CXCR4 inhibition modulates the tumor microenvironment and retards the growth of B16-OVA melanoma and Renca tumors

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

Is it possible to treat melanoma by intercepting the CXCR4/CXCL12 pathway?

Melanoma is a particularly aggressive type of skin cancer that can spread to distant organs, resulting in poor patient outcomes. C-X-C motif chemokine ligand 12 (CXCL12) interacts to the C-X-C chemokine receptor type 4 (CXCR4). This connection between CXCR4 and its companion ligand CXCL12 is important in melanoma metastasis and progression, encouraging cell proliferation, invasion, and survival via downstream signaling pathways. Furthermore, CXCR4 is implicated in the interaction between melanoma cells and the tumor microenvironment, which promotes malignant cell migration and immune evasion. Given the importance of the CXCR4/CXCL12 axis in melanoma, addressing this axis has the potential to prevent metastasis and improve patient outcomes. We present an overview of the CXCR4/CXCL12 axis in cancer progression and explain its role in the melanoma microenvironment in this paper. Furthermore, we investigate CXCR4's predictive usefulness as a possible biomarker for monitoring melanoma progression. Finally, we discuss the most recent research and clinical trials on CXCR4 inhibitors, emphasizing their efficacy and limits. We hope to improve the quality of life for melanoma patients by better understanding the role of CXCR4 and investigating novel therapeutic options.

Novel cancer treatment paradigm targeting hypoxia-induced factor in conjunction with current therapies to overcome resistance

Chemotherapy, radiotherapy, targeted therapy, and immunotherapy are established cancer treatment modalities that are widely used due to their demonstrated efficacy against tumors and favorable safety profiles or tolerability. Nevertheless, treatment resistance continues to be one of the most pressing unsolved conundrums in cancer treatment. Hypoxia-inducible factors (HIFs) are a family of transcription factors that regulate cellular responses to hypoxia by activating genes involved in various adaptations, including erythropoiesis, glucose metabolism, angiogenesis, cell proliferation, and apoptosis. Despite this critical function, overexpression of HIFs has been observed in numerous cancers, leading to resistance to therapy and disease progression. In recent years, much effort has been poured into developing innovative cancer treatments that target the HIF pathway. Combining HIF inhibitors with current cancer therapies to increase anti-tumor activity and diminish treatment resistance is one strategy for combating therapeutic resistance. This review focuses on how HIF inhibitors could be applied in conjunction with current cancer treatments, including those now being evaluated in clinical trials, to usher in a new era of cancer therapy.

Understanding tumour endothelial cell heterogeneity and function from single-cell omics

Anti-angiogenic therapies (AATs) are used to treat different types of cancers. However, their success is limited owing to insufficient efficacy and resistance. Recently, single-cell omics studies of tumour endothelial cells (TECs) have provided new mechanistic insight. Here, we overview the heterogeneity of human TECs of all tumour types studied to date, at the single-cell level. Notably, most human tumour types contain varying numbers but only a small population of angiogenic TECs, the presumed targets of AATs, possibly contributing to the limited efficacy of and resistance to AATs. In general, TECs are heterogeneous within and across all tumour types, but comparing TEC phenotypes across tumours is currently challenging, owing to the lack of a uniform nomenclature for endothelial cells and consistent single-cell analysis protocols, urgently raising the need for a more consistent approach. Nonetheless, across most tumour types, universal TEC markers (ACKR1, PLVAP and IGFBP3) can be identified. Besides angiogenesis, biological processes such as immunomodulation and extracellular matrix organization are among the most commonly predicted enriched signatures of TECs across different tumour types. Although angiogenesis and extracellular matrix targets have been considered for AAT (without the hoped success), the immunomodulatory properties of TECs have not been fully considered as a novel anticancer therapeutic approach. Therefore, we also discuss progress, limitations, solutions and novel targets for AAT development.

