Vesnarinone downregulates CXCR4 expression via upregulation of Krüppel-like factor 2 in oral cancer cells

Targeting anticancer immunity in oral cancer: Drugs, products, and nanoparticles

Oral cavity carcinomas are the most frequent malignancies among head and neck malignancies. Oral tumors include not only oral cancer cells with different potency and stemness but also consist of diverse cells, containing anticancer immune cells, stromal and also immunosuppressive cells that influence the immune system reactions. The infiltrated T and natural killer (NK) cells are the substantial tumor-suppressive immune compartments in the tumor. The infiltration of these cells has substantial impacts on the response of tumors to immunotherapy, chemotherapy, and radiotherapy. Nevertheless, cancer cells, stromal cells, and some other compartments like regulatory T cells (Tregs), macrophages, and myeloid-derived suppressor cells (MDSCs) can repress the immune responses against malignant cells. Boosting anticancer immunity by inducing the immune system or repressing the tumor-promoting cells is one of the intriguing approaches for the eradication of malignant cells such as oral cancers. This review aims to concentrate on the secretions and interactions in the oral tumor immune microenvironment. We review targeting tumor stroma, immune system and immunosuppressive interactions in oral tumors. This review will also focus on therapeutic targets and therapeutic agents such as nanoparticles and products with anti-tumor potency that can boost anticancer immunity in oral tumors. We also explain possible future perspectives including delivery of various cells, natural products and drugs by nanoparticles for boosting anticancer immunity in oral tumors.

Simvastatin inhibits proliferation and promotes apoptosis of oral squamous cell carcinoma through KLF2 signal

OBJECTIVES

This study aimed to explore the role and specific mechanism of the cholesterol-lowering drug simvastatin in inhibiting oral squamous cell carcinoma (OSCC).

METHODS

The proliferation, apoptosis, and migration levels of OSCC cells were detected by CCK8, quantitative real-time polymerase chain reaction, Western blot, colony formation, TdT-mediated dUTP Nick-End Labeling assay, and wound healing assay. The inhibitory effect of simvastatin in vivo was detected by a mouse xenograft tumor model. Immunohistochemistry and immunofluorescence staining were used to assess the KLF2 and β-catenin expressions in cells and tissues.

RESULTS

KLF2 expression in OSCC cells and tissues was downregulated. The addition of KLF2 inducer, GGTI298, inhibited the proliferation and migration of OSCC cells. Simvastatin played a role in inhibiting the proliferation and promoting the apoptosis of OSCC cells. Moreover, it inhibited β-catenin expression and promoted KLF2 expression in OSCC cells. KLF2 siRNA reversed the effect of simvastatin on the proliferation and apoptosis of OSCC cells.

CONCLUSIONS

KLF2, as a tumor suppressor gene, may be an important marker for diagnosing and treating OSCC. Simvastatin inhibits the progression of OSCC by regulating the KLF2 signal.

Versatile applications of transition metal incorporating quinoline Schiff base metal complexes: An overview

Since the last decade, research on quinoline Schiff base metal complexes has risen substantially due to their versatile applications across many significant fields. Schiff bases are also known as azomethines, aldimines, and imines. Quinoline Schiff base-derived metal complexes are intriguing to study topics. These complexes are employed in biological, analytical, and catalytic fields. Researchers have found that Schiff bases are more biologically active when coordinated with metal ions. Research in the biological sciences has shown that heterocyclic compounds like quinoline and its derivatives are important. Because of their broad spectrum of activity, quinoline derivatives have been discovered to be effective therapeutic agents for various disorders. Even though various classical synthetic pathways mentioned in the literature are still in use, there is an urgent need for a new, more effective method that is safer for the environment, has a higher yield, generates less hazardous waste, and is easier to use. This highlights the critical need for a safe, eco-friendly approach to quinoline scaffold synthesis. This review focuses exclusively on Schiff base metal complexes derived from quinoline, fabricated and studied in the past ten years, and having anticancer, antibacterial, antifungal, antioxidant, antidiabetic, antiproliferative, DNA-intercalation, and cytotoxic activities.

MiR-32-5p promoted epithelial-to-mesenchymal transition of oral squamous cell carcinoma cells via regulating the KLF2/CXCR4 pathway

