Purpose: Leukemic stem cells (LSC) are responsible for leukemia initiation, relapse, and therapeutic resistance. Therefore, the development of novel therapeutic approaches targeting LSCs is urgently needed for patients with acute myeloid leukemia (AML). Experimental Design: The LSC-like cell lines (KG-1α and Kasumi-1) and CD34+ primary AML cells purified from patients with AML (n = 23) treated with CS055 and/or chiglitazar and were analyzed for viability, death, and colony formation assay. We performed RNA sequencing, glutamate release, intracellular glutathione, lipid reactive oxygen species, transmission electron microscopy, and Western blotting assay and confirmed ferroptosis in LSC-like cells. The luciferase reporter, co-immunoprecipitation, histone deacetylase 3 (HDAC3)-shRNA/HDAC3/deacetylase-deficient LSC-like cell lines, histidine pull-down, and chromatin immunoprecipitation assays performed to clarify the molecular mechanism of CS055/chiglitazar in LSC-like cells. We also established cell-derived xenograft and patient-derived xenograft mouse models to evaluate the therapeutic efficacy of CS055/chiglitazar against AML in vivo. Results: We report that the HDAC inhibitor CS055, in combination with peroxisome proliferator–activated receptor pan-agonist (chiglitazar), synergistically targets leukemic stem-like cells from leukemia cell lines and patient samples while sparing normal hematopoietic progenitor cells. Mechanistically, chiglitazar enhances the inhibitory effect of CS055 on HDAC3 and induces ferroptosis in LSC-like cells by downregulating the expression of ferroptosis suppressor SLC7A11. In fact, the inhibition of HDAC3 increases H3K27AC levels in the promoter region of activating transcription factor 3 (ATF3), a transcriptional repressor of the SLC7A11 gene, and upregulates the expression of ATF3. In contrast, ATF4, a SLC7A11 activator, is suppressed by HDAC3 inhibition. Conclusions: Our findings suggest that treatment with CS055 combined with chiglitazar will target LSCs by inducing ferroptosis and may confer an effective approach for the treatment of AML.

Transformed follicular lymphoma (t-FL), for which there is no efficient treatment strategy, has a rapid progression, treatment resistance, and poor prognosis, which are the main reasons for FL treatment failure. In this study, we identified a promising therapeutic approach with chiauranib, a novel orally developed multitarget inhibitor targeting VEGFR/Aurora B/CSF-1R. We first determined the cytotoxicity of chiauranib in t-FL cell lines through CCK-8, EdU staining, flow cytometry, and transwell assays. We also determined the killing effect of chiauranib in a xenograft model. More importantly, we identified the underlying mechanism of chiauranib in t-FL tumorigenesis by immunofluorescence and Western blotting. Treatment with chiauranib significantly inhibited cell growth and migration, promoted apoptosis, induced cell cycle arrest in G2/M phase, and resulted in significant killing in vivo. Mechanistically, chiauranib suppresses the phosphorylation level of VEGFR2, which has an anti-t-FL effect by inhibiting the downstream MEK/ERK/STAT3 signaling cascade. In conclusion, chiauranib may be a potential therapy to treat t-FL, since it inhibits tumor growth and migration and induces apoptosis by altering the VEGFR2/ERK/STAT3 signaling pathway.

Persistence of leukemic stem cells (LSCs) is one of the determining factors to acute myeloid leukemia (AML) treatment failure and responsible for the poor prognosis of the disease. Hence, novel therapeutic strategies that target LSCs are crucial for treatment success. We investigated if targeting Bcl-2 and peroxisome proliferator activated receptor α (PPARα), two distinct cell survival regulating mechanisms could eliminate LSCs. This study demonstrate that the Bcl-2 inhibitor venetoclax combined with the PPARα agonist chiglitazar resulted in synergistic killing of LSC-like cell lines and CD34⁺ primary AML cells while sparing their normal counterparts. Furthermore, the combination regimen significantly suppressed AML progression in patient-derived xenograft (PDX) mouse models. Mechanistically, chiglitazar-mediated PPARα activation inhibited the transcriptional activity of the PIK3AP1 gene promoter and down-regulated the PI3K/Akt signaling pathway and anti-apoptotic Bcl-2 proteins, leading to cell proliferation inhibition and apoptosis induction, which was synergized with venetoclax. These findings suggest that combinatorial Bcl-2 inhibition and PPARα activation selectively eliminates AML cells in vivo and vitro, representing an effective therapy for patients with relapsed and refractory AML.

Background: Group 2 innate lymphoid cells (ILC2s) are critical sources of type 2 cytokines and represent one of the major tissue-resident lymphoid cells in the mouse lung. However, the molecular mechanisms underlying ILC2 activation under challenges are not fully understood. Results: Here, using single-cell transcriptomics, genetic reporters, and gene knockouts, we identify four ILC2 subsets, including two non-activation subsets and two activation subsets, in the mouse acute inflammatory lung. Of note, a distinct activation subset, marked by the transcription factor Nr4a1, paradoxically expresses both tissue-resident memory T cell (Trm), and effector/central memory T cell (Tem/Tcm) signature genes, as well as higher scores of proliferation, activation, and wound healing, all driven by its particular regulons. Furthermore, we demonstrate that the Nr4a1⁺ILC2s are restrained from activating by the programmed cell death protein-1 (PD-1), which negatively modulates their activation-related regulons. PD-1 deficiency places the non-activation ILC2s in a state that is prone to activation, resulting in Nr4a1⁺ILC2 differentiation through different activation trajectories. Loss of PD-1 also leads to the expansion of Nr4a1⁺ILC2s by the increase of their proliferation ability. Conclusions: The findings show that activated ILC2s are a heterogenous population encompassing distinct subsets that have different propensities, and therefore provide an opportunity to explore PD-1's role in modulating the activity of ILC2s for disease prevention and therapy.

Acute myeloid leukemia (AML) is a highly heterogeneous malignancy with immunosuppressive tumor microenvironment (TME), which contributes to the development of drug resistance and poor outcomes of immune therapy in AML patients. Therefore, it is imperative to unveil the mechanisms underlying immune suppression in AML TME and identify novel therapeutic targets for immunotherapy. Here, our study identified two immune-related subtypes via RNA-seq analysis, with Cluster 2 significantly associated with multiple biological characteristics and clinical phenotypes, including patients' age, survival and mutational burden. Meanwhile, differential analysis revealed 397 upregulated genes, 75 downregulated genes and 87 prognosis-related differentially expressed genes (DEGs) between Cluster 1 and Cluster 2. Subsequently, LSP1 was identified as the most significant prognostic marker for AML patients. Furthermore, we found that LSP1 expression was significantly correlated with patients' age, class and prognosis and notably affected the cytotoxicity of sorafenib against AML cells. Finally, scRNA-seq analysis revealed a significant correlation between LSP1 and the expression of immune checkpoint molecules in CD8⁺ T cells and AML cells, influencing the function of total CD8⁺ T cells as well as CD8⁺ Teff and CD8⁺ Tem cells. Collectively, our study revealed that LSP1 is an immune-related marker that greatly correlated with the prognosis, multiple clinical features and biological characteristics of AML patients. Meanwhile, the effects of LSP1 on sorafenib sensitivity and CD8⁺ T cell apoptosis were also unveiled, shedding light on LSP1 as a promising therapeutic target for AML.