Endoplasmic reticulum stress-induced apoptotic pathway and mitochondrial dysregulation in HeLa cells treated with dichloromethane extract of Dillenia suffruticosa

Induction of Apoptosis and Cell Cycle Arrest by Flavokawain C on HT-29 Human Colon Adenocarcinoma via Enhancement of Reactive Oxygen Species Generation, Upregulation of p21, p27, and GADD153, and Inactivation of Inhibitor of Apoptosis Proteins

Chalcones have been shown to exhibit anti-cancer properties by targeting multiple molecular pathways. It was, therefore, of interest to investigate flavokawain C (FKC), a naturally occurring chalcone, which can be isolated from Kava (Piper methysticum Forst) root extract. The aim of this study was to investigate the inhibitory effect of FKC on the growth of HT-29 cells and its underlying mechanism of action. Cell viability of HT-29 cells was assessed by Sulforhodamine B assay after FKC treatment. Induction of apoptosis was examined by established morphological and biochemical assays. ROS generation was determined by dichlorofluorescein fluorescence staining, and superoxide dismutase activity was measured using the spectrophotometric method. Western blotting was used to examine the changes in the protein levels. FKC markedly decreased the cell viability of HT-29 cells and the cells showed dramatic changes in cellular and nuclear morphologies with typical apoptotic features. The induction of apoptosis correlated well with the externalization of phosphatidylserine, DNA fragmentation, decreased mitochondrial membrane potential, activation of caspases, and PARP cleavage. This was associated with an increase in reactive oxygen species and a decrease in SOD activity. The protein levels of XIAP, c-IAP1, and c-IAP2 were downregulated, whereas the GADD153 was upregulated after FKC treatment. FKC induced cell cycle arrest at the G₁ and G₂/M phases via upregulation of p21 and p27 in a p53-independent manner. Our results provide evidence that FKC has the potential to be developed into chemotherapeutic drug for the treatment of colon adenocarcinoma.

SUMMARY

Flavokawain C inhibited the growth of HT-29 human colon adenocarcinoma cellsFlavokawain C induced apoptosis in HT-29 cells, associated with an increase in reactive oxygen species and a decrease in SOD activityFlavokawain C induced cell cycle arrest at the G₁ and G₂/M phases via upregulation of p21 and p27 in HT-29 cellsHT-29 cells treated with flavokawain C caused downregulation of XIAP, c-IAP1, and c-IAP2, and upregulation of GADD153. Abbreviations used: FKC: Flavokawain C; SRB: Sulforhodamine B; ROS: Reactive oxygen species; SOD: Superoxide dismutase; PARP: Poly(ADP-ribose) polymerase; ER: Endoplasmic reticulum; IAPs: Inhibitor of apoptosis proteins; TUNEL: Transferase dUTP nick end labeling; Annexin V-FITC: Annexin V conjugated with fluorescein isothicyanate.

Molecular mechanisms of anticancer activity of deoxyelephantopin in cancer cells

Background

Deoxyelephantopin (DOE) is a natural bioactive sesquiterpene lactone from Elephantopus scaber, a traditionally relevant herb in Chinese and Indian medicine. It has shown promising anticancer effects against a broad spectrum of cancers.

Methods

We examined the effect of DOE on growth, autophagy, apoptosis, cell cycle progression, metastasis, and various molecular signaling pathways in cancer cells, and endeavored to decipher the molecular mechanisms underlying its effect. The cytotoxicity of DOE was examined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and colony formation assays. The antimetastatic potential of DOE was identified by wound closure, as well as invasion and migration assays. The expression of mRNAs and proteins related to cytotoxicity in cancer cells induced by DOE was investigated using reverse transcription-polymerase chain reaction, flow cytometry, and Western blot analysis.

Results

DOE showed significant cytotoxicity and induced apoptosis in cancer cells. DOE promoted the autophagy of HCT 116 and K562 cells. DOE arrested cell cycle progression in the G2/M phase. DOE treatment caused activation of caspase-8, -9, -3 and -7, reactive oxygen species production, and cleavage of cleavage of poly-ADP-ribose polymerase (PARP), the markers of apoptosis. Moreover, apoptosis induction was associated with mitochondrial permeability and endoplasmic reticulum stress. Treatment of cancer cells with DOE inhibited mitogen-activated protein kinases, nuclear factor-kappa B, phosphatidylinositol 3-kinase (PI3K/Akt), and β-catenin signaling. Furthermore, treatment of DOE increased the expression of p53, phospho-Jun amino-terminal kinases (p-JNK), and p-p38 and decreased the expression of phospho-signal transducer and activator of transcription 3 (p-STAT3) and phospho-mammalian target of rapamycin (p-mTOR) in cancer cells. DOE downregulated matrix metalloproteinase (MMP-2) and MMP-9, urokinase-type plasminogen activator (uPA), and urokinase-type plasminogen activator receptor (uPAR) mRNA levels in cancer cells.

Conclusion

These findings concluded that DOE may be useful as a chemotherapeutic agent against cancer.