Neochlorogenic acid enhances the antitumor effects of pingyangmycin via regulating TOP2A.

Neochlorogenic acid (NCA), a natural compound found in honeysuckle, possesses prominent anti­inflammatory and antitumor effects. Pingyangmycin (PYM) induces DNA damage and has been used for the treatment of oral and maxillofacial tumors. Oral care serves an important role in promoting wound healing during chemotherapy in patients with oral squamous cell carcinoma (OSCC). Therefore, the present study aimed to analyze the effects of NCA and PYM on OSCC cells and to investigate the potential underlying mechanism. Reverse transcription­quantitative PCR and western blotting were conducted to analyze the expression levels of DNA topoisomerase II α (TOP2A) in different OSCC cell lines. TOP2A­overexpression cells were constructed via transfection of TOP2A­overexpression plasmids. Following NCA or PYM treatment, cell proliferation was assessed using Cell Counting Kit­8 and colony formation assays, whereas cell apoptosis and the cell cycle distribution were assessed via TUNEL staining and flow cytometry, respectively. In addition, the expression levels of apoptosis­ and cell cycle­related proteins were detected via western blotting. Moreover, co­immunoprecipitation (Co­IP) was conducted to determine whether TOP2A interacted with CDK1. The results of the present study indicated that NCA treatment significantly enhanced the suppressive effects of PYM on OSCC cell proliferation and apoptosis. The results also indicated that PYM arrested the cell cycle in the G0/1 by regulating cyclin dependent kinase 1 (CDK1)/cyclin B1, which was enhanced by the cotreatment of NCA and PYM. In addition, NCA and PYA treatment altered the expression levels of apoptosis­related proteins. The Co­IP assay indicated that TOP2A interacted with CDK1. Moreover, TOP2A overexpression significantly reversed the effects of NCA and PYM treatment on OSCC cell proliferation and apoptosis. In addition, NCA significantly decreased PYM­induced toxicity in normal oral epithelial cells. In conclusion, the results of the present study suggested that NCA may promote the inhibitory effects of PYM in OSCC via TOP2A.