The prospect of tumor microenvironment-modulating therapeutical strategies

Multiple mechanisms promote tumor prosperity, which does not only depend on cell-autonomous, inherent abnormal characteristics of the malignant cells that facilitate rapid cell division and tumor expansion. The neoplastic tissue is embedded in a supportive and dynamic tumor microenvironment (TME) that nurtures and protects the malignant cells, maintaining and perpetuating malignant cell expansion. The TME consists of different elements, such as atypical vasculature, various innate and adaptive immune cells with immunosuppressive or pro-inflammatory properties, altered extracellular matrix (ECM), activated stromal cells, and a wide range of secreted/stroma-tethered bioactive molecules that contribute to malignancy, directly or indirectly. In this review, we describe the various TME components and provide examples of anti-cancer therapies and novel drugs under development that aim to target these components rather than the intrinsic processes within the malignant cells. Combinatory TME-modulating therapeutic strategies may be required to overcome the resistance to current treatment options and prevent tumor recurrence.

Mavorixafor, an Orally Bioavailable CXCR4 Antagonist, Increases Immune Cell Infiltration and Inflammatory Status of Tumor Microenvironment in Patients with Melanoma

Purpose

Mavorixafor is an oral, selective inhibitor of the CXCR4 chemokine receptor that modulates immune cell trafficking. A biomarker-driven phase Ib study (NCT02823405) was conducted in 16 patients with melanoma to investigate the hypothesis that mavorixafor favorably modulates immune cell profiles in the tumor microenvironment (TME) and to evaluate the safety of mavorixafor alone and in combination with pembrolizumab.

Experimental Design

Serial biopsies of melanoma lesions were assessed after 3 weeks of mavorixafor monotherapy and after 6 weeks of combination treatment for immune cell markers by NanoString analysis for gene expression and by multiplexed immunofluorescent staining for in situ protein expression. Serum samples taken at biopsy timepoints were evaluated for key chemokine and cytokine alterations using the Myriad Rules Based Medicine multiplex immunoassays.

Results

Within the TME, mavorixafor alone increased CD8⁺ T-cell infiltration, granzyme B signal, antigen presentation machinery, and both tumor inflammatory signature (TIS) and IFNγ gene expression signature scores. Increases in the key serum cytokines CXCL9 and CXCL10 were further enhanced when mavorixafor was combined with pembrolizumab. Adverse events (AE), as assessed by the investigator according to NCI Common Terminology Criteria for Adverse Events (v4.03), related to either mavorixafor or pembrolizumab (≥15%) were diarrhea, fatigue, maculopapular rash, and dry eye. Reported AEs were all ≤ grade 3.

Conclusion/Discussion

Treatment with single-agent mavorixafor resulted in enhanced immune cell infiltration and activation in the TME, leading to increases in TIS and IFNγ gene signatures. Mavorixafor as a single agent, and in combination with pembrolizumab, has an acceptable safety profile. These data support further investigation of the use of mavorixafor for patients unresponsive to checkpoint inhibitors.

Significance

Despite survival improvements in patients with melanoma treated with checkpoint inhibitor therapy, a significant unmet medical need exists for therapies that enhance effectiveness. We propose that mavorixafor sensitizes the melanoma tumor microenvironment and enhances the activity of checkpoint inhibitors, and thereby may translate to a promising treatment for broader patient populations.

The Challenging Melanoma Landscape: From Early Drug Discovery to Clinical Approval

Melanoma is recognized as the most dangerous type of skin cancer, with high mortality and resistance to currently used treatments. To overcome the limitations of the available therapeutic options, the discovery and development of new, more effective, and safer therapies is required. In this review, the different research steps involved in the process of antimelanoma drug evaluation and selection are explored, including information regarding in silico, in vitro, and in vivo experiments, as well as clinical trial phases. Details are given about the most used cell lines and assays to perform both two- and three-dimensional in vitro screening of drug candidates towards melanoma. For in vivo studies, murine models are, undoubtedly, the most widely used for assessing the therapeutic potential of new compounds and to study the underlying mechanisms of action. Here, the main melanoma murine models are described as well as other animal species. A section is dedicated to ongoing clinical studies, demonstrating the wide interest and successful efforts devoted to melanoma therapy, in particular at advanced stages of the disease, and a final section includes some considerations regarding approval for marketing by regulatory agencies. Overall, considerable commitment is being directed to the continuous development of optimized experimental models, important for the understanding of melanoma biology and for the evaluation and validation of novel therapeutic strategies.

