Protein kinase C delta regulates mononuclear phagocytes and hinders response to immunotherapy in cancer

Protein Kinase C δ: a critical hub regulating macrophage immunomodulatory functions during Mycobacterium tuberculosis infection

A host-modulating candidate gene involved in putative pathogen-killing pathways, with potential novel therapeutic intervention, Protein Kinase C - δ (PKCδ) has been recognized as a critical marker of inflammation with clinical and experimental evidence in recent years. Pulmonary microenvironment during Mtb infection is largely governed by lung resident macrophages, initiating innate and subsequent adaptive immune responses. We investigated the role of PKCδ in macrophages using a macrophage-specific PKCδ knockout mice model (LysMcrePKCδflox/flox). PKCδ deficiency in macrophages triggers an early lymphocytic immune response, increases neutrophil recruitment, and reduces inflammatory macrophages in the lungs, leading to higher Mtb burden and exacerbated pathology. Experimental and omics analysis further revealed that dysregulation of antimicrobial effector functions is detrimental to macrophage's ability to restrict bacterial growth in vitro. Importantly this defect was mitigated by exogenous GM-CSF supplementation and/or overexpressing PKCδ in macrophages. Thus, PKCδ plays a crucial role in immune modulation during Mtb infection with GM-CSF amongst several downstream pathways through which PKCδ exerts its regulatory effects.

Novel insights and an updated review of metabolic syndrome in immune-mediated organ transplant rejection

Metabolic syndrome (MetS) is a group of symptoms that are characterized by abnormal changes in metabolic substances such as glucose, lipids, proteins, and bile acids. MetS is a common complication after organ transplantation and can further affect the survival and physiological function of the graft by reprograming the patient's immune environment. Additionally, MetS can influence the occurrence of post-transplant complications, such as infections. In recent years, research into the epidemiology and mechanisms of MetS has grown significantly. In this review, we summarize the mechanisms of MetS after transplantation and the mechanisms of hyperglycemia, insulin resistance, hyperlipidemia, abnormal bile acids, and abnormal amino acids on the body's immune cells as related to the effect of metabolic disorders on immune rejection after liver, kidney, heart, skin and other organ transplantation. Finally, we provide an overview of current treatment strategies and offer insights into potential future therapies for managing MetS in transplant recipients.

Incretin triple agonist retatrutide (LY3437943) alleviates obesity-associated cancer progression

Medical therapeutics for weight loss are changing the landscape of obesity but impacts on obesity-associated cancer remain unclear. We report that in pre-clinical models with significant retatrutide (RETA, LY3437943)-induced weight loss, pancreatic cancer engraftment was reduced, tumor onset was delayed, and progression was attenuated resulting in a 14-fold reduction in tumor volume compared to only 4-fold reduction in single agonist semaglutide-treated mice. Despite weight re-gain after RETA withdrawal, the anti-tumor benefits of RETA persisted. Remarkably, RETA-induced protection extends to a lung cancer model with 50% reduced tumor engraftment, significantly delayed tumor onset, and mitigated tumor progression, with a 17-fold reduction in tumor volume compared to controls. RETA induced immune reprogramming systemically and in the tumor microenvironment with durable anti-tumor immunity evidenced by elevated circulating IL-6, increased antigen presenting cells, reduced immunosuppressive cells, and activation of pro-inflammatory pathways. In sum, our findings suggest that patients with RETA-mediated weight loss may also benefit from reduced cancer risk and improved outcomes.

FXR Agonism with Bile Acid Mimetic Reduces Pre-Clinical Triple-Negative Breast Cancer Burden

Bariatric surgery is associated with improved outcomes for several cancers, including breast cancer (BC), although the mechanisms mediating this protection are unknown. We hypothesized that elevated bile acid pools detected after bariatric surgery may be factors that contribute to improved BC outcomes. Patients with greater expression of the bile acid receptor FXR displayed improved survival in specific aggressive BC subtypes. FXR is a nuclear hormone receptor activated by primary bile acids. Therefore, we posited that activating FXR using an established FDA-approved agonist would induce anticancer effects. Using in vivo and in vitro approaches, we determined the anti-tumor potential of bile acid receptor agonism. Indeed, FXR agonism by the bile acid mimetic known commercially as Ocaliva ("OCA"), or Obeticholic acid (INT-747), significantly reduced BC progression and overall tumor burden in a pre-clinical model. The transcriptomic analysis of tumors in mice subjected to OCA treatment revealed differential gene expression patterns compared to vehicle controls. Notably, there was a significant down-regulation of the oncogenic transcription factor MAX (MYC-associated factor X), which interacts with the oncogene MYC. Gene set enrichment analysis (GSEA) further demonstrated a statistically significant downregulation of the Hallmark MYC-related gene set (MYC Target V1) following OCA treatment. In human and murine BC analyses in vitro, agonism of FXR significantly and dose-dependently inhibited proliferation, migration, and viability. In contrast, the synthetic agonism of another common bile acid receptor, the G protein-coupled bile acid receptor TGR5 (GPBAR1) which is mainly activated by secondary bile acids, failed to significantly alter cancer cell dynamics. In conclusion, agonism of FXR by primary bile acid memetic OCA yields potent anti-tumor effects potentially through inhibition of proliferation and migration and reduced cell viability. These findings suggest that FXR is a tumor suppressor gene with a high potential for use in personalized therapeutic strategies for individuals with BC.