Evolutionarily conserved resistance to phagocytosis observed in melanoma cells is insensitive to upregulation of pro-phagocytic signals and to CD47 blockade

Modulating macrophage-mediated programmed cell removal: An attractive strategy for cancer therapy

Macrophage-mediated programmed cell removal (PrCR) is crucial for the identification and elimination of needless cells that maintain tissue homeostasis. The efficacy of PrCR depends on the balance between pro-phagocytic "eat me" signals and anti-phagocytic "don't eat me" signals. Recently, a growing number of studies have shown that tumourigenesis and progression are closely associated with PrCR. In the tumour microenvironment, PrCR activated by the "eat me" signal is counterbalanced by the "don't eat me" signal of CD47/SIRPα, resulting in tumour immune escape. Therefore, targeting exciting "eat me" signalling while simultaneously suppressing "don't eat me" signalling and eventually inducing macrophages to produce effective PrCR will be a very attractive antitumour strategy. Here, we comprehensively review the functions of PrCR-activating signal molecules (CRT, PS, Annexin1, SLAMF7) and PrCR-inhibiting signal molecules (CD47/SIRPα, MHC-I/LILRB1, CD24/Siglec-10, SLAMF3, SLAMF4, PD-1/PD-L1, CD31, GD2, VCAM1), the interactions between these molecules, and Warburg effect. In addition, we highlight the molecular regulatory mechanisms that affect immune system function by exciting or suppressing PrCR. Finally, we review the research advances in tumour therapy by activating PrCR and discuss the challenges and potential solutions to smooth the way for tumour treatment strategies that target PrCR.

An "All-In-One" Immunomodulator-Engineered Clinical Translatable Immunotherapy of Advanced Hepatocellular Carcinoma

Clinical treatment of advanced hepatocellular carcinoma (HCC) remains a significant challenge. Utilizing 1-bromoacetyl-3,3-dinitroazetidine (RRx-001) to downregulate the expression of innate immune checkpoint molecule, cluster of differentiation 47 (CD47), provides a powerful means for treating advanced HCC containing abundant immunosuppressive macrophages. Herein engineering of a previously optimized Doxorubicin (DOX)-delivery nanoplatform based on sodium alginate is reported to further co-deliver RRx-001 (biotinylated aldehyde alginate-doxorubicin micelle prodrug nanoplatform, BEA-D@R) for efficient immunotherapy of advanced HCC. This groundbreaking  technique reveals the "all-in-one" immunotherapeutic functionalities of RRx-001. Besides the previously demonstrated functions of downregulating CD47 expression and increasing reactive nitrogen species (RNS) generation, another key function of RRx-001 for downregulating the expression of the adaptive immune checkpoint molecule programmed cell death 1 ligand 1 (PDL1) is first uncovered here. Combined with the reactive oxygen species (ROS) generation and an upregulated "eat me" signal level of DOX, BEA-D@R collectively increases RNS generation, enhances T-cell infiltration, and maximizes macrophage phagocytosis, leading to an average of 40% tumor elimination in a mice model bearing an initial tumor volume of ≈300 mm3 that mimics advanced HCC. Overall, the "all-in-one" immunotherapeutic functionalities of a clinical translatable nanoplatform are uncovered for enhanced immunotherapy of advanced HCC.

Targeting HDAC6 improves anti-CD47 immunotherapy

BACKGROUND

Cancer cells can overexpress CD47, an innate immune checkpoint that prevents phagocytosis upon interaction with signal regulatory protein alpha (SIRPα) expressed in macrophages and other myeloid cells. Several clinical trials have reported that CD47 blockade reduces tumor growth in hematological malignancies. However, CD47 blockade has shown modest results in solid tumors, including melanoma. Our group has demonstrated that histone deacetylase 6 inhibitors (HDAC6is) have immunomodulatory properties, such as controlling macrophage phenotype and inflammatory properties. However, the molecular and cellular mechanisms controlling these processes are not fully understood. In this study, we evaluated the role of HDAC6 in regulating the CD47/SIRPα axis and phagocytosis in macrophages.

