Background: Since most patients with oral cancer do not benefit from current treatments, new therapeutic strategies or drugs must be developed to improve patient prognosis. Qing Yan Li Ge Tang (QYLGT), a Chinese herbal medicine, is known for its anticancer activity. This study aimed to investigate whether QYLGT has anticancer effects on human OEC-M1 oral cancer cells.
Methods: To evaluate whether QYLGT affects viability, morphology, and colony formation ability of the OEC-M1 cells, the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, morphology study, and colony formation assay were performed, respectively. Each assay was carried out in triplicate, and the whole set of experiments was performed three times independently. To investigate whether QYLGT induces apoptotic effects in OEC-M1 cells, the enzyme-linked immunosorbent (ELISA) was carried out to quantify cytokeratin 18 fragment (an apoptosis marker). Each assay was carried out in triplicate, and the whole set of experiments was performed three times independently. The immunoblotting assay was performed to detect the protein expression after QYLGT treatment. The whole set of experiments was performed two times independently.
Results: The results from the MTT and colony formation assays indicate that QYLGT inhibited the cell viability and clonogenic growth capacity of OEC-M1 cells. The morphology study shows that QYLGT increased plasma membrane blebbing in OEC-M1 clles. The results of ELISA and an immunoblotting assay show that QYLGT increased cytokeratin 18 fragment release and poly ADP-ribose polymerase cleavage (another apoptosis marker) in OEC-M1 cells. In addition, the results from immunoblotting assay show that QYLGT also activated apoptotic executor proteins, including caspase-8, caspase-9, and caspase-3, and the results of ELISA indicate that treatment with the pan-caspase inhibitor, Z-VAD-FMK, inhibited QYLGT-induced cytokeratin 18 fragment release. These results indicate that QYLGT inhibited cell viability in OEC-M1 cells and induced OEC-M1 apoptosis through caspase activation. Additionally, QYLGT-activated c-Jun N-terminal kinase, extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, and nuclear factor-kappa B (NF-κB), and the related inhibitors, including SP600125, PD184352, SB202190, and Bay11-7082, were used to confirm which signaling was involved in QYLGT-induced apoptosis. Moreover, only Bay11-7082, the NF-κB inhibitor, could suppress QYLGT-induced the release of cytokeratin 18 fragments from OEC-M1 cells.
Conclusions: QYLGT induced apoptosis in OEC-M1 cells via the NF-κB pathway.