Significance of chemokine and chemokine receptors in head and neck squamous cell carcinoma: A critical review

CR5/CCL5 axis is linked to a poor outcome, and inhibition reduces metastasis in oral squamous cell carcinoma

PURPOSE

The CCR5/CCL5 axis is essential for interactions between malignant cells and microenvironment components, promoting tumor progression in oral squamous cell carcinoma (OSCC). This study aims to evaluate the association of CCL5 and CCR5 with the behavior of oral cancer and assess the therapeutic potential of a CCR5 antagonist.

METHODS

A retrospective study to analyze CCR5 and CCL5 expression on paraffin-embedded tissues was performed. In cell lines, rhCCL5 was added to induce CCR5-related pathways, and Maraviroc and shRNA against CCR5 were used to neutralize the receptor. Finally, an in vivo murine orthotopic xenograft model of tongue cancer was used to evaluate Maraviroc as an oncologic therapy. After 15 days, the mice were killed, and the primary tumors and cervical lymph nodes were analyzed.

RESULTS

The expression of CCR5 was associated with clinical stage and metastasis, and CCL5 was related to overall survival. Adding rhCCL5 induced cell proliferation, while shRNA and Maraviroc reduced it in a dose-dependent manner. Maraviroc treatment also increased apoptosis and modified cytoskeletal organization. In vivo, Maraviroc reduced neck metastasis.

CONCLUSIONS

The effects of CCR5 antagonists in OSCC have been poorly studied, and this study reports in vitro and in vivo evidence for the effects of Maraviroc in OSCC. Our results suggest that the CCR5/CCL5 axis plays a role in oral cancer behavior, and that its inhibition is a promising new therapy alternative.

CXCL14-like immunoreactivity in somatostatin-producing cells of the Japanese quail (Coturnix japonica) pancreas

This study examines chemokine CXCL14-like peptide distribution in the Japanese quail (Coturnix japonica) pancreas using a specific anti-human CXCL14 antibody. CXCL14-immunoreactive cells were observed in the pancreatic islet peripheral region. The staining was abolished after pre-absorbing the antibody with recombinant human CXCL14. CXCL14-immunoreactive cells were immuno-positive for somatostatin, but not glucagon and insulin. CXCL14 secreted from somatostatin-producing cells might participate in insulin secretion modulation together with somatostatin. In addition, CXCL14 might participate in glucose homeostasis in co-operation with somatostatin and growth hormone.

Identification and Biological Validation of a Chemokine/Chemokine Receptor-Based Risk Model for Predicting Immunotherapeutic Response and Prognosis in Head and Neck Squamous Cell Carcinoma

Over 80% of head and neck squamous cell carcinoma (HNSCC) patients failed to respond to immunotherapy, which can likely be attributed to the tumor microenvironment (TME) remolding mediated by chemokines/chemokine receptors (C/CR). This study aimed to establish a C/CR-based risk model for better immunotherapeutic responses and prognosis. After assessing the characteristic patterns of the C/CR cluster from the TCGA-HNSCC cohort, a six-gene C/CR-based risk model was developed to stratify patients by LASSO Cox analysis. The screened genes were multidimensionally validated by RT-qPCR, scRNA-seq, and protein data. A total of 30.4% of patients in the low-risk group had better responses to anti-PD-L1 immunotherapy. A Kaplan-Meier analysis showed that patients in the low-risk group had longer overall survival. A time-dependent receiver operating characteristic curve and Cox analyses indicated that risk score served as an independent predictive indicator. The robustness of the immunotherapy response and prognosis prediction was also validated in independent external datasets. Additionally, the TME landscape revealed that the low-risk group was immune activated. Furthermore, the cell communication analysis on the scRNA-seq dataset revealed that cancer-associated fibroblasts were the main communicators within the C/CR ligand-receptor network of TME. Collectively, The C/CR-based risk model simultaneously predicted immunotherapeutic response and prognosis, potentially optimizing personalized therapeutic strategies of HNSCC.

Modulation of diverse oncogenic signaling pathways by oroxylin A: An important strategy for both cancer prevention and treatment

BACKGROUND

Regardless of major advances in diagnosis, prevention and treatment strategies, cancer is still a foreboding cause due to factors like chemoresistance, radioresistance, adverse side effects and cancer recurrence. Therefore, continuous development of unconventional approaches is a prerequisite to overcome foregoing glitches. Natural products have found their way into treatment of serious health conditions, including cancer since ancient times. The compound oroxylin A (OA) is one among those with enormous potential against different malignancies. It is a flavonoid obtained from the several plants such as Oroxylum indicum, Scutellaria baicalensis and S. lateriflora, Anchietea pyrifolia, and Aster himalaicus.

