Stress-Induced CXCR4 Promotes Migration and Invasion of Ewing Sarcoma

Abstract

Ewing sarcoma is the second most common bone cancer in pediatric patients. Although the primary cause of death in Ewing sarcoma is metastasis, the mechanism underlying tumor spread needs to be elucidated. To this end, the role of the CXCR4/SDF-1a chemokine axis as a mediator of Ewing sarcoma metastasis was investigated. CXCR4 expression status was measured in primary tumor specimens by immunohistochemical (IHC) staining and in multiple cell lines by quantitative RT-PCR and flow cytometry. Migration and invasion of CXCR4-positive Ewing sarcoma cells towards CXCL12/SDF-1a were also determined. Interestingly, while CXCR4 status was disparate among Ewing sarcoma cells, ranging from absent to high-level expression; its expression was found to be highly dynamic and responsive to changes in the microenvironment. In particular, up-regulation of CXCR4 occurred in cells that were subjected to growth factor deprivation, hypoxia, and space constraints. This up-regulation of CXCR4 was rapidly reversed upon removal of the offending cellular stress conditions. Functionally, CXCR4-positive cells migrated and invaded towards an SDF-1a gradient and these aggressive properties were impeded by both the CXCR4 small molecule inhibitor AMD3100, and by knockdown of CXCR4. In addition, CXCR4-dependent migration and invasion were inhibited by small molecule inhibitors of Cdc42 and Rac1, mechanistically implicating these Rho-GTPases as downstream mediators of the CXCR4-dependent phenotype.

CXCL14, CXCR7 expression and CXCR4 splice variant ratio associate with survival and metastases in Ewing sarcoma patients

“…In addition, we studied expression levels of the earlier reported CXCR4 isoforms in tumour samples as the expression of these isoforms in particular might partly be responsible for the contradictory results [15,16,20]. All chemokines and receptors of the CXCR4-CXCR7 axis were expressed in EWS but a large variation was observed between individual samples, consistent with previous observations [16,27]. The observed increased expression of CXCR7 and CXCL12 in tumour samples compared to cell lines could be stromal derived since both endothelial and perivascular cells express CXCR7 and CXCL12 and EWS is highly vascularised [28,29].…”

“…expression has been shown in EWS and this may hold for CXCR7 as well [27]. The local tumour microenvironment can be an influencing factor here as well.…”

The Ewing Sarcoma Secretome and Its Response to Activation of Wnt/beta-catenin Signaling

“…Previous reports have shown that the bone TME specifically promotes metastatic progression of Ewing sarcoma (9) and that its ability to grow in bone is dependent on the osteolytic phenotype (10). Moreover, a hypoxic microenvironment promotes activation of metastasis-associated gene expression in tumor cells and enhanced metastatic progression in xenograft models (11,12). In addition, gene expression profiling studies of primary localized tumor specimens demonstrated the important contribution of tumor stroma to relapse and patient survival (13).…”

Endocytotic uptake of HPMA-based polymers by different cancer cells: impact of extracellular acidosis and hypoxia

“…Since hypoxia is also suitable to activate Rho-GTPases as part of the stress response, 38 this behavior may rely on a …”