Oral squamous cell carcinoma (OSCC) is one of the most common carcinomas of the oral cavity. However, the regulatory mechanisms on miR-32-5p remain poorly understood in OSCC. The expression of miR-32-5p, Krüppel-like factor 2 (KLF2), C-X-C motif chemokine receptor 4 (CXCR4), and epithelial-to-mesenchymal transition (EMT)-related proteins (E-cadherin, Vimentin, N-cadherin, and Snail) were evaluated were assessed using RT-qPCR and Western blot. 3-(4, 5-Dimethylthiazolyl2)-2, 5-diphenyltetrazolium bromide assay, wound healing assay, and transwell assay were employed to detect cell proliferation, migration, and invasion of OSCC cells. Finally, dual-luciferase reporter assay was performed to verify the binding relationship between KLF2 and miR-32-5p. MiR-32-5p was highly expressed while KLF2 was lowly expressed in OSCC cells, and miR-32-5p knockdown or KLF2 overexpression could markedly reduce cell proliferation, migration, invasion, and EMT of OSCC cells. What is more, KLF2 was the target of miR-32-5p, and knockdown of KLF2 abolished the inhibitory effect of miR-32-5p inhibitor on progression of OSCC. Finally, CXCR4 expression was negatively regulated by KLF2, and inhibition of CXCR4 obviously alleviated the biological effects of si-KLF2 on the progression of OSCC. MiR-32-5p could enhance cell proliferation, migration, invasion, and EMT of OSCC cells, and the discovery of miR-32-5p/KLF2/CXCR4 axis might provide potential therapeutic targets for OSCC.

CXCL12 Signaling in the Tumor Microenvironment

Tumor microenvironment (TME) is the local environment of tumor, composed of tumor cells and blood vessels, extracellular matrix (ECM), immune cells, and metabolic and signaling molecules. Chemokines and their receptors play a fundamental role in the crosstalk between tumor cells and TME, regulating tumor-related angiogenesis, specific leukocyte infiltration, and activation of the immune response and directly influencing tumor cell growth, invasion, and cancer progression. The chemokine CXCL12 is a homeostatic chemokine that regulates physiological and pathological process such as inflammation, cell proliferation, and specific migration. CXCL12 activates CXCR4 and CXCR7 chemokine receptors, and the entire axis has been shown to be dysregulated in more than 20 different tumors. CXCL12 binding to CXCR4 triggers multiple signal transduction pathways that regulate intracellular calcium flux, chemotaxis, transcription, and cell survival. CXCR7 binds with high-affinity CXCL12 and with lower-affinity CXCL11, which binds also CXCR3. Although CXCR7 acts as a CXCL12 scavenger through ligand internalization and degradation, it transduces the signal mainly through β-arrestin with a pivotal role in endothelial and neural cells. Recent studies demonstrate that TME rich in CXCL12 leads to resistance to immune checkpoint inhibitors (ICI) therapy and that CXCL12 axis inhibitors sensitize resistant tumors to ICI effect. Thus targeting the CXCL12-mediated axis may control tumor and tumor microenvironment exerting an antitumor dual action. Herein CXCL12 physiology, role in cancer biology and in composite TME, prognostic role, and the relative inhibitors are addressed.

The pharmaceutical solvent N-methyl-2-pyrollidone (NMP) attenuates inflammation through Krüppel-like factor 2 activation to reduce atherogenesis

N-methyl-2-pyrrolidone (NMP) is a versatile water-miscible polar aprotic solvent. It is used as a drug solubilizer and penetration enhancer in human and animal, yet its bioactivity properties remain elusive. Here, we report that NMP is a bioactive anti-inflammatory compound well tolerated in vivo, that shows efficacy in reducing disease in a mouse model of atherosclerosis. Mechanistically, NMP increases the expression of the transcription factor Kruppel-like factor 2 (KLF2). Monocytes and endothelial cells treated with NMP express increased levels of KLF2, produce less pro-inflammatory cytokines and adhesion molecules. We found that NMP attenuates monocyte adhesion to endothelial cells inflamed with tumor necrosis factor alpha (TNF-α) by reducing expression of adhesion molecules. We further show using KLF2 shRNA that the inhibitory effect of NMP on endothelial inflammation and subsequent monocyte adhesion is KLF2 dependent. Enhancing KLF2 expression and activity improves endothelial function, controls multiple genes critical for inflammation, and prevents atherosclerosis. Our findings demonstrate a consistent effect of NMP upon KLF2 activation and inflammation, biological processes central to atherogenesis. Our data suggest that inclusion of bioactive solvent NMP in pharmaceutical compositions to treat inflammatory disorders might be beneficial and safe, in particular to treat diseases of the vascular system, such as atherosclerosis.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

Targeting CXCL12/CXCR4 Axis in Tumor Immunotherapy

Chemokines, which have chemotactic abilities, are comprised of a family of small cytokines with 8-10 kilodaltons. Chemokines work in immune cells by trafficking and regulating cell proliferation, migration, activation, differentiation, and homing. CXCR-4 is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1, also known as CXCL12), which has been found to be expressed in more than 23 different types of cancers. Recently, the SDF-1/CXCR-4 signaling pathway has emerged as a potential therapeutic target for human tumor because of its critical role in tumor initiation and progression by activating multiple signaling pathways, such as ERK1/2, ras, p38 MAPK, PLC/ MAPK, and SAPK/ JNK, as well as regulating cancer stem cells. CXCL12/CXCR4 antagonists have been produced, which have shown encouraging results in anti-cancer activity. Here, we provide a brief overview of the CXCL12/CXCR4 axis as a molecular target for cancer treatment. We also review the potential utility of targeting CXCL12/CXCR4 axis in combination of immunotherapy and/or chemotherapy based on up-to-date literature and ongoing research progress.