PURPOSE

The main purpose of this study is to comprehensively elucidate the anticancerous effects of OA against various malignancies and unravel their chemosensitization and radiosensitization potential. Pharmacokinetic and pharmacodynamic studies of OA have also been investigated.

METHOD

The literature on antineoplastic effects of OA was searched in PubMed and Scopus, including in vitro and in vivo studies and is summarized based on a systematic review protocol prepared according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The term "oroxylin A" was used in combination with "cancer" and all the title, abstracts and keywords appeared were considered.

RESULTS

In Scopus, a total of 157 articles appeared out of which 103 articles that did not meet the eligibility criteria were eliminated and 54 were critically evaluated. In PubMed, from the 85 results obtained, 26 articles were eliminated and 59 were included in the preparation of this review. Mounting number of studies have illustrated the anticancer effects of OA, and its mechanism of action.

CONCLUSION

OA is a promising natural flavonoid possessing wide range of pleiotropic properties and is a potential anticancer agent. It has a great potential in the treatment of multiple cancers including brain, breast, cervical, colon, esophageal, gall bladder, gastric, hematological, liver, lung, oral, ovarian, pancreatic and skin. However, lack of pharmacokinetic studies, toxicity assessments, and dose standardization studies and adverse effects limit the optimization of this compound as a therapeutic agent.

Simultaneous Expression of Th1- and Treg-Associated Chemokine Genes and CD4+, CD8+, and Foxp3+ Cells in the Premalignant Lesions of 4NQO-Induced Mouse Tongue Tumorigenesis

Chemokines and cytokines in the tumor microenvironment influence immune cell infiltration and activation. To elucidate their role in immune cell recruitment during oral cancer development, we generated a mouse tongue cancer model using the carcinogen 4-nitroquinoline 1-oxide (4NQO) and investigated the carcinogenetic process and chemokine/cytokine gene expression kinetics in the mouse tongue. C57/BL6 mice were administered 4NQO in drinking water, after which tongues were dissected at 16 and 28 weeks and subjected to analysis using the RT² Profiler PCR Array, qRT-PCR, and pathologic and immunohistochemical analyses. We found that Th1-associated chemokine/cytokine (Cxcl9, Cxcl10, Ccl5, and Ifng) and Treg-associated chemokine/cytokine (Ccl17, Ccl22, and Il10) mRNA levels were simultaneously increased in premalignant lesions of 4NQO-treated mice at 16 weeks. Additionally, although levels of Gata3, a Th2 marker, were not upregulated, those of Cxcr3, Ccr4, and Foxp3 were upregulated in the tongue tissue. Furthermore, immunohistochemical analysis confirmed the infiltration of CD4⁺, CD8⁺, and Foxp3⁺ cells in the tongue tissue of 4NQO-treated mice, as well as significant correlations between Th1- or Treg-associated chemokine/cytokine mRNA expression and T cell infiltration. These results indicate that CD4⁺, CD8⁺, and Foxp3⁺ cells were simultaneously recruited through the expression of Th1- and Treg-associated chemokines in premalignant lesions of 4NQO-induced mouse tongue tissue.

Bioinformatics and immunohistochemistry analyses of expression levels and clinical significance of CXCL2 and TANs in an oral squamous cell carcinoma tumor microenvironment of Prophyromonas gingivalis infection

