A composition of ursolic acid derivatives from Ludwigia hyssopifolia induces apoptosis in throat cancer cells via the Akt/mTOR and mitochondrial signaling pathways and by modulating endoplasmic reticulum stress

Abstract

Ethnopharmacological relevance: Ludwigia hyssopifolia (LH), an ethnopharmacological herb used in Guangxi Zhuang medicine, is known for its extensive therapeutic use in treating throat disorders. The anti-laryngeal-cancer benefits of the ethyl acetate and petroleum ether fractions of the ethanolic extracts of LH have been shown in our prior cell-based research. Nevertheless, the specific impacts and underlying processes by which LH combats throat cancer effects have not been fully understood.

Aim of the study: This study involved the extraction of a composition containing two derivatives of ursolic acid from LH (LH-CUAD). The present study aimed to assess the anti-throat-cancer effects of these derivatives and the underlying mechanisms through in vitro and in vivo experiments.

Materials and methods: Solvent extraction, fractionation, chromatography, and semipreparative high-performance liquid chromatography were used for the extraction, purification, and analysis of LH-CUAD. The in vitro and in vivo anti-throat-cancer effects of LH-CUAD were investigated using the throat cancer cell lines Hep-2 and FaDu as well as Hep-2 tumor-bearing nude mice.

Results: LH-CUAD significantly inhibited the proliferation and migration of throat cancer cells without any prominent toxicity. The Hoechst 33258 staining, Annexin V-FITC/PI double-staining assays, and flow cytometry confirmed that LH-CUAD could induce throat cancer cell death from early to late apoptosis in vitro. LH-CUAD exhibited significant antitumor activity and low toxicity in a xenograft model, and induced throat cancer cells apoptosis in vivo. The apoptotic effects of LH-CUAD therapy were validated using Western blotting, which demonstrated the activation of a caspase cascade response triggered by an imbalance between the endoplasmic reticulum and mitochondria. In addition, it was observed that LH-CUAD exhibited inhibitory effects on Akt and mTOR phosphorylation, hence promoting apoptosis.

Conclusions: LH-CUAD induces apoptosis in both in vivo and in vitro models of throat cancer. This effect is achieved by activating the mitochondrial pathway, inhibiting the Akt/mTOR pathway and initiating endoplasmic reticulum stress. The findings of this study suggest that LH-CUAD has the potential to offer a novel approach to the clinical management of throat cancer.

Keywords: Akt; Endoplasmic reticulum stress; Ludwigia hyssopifolia; Mitochondrial apoptosis; Throat cancer; mTOR.