Docosahexaenoic acid reverses PD-L1-mediated immune suppression by accelerating its ubiquitin-proteasome degradation

MEN1 deficiency stabilizes PD-L1 and promotes tumor immune evasion of lung cancer

Multiple Endocrine Neoplasia 1 gene (MEN1), which is known to be a tumor suppressor gene in lung tissues, encodes a 610 amino acid protein menin. Previous research has proven that MEN1 deficiency promotes the malignant progression of lung cancer. However, the biological role of this gene in the immune microenvironment of lung cancer remains unclear. In this study, we found that programmed cell death-ligand 1 (PD-L1) is upregulated in lung-specific KrasG12D mutation-induced lung adenocarcinoma in mice, after Men1 deficiency. Simultaneously, CD8+ and CD3+ T cells are depleted, and their cytotoxic effects are suppressed. In vitro, PD-L1 is inhibited by the overexpression of menin. Mechanistically, we found that MEN1 inactivation promotes the deubiquitinating activity of COP9 signalosome subunit 5 (CSN5) and subsequently increases the level of PD-L1.

Immunonutrition, Metabolism, and Programmed Cell Death in Lung Cancer: Translating Bench to Bedside

Lung cancer presents significant therapeutic challenges, motivating the exploration of novel treatment strategies. Programmed cell death (PCD) mechanisms, encompassing apoptosis, autophagy, and programmed necrosis, are pivotal in lung cancer pathogenesis and the treatment response. Dysregulation of these pathways contributes to tumor progression and therapy resistance. Immunonutrition, employing specific nutrients to modulate immune function, and metabolic reprogramming, a hallmark of cancer cells, offer promising avenues for intervention. Nutritional interventions, such as omega-3 fatty acids, exert modulatory effects on PCD pathways in cancer cells, while targeting metabolic pathways implicated in apoptosis regulation represents a compelling therapeutic approach. Clinical evidence supports the role of immunonutritional interventions, including omega-3 fatty acids, in augmenting PCD and enhancing treatment outcomes in patients with lung cancer. Furthermore, synthetic analogs of natural compounds, such as resveratrol, demonstrate promising anticancer properties by modulating apoptotic signaling pathways. This review underscores the convergence of immunonutrition, metabolism, and PCD pathways in lung cancer biology, emphasizing the potential for therapeutic exploration in this complex disease. Further elucidation of the specific molecular mechanisms governing these interactions is imperative for translating these findings into clinical practice and improving lung cancer management.

Beyond inhibition against the PD-1/PD-L1 pathway: development of PD-L1 inhibitors targeting internalization and degradation of PD-L1

Tumor cells hijack the programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) pathway to suppress the immune response through overexpressing PD-L1 to interact with PD-1 of T cells. With in-depth ongoing research, tumor-intrinsic PD-L1 is found to play important roles in tumor progression without interaction with PD-1 expressed on T cells, which provides an additional important target and therapeutic approach for development of PD-L1 inhibitors. Existing monoclonal antibody (mAb) drugs against the PD-1/PD-L1 pathway generally behave by conformationally blocking the interactions of PD-1 with PD-L1 on the cell surface. Beyond general inhibition of the protein-protein interaction (PPI), inhibitors targeting PD-L1 currently focus on the functional inhibition of the interaction between PD-1/PD-L1 and degradation of tumor-intrinsic PD-L1. This perspective will clarify the evolution of PD-L1 inhibitors and provide insights into the current development of PD-L1 inhibitors, especially targeting internalization and degradation of PD-L1.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

The interaction between programmed cell death ligand 1 (PD-L1), which is expressed on the surface of tumor cells, and programmed cell death 1 (PD-1), which is expressed on T cells, impedes the effective activation of tumor antigen-specific T cells, resulting in the evasion of tumor cells from immune-mediated killing. Blocking the PD-1/PD-L1 signaling pathway has been shown to be effective in preventing tumor immune evasion. PD-1/PD-L1 blocking antibodies have garnered significant attention in recent years within the field of tumor treatments, given the aforementioned mechanism. Furthermore, clinical research has substantiated the efficacy and safety of this immunotherapy across various tumors, offering renewed optimism for patients. However, challenges persist in anti-PD-1/PD-L1 therapies, marked by limited indications and the emergence of drug resistance. Consequently, identifying additional regulatory pathways and molecules associated with PD-1/PD-L1 and implementing judicious combined treatments are imperative for addressing the intricacies of tumor immune mechanisms. This review briefly outlines the structure of the PD-1/PD-L1 molecule, emphasizing the posttranslational modification regulatory mechanisms and related targets. Additionally, a comprehensive overview on the clinical research landscape concerning PD-1/PD-L1 post-translational modifications combined with PD-1/PD-L1 blocking antibodies to enhance outcomes for a broader spectrum of patients is presented based on foundational research.

Recent advances and mechanisms of action of PD-L1 degraders as potential therapeutic agents

PD-L1 is an important immune checkpoint protein that can bind to T cells' PD-1 receptor, thereby promoting immune escape from tumors. In recent years, many researchers have developed strategies to degrade PD-L1 to improve the effect of immunotherapy. The study of degrading PD-L1 provides new opportunities for immunotherapy. Here, we mainly summarize and review the current active molecules and mechanisms that mediate the degradation of immature and mature PD-L1 during the post-translational modification stages, involving PD-L1 phosphorylation, glycosylation, palmitoylation, ubiquitination, and the autophagy-lysosomal process. This review expects that by degrading PD-L1 protein, we will not only gain a better understanding of oncogenic mechanisms involving tumor PD-L1 protein but also provide a new way to improve immunotherapy.

