Bromodomains and Extra-Terminal (BET) Inhibitor JQ1 Suppresses Proliferation of Acute Lymphocytic Leukemia by Inhibiting c-Myc-Mediated Glycolysis

Lactate Utilization Enables Metabolic Escape to Confer Resistance to BET Inhibition in Acute Myeloid Leukemia

Impairing the BET family coactivator BRD4 with small-molecule inhibitors (BETi) showed encouraging preclinical activity in treating acute myeloid leukemia (AML). However, dose-limiting toxicities and limited clinical activity dampened the enthusiasm for BETi as a single agent. BETi resistance in AML myeloblasts was found to correlate with maintaining mitochondrial respiration, suggesting that identifying the metabolic pathway sustaining mitochondrial integrity could help develop approaches to improve BETi efficacy. Herein, we demonstrated that mitochondria-associated lactate dehydrogenase allows AML myeloblasts to utilize lactate as a metabolic bypass to fuel mitochondrial respiration and maintain cellular viability. Pharmacologically and genetically impairing lactate utilization rendered resistant myeloblasts susceptible to BET inhibition. Low-dose combinations of BETi and oxamate, a lactate dehydrogenase inhibitor, reduced in vivo expansion of BETi-resistant AML in cell line and patient-derived murine models. These results elucidate how AML myeloblasts metabolically adapt to BETi by consuming lactate and demonstrate that combining BETi with inhibitors of lactate utilization may be useful in AML treatment.

SIGNIFICANCE

Lactate utilization allows AML myeloblasts to maintain metabolic integrity and circumvent antileukemic therapy, which supports testing of lactate utilization inhibitors in clinical settings to overcome BET inhibitor resistance in AML. See related commentary by Boët and Sarry, p. 950.

Co-overexpression of BRD4 and CDK7 promotes cell proliferation and predicts poor prognosis in HCC

Aberrant expression of critical components of the trans-acting super-enhancers (SE) complex contributes to the continuous and robust transcription of oncogenes in human cancers. Small-molecule inhibitors targeting core-transcriptional components such as transcriptional bromodomain protein 4 (BRD4) and cyclin-dependent kinase 7 (CDK7) have been developed and are currently undergoing preclinical and clinical testing in several malignant cancers. By analysis of TCGA data and clinical specimens, we demonstrated that BRD4 and CDK7 were frequently overexpressed in human HCCs and were associated with the poor prognosis. Shorter survival and poorly differentiated histology were linked to high BRD4 or CDK7 expression levels. Interestingly, co-overexpression of BRD4 and CDK7 was a more unfavorable prognostic factor in HCC. Treatment with JQ1 or THZ1 alone exhibited an inhibitory impact on the proliferation of HCC cells, while JQ1 synergized with THZ1 showed a more pronounced suppression. Concurrently, a combined JQ1 and THZ1 treatment abolished the transcription of oncogenes ETV4, MYC, NFE2L2. Our study suggested that BRD4 and CDK7 coupled can be a valuable biomarker in HCC diagnosis and the combination of JQ1 and THZ1 can be a promising therapeutic treatment against HCC.

Metabolic Reprogramming by Ribitol Expands the Therapeutic Window of BETi JQ1 against Breast Cancer

Many cancer patients still lack effective treatments, and pre-existing or acquired resistance limits the clinical benefit of even the most advanced medicines. Recently, much attention has been given to the role of metabolism in cancer, expanding from the Warburg effect to highlight unique patterns that, in turn, may improve diagnostic and therapeutic approaches. Our recent metabolomics study revealed that ribitol can alter glycolysis in breast cancer cells. In the current study, we investigate the combinatorial effects of ribitol with several other anticancer drugs (chrysin, lonidamine, GSK2837808A, CB-839, JQ1, and shikonin) in various breast cancer cells (MDA-MB-231, MCF-7, and T-47D). The combination of ribitol with JQ1 synergistically inhibited the proliferation and migration of breast cancer cells cell-type dependently, only observed in the triple-negative MDA-MB-231 breast cancer cells. This synergy is associated with the differential effects of the 2 compounds on expression of the genes involved in cell survival and death, specifically downregulation in c-Myc and other anti-apoptotic proteins (Bcl-2, Bcl-xL, Mcl-1), but upregulation in p53 and cytochrome C levels. Glycolysis is differentially altered, with significant downregulation of glucose-6-phosphate and lactate by ribitol and JQ1, respectively. The overall effect of the combined treatment on metabolism and apoptosis-related genes results in significant synergy in the inhibition of cell growth and induction of apoptosis. Given the fact that ribitol is a metabolite with limited side effects, a combined therapy is highly desirable with relative ease to apply in the clinic for treating an appropriate cancer population. Our results also emphasize that, similar to traditional drug development, the therapeutic potential of targeting metabolism for cancer treatment may only be achieved in combination with other drugs and requires the identification of a specific cancer population. The desire to apply metabolomic intervention to a large scope of cancer types may be one of the reasons identification of this class of drugs in a clinical trial setting has been delayed.