The present study aimed to detect the immunoexpression and clinical significance of Porphyromonas gingivalis (P. gingivalis) in the tumor microenvironment (TME) of oral squamous cell carcinoma (OSCC). The immunoexpression of P. gingivalis in OSCC tissues was detected via immunohistochemistry (IHC) after P. gingivalis was infected into the TME of OSCC. To identify the differentially expressed genes in the carcinogenesis and progression of OSCC with P. gingivalis infection, microarray datasets (GSE87539 and GSE138206) were downloaded from the Gene Expression Omnibus database. The immunoexpression levels of C-X-C motif chemokine ligand 2 (CXCL2) and tumor-associated neutrophils (TANs) were also evaluated via IHC, and the immunoexpression levels of all three clinical variables were analyzed using χ² or Fisher's exact tests. The survival rates were calculated using the Kaplan-Meier method and the survival curves were compared using log-rank tests. Predominantly strong immunoexpression of P. gingivalis was identified in OSCC samples. CXCL2 was considered to be a differential gene in the two datasets. Immunoexpression of P. gingivalis was positively associated with CXCL2 and TANs expression. Furthermore, P. gingivalis was associated with survival status (P<0.001) and differentiation (P<0.001). CXCL2 was associated with age (P=0.038) and survival status (P=0.003), while TANs were associated with T stage (P=0.015) and clinical stage (P=0.002). These clinical variables were considered to be independent risk factors for the poor prognosis of patients with OSCC. Collectively, the results suggested that the immunoexpression of P. gingivalis may be positively associated with CXCL2 and TANs. In addition, the strong immunoexpression levels of P. gingivalis, CXCL2 and TANs may be associated with a poor prognosis in patients with OSCC.

The Chemokine CXCL14-like Immunoreactivity Co-exists with Somatostatin, but not NPY in the Rat Dorsal Horn and Has Intimate Association with GABAergic Neurons in the Lateral Spinal Nucleus

Recent studies have proposed that the chemokine CXCL14 not only has a chemotactic activity, but also functions as a neuromodulator and/or neurotransmitter. In this study, we investigated the distribution of CXCL14 immunoreactive structures in the rat spinal cord and clarified the association of these structures with somatostatin, glutamic acid decarboxylase (GAD; a marker for GABAergic neurons), and neuropeptide Y (NPY). CXCL14 immunoreactive fibers and puncta were observed in lamina II, which modulates somatosensation including nociception, and the lateral spinal nucleus of the spinal dorsal horn at cervical, thoracic, and lumber spinal cord levels. These CXCL14 immunoreactive structures were also immuno-positive for somatostatin, but were immuno-negative for GAD and NPY. In the cervical lateral spinal nucleus, CXCL14 immunoreactive puncta, which were also immuno-positive for somatostatin, existed along the proximal dendrites of some of GABAergic neurons. Together, these results suggest that CXCL14 contributes to the modulation of somatosensation in concert with somatostatin. Neurons targeted by the CXCL14 fiber system include GABAergic neurons located in the lateral spinal nucleus suggesting that CXCL14 with somatostatin can influence the GABAergic neuron function.

Chemokine CXCL14-like immunoreactivity in the αMSH-producing cells and PRL-producing cells of the flat-tailed house gecko pituitary

The distribution pattern of chemokine CXCL14-immunoreactive cells was examined by immunohistochemistry in the pituitary of the gecko Hemidactylus platyurus. Immunoreactive cells were observed in the pars intermedia and pars distalis of the pituitary, but not in the pars nervosa. All α-melanocyte-stimulating hormone (αMSH)-producing cells were immunoreactive for CXCL14 in the pars intermedia. The CXCL14-immunoreactive cells corresponded to prolactin (PRL)-producing cells but not to other adenohypophyseal-hormone-producing cells in the pars distalis. CXCL14 secreted from αMSH-producing cells and PRL-producing cells may regulate insulin release from β cells in the pancreatic islets as well as glucose uptake in the muscle cells together with αMSH and/or PRL. In addition, secreted CXCL14 with αMSH and/or PRL may act as a bioactive factor regulating hormone release in the adenohypophyseal cells of the reptilian pars distalis.

Laryngeal Tumor Microenvironment

Tumor microenvironment has been extensively studied in various forms of cancer, like head and neck squamous cell carcinoma. Progress in the field revealed the prognostic significance of the various components of the tumor's ecosystem and led to changes in treatment strategies, like including immunotherapy as an important tool. In this chapter, the microenvironment of tumors with a special interest in laryngeal cancer will be described. The issues assessed include innate immune response factors, like neutrophils, neutrophil extracellular traps (NET), platelets, macrophages M1 or M2, dendritic cells, natural killer cells, as well as adaptive immunity aspects, like cytotoxic, exhausted and regulatory T cells, and immune checkpoints (PD-1/PD-L1, CTLA4). Also, stroma-associated factors, like fibroblasts, fibrosis, extracellular matrix, vessels and perineural invasion, hypoxia and cancer metabolism aspects, as well as the pre-metastatic niche, exosomes and cGAS-STING, are reviewed.