Role of CXCR4 as a Prognostic Biomarker Associated With the Tumor Immune Microenvironment in Gastric Cancer

Background: Gastric cancer (GC) is a leading cause of cancer-related deaths worldwide, accounting for high rates of morbidity and mortality in the population. The tumor microenvironment (TME), which plays a crucial role in GC progression, may serve as an optimal prognostic predictor of GC. In this study, we identified CXC motif chemokine receptor 4 (CXCR4) as a TME-related gene among thousands of differentially expressed genes (DEGs). We showed that CXCR4 can be used to predict the effect of immunotherapy in patients with GC.

Methods: GC samples obtained from The Cancer Genome Atlas (TCGA) were analyzed for the presence of stroma (stromal score), the infiltration of immune cells (immune score) in tumor tissues, and the tumor purity (estimate score) using the ESTIMATE (Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data) algorithm. DEGs were sorted based on differences in the values of the three scores. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to determine the biological processes and pathways enriched in these DEGs. The correlations of scores with clinicopathological features and overall survival (OS) of patients with GC were assessed by the Kaplan–Meier survival and Cox regression analyses. Through subsequent protein–protein interaction (PPI) network and univariate Cox regression analyses, CXCR4 was identified as a TME-related gene. Gene Set Enrichment Analysis (GSEA) was performed to assess the role of CXCR4 in the TME of GC. The CIBERSORT algorithm was used to further explore the correlation between tumor-infiltrating immune cells (TIICs) and CXCR4. Finally, the TISIDB database was used to predict the efficacy of immunotherapy in patients with GC.

Results: We extracted 1231 TME-related DEGs and by an overlapping screening of PPI network and univariate Cox regression, CXCR4 was identified as a biomarker of TME, which deeply engaged in immune-related biological processes of gastric cancer and have close association with several immunocompetent cells.

Conclusion: CXCR4 may be a useful biomarker of prognosis and an indicator of the TME in GC.

Current challenges in targeting tumor desmoplasia to improve the efficacy of immunotherapy

Desmoplasia is crucial for the development, progression and treatment of immune-resistant malignancies. and treatment of immune-resistant malignancies. Targeting desmoplasia-related metabolic pathways appears to be an interesting approach to expand our stock of disposable anti-tumor agents.CXCL12/CXCR4 axis inhibition reduces fibrosis, alleviates immunosuppression and significantly enhances the efficacy of PD-1 immunotherapy. CD40L substitute therapy may increase the activity of T-cells, downregulate CD40+, prolong patients' survival and prevent cancer progression. Although FAPα antagonists used in preclinical models did not lead to permanent cure, an alleviation of immune-resistance, modification of desmoplasia and a decrease in angiogenesis were observed. Targeting DDR2 may enhance the effect of anti-PD-1 treatment in multiple neoplasm cell lines and has the ability to overcome the adaptation to BRAF-targeted therapy in melanoma. Reprogramming desmoplasia could potentially cooperate not only with present treatment, but also other potential therapeutic targets. We present the most promising metabolic pathways related to desmoplasia and discuss the emerging strategies to improve the efficacy of immunotherapy.

Identification of potential targets of triptolide in regulating the tumor microenvironment of stomach adenocarcinoma patients using bioinformatics

This study aimed to identify potential pharmacological targets of triptolide regulating the tumor microenvironment (TME) of stomach adenocarcinoma (STAD) patients. A total of 343 STAD cases from The Cancer Genome Atlas (TCGA) were assigned into high- or low-score groups applying Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE). Hub genes were identified from differentially expressed genes (DEGs) shared by stromal- and immune-related components in the TME of STAD patients using R software. Cox regression analysis was used to identify genes significantly correlated with STAD patient survival. Triptolide target genes were predicted from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). Top 30 genes filtered by Cytohubba from 734 DEGs were screened as hub genes. Forty-two genes were found to be at high risk for STAD prognosis. Thirty-four targets of triptolide were predicted using the TCMSP database. Importantly, C-X-C chemokine receptor type 4 (CXCR4) was identified as a potential target of triptolide associated with the TME in STAD. Analysis of survival highlighted the association between CXCR4 upregulation with STAD progression and poor prognosis. Gene Set Enrichment Analysis (GSEA) confirmed that genes in the CXCR4- upregulated group had significant enrichment in immune-linked pathways. Additionally, triptolide targets were found to be significantly enriched in CXCR4-related chemokine and cancer-related p53 signaling pathways. Molecular docking demonstrated a high affinity between triptolide and CXCR4. In conclusion, CXCR4 may be a therapeutic target of triptolide in the treatment of STAD patients by modulating the TME.

