Z-Ligustilide Induces c-Myc-Dependent Apoptosis via Activation of ER-Stress Signaling in Hypoxic Oral Cancer Cells.

Z-ligustilide (or ligustilide) is found in Angelica sinensis (Oliv.) Diels and may exert potential benefits in cancer treatment. Previous research has reported that ligustilide has anti-cancer effects on several types of cancer cells. However, studies of ligustilide on oral cancer cells have not been reported, especially under hypoxic conditions. This study focuses on the molecular mechanism of ligustilide-induced apoptosis in hypoxic oral cancer cells. We found that in hypoxic TW2.6 cells, ligustilide inhibited cell migration and induced caspase-dependent apoptosis. Accumulation of c-Myc accompanied by BH3-only members suggests that ligustilide may induce c-Myc-dependent apoptosis. In addition, we reported that ligustilide has an effect on ER-stress signaling. By using inhibitors of c-Myc, IRE1α, and ER-stress inhibitors, we found that cell morphologies or cell viability were rescued to some degree. Moreover, ligustilide is able to increase the expression of γ-H2AX and enhance the occurrence of DNA damage in oral cancer cells after radiation treatment. This result suggests that ligustilide has potential as a radiation sensitizer. Altogether, we propose that ligustilide may induce c-Myc-dependent apoptosis via ER-stress signaling in hypoxic oral cancer cells.

Osthole Exerts Inhibitory Effects on Hypoxic Colon Cancer Cells via EIF2[Formula: see text] Phosphorylation-mediated Apoptosis and Regulation of HIF-1[Formula: see text].

Hypoxic microenvironment and dysregulated endoplasmic reticulum stress/unfolded protein response (UPR) system are considered important factors that promote cancer progression. Although osthole extracted from Cnidium monnieri(Fructus Cnidii) has been confirmed to exhibit an anticancer activity in various cancers, the effects of osthole in hypoxic colon cancer cells have not been explored. Therefore, the aim of this study was to examine whether osthole has an inhibitory effect on hypoxic colon cancer HCT116 cells and further investigate the underlying molecular mechanisms. Treatment with osthole significantly attenuated the cell viability, proliferation, and migration in hypoxic HCT116 cells. Osthole also activated UPR signaling such as phospho-eukaryotic initiation factor 2 alpha (EIF2[Formula: see text]/ATF4/CHOP/DR5 cascade accompanied by upregulation of pro-apoptotic proteins. Moreover, the tubule-like formation of human umbilical vein endothelial cells, the secretion of vascular endothelial growth factor A, and the expression and activity of hypoxia-inducible factor-1[Formula: see text] (HIF-1[Formula: see text] in hypoxic HCT116 cells were markedly suppressed by osthole. However, suppressing EIF2[Formula: see text] phosphorylation with salubrinal or ISRIB markedly reversed the effects of osthole on the expressions of pro-apoptotic proteins and HIF-1[Formula: see text]. Co-treatment of hypoxic HCT116 cells with osthole greatly increased the sensitivity to cisplatin and the expressions of phospho-EIF2[Formula: see text] and cleaved caspase 3. Collectively, the inhibitory effect of osthole in hypoxic HCT116 cells may be associated with EIF2[Formula: see text] phosphorylation-mediated apoptosis and translational repression of HIF-1[Formula: see text]. Taken together, osthole may be a potential agent in the treatment of colon cancer.