AMD3100 reduces CXCR4-mediated survival and metastasis of osteosarcoma by inhibiting JNK and Akt, but not p38 or Erk1/2, pathways in in vitro and mouse experiments

Evaluation of the influence of the C-X-C motif chemokine ligand 12 / C-X-C chemokine receptor 4 axis on canine mammary gland tumor cell migration

C-X-C motif chemokine ligand 12 (CXCL12) is one of the chemokines that binds to C-X-C chemokine receptor 4 (CXCR4) on tumor cell membranes and induces chemotaxis and/or migration. Mammary gland tumors (MGT) are the most common neoplasms in intact female dogs, with local invasion and distant metastasis regarded as problems. However, the influence of the CXCL12/CXCR4 axis on canine MGT cell migration has not been elucidated. This study aimed to evaluate the expression of CXCL12 and CXCR4 in canine MGT cells and tissues and investigate the influence of CXCL12 protein on the migratory ability of MGT cells. CXCL12 expression was evaluated in 10 canine malignant MGT tissues. CXCL12 expression in tumor cells was identified in all examined tissues; however, the staining pattern and intensity differed between the tumors. Immunocytochemistry revealed three canine MGT cell lines as CXCR4-positive. Migratory ability was evaluated using a wound healing assay, and the migration of CXCR4-positive MGT cells was significantly activated by the addition of CXCL12 protein. This influence was canceled by pre-treatment with a CXCR4 antagonist. The results of our study suggest that the CXCL12/CXCR4 axis may be associated with the migration of canine MGT.

Mycobacterium indicus pranii therapy suppresses systemic dissemination of tumor cells in B16F10 murine model of melanoma

Cancer associated morbidity is mostly attributed to the dissemination of tumor cells from their primary niche into the circulation known as "metastasis". Mycobacterium indicus pranii (MIP) an approved immunotherapeutic agent against lung cancer (NSCLC) has shown potent anti-tumor activity in prior studies. While evaluating anti-tumor activity of MIP in mouse model, MIP treated animals typically exhibited less metastatic lesions in their pulmonary compartment. To study the role of MIP in metastasis closely, B16F10 melanoma cells were implanted subcutaneously in the mice, and the dissemination of tumor cells from the solid tumor was evaluated over a period of time. When B16F10 melanoma cells were treated with MIP in vitro, downregulation of epithelial mesenchymal transition markers was observed in these cells, which in turn suppressed the invasion, migration and adhesion of tumor cells. Notably, MIP therapy was found to be effectively reducing the metastatic burden in murine model of melanoma. Molecular characterization of MIP treated tumor cells substantiated that MIP upregulates the PPARγ expression within the tumor cells, which attenuates the NFκB/p65 levels within the nucleus, resulting in the suppression of Mmp9 expression in tumor cells. Besides that, MIP also downregulated the surface expression of chemokine receptor CXCR4 in murine melanoma cells, where chromatin immunoprecipitation confirmed the impeded recruitment of p50 and c-Rel factors to the Cxcr4 promoter, resulting in its downregulation transcriptionally. Taken together, MIP suppressed the dissemination of tumor cells in vivo, by regulating the expression of MMP9 and CXCR4 on these cells.

Clinicopathological and prognostic significance of CXCR4 expression in osteosarcoma: a meta-analysis

Background

C-X-C Motif Chemokine Receptor (CXCR4) is an oncogene that widely studied and associated with worse clinicopathological features and prognosis outcome on many types of cancer. Beside that, significance of CXCR4 expression on clinicopathological features and prognostic on osteosarcoma (OS) require further validation.

Aim

We conducted a meta-analysis to evaluate association between positive CXCR4 expression with clinicopathological features, and prognosis in OS.

Methods

Literature searches on Pubmed, Cochrane Library and Web of Science was conducted systematically up to December 2021 to find relevant references. Effect of CXCR4 expression on clinicopathological characteristic and prognostic were analyzed using Review Manager 5.4 (Cochrane Collaboration, Oxford, UK). Significance value less than 0.05 was considered statistically significant.

Results

By considering inclusion and exclusion criteria, 940 patients from 12 studies were suitable to included in qualitative analysis, and 10 studies were suitable for quantitative analysis. Association between CXCR4 expression and OS clinicopathological features was found significant on metastasis (OR = 4.01, 95%CI = 1.58-10.18; p = 0.003), stage (stage III & IV vs I & II, OR = 6.52, 95%CI = 1.05-40.62; p = 0.04), and tumor primary site (femur/tibia vs other, OR = 1.60, 95%CI = 1.04-2.45; p = 0.03), but not associated with histological type, gender, and age. Furthermore, CXCR4 expression is associated with poor overall survival in OS (HR = 2.13, 95%CI = 1.78-2.55; p < 0.001).

Conclusion

In conclusion, the results of our meta-analysis suggest that CXCR4 expression may be valuable as a histopathological predictor of poor clinicopathological features and prognosis of OS.

The Relationship between PBLS and Osteosarcoma Distribution in Different Subgroups and the Survival and Prognosis of Osteosarcoma

Objective

To analyze the differences in the distribution of lymphocytes (PBLS) in different subgroups of osteosarcoma (OS) and the predictive value of related parameters on the survival prognosis of OS.

Methods

For retrospective analysis, 80 patients with malignant OS diagnosed and treated in our hospital from June 2016 to June 2017 were selected as the observation group, and 80 patients with benign bone tumors during the same period were selected as the control group. Patients in the observation group were followed up for three years and grouped according to the tumor diameter, stage, metastasis, and prognosis. Fasting venous blood was collected from each group and the levels of CD3+, CD3+CD4+, and CD3+CD8+ were detected. Meanwhile, the ratio of CD4+/CD8+, CD4+/CD3+, and CD8+/CD3+ was calculated and compared. Kaplan-Meier survival curve was used to analyze the relationship between PBLS parameters and OS survival. The area under the curve (AUC), sensitivity, and specificity of each entry index were analyzed by the receiver operating characteristic curve (ROC curve).

