CXCR4 antagonist AMD3100 enhances the response of MDA-MB-231 triple-negative breast cancer cells to ionizing radiation

Molecular Changes in Breast Cancer Induced by Radiation Therapy

PURPOSE

Breast cancer treatments are based on prognostic clinicopathologic features that form the basis for therapeutic guidelines. Although the utilization of these guidelines has decreased breast cancer-associated mortality rates over the past three decades, they are not adequate for individualized therapy. Radiation therapy (RT) is the backbone of breast cancer treatment. Although a highly successful therapeutic modality clinically, from a biological perspective, preclinical studies have shown RT to have the potential to alter tumor cell phenotype, immunogenicity, and the surrounding microenvironment, potentially changing the behavior of cancer cells and resulting in a significant variation in RT response. This review presents the recent advances in revealing the complex molecular changes induced by RT in the treatment of breast cancer and highlights the complexities of translating this information into clinically relevant tools for improved prognostic insights and the revelation of novel approaches for optimizing RT.

METHODS AND MATERIALS

Current literature was reviewed with a focus on recent advances made in the elucidation of tumor-associated radiation-induced molecular changes across molecular, genetic, and proteomic bases. This review was structured with the aim of providing an up-to-date overview over the very broad and complex subject matter of radiation-induced molecular changes and radioresistance, familiarizing the reader with the broader issue at hand.

RESULTS

The subject of radiation-induced molecular changes in breast cancer has been broached from various physiological focal points including that of the immune system, immunogenicity and the abscopal effect, tumor hypoxia, breast cancer classification and subtyping, molecular heterogeneity, and molecular plasticity. It is becoming increasingly apparent that breast cancer clinical subtyping alone does not adequately account for variation in RT response or radioresistance. Multiple components of the tumor microenvironment and immune system, delivered RT dose and fractionation schedules, radiation-induced bystander effects, and intrinsic tumor physiology and heterogeneity all contribute to the resultant RT outcome.

CONCLUSIONS

Despite recent advances and improvements in anticancer therapies, tumor resistance remains a significant challenge. As new analytical techniques and technologies continue to provide crucial insight into the complex molecular mechanisms of breast cancer and its treatment responses, it is becoming more evident that personalized anticancer treatment regimens may be vital in overcoming radioresistance.

Targeting cytokine and chemokine signaling pathways for cancer therapy

Cytokines are critical in regulating immune responses and cellular behavior, playing dual roles in both normal physiology and the pathology of diseases such as cancer. These molecules, including interleukins, interferons, tumor necrosis factors, chemokines, and growth factors like TGF-β, VEGF, and EGF, can promote or inhibit tumor growth, influence the tumor microenvironment, and impact the efficacy of cancer treatments. Recent advances in targeting these pathways have shown promising therapeutic potential, offering new strategies to modulate the immune system, inhibit tumor progression, and overcome resistance to conventional therapies. In this review, we summarized the current understanding and therapeutic implications of targeting cytokine and chemokine signaling pathways in cancer. By exploring the roles of these molecules in tumor biology and the immune response, we highlighted the development of novel therapeutic agents aimed at modulating these pathways to combat cancer. The review elaborated on the dual nature of cytokines as both promoters and suppressors of tumorigenesis, depending on the context, and discussed the challenges and opportunities this presents for therapeutic intervention. We also examined the latest advancements in targeted therapies, including monoclonal antibodies, bispecific antibodies, receptor inhibitors, fusion proteins, engineered cytokine variants, and their impact on tumor growth, metastasis, and the tumor microenvironment. Additionally, we evaluated the potential of combining these targeted therapies with other treatment modalities to overcome resistance and improve patient outcomes. Besides, we also focused on the ongoing research and clinical trials that are pivotal in advancing our understanding and application of cytokine- and chemokine-targeted therapies for cancer patients.

Chemokine systems in oncology: From microenvironment modulation to nanocarrier innovations

Over the past few decades, significant strides have been made in understanding the pivotal roles that chemokine networks play in tumor biology. These networks, comprising chemokines and their receptors, wield substantial influence over cancer immune regulation and therapeutic outcomes. As a result, targeting these chemokine systems has emerged as a promising avenue for cancer immunotherapy. However, therapies targeting chemokines face significant challenges in solid tumor treatment, due to the complex and fragile of the chemokine networks. A nuanced comprehension of the complicacy and functions of chemokine networks, and their impact on the tumor microenvironment, is essential for optimizing their therapeutic utility in oncology. This review elucidates the ways in which chemokine networks interact with cancer immunity and tumorigenesis. We particularly elaborate on recent innovations in manipulating these networks for cancer treatment. The review also highlights future challenges and explores potential biomaterial strategies for clinical applications.

Combating multidrug resistance of breast cancer with ginsenoside Rh2-irrigated nano-in-thermogel

The emergence of multidrug resistance (MDR) is the leading cause of mortality in patients with breast cancer. Overexpressed P-glycoprotein (P-gp) that can pump out chemotherapeutics from multidrug-resistant cancer cells is the main cause of chemotherapy failure. P-gp inhibitors are hence increasingly used to sensitize chemotherapy to breast cancer with MDR by reducing the efflux of drugs. However, representative P-gp inhibitors usually have severe side effects and the effect of their release behavior on chemotherapy are neglected in current studies. We constructed a nano-in-thermogel delivery system with the sequential release of ginsenoside Rh2 (GRh2) and a chemotherapeutic drug in the tumor microenvironment as a drug compounding "reservoir" to combat MDR in breast cancer. Briefly, paclitaxel (PTX) and GRh2 were encapsulated in solid lipid nanoparticles (SLNs) and dispersed in a poloxamer-based thermogel (SLNs-Gel). GRh2 was used as an innovative and safe P-gp inhibitor to lower P-gp expression and cellular adenosine triphosphate context, thereby sensitizing PTX-resistant breast cancer cells (MCF-7/PTX) to PTX. Pharmacodynamic and in vivo safety studies confirmed that intratumoral injection of SLNs-Gel significantly suppressed the proliferation of PTX-resistant breast cancer and alleviated the PTX-induced hematotoxicity. The GRh2-irrigated nano-in-thermogel delivery system shows great potential in combating multidrug-resistant cancer.

