The PKR-Like Endoplasmic Reticulum Kinase Promotes the Dissemination of Myc-Induced Leukemic Cells

Low-dose metronomic chemotherapy triggers oxidized mtDNA sensing inside tumor cells to potentiate CD8+T anti-tumor immunity

Low-dose metronomic (LDM) chemotherapy, the frequent and continuous use of low doses of conventional chemotherapeutics, is emerging as a promising form of chemotherapy utilization. LDM chemotherapy exerts immunomodulatory effects. However, the underlying mechanism is not fully understood. Here we found that suppressing tumor growth by LDM chemotherapy was dependent on the activation of CD8+T cells. LDM chemotherapy potentiated the cytotoxic function of CD8+T cells by stimulating cancer-cell autonomous type I interferon (IFN) induction. Mechanistically, LDM chemotherapy evoked mitochondrial dysfunction and increased reactive oxygen species (ROS) production. ROS triggered the oxidation of cytosolic mtDNA, which was sensed by cGAS-STING, consequently inducing type I IFN production in the cancer cells. Moreover, the cGAS-STING-IFN axis increased PD-L1 expression and predicted favorable clinical responses to chemoimmunotherapy. Antioxidant N-acetylcysteine inhibited oxidized mtDNA-induced type I IFN production and attenuated the efficacy of combination therapy with LDM chemotherapy and PD-L1 blockade. This study elucidates the critical role of intratumoral oxidized mtDNA sensing in LDM chemotherapy-mediated activation of CD8+T cell immune response. These findings may provide new insights for designing combinatorial immunotherapy for cancer patients.

Enhanced IFN Sensing by Aggressive Chronic Lymphocytic Leukemia Cells

Type I IFN is made by cells in response to stress. Cancer cells exist in a state of stress, but their IFN response is complex and not completely understood. This study investigated the role of autocrine IFN in human chronic lymphocytic leukemia (CLL) cells. CLL cells were found to make low amounts of IFN via TANK-binding kinase 1 pathways, but p-STAT1 and -STAT2 proteins along with IFN-stimulated genes that reflect IFN activation were variably downregulated in cultured CLL cells by the neutralizing IFNAR1 Ab anifrolumab. Patients with CLL were segregated into two groups based on the response of their leukemia cells to anifrolumab. Samples associated with more aggressive clinical behavior indicated by unmutated IGHV genes along with high CD38 and p-Bruton’s tyrosine kinase expression exhibited responses to low amounts of IFN that were blocked by anifrolumab. Samples with more indolent behavior were unaffected by anifrolumab. Hypersensitivity to IFN was associated with higher expression of IFNAR1, MX1, STAT1, and STAT2 proteins and lower activity of negative regulatory tyrosine phosphatases. Autocrine IFN protected responsive CLL cells from stressful tissue culture environments and therapeutic drugs such as ibrutinib and venetoclax in vitro, in part by upregulating Mcl-1 expression. These findings suggest hypersensitivity to IFN may promote aggressive clinical behavior. Specific blockade of IFN signaling may improve outcomes for patients with CLL with higher-risk disease.

Decoding endoplasmic reticulum stress signals in cancer cells and antitumor immunity

The tumor microenvironment (TME) provokes endoplasmic reticulum (ER) stress in malignant cells and infiltrating immune populations. Sensing and responding to ER stress is coordinated by the unfolded protein response (UPR), an integrated signaling pathway governed by three ER stress sensors: activating transcription factor (ATF6), inositol-requiring enzyme 1α (IRE1α), and protein kinase R (PKR)-like ER kinase (PERK). Persistent UPR activation modulates malignant progression, tumor growth, metastasis, and protective antitumor immunity. Hence, therapies targeting ER stress signaling can be harnessed to elicit direct tumor killing and concomitant anticancer immunity. We highlight recent findings on the role of the ER stress responses in onco-immunology, with an emphasis on genetic vulnerabilities that render tumors highly sensitive to therapeutic UPR modulation.

Overexpression of HOXA10 is associated with unfavorable prognosis of acute myeloid leukemia

Background

HOXA family genes were crucial transcription factors involving cell proliferation and apoptosis. While few studies have focused on HOXA10 in AML. We aimed to investigate the prognostic significance of HOXA10.

Methods

We downloaded datasets from GEO and BeatAML database, to compare HOXA expression level between AML patients and controls. Kaplan-Meier curves were used to estimate the impact of HOXA10 expression on AML survival. The differentially expressed genes, miRNAs, lncRNAs and methylated regions between HOXA10-high and -low groups were obtained using R (version 3.6.0). Accordingly, the gene set enrichment analysis (GSEA) was accomplished using MSigDB database. Moreover, the regulatory TFs/microRNAs/lncRNAs of HOXA10 were identified. A LASSO-Cox model fitted OS to clinical and HOXA10-associated genetic variables by glmnet package.

Results

HOXA10 was overexpressed in AML patients than that in controls. The HOXA10-high group is significantly associated with shorter OS and DFS. A total of 1219 DEGs, 131 DEmiRs, 282 DElncRs were identified to be associated with HOXA10. GSEA revealed that 12 suppressed and 3 activated pathways in HOXA10-high group. Furthermore, the integrated regulatory network targeting HOXA10 was established. The LASSO-Cox model fitted OS to AML-survival risk scores, which included age, race, molecular risk, expression of IKZF2/LINC00649/LINC00839/FENDRR and has-miR-424-5p. The time dependent ROC indicated a satisfying AUC (1-year AUC 0.839, 3-year AUC 0.871 and 5-year AUC 0.813).

Conclusions

Our study identified HOXA10 overexpression as an adverse prognostic factor for AML. The LASSO-COX regression analysis revealed novel prediction model of OS with superior diagnostic utility.

Unfolded Protein Response in Leukemia: From Basic Understanding to Therapeutic Opportunities

Understanding genetic and epigenetic changes that underlie abnormal proliferation of hematopoietic stem and progenitor cells is critical for development of new approaches to monitor and treat leukemia. The unfolded protein response (UPR) is a conserved adaptive signaling pathway that governs protein folding, secretion, and energy production and serves to maintain protein homeostasis in various cellular compartments. Deregulated UPR signaling, which often occurs in hematopoietic stem cells and leukemia, defines the degree of cellular toxicity and perturbs protein homeostasis, and at the same time, offers a novel therapeutic target. Here, we review current knowledge related to altered UPR signaling in leukemia and highlight possible strategies for exploiting the UPR as treatment for this disease.