KLF2 inhibits cell growth via regulating HIF-1α/Notch-1 signal pathway in human colorectal cancer HCT116 cells

The transcription factor Krüppel-like factor 2 (KLF2) has been shown to function as a tumor suppressor and regulate biological processes of cancer cells, such as cell growth, cell apoptosis and angiogenesis. However, the function and mechanism of KLF2 in colorectal cancer (CRC) is still unknown. In the present study, we show that the expression of KLF2 is diminished in a cohort of CRC cell lines. Also, KLF2 overexpression remarkably inhibits HCT116 and SW480 cell survival and proliferation. Moreover, cell death detection ELISA plus assay showed that KLF2 overexpression increased HCT116 cell proliferation. Caspase-3/7 activity also increased in HCT116 cells transfected with PcDNA3.1-KLF2. Further studies showed that KLF2 significantly suppresses the expression of Notch-1 and is dependent on the decline of the HIF-1α level. Most importantly, silencing Notch-1 expression or HIF-1α level both impair the action of KLF2 overexpression in CRC cells. Collectively, we demonstrated that KLF2 mediates CRC cell biological processes including cell growth and apoptosis via regulating the HIF-1α/Notch-1 signal pathway. These results indicated that KLF2 plays an important role in CRC and provided novel insight on the function of KLF2 in tumor progression.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Chemokines accentuating protumoral activities in oral cancer microenvironment possess an imperious stratagem for therapeutic resolutions

Chemokines, the chemotactic cytokines have established their role in tumorigenesis and tumor progression. Studies, which explored their role in oral cancer for protumoral activity, point towards targeting chemokines for oral squamous cell carcinoma therapy. The need of the hour is to emphasize/divulge in the activities of chemokine ligands and their receptors in the tumor microenvironment for augmentation of such stratagems. This progressing sentience of chemokines and their receptors has inspired this review which is an endeavour to comprehend their role as an aid in accentuating hallmarks of cancer and targeted therapy.

Oncogenic roles and drug target of CXCR4/CXCL12 axis in lung cancer and cancer stem cell

Although the great progress has been made in diagnosis and therapeutic in lung cancer, it induces the most cancer death worldwide in both males and females. Chemokines, which have chemotactic abilities, contain up to 50 family members. By binding to G protein-coupled receptors (GPCR), holding seven-transmembrane domain, they function in immune cell trafficking and regulation of cell proliferation, differentiation, activation, and migration, homing under both physiologic and pathologic conditions. The alpha-chemokine receptor CXCR4 for the alpha-chemokine stromal cell-derived-factor-1 (SDF-1) is most widely expressed by tumors. In addition to human tissues of the bone marrow, liver, adrenal glands, and brain, the CXC chemokine SDF-1 or CXCL12 is also highly expressed in lung cancer tissues and is associated with lung metastasis. Lung cancer cells have the capabilities to utilize and manipulate the CXCL12/CXCR system to benefit growth and distant spread. CXCL12/CXCR4 axis is a major culprit for lung cancer and has a crucial role in lung cancer initiation and progression by activating cancer stem cell. This review provides an evaluation of CXCL12/CXCR4 as the potential therapeutic target for lung cancers; it also focuses on the synergistic effects of inhibition of CXCL12/CXCR4 axis and immunotherapy as well as chemotherapy. Together, CXCL12/CXCR4 axis can be a potential therapeutic target for lung cancers and has additive effects with immunotherapy.

CXCR4 in breast cancer: oncogenic role and therapeutic targeting

Chemokines are 8–12 kDa peptides that function as chemoattractant cytokines and are involved in cell activation, differentiation, and trafficking. Chemokines bind to specific G-protein-coupled seven-span transmembrane receptors. Chemokines play a fundamental role in the regulation of a variety of cellular, physiological, and developmental processes. Their aberrant expression can lead to a variety of human diseases including cancer. C-X-C chemokine receptor type 4 (CXCR4), also known as fusin or CD184, is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1 also called CXCL12). CXCR4 belongs to the superfamily of the seven transmembrane domain heterotrimeric G protein-coupled receptors and is functionally expressed on the cell surface of various types of cancer cells. CXCR4 also plays a role in the cell proliferation and migration of these cells. Recently, CXCR4 has been reported to play an important role in cell survival, proliferation, migration, as well as metastasis of several cancers including breast cancer. This review is mainly focused on the current knowledge of the oncogenic role and potential drugs that target CXCR4 in breast cancer. Additionally, CXCR4 proangiogenic molecular mechanisms will be reviewed. Strict biunivocal binding affinity and activation of CXCR4/CXCL12 complex make CXCR4 a unique molecular target for prevention and treatment of breast cancer.