Protein disulfide isomerase family member 4 promotes triple-negative breast cancer tumorigenesis and radiotherapy resistance through JNK pathway

BACKGROUND

Despite radiotherapy ability to significantly improve treatment outcomes and survival in triple-negative breast cancer (TNBC) patients, acquired resistance to radiotherapy poses a serious clinical challenge. Protein disulfide isomerase exists in endoplasmic reticulum and plays an important role in promoting protein folding and post-translational modification. However, little is known about the role of protein disulfide isomerase family member 4 (PDIA4) in TNBC, especially in the context of radiotherapy resistance.

METHODS

We detected the presence of PDIA4 in TNBC tissues and paracancerous tissues, then examined the proliferation and apoptosis of TNBC cells with/without radiotherapy. As part of the validation process, xenograft tumor mouse model was used. Mass spectrometry and western blot analysis were used to identify PDIA4-mediated molecular signaling pathway.

RESULTS

Based on paired clinical specimens of TNBC patients, we found that PDIA4 expression was significantly higher in tumor tissues compared to adjacent normal tissues. In vitro, PDIA4 knockdown not only increased apoptosis of tumor cells with/without radiotherapy, but also decreased the ability of proliferation. In contrast, overexpression of PDIA4 induced the opposite effects on apoptosis and proliferation. According to Co-IP/MS results, PDIA4 prevented Tax1 binding protein 1 (TAX1BP1) degradation by binding to TAX1BP1, which inhibited c-Jun N-terminal kinase (JNK) activation. Moreover, PDIA4 knockdown suppressed tumor growth xenograft model in vivo, which was accompanied by an increase in apoptosis and promoted tumor growth inhibition after radiotherapy.

CONCLUSIONS

The results of this study indicate that PDIA4 is an oncoprotein that promotes TNBC progression, and targeted therapy may represent a new and effective anti-tumor strategy, especially for patients with radiotherapy resistance.

Tumor-targeted AIE polymeric micelles mediated immunogenic sonodynamic therapy inhibits cancer growth and metastasis

Aggregation-induced emission luminogens (AIEgens) exhibit potent sonosensitivity in nanocarriers compared with conventional organic sonosensitizers owing to the strong fluorescence emission in the aggregated state. However, the premature drug leakage and ineffective tumor targeting of current AIE nanosonosensitizers critically restrict their clinical applications. Here, an AIEgen-based sonosensitizer (AIE/Biotin-M) with excellent sonosensitivity was developed by assembling salicylaldazine-based amphiphilic polymers (AIE-1) and 4T1 tumor-targeting amphiphilic polymers (DSPE-PEG-Biotin) for the effective delivery of salicylaldazine to 4T1 tumor tissues, aiming to mediate immunogenic SDT. In vitro, AIE/Biotin-M were highly stable and generated plentiful singlet oxygen (¹O₂) under ultrasound (US) irradiation. After AIE/Biotin-M targeted accumulation in the tumor, upon US irradiation, the generation of ¹O₂ not only led to cancer cell death, but also elicited a systemically immune response by causing the immunogenic cell death (ICD) of cancer cells. In addition to mediating SDT, AIE/Biotin-M could chelate and reduce Fe³⁺, Cu²⁺ and Zn²⁺ by salicylaldazine for inhibiting neovascularization in tumor tissues. Ultimately, AIE/Biotin-M systemically inhibited tumor growth and metastasis upon US irradiation. This study presents a facile approach to the development of AIE nanosonosensitizers for cancer SDT.

The Role of PET/CT in Breast Cancer

Female breast cancer has surpassed lung cancer as the most commonly diagnosed cancer worldwide, with an estimated 2.3 million new cases (11.7%), followed by lung cancer (11.4%) The current literature and the National Comprehensive Cancer Network (NCCN) guidelines state that ¹⁸F-FDG PET/CT is not routine for early diagnosis of breast cancer, and rather PET/CT scanning should be performed for patients with stage III disease or when conventional staging studies yield non-diagnostic or suspicious results because this modality has been shown to upstage patients compared to conventional imaging and thus has an impact on disease management and prognosis. Furthermore, with the growing interest in precision therapy in breast cancer, numerous novel radiopharmaceuticals have been developed that target tumor biology and have the potential to non-invasively guide the most appropriate targeted therapy. This review discusses the role of ¹⁸F-FDG PET and other PET tracers beyond FDG in breast cancer imaging.