METHODS

We tested the role of HDAC6is, especially Nexturastat A, in regulating macrophage phenotype and phagocytic function using bone marrow-derived macrophages and macrophage cell lines. The modulation of the CD47/SIRPα axis and phagocytosis by HDAC6is was investigated using murine and human melanoma cell lines and macrophages. Phagocytosis was evaluated via coculture assays of macrophages and melanoma cells by flow cytometry and immunofluorescence. Lastly, to evaluate the antitumor activity of Nexturastat A in combination with anti-CD47 or anti-SIRPα antibodies, we performed in vivo studies using the SM1 and/or B16F10 melanoma mouse models.

RESULTS

We observed that HDAC6is enhanced the phenotype of antitumoral M1 macrophages while decreasing the protumoral M2 phenotype. In addition, HDAC6 inhibition diminished the expression of SIRPα, increased the expression of other pro-phagocytic signals in macrophages, and downregulated CD47 expression in mouse and human melanoma cells. This regulatory role on the CD47/SIRPα axis translated into enhanced antitumoral phagocytic capacity of macrophages treated with Nexturastat A and anti-CD47. We also observed that the systemic administration of HDAC6i enhanced the in vivo antitumor activity of anti-CD47 blockade in melanoma by modulating macrophage and natural killer cells in the tumor microenvironment. However, Nexturastat A did not enhance the antitumor activity of anti-SIRPα despite its modulation of macrophage populations in the SM1 tumor microenvironment.

CONCLUSIONS

Our results demonstrate the critical regulatory role of HDAC6 in phagocytosis and innate immunity for the first time, further underscoring the use of these inhibitors to potentiate CD47 immune checkpoint blockade therapeutic strategies.

Opportunities and challenges of CD47-targeted therapy in cancer immunotherapy

Cancer immunotherapy has emerged as a promising strategy for the treatment of cancer, with the tumor microenvironment (TME) playing a pivotal role in modulating the immune response. CD47, a cell surface protein, has been identified as a crucial regulator of the TME and a potential therapeutic target for cancer therapy. However, the precise functions and implications of CD47 in the TME during immunotherapy for cancer patients remain incompletely understood. This comprehensive review aims to provide an overview of CD47's multifaced role in TME regulation and immune evasion, elucidating its impact on various types of immunotherapy outcomes, including checkpoint inhibitors and CAR T-cell therapy. Notably, CD47-targeted therapies offer a promising avenue for improving cancer treatment outcomes, especially when combined with other immunotherapeutic approaches. The review also discusses current and potential CD47-targeted therapies being explored for cancer treatment and delves into the associated challenges and opportunities inherent in targeting CD47. Despite the demonstrated effectiveness of CD47-targeted therapies, there are potential problems, including unintended effects on healthy cells, hematological toxicities, and the development if resistance. Consequently, further research efforts are warranted to fully understand the underlying mechanisms of resistance and to optimize CD47-targeted therapies through innovative combination approaches, ultimately improving cancer treatment outcomes. Overall, this comprehensive review highlights the significance of CD47 as a promising target for cancer immunotherapy and provides valuable insight into the challenges and opportunities in developing effective CD47-targeted therapies for cancer treatment.

Human CD47-Derived Cyclic Peptides Enhance Engulfment of mAb-Targeted Melanoma by Primary Macrophages

CD47 on healthy cells, cancer cells, and even engineered particles can inhibit phagocytic clearance by binding SIRPα on macrophages. To mimic and modulate this interaction with peptides that could be used as soluble antagonists or potentially as bioconjugates to surfaces, we made cyclic "nano-Self" peptides based on the key interaction loop of human CD47. Melanoma cells were studied as a standard preclinical cancer model and were antibody-opsonized to adhere to and activate engulfment by primary mouse macrophages. Phagocytosis in the presence of soluble peptides showed cyclic > wildtype > scrambled activity, with the same trend observed with human cells. Opsonized cells that were not engulfed adhered tightly to macrophages, with opposite trends to phagocytosis. Peptide activity is nonetheless higher in human versus mouse assays, consistent with species differences in CD47-SIRPα. Small peptides thus function as soluble antagonists of a major macrophage checkpoint.

