Combined oridonin with cetuximab treatment shows synergistic anticancer effects on laryngeal squamous cell carcinoma: involvement of inhibition of EGFR and activation of reactive oxygen species-mediated JNK pathway

Int J Oncol. 2016 Nov;49(5):2075-2087. doi: 10.3892/ijo.2016.3696. Epub 2016 Sep 19.

Abstract

Epidermal growth factor receptor (EGFR), a transmembrane glycoprotein, is expressed at high levels in a large proportion of laryngeal squamous cell carcinoma (LSCC). Cetuximab (Cet), an anti-EGFR monoclonal antibody, has limited clinical outcome for patients with head and neck squamous cell carcinoma. Our previous studies showed that oridonin (ORI), a natural and safe kaurene diterpenoid isolated from Rabdosia rubescens, inhibited cell growth in HEp-2 cells through inhibition of EGFR phosphorylation. The aim of the present study was to determine whether ORI could improve the anticancer efficacy of Cet on LSCC. We observed that the combination with Cet and ORI synergistically inhibited cell growth associated with Fas-mediated apoptosis and G2/M phase arrest in two LSCC cell lines (HEp-2 and Tu212 cells). Moreover, combination treatment caused cell death associated with suppression of p-EGFR and activation of reactive oxygen species (ROS)-mediated JNK pathway. In nude mice bearing HEp-2 xenografts, ORI plus Cet caused a significant tumor regression through induction of apoptosis and inhibition of proliferation with no side-effect. Together, our findings suggest that the combination of ORI and Cet has the potential to enhance tumor responses and may significantly improve therapeutic outcomes in LSCC.

MeSH terms

  • Animals
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Apoptosis / drug effects
  • Blotting, Western
  • Carcinoma, Squamous Cell / drug therapy
  • Carcinoma, Squamous Cell / metabolism
  • Carcinoma, Squamous Cell / pathology*
  • Cell Proliferation / drug effects
  • Cetuximab / administration & dosage
  • Diterpenes, Kaurane / administration & dosage
  • Drug Synergism*
  • ErbB Receptors / antagonists & inhibitors*
  • ErbB Receptors / metabolism
  • Female
  • Flow Cytometry
  • Humans
  • Immunoenzyme Techniques
  • Laryngeal Neoplasms / drug therapy
  • Laryngeal Neoplasms / metabolism
  • Laryngeal Neoplasms / pathology*
  • MAP Kinase Kinase 4 / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Fluorescence
  • Reactive Oxygen Species / metabolism*
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays

Substances

  • Diterpenes, Kaurane
  • Reactive Oxygen Species
  • oridonin
  • EGFR protein, human
  • ErbB Receptors
  • MAP Kinase Kinase 4
  • Cetuximab