Therapeutic Perspectives of HIV-Associated Chemokine Receptor (CCR5 and CXCR4) Antagonists in Carcinomas

The interaction between malignant cells and the tumor microenvironment is critical for tumor progression, and the chemokine ligand/receptor axes play a crucial role in this process. The CXCR4/CXCL12 and CCR5/CCL5 axes, both related to HIV, have been associated with the early (epithelial-mesenchymal transition and invasion) and late events (migration and metastasis) of cancer progression. In addition, these axes can also modulate the immune response against tumors. Thus, antagonists against the receptors of these axes have been proposed in cancer therapy. Although preclinical studies have shown promising results, clinical trials are needed to include these drugs in the oncological treatment protocols. New alternatives for these antagonists, such as dual CXCR4/CCR5 antagonists or combined therapy in association with immunotherapy, need to be studied in cancer therapy.

CXCR4 inhibitor, AMD3100, down-regulates PARP1 expression and Synergizes with olaparib causing severe DNA damage in BRCA-proficient triple-negative breast cancer

Poly ADP-ribose polymerase inhibitor (PARPi) treatment is effective in triple-negative breast cancer (TNBC) with BRCA mutation. However, its efficacy in BRCA-proficient TNBC remains unexplored. It is, therefore, an exciting proposition to broaden the indication of PARPi for BRCA-proficient TNBC patients. Chemokine receptor (CXCR4) is a transmembrane G protein-coupled receptor, which is involved in cell migration, proliferation, apoptosis, and damage repair, and it initiates many signalling pathways. Although administration of CXCR4 inhibitor alone is not ideal as a target drug, it can play a strong synergistic role in combination with other drugs. We explored the effect of CXCR4 and PARP1 on tumour cell proliferation, migration, metastasis, and apoptosis in vitro and in vivo and found that a CXCR4 inhibitor, AMD3100, enhanced the anti-tumour effect of PARP1 inhibitor, olaparib, on BRCA-proficient TNBC. When CXCR4 was inhibited and silenced, DNA damage repair and DNA replication fork activity were suppressed by up-regulating caspase-3-mediated increase in PARP1 cleavage; in combination with the inhibition of PARP1, AMD3100 resulted in the accumulation of fatal DNA damage and induction of apoptosis. This combination regimen can be effective against BRCA-proficient TNBC.

MiR-181a reduces radiosensitivity of non-small-cell lung cancer via inhibiting PTEN

BACKGROUND

The aim of this study is to explore the effect of micro ribonucleic acid (miR)-181a on the radiosensitivity of non-small cell lung cancer (NSCLC) and its potential mechanism of action.

METHODS

The differentially expressed miRNAs were screened in lung cancer tissues of radiotherapy-resistant and non-radiotherapy-resistant NSCLC patients, and verified via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Next, the effects of different miRNA expressions on patients' survival time were discussed, and target genes of miR-181a were predicted. The effect of miR-181a expression on radiosensitivity was determined using cell counting kit-8 (CCK-8) assay and flow cytometry. The direct target of miR-181a was verified via luciferase reporter assay. Phosphatase and tensin homolog deleted on chromosome ten (PTEN) was overexpressed using lentiviruses, and then whether miR-181a reduces radiosensitivity via targeting PTEN was detected via CCK-8 assay and flow cytometry. Finally, Western blotting was performed to detect the protein expression of PTEN.

RESULTS

The screening results of microarray expression profile assay revealed that 15 miRNAs had significant differences in lung cancer tissues of radiotherapy-resistant NSCLC patients compared with those in non-radiotherapy-resistant NSCLC patients. The results of RT-qPCR showed that hsa-miR-181a, hsa-miR-199b, hsa-miR-489 and hsa-miR-589 were significantly up-regulated in the lung cancer tissues of radiotherapy-resistant NSCLC patients compared with those in non-radiotherapy-resistant NSCLC patients. In addition, it was found that the survival time of NSCLC patients was obviously prolonged in hsa-miR-181a low-expression group and hsa-miR-589 high-expression group, but hsa-miR-489 and hsa-miR-199b had no significant influence on the survival time of NSCLC patients. According to KEGG enrichment analysis, the target genes of miR-181a were evidently enriched in the phosphatidylinositol 3-hydroxy kinase (PI3K)/protein kinase B (AKT) signaling pathway, NSCLC signaling pathway and other cancer signaling pathways. Under the radiation dose of 2, 4, 6 and 8 Gy, the survival rate of A549 cells rose in miR-181a mimic group, but declined in miR-181a inhibitor group. Moreover, compared with that in model group, the radiotherapy-induced apoptosis was markedly inhibited in miR-181a mimic group, but markedly promoted in miR-181a inhibitor group. It was also observed that the response of cells to radiotherapy-induced apoptosis was remarkably weakened in miR-181a mimic + PTEN overexpression group compared with that in miR-181a mimic group. Finally, miR-181a mimic group had a significantly lower protein expression of PTEN and significantly higher protein expressions of CXC chemokine receptor 4 (CXCR4), phosphorylated signal transducer and activator of transcription 3 (p-STAT3), p-AKT1 and p-mammalian target of rapamycin (mTOR) than model group, while miR-181a inhibitor group had the opposite protein expressions. The protein expressions of CXCR4, p-STAT3, p-AKT1 and p-mTOR were obviously lower in miR-181a mimic + PTEN overexpression group than those in miR-181a mimic group.

CONCLUSIONS

MiR-181a reduces the radiosensitivity of NSCLC via inhibiting PTEN expression.

