Protocatechualdehyde Induces S-Phase Arrest and Apoptosis by Stimulating the p27(KIP1)-Cyclin A/D1-CDK2 and Mitochondrial Apoptotic Pathways in HT-29 Cells

Molecules. 2016 Jul 19;21(7):934. doi: 10.3390/molecules21070934.


Protocatechualdehyde (PCA) extracted from Phellinus gilvus exhibits anti-cancer activity in human colorectal carcinoma cells (HT-29). However, the underlying mechanisms remain poorly understood. We performed an in vitro study involving MTT, flow cytometry, RT-PCR, and western blot analyses to investigate the effects of PCA treatment on cell proliferation, cell cycle distribution, apoptosis, and expression of several cell cycle-related genes in HT-29 cells. The treatment enhanced S-phase cell cycle and apoptosis in HT-29 cells in a dose-dependent manner. Western blot results showed that PCA treatment decreased the expression levels of cyclin A, cyclin D1, and p27(KIP1) but increased those of cyclin-dependent kinase 2 (CDK2) in HT-29 cells. Furthermore, the expression levels of B-cell lymphoma/leukemia-2 (Bcl-2) and B-cell lymphoma/leukemia-xL (Bcl-xL) were down-regulated, whereas the levels of BH3-interacting domain death agonist (Bid), Bcl-2 homologous antagonist/killer (Bak), and cytosolic cytochrome c were significantly upregulated. Thus, the enzymes caspases-9, -3, -8, and -6 were found to be activated in HT-29 cells with PCA treatment. These results indicate that PCA-induced S-phase cell cycle arrest and apoptosis involve p27(KIP1)-mediated activation of the cyclin-A/D1-Cdk2 signaling pathway and the mitochondrial apoptotic pathway.

Keywords: HT-29 cells; Phellinus gilvus; S-phase arrest; apoptosis; protocatechualdehyde.

MeSH terms

  • Apoptosis / drug effects*
  • Benzaldehydes / chemistry
  • Benzaldehydes / pharmacology*
  • Catechols / chemistry
  • Catechols / pharmacology*
  • Cell Proliferation / drug effects
  • Cyclin A1 / metabolism
  • Cyclin D1 / metabolism
  • Cyclin-Dependent Kinase 2 / metabolism
  • Cyclin-Dependent Kinase Inhibitor p27 / metabolism
  • HT29 Cells
  • Humans
  • Mitochondria / drug effects*
  • Mitochondria / metabolism*
  • S Phase Cell Cycle Checkpoints / drug effects*
  • Signal Transduction / drug effects*


  • Benzaldehydes
  • Catechols
  • Cyclin A1
  • Cyclin D1
  • Cyclin-Dependent Kinase Inhibitor p27
  • protocatechualdehyde
  • Cyclin-Dependent Kinase 2