Specific chemotherapeutic agents induce metastatic behaviour through stromal- and tumour-derived cytokine and angiogenic factor signalling

Recent studies reveal that chemotherapy can enhance metastasis due to host responses, such as augmented expression of adhesion molecules in endothelial cells and increased populations of myeloid cells. However, it is still unclear how tumour cells contribute to this process. Here, we observed that paclitaxel and carboplatin accelerated lung metastasis in tumour-bearing mice, while doxorubicin and fluorouracil did not. Mechanistically, paclitaxel and carboplatin induced similar changes in cytokine and angiogenic factors. Increased levels of CXCR2, CXCR4, S1P/S1PR1, PlGF and PDGF-BB were identified in the serum or primary tumour tissues of tumour-bearing mice treated by paclitaxel. The serum levels of CXCL1 and PDGF-BB and the tissue level of CXCR4 were also elevated by carboplatin. On the other hand, doxorubicin and fluorouracil did not induce such changes. The chemotherapy-induced cytokine and angiogenic factor changes were also confirmed in gene expression datasets from human patients following chemotherapy treatment. These chemotherapy-enhanced cytokines and angiogenic factors further induced angiogenesis, destabilized vascular integrity, recruited BMDCs to metastatic organs and mediated the proliferation, migration and epithelial-to-mesenchymal transition of tumour cells. Interestingly, inhibitors of these factors counteracted chemotherapy-enhanced metastasis in both tumour-bearing mice and normal mice injected intravenously with B16F10-GFP cells. In particular, blockade of the SDF-1α-CXCR4 or S1P-S1PR1 axes not only compromised chemotherapy-induced metastasis but also prolonged the median survival time by 33.9% and 40.3%, respectively. The current study delineates the mechanism of chemotherapy-induced metastasis and provides novel therapeutic strategies to counterbalance pro-metastatic effects of chemo-drugs via combination treatment with anti-cytokine/anti-angiogenic therapy.

CXCR4 is a novel target of cancer chemopreventative isothiocyanates in prostate cancer cells

Isothiocyanates (ITCs) derived from cruciferous vegetables, including phenethyl isothiocyanate (PEITC) and sulforaphane (SFN), exhibit in vivo activity against prostate cancer in a xenograft and transgenic mouse model, and thus are appealing for chemoprevention of this disease. Watercress constituent PEITC and SFN-rich broccoli sprout extract are under clinical investigations but the molecular mechanisms underlying their cancer chemopreventive effects are not fully understood. The present study demonstrates that chemokine receptor CXCR4 is a novel target of ITCs in prostate cancer cells. Exposure of prostate cancer cells (LNCaP, 22Rv1, C4-2, and PC-3) to pharmacologically applicable concentrations of PEITC, benzyl isothiocyanate (BITC), and SFN (2.5 and 5 μmol/L) resulted in downregulation of CXCR4 expression. None of the ITCs affected secretion of CXCR4 ligand (stromal-derived factor-1). In vivo inhibition of PC-3 xenograft growth upon PEITC treatment was associated with a significant decrease in CXCR4 protein level. A similar trend was discernible in the tumors from SFN-treated TRAMP mice compared with those of control mice, but the difference was not significant. Stable overexpression of CXCR4 in PC-3 cells conferred significant protection against wound healing, cell migration, and cell viability inhibition by ITCs. Inhibition of cell migration resulting from PEITC and BITC exposure was significantly augmented by RNAi of CXCR4. This study demonstrates, for the first time, that cancer chemopreventive ITCs suppress CXCR4 expression in prostate cancer cells in vitro as well as in vivo. These results suggest that CXCR4 downregulation may be an important pharmacodynamic biomarker of cancer chemopreventative ITCs in prostate adenocarcinoma.

Downregulation of Kruppel-like factor 2 is associated with poor prognosis for nonsmall-cell lung cancer

Kruppel-like factor 2 (KLF2) expression is diminished in many malignancies. However, its expression and role in nonsmall-cell lung cancer (NSCLC) remain unknown. In this study, we found that KLF2 levels were decreased in NSCLC tissues compared with adjacent normal tissues. Its expression level was significantly correlated with TNM stages, tumor size, and lymph node metastasis. Moreover, patients with low levels of KLF2 expression had a relatively poor prognosis. Furthermore, knockdown of KLF2 expression by siRNA could promote cell proliferation, while ectopic expression of KLF2 inhibited cell proliferation and promoted apoptosis in NSCLC cells partly via regulating CDKN1A/p21 and CDKN2B/p15 protein expression. Our findings present that decreased KLF2 could be identified as a poor prognostic biomarker in NSCLC and regulate cell proliferation and apoptosis.

