No abstract

SUMMARY Dendritic cells (DCs) orchestrate the initiation, programming, and regulation of anti-tumor immune responses. Emerging evidence indicates that the tumor microenvironment (TME) induces immune dysfunctional tumor-infiltrating DCs (TIDCs), characterized with both increased intracellular lipid content and mitochondrial respiration. The underlying mechanism, however, remains largely unclear. Here, we report that fatty acid-carrying tumor-derived exosomes (TDEs) induce immune dysfunctional DCs to promote immune evasion. Mechanistically, peroxisome proliferator activated receptor (PPAR) α responds to the fatty acids delivered by TDEs, resulting in excess lipid droplet biogenesis and enhanced fatty acid oxidation (FAO), culminating in a metabolic shift toward mitochondrial oxidative phosphorylation, which drives DC immune dysfunction. Genetic depletion or pharmacologic inhibition of PPARα effectively attenuates TDE-induced DC-based immune dysfunction and enhances the efficacy of immunotherapy. This work uncovers a role for TDE-mediated immune modulation in DCs and reveals that PPARα lies at the center of metabolic-immune regulation of DCs, suggesting a potential immunotherapeutic target.

Mitochondrial biogenesis is one of the generally accepted regulatory mechanisms in the heart under chronic hypoxia. The precise quantity and quality control of mitochondria is critical for the survival and function of cardiomyocytes. Mitochondrial autophagy, also known as mitophagy, which selectively eliminates dysfunctional and unwanted mitochondria, is the most important type of mitochondrial quality control. However, the detailed molecular mechanisms of mitophagy in cardiomyocytes have been largely undefined. The present study investigated the role of adenosine 5′-monophosphate-activated protein kinase (AMPK) in mitophagy regulation in cardiomyocytes under chronic hypoxia. H9c2 cells were cultured under hypoxic conditions (1% O2) for different time periods. Mitochondrial biogenesis was confirmed and hypoxia was found to induce the collapse of mitochondrial membrane potential (ΛΨm) and increase the number of dysfunctional mitochondria. As expected, mitochondrial autophagy was increased significantly in cardiomyocytes exposed to hypoxic conditions for 48 h. AMPK was activated under hypoxia. Notably, when the activation of AMPK was enhanced by the AMPK agonist AICAR, mitochondrial autophagy was increased accordingly. By contrast, when AMPK activation was blocked, mitochondrial autophagy was decreased and cardiomyocyte apoptosis was increased. In conclusion, in the present study, mitophagy was activated and played a crucial role in cardioprotection under chronic hypoxia. AMPK was involved in mitophagy regulation, thereby providing a potential therapeutic target for heart diseases associated with chronic hypoxia.

Microtubule-associated serine/threonine kinase 1 (MAST1) is a central driver of cisplatin resistance in human cancers. However, the molecular mechanism regulating MAST1 levels in cisplatin-resistant tumors is unknown. Through a proteomics screen, we identified the heat shock protein 90 B (hsp90B) chaperone as a direct MAST1 binding partner essential for its stabilization. Targeting hsp90B sensitized cancer cells to cisplatin predominantly through MAST1 destabilization. Mechanistically, interaction of hsp90B with MAST1 blocked ubiquitination of MAST1 at lysines 317 and 545 by the E3 ubiquitin ligase CHIP and prevented proteasomal degradation. The hsp90B-MAST1-CHIP signaling axis and its relationship with cisplatin response were clinically validated in cancer patients. Furthermore, combined treatment with a hsp90 inhibitor and the MAST1 inhibitor lestaurtinib further abrogated MAST1 activity and consequently enhanced cisplatin-induced tumor growth arrest in a patient-derived xenograft model. Our study not only uncovers the regulatory mechanism of MAST1 in tumors but also suggests a promising combinatorial therapy to overcome cisplatin resistance in human cancers.

Baduanjin significantly improved insomnia as measured by the PSQI; more well-designed trials are needed to determine the long-term effects.