Magnolol inhibits cancer stemness and IL-6/Stat3 signaling in oral carcinomas

Background/purpose: Cancer stem cells (CSCs) have been known to be implicated in tumorigenesis, metastasis, and drug resistance in oral squamous cell carcinomas (OSCC). In this study, we aimed to investigate whether magnolol, a polyphenolic component derived from Magnolia officinalis, exhibited the anti-CSCs properties. Methods: The cytotoxicity of magnolol was tested using normal gingival epithelioid SG cells and sphere-forming OSCC-CSCs isolated from SAS, OECM1, and GNM cells. Secondary sphere-forming ability, the proportion of ALDH1 positive cells, Transwell migration, and invasion capacities were examined as well. The chemosensitive effects of magnolol were investigated using MTT, secondary sphere-forming, and invasion assays. Results: Magnolol exerted a higher cytotoxicity of OSCC-CSCs and cancer stemness features, including self-renewal ability, the expression CSC marker, migration, and invasion capacities were all downregulated in magnolol-treated OSCC-CSCs. Moreover, administration of magnolol potentiated the effect of cisplatin, including a decrease in cell viability, self-renewal, and invasion activities. In addition, we observed that the secretion of IL-6 and phosphorylation of Stat3 were decreased in OSCC-CSCs treated with magnolol. Conclusion: Our data suggest that magnolol is able to target CSCs and suppress the cancer stemness properties, at least in part, via IL-6/Stat3 signaling. Besides, a dietary supplement of magnolol may function as an adjunct to cisplatin treatment.