The CD47-SIRPα signaling axis as an innate immune checkpoint in cancer

Tumor-associated myeloid cells: new understandings on their metabolic regulation and their influence in cancer immunotherapy

Tumor-associated myeloid cells (TAMCs), mainly represented by tumor-associated macrophages and myeloid-derived suppressor cells, can promote tumor growth directly, by favoring tumor cell proliferation and survival, and indirectly, by creating an immunosuppressive microenvironment. Myeloid cells are characterized by an extreme phenotypical and functional plasticity. Immunometabolism is now emerging as a crucial aspect of TAMCs skewing toward pro-tumoral activities. The metabolic re-education of myeloid cells is a new strategy to boost their antitumor effector functions. Several anticancer therapies targeting TAMCs are already under investigation. Nowadays, the hot topic of cancer immunotherapy is represented by immune checkpoint inhibitors. These drugs unrestrain T-cell-mediated tumor elimination by removing suppressive signals delivered by tumor-associated cells. The efficacy of immune checkpoint blockade can be enhanced using coordinated strategies to counteract the TAMCs-dependent impairment of immune adaptive responses. In the first part of the review, we will describe the association between metabolic reprogramming and TAMCs biological activities. In the second part, we will illustrate the potential of combination therapies associating TAMC-targeting drugs with immune checkpoint inhibitors.

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

SIGNIFICANCE

In contrast to structural elements of the extracellular matrix, matricellular proteins appear transiently during development and injury responses, but their sustained expression can contribute to chronic disease. Through interactions with other matrix components and specific cell surface receptors, matricellular proteins regulate multiple signaling pathways, including those mediated by reactive oxygen and nitrogen species and H2S. Dysregulation of matricellular proteins contributes to the pathogenesis of vascular diseases and cancer. Defining the molecular mechanisms and receptors involved is revealing new therapeutic opportunities. Recent Advances: Thrombospondin-1 (TSP1) regulates NO, H2S, and superoxide production and signaling in several cell types. The TSP1 receptor CD47 plays a central role in inhibition of NO signaling, but other TSP1 receptors also modulate redox signaling. The matricellular protein CCN1 engages some of the same receptors to regulate redox signaling, and ADAMTS1 regulates NO signaling in Marfan syndrome. In addition to mediating matricellular protein signaling, redox signaling is emerging as an important pathway that controls the expression of several matricellular proteins.

CRITICAL ISSUES

Redox signaling remains unexplored for many matricellular proteins. Their interactions with multiple cellular receptors remains an obstacle to defining signaling mechanisms, but improved transgenic models could overcome this barrier.

FUTURE DIRECTIONS

Therapeutics targeting the TSP1 receptor CD47 may have beneficial effects for treating cardiovascular disease and cancer and have recently entered clinical trials. Biomarkers are needed to assess their effects on redox signaling in patients and to evaluate how these contribute to their therapeutic efficacy and potential side effects. Antioxid. Redox Signal. 27, 874-911.

How many diseases is triple negative breast cancer: the protagonism of the immune microenvironment

Triple negative breast cancer (TNBC) is a type of breast cancer (BC) that does not express the oestrogen and the progesterone receptors and the human epidermal growth factor receptor type 2 (HER2). Since there are no positive markers to reliably classify TNBC, these tumours are not yet treated with targeted therapies. Perhaps for this reason they are the most aggressive form of breast carcinomas. However, the clinical observation that these patients do not carry a uniformly dismal prognosis, coupled with data coming from pathology and epidemiology, suggests that this negative definition is not capturing a single clinical entity, but several. We critically evaluate this evidence in this paper, reviewing clinical and epidemiological data and new studies that aim to subclassify TNBC. Moreover, evidence on the role of tumour infiltrating lymphocytes (TILs) on TNBC progression, response to chemotherapy and patient outcome have been published. The heterogeneity, observed even at TILs level, highlights the idea that TNBC is much more than a single disease with a unique treatment. The exploration of the immune environment present at the tumour site could indeed help in answering the question 'How many diseases is TNBC' and will help to define prognosis and eventually develop new therapies, by stimulating the immune effector cells or by inhibiting immunological repressor molecules. In this review, we focus on the prospect of the patient's diverse immune signatures within the tumour as potential biomarkers and how they could be modulated to fight the disease.