Results

The CD3+CD8+ level and CD4+/CD3+ ratio in the observation group were significantly higher than those in the control group (P < 0.05). The level of CD3+CD8+ in the patients with tumor diameter ≥ 11 cm was observably higher than that in the patients with tumor diameter <11 cm (P < 0.05). The levels of CD3+CD4+ and the ratio of CD4+/CD8 and CD4+/CD3+ of patients in stage III were markedly lower than those of patients in stage II, while the ratio of CD8+/CD3+ and the levels of CD3+CD8+ were prominently higher than those of patients in stage II (P < 0.05). The CD3+CD4+ level and CD4+/CD3+ ratio of patients in the metastatic group before treatment, the metastatic group after treatment, and the nonmetastatic group after treatment increased successively, while the ratio of CD4+/CD8+ and CD8+/CD3+ and the level of CD3+CD8+ decreased successively (P < 0.05). The CD3+CD4+ level and CD4+/CD3+ ratio in the poor prognosis group were significantly higher than those in the good prognosis group, whereas the ratio of CD8+/CD3+ and CD4+/CD8+ and the level of CD3+CD8+ were significantly lower than those in the poor prognosis group (P < 0.05). ROC curve analysis showed that the AUC of CD4+/CD8+ and CD4+/CD3+ in predicting poor prognosis in patients with OS was notably higher than other indicators, which were 0.818 and 0.866, respectively (P < 0.05). Kaplan-Meier survival curve results revealed that patients with CD3+CD4+ ≤ 5.15, CD3+CD8+ > 3.85, CD4+/CD8+ ≤ 1.42, CD4+/CD3+ ≤ 0.50, and CD8+/CD3+ > 0.38 had longer survival.

Conclusion

The distribution of PBLS parameters varied widely among different subgroups of OS. Patients with poor prognosis had a higher ratio of CD4+/CD8+ and CD4+/CD3+, which were related to the survival of patients with OS. Moreover, both the ratio of CD4+/CD8+ and CD4+/CD3+ had certain predictive values in terms of survival and prognosis of OS. Therefore, regular clinical monitoring of patients' immune function could help predict disease changes and assess prognosis.

Tumor-promoting myeloid cells in the pathogenesis of human oncoviruses: potential targets for immunotherapy

Oncoviruses, known as cancer-causing viruses, are typically involved in cancer progression by inhibiting tumor suppressor pathways and uncontrolled cell division. Myeloid cells are the most frequent populations recruited to the tumor microenvironment (TME) and play a critical role in cancer development and metastasis of malignant tumors. Tumor-infiltrating myeloid cells, including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), tumor-associated dendritic cells (TADCs), and tumor-associated neutrophils (TANs) exert different states from anti-tumorigenic to pro-tumorigenic phenotypes in TME. Although their role in the anti-tumorigenic state is well introduced, their opposing roles, pro-tumorigenic activities, such as anti-inflammatory cytokine and reactive oxygen species (ROS) production, should not be ignored since they result in inflammation, tumor progression, angiogenesis, and evasion. Since the blockade of these cells had promising results against cancer progression, their inhibition might be helpful in various cancer immunotherapies. This review highlights the promoting role of tumor-associated myeloid cells (TAMCs) in the pathophysiology of human virus tumorigenesis.

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.

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.

Metastatic human hepatoblastoma cells exhibit enhanced tumorigenicity, invasiveness and a stem cell-like phenotype

BACKGROUND/PURPOSE

Metastatic hepatoblastoma continues to pose a significant treatment challenge, primarily because the precise mechanisms involved in metastasis are not fully understood, making cell lines and preclinical models that depict the progression of disease and metastasis-related biology paramount. We aimed to generate and characterize a metastatic hepatoblastoma cell line to create a model for investigation of the molecular mechanisms associated with metastasis.

MATERIALS/METHODS

Using a murine model of serial tail vein injections of the human hepatoblastoma HuH6 cell line, non-invasive bioluminescence imaging, and dissociation of metastatic pulmonary lesions, we successfully established and characterized the metastatic human hepatoblastoma cell line, HLM_3.

RESULTS

The HLM_3 cells exhibited enhanced tumorigenicity and invasiveness, both in vitro and in vivo compared to the parent HuH6 cell line. Moreover, HLM_3 metastatic hepatoblastoma cells exhibited a stem cell-like phenotype and were more resistant to the standard chemotherapeutic cisplatin.

CONCLUSION

This newly described metastatic hepatoblastoma cell line offers a novel tool to study mechanisms of tumor metastasis and evaluate new therapeutic strategies for metastatic hepatoblastoma.

Molecular sensors for detection of tumor-stroma crosstalk

In most solid tumors, malignant cells coexist with non-cancerous host tissue comprised of a variety of extracellular matrix components and cell types, notably fibroblasts, immune cells, and endothelial cells. It is becoming increasingly evident that the non-cancerous host tissue, often referred to as the tumor stroma or the tumor microenvironment, wields tremendous influence in the proliferation, survival, and metastatic ability of cancer cells. The tumor stroma has an active biological role in the transmission of signals, such as growth factors and chemokines that activate oncogenic signaling pathways by autocrine and paracrine mechanisms. Moreover, the constituents of the stroma define the mechanical properties and the physical features of solid tumors, which influence cancer progression and response to therapy. Inspired by the emerging importance of tumor-stroma crosstalk and oncogenic physical forces, numerous biosensors, or advanced imaging and analysis techniques have been developed and applied to investigate complex and challenging questions in cancer research. These techniques facilitate measurements and biological readouts at scales ranging from subcellular to tissue-level with unprecedented level of spatial and temporal precision. Here we examine the application of biosensor technology for studying the complex and dynamic multiscale interactions of the tumor-host system.

Osteosarcoma and Metastasis

Osteosarcoma is the most common primary bone malignancy in adolescents. Its high propensity to metastasize is the leading cause for treatment failure and poor prognosis. Although the research of osteosarcoma has greatly expanded in the past decades, the knowledge and new therapy strategies targeting metastatic progression remain sparse. The prognosis of patients with metastasis is still unsatisfactory. There is resonating urgency for a thorough and deeper understanding of molecular mechanisms underlying osteosarcoma to develop innovative therapies targeting metastasis. Toward the goal of elaborating the characteristics and biological behavior of metastatic osteosarcoma, it is essential to combine the diverse investigations that are performed at molecular, cellular, and animal levels from basic research to clinical translation spanning chemical, physical sciences, and biology. This review focuses on the metastatic process, regulatory networks involving key molecules and signaling pathways, the role of microenvironment, osteoclast, angiogenesis, metabolism, immunity, and noncoding RNAs in osteosarcoma metastasis. The aim of this review is to provide an overview of current research advances, with the hope to discovery druggable targets and promising therapy strategies for osteosarcoma metastasis and thus to overcome this clinical impasse.

Potential Strategies to Improve the Effectiveness of Drug Therapy by Changing Factors Related to Tumor Microenvironment

A tumor microenvironment (TME) is composed of various cell types and extracellular components. It contains tumor cells and is nourished by a network of blood vessels. The TME not only plays a significant role in the occurrence, development, and metastasis of tumors but also has a far-reaching impact on the effect of therapeutics. Continuous interaction between tumor cells and the environment, which is mediated by their environment, may lead to drug resistance. In this review, we focus on the key cellular components of the TME and the potential strategies to improve the effectiveness of drug therapy by changing their related factors.

