Abstract 2182: Flavokawain A and B from kava extract exhibits low toxicity and up-regulates tumor suppressor miRNAs in human osteosarcoma cells
Authors: Zhang Wendong , Morris Jonathan , Piperdi Sajida , Guo Yi , Ji Tao , Yang Rui , Roth Michael , Gill Jonathan , Geller David S. , Gorlick Richard , Jones Kevin , Zi Xiaolin , Hoang Bang H. 
Published: July 2016

Objective: Osteosarcoma (OS) is the most common primary bone malignancy with a high propensity for local invasion and distant metastasis. Flavokawain A and B (FKA and FKB) from kava extract have been reported to have significant anti-tumoral effects on human cancer cells. The consumption of kava-containing beverage has been associated with a low cancer incidence. The objective of this study is to investigate the anti-tumoral effects of flavokawains in OS. In a previous report, mice treated with high-dose FKA did not demonstrate any significant major organ toxicity. MicroRNAs (miRNA), endogenous, non-coding RNA, are associated with cell-cycle regulation, differentiation, proliferation, apoptosis, and migration. There remains a paucity of literature on the effects of flavokawains on the expression of miRNA in OS. As such, we hypothesize that flavokawains will up-regulate tumor-suppressive miRNA in OS cell lines.

Methods: Human OS cell lines from American Type Culture Collection (ATCC), patient-derived OS cell lines, human mesenchymal stem cells, human intestinal epithelial cells, and mouse bone marrow cells were cultured. Cell lines were divided into control and treatment groups with increasing doses of FKA or FKB. Cell viability was determined by MTT proliferation assays and cytotoxicity to bone marrow cells was examined by colony formation. Effects of flavokawain on intestinal cells were examined by fluorescent cytotoxicity and flow cytometry. Apoptotic assays were performed following flavokawain treatments. The expression of miRNA after FKA and FKB treatment was examined by qRT-PCR. SCID mice were injected with OS 143B cells in the tibia and treated with either vehicle control or FKA (200 mg/kg) by oral gavage.

Results: By flow cytometry, FKB increases apoptosis of OS 143B cells while sparing intestinal FHs 74 intestinal cells. Mouse bone marrow cells treated with FKB showed no significant difference in colony forming units compared to control cells. Exposure of OS cell lines to FKA or FKB resulted in a loss of cell viability in a dose-dependent manner. In all cell lines tested a dose-dependent expression of miRNA was observed after exposure to FKA or FKB. Flavokawain B induced miR-26a while FKA induced miR-26a, miR-34, and miR-203 expression in OS cell lines. Mice bearing 143B xenograft tumors treated with FKA did not exhibit weight loss compared to control animals. Animals treated with FKA sustained less lung metastasis than animals treated with vehicle control.

Conclusions: Taken together, the evidence suggests flavokawains up-regulate tumor suppressive miRNAs in OS cells. In vivo experiments suggest that FKA exerts anti-metastatic effects in OS. Given their low toxicity profile, flavokawains may be useful as a chemopreventive strategy for OS and thus warrant further investigations.

Citation Format: Wendong Zhang, Jonathan Morris, Sajida Piperdi, Yi Guo, Tao Ji, Rui Yang, Michael Roth, Jonathan Gill, David S. Geller, Richard Gorlick, Kevin Jones, Xiaolin Zi, Bang H. Hoang. Flavokawain A and B from kava extract exhibits low toxicity and up-regulates tumor suppressor miRNAs in human osteosarcoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2182.