Kruppel-like factor-9 (KLF9) inhibits glioblastoma stemness through global transcription repression and integrin α6 inhibition

It is increasingly important to understand the molecular basis for the plasticity of neoplastic cells and their capacity to transition between differentiated and stemlike phenotypes. Kruppel-like factor-9 (KLF9), a member of the large KLF transcription factor family, has emerged as a regulator of oncogenesis, cell differentiation, and neural development; however, the molecular basis for the diverse contextual functions of KLF9 remains unclear. This study focused on the functions of KLF9 in human glioblastoma stemlike cells. We established for the first time a genome-wide map of KLF9-regulated targets in human glioblastoma stemlike cells and show that KLF9 functions as a transcriptional repressor and thereby regulates multiple signaling pathways involved in oncogenesis and stem cell regulation. A detailed analysis of one such pathway, integrin signaling, showed that the capacity of KLF9 to inhibit glioblastoma cell stemness and tumorigenicity requires ITGA6 repression. These findings enhance our understanding of the transcriptional networks underlying cancer cell stemness and differentiation and identify KLF9-regulated molecular targets applicable to cancer therapeutics.

Arsenic trioxide inhibits CXCR4-mediated metastasis by interfering miR-520h/PP2A/NF-κB signaling in cervical cancer

BACKGROUND

Arsenic apparently affects numerous intracellular signal transduction pathways and causes many alterations leading to apoptosis and differentiation in malignant cells. We and others have demonstrated that arsenic inhibits the metastatic capacity of cancer cells. Here we present additional mechanistic studies to elucidate the potential of arsenic as a promising therapeutic inhibitor of metastasis.

METHODS

The effects of arsenic trioxide (ATO) on human cervical cancer cell lines migration and invasion were observed by transwell assays. In experimental metastasis assays, cancer cells were injected into tail veins of severe combined immunodeficient mice for modeling metastasis. The mechanisms involved in ATO regulation of CXCR4 were analyzed by immunoblot, real-time polymerase chain reaction, and luciferase reporter assays. Immunohistochemistry was utilized to identify PP2A/C and CXCR4 protein expressions in human cervical cancer tissues.

RESULTS

ATO inhibited CXCR4-mediated cervical cancer cell invasion in vitro and distant metastasis in vivo. We determined that ATO modulates the pivotal nuclear factor-kappa B (NF-κB)/CXCR4 signaling pathway that contributes to cancer metastasis. Substantiating our findings, we demonstrated that ATO activates PP2A/C activity by downregulating miR-520h, which results in IKK inactivation, IκB-dephosphorylation, NF-κB inactivation, and, subsequently, a reduction in CXCR4 expression. Furthermore, PP2A/C was reduced during cervical carcinogenesis, and the loss of PP2A/C expression was closely associated with the nodal status of cervical cancer patients.

CONCLUSIONS

Our results indicate a functional link between ATO-mediated PP2A/C regulation, CXCR4 expression, and tumor-suppressing ability. This information will be critical in realizing the potential for synergy between ATO and other anti-cancer agents, thus providing enhanced benefit in cancer therapy.

Antitumour effect of valproic acid against salivary gland cancer in vitro and in vivo

Salivary gland cancer (SGC) has a comparatively poor prognosis and is prone to frequent recurrence and metastases. Therefore, the development of more effective chemotherapy against SGC is desirable. The aim of the present study was to investigate the antitumour effects of valproic acid (VPA) against SGC in vitro and in vivo. Two human SGC cell lines (HSY and HSG cells) were used in the present study. The effects of VPA on the proliferation of SGC cells in vitro were assessed by MTT assay. Cancer cells treated with VPA were subjected to cell cycle analysis by flow cytometry. In addition, the expression levels of p21 and p27 were examined by real-time RT-PCR to identify the mechanisms of the antitumour effect of VPA on SGC. The effects of VPA on cancer growth in vivo were evaluated in a xenograft model. VPA inhibited the proliferation of SGC cells in a dose-dependent manner in vitro. Degenerated cancer cells were observed at high concentrations of VPA. In the cell cycle analysis, VPA induced cell-growth inhibition and G1 arrest of cell cycle progression in both cancer cell lines in a time- and dose-dependent manner. VPA markedly upregulated the mRNA expression levels of both p21 and p27 in both SGC cell lines in a time-dependent manner. In the xenograft model experiment, VPA treatment markedly inhibited the growth of salivary gland tumours when compared with the growth of the untreated controls. VPA may be a valuable drug in the development of better therapeutic regimens for SGC.