Recent Advances in CXCL12/CXCR4 Antagonists and Nano-Based Drug Delivery Systems for Cancer Therapy

Chemokines can induce chemotactic cell migration by interacting with G protein-coupled receptors to play a significant regulatory role in the development of cancer. CXC chemokine-12 (CXCL12) can specifically bind to CXC chemokine receptor 4 (CXCR4) and is closely associated with the progression of cancer via multiple signaling pathways. Over recent years, many CXCR4 antagonists have been tested in clinical trials; however, Plerixafor (AMD3100) is the only drug that has been approved for marketing thus far. In this review, we first summarize the mechanisms that mediate the physiological effects of the CXCL12/CXCR4 axis. Then, we describe the use of CXCL12/CXCR4 antagonists. Finally, we discuss the use of nano-based drug delivery systems that exert action on the CXCL12/CXCR4 biological axis.

Ultrasound-Responsive Peptide Nanogels to Balance Conflicting Requirements for Deep Tumor Penetration and Prolonged Blood Circulation

A series of biological barriers need to be overcome for therapeutic nanocarriers accumulating at the tumor site and uptaken by cancer cells. One strategy is to construct switchable nanocarriers to meet the conflicting requirements for various physiology environments. In this work, besides widely studied endogenous stimuli-responsiveness, an exogenous ultrasound responsiveness was additionally embedded into nanocarriers to balance the conflicting needs of prolonged blood circulation and deep tumor penetration. Polylysine and Pluronic F127 were first coassembled and then cross-linked by genipin to form stable nanogel structure. Subsequently, ICAM-1 antibody was grafted onto the nanogel (designated as GenPLPF_T) for active tumor targeting. Upon external sonication, the F127 was shed from GenPLPF_T to induce swelling of nanogel with reduced stability and accelerated drug release. In detail, sonication leads to GenPLPF swelling from 329 to 516 nm, while its Young's modulus significantly decreased from 336.78 to 3.93 kPa. Through intravenous injection, relatively rigid GenPLPF_T was able to achieve a high level of accumulation at tumor site by active targeting and long-term blood circulation. Moreover, under sonication at the tumor site, GenPLPF_T became softer with enhanced deformability to achieve deep tumor penetration. In addition, in vivo studies revealed that GenPLPF_T was able to penetrate into the deep area of xenografted tumor with enhanced antitumor efficacy and reduced toxicity. Overall, this peptide nanogel with ultrasound-responsive stiffness demonstrates an effective approach to overcome a series of biological barriers for enhanced deep tumor therapy.

Targeting Tumour-Associated Fibroblasts in Cancers

Tumours develop within complex tissue environments consisting of aberrant oncogenic cancer cells, diverse innate and adaptive immune cells, along with structural stromal cells, extracellular matrix and vascular networks, and many other cellular and non-cellular soluble constituents. Understanding the heterogeneity and the complex interplay between these cells remains a key barrier in treating tumours and cancers. The immune status of the pre-tumour and tumour milieu can dictate if the tumour microenvironment (TME) supports either a pro-malignancy or an anti-malignancy phenotype. Identification of the factors and cell types that regulate the dysfunction of the TME is crucial in order to understand and modulate the immune status of tumours. Among these cell types, tumour-associated fibroblasts are emerging as a major component of the TME that is often correlated with poor prognosis and therapy resistance, including immunotherapies. Thus, a deeper understanding of the complex roles of tumour-associated fibroblasts in regulating tumour immunity and cancer therapy could provide new insight into targeting the TME in various human cancers. In this review, we summarize recent studies investigating the role of immune and key stromal cells in regulating the immune status of the TME and discuss the therapeutic potential of targeting stromal cells, especially tumour-associated fibroblasts, within the TME as an adjuvant therapy to sensitize immunosuppressive tumours and prevent cancer progression, chemo-resistance and metastasis.

3D Breast Tumor Models for Radiobiology Applications

Breast cancer is a leading cause of cancer-associated death in women. The clinical management of breast cancers is normally carried out using a combination of chemotherapy, surgery and radiation therapy. The majority of research investigating breast cancer therapy until now has mainly utilized two-dimensional (2D) in vitro cultures or murine models of disease. However, there has been significant uptake of three-dimensional (3D) in vitro models by cancer researchers over the past decade, highlighting a complimentary model for studies of radiotherapy, especially in conjunction with chemotherapy. In this review, we underline the effects of radiation therapy on normal and malignant breast cells and tissues, and explore the emerging opportunities that pre-clinical 3D models offer in improving our understanding of this treatment modality.

Chemokine Receptor Antagonists: Role in Oncology

PURPOSE OF REVIEW

To evaluate the clinical potential of chemokine receptor antagonists for the treatment of patients with cancer.

RECENT FINDINGS

Chemokine receptors and their ligands can have a significant impact on the infiltration of cells into the tumor microenvironment. The receptors are increasingly being investigated as targets for the treatment of cancers. Recent studies are demonstrating the promise of chemokine receptor antagonists in this setting. There are many chemokine receptors, and each can have different functions depending on the cellular context. Targeting chemokine receptors is a promising strategy in both pre-clinical research and clinical trials. Inhibiting chemokine receptors that either recruit suppressive cells or improve cancer mobility and viability while sparing those necessary for proper immune trafficking may prove to dramatically improve treatment responses. Further research in this area is warranted and has the potential to dramatically improve patient outcomes.