SOX17 inhibits proliferation and invasion of neuroblastoma through CXCL12/CXCR4 signaling axis

SOX17 has been shown to be involved in the transcriptional regulation of CXCR4, and CXCL12 functions by binding to its receptor CXCR4. Here, we explored the expression of SOX17 in neuroblastoma (NB), its mutual regulation with CXCL12, and its effects on cancer cell proliferation, migration and invasion. Five human NB cell lines and 15 pairs of NB and adjacent tissue specimens were used, to conduct RT-qPCR, immunohistochemistry, western blot, ELISA, CCK-8, colony formation, Edu, transwell, chromatin immunoprecipitation (ChIP), and dual-luciferase assays, to study the role of SOX17 in NB. SOX17 levels were reduced in both NB tissues and cell lines. SOX17 inhibited NB tumor growth, migration and invasion in vivo and suppressed NB cell proliferation, migration, and invasion in vitro. SOX17 knockdown or overexpression revealed a negative correlation between SOX17 and CXCL12/CXCR4 pathway activation. ChIP and dual-luciferase assays in NB cells demonstrated that SOX17 significantly inhibited CXCL12 gene and protein levels by binding to CXCL12 promoter regions. In vivo and in vitro experiments using the CXCR4 antagonist, AMD3100, demonstrated that cell proliferation, migration and invasion were significantly abrogated by AMD3100 in NB cells with SOX17 knocked down. Further, AMD3100 impaired growth of NB tumors with SOX17 knocked down in mice. Importantly, SOX17 bound to the CXCL12 promoter, which then activated downstream targets to regulate cell viability, proliferation, and migration. In conclusion, our data demonstrate that SOX17 expression is repressed in NB tissues and cells, and that SOX17 suppresses NB tumor formation and proliferation through inhibition of CXCL12/CXCR4 signaling.

CXCR4 blockade sensitizes osteosarcoma to doxorubicin by inducing autophagic cell death via PI3K‑Akt‑mTOR pathway inhibition

Doxorubicin is one of the most frequently used chemotherapy drugs in the treatment of osteosarcoma (OS), but the emergence of chemoresistance often leads to treatment failure. C-X-C motif chemokine receptor 4 (CXCR4) has been demonstrated to regulate OS progression and metastasis. However, whether CXCR4 is also involved in OS chemoresistance and its molecular mechanisms has yet to be fully elucidated. In the present study, CXCR4-mediated autophagy for OS chemotherapy was investigated by western blot analysis, transmission electron microscopy and confocal microscopy. CXCR4 silencing enhanced doxorubicin-induced apoptosis by reducing P-glycoprotein in CXCR4⁺ LM8 cells, while CXCR4 overexpression promoted OS doxorubicin resistance in CXCR4⁻Dunn cells. Furthermore, CXCR4 silencing with or without doxorubicin increased the expression of beclin 1 and light chain 3B, and the number of autophagosomes and autolysosomes, as well as induced autophagic flux activation by suppressing the PI3K/AKT/mTOR signaling pathway. In addition, pretreatment with the autophagy inhibitor bafilomycin A1 attenuated CXCR4 abrogation-induced cell death. Finally, the CXCR4 antagonist AMD3100 synergistically reinforced the antitumor effect of doxorubicin in an orthotopic OS mouse model. Taken together, the present study revealed that CXCR4 inhibition sensitizes OS to doxorubicin by inducing autophagic cell death. Therefore, targeting the CXCR4/autophagy axis may be a promising therapeutic strategy to overcome OS chemotherapy resistance.

CXCL12-mediated HOXB5 overexpression facilitates Colorectal Cancer metastasis through transactivating CXCR4 and ITGB3

Background: Metastasis is the major reason for the high mortality of colorectal cancer (CRC). However, the molecular mechanism underlying CRC metastasis remains unclear. Here, we report a novel role of homeobox B5 (HOXB5), a member of the HOX family, in promoting CRC metastasis. Method: The expression of HOXB5 and its target genes were examined by immunohistochemistry in human CRC. Chromatin immunoprecipitation and luciferase reporter assays were performed to measure the transcriptional regulation of target genes by HOXB5. The metastatic capacities of CRC cells were evaluated by in vivo lung and liver metastatic models. Results: The elevated expression of HOXB5 was positively correlated with distant metastasis, higher AJCC stage, and poor prognosis in CRC patients. HOXB5 expression was an independent and significant risk factor for the recurrence and survival in CRC patients. Overexpression of HOXB5 promoted CRC metastasis by transactivating metastatic related genes, C-X-C motif chemokine receptor 4 (CXCR4) and integrin subunit beta 3 (ITGB3). C-X-C motif chemokine ligand 12 (CXCL12), which is the ligand of CXCR4, upregulated HOXB5 expression through the extracellular regulated protein kinase (ERK)/ETS proto-oncogene 1, transcription factor (ETS1) pathway. The knockdown of HOXB5 decreased CXCL12-enhanced CRC metastasis. Furthermore, AMD3100, a specific CXCR4 inhibitor, significantly suppressed HOXB5-mediated CRC metastasis. HOXB5 expression was positively correlated with CXCR4 and ITGB3 expression in human CRC tissues, and patients with positive co-expression of HOXB5/CXCR4, or HOXB5/ITGB3 exhibited the worst prognosis. Conclusion: Our study implicates HOXB5 as a prognostic biomarker in CRC, and defines a CXCL12-HOXB5-CXCR4 positive feedback loop that plays an important role in promoting CRC metastasis.

PTEN in osteosarcoma: Recent advances and the therapeutic potential

Osteosarcoma is the most common primary malignant bone tumor, predominantly occurring in children and adolescents. Despite treated with surgery and neoadjuvant chemotherapy, osteosarcoma has a high potential of local recurrence and lung metastasis. Overall survival rates for osteosarcoma have plateaued in the past four decades, therefore, identification of novel targets and development of more effective treatment strategies are urgent. Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene that negatively regulates the phosphatidylinositol 3-kinase (PI3K)/ protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) pathway. Over half of clinical osteosarcoma samples presented loss or low expression of PTEN, which usually indicated an advanced stage of tumor and a poor prognosis. The expression of PTEN is regulated by epigenetic silence, transcription regulation, post-translational modifications, and protein interactions in osteosarcoma. Therefore, explicating regulations to restore the anti-tumor function of PTEN might provide novel targeted therapies for osteosarcoma. Preclinical evidence suggested directly targeting the altered PTEN in osteosarcoma was promising. Current clinical application of PTEN related therapies in osteosarcoma are PI3K/mTOR inhibitors, and these drugs have shown the favorable efficacy in patients with advanced osteosarcoma.