Krüppel-like factors in cancer

Krüppel-like factors (KLFs) are a family of DNA-binding transcriptional regulators with diverse and essential functions in a multitude of cellular processes, including proliferation, differentiation, migration, inflammation and pluripotency. In this Review, we discuss the roles and regulation of the 17 known KLFs in various cancer-relevant processes. Importantly, the functions of KLFs are context dependent, with some KLFs having different roles in normal cells and cancer, during cancer development and progression and in different cancer types. We also identify key questions for the field that are likely to lead to important new translational research and discoveries in cancer biology.

Emerging targets in cancer management: role of the CXCL12/CXCR4 axis

The chemokine CXCL12 (SDF-1) and its cell surface receptor CXCR4 were first identified as regulators of lymphocyte trafficking to the bone marrow. Soon after, the CXCL12/CXCR4 axis was proposed to regulate the trafficking of breast cancer cells to sites of metastasis. More recently, it was established that CXCR4 plays a central role in cancer cell proliferation, invasion, and dissemination in the majority of malignant diseases. The stem cell concept of cancer has revolutionized the understanding of tumorigenesis and cancer treatment. A growing body of evidence indicates that a subset of cancer cells, referred to as cancer stem cells (CSCs), plays a critical role in tumor initiation, metastatic colonization, and resistance to therapy. Although the signals generated by the metastatic niche that regulate CSCs are not yet fully understood, accumulating evidence suggests a key role of the CXCL12/CXCR4 axis. In this review we focus on physiological functions of the CXCL12/CXCR4 signaling pathway and its role in cancer and CSCs, and we discuss the potential for targeting this pathway in cancer management.

The Role of chemokine receptor CXCR4 in breast cancer metastasis

Breast cancer is one of the leading causes of cancer related deaths worldwide. Breast cancer-related mortality is associated with the development of metastatic potential of primary tumor lesions. The chemokine receptor CXCR4 has been found to be a prognostic marker in various types of cancer, including breast cancer. Recent advances in the field of cancer biology has pointed to the critical role that CXCR4 receptor and its ligand CXCL12 play in the metastasis of various types of cancer, including breast cancer. Breast tumors preferentially metastasize to the lung, bones and lymph nodes, all of which represent organs that secrete high levels of CXCL12. CXCL12 acts as a chemoattractant that drives CXCR4-positive primary tumor cells towards secondary metastatic sites leading to the onset of metastatic lesions. Since its discovery in 2001, the CXCR4 field has progressed at a very fast rate and further studies have pointed to the role of CXCR4 in dissemination of tumor cells from primary sites, transendothelial migration of tumor cells as well as the trafficking and homing of cancer stem cells. This review summarizes the information that has been obtained over the years regarding the role of CXCL12-CXCR4 signaling in breast cancer, discusses its potential application to the development of new therapeutic tools for breast cancer control, and elucidates the potential therapeutic challenges which lie ahead and the future directions that this field can take for the improvement of prognosis in breast cancer patients.

CXCL12/CXCR4 axis plays pivotal roles in the organ-specific metastasis of pancreatic adenocarcinoma: A clinical study

Pancreatic cancer is one of the most lethal types of cancer, and curative resection is only applicable to potentially limited cases due to early metastasis and local invasion. This study reports the influence of CXCL12 and its receptor CXCR4 on the progression of pancreatic cancer and highlights the correlation between the CXCL12/CXCR4 axis and the organ-specific metastasis of pancreatic adenocarcinoma (PAC). A total of 34 patients with pancreatic cancer participated in the current study. The expression of CXCL12 and CXCR4 in cancerous tissues, paracancerous tissues, normal pancreas and lymph nodes surrounding the pancreas were investigated using immunohistochemistry and RT-PCR; furthermore, their relationship with clinicopathological factors was explored (PV9000 method). The positive rate of CXCL12 protein was 13.3% (4/30), the positive rate of CXCR4 protein was 80% (24/30) in tumor tissues. Additionally, a significant correlation between the expression pattern of the CXCL12/CXCR4 axis with lymph node metastasis was identified (P<0.05), excluding gender, age, tumor node metastasis (TNM) stage and differentiation (all P>0.05). Also, the positive rate of CXCL12 protein was 50% (15/30), the positive rate of CXCR4 protein was 73.3% (22/30) in the lymphocytes in lymph nodes surrounding the pancreas. Furthermore, we found that CXCL12 and CXCR4 expression in paratumorous vessels and neural tissue were significantly strongly positive. The paratumorous vessels and neural tissue with positive CXCL12 and CXCR4 expression were invaded by CXCL12-positive pancreatic cancer cells. The chemotactic interaction between CXCR4 and its ligand CXCL12 may be a critical event during the progression of pancreatic cancer. The CXCL12/CXCR4 axis plays an important role in the progression and organ-specific metastasis of pancreatic adenocarcinoma.

