729230

CCR2

Chronic inflammation has a decisive role in tumorigenesis, particularly in gastric carcinogenesis. The CC chemokine ligand 2 (CCL2), an important inflammatory cytokine, is involved in the initiation, development and progression of various types of cancer. However, the role of CCL2 in gastric cancer remains to be elucidated. The present study demonstrated that recombinant CCL2 stimulation caused no effect on the morphology, proliferation and migration of human GES-1 gastric mucosa epithelial cells, in which the protein expression of CC-chemokine receptor 2 (CCR2) was markedly low. However, the expression of CCR2 was significantly upregulated in the GES-1 cells following pretreatment with the chemical carcinogen, N-methyl-N-nitro-N'-nitrosoguanidine (MNNG), for 12 h or transformed with MNNG (MC cells). The present study used CCL2 to stimulate MNNG pretreated GES-1 cells and MC cells, and demonstrated that CCL2 clearly promoted their migration and the epithelial-mesenchymal transition (EMT). However, no effect was observed on the proliferative ability of the cells. Taken together, these findings suggested that the CCL2/CCR2 chemokine signaling may regulate the EMT in gastric epithelial cells and resulted in gastric carcinogenesis in response to the intake of the carcinogen, MNNG.

Chemokine (C-C motif) ligand 2 (CCL2) has been shown to play an important role in the regulation of tumor cell growth, metastasis and host immune response. CCL2 preferentially binds to the C-C chemokine receptor type 2 (CCR2), which is expressed in various tissues. However, the role of the CCL2/CCR2 axis in hepatocellular carcinoma (HCC) invasion and its molecular mechanisms remain unclear. The aim of this study was to elucidate this issue. The human HCC cell line MHCC-97H was treated with CCL2. Cyclopamine, a smoothened (SMO) antagonist, was used to inhibit SMO activity. CCR2 siRNA and Gli-1 siRNA were used to inhibit CCR2 and Gli-1 expression respectively. The effect of CCL2 and Hedgehog (Hh) signaling on cancer cell epithelial-mesenchymal transition (EMT) and invasion was evaluated by quantitative realtime PCR analysis, western blotting and Transwell invasion assay. Our results revealed that CCL2 induced HCC cell invasion and EMT. This effect was accompanied by the activation of Hh signaling, the upregulation of Snail and vimentin and the reduction of E-cadherin. Notably, prior silencing of CCR2 with siRNA abolished CCL2-induced Hh signaling activation, Snail and vimentin upregulation, E-cadherin reduction, as well as HCC cell invasion and EMT. Furthermore, pretreatment with cyclopamine or predepletion of Gli-1 by siRNA also eliminated the changes of Snail, vimentin and E-cadherin, and HCC invasion and EMT caused by CCL2. Collectively, our results revealed that the link between the CCL2/CCR2 axis and the Hh pathway plays an important role in HCC progression. Therefore, the CCL2/CCR2 axis may represent a promising therapeutic target to prevent HCC progression.

CC chemokine receptor type 2 (CCR2) is aberrantly expressed in a variety of tumor cells, and participates in the regulation of tumor cell progression, metastasis and immune escape. However, the mechanism of action of CCR2 in liver cancer remains unclear. In the present study, the aim was to elucidate the molecular mechanism underlying the regulation of epithelialtomesenchymal transition (EMT) by CCR2 in liver cancer cells. Initially, CCR2 expression in liver cancer tissues was measured, and the survival time of patients was analyzed by KaplanMeier analysis. In liver cancer cells, the mRNA and protein expression levels of CCR2, matrix metalloproteinase2 (MMP2), Ecadherin and vimentin were evaluated by reverse transcriptionquantitative polymerase chain reaction and western blotting. Cell viability, migration and invasion were determined by Cell Counting Kit8, wound healing and Transwell chamber assays, respectively. Additionally, the binding between CCR2 and MMP2 was identified by coimmunoprecipitation (CoIP). It was observed that CCR2 was abnormally upregulated in liver cancer tissues and significantly associated with the tumor diameter, metastasis and stage. The survival of patients with high CCR2 expression was lower compared with that of patients with low CCR2 expression. In addition, the number of cells that penetrated the transwell chamber membrane was significantly reduced following treatment with CCR2small interfering RNA (siRNA). Furthermore, CCR2 was found to participate in MMP2induced EMT, while CCR2siRNA transfection reduced the expression and activity of MMP2, and confirmed the specific binding between CCR2 and MMP2. CoIP also identified the independent interaction between endogenous proteins in HepG2 cells. These results revealed that CCR2 promotes EMT in liver cancer. Thus, CCR2 is an attractive novel target for inhibiting invasion and metastasis of liver cancer cells.