Epstein-Barr virus-induced VEGF and GM-CSF drive nasopharyngeal carcinoma metastasis via recruitment and activation of macrophages

Chronic inflammation induced by persistent microbial infection plays an essential role in tumor progression. Although it is well documented that Epstein-Barr virus (EBV) infection is closely associated with nasopharyngeal carcinoma (NPC), how EBV-induced inflammation promotes NPC progression remains largely unknown. Here we report that tumor infiltration of tumor associated macrophages (TAM) and expression of CCL18, the cytokine preferentially secreted by TAM, closely correlate with serum EBV infection titers and tumor progression in two cohorts of NPC patients. In vitro, compared to EBV- NPC cell lines, EBV+ NPC cell lines exhibited superior capacity to attract monocytes and skew them to differentiate to a TAM-like phenotype. Cytokine profiling analysis revealed that NPC cells with active EBV replications recruited monocytes by VEGF and induced TAM by GM-CSF in an NFκB-dependent manner. Reciprocally, TAM induced epithelial-mesenchymal transition (EMT) and further NFκB activation of tumor cells by CCL18. In humanized mice, NPC cells with active EBV replications exhibited increased metastasis, and neutralization of CCL18, GM-CSF and VEGF significantly reduced metastasis. Collectively, our work defines a feed-forward loop between tumor cells and macrophages in NPC which shows how metastatic potential can evolve concurrently with virus-induced chronic inflammation.

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