CCL2/CCR2 axis signaling promotes metastasis of nasopharyngeal carcinoma by activating ERK1/2 pathway via upregulating MMP2 and MMP9

Abstract

Despite tremendous progress in diagnosis and treatments of nasopharyngeal carcinoma (NPC) has been established nowadays, distant metastasis remains the major cause of death.The underlying molecular mechanisms are largely unknown. In the present study,we investigated the roles in NPCs for an axis of candidate metastasis-related genes located at 17q11.2-q12, chemokine C-C motif ligand 2 (CCL2), and located at 3p21.31, chemokine C-C motif receptor 2 (CCR2). ELISA analyses of human serum from 50 cases with NPC and 50 cases without NPC revealed the mean serum CCL2 concentration of cases with NPC was significantly higher than cases without NPC (P<0.001).Higher expression levels of CCL2 and CCR2 were frequently detected in NPCs compared with normal nasopharyngeal epithelium samples by IHC analyses, and both ectopic expressions were significantly associated with NPC metastasis (P = 0.039, p = 0.016, respectively) and poor overall survival (P = 0.011, p = 0.004, respectively). Overexpressions of CCL2 and CCR2 were observed in human strong-metastatic NPC cell line S18 originated from CNE2 and 58F originated from SUNE1. Correspondingly, relatively lower expressions of CCL2 and CCR2 were detected in human weak-metastatic NPC cell line S26 originated from CNE2 and SUNE1 with weaker-metastatic ability compared to 58F. Functional studies demonstrated that upregulating the expressions of CCL2 and CCR2 respectively in S26 and SUNE1 could effectively promote cell migration and invasion in vitro, and enhance tumor distant metastasis in vivo of nude mice, which could be further raised in cells overexpressing CCR2 with exogenous CCL2 in the medium. When CCL2 and CCR2 were silenced by shRNAs respectively in S18 and 58F, decrease of cell migration and invasion was showed and significantly fewer metastases were observed. However, adding exogenous CCL2 to the medium culturing CCR2-silencing cells could not rescue their weaken ability of migration and invasion and metastasis. Mechanistic investigations suggested that, dual overexpressions of CCL2/CCR2 could remarkably activate extracellular signal-regulated kinase (ERK1/2) signaling pathway, which sequentially induced matrix metalloproteinase (MMP)2/9 transcriptional activation to facilitate tumor metastasis. Taken as a whole, CCL2-CCR2 axis signaling plays a pivotal role in NPC metastasis by activating ERK1/2 pathway via upregulating MMP2 and MMP9, and this finding may help to identify novel therapeutic targets for a better clinical management of NPC.