NEAT1 in bone marrow mesenchymal stem cell-derived extracellular vesicles promotes melanoma by inducing M2 macrophage polarization

Bone marrow mesenchymal stem cells (BMSCs)-derived extracellular vesicles (EVs) reportedly play an important role in melanoma pathogenesis. This study aimed to explore the mechanisms of EVs-carried long non-coding RNA (lncRNA) NEAT1 involvement in melanoma. Gain- and loss-of-function experiments were performed to determine biological characteristics of A-375 melanoma cells. Bioinfomatic prediction, RNA immunoprecipitation (RIP), and dual luciferase reporter gene experiments were applied to investigate the roles of NEAT1 and microRNA-374a-5p (miR-374a-5p), and leucine-rich repeat-containing G protein-coupled receptor 4 (LGR4). A subcutaneous tumor model was constructed using nude mice, and in vivo fluorescence imaging was used to observe the effect of NEAT1 on the growth and metastasis of melanoma cells in vivo. The results indicated that BMSC-EVs could be internalized by macrophages to promote the expression of macrophages M2 markers. M2 type macrophages promoted malignancy of melanoma cells. NEAT1 derived from BMSC-EVs promoted the progression of melanoma by promoting M2 polarization of macrophages. NEAT1 inhibits miR-374 expression, while miR-374 could upregulate LGR4-dependent IQGAP1 expression. The tumor-inhibiting effect of NEAT1 silencing was validated in the nude mouse xenograft model. Collectively, the results demonstrated that BMSC-EVs carrying NEAT1 can promote the progression of melanoma by inducing M2 polarization of macrophages, and thus may be considered as a potential target for melanoma therapeutics.

Enhancing Therapeutic Approaches for Melanoma Patients Targeting Epigenetic Modifiers

Melanoma is the least common but deadliest type of skin cancer. Melanomagenesis is driven by a series of mutations and epigenetic alterations in oncogenes and tumor suppressor genes that allow melanomas to grow, evolve, and metastasize. Epigenetic alterations can also lead to immune evasion and development of resistance to therapies. Although the standard of care for melanoma patients includes surgery, targeted therapies, and immune checkpoint blockade, other therapeutic approaches like radiation therapy, chemotherapy, and immune cell-based therapies are used for patients with advanced disease or unresponsive to the conventional first-line therapies. Targeted therapies such as the use of BRAF and MEK inhibitors and immune checkpoint inhibitors such as anti-PD-1 and anti-CTLA4 only improve the survival of a small subset of patients. Thus, there is an urgent need to identify alternative standalone or combinatorial therapies. Epigenetic modifiers have gained attention as therapeutic targets as they modulate multiple cellular and immune-related processes. Due to melanoma's susceptibility to extrinsic factors and reversible nature, epigenetic drugs are investigated as a therapeutic avenue and as adjuvants for targeted therapies and immune checkpoint inhibitors, as they can sensitize and/or reverse resistance to these therapies, thus enhancing their therapeutic efficacy. This review gives an overview of the role of epigenetic changes in melanoma progression and resistance. In addition, we evaluate the latest advances in preclinical and clinical research studying combinatorial therapies and discuss the use of epigenetic drugs such as HDAC and DNMT inhibitors as potential adjuvants for melanoma patients.

Targeting Ovarian Carcinoma with TSP-1:CD47 Antagonist TAX2 Activates Anti-Tumor Immunity

TAX2 peptide is a cyclic peptide that acts as an orthosteric antagonist for thrombospondin-1 (TSP-1) interaction with CD47. TAX2 was first described for its anti-angiogenic activities and showed anti-cancer efficacy in numerous preclinical models. Here, we aimed at providing an extensive molecular characterization of TAX2 mode of action, while evaluating its potential in ovarian cancer therapy. Multidisciplinary approaches were used to qualify a TAX2 drug candidate in terms of stability, solubility and potency. Then, efficacy studies, together with benchmark experiments, were performed in relevant mouse models of ovarian carcinoma. TAX2 peptide appears to be stable and soluble in clinically relevant solvents, while displaying a favorable safety profile. Moreover, clinical data mining allowed for the identification of TSP-1 as a relevant pharmacological target in ovarian cancer. In mice, TAX2 therapy inhibits ovarian tumor growth and metastatic dissemination, while activating anti-cancer adaptive immunity. Interestingly, TAX2 also synergizes when administered in combination with anti-PD-1 immune checkpoint inhibitiors. Altogether, our data expose TAX2 as an optimized candidate with advanced preclinical characterization. Using relevant syngeneic ovarian carcinoma models, we highlighted TAX2's ability to convert poorly immunogenic tumors into ones displaying effective anti-tumor T-cell immunity.