A Near-Infrared-II Fluorescent Nanocatalyst for Enhanced CAR T Cell Therapy against Solid Tumor by Immune Reprogramming

Chimeric antigen receptor (CAR) T cell therapy holds great promise in the treatment of hematological malignancies but performs poorly in solid tumors due to the tumor immunosuppressive microenvironment. Herein, a multifunctional nanocatalyst (APHA@CM) was prepared by encapsulating horseradish peroxidase (HRP)-loaded Au/polydopamine nanoparticles (Au/PDA NPs) and Ag₂S quantum dots with CAR T cell membranes to improve the CAR T cell therapy in solid tumors. The APHA@CM has excellent multimodal imaging capability to precisely guide the scope and time window for nanocatalyst-induced tumor microenvironment regulation and CAR T cell therapy. The oxidase-like activity of Au NPs inhibited the glycolytic metabolism of tumor cells, reducing lactate efflux, reprogramming tumor immunosuppression, and ultimately increasing CAR T cell activation within the tumors. Additionally, the hypoxia environment of tumors could be relieved by HRP to enhance the Au/PDA NPs-induced synergistic sonodynamic/photothermal therapy (SDT/PTT), thereby promoting the immunogenic cell death of NALM 6 cells and enhancing CAR T cell-mediated immune microenvironment reprogramming. When this strategy was utilized to treat NALM 6 solid tumors, it not only completely eliminated tumors but also formed a long-term immune memory effect to inhibit tumor metastasis and recurrence. This work offers a strategy for CAR T cell therapy in solid tumor.

Regulation of Cell Plasticity by Bromodomain and Extraterminal Domain (BET) Proteins: A New Perspective in Glioblastoma Therapy

BET proteins are a family of multifunctional epigenetic readers, mainly involved in transcriptional regulation through chromatin modelling. Transcriptome handling ability of BET proteins suggests a key role in the modulation of cell plasticity, both in fate decision and in lineage commitment during embryonic development and in pathogenic conditions, including cancerogenesis. Glioblastoma is the most aggressive form of glioma, characterized by a very poor prognosis despite the application of a multimodal therapy. Recently, new insights are emerging about the glioblastoma cellular origin, leading to the hypothesis that several putative mechanisms occur during gliomagenesis. Interestingly, epigenome dysregulation associated with loss of cellular identity and functions are emerging as crucial features of glioblastoma pathogenesis. Therefore, the emerging roles of BET protein in glioblastoma onco-biology and the compelling demand for more effective therapeutic strategies suggest that BET family members could be promising targets for translational breakthroughs in glioblastoma treatment. Primarily, “Reprogramming Therapy”, which is aimed at reverting the malignant phenotype, is now considered a promising strategy for GBM therapy.

A Comprehensive Review of BET Protein Biochemistry, Physiology, and Pathological Roles

Epigenetic modifications, specifically acetylation of histone plays a decisive role in gene regulation and transcription of normal cellular mechanisms and pathological conditions. The bromodomain and extraterminal (BET) proteins (BRD2, BRD3, BRD4, and BRDT), being epigenetic readers, ligate to acetylated regions of histone and synchronize gene transcription. BET proteins are crucial for normal cellular processing as they control cell cycle progression, neurogenesis, differentiation, and maturation of erythroids and spermatogenesis, etc. Research-based evidence indicated that BET proteins (mainly BRD4) are associated with numeral pathological ailments, including cancer, inflammation, infections, renal diseases, and cardiac diseases. To counter the BET protein-related pathological conditions, there are some BET inhibitors developed and also under development. BET proteins are a topic of most research nowadays. This review, provides an ephemeral but comprehensive knowledge about BET proteins’ basic structure, biochemistry, physiological roles, and pathological conditions in which the role of BETs have been proven. This review also highlights the current and future approaches to pledge BET protein-related pathologies.

Mechanisms of Immunosuppressive Tumor Evasion: Focus on Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a malignancy with high heterogeneity in its biological features and treatments. Although the overall survival (OS) of patients with ALL has recently improved considerably, owing to the application of conventional chemo-therapeutic agents, approximately 20% of the pediatric cases and 40-50% of the adult patients relapse during and after the treatment period. The potential mechanisms that cause relapse involve clonal evolution, innate and acquired chemoresistance, and the ability of ALL cells to escape the immune-suppressive tumor response. Currently, immunotherapy in combination with conventional treatment is used to enhance the immune response against tumor cells, thereby significantly improving the OS in patients with ALL. Therefore, understanding the mechanisms of immune evasion by leukemia cells could be useful for developing novel therapeutic strategies.