Secretory phospholipase A2-IIa upregulates HER/HER2-elicited signaling in lung cancer cells

Int J Oncol. 2014 Sep;45(3):978-84. doi: 10.3892/ijo.2014.2486. Epub 2014 Jun 10.

Abstract

Lung cancer is the leading cause of cancer death worldwide. There is an urgent need for early diagnostic tools and novel therapies in order to increase lung cancer survival. Secretory phospholipase A2 group IIa (sPLA2-IIa) is involved in inflammation, tumorigenesis and metastasis. We were the first to uncover that cancer cells secrete sPLA2‑IIa. sPLA2‑IIa is overexpressed in almost all specimens of human lung cancers examined and is significantly elevated in the plasma of lung cancer patients. High levels of plasma sPLA2-IIa are significantly associated with advanced stage and decreased overall cancer survival. In this study, we further showed that elevated HER/HER2‑PI3K-Akt-NF-κB signaling contributes to sPLA2-IIa overexpression in lung cancer cells. sPLA2-IIa in turn phosphorylates and activates HER2 and HER3 in a time- and dose‑dependent manner in lung cancer cells. The structure and sequence‑based docking analysis revealed that sPLA2-IIa β hairpin shares structural similarity with the corresponding EGF hairpin. sPLA2-IIa forms an extensive interface with EGFR and brings the two lobes of EGFR into an active conformation. sPLA2-IIa also enhances the NF-κB promoter activity. Anti-sPLA2-IIa antibody, but not the small molecule sPLA2-IIa inhibitor LY315920, significantly inhibits sPLA2‑IIa-induced activation of NF-κB promoter. Our findings support the notion that sPLA2-IIa functions as a ligand for the EGFR family of receptors leading to an elevated HER/HER2-elicited signaling. Plasma sPLA2-IIa can potentially serve as lung cancer biomarker and sPLA2‑IIa is a potential therapeutic target against lung cancer.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenocarcinoma, Bronchiolo-Alveolar / metabolism*
  • Adenocarcinoma, Bronchiolo-Alveolar / pathology
  • Biomarkers, Tumor / blood
  • Cell Line
  • Gene Expression Regulation, Neoplastic
  • Group II Phospholipases A2 / chemistry
  • Group II Phospholipases A2 / metabolism*
  • Humans
  • Lung Neoplasms / metabolism*
  • Lung Neoplasms / pathology
  • Molecular Docking Simulation
  • NF-kappaB-Inducing Kinase
  • Neuregulin-1 / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein Conformation
  • Protein Serine-Threonine Kinases / genetics
  • Protein Structure, Tertiary
  • Receptor, ErbB-2 / metabolism
  • Signal Transduction*

Substances

  • Biomarkers, Tumor
  • NRG1 protein, human
  • Neuregulin-1
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • Protein Serine-Threonine Kinases
  • Group II Phospholipases A2
  • PLA2G2A protein, human