NRP1 regulates radiation-induced EMT via TGF-β/Smad signaling in lung adenocarcinoma cells

PURPOSE

Radiation has been shown to promote the epithelial-mesenchymal transition (EMT) in tumor cells, and TGF-β/Smad and PI3K-Akt signaling pathways play an important role in the EMT. In this study, we investigated the effects of neuropilin-1 (NRP1) on radiation-induced TGF-β/Smad and non-classical Smad signaling pathways in lung cancer cells, as well as the effects of NRP1 on invasion and migration.

MATERIALS AND METHODS

Changes in the expression levels of EMT markers (β-catenin, N-cadherin, and vimentin) and related transcription factors (Twist and ZEB1) in stably transfected cells were detected by Western blotting and qPCR, and changes were assessed by TGF-β/Smad and non-classical Smad signaling. Immunofluorescence was used to detect the expression of the cytoskeletal protein F-actin. Expression of TGF-β1 and CXCL-12 was detected by ELISA. Transwell and scratch assays were used to detect the invasive ability and migration of lung cancer cells, respectively.

RESULTS

Our results showed that ionizing radiation could induce the EMT as well as morphological changes in lung adenocarcinoma cells (A549); however, the effects were not significant in lung squamous carcinoma cells (SK-MES-1). Moreover, we showed that NRP1 promotes the EMT induced by ionizing radiation in A549 cells, which may be related to the increased expression of EMT-related transcription factors. NRP1 may promote the radiation-induced EMT of A549 cells mainly through TGF-β1/Smad2/3 signaling. NRP1 also enhanced radiation-induced invasion, migration, and CXCL-12 expression in A549 cells.

CONCLUSIONS

We conclude that NRP1 promotes radiation-induced EMT in lung adenocarcinoma cells via TGF-β1/Smad signaling and not non-classical Smad signaling, and enhances the invasion and migration of lung adenocarcinoma cells.

JNK signaling is required for proper tangential migration and laminar allocation of cortical interneurons

The precise migration of cortical interneurons is essential for the formation and function of cortical circuits, and disruptions to this key developmental process are implicated in the etiology of complex neurodevelopmental disorders, including schizophrenia, autism and epilepsy. We have recently identified the Jun N-terminal kinase (JNK) pathway as an important mediator of cortical interneuron migration in mice, regulating the proper timing of interneuron arrival into the cortical rudiment. In the current study, we demonstrate a vital role for JNK signaling at later stages of corticogenesis, when interneurons transition from tangential to radial modes of migration. Pharmacological inhibition of JNK signaling in ex vivo slice cultures caused cortical interneurons to rapidly depart from migratory streams and prematurely enter the cortical plate. Similarly, genetic loss of JNK function led to precocious stream departure ex vivo, and stream disruption, morphological changes and abnormal allocation of cortical interneurons in vivo These data suggest that JNK signaling facilitates the tangential migration and laminar deposition of cortical interneurons, and further implicates the JNK pathway as an important regulator of cortical development.

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.

Circulating osteopontin per tumor volume as a prognostic biomarker for resectable intrahepatic cholangiocarcinoma

Background

The role of osteopontin (OPN) in intrahepatic cholangiocarcinoma (ICC) remains controversial. This study aimed to explore the prognostic value of OPN in patients with ICC undergoing curative resection.

Methods

Patients undergoing curative resection from 2005 to 2016 were identified for inclusion in this retrospective study. The expression level of OPN in tumors was measured in each of the 228 patients by immunohistochemistry. Circulating OPN in serum was tested in 124 patients by ELISA. Tumor volume was calculated according to preoperative imaging or operation record. Proliferation assay, wound healing assay, and invasion assay were performed to investigate the biological function.

Results

Low expression of OPN in tissue was associated with lymph node metastasis (P=0.009) and shorter overall survival (OS) (P=0.001). A low level of circulating OPN/volume was associated with multiple tumors (P<0.001), vascular invasion (P=0.027), visceral peritoneal perforation (P=0.001), and lymph node metastasis (P=0.002). It was also able to predict the invasive behavior, lymph node metastasis, and early recurrence with the area under the receiver operating curve (AUC) of being 0.719, 0.708 and 0.622 respectively. Patients with a low level of circulating OPN/volume had shorter OS (P=0.028) and disease-free survival (DFS) (P=0.004) and could benefit from adjuvant chemotherapy (P=0.011). Compared with negative controlled cells, ICC cell lines, which expressed more OPN, showed a decelerated proliferation rate, the weaker ability of migration and invasion, while the opposite was true for the cells expressed less OPN. MMP1, MMP10, and CXCR4 were negatively regulated by OPN.

Conclusions

A low level of circulating OPN/volume could indicate aggressive characteristics, along with poor prognosis and efficacy of adjuvant chemotherapy in ICC patients. Over expression of OPN may inhibit phenotypes facilitating ICC metastasis by negatively regulating MMP1, MMP10, and CXCR4.

Targeting autophagy is a promising therapeutic strategy to overcome chemoresistance and reduce metastasis in osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy, mainly affecting children and adolescents. Currently, surgical resection combined with adjuvant chemotherapy has been standardized for OS treatment. Despite great advances in chemotherapy for OS, its clinical prognosis remains far from satisfactory; this is due to chemoresistance, which has become a major obstacle to improving OS treatment. Autophagy, a catabolic process through which cells eliminate and recycle their own damaged proteins and organelles to provide energy, can be activated by chemotherapeutic drugs. Accumulating evidence has indicated that autophagy plays the dual role in the regulation of OS chemoresistance by either promoting drug resistance or increasing drug sensitivity. The aim of the present review was to demonstrate thatautophagy has both a cytoprotective and an autophagic cell death function in OS chemoresistance. In addition, methods to detect autophagy, autophagy inducers and inhibitors, as well as autophagy‑mediated metastasis, immunotherapy and clinical prognosis are also discussed.

PTEN loss activates a functional AKT/CXCR4 signaling axis to potentiate tumor growth and lung metastasis in human osteosarcoma cells

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents. Loss of the tumor suppressor PTEN or activation of chemokine receptor CXCR4 has been demonstrated to associate with OS respectively. However, the signaling mechanism underlying PTEN-mediated antitumor effect remains largely unknown, and the crosstalk between PTEN and CXCR4 in OS has not been investigated. Here, we uncover a PTEN/AKT/CXCR4 pathway nexus in highly tumorigenic and metastatic human 143B OS cells. Loss of PTEN activates AKT/CXCR4 signaling axis and regulates a series of tumor cell behaviors. Notably, ERK is inversely regulated by PTEN and its activation occurs downstream of AKT but upstream of CXCR4, suggesting this kinase to be an important mediator between AKT and CXCR4. In vivo studies show that overexpression of PTEN dramatically attenuates bone destruction, and this inhibition is associated with reduced CXCR4 expression in tumors. CXCR4 inhibitor AMD3100 also markedly suppresses tumor growth in the bone. In addition, PTEN overexpression or AMD3100 substantially inhibits tumor expansion in the lung. Our studies highlight a novel PTEN/AKT/CXCR4 signaling nexus in OS tumor growth and lung metastasis, and provide a strong rationale to consider PTEN restoration or CXCR4 blockade for the treatment of aggressive OS in humans.