ACE2 abrogates tumor resistance to VEGFR inhibitors suggesting angiotensin-(1-7) as a therapy for clear cell renal cell carcinoma

Angiotensin converting enzyme 2 (ACE2) is an enzyme that belongs to the renin-angiotensin system (RAS) and antagonizes the classical angiotensin (Ang) II/angiotensin II receptor type 1 (AT1) receptor pathway. Here, we report that higher ACE2 expression correlates with better overall survival in patients with clear cell renal cell carcinoma (ccRCC). Moreover, ACE2 has inhibitory effects on tumor proliferation in ccRCC in vitro and in preclinical animal models of ccRCC. We further show that Ang-(1-7), a heptapeptide generated by ACE2, is the likely mediator of this effect. Vascular endothelial growth factor receptor-tyrosine kinase inhibitor (VEGFR-TKI) treatment of ccRCC xenografts decreased ACE2 expression, and combination treatment with VEGFR-TKI and Ang-(1-7) generated additive suppression of tumor growth and improved survival outcomes. Last, the addition of Ang-(1-7) to programmed death-ligand 1 (PD-L1) pathway inhibitor and VEGFR-TKI showed further growth suppression in an immunocompetent RCC model. Together, these results suggest that targeting the ACE2/Ang-(1-7) axis is a promising therapeutic strategy against ccRCC.

The Complexity of Targeting Chemokines to Promote a Tumor Immune Response

Immunotherapeutic treatment strategies greatly extend patient survival following malignant disease across a wide range of tumor types, including even those with metastatic disease. While diverse in approach, adoptive cell therapy, introduction of T cells that express chimeric antigen receptors, and checkpoint inhibitors all aim to re-invigorate the immune system to promote tumor cell identification and elimination. This review will focus on immune cell infiltration into tumors as well as a cellular organization within the tumor microenvironment as directed by the cell-specific expression patterns of chemokines and chemokine receptors. Through better understanding the chemokine network within tumors, we can uncover mechanisms to promote beneficial immune cell infiltration that can be combined with checkpoint inhibition. Conversely, chemokine expression is not limited to cells of the immune system, and it is understood that tumor cells also express chemokines and chemokine receptors. Tumor cells can hijack the chemokine networks to promote immune suppression and metastatic tumor cell trafficking. We will discuss the ways in which the chemokine network lies at the crossroad of immune evasion and tumor regression. Overall, this review will summarize key publications in the field of immune cell recruitment to tumors, highlight the dichotomous nature of chemokine interventions into cancer, and aims to identify therapeutic pathways forward.

Salmonella reduces tumor metastasis by downregulation C-X-C chemokine receptor type 4

Tumor metastasis is the main reason for the death of most cancer patients. C-X-C chemokine receptor type 4 (CXCR4) has been demonstrated to be overexpressed in numerous types of cancer. CXCR4 selectively binds with stromal cell-derived factor 1 (SDF1), also known as C-X-C family chemokine ligand 12 (CXCL12) (CXCL12/SDF-1), which induced tumor proliferation and metastasis. Recently, the use of conventional cancer treatments had some limitation; bacteria treatment for cancer becomes a trend that overcomes these limitations. Plenty of studies show that Salmonella has anti-tumor and anti-metastatic activity. The current study aimed to investigate Salmonella suppresses CXCR4 protein expression and tumor cell migration ability in B16F10 melanoma and LL2 lung carcinoma cells. Salmonella reduced CXCR4 protein expression through downregulating Protein Kinase-B (Akt)/Mammalian Target of Rapamycin (mTOR) signaling pathway. In cells transfected with constitutively active Akt plasmids, a reverse effect of Salmonella-induced inhibition of CXCR4 was observed. Tumor cells have chemotactic response to CXCL12 in migration assay, and we found that Salmonella reduced tumor chemotactic response after CXCL12 treatment. The C57BL/6 mice were intravenously injected with B16F10 and LL2 cells pre-incubated with or without Salmonella, the tumor size and lung weight of Salmonella group had obviously decreased, indicating anti-metastatic effect that confirmed the findings from the in vitro experiments.

