Mechanisms involved in the cytotoxic action of Brazilian propolis and caffeic acid against HEp-2 cells and modulation of P-glycoprotein activity

J Pharm Pharmacol. 2017 Nov;69(11):1625-1633. doi: 10.1111/jphp.12789. Epub 2017 Aug 4.


Objectives: The effects of propolis and phenolic compounds (caffeic acid - Caf; dihydrocinnamic acid - Cin; p-coumaric acid - Cou) in the same quantity found in our propolis sample were investigated on human laryngeal epidermoid carcinoma (HEp-2) cells.

Methods: Cell viability, apoptosis/necrosis and cell cycle arrest, P53 and CASPASE-3 gene expression, generation of reactive oxygen species (ROS) and the ability of propolis to induce doxorubicin (DOX) efflux using a P-glycoprotein (P-gp) inhibitor (verapamil) were assayed.

Key findings: Propolis exerted a cytotoxic effect on HEp-2 cells, whereas isolated compounds had no effect on cell viability. Higher concentrations were tested and Caf induced late apoptosis or necrosis in HEp-2 cells, while propolis induced apoptosis, both probably due to ROS generation. P53 expression was downregulated by propolis but not by Caf. CASPASE-3 expression was correlated with induction of both early and late apoptosis, with both propolis and Caf alone upregulating its expression. Propolis induced cell cycle arrest at G2/M phase and Caf at S phase. Propolis but not Caf may act as a P-gp inhibitor by modulating P-gp activity and inhibiting DOX efflux.

Conclusions: Propolis exerted cytotoxic effects on HEp-2 cells, and the mechanisms are discussed, showing its potential as an antitumour drug.

Keywords: HEp-2 cells; P-glycoprotein; caffeic acid; phenolic compounds; propolis.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / drug effects
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Animals
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Apoptosis / drug effects
  • Brazil
  • Caffeic Acids / pharmacology*
  • Carcinoma, Squamous Cell / drug therapy
  • Carcinoma, Squamous Cell / pathology
  • Cell Cycle Checkpoints / drug effects
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Chlorocebus aethiops
  • Doxorubicin / pharmacology
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Laryngeal Neoplasms / drug therapy*
  • Laryngeal Neoplasms / pathology
  • Phenols / pharmacology
  • Propolis / pharmacology*
  • Reactive Oxygen Species / metabolism
  • Verapamil / pharmacology
  • Vero Cells


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents, Phytogenic
  • Caffeic Acids
  • Phenols
  • Reactive Oxygen Species
  • Doxorubicin
  • Propolis
  • Verapamil
  • caffeic acid