Flavokawain C Inhibits Cell Cycle and Promotes Apoptosis, Associated with Endoplasmic Reticulum Stress and Regulation of MAPKs and Akt Signaling Pathways in HCT 116 Human Colon Carcinoma Cells

PLoS One. 2016 Feb 9;11(2):e0148775. doi: 10.1371/journal.pone.0148775. eCollection 2016.

Abstract

Flavokawain C (FKC) is a naturally occurring chalcone which can be found in Kava (Piper methysticum Forst) root. The present study evaluated the effect of FKC on the growth of various human cancer cell lines and the underlying associated mechanisms. FKC showed higher cytotoxic activity against HCT 116 cells in a time- and dose-dependent manner in comparison to other cell lines (MCF-7, HT-29, A549 and CaSki), with minimal toxicity on normal human colon cells. The apoptosis-inducing capability of FKC on HCT 116 cells was evidenced by cell shrinkage, chromatin condensation, DNA fragmentation and increased phosphatidylserine externalization. FKC was found to disrupt mitochondrial membrane potential, resulting in the release of Smac/DIABLO, AIF and cytochrome c into the cytoplasm. Our results also revealed that FKC induced intrinsic and extrinsic apoptosis via upregulation of the levels of pro-apoptotic proteins (Bak) and death receptors (DR5), while downregulation of the levels of anti-apoptotic proteins (XIAP, cIAP-1, c-FlipL, Bcl-xL and survivin), resulting in the activation of caspase-3, -8 and -9 and cleavage of poly(ADP-ribose) polymerase (PARP). FKC was also found to cause endoplasmic reticulum (ER) stress, as suggested by the elevation of GADD153 protein after FKC treatment. After the cells were exposed to FKC (60μM) over 18hrs, there was a substantial increase in the phosphorylation of ERK 1/2. The expression of phosphorylated Akt was also reduced. FKC also caused cell cycle arrest in the S phase in HCT 116 cells in a time- and dose-dependent manner and with accumulation of cells in the sub-G1 phase. This was accompanied by the downregulation of cyclin-dependent kinases (CDK2 and CDK4), consistent with the upregulation of CDK inhibitors (p21Cip1 and p27Kip1), and hypophosphorylation of Rb.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents, Phytogenic / chemistry
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Apoptosis / drug effects*
  • Caspases / metabolism
  • Cell Cycle / drug effects*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Chalcones / chemistry
  • Chalcones / pharmacology*
  • Colonic Neoplasms / drug therapy*
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • DNA Fragmentation / drug effects
  • Endoplasmic Reticulum Stress / drug effects
  • Enzyme Activation / drug effects
  • HCT116 Cells
  • HT29 Cells
  • Humans
  • MAP Kinase Signaling System / drug effects
  • MCF-7 Cells
  • Membrane Potential, Mitochondrial / drug effects
  • Phosphatidylserines / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Receptors, Death Domain / metabolism
  • Signal Transduction / drug effects

Substances

  • Antineoplastic Agents, Phytogenic
  • Chalcones
  • Phosphatidylserines
  • Receptors, Death Domain
  • flavokawain C
  • Proto-Oncogene Proteins c-akt
  • Caspases

Grant support

This research is supported by High Impact Research MoE Grant UM.C/625/1/HIR/MoE/SC/02 from the Ministry of Education Malaysia. This grant was awarded to SNAM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.