SDF-1/CXCR4 axis facilitates myeloid-derived suppressor cells accumulation in osteosarcoma microenvironment and blunts the response to anti-PD-1 therapy

Immune checkpoint inhibitors, such as anti-PD-1/PD-L1, are a novel class of inhibitors that function as a tumor suppressing factor via modulation of immune cell-tumor cell interaction. To date, PD-1/PD-L1 inhibitors have been approved for the treatment of specific types of tumors and obtained good clinical efficacy. However, patients with osteosarcoma showed poor response to anti-PD-1/PD-L1 therapy, the mechanism of which is not well understood. In this study, we found that osteosarcoma tissues were heavily infiltrated by myeloid-derived suppressor cells (MDSCs) which could inhibit cytotoxicity T cell (CTL) expansion. Further study revealed that the vast majority of tumor-infiltrating MDSCs were CXCR4 positive and could migrate toward an SDF-1 gradient. The binding of SDF-1 to its receptor CXCR4 results in the activation of downstream AKT pathway that mediates reduced apoptosis of MDSCs. We also demonstrated that AMD3100, a CXCR4 antagonist, has a synergistic effect with anti-PD-1 antibody in tumor treatment in a murine model of osteosarcoma. These findings provide the basis for establishing CXCR4 antagonist and PD-1/PD-L1 inhibitors co-administration as a novel therapeutic regimen for patients with osteosarcoma and hold great promise for improving the therapeutic effect of osteosarcoma.

CXCR4 in human osteosarcoma malignant progression. The response of osteosarcoma cell lines to the fully human CXCR4 antibody MDX1338

Osteosarcoma (OS) is the most frequent primary malignant tumour of bone and metastases occur in 30% of cases, the 5-year survival rate is 25–30%.

Although pre- and post-operative chemotherapy has improved prognosis in osteosarcoma (OS), high toxicity and natural and acquired drug-resistance are the first cause of treatment failure. The identification of new predictive and therapeutic biomarkers may increase drug sensitivity and better control localized and metastatic disease. By the evidence that CXCR4 receptor by binding its ligand CXCL12 activates downstream critical endpoints for tumour malignancy, we first studied human OS progression correlating CXCR4 expression in OS biopsy with patient clinical data. By Real-time PCR and immunoistochemistry we found that high levels of CXCR4 gene and protein expression significantly correlated with OS progression, emphasizing the role of CXCR4/CXCL12 axis in tumour prognosis. This was supported by univariate analyses that showed a higher probability of local and/or systemic relapse in OS patients with a high CXCR4 gene expression and a significant increase of metastasis risk associated with an increasing score of CXCR4 protein staining intensity. Secondarily, to study the role of CXCR4 as a target for new therapeutic strategies, we evaluated the response of OS cells to the fully human CXCR4 antibody, MDX1338. In the study we also included AMD3100, the most studied CXCR4 antagonist.

In CXCR4-positive OS cells cultured in CXCL12-rich BM-MCS-CM (bone marrow-derived mesenchymal stem conditioned medium), a decrease of cell proliferation up to 30%–40% of control was seen after drug exposure. However, an increase of apoptosis was seen in p53-positive U2OS and 143B after CXCR4 inhibitor incubation, while no changes were seen in treated SAOS-2 cells which also present a different labeling profile. The role of p53 in apoptotic response to CXCR4 inhibitors was confirmed by p53 silencing in U2OS cell line. Our data suggest that the response to anti-CXCR4 agents could be influenced by the genetic background and labeling profile which induces a different cross-talk between tumour cells and environment. The delay in cell cycle progression associated with increased apoptosis could sensitize p53-positive cells to conventional therapy and in vivo preclinical experiments are on going with the aim to suggest new combined target therapies in human OS.

Dual blockade of CXCL12-CXCR4 and PD-1-PD-L1 pathways prolongs survival of ovarian tumor-bearing mice by prevention of immunosuppression in the tumor microenvironment

Blockade of immune-checkpoint programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 can enhance effector T-cell responses. However, the lack of response in many patients to checkpoint-inhibitor therapies emphasizes the need for combination immunotherapies to pursue maximal antitumor efficacy. We have previously demonstrated that antagonism of C-X-C chemokine receptor type 4 (CXCR4) by plerixafor (AMD3100) can decrease regulatory T (T_reg)-cell intratumoral infiltration. Therefore, a combination of these 2 therapies might increase antitumor effects. Here, we evaluated the antitumor efficacy of AMD3100 and anti-PD-1 (αPD-1) antibody alone or in combination in an immunocompetent syngeneic mouse model of ovarian cancer. We found that AMD3100, a highly specific CXCR4 antagonist, directly down-regulated the expression of both C-X-C motif chemokine 12 (CXCL12) and CXCR4 in vitro and in vivo in tumor cells. AMD3100 and αPD-1 significantly inhibited tumor growth and prolonged the survival of tumor-bearing mice when given as monotherapy. Combination of these 2 agents significantly enhanced antitumor effects compared with single-agent administration. Benefits of tumor control and animal survival were associated with immunomodulation mediated by these 2 agents, which were characterized by increased effector T-cell infiltration, increased effector T-cell function, and increased memory T cells in tumor microenvironment. Intratumoral T_reg cells were decreased, and conversion of T_reg cells into T helper cells was increased by AMD3100 treatment. Intratumoral myeloid-derived suppressor cells were decreased by the combined treatment, which was associated with decreased IL-10 and IL-6 in the ascites. Also, the combination therapy decreased suppressive leukocytes and facilitated M2-to-M1 macrophage polarization in the tumor. These results suggest that AMD3100 could be used to target the CXCR4-CXCL12 axis to inhibit tumor growth and prevent multifaceted immunosuppression alone or in combination with αPD-1 in ovarian cancer, which could be clinically relevant to patients with this disease.-Zeng, Y., Li, B., Liang, Y., Reeves, P. M., Qu, X., Ran, C., Liu, Q., Callahan, M. V., Sluder, A. E., Gelfand, J. A., Chen, H., Poznansky, M. C. Dual blockade of CXCL12-CXCR4 and PD-1-PD-L1 pathways prolongs survival of ovarian tumor-bearing mice by prevention of immunosuppression in the tumor microenvironment.

