Suppression of A549 cell proliferation and metastasis by calycosin via inhibition of the PKC-/ERK1/2 pathway: An in vitro investigation

The migration and invasion of lung cancer cells into the extracellular matrix contributes to the high mortality rates of lung cancer. The protein kinase C (PKC) and downstream signaling pathways are important in the invasion and migration of lung cancer cells. Calycosin (Cal), an effector chemical from Astragalus has been reported to affect the recurrence and metastasis of cancer cells via the regulation of the protein expression of matrix metalloproteinases (MMPs). The inhibition of Cal on the migration and invasion of A549 cells was investigated in the present study. Cell viability and apoptosis assays were performed using MTT and flow cytometric analyses. A wound healing assay and Transwell invasion assay were performed to evaluate the effect of Cal on A549 cell migration and invasion. Invasion-associated proteins, including MMP-2, MMP-9, E-cadherin (E-cad), integrin 1, PKC- and extracellular signal-regulated kinase 1/2 (ERK1/2) were detected using western blotting. In addition, PKC- inhibitor, AEB071, and ERK1/2 inhibitor, PD98059, were used to determine the association between the suppression of PKC-/ERK1/2 and invasion, MMP-2, MMP-9, E-cad and integrin 1. Cal was observed to suppress cell proliferation and induce apoptosis. There were significant differences between the phorbol-12-myristate-13-acetate (TPA)-induced A549 cells treated with Cal and the untreated cells in the rates of migration and invasion. The levels of MMP-2, MMP-9, E-cad and integrin 1 in the TPA-induced A549 cells changed markedly, compared with the untreated cells. In addition, the suppression of Cal was affected by the PKC inhibitor, AEB071, an ERK1/2 inhibitor, PD98059. The results of the present study indicated that Cal inhibited the proliferation, adhesion, migration and invasion of the TPA-induced A549 cells. The Cal-induced repression of PKC-/ERK1/2, increased the expression of E-Cad and inhibited the expression levels of MMP-2, MMP-9 and integrin 1, which possibly demonstrates the mechanism underlying the biological anticancer effects of Cal.