death. With the purpose for the discovery of anti-RV therapeutics, we assessed anti-rotaviral potential of quercetin, a well-characterized antioxidant flavonoid. In vitro study revealed that quercetin treatment resulted in diminished production of RV-SA11 (simian strain) viral particles in a concentration-dependent manner as estimated by the plaque assay. Consistent with this result, Western blot analysis also revealed reduced synthesis of viral protein in quercetin-treated RV-SA11-infected MA104 cells compared to vehicle (DMSO) treated controls. Not surprisingly, infection of other RV strains A5-13 (bovine strain) and Wa (Human strain) was also found to be abridged in the presence of quercetin compared to DMSO. The IC50 of quercetin against three RV strains ranges between 2.79 and 4.36 Mm, and S.I. index is greater than 45. Concurrent to the in vitro results, in vivo study in mice model also demonstrated reduced expression of viral proteins and viral titer in the small intestine of quercetin-treated infected mice compared to vehicle-treated infected mice. Furthermore, the result suggested anti-rotaviral activity of quercetin to be interferon-independent. Mechanistic study revealed that the antiviral action of quercetin is co-related with the inhibition of RV-induced early activation of NF-κB pathway. Overall, this study delineates the strong anti-RV potential of quercetin and also proposes it as future therapeutics against rotaviral diarrhea.
Copyright © 2022 Banerjee, Sarkar, Mukherjee, Miyoshi, Kitahara, Halder, Koley and Chawla-Sarkar.

Tyrosine kinase inhibitors (TKIs) have dramatically improved the survival in chronic myeloid leukemia (CML), but residual disease typically persists even after prolonged treatment. Several lines of evidence suggest that TKIs administered to CML patients upregulate interferon γ (IFNγ) production, which may counteract the anti-tumorigenic effects of the therapy. We now show that activated T cell-conditioned medium (TCM) enhanced proliferation and counteracted imatinib-induced apoptosis of CML cells, and addition of a neutralizing anti-IFNγ antibody at least partially inhibited the anti-apoptotic effect. Likewise, recombinant IFNγ also reduced imatinib-induced apoptosis of CML cells. This anti-apoptotic effect of IFNγ was independent of alternative IFNγ signaling pathways, but could be notably diminished by STAT1-knockdown. Furthermore, IFNγ upregulated the expression of several anti-apoptotic proteins, including MCL1, PARP9, and PARP14, both in untreated and imatinib-treated primary human CD34+ CML stem/progenitor cells. Our results suggest that activated T cells in imatinib-treated CML patients can directly rescue CML cells from imatinib-induced apoptosis at least partially through the secretion of IFNγ, which exerts a rapid, STAT1-dependent anti-apoptotic effect potentially through the simultaneous upregulation of several key hematopoietic survival factors. These mechanisms may have a major clinical impact, when targeting residual leukemic stem/progenitor cells in CML.
© 2022 The Author(s). Published with license by Taylor & Francis Group, LLC.

Interferon gamma (IFNγ) is a pro-inflammatory cytokine that directly activates the JAK/STAT pathway. However, the temporal dynamics of chromatin remodeling and transcriptional activation initiated by IFNγ have not been systematically profiled in an unbiased manner. Herein, we integrated transcriptomic and epigenomic profiling to characterize the acute epigenetic changes induced by IFNγ stimulation in a murine breast cancer model.
We identified de novo activation of cis-regulatory elements bound by Irf1 that were characterized by increased chromatin accessibility, differential usage of pro-inflammatory enhancers, and downstream recruitment of BET proteins and RNA polymerase II. To functionally validate this hierarchical model of IFNγ-driven transcription, we applied selective antagonists of histone acetyltransferases P300/CBP or acetyl-lysine readers of the BET family. This highlighted that histone acetylation is an antecedent event in IFNγ-driven transcription, whereby targeting of P300/CBP acetyltransferase activity but not BET inhibition could curtail the epigenetic remodeling induced by IFNγ through suppression of Irf1 transactivation.
These data highlight the ability for epigenetic therapies to reprogram pro-inflammatory gene expression, which may have therapeutic implications for anti-tumor immunity and inflammatory diseases.
© 2022. The Author(s).

Toll-like receptor 8 (TLR8) recognizes single-stranded RNA of viral and bacterial origin as well as mediates the secretion of pro-inflammatory cytokines and type I interferons by human monocytes and macrophages. TLR8, as other endosomal TLRs, utilizes the MyD88 adaptor protein for initiation of signaling from endosomes. Here, we addressed the potential role of the Toll-interleukin 1 receptor domain-containing adaptor protein (TIRAP) in the regulation of TLR8 signaling in human primary monocyte-derived macrophages (MDMs). To accomplish this, we performed TIRAP gene silencing, followed by the stimulation of cells with synthetic ligands or live bacteria. Cytokine-gene expression and secretion were analyzed by quantitative PCR or Bioplex assays, respectively, while nuclear translocation of transcription factors was addressed by immunofluorescence and imaging, as well as by cell fractionation and immunoblotting. Immunoprecipitation and Akt inhibitors were also used to dissect the signaling mechanisms. Overall, we show that TIRAP is recruited to the TLR8 Myddosome signaling complex, where TIRAP contributes to Akt-kinase activation and the nuclear translocation of interferon regulatory factor 5 (IRF5). Recruitment of TIRAP to the TLR8 signaling complex promotes the expression and secretion of the IRF5-dependent cytokines IFNβ and IL-12p70 as well as, to a lesser degree, TNF. These findings reveal a new and unconventional role of TIRAP in innate immune defense.