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.

Convective forces increase CXCR4-dependent glioblastoma cell invasion in GL261 murine model

Glioblastoma is the most common and malignant form of brain cancer. Its invasive nature limits treatment efficacy and promotes inevitable recurrence. Previous in vitro studies showed that interstitial fluid flow, a factor characteristically increased in cancer, increases glioma cell invasion through CXCR4-CXCL12 signaling. It is currently unknown if these effects translate in vivo. We used the therapeutic technique of convection enhanced delivery (CED) to test if convective flow alters glioma invasion in a syngeneic GL261 mouse model of glioblastoma. The GL261 cell line was flow responsive in vitro, dependent upon CXCR4 and CXCL12. Additionally, transplanting GL261 intracranially increased the populations of CXCR4+ and double positive cells versus 3D culture. We showed that inducing convective flow within implanted tumors indeed increased invasion over untreated controls, and administering the CXCR4 antagonist AMD3100 (5 mg/kg) effectively eliminated this response. These data confirm that glioma invasion is stimulated by convective flow in vivo and depends on CXCR4 signaling. We also showed that expression of CXCR4 and CXCL12 is increased in patients having received standard therapy, when CED might be elected. Hence, targeting flow-stimulated invasion may prove beneficial as a second line of therapy, particularly in patients chosen to receive treatment by convection enhanced delivery.

Clampdown of inflammation in aging and anticancer therapies by limiting upregulation and activation of GPCR, CXCR4

One of the major pathological outcomes of DNA damage during aging or anticancer therapy is enhanced inflammation. However, the underlying signaling mechanism that drives this is not well understood. Here, we show that in response to DNA damage, ubiquitously expressed GPCR, CXCR4 is upregulated through the ATM kinase-HIF1α dependent DNA damage response (DDR) signaling, and enhances inflammatory response when activated by its ligand, chemokine CXCL12. A pharmacologically active compound screen revealed that this increased inflammation is dependent on reduction in cAMP levels achieved through activation of Gαi through CXCR4 receptor and PDE4A. Through in vivo analysis in mice where DNA damage was induced by irradiation, we validated that CXCR4 is induced systemically after DNA damage and inhibition of its activity or its induction blocked inflammation as well as tissue injury. We thus report a unique DNA damage-linked inflammatory cascade, which is mediated by expression level changes in a GPCR and can be targeted to counteract inflammation during anticancer therapies as well as aging.

A sensing protein that is increased in response to DNA damage can be targeted to reduce inflammation and collateral damage during anti-cancer therapy and aging. Scientists at Saini Lab at the Indian Institute of Science have identified the protein that drives sustained and detrimental inflammation when the DNA of cells are damaged, such as during normal human aging or during anti-cancer therapy. Furthermore, blocking the functions of this protein and associated pathway was able to reduce the inflammation to less harmful levels. This discovery could potentially enable safer and more effective anti-cancer therapy by protecting non-cancerous cells surrounding tumors from lethal inflammation. Further studies on this protein could also reduce age associated inflammation, allowing us to age gracefully and healthily.

CoCl2 , a mimic of hypoxia, enhances bone marrow mesenchymal stem cells migration and osteogenic differentiation via STAT3 signaling pathway

Mesenchymal stem cells homing and migration is a crucial step during bone fracture healing. Hypoxic environment in fracture site induces bone marrow mesenchymal stem cells (BMSCs) migration, but its mechanism remains unclear. Our previous study and studies by other groups have reported the involvement of signal transducer and activator of transcription 3 (STAT3) pathway in cell migration. However, the role of STAT3 pathway in hypoxia-induced cell migration is still unknown. In this study, we investigated the role of STAT3 signaling in hypoxia-induced BMSCs migration and osteogenic differentiation. BMSCs isolated from C57BL/6 male mice were cultured in the presence of cobalt chloride (CoCl₂ ) to simulate intracellular hypoxia. Hypoxia enhanced BMSCs migration, and upregulated cell migration related gene expression, that is, metalloproteinase (MMP) 7, MMP9, and C-X-C motif chemokine receptor 4. Hypoxia enhanced the phosphorylation of STAT3, and cell migration related proteins: c-jun n-terminal kinase (JNK), focal of adhesion kinase (FAK), extracellular regulated protein kinases, and protein kinase B 1/2 (ERK1/2). Moreover, hypoxia enhanced expression of osteogenic differentiation marker. Inhibition of STAT3 suppressed the hypoxia-induced BMSCs migration, cell migration related signaling molecules phosphorylation, and osteogenic differentiation related gene expression. In conclusion, our result indicates that hypoxia-induced BMSCs migration and osteogenic differentiation is via STAT3 phosphorylation and involves the cooperative activity of the JNK, FAK, and MMP9 signaling pathways.

CXCR4-mediated osteosarcoma growth and pulmonary metastasis is suppressed by MicroRNA-613

Osteosarcoma is the most common primary bone malignancy. Recently, studies showed chemokine receptor 4 (CXCR4) played a critical role in osteosarcoma. However, the regulation of CXCR4 is not fully understood. microRNAs are short, non‐coding RNAs that play an important roles in post‐transcriptional regulation of gene expression in a variety of diseases including osteosarcoma. miR‐613 is a newly discovered miRNA and has been reported to function as a tumor suppressor in many cancers. In this study, we confirmed that both Stromal Cell‐Derived Factor (SDF‐1) and CXCR4 could be prognostic markers for osteosarcoma. Meanwhile this study found that SDF‐1/CXCR4 pathway regulated osteosarcoma cells proliferation, migration and reduced apoptosis. Besides, we demonstrated that miR‐613 was significantly downregulated in osteosarcoma patients. Elevated expression of miR‐613 directly suppressed CXCR4 expression and then decreased the proliferation, migration and induced apoptosis of osteosarcoma cells. Moreover, our study found that CXCR4 promoted the development of lung metastases and inhibition of CXCR4 by miR‐613 reduced lung metastases. These data indicated that CXCR4 mediated osteosarcoma cell growth and lung metastases and this effect can be suppressed by miR‐613 through directly downregulating CXCR4.

Bioinformatic analyses reveal the key pathways and genes in the CXCR4 mediated mesenchymal subtype of glioblastoma

Glioblastoma multiforme (GBM) is one of the most lethal types of tumour, despite severe treatment methods. The Cancer Genome Atlas has categorised GBMs into proneural, neural, classical and mesenchymal subtypes; the mesenchymal subgroup has the worst prognosis. CXCR4 has been reported as selectively overexpressed in the mesenchymal subtype and positively associated with MES markers. However, to the best of our knowledge the underlying mechanisms regarding how CXCR4 may regulate mesenchymal GBM are still unknown. The present study aimed to investigate the critical pathways mediated by CXCR4 in mesenchymal GBM using bioinformatic analyses. The results suggested that CXCR4 is a predictor of poor prognosis and may serve as a biomarker of the mesenchymal subtype in patients with GBM. In addition, CXCR4 mediated the mitogen‑activated protein kinase signaling pathway, which was identified specifically in patients with mesenchymal GBM. CXCR4 associated genes or pathways may be a 'basket trial' option for the management of melanoma, prostate cancer and mesenchymal GBM.