TCR Redirected T Cells for Cancer Treatment: Achievements, Hurdles, and Goals

Adoptive T cell therapy (ACT) is a rapidly evolving therapeutic approach designed to harness T cell specificity and function to fight diseases. Based on the evidence that T lymphocytes can mediate a potent anti-tumor response, initially ACT solely relied on the isolation, in vitro expansion, and infusion of tumor-infiltrating or circulating tumor-specific T cells. Although effective in a subset of cases, in the first ACT clinical trials several patients experienced disease progression, in some cases after temporary disease control. This evidence prompted researchers to improve ACT products by taking advantage of the continuously evolving gene engineering field and by improving manufacturing protocols, to enable the generation of effective and long-term persisting tumor-specific T cell products. Despite recent advances, several challenges, including prioritization of antigen targets, identification, and optimization of tumor-specific T cell receptors, in the development of tools enabling T cells to counteract the immunosuppressive tumor microenvironment, still need to be faced. This review aims at summarizing the major achievements, hurdles and possible solutions designed to improve the ACT efficacy and safety profile in the context of liquid and solid tumors.

Comprehensive analysis of the prognostic value and immune function of chemokine-CXC receptor family members in breast cancer

Recently, immune checkpoint inhibitors (ICIs) have been successfully used for treating melanoma. Unfortunately, many breast cancer (BC) patients show low response to ICIs due to the lack of infiltrating immune cells. Previous studies revealed that chemokine-CXC receptors (CXCRs) play a crucial role in leukocyte infiltration and promote cancer cell proliferation, migration, metastasis, and angiogenesis. However, the underlying functions of CXCRs in cancer-immunity cycle remain unclear. In this study, we firstly found that in comparison to normal tissues, BC tissues, especially basal-like BC, showed increased mRNA levels of CXCR3/4/5/6/8, but decreased CXCR1/2/7 expression using UALCAN and TIMER database. Interestingly, it's was found that the mRNA levels of CXCR3/4/5/6 were decreased in lymphocyte depleted of the BC immune subtype. Subsequently, functional enrichment analysis of distinct CXCRs indicated that CXCR3/4/5/6 were strongly associated to immune-related biological functions. Therefore, further analysis using TIMER and TISIDB database suggested that CXCR3/4/5/6 expression were strongly correlated with tumor-infiltrating lymphocytes (TILs) and immune checkpoints in BC. Finally, Kaplan-Meier Plotter analysis indicated that high mRNA expression of CXCR4 predicted worse relapse-free survival (RFS), whereas CXCR3/5/6 indicated better RFS in BC patients. These findings suggest a therapeutic value for CXCR3/4/5/6 in combination with ICIs for the treatment of BC.

Donor bone-marrow CXCR4+ Foxp3+ T-regulatory cells are essential for costimulation blockade-induced long-term survival of murine limb transplants

Vascularized composite allotransplantation (VCA) allows tissue replacement after devastating loss but is currently limited in application and may be more widely performed if maintenance immunosuppression was not essential for graft acceptance. We tested whether peri-transplant costimulation blockade could prolong VCA survival and required donor bone-marrow cells, given that bone-marrow might promote graft immunogenicity or graft-versus-host disease. Peritransplant CD154 mAb/rapamycin (RPM) induced long-term orthotopic hindlimb VCA survival (BALB/c->C57BL/6), as did CTLA4Ig/RPM. Surprisingly, success of either protocol required a bone-marrow-associated, radiation-sensitive cell population, since long-bone removal or pre-transplant donor irradiation prevented long-term engraftment. Rejection also occurred if Rag1−/− donors were used, or if donors were treated with a CXCR4 inhibitor to mobilize donor BM cells pre-transplant. Donor bone-marrow contained a large population of Foxp3+ T-regulatory (Treg) cells, and donor Foxp3+ Treg depletion, by diphtheria toxin administration to DEREG donor mice whose Foxp3+ Treg cells expressed diphtheria toxin receptor, restored rejection with either protocol. Rejection also occurred if CXCR4 was deleted from donor Tregs pre-transplant. Hence, long-term VCA survival is possible across a full MHC disparity using peritransplant costimulation blockade-based approaches, but unexpectedly, the efficacy of costimulation blockade requires the presence of a radiation-sensitive, CXCR4+ Foxp3+ Treg population resident within donor BM.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.