At the Bench: Pre-clinical evidence for multiple functions of CXCR4 in cancer

Signaling through chemokine receptor, C-X-C chemokine receptor type 4 (CXCR4) regulates essential processes in normal physiology, including embryogenesis, tissue repair, angiogenesis, and trafficking of immune cells. Tumors co-opt many of these fundamental processes to directly stimulate proliferation, invasion, and metastasis of cancer cells. CXCR4 signaling contributes to critical functions of stromal cells in cancer, including angiogenesis and multiple cell types in the tumor immune environment. Studies in animal models of several different types of cancers consistently demonstrate essential functions of CXCR4 in tumor initiation, local invasion, and metastasis to lymph nodes and distant organs. Data from animal models support clinical observations showing that integrated effects of CXCR4 on cancer and stromal cells correlate with metastasis and overall poor prognosis in >20 different human malignancies. Small molecules, Abs, and peptidic agents have shown anticancer efficacy in animal models, sparking ongoing efforts at clinical translation for cancer therapy. Investigators also are developing companion CXCR4-targeted imaging agents with potential to stratify patients for CXCR4-targeted therapy and monitor treatment efficacy. Here, pre-clinical studies demonstrating functions of CXCR4 in cancer are reviewed.

CXCR4 antagonism sensitizes cancer cells to novel indole-based MDM2/4 inhibitors in glioblastoma multiforme

Glioblastoma Multiforme (GBM) is a highly invasive primary brain tumour characterized by chemo- and radio-resistance and poor overall survival. GBM can present an aberrant functionality of p53, caused by the overexpression of the murine double minute 2 protein (MDM2) and its analogue MDM4, which may influence the response to conventional therapies. Moreover, tumour resistance/invasiveness has been recently attributed to an overexpression of the chemokine receptor CXCR4, identified as a pivotal mediator of glioma neovascularization. Notably, CXCR4 and MDM2-4 cooperate in promoting tumour invasion and progression. Although CXCR4 actively promotes MDM2 activation leading to p53 inactivation, MDM2-4 knockdown induces the downregulation of CXCR4 gene transcription. Our study aimed to assess if the CXCR4 signal blockade could enhance glioma cells' sensitivity to the inhibition of the p53-MDMs axis. Rationally designed inhibitors of MDM2/4 were combined with the CXCR4 antagonist, AMD3100, in human GBM cells and GBM stem-like cells (neurospheres), which are crucial for tumour recurrence and chemotherapy resistance. The dual MDM2/4 inhibitor RS3594 and the CXCR4 antagonist AMD3100 reduced GBM cell invasiveness and migration in single-agent treatment and mainly in combination. AMD3100 sensitized GBM cells to the antiproliferative activity of RS3594. It is noteworthy that these two compounds present synergic effects on cancer stem components: RS3594 inhibited the growth and formation of neurospheres, AMD3100 induced differentiation of neurospheres while enhancing RS3594 effectiveness preventing their proliferation/clonogenicity. These results confirm that blocking CXCR4/MDM2/4 represents a valuable strategy to reduce GBM proliferation and invasiveness, acting on the stem cell component too.

The Effect of Hypoxia on the Expression of CXC Chemokines and CXC Chemokine Receptors-A Review of Literature

Hypoxia is an integral component of the tumor microenvironment. Either as chronic or cycling hypoxia, it exerts a similar effect on cancer processes by activating hypoxia-inducible factor-1 (HIF-1) and nuclear factor (NF-κB), with cycling hypoxia showing a stronger proinflammatory influence. One of the systems affected by hypoxia is the CXC chemokine system. This paper reviews all available information on hypoxia-induced changes in the expression of all CXC chemokines (CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8 (IL-8), CXCL9, CXCL10, CXCL11, CXCL12 (SDF-1), CXCL13, CXCL14, CXCL15, CXCL16, CXCL17) as well as CXC chemokine receptors—CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. First, we present basic information on the effect of these chemoattractant cytokines on cancer processes. We then discuss the effect of hypoxia-induced changes on CXC chemokine expression on the angiogenesis, lymphangiogenesis and recruitment of various cells to the tumor niche, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T cells (T_regs) and tumor-infiltrating lymphocytes (TILs). Finally, the review summarizes data on the use of drugs targeting the CXC chemokine system in cancer therapies.

The Recombinant Protein Based on Trypanosoma cruzi P21 Interacts With CXCR4 Receptor and Abrogates the Invasive Phenotype of Human Breast Cancer Cells

Trypanosoma cruzi P21 is a protein secreted by the parasite that plays biological roles directly involved in the progression of Chagas disease. The recombinant protein (rP21) demonstrates biological properties, such as binding to CXCR4 receptors in macrophages, chemotactic activity of immune cells, and inhibiting angiogenesis. This study aimed to verify the effects of rP21 interaction with CXCR4 from non-tumoral cells (MCF-10A) and triple-negative breast cancer cells (MDA-MB-231). Our data showed that the MDA-MB-231 cells expressed higher levels of CXCR4 than did the non-tumor cell lines. Besides, cytotoxicity assays using different concentrations of rP21 showed that the recombinant protein was non-toxic and was able to bind to the cell membranes of both cell lineages. In addition, rP21 reduced the migration and invasion of MDA-MB-231 cells by the downregulation of MMP-9 gene expression. In addition, treatment with rP21 blocked the cell cycle, arresting it in the G1 phase, mainly in MDA-MB-231 cells. Finally, rP21 prevents the chemotaxis and proliferation induced by CXCL12. Our data showed that rP21 binds to the CXCR4 receptors in both cells, downregulates CXCR4 gene expression, and decreases the receptors in the cytoplasm of MDA-MB-231 cells, suggesting CXCR4 internalization. This internalization may explain the desensitization of the receptors in these cells. Thus, rP21 prevents migration, invasion, and progression in MDA-MB-231 cells.

