Interaction and binding mechanism of anticancer echinacoside phenylethanoid glycoside against hepatocellular carcinoma with subdomains of human serum albumin

Abstract

A phenylethanoid glycoside known as echinacoside has demonstrated promising anticancer properties against numerous cancer cell types. However, its pharmacokinetics or anticancer mechanism has remained unclear. Herein, the interaction of the echinacoside with human serum albumin (HSA) was explored by intrinsic/extrinsic fluorescence spectroscopy, circular dichroism (CD) spectroscopy as well as molecular docking simulation. Also, the anticancer effects and possible mechanism of action of the echinacoside against hepatocellular carcinoma (HCC) cells, MHCC-97-H with high tumorgenicity and metastasis, were assessed by cell viability, flow cytometry, qRT-PCR, and western blot assays. The results showed a static quenching mechanism in the formation of echinacoside-HSA complex, one binding site on HSA for echinacoside, contribution of hydrophobic interactions (PHE157, GLU188 and PRO447), and slight conformational changes of HSA in the complex form. Cellular assays disclosed that treatment with echinacoside concentration-dependently mitigated the proliferation of MHCC97-H cells in vitro with an IC50 concentration of around 30 µM. Also, echinacoside triggered apoptosis through the regulation of caspase-3 at mRNA and protein levels. Moreover, echinacoside reduced the expression of astrocyte elevated gene-1 (AEG-1)and N-cadherin, while enhancing the expression of E-cadherin, as the main hallmarks of epithelial–mesenchymal transition (EMT) in tumorigenicity and metastasis. Therefore, these data indicated that echinacoside with a promising binding affinity with HSA in a mimicking physiological condition may inhibit the proliferation and metastatic activity of MHCC97-H cells mediated by manipulation of the AEG-1/EMT pathway.