Mechanotransduction in embryonic vascular development

A plethora of biochemical signals provides spatial and temporal cues that carefully orchestrate the complex process of vertebrate embryonic development. The embryonic vasculature develops not only in the context of these biochemical cues, but also in the context of the biomechanical forces imparted by blood flow. In the mature vasculature, different blood flow regimes induce distinct genetic programs, and significant progress has been made toward understanding how these forces are perceived by endothelial cells and transduced into biochemical signals. However, it cannot be assumed that paradigms that govern the mature vasculature are pertinent to the developing embryonic vasculature. The embryonic vasculature can respond to the mechanical forces of blood flow, and these responses are critical in vascular remodeling, certain aspects of sprouting angiogenesis, and maintenance of arterial-venous identity. Here, we review data regarding mechanistic aspects of endothelial cell mechanotransduction, with a focus on the response to shear stress, and elaborate upon the multifarious effects of shear stress on the embryonic vasculature. In addition, we discuss emerging predictive vascular growth models and highlight the prospect of combining signaling pathway information with computational modeling. We assert that correlation of precise measurements of hemodynamic parameters with effects on endothelial cell gene expression and cell behavior is required for fully understanding how blood flow-induced loading governs normal vascular development and shapes congenital cardiovascular abnormalities.

Sequence-specific recruitment of heterochromatin protein 1 via interaction with Krüppel-like factor 11, a human transcription factor involved in tumor suppression and metabolic diseases

Heterochromatin protein 1 (HP1) proteins are "gatekeepers" of epigenetic gene silencing that is mediated by lysine 9 of histone H3 methylation (H3K9me). Current knowledge supports a paradigm whereby HP1 proteins achieve repression by binding to H3K9me marks and interacting to H3K9 histone methyltransferases (HMTs), such as SUV39H1, which methylate this residue on adjacent nucleosomes thereby compacting chromatin and silencing gene expression. However, the mechanism underlying the recruitment of this epigenetic regulator to target gene promoters remains poorly characterized. In the current study, we reveal for the first time a mechanism whereby HP1 is recruited to promoters by a well characterized Krüppel-like transcription factor (KLF), in a sequence-specific manner, to mediate complex biological phenomena. A PXVXL HP1-interacting domain identified at position 487-491 of KLF11 mediates the binding of HP1α and KLF11 in vitro and in cultured cells. KLF11 also recruits HP1α and its histone methyltransferase, SUV39H1, to promoters to limit KLF11-mediated gene activation. Indeed, a KLF11ΔHP1 mutant derepresses KLF11-regulated cancer genes, by inhibiting HP1-SUV39H1 recruitment, decreasing H3K9me3, while increasing activation-associated marks. Biologically, impairment of KLF11-mediated HP1-HMT recruitment abolishes tumor suppression, providing direct evidence that HP1-HMTs act in a sequence-specific manner to achieve this function rather than its well characterized binding to methylated chromatin without intermediary. Collectively, these studies reveal a novel role for HP1 as a cofactor in tumor suppression, expand our mechanistic understanding of a KLF associated to human disease, and outline cellular and biochemical mechanisms underlying this phenomenon, increasing the specificity of targeting HP1-HMT complexes to gene promoters.

PEA3 activates CXCR4 transcription in MDA-MB-231 and MCF7 breast cancer cells

CXC chemokine receptor 4 (CXCR4) is a cell surface receptor that has been shown to mediate the metastasis of many solid tumors including lung, breast, kidney, and prostate tumors. In this study, we found that overexpression of ets variant gene 4 (PEA3) could elevate CXCR4 mRNA level and CXCR4 promoter activity in human MDA-MB-231 and MCF-7 breast cancer cells. PEA3 promoted CXCR4 expression and breast cancer metastasis. Chromatin immunoprecipitation assay demonstrated that PEA3 could bind to the CXCR4 promoter in the cells transfected with PEA3 expression vector. PEA3 siRNA attenuated CXCR4 promoter activity and the binding of PEA3 to the CXCR4 promoter in MDA-MB-231 and MCF-7 cells. These results indicated that PEA3 could activate CXCR4 promoter transcription and promote breast cancer metastasis.

Homeostatic chemokine receptors and organ-specific metastasis

It has been 10 years since the role of a chemokine receptor, CXCR4, in breast cancer metastasis was first documented. Since then, the field of chemokines and cancer has grown significantly, so it is timely to review the progress, analyse the studies to date and identify future challenges facing this field. Metastasis is the major factor that limits survival in most patients with cancer. Therefore, understanding the molecular mechanisms that control the metastatic behaviour of tumour cells is pivotal for treating cancer successfully. Substantial experimental and clinical evidence supports the conclusion that molecular mechanisms control organ-specific metastasis. One of the most important mechanisms operating in metastasis involves homeostatic chemokines and their receptors. Here, we review this field and propose a model of 'cellular highways' to explain the effects of homeostatic chemokines on cancer cells and how they influence metastasis.