Docosahexaenoic acid (DHA) impairs hypoxia-induced cellular and exosomal overexpression of immune-checkpoints and immunomodulatory molecules in different subtypes of breast cancer cells

BACKGROUND

Tumor cells express immune-checkpoint molecules to suppress anti-tumor immune responses. In part, immune evasion takes place by secreting exosomes bearing immune-checkpoint and immunomodulatory molecules and their inducing and/or regulating agents e.g., microRNAs (miRs). This study aimed to evaluate the effects of omega-3 fatty acid, docosahexaenoic acid (DHA), on the expression of some selected immune-checkpoint and immunomodulatory molecules and their regulating miRs under both normoxic and hypoxic conditions in triple negative (TNBC) invasive and triple positive non-invasive breast cancer cell lines.

METHODS

MDA-MB-231 and BT-474 cells were treated with 100 µM DHA under hypoxic and normoxic conditions for 24 h. Exosomes were isolated by ultracentrifuge and confirmed by electron microscope and anti-CD9, -CD63, -CD81 immunoblotting. Total RNA from cells and exosomes were extracted and expression of CD39, CD73, CD47, CD80, PD-L1, B7-H3, B7-H4 genes and their related miRs were evaluated by quantitative Real-time PCR.

RESULTS

This study showed significant over-expression of immune-checkpoint and immunomodulatory molecules under hypoxic condition. Treatment with DHA resulted in a significant decrease in immune-checkpoint and immunomodulatory molecule expression as well as an upregulation of their regulatory miRNA expression.

CONCLUSION

DHA supplementation may be utilized in breast cancer therapy for down-regulation of cellular and exosomal immune escape-related molecules.

Fatty acid synthase (FASN) signalome: A molecular guide for precision oncology

The initial excitement generated more than two decades ago by the discovery of drugs targeting fatty acid synthase (FASN)-catalyzed de novo lipogenesis for cancer therapy was short-lived. However, the advent of the first clinical-grade FASN inhibitor (TVB-2640; denifanstat), which is currently being studied in various phase II trials, and the exciting advances in understanding the FASN signalome are fueling a renewed interest in FASN-targeted strategies for the treatment and prevention of cancer. Here, we provide a detailed overview of how FASN can drive phenotypic plasticity and cell fate decisions, mitochondrial regulation of cell death, immune escape and organ-specific metastatic potential. We then present a variety of FASN-targeted therapeutic approaches that address the major challenges facing FASN therapy. These include limitations of current FASN inhibitors and the lack of precision tools to maximize the therapeutic potential of FASN inhibitors in the clinic. Rethinking the role of FASN as a signal transducer in cancer pathogenesis may provide molecularly driven strategies to optimize FASN as a long-awaited target for cancer therapeutics.

The implications of FASN in immune cell biology and related diseases

Fatty acid metabolism, particularly fatty acid synthesis, is a very important cellular physiological process in which nutrients are used for energy storage and biofilm synthesis. As a key enzyme in the fatty acid metabolism, fatty acid synthase (FASN) is receiving increasing attention. Although previous studies on FASN have mainly focused on various malignancies, many studies have recently reported that FASN regulates the survival, differentiation, and function of various immune cells, and subsequently participates in the occurrence and development of immune-related diseases. However, few studies to date systematically summarized the function and molecular mechanisms of FASN in immune cell biology and related diseases. In this review, we discuss the regulatory effect of FASN on immune cells, and the progress in research on the implications of FASN in immune-related diseases. Understanding the function of FASN in immune cell biology and related diseases can offer insights into novel treatment strategies for clinical diseases.

Soy isoflavone genistein attenuates the efficacy of immune checkpoint therapy in C57BL/6 mice inoculated with B16F1 melanoma and a high PD-L1 expression level reflects tumor resistance

Immune checkpoint therapy has been shown to be an effective therapy for many types of tumors. Much attention has been paid to the development of an effector target would be helpful for immune checkpoint therapy. Genistein has been shown to have an anti-tumor effect both in vitro and in vivo. In this study, we examined the effect of genistein on immune checkpoint blockade therapy against B16F1 melanoma tumors. Mice treated with genistein or anti-programmed death (PD)-1 antibody showed a significant decrease in tumor growth. However, treatment with genistein had no effect on or attenuated the efficacy of immune checkpoint therapy. The percentages of T cell receptor (TCR)β+CD4+ and TCRβ+CD8+ cells and the concentrations of interferon-γ and tumor necrosis factor-α in tumor tissue were not different among the experimental groups. A significant difference was also not found in microbe composition. Interestingly, a high expression level of PD-ligand (L)1 closely reflected the outcome of therapy by genistein or anti-PD-1 antibody. The study showed that a combination of genistein treatment does not improve the effect of immune blockade therapy. It also showed that a high PD-L1 expression level in tumors is a good prediction maker for the outcome of tumor therapy.