Long-Term Exposure to Oroxylin A Inhibits Metastasis by Suppressing CCL2 in Oral Squamous Cell Carcinoma Cells

Oroxylin A (Oro-A), the main bioactive flavonoid extracted from Scutellaria radix, has been reported to inhibit migration in various human cancer cell models. In this study, we further explored the anti-migration effects of Oro-A on oral squamous cell carcinoma (OSCC) cells and investigated the underlying mechanisms. A 24-h (short-term) exposure of OSCC cells to non-cytotoxic concentrations (5–20 μM) of Oro-A significantly suppressed cell migration according to a wound-healing assay. Furthermore, a 30-day exposure (long-term) to Oro-A (20 μM), which did not exhibit a cytotoxic effect on OSCC cells, significantly suppressed cell migration more than short-term Oro-A exposure. To uncover the molecular mechanisms underlying the inhibitory effect of long-term Oro-A exposure on OSCC migration, a cDNA microarray and the Ingenuity software were used. Overall, 112 upregulated and 356 downregulated genes were identified in long-term Oro-A-exposed cells compared with untreated OSCC cells. Among them, 75 genes were reported to be associated with cancer cell migration. Consistent with the cDNA microarray results, we found that the expression levels of several cell migration-related genes, such as LCN2, ID-1, MDK, S100A9 and CCL2, were significantly decreased in long-term Oro-A-exposed OSCC cells using a quantitative real-time polymerase chain reaction (Q-PCR) assay. The Western blotting and enzyme-linked immunosorbent assay (ELISA) results also demonstrated that CCL2 expression at the mRNA and protein levels was significantly decreased in long-term Oro-A-exposed OSCC cells compared with untreated OSCC cells. Moreover, the expression levels of downstream CCL2 targets, including p-ERK1/2, NFκB, MMP2, and MMP9, were also decreased in long-term Oro-A-exposed OSCC cells. Further, Oro-A treatment suppressed in vivo metastasis. These results suggest that long-term Oro-A treatment inhibits metastasis via CCL2 signaling in OSCC cells.

The IL-1/IL-1R axis induces greater fibroblast-derived chemokine release in human papillomavirus-negative compared to positive oropharyngeal cancer

Human papillomavirus (HPV) is now recognised as a major aetiological agent in the pathogenesis of oropharyngeal carcinoma (OPC). HPV-positive tumours are associated with better outcomes compared to HPV-negative tumours, possibly due to differences in their aetiology and/or the tumour microenvironment. Increased numbers of tumour-associated leukocytes have been observed in many cancers including OPC, with variable influence on prognosis depending on the leukocyte subpopulation investigated. Whether HPV status influences leukocyte recruitment to OPC remains unknown. This in-vitro study examined differences in the chemoattractant capacity of HPV-positive and HPV-negative OPC cell lines. Gene and protein expression analysis demonstrated that whilst both monocultures of HPV-positive and HPV-negative cell lines, along with normal tonsillar fibroblasts (NTF), expressed low chemokine levels, NTF cultured with conditioned medium from HPV-negative OPC cells expressed significantly higher levels of all chemokines tested compared to NTF incubated with the medium from HPV-positive OPC cell lines. HPV-negative OPC lines expressed IL-1β mRNA whereas HPV-positive cells did not, and NTF constitutively expressed IL-1R1. Pre-treatment with the IL-R antagonist, anakinra or siRNA to IL-1R1 significantly reduced chemokine secretion from NTF stimulated with conditioned medium from HPV-negative tumour cells or recombinant IL-1β (p < 0.05). These data suggest that secretion of chemokines is driven by the interaction between HPV-negative OPC cells and stromal fibroblasts through an IL-1/IL-1R-mediated mechanism that is less prominent within the HPV-positive tumour microenvironment. These observations may explain differences in leukocyte sub-populations recruited to HPV-positive versus negative OPC and indicate that HPV status is a key determinant in controlling the inflammatory tumour microenvironment.

Hypoxia modulates CCR7 expression in head and neck cancers

BACKGROUND

The chemokine receptor CCR7 is expressed on lymphocytes and dendritic cells and is responsible for trafficking of these cells in and out of secondary lymphoid organs. It has recently been shown that CCR7 expression is elevated in a number of cancers, including head and neck cancers, and that its expression correlates to lymph node (LN) metastasis. However, little is known about the factors that can induce CCR7 expression in head and neck cancers.