An immune-based risk-stratification system for predicting prognosis in pulmonary sarcomatoid carcinoma (PSC)

Pulmonary sarcomatoid carcinoma (PSC) is an uncommon subtype of lung cancer, and immune checkpoint blockade promises in clinical benefit. However, virtually nothing is known about the expression of common immune checkpoints in PSC. Here, we performed immunohistochemistry (IHC) to detect nine immune-related proteins in 97 PSC patients. Based on the univariable Cox regression, random forests were used to establish risk models for OS and DFS. Moreover, we used the GSEA, CIBERSORT, and ImmuCellAI to analyze the enriched pathways and microenvironment. Univariable analysis revealed that CD4 (P = 0.008), programmed cell death protein 1 (PD-1; P = 0.003), galectin-9 (Gal-9) on tumor cells (TCs; P = 0.021) were independent for DFS, while CD4 (P = 0.020), PD-1 (P = 0.004), Gal-9 (P = 0.033), and HLA on TILs (P = 0.031) were significant for OS. Meanwhile, the expression level of CD8 played a marginable role in DFS (P = 0.061), limited by the number of patients. The combination of Gal-9 on TC with CD4 and PD-1 on TILs demonstrated the most accurate prediction for DFS (AUC: 0.636-0.791, F1-score: 0.635–0.799), and a dramatic improvement to TNM-stage (P < 0.001 for F1-score of 1-y, 3-y, and 5-yDFS). A similar finding was also observed in the predictive ability of CD4 for OS (AUC: 0.602-0.678, F1-score: 0.635–0.679). CD4 was negatively associated with the infiltration of neutrophils (P = 0.015). PDCD1 (coding gene of PD-1) was positively correlated to the number of exhausted T cells (Texs; P = 0.020) and induced regulatory T cells (iTregs; P = 0.021), and LGALS9 (coding gene of Gal-9) was positively related to the level of dendritic cells (DCs; P = 0.021). Further, a higher combinational level of CD4, PDCD1 on TILs, and LAGLS9 on TCs were proved to be infiltrated with more M1-type macrophages (P < 0.05). We confirmed the expression status of nine immune-related proteins and established a TNM-Immune system for OS and DFS in PSC to assist clinical risk-stratification.

Genomically Complex Human Angiosarcoma and Canine Hemangiosarcoma Establish Convergent Angiogenic Transcriptional Programs Driven by Novel Gene Fusions

Sporadic angiosarcomas are aggressive vascular sarcomas whose rarity and genomic complexity present significant obstacles in deciphering the pathogenic significance of individual genetic alterations. Numerous fusion genes have been identified across multiple types of cancers, but their existence and significance remain unclear in sporadic angiosarcomas. In this study, we leveraged RNA-sequencing data from 13 human angiosarcomas and 76 spontaneous canine hemangiosarcomas to identify fusion genes associated with spontaneous vascular malignancies. Ten novel protein-coding fusion genes, including TEX2-PECAM1 and ATP8A2-FLT1, were identified in seven of the 13 human tumors, with two tumors showing mutations of TP53. HRAS and NRAS mutations were found in angiosarcomas without fusions or TP53 mutations. We found 15 novel protein-coding fusion genes including MYO16-PTK2, GABRA3-FLT1, and AKT3-XPNPEP1 in 11 of the 76 canine hemangiosarcomas; these fusion genes were seen exclusively in tumors of the angiogenic molecular subtype that contained recurrent mutations in TP53, PIK3CA, PIK3R1, and NRAS. In particular, fusion genes and mutations of TP53 cooccurred in tumors with higher frequency than expected by random chance, and they enriched gene signatures predicting activation of angiogenic pathways. Comparative transcriptomic analysis of human angiosarcomas and canine hemangiosarcomas identified shared molecular signatures associated with activation of PI3K/AKT/mTOR pathways. Our data suggest that genome instability induced by TP53 mutations might create a predisposition for fusion events that may contribute to tumor progression by promoting selection and/or enhancing fitness through activation of convergent angiogenic pathways in this vascular malignancy. IMPLICATIONS: This study shows that, while drive events of malignant vasoformative tumors of humans and dogs include diverse mutations and stochastic rearrangements that create novel fusion genes, convergent transcriptional programs govern the highly conserved morphologic organization and biological behavior of these tumors in both species.