The Signaling Duo CXCL12 and CXCR4: Chemokine Fuel for Breast Cancer Tumorigenesis

Simple Summary

Breast cancer remains the most common malignancy in women. In this review, we explore the role of the CXCL12/CXCR4 pathway in breast cancer. We show that the CXCL12/CXCR4 cascade is involved in nearly every aspect of breast cancer tumorigenesis including proliferation, cell motility and distant metastasis. Moreover, we summarize current knowledge about the CXCL12/CXCR4-targeted therapies. Due to the critical roles of this pathway in breast cancer and other malignancies, we believe that audiences in different fields will find this overview helpful.

Abstract

The CXCL12/CXCR4 signaling pathway has emerged in the recent years as a key player in breast cancer tumorigenesis. This pathway controls many aspects of breast cancer development including cancer cell proliferation, motility and metastasis to all target organs. Moreover, the CXCL12/CXCR4 cascade affects both immune and stromal cells, creating tumor-supporting microenvironment. In this review, we examine state-of-the-art knowledge about detrimental roles of the CXCL12/CXCR4 signaling, discuss its therapeutic potential and suggest further research directions beneficial both for basic research and personalized medicine in breast cancer.

Cancer stem cell secretome in the tumor microenvironment: a key point for an effective personalized cancer treatment

Cancer stem cells (CSCs) represent a tumor subpopulation responsible for tumor metastasis and resistance to chemo- and radiotherapy, ultimately leading to tumor relapse. As a consequence, the detection and eradication of this cell subpopulation represent a current challenge in oncology medicine. CSC phenotype is dependent on the tumor microenvironment (TME), which involves stem and differentiated tumor cells, as well as different cell types, such as mesenchymal stem cells, endothelial cells, fibroblasts and cells of the immune system, in addition to the extracellular matrix (ECM), different in composition to the ECM in healthy tissues. CSCs regulate multiple cancer hallmarks through the interaction with cells and ECM in their environment by secreting extracellular vesicles including exosomes, and soluble factors such as interleukins, cytokines, growth factors and other metabolites to the TME. Through these factors, CSCs generate and activate their own tumor niche by recruiting stromal cells and modulate angiogenesis, metastasis, resistance to antitumor treatments and their own maintenance by the secretion of different factors such as IL-6, VEGF and TGF-ß. Due to the strong influence of the CSC secretome on disease development, the new antitumor therapies focus on targeting these communication networks to eradicate the tumor and prevent metastasis, tumor relapse and drug resistance. This review summarizes for the first time the main components of the CSC secretome and how they mediate different tumor processes. Lastly, the relevance of the CSC secretome in the development of more precise and personalized antitumor therapies is discussed.

CXCR4 Antagonist AMD3100 Reverses the Resistance to Tamoxifen in Breast Cancer via Inhibiting AKT Phosphorylation

Endocrine therapy is a systemic therapy and has become the main treatment strategy for patients with estrogen receptor (ER)-positive breast cancer. However, tamoxifen resistance has become an insurmountable clinical challenge, and the underlying mechanisms are still poorly understood. In this study, we explored the roles of CXC chemokine receptor type 4 (CXCR4) in tamoxifen-treated breast cancer and tamoxifen resistance. Based on the Gene Expression Omnibus (GEO) database, high expression of CXCR4 was found to be associated with worse overall survival (hazard ratio [HR] = 4.646, p < 0.001) and cancer-specific survival (HR = 4.480, p < 0.001) in tamoxifen-treated breast cancer. CXCR4 was also positively correlated with the level of AKT phosphorylation and the resistance to tamoxifen in breast cancer. AMD3100 is a CXCR4 antagonist and was found to decrease phosphorylated (p)-AKT levels of tamoxifen-resistant cells. The reversal effect of AMD3100 on tamoxifen resistance was also confirmed in vitro and in vivo. Taken together, our study demonstrated that CXCR4 could be a potential prognostic biomarker for tamoxifen-treated breast cancer, and the combination of AMD3100 with tamoxifen could be a more efficacious therapeutic strategy for the treatment of tamoxifen resistance.

CXCR4 antagonist AMD3100 (plerixafor): From an impurity to a therapeutic agent

AMD3100 (plerixafor), a CXCR4 antagonist, has opened a variety of avenues for potential therapeutic approaches in different refractory diseases. The CXCL12/CXCR4 axis and its signaling pathways are involved in diverse disorders including HIV-1 infection, tumor development, non-Hodgkin lymphoma, multiple myeloma, WHIM Syndrome, and so on. The mechanisms of action of AMD3100 may relate to mobilizing hematopoietic stem cells, blocking infection of X4 HIV-1, increasing circulating neutrophils, lymphocytes and monocytes, reducing myeloid-derived suppressor cells, and enhancing cytotoxic T-cell infiltration in tumors. Here, we first revisit the pharmacological discovery of AMD3100. We then review monotherapy of AMD3100 and combination use of AMD3100 with other agents in various diseases. Among those, we highlight the perspective of AMD3100 as an immunomodulator to regulate immune responses particularly in the tumor microenvironment and synergize with other therapeutics. All the pre-clinical studies support the clinical testing of the monotherapy and combination therapies with AMD3100 and further development for use in humans.

The effect of combining Endostar with radiotherapy on blood vessels, tumor-associated macrophages, and T cells in brain metastases of Lewis lung cancer

Background

Combining Endostar (ES) with radiotherapy (RT) has shown a promising therapeutic effect on non-small cell lung carcinoma with brain metastases (BMs) in clinical practice. However, the specific mechanism is not yet fully understood. The present study aimed to investigate the effects of ES on blood vessels, tumor-associated macrophages (TAMs), and T cells in a tumor microenvironment treated with RT.