METHOD

We compared the protein expression and functional responses of CCR7 under normoxia and hypoxia in head and neck cancer cell lines OSC-19, FaDu, SCC-4, A-253 and Detroit-562 cultured as monolayers, spheroids, and grown in vivo as xenografts in balb/c mice. In addition, we analysed the correlation between hypoxia marker HIF-1α and CCR7 expression in a tissue microarray comprising 80 clinical samples with various stages and grades of malignant tumour and normal tissue.

RESULTS

Under hypoxia, the expression of CCR7 is elevated in both in vitro and in vivo models. Furthermore, in malignant tissue, a correlation is observed between hypoxia marker HIF-1α and CCR7 across all clinical stages. This correlation is also strong in early histological grade of tumours.

CONCLUSION

Hypoxia plays a role in the regulation of the expression of CCR7 and it may contribute to the development of a metastatic phenotype in head and neck cancers through this axis.

CXCL14-like Immunoreactivity Exists in Somatostatin-containing Endocrine Cells, and in the Lamina Propria and Submucosal Somatostatinergic Nervous System of Mouse Alimentary Tract

In the present study, we investigated the distribution of CXCL14 immunoreactive endocrine cells and neurons in mouse alimentary tract by immunohistochemistry. CXCL14 immunoreactive endocrine cells were found as closed-type cells in the stomach and open-type cells in the small intestine. The immunostaining of these endocrine cells corresponded with that of the somatostatin-containing endocrine cells. Only a few CXCL14 immunoreactive endocrine cells were seen in the large intestine. CXCL14 immunoreactive fibers were observed in the muscular layer from the stomach to the rectum with most abundance in the rectum. Many CXCL14 immunoreactive fibers were observed in the lamina propria and submucosal layer from the duodenum to the rectum with most abundance in the rectum; these fibers corresponded to the somatostatin-containing nerve fibers. Some CXCL14 immunoreactive neuronal somata that were also immuno-positive for somatostatin, were noted in the submucosal layer of the rectum. However, the remaining parts of the alimentary tract presented with almost negligible immunoreactive somata. The co-localization of CXCL14 and somatostatin suggests that CXCL14 contributes to the function of somatostatin, which include the inhibition of other endocrine and exocrine cells and the enteric nervous systems.

Investigation of proliferation and migration of tongue squamous cell carcinoma promoted by three chemokines, MIP-3α, MIP-1β, and IP-10

The aim of this work was to investigate the role of chemokines in proliferation and migration of tongue squamous cell carcinoma (TSCC). Out of the 80 cytokines surveyed by a human cytokine antibody array, three chemokines, macrophage inflammatory protein-3α (MIP-3α), macrophage inflammatory protein-1β (MIP-1β), and interferon gamma-induced protein 10 (IP-10), showed elevated expression in TSCC cells (CAL-27 and UM-1), compared to the oral mucosal epithelial cells. Immunohistochemistry confirmed the high level of expression of MIP-3α in the TSCC tissues, especially in the high clinical stages. Furthermore, Western blot and immunofluorescence staining indicated that C-C chemokine receptor type 5, C-C chemokine receptor type 6, and C-X-C motif chemokine receptor 3, which are the receptors for MIP-3α, MIP-1β, and IP-10, respectively, were expressed in the TSCC cells. Viability assay showed MIP-3α, MIP-1β, and IP-10 led to the proliferation of the CAL-27 cells. Interestingly, MIP-1β and IP-10 also induced apoptosis in the TSCC cells. Transwell invasion assay showed MIP-3α and IP-10 could increase the invasive capability of TSCC cells; consistently, the enzymatic activities of matrix metalloproteinase-2 and matrix metalloproteinase-9 increased in the MIP-3α- and IP-10-treated cells. In summary, our results indicate the expression of MIP-3α, MIP-1β, and IP-10 increased in the TSCC cells. The elevated expression of MIP-3α and IP-10 promoted proliferation and migration of TSCC. These chemokines, along with their receptors, could be potential biomarkers and therapeutic targets for TSCC, especially for those in the high clinical stages.

Detection of high serum concentration of CXC chemokine ligand-12 in acute intracerebral hemorrhage

BACKGROUND

CXC chemokine ligand-12 (CXCL12), a member of the CXC chemokine subfamily, is involved in both focal angiogenesis and inflammatory reactions. We examined serum CXCL12 concentration in intracerebral hemorrhage (ICH) patients and its correlation to stroke severity and outcome.