Interaction between alk1 and blood flow in the development of arteriovenous malformations

Arteriovenous malformations (AVMs) are fragile direct connections between arteries and veins that arise during times of active angiogenesis. To understand the etiology of AVMs and the role of blood flow in their development, we analyzed AVM development in zebrafish embryos harboring a mutation in activin receptor-like kinase I (alk1), which encodes a TGFβ family type I receptor implicated in the human vascular disorder hereditary hemorrhagic telangiectasia type 2 (HHT2). Our analyses demonstrate that increases in arterial caliber, which stem in part from increased cell number and in part from decreased cell density, precede AVM development, and that AVMs represent enlargement and stabilization of normally transient arteriovenous connections. Whereas initial increases in endothelial cell number are independent of blood flow, later increases, as well as AVMs, are dependent on flow. Furthermore, we demonstrate that alk1 expression requires blood flow, and despite normal levels of shear stress, some flow-responsive genes are dysregulated in alk1 mutant arterial endothelial cells. Taken together, our results suggest that Alk1 plays a role in transducing hemodynamic forces into a biochemical signal required to limit nascent vessel caliber, and support a novel two-step model for HHT-associated AVM development in which pathological arterial enlargement and consequent altered blood flow precipitate a flow-dependent adaptive response involving retention of normally transient arteriovenous connections, thereby generating AVMs.

Blockade of CXCR4 in oral squamous cell carcinoma inhibits lymph node metastases

We have previously demonstrated that a stromal cell-derived factor-1 (SDF-1; CXCL12)/CXCR4 system is involved in the establishment of lymph node metastasis in oral squamous cell carcinoma (OSCC). In this study, we investigated whether the blockade of CXCR4 inhibits lymph node metastasis in B88 OSCC cells. These cells harbour a functional CXCR4 and have the potential to metastasise to the lymph node in vivo. Following introduction of a vector that expresses short hairpin small interfering RNA (shRNA) against CXCR4, we isolated three clones (shCXCR4-16, -17 and -21) that showed decreased expression of CXCR4 mRNA. These clones also had reduced CXCR4 protein levels and showed impairments in calcium flux and cell migration in response to SDF-1. These cells were orthotopically inoculated into the masseter muscle of nude mice. Lymph node metastases, loss in body weight and tumour volumes were significantly inhibited in mice inoculated with shCXCR4-17 cells compared to mice inoculated with control cells. SDF-1-induced migration of B88 cells was significantly inhibited in vitro by the treatment with 1,1'-[1,4-phenylenebis(methylene)]bis-1,4,8,11-tetraazacyclotetradecane octahydrochloride (AMD3100), a CXCR4 antagonist. Subcutaneous administration of AMD3100 significantly inhibited the lymph node metastases of B88 cells when they were orthotopically inoculated into the masseter muscle of nude mice. Moreover, the enhanced production of interleukin (IL)-6 and IL-8 in response to SDF-1 was inhibited by shRNA against CXCR4 or by treatment with AMD3100. These results suggest that blockade of CXCR4 may be a potent anti-metastatic therapy against lymph node metastases in cases of CXCR4-related OSCC.

The CXCR4-CXCL12 pathway facilitates the progression of pancreatic cancer via induction of angiogenesis and lymphangiogenesis

BACKGROUND

This study reports the influence of CXCL12 and its receptor CXCR4 on the progression of pancreatic cancer and illuminates the correlation between the CXCL12/CXCR4 axis and the angiogenesis and lymphangiogenesis of pancreatic adenocarcinoma (PAC).

METHODS

A total of 30 patients with pancreatic cancer participated in the current study. The expression of CXCL12 and CXCR4 in cancerous tissues, paracancerous tissues, normal pancreas, and lymph nodes surrounding the pancreas were investigated using real-time PCR and immunohistochemistry, respectively. In addition, we assessed microvessel density (MVD) and microlymphatic vessel density (MLVD) in tumor tissues using immunohistochemistry.

RESULTS

CXCL12 expression in tumor tissues was significantly lower than that of paracancerous tissues, normal pancreas, and lymph nodes. In contrast, CXCR4 expression in cancerous tissues was considerably higher than that of normal pancreas. Additionally, a significant correlation between the expression pattern of the CXCL12/CXCR4 axis and clinicopathologic features, such as lymph node metastasis, was identified. Furthermore, we found that CXCL12 expression was significantly associated with MVD but not significantly associated with MLVD, while CXCR4 expression was significantly associated with MLVD but not significantly associated with MVD.

CONCLUSIONS

The chemotactic interaction between CXCR4 and its ligand CXCL12 may be a critical event during the progression of pancreatic cancer. The underlying mechanism may be the induction of angiogenesis and lymphangiogenesis regulated by the interaction of CXCL12 and CXCR4.