Methods

BM models were established by stereotactic and intracarotid injection of luciferase-Lewis lung cancer (LLC) cells into female C57BL mice. The animals were randomly divided into 4 groups: normal saline (NS), ES, RT, and ES plus radiotherapy (ES + RT) groups. Tumor size was determined with the IVIS imaging system. Tumor specimens were stained with CD34 and α-SMA to investigate tumor vascular changes. The proportions of TAMs, CD4⁺ T cells, and CD8⁺ T cells in tumor tissues were determined by flow cytometry and immunofluorescence. The expressions of hypoxia-inducible factor 1α (HIF-1α) and CXCR4 were deduced using western blotting and immunohistochemistry (IHC).

Results

ES + RT significantly suppressed tumor growth compared to the other 3 groups. RT decreased M1 and increased M2 in microglial cells and bone marrow-derived macrophages (BMDMs) relative to NS, while ES had the opposite effect. The ratio of CD8⁺T/CD4⁺T was increased in the ES + RT group compared to the other 3 groups. Tumor vascular maturity (α-SMA⁺/CD34⁺) was increased while HIF-1α was significantly suppressed in the ES + RT group. CXCR4 expression, which is involved in TAM recruitment, increased following RT, whereas, ES attenuated its expression.

Conclusions

Our findings suggest that ES can promote the normalization of tumor blood vessels and increase the anti-tumor immune-related immune cells infiltrating the tumor following RT treatment.

The Anti-Angiogenic Effects of Anti-Human Immunodeficiency Virus Drugs

The growth and metastasis of malignant tumors benefit from the formation of blood vessels within the tumor area. There, new vessels originate from angiogenesis (the sprouting of pre-existing neighboring vessels) and/or vasculogenesis (the mobilization of bone marrow-derived endothelial cell precursors which incorporate in tumor vasculature and then differentiate into mature endothelial cells). These events are induced by soluble molecules (the angiogenic factors) and modulated by endothelial cell interactions with the perivascular matrix. Given angiogenesis/vasculogenesis relevance to tumor progression, anti-angiogenic drugs are often employed to buttress surgery, chemotherapy or radiation therapy in the treatment of a wide variety of cancers. Most of the anti-angiogenic drugs have been developed to functionally impair the angiogenic vascular endothelial growth factor: however, this leaves other angiogenic factors unaffected, hence leading to drug resistance and escape. Other anti-angiogenic strategies have exploited classical inhibitors of enzymes remodeling the perivascular matrix. Disappointingly, these inhibitors have been found toxic and/or ineffective in clinical trials, even though they block angiogenesis in pre-clinical models. These findings are stimulating the identification of other anti-angiogenic compounds. In this regard, it is noteworthy that drugs utilized for a long time to counteract human immune deficiency virus (HIV) can directly and effectively hamper molecular pathways leading to blood vessel formation. In this review the mechanisms leading to angiogenesis and vasculogenesis, and their susceptibility to anti-HIV drugs will be discussed.

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.

CXCL12-CXCL4 heterodimerization prevents CXCL12-driven breast cancer cell migration

Despite improvements in cancer early detection and treatment, metastatic breast cancer remains deadly. Current therapeutic approaches have very limited efficacy in patients with triple negative breast cancer. Among the many mechanisms associated that contribute to cancer progression, signaling through the CXCL12-CXCR4 is an essential step in cancer cell migration. We previously demonstrated the formation of CXCL12-CXCL4 heterodimers (Carlson et al., 2013). Here, we investigated whether CXCL12-CXCL4 heterodimers alter tumor cell migration. CXCL12 alone dose-dependently promoted the MDA-MB 231 cell migration (p < .05), which could be prevented by blocking the CXCR4 receptor. The addition of CXCL4 inhibited the CXCL12-induced cell migration (p < .05). Using NMR spectroscopy, we identified the CXCL4-CXCL12 binding interface. Moreover, we generated a CXCL4-derived peptide homolog of the binding interface that mimicked the activity of native CXCL4 protein. These results confirm the formation of CXCL12-CXCL4 heterodimers and their inhibitory effects on the migration of breast tumors cells. These findings suggest that specific peptides mimicking heterodimerization of CXCL12 might prevent breast cancer cell migration.

Ionizing radiation effects on the tumor microenvironment

The broad use of radiotherapy (RT) in the management of solid human tumors is based on its ability to damage cellular macromolecules, particularly the DNA, effectively inducing growth arrest and cell death locally in irradiated tumor cells. However, bystander effects, such as the transmission of lethal signals between cells via gap junctions or the production of diffusible cytotoxic mediators, can also contribute to the local antineoplastic action of RT. Traditionally, RT has been considered to exert immunosuppressive effects on the host. This idea largely stems from the radiosensitivity of quiescent lymphocytes and on the use of total body irradiation as part of myeloablative conditioning regimens preceding hematopoietic stem cell transplantation. Additionally, the occurrence of the so-called "abscopal effect," where nonirradiated distant lesions display effects of RT response, suggests that RT may also induce tumor immunization. Several RT-induced effects on cancer, immune and stromal cells, contribute to the abscopal effect: (1) induction of "immunogenic cell death", with release of tumor-associated antigens, (2) alterations of cancer cell immunophenotype, and (3) modulation of the tumor microenvironment. Damage and death of cancer cells leads to the surface exposure of immunogenic molecules as well as the release of damage associated molecular patterns such as adenosine triphosphate or High-Mobility-Group-Protein B1, and potentially tumor antigens that activate the innate and adaptive immune systems. Moreover, nuclear release and cytoplasmic sensing of altered nucleic acids via cyclic GMP-AMP Synthase/Stimulator of Interferon Genes is connected to the secretion of cytokines that support innate and adaptive antitumor immunity. As a result of the above, irradiated tumor cells may potentially act as an "in situ vaccine."