MEKK1, JNK, and SMAD3 mediate CXCL12-stimulated connective tissue growth factor expression in human lung fibroblasts

Background

In idiopathic pulmonary fibrosis, the interaction of CXCL12 and CXC receptor 4 (CXCR4) plays a critical role in lung fibrosis. Connective tissue growth factor (CTGF) overexpression underlies the development of pulmonary fibrosis. Our previous report showed that the Rac1-dependent extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and activator protein (AP)-1 pathways are involved in CXCL12-generated CTGF expression in human lung fibroblasts (WI-38). In present study, we additionally inspected the involvement of mitogen-activated protein kinase kinase kinase 1 (MEKK1)/JNK-dependent SMAD3 in CXCL12-triggered CTGF expression in WI-38 cells.

Methods

WI-38 cells were stimulated with CXCL12 in the absence or presence of specific inhibitors or small interfering RNAs (siRNAs). CTGF expression and signaling transduction molecules were assessed by Western blot, luciferase activity assay, or ChIP assay.

Results

CXCL-12-induced CTGF expression was attenuated by SIS3 (a SMAD3 inhibitor) and SMAD3 siRNA, but not by SB431542 (an activin receptor-like kinase 5, ALK5, inhibitor). CXCL12-stimulated CTGF expression was also attenuated by MEKK1 siRNA. Treatment of cells with CXCL12 caused an increase in SMAD3 phosphorylation at Ser208, translocation to nuclei, SMAD3-luciferase activity, and recruitment of SMAD3 to the CTGF promoter. Stimulation of cells with CXCL12 resulted in increase in JNK phosphorylation at Thr183/Tyr185 and MEKK1 phosphorylation at Thr261. Moreover, CXCL12-mediated SMAD3 phosphorylation or SMAD3-luciferase activity was inhibited by MEKK1 siRNA or SP600125. Finally, CXCL12-mediated JNK phosphorylation was attenuated by MEKK1 siRNA.

Conclusion

In conclusion, results of this study suggest that CXCL12 activates the MEKK1/JNK signaling pathway, which in turn initiates SMAD3 phosphorylation, its translocation to nuclei, and recruitment of SMAD3 to the CTGF promoter, which ultimately induces CTGF expression in human lung fibroblasts.

Established Models and New Paradigms for Hypoxia-Driven Cancer-Associated Bone Disease

The five-year survival rate for primary bone cancers is ~ 70% while almost all cases of secondary metastatic bone cancer are terminal. Hypoxia, the deficiency of oxygen which occurs as the rate of tumour growth exceeds the supply of vascularisation, is a key promoter of tumour progression. Hypoxia-driven effects in the primary tumour are wide ranging including changes in gene expression, dysregulation of signalling pathways, resistance to chemotherapy, neovascularisation, increased tumour cell proliferation and migration. Paget's seed and soil theory states that for a metastasising tumour cell 'the seed' it requires the correct microenvironment 'soil' to colonise. Why and how metastasising tumour cells colonise the bone is a complex and intriguing problem. However, once present tumour cells are able to disrupt bone homeostasis through increasing osteoclast activity and downregulating osteoblast function. Osteoclast resorption releases growth factors from the bone matrix that subsequently contribute to the proliferation of invasive tumour cells creating the vicious cycle of bone loss and metastatic cancer progression. Recently, we have shown that hypoxia increases expression and release of lysyl oxidase (LOX) from primary mammary tumours, which in turn disrupts bone homeostasis to favour osteolytic degradation to create pre-metastatic niches in the bone microenvironment. We also demonstrated how treatment with bisphosphonates could block this cancer-induced bone remodelling and reduce secondary bone metastases. This review describes the roles of hypoxia in primary tumour progression to metastasis, with a focus on key signalling pathways and treatment options to reduce patient morbidity and increase survival.

The CXCL12/CXCR7 signaling axis, isoforms, circadian rhythms, and tumor cellular composition dictate gradients in tissue

Chemokine CXCL12 gradients drive chemotaxis in a CXCR4-dependent mechanism and have been implicated in cancer metastasis. While CXCL12 gradients are typically studied in organized, defined environments, the tumor microenvironment is disorganized. In vivo, CXCL12 gradients depend on many factors: the number and arrangement of cells secreting and degrading CXCL12, isoform-dependent binding to the extracellular matrix, diffusion, and circadian fluctuations. We developed a computational model of the tumor microenvironment to simulate CXCL12 gradient dynamics in disorganized tissue. There are four major findings from the model. First, CXCL12-β and -γ form higher magnitude (steeper) gradients compared to CXCL12-α. Second, endothelial CXCR7+ cells regulate CXCL12 gradient direction by controlling concentrations near but not far from the vasculature. Third, the magnitude and direction of CXCL12 gradients are dependent on the local composition of secreting and scavenging cells within the tumor. We theorize that "micro-regions" of cellular heterogeneity within the tumor are responsible for forming strong gradients directed into the blood. Fourth, CXCL12 circadian fluctuations influence gradient magnitude but not direction. Our simulations provide predictions for future experiments in animal models. Understanding the generation of CXCL12 gradients is crucial to inhibiting cancer metastasis.

Targeting the CXCR4/CXCL12 axis in treating epithelial ovarian cancer

Ovarian carcinoma is the most crucial and difficult target for available therapeutic treatments among gynecological malignancies, and great efforts are required to find an effective solution. Molecular studies showed that the chemokine stromal cell-derived factor-1 (also known as CXCL12) and its receptor, CXCR4, are key determinants of tumor initiation, progression and metastasis in ovarian carcinomas. Hence, it is generally believed that blocking the CXCR4/CXCL12 pathway could serve as a potential therapy for patients with ovarian cancer. Herein, we investigated the role of the CXCR4/CXCL12 axis in regulating ovarian cancer progression. Using flow cytometry, a real-time PCR and western blot analyses, we showed that the chemokine receptor CXCR4 protein and mRNA were overexpressed in human epithelial ovarian cancer cell lines, and these were closely correlated with poor outcomes. Moreover, silencing CXCR4 by small hairpin RNA in HTB75 cells reduced cell proliferation, migration and invasion and significantly reduced RhoA and Rac-1/Cdc42 expressions, whereas overexpression of CXCR4 in SKOV3 cells significantly increased cell migration and markedly increased RhoA, Rac-1/Cdc42 levels. Silencing CXCR4 also led to decreased in vitro cytotoxicity of AMD3100, a specific antagonist of CXCR4, which exerts its effect upon CXCR4 expression. Remarkably, knockdown of CXCR4 in HTB75 cells led to a significantly decreased capability to form tumors in vivo, and the Ki67 proliferation index of xenograft tumors showed a dramatic reduction. Our results revealed that the CXCR4/CXCL12 pathway represents a promising therapeutic target for epithelial ovarian carcinoma.

