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Sustained ERK [corrected] inhibition by EGFR targeting therapies is a predictive factor for synergistic cytotoxicity

Anette Weyergang1, Pål K Selbo, Kristian Berg

  • 1Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital Montebello, N-0310 Oslo, Norway. anette.weyergang@rr-research.no

Biochimica Et Biophysica Acta
|May 15, 2013
PubMed
Abstract

Insights

Combining photodynamic therapy (PDT) with epidermal growth factor receptor (EGFR) inhibitors shows promise. Sustained ERK inhibition predicts synergistic cytotoxicity, guiding selection of adjuvant therapies for cancer treatment.

Area of Science:

  • Oncology
  • Biochemistry
  • Photomedicine

Background:

  • Epidermal growth factor receptor (EGFR) targeting therapies, including tyrosine kinase inhibitors (TKIs) and monoclonal antibodies, face limitations due to drug resistance.
  • Adjuvant therapies are crucial for enhancing the efficacy of EGFR-targeted treatments.

Purpose of the Study:

  • To investigate the synergistic effects of combining photodynamic therapy (PDT) with EGFR inhibitors.
  • To identify predictive factors for successful combination therapies.

Main Methods:

  • Three EGFR inhibitors (Cetuximab, Erlotinib, Tyrphostin AG1478) were combined with PDT using TPPS(2a) photosensitizer.
  • Experiments were conducted on EGFR-positive A-431 (skin carcinoma) and WiDr (colorectal adenocarcinoma) cell lines.
  • Cytotoxicity was assessed via cell counting and MTT assays; cellular signaling was analyzed by Western blotting.

Main Results:

  • Neoadjuvant PDT with Tyrphostin in A-431 cells and with Tyrphostin or Erlotinib in WiDr cells demonstrated synergistic cytotoxicity.
  • Conversely, Erlotinib or Cetuximab combined with neoadjuvant PDT showed antagonistic effects in A-431 cells.
  • Synergistic cytotoxicity and ERK inhibition occurred only when EGFR inhibitors induced prolonged ERK inhibition, not correlating with EGFR inhibition levels.

Conclusions:

  • Sustained ERK inhibition by EGFR inhibitors is a predictive biomarker for synergistic cytotoxicity when combined with neoadjuvant PDT.
  • This study provides a basis for selecting anticancer drugs that may benefit from PDT as an adjuvant therapy.

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