The prognosis comparison of different molecular subtypes of breast tumors after radiotherapy and the intrinsic reasons for their distinct radiosensitivity

Radiotherapy can increase the cell cycle arrest that promotes apoptosis, reduces the risk of tumor recurrence and has become an irreplaceable component of systematic treatment for patients with breast cancer. Substantial advances in precise radiotherapy unequivocally indicate that the benefits of radiotherapy vary depending on intrinsic subtypes of the disease; luminal A breast cancer has the highest benefit whereas human epidermal growth factor receptor 2 (HER2)-positive and triple negative breast cancer (TNBC) are affected to a lesser extent irrespective of the selection of radiotherapy strategies, such as conventional whole-breast irradiation (CWBI), accelerated partial-breast irradiation (APBI), and hypofractionated whole-breast irradiation (HWBI). The benefit disparity correlates with the differential invasiveness, malignance, and radiosensitivity of the subtypes. A combination of a number of molecular mechanisms leads to the strong radioresistant profile of HER2-positive breast cancer, and sensitization to irradiation can be induced by multiple drugs or compounds in luminal disease and TNBC. In this review, we aimed to summarize the prognostic differences between various subtypes of breast tumors after CWBI, APBI, and HWBI, the potential reasons for drug-enhanced radiosensitivity in luminal breast tumors and TNBC, and the robust radioresistance of HER2-positive cancer.

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Mozobil® (Plerixafor, AMD3100), 10 years after its approval by the US Food and Drug Administration

AMD3100 (plerixafor, Mozobil®) was first identified as an anti-HIV agent specifically active against the T4-lymphotropic HIV strains, as it selectively blocked the CXCR4 receptor. Through interference with the interaction of CXCR4 with its natural ligand, SDF-1 (also named CXCL12), it also mobilized the CD34⁺stem cells from the bone marrow into the peripheral blood stream. In December 2008, AMD3100 was formally approved by the US FDA for autologous transplantation in patients with Non-Hodgkin’s Lymphoma or multiple myeloma. It may be beneficially used in various other malignant diseases as well as hereditary immunological disorders such as WHIM syndrome, and physiopathological processes such as hepatopulmonary syndrome.

The significance of chemokines in diffuse large B-cell lymphoma: a systematic review and future insights

Despite the progress made in molecular and clinical research, patients with diffuse large B-cell lymphoma (DLBCL) still have a bad prognosis. Recently, chemokines/chemokine receptors have become the subject of interest in relation to DLBCL. Studies have demonstrated the important role of chemokines/chemokine receptors in the communication between DLBCL cells and tumor microenvironment. Studies have also reported the ability of chemokines/chemokine receptors in promoting the proliferation and invasion of DLBCL cells. Here, we summarize the data on mechanisms of DLBCL supporting the involvement of chemokine/chemokine receptor changes. We focus on the available evidence regarding chemokines/chemokine receptors as biomarkers and therapeutic targets for DLBCL.

Potential Role of CXCR4 Targeting in the Context of Radiotherapy and Immunotherapy of Cancer

Cancer immunotherapy has been established as standard of care in different tumor entities. After the first reports on synergistic effects with radiotherapy and the induction of abscopal effects-tumor shrinkage outside the irradiated volume attributed to immunological effects of radiotherapy-several treatment combinations have been evaluated. Different immunotherapy strategies (e.g., immune checkpoint inhibition, vaccination, cytokine based therapies) have been combined with local tumor irradiation in preclinical models. Clinical trials are ongoing in different cancer entities with a broad range of immunotherapeutics and radiation schedules. SDF-1 (CXCL12)/CXCR4 signaling has been described to play a major role in tumor biology, especially in hypoxia adaptation, metastasis and migration. Local tumor irradiation is a known inducer of SDF-1 expression and release. CXCR4 also plays a major role in immunological processes. CXCR4 antagonists have been approved for the use of hematopoietic stem cell mobilization from the bone marrow. In addition, several groups reported an influence of the SDF-1/CXCR4 axis on intratumoral immune cell subsets and anti-tumor immune response. The aim of this review is to merge the knowledge on the role of SDF-1/CXCR4 in tumor biology, radiotherapy and immunotherapy of cancer and in combinatorial approaches.

GPCR Modulation in Breast Cancer

Breast cancer is the most prevalent cancer found in women living in developed countries. Endocrine therapy is the mainstay of treatment for hormone-responsive breast tumors (about 70% of all breast cancers) and implies the use of selective estrogen receptor modulators and aromatase inhibitors. In contrast, triple-negative breast cancer (TNBC), a highly heterogeneous disease that may account for up to 24% of all newly diagnosed cases, is hormone-independent and characterized by a poor prognosis. As drug resistance is common in all breast cancer subtypes despite the different treatment modalities, novel therapies targeting signaling transduction pathways involved in the processes of breast carcinogenesis, tumor promotion and metastasis have been subject to accurate consideration. G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors involved in the development and progression of many tumors including breast cancer. Here we discuss data regarding GPCR-mediated signaling, pharmacological properties and biological outputs toward breast cancer tumorigenesis and metastasis. Furthermore, we address several drugs that have shown an unexpected opportunity to interfere with GPCR-based breast tumorigenic signals.