Warburg Effect Is a Cancer Immune Evasion Mechanism Against Macrophage Immunosurveillance

Evasion of immunosurveillance is critical for cancer initiation and development. The expression of “don’t eat me” signals protects cancer cells from being phagocytosed by macrophages, and the blockade of such signals demonstrates therapeutic potential by restoring the susceptibility of cancer cells to macrophage-mediated phagocytosis. However, whether additional self-protective mechanisms play a role against macrophage surveillance remains unexplored. Here, we derived a macrophage-resistant cancer model from cells deficient in the expression of CD47, a major “don’t eat me” signal, via a macrophage selection assay. Comparative studies performed between the parental and resistant cells identified self-protective traits independent of CD47, which were examined with both pharmacological or genetic approaches in in vitro phagocytosis assays and in vivo tumor models for their roles in protecting against macrophage surveillance. Here we demonstrated that extracellular acidification resulting from glycolysis in cancer cells protected them against macrophage-mediated phagocytosis. The acidic tumor microenvironment resulted in direct inhibition of macrophage phagocytic ability and recruitment of weakly phagocytic macrophages. Targeting V-ATPase which transports excessive protons in cancer cells to acidify extracellular medium elicited a pro-phagocytic microenvironment with an increased ratio of M1-/M2-like macrophage populations, therefore inhibiting tumor development and metastasis. In addition, blockade of extracellular acidification enhanced cell surface exposure of CD71, targeting which by antibodies promoted cancer cell phagocytosis. Our results reveal that extracellular acidification due to the Warburg effect confers immune evasion ability on cancer cells. This previously unrecognized role highlights the components mediating the Warburg effect as potential targets for new immunotherapy harnessing the tumoricidal capabilities of macrophages.

Checkpoint CD47 Function On Tumor Metastasis And Immune Therapy

The success of cancer immunotherapy on recognition checkpoints for killing cancer cells has raised a great interest of scientists in understanding new and old methods of immunotherapeutic. CD47 (cluster of differentiation 47) is a cell surface glycoprotein and widely expressed on cells, which belongs to the immunoglobulin (Ig) superfamily as a cell membrane receptor which serves in immune therapy. CD47 is an inhibitory receptor expressed on tumor cell surface and interacts with signal receptor protein-alpha (SIPR-α, also named CD172a or SHPS-1) which may escape from immune cells such as macrophage and T cells. Meanwhile, tumor cells express high CD47 protein which may secrete exosomes with high CD47 expression. The high CD47 expression-exosomes could serve the tumor metastasis process and provide transfer convenience for tumors on the microenvironment. CD47 on cancer cells can also affect the migration and invasion of cells. The high CD47 expression on tumor or CTC (circulating tumor cell) surface means the stronger migration and invasion and makes them escape from immune cells for phagocytosis such as T cells, NK (natural killer) cells and macrophage, which could be used for diagnosis and prognosis on cancer patients. Meanwhile, targeting CD47 combined with other biomarkers such as EpCAM (epithelial cell adhesion molecule), CD44, etc on cancer surface could be used to isolate CTCs from patients' blood. In terms of treatment, anti-CD47 antibody combined with another antibody such as anti-PD-L1 (programmed death-ligand 1) antibody or drugs such as rituximab, DOX or oxaliplatin also has better therapeutic effects and antitumor function to tumors. Using nanomaterials as an intermediary for CD47-related immune therapy could greatly increase the therapeutic effect and overcome multiple biological barriers for anti-CD47 antibody in vivo. In this review, we discuss the important role and the function of CD47 in tumor metastasis and also provide a reference for related research.