Mithramycin-loaded mPEG-PLGA nanoparticles exert potent antitumor efficacy against pancreatic carcinoma

Previous studies have shown that mithramycin A (MIT) is a promising candidate for the treatment of pancreatic carcinoma through inhibiting transcription factor Sp1. However, systemic toxicities may limit its clinical application. Here, we report a rationally designed formulation of MIT-loaded nanoparticles (MIT-NPs) with a small size and sustained release for improved passive targeting and enhanced therapeutic efficacy. Nearly spherical MIT-NPs with a mean particle size of 25.0±4.6 nm were prepared by encapsulating MIT into methoxy poly(ethylene glycol)-block-poly(d,l-lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (NPs) with drug loading of 2.11%±0.51%. The in vitro release of the MIT-NPs lasted for >48 h with a sustained-release pattern. The cytotoxicity of MIT-NPs to human pancreatic cancer BxPC-3 and MIA Paca-2 cells was comparable to that of free MIT. Determined by flow cytometry and confocal microscopy, the NPs internalized into the cells quickly and efficiently, reaching the peak level at 1-2 h. In vivo fluorescence imaging showed that the prepared NPs were gradually accumulated in BxPC-3 and MIA Paca-2 xenografts and retained for 168 h. The fluorescence intensity in both BxPC-3 and MIA Paca-2 tumors was much stronger than that of various tested organs. Therapeutic efficacy was evaluated with the poorly permeable BxPC-3 pancreatic carcinoma xenograft model. At a well-tolerated dose of 2 mg/kg, MIT-NPs suppressed BxPC-3 tumor growth by 96%. Compared at an equivalent dose, MIT-NPs exerted significantly higher therapeutic effect than free MIT (86% versus 51%, P<0.01). Moreover, the treatment of MIT and MIT-NPs reduced the expression level of oncogene c-Myc regulated by Sp1, and notably, both of them decreased the protein level of CD47. In summary, the novel formulation of MIT-NPs shows highly therapeutic efficacy against pancreatic carcinoma xenograft. In addition, MIT-NPs can downregulate CD47 expression, implying that it might play a positive role in cancer immunotherapy.

Targeting CD47 Enhances the Efficacy of Anti-PD-1 and CTLA-4 in an Esophageal Squamous Cell Cancer Preclinical Model

Esophageal squamous cell cancer is a highly aggressive cancer with a dismal 5-year survival rate. CD47 is a cell transmembrane protein that is involved in cell apoptosis, proliferation, adhesion, migration, and antigen presentation in the immune system. By interacting with signal regulatory protein-α expressed in antigen-presenting cells (APCs), CD47 acts as an antiphagocytic mechanism to inhibit APC-dependent antigen presentation. Overexpression of CD47 was found in various types of cancer. However, its role in esophageal squamous cell cancer is not yet clear. Anti-CD47 is an antagonist of CD47 signaling pathways by competing with its ligand. In the current study, we investigated the effects of anti-CD47 treatment on the antitumor immune response in an esophageal squamous cell cancer preclinical model. We found that anti-CD47 treatment enhanced proinflammatory responses and increased CD8+ T-cell infiltration in tumor tissue in the animal model. T cells in anti-CD47-treated tumors showed higher PD-1 and CTLA-4 expression, indicating T-cell activation and the rationale of combining anti-CD47 with anti-PD-1 and CLTA-4. The combinatory treatment showed the best antitumor response, implying a novel treatment strategy. The effects of anti-CD47 depended on dendritic cell function. In patient samples, expression of CD47 was negatively correlated with CD8+ T-cell infiltration in esophageal squamous cell cancer patients. Taken together, CD47 might be a novel target to enhance anti-PD-1 and CLTA-4 efficacy in esophageal squamous cell cancer.