Caffeic Acid Targets AMPK Signaling and Regulates Tricarboxylic Acid Cycle Anaplerosis while Metformin Downregulates HIF-1α-Induced Glycolytic Enzymes in Human Cervical Squamous Cell Carcinoma Lines

Nutrients. 2018 Jun 28;10(7):841. doi: 10.3390/nu10070841.


The small molecules, natural antioxidant Caffeic Acid (trans-3,4-Dihydroxycinnamic acid CA) and anti-diabetic drug Metformin (Met), activate 5′-adenosine monophosphate-activated protein kinase (AMPK) and interfere with metabolic reprogramming in human cervical squamous carcinoma cells. Here, to gain more insight into the ability of CA, Met and the combination of both compounds to impair aerobic glycolysis (the “Warburg effect”) and disrupt bioenergetics of cancer cells, we employed the cervical tumor cell lines C-4I and HTB-35/SiHa. In epithelial C-4I cells derived from solid tumors, CA alleviated glutamine anaplerosis by downregulation of Glutaminase (GLS) and Malic Enzyme 1 (ME1), which resulted in the reduction of NADPH levels. CA treatment of the cells altered tricarboxylic acid (TCA) cycle supplementation with pyruvate via Pyruvate Dehydrogenase Complex (PDH), increased ROS formation and enhanced cell death. Additionally, CA and CA/Met evoked intracellular energetic stress, which was followed by activation of AMPK and the impairment of unsaturated FA de novo synthesis. In invasive HTB-35 cells, Met inhibited Hypoxia-inducible Factor 1 (HIF-1α) and suppressed the expression of the proteins involved in the “Warburg effect”, such as glucose transporters (GLUT1, GLUT3) and regulatory enzymes of glycolytic pathway Hexokinase 2 (HK2), 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 4 (PFKFB4), Pyruvate Kinase (PKM) and Lactate Dehydrogenase A (LDH). Met suppressed the expression of c-Myc, BAX and cyclin-D1 (CCND1) and evoked apoptosis in HTB-35 cells. In conclusion, both small molecules CA and Met are capable of disrupting energy homeostasis, regulating oxidative metabolism/glycolysis in cervical tumor cells in regard to specific metabolic phenotype of the cells. CA and Met may provide a promising approach in the prevention of cervical cancer progression.

Keywords: 5′-adenosine monophosphate-activated protein kinase (AMPK); Caffeic Acid; Metformin; Warburg effect; cancer metabolism; cervical cancer; metabolic reprogramming; mitochondria; polyphenols.

Publication types

  • Comparative Study

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Antinematodal Agents / pharmacology*
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Caffeic Acids / pharmacology*
  • Carcinoma, Squamous Cell / drug therapy*
  • Carcinoma, Squamous Cell / enzymology
  • Carcinoma, Squamous Cell / genetics
  • Carcinoma, Squamous Cell / pathology
  • Cell Line, Tumor
  • Citric Acid Cycle / drug effects*
  • Female
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glycolysis / drug effects*
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Lipid Metabolism / drug effects
  • Metformin / pharmacology*
  • Phenotype
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects
  • Uterine Cervical Neoplasms / drug therapy*
  • Uterine Cervical Neoplasms / enzymology
  • Uterine Cervical Neoplasms / genetics
  • Uterine Cervical Neoplasms / pathology


  • Antinematodal Agents
  • Apoptosis Regulatory Proteins
  • Caffeic Acids
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Reactive Oxygen Species
  • Metformin
  • AMP-Activated Protein Kinases
  • caffeic acid