Metabolic control of CD47 expression through LAT2-mediated amino acid uptake promotes tumor immune evasion

[Latest Findings on the Role of CD47 in Tumor Immune Evasion and Related Targeted Therapies]

CD47 is an immunoglobulin that is overexpressed on the surface of a variety of cancer cells. CD47 forms a signaling complex with signal regulatory protein alpha (SIRPα), prompting the escape of cancer cells from macrophage-mediated phagocytosis. In recent years, CD47 has been shown to be highly expressed in many types of solid tumors and is associated with poor prognosis in patients. More and more studies have shown that inhibition of the CD47-SIRPα signaling pathway can promote adaptive immune responses and enhance the phagocytosis of tumor cells by macrophages. Humanized anti-CD47 IgG4 monoclonal antibody has been studied in clinical trials for the treatment of a variety of advanced solid tumors and lymphomas, demonstrating a sound safety profile and achieving partial remission in some patients. In this review we discuss the structure and function of CD47 and the mechanism of CD47 regulation in tumors, summarize the research progress in therapeutic antibody drugs targeting CD47 and a bottleneck in research that targeted drugs are more prone to result in serious adverse effects, and evaluated the potential of the applying CD47-SIRPα signaling pathway in anti-cancer therapy.

Echinacea purpurea-derived homogeneous polysaccharide exerts anti-tumor efficacy via facilitating M1 macrophage polarization

Echinacea purpurea modulates tumor progression, but the underlying mechanism is poorly defined. We isolated and purified a novel homogeneous polysaccharide from E. purpurea (EPPA), which was shown to be an arabinogalactan with a mean molecular mass (Mr) of 3.8 × 10⁴ Da and with α- (1 → 5) -L-Arabinan as the backbone and α-L-Araf-(1→, →6)-β-D-Galp-(1→, and →4)-α-D-GalpA-(1→ as the side chains. Interestingly, oral administration of EPPA suppresses tumor progression in vivo and shapes the immune cell profile (e.g., facilitating M1 macrophages) in tumor microenvironment by single-cell RNA sequencing (scRNA-seq) analysis. More importantly, EPPA activates the inflammasome through a phagocytosis-dependent mechanism and rewires transcriptomic and metabolic profile, thereby potentiating M1 macrophage polarization. Collectively, we propose that EPPA supplementation could function as an adjuvant therapeutic strategy for tumor suppression.

Macrophage Repolarization as a Therapeutic Strategy for Osteosarcoma

Macrophages are versatile immune cells and can adapt to both external stimuli and their surrounding environment. Macrophages are categorized into two major categories; M1 macrophages release pro-inflammatory cytokines and produce protective responses that lead to antimicrobial or antitumor activity. M2 or tumor-associated macrophages (TAM) release anti-inflammatory cytokines that support tumor growth, invasion capacity, and metastatic potential. Since macrophages can be re-polarized from an M2 to an M1 phenotype with a variety of strategies, this has emerged as an innovative anti-cancer approach. Osteosarcoma (OS) is a kind of bone cancer and consists of a complex niche, and immunotherapy is not very effective. Therefore, immediate attention to new strategies is required. We incorporated the recent studies that have used M2-M1 repolarization strategies in the aspect of treating OS cancer.

Molecular mechanisms of osteosarcoma metastasis and possible treatment opportunities

In osteosarcoma patients, metastasis of the primary cancer is the leading cause of death. At present, management options to prevent metastasis are limited and non-curative. In this study, we review the current state of knowledge on the molecular mechanisms of metastasis and discuss promising new therapies to combat osteosarcoma metastasis. Genomic and epigenomic changes, metabolic reprogramming, transcription factors, dysregulation of physiologic pathways, and alterations to the tumor microenvironment are some of the changes reportedly involved in the regulation of osteosarcoma metastasis. Key factors within the tumor microenvironment include infiltrating lymphocytes, macrophages, cancer-associated fibroblasts, platelets, and extracellular components such as vesicles, proteins, and other secreted molecules. We conclude by discussing potential osteosarcoma-limiting agents and their clinical studies.