Astrocyte elevated gene-1 regulates CCL3/CCR5-induced epithelial-to-mesenchymal transition via Erk1/2 and Akt signaling in cardiac myxoma

Abstract

In recent years, astrocyte elevated gene-1 (AEG-1) has been reported as a key mediator that is involved in the epithelial-to-mesenchymal transition (EMT) process. However, the mechanisms underlying CCL3/CCR5-AEG-1 pathway-mediated EMT in cardiac myxoma (CM) has not been well featured till now. We used immnohistochemistry and immunoblotting to assess the expression of CCR5 and AEG-1 in 30 cases of CM tissues and cells. Subsequently, cultured CM cells were treated with si-AEG-1 or si-CCR5 and then subjected to in vitro assays. We observed that CCR5 and AEG-1 proteins were highly expressed in CM tissues (73.3 and 76.7%, respectively) and closely correlated with tumor size (>5 cm). Importantly, we validated the expression of AEG-1, p-Erk1/2, p-Akt, vimentin, N-cadherin and MMP2 increased in the CM cell with CCL3 treatment in a time- and concentration-dependent manner. When CM cells were treated with si-CCR5, the expression of AEG-1, p-Erk1/2, p-Akt, vimentin, N-cadherin and MMP2 was downregulated. In addition, when CM cells were treated with si-AEG-1, the expression of p-Erk1/2, p-Akt, vimentin, N-cadherin and MMP2 was also downregulated. Using the cell cycle and proliferation assay, the knockdown of AEG-1 inhibited the entry of G1 into S phase and the proliferation capacity of CM cells. In conclusion, AEG-1 mediates CCL3/CCR5- induced EMT development via both Erk1/2 and Akt signaling pathway in CM patients, which indicates CCL3/CCR5-AEG- 1-EMT pathway could be suggested as a useful target to affect the progression of CM.