METHODS

The study was carried out on 105 ICH patients on 105 healthy controls. Serum samples were at admission obtained to measure CXCL12 concentrations. The National Institutes of Health Stroke Scale (NIHSS) and hematoma volume were recorded to assess stroke severity.

RESULTS

As compared to the controls, CXCL12 concentrations were significantly increased in the patients. Also, non-survivors within 6months and patients with an unfavorable outcome (modified Rankin Scale score>2) at 6months had higher CXCL12 concentrations than other remaining ones. CXCL12 concentrations had positive correlation with NIHSS scores and hematoma volume. Serum CXCL12 significantly discriminated patients at risk of 6-month mortality and 6-month unfavorable outcome under receiver operating characteristic curve. Moreover, serum CXCL12 was independently associated with the mortality, overall survival and unfavorable outcome.

CONCLUSIONS

Serum CXCL12 concentrations are enhanced after ICH and CXCL12 in serum has the potential to reflect severity and prognosis following hemorrhagic stroke.

Relevance of CCL3/CCR5 axis in oral carcinogenesis

The chemokine CCL3 is a chemotactic cytokine crucial for inflammatory cell recruitment in homeostatic and pathological conditions. CCL3 might stimulate cancer progression by promoting leukocyte accumulation, angiogenesis and tumour growth. The expression of CCL3 and its receptors CCR1 and CCR5 was demonstrated in oral squamous cell carcinoma (OSCC), but their role was not defined. Here, the functions of CCL3 were assessed using a model of chemically induced tongue carcinogenesis with 4-nitroquinoline-1-oxide (4NQO). Lineages of OSCC were used to analyse the effects of CCL3 in vitro. The 4NQO-induced lesions exhibited increased expression of CCL3, CCR1 and CCR5. CCL3^-/- and CCR5^-/- mice presented reduced incidence of tongue tumours compared to wild-type (WT) and CCR1^-/- mice. Consistently, attenuated cytomorphological atypia and reduced cell proliferation were observed in lesions of CCL3^-/- and CCR5^-/- mice. OSCC from CCL3^-/- mice exhibited lower infiltration of eosinophils and reduced expression of Egf, Fgf1, Tgf-β1, Vegfa, Vegfb, Itga-4, Vtn, Mmp-1a, Mmp-2 and Mmp-9 than WT mice. In vitro, CCL3 induced invasion and production of CCL5, IL-6, MMP -2, -8, -9. Blockage of CCL3 in vitro using α-CCL3 or Evasin-1 (a CCL3-binding protein) impaired tumour cell invasion. In conclusion, CCL3/CCR5 axis has pro-tumourigenic effects in oral carcinogenesis. The induction of inflammatory and angiogenic pathways and eosinophils recruitment appear to be the underlying mechanism explaining these effects. These data reveal potential protective effects of CCL3 blockade in oral cancer.

CXCL5 Plays a Promoting Role in Osteosarcoma Cell Migration and Invasion in Autocrine- and Paracrine-Dependent Manners

CXCL5, a CXC-type chemokine, is an important attractant for granulocytic immune cells by binding to its receptor CXCR2. Recently, CXCL5/CXCR2 has been found to play an oncogenic role in many human cancers. However, the exact role of CXCL5 in osteosarcoma cell migration and invasion has not been revealed. Here we found that the protein expression of CXCL5 was significantly increased in osteosarcoma tissues compared with that in matched adjacent nontumor tissues. Moreover, the expression of CXCL5 was significantly associated with advanced clinical stage and metastasis. Further investigation showed that the CXCL5 expression levels were also significantly increased in osteosarcoma cell lines, including Saos-2, MG63, U2OS, and SW1353, when compared with those in normal osteoblast hFoB1.19 cells. U2OS cells were further transfected with CXCL5-specific siRNA or overexpression plasmid. Knockdown of CXCL5 significantly suppressed U2OS cell migration and invasion. On the contrary, overexpression of CXLC5 remarkably promoted the migration and invasion of U2OS cells. Interestingly, both exogenous CXCL5 treatment and the conditioned medium of CXCL5-overexpressing hFoB1.19 cells could also enhance the migration and invasion of U2OS cells, suggesting that the promoting role of CXCL5 in U2OS cell migration and invasion is also in a paracrine-dependent manner. According to these data, our study demonstrates that CXCL5 is upregulated in osteosarcoma and may play an oncogenic role in osteosarcoma metastasis. Therefore, CXCL5 may become a potential therapeutic target for osteosarcoma treatment.