Mesenchymal stromal cells' role in tumor microenvironment: involvement of signaling pathways

Mesenchymal stromal cells (MSCs) are adult multipotent stem cells residing as pericytes in various tissues and organs where they can differentiate into specialized cells to replace dying cells and damaged tissues. These cells are commonly found at injury sites and in tumors that are known to behave like " wounds that do not heal." In this article, we discuss the mechanisms of MSCs in migrating, homing, and repairing injured tissues. We also review a number of reports showing that tumor microenvironment triggers plasticity mechanisms in MSCs to induce malignant neoplastic tissue formation, maintenance, and chemoresistance, as well as tumor growth. The antitumor properties and therapeutic potential of MSCs are also discussed.

Development of CXCR4 modulators by virtual HTS of a novel amide-sulfamide compound library

CXCR4 plays a crucial role in recruitment of inflammatory cells to inflammation sites at the beginning of the disease process. Modulating CXCR4 functions presents a new avenue for anti-inflammatory strategies. However, using CXCR4 antagonists for a long term usage presents potential serious side effect due to their stem cell mobilizing property. We have been developing partial CXCR4 antagonists without such property. A new computer-aided drug design program, the FRESH workflow, was used for anti-CXCR4 lead compound discovery and optimization, which coupled both compound library building and CXCR4 docking screens in one campaign. Based on the designed parent framework, 30 prioritized amide-sulfamide structures were obtained after systemic filtering and docking screening. Twelve compounds were prepared from the top-30 list. Most synthesized compounds exhibited good to excellent binding affinity to CXCR4. Compounds Ig and Im demonstrated notable in vivo suppressive activity against xylene-induced mouse ear inflammation (with 56% and 54% inhibition). Western blot analyses revealed that Ig significantly blocked CXCR4/CXCL12-mediated phosphorylation of Akt. Moreover, Ig attenuated the amount of TNF-α secreted by pathogenic E. coli-infected macrophages. More importantly, Ig had no observable cytotoxicity. Our results demonstrated that FRESH virtual high throughput screening program of targeted chemical class could successfully find potent lead compounds, and the amide-sulfamide pharmacophore was a novel and effective framework blocking CXCR4 function.

CXCR4 and CCR7: Two eligible targets in targeted cancer therapy

Cancer is one of the most common cause of death in the world with high negative emotional, economic, and social impacts. Conventional therapeutic methods, including chemotherapy and radiotherapy, have not proven satisfactory and relapse is common in most cases. Recent studies have focused on targeted therapy with more precise identification and targeted attacks to the cancer cells. For this purpose, chemokine receptors are proper targets and among them, CXCR4 and CCR7, with a crucial role in cancer metastasis, are being considered as desired candidates for investigation. In this review paper, the most important experimental results are highlighted on the potential targeted therapies based on CXCR4 and CCR7 chemokine receptors.

CXCL12 expression promotes esophageal squamous cell carcinoma proliferation and worsens the prognosis

BACKGROUND

The chemokine CXCL12 and its corresponding receptor CXCR4 are key players in the development of several cancers. Therefore, we hypothesized that there is a functional causality between CXCL12 expression and tumor progression in patients with esophageal squamous cell carcinoma (ESCC).

METHODS

We performed an immunohistochemical analysis in 79 consecutive patients with ESCC. We performed in vitro and in vivo cell proliferation assays using ESCC cell lines and a newly established transfectant stably overexpressing CXCL12.

RESULTS

Immunohistochemistry revealed positive CXCR4 and CXCL12 expression in 48 (61 %) and 62 (78 %) patients, respectively. Additionally, the expression levels did not significantly correlate with any clinicopathological factors. The MIB-1 proliferation index was markedly higher in ESCC with a positive expression of CXCR4 or CXCL12. Positive CXCL12 expression was significantly correlated with lower recurrence-free survival (RFS, p = 0.02). Cox's hazard models revealed CXCL12 expression as an independent predictive factor for recurrence. In vitro, CXCL12 exposure or overexpression enhanced ESCC proliferation; and AMD3100, a specific inhibitor of CXCR4, equally decreased proliferation irrespective of CXCL12 exposure or overexpression. In the mouse model, AMD3100 significantly decreased ESCC tumor size (p = 0.03).

CONCLUSIONS

CXCL12 stimulates ESCC proliferation, and its expression levels are related to lower RFS in patients with ESCC. Our findings indicate that positive CXCL12 expression may be a useful marker for predicting the outcome in patients with ESCC and is a potentially new therapeutic target for ESCC.

Symmetrical bis-tertiary amines as novel CXCR4 inhibitors

CXCR4 inhibitors are promising agents for the treatment of cancer metastasis and inflammation. A series of novel tertiary amine derivatives targeting CXCR4 were designed, synthesized, and evaluated. The central benzene ring linker and side chains were modified and optimized to study the structure-activity relationship. Seven compounds displayed much more potent activity than the reference drug, AMD3100, in both the binding affinity assay and the blocking of Matrigel invasion functional assay. These compounds exhibited effective concentration ranging from 1 to 100 nM in the binding affinity assay and inhibited invasion from 65.3% to 100% compared to AMD3100 at 100 nM. Compound IIn showed a 50% suppressive effect against carrageenan-induced paw inflammation in a mouse model, which was as effective as the peptidic antagonist, TN14003 (48%). These data demonstrate that symmetrical bis-tertiary amines are unique CXCR4 inhibitors with high potency.

Role of stromal cell-derived factor 1α pathway in bone metastatic prostate cancer

Metastatic prostate cancer is one of the leading causes of cancer-related death in men. The primary site of metastasis from prostate cancers is the bone. During the last decade, multiple studies have pointed to the role of the stromal cell-derived factor 1 alpha (SDF1α)/CXCR4 axis in the metastatic spread of the disease, but the mechanisms that underlie this effect are still incompletely understood. In this review, we summarize the current understanding of the role of the SDF1α/CXCR4 pathway in bone metastatic prostate cancer. We also discuss the therapeutic potential of disrupting the interaction between prostate tumor cells and bone environment with focus on the SDF1α pathway.