CCL2/CCR2 Axis Promotes the Progression of Salivary Adenoid Cystic Carcinoma via Recruiting and Reprogramming the Tumor-Associated Macrophages.

Zihui Yang,Jianhua Wei,Jun Wang,Jianying Zhang,Xinjie Yang,Huan Li,Weiqi Wang,Delin Lei,Sen Jia,Kaijin Hu

doi:10.3389/fonc.2019.00231

Abstract

Objective: The present study investigated the roles and underlying mechanism of CCL2/CCR2 axis in the interactions between tumor cells and tumor-associated macrophages (TAMs) during the progression of salivary adenoid cystic carcinoma (SACC).Methods: Immunohistochemical staining and survival analysis were performed to study the correlation and clinical value of CD68, CD163, CCL2, and CCR2 expression in SACC cases. CCL2 silencing by RNA interference and CCR2 blocking by CCR2 specific antagonist (RS504393) were performed. ELISA, qRT-PCR, western blot, immunofluorescence, flow cytometry, CCK8, scratch wound healing, and transwell assays were used to explore the functional roles and possible mechanism of CCL2/CCR2 axis in the interactions between SACC cells and TAMs. The effects of targeting TAMs by blocking the CCL2/CCR2 axis were investigated in a xenograft mice model with SACC cells.Results: The high infiltration of TAMs marked by CD68 and high infiltration of M2 TAMs marked by CD163 were significantly correlated with the expression of CCL2 and CCR2 in SACC tissues. Notably, the high infiltration of TAMs and the overexpression of CCL2 were obviously associated with the clinical progression and poor prognosis of SACC. SACC cells derived CCL2 could activate its receptor CCR2 expression in TAMs in vitro. The in vitro results further indicated that the SACC cells derived CCL2 was involved in the recruitment, M2 polarization, and GDNF expression of TAMs through the CCL2/CCR2 axis. Meanwhile, TAMs derived GDNF promoted the proliferation, migration, and invasion of SACC cells through the GDNF/p-RET pathway. Treating immunodeficient mice with the CCR2 antagonist (RS504393) greatly inhibited the infiltration of TAMs and the tumorigenicity of SACC cells.Conclusion: These new findings indicated that the CCL2/CCR2 axis promoted the progression of SACC cells via recruiting and reprogramming TAMs. Targeting TAMs by blocking the CCL2/CCR2 axis might be a prospective strategy for SACC therapy.

Highlights

Salivary adenoid cystic carcinoma (SACC) is one of the most commonly diagnosed salivary gland malignancies, accounting for about 10% of all salivary gland neoplasms [1, 2]
We further investigated the roles of the CCL2/CCR2 axis in the interactions between SACC cells and tumor-associated macrophages (TAMs), and explored the underlying molecular mechanism
While blocking the CCL2/CCR2 axis by the specific CCR2 antagonist obviously reduced the recruitment and the M2 polarization of TAMs. These results indicated that SACC cells could recruit and educate TAMs via the CCL2/CCR2 axis, which contributed to the construction of the tumorpromoting environment

Summary

Introduction

Salivary adenoid cystic carcinoma (SACC) is one of the most commonly diagnosed salivary gland malignancies, accounting for about 10% of all salivary gland neoplasms [1, 2]. The typical characteristics of SACC include the recurrent growth, aggressive invasion, hematogenous metastasis, and chemotherapy refractory [2,3,4]. A better understanding of the molecular mechanism is needed to illuminate the aggressive behavior and guide the development of novel therapies for SACC. TAMs were found to accelarate the growth, invasion, and metastasis of multiple malignancies, including lung cancer, breast cancer, and the hepatocellular carcinoma [7, 10, 11]. Studying the reciprocal interactions between SACC and TAMs might provide new perspectives for the mechanism of SACC development

Methods

Results

Conclusion