Phosphoproteomics identify arachidonic-acid-regulated signal transduction pathways modulating macrophage functions with implications for ovarian cancer

Theranostics. 2021 Jan 1;11(3):1377-1395. doi: 10.7150/thno.52442. eCollection 2021.


Arachidonic acid (AA) is a polyunsaturated fatty acid present at high concentrations in the ovarian cancer (OC) microenvironment and associated with a poor clinical outcome. In the present study, we have unraveled a potential link between AA and macrophage functions. Methods: AA-triggered signal transduction was studied in primary monocyte-derived macrophages (MDMs) by phosphoproteomics, transcriptional profiling, measurement of intracellular Ca2+ accumulation and reactive oxygen species production in conjunction with bioinformatic analyses. Functional effects were investigated by actin filament staining, quantification of macropinocytosis and analysis of extracellular vesicle release. Results: We identified the ASK1 - p38δ/α (MAPK13/14) axis as a central constituent of signal transduction pathways triggered by non-metabolized AA. This pathway was induced by the Ca2+-triggered activation of calmodulin kinase II, and to a minor extent by ROS generation in a subset of donors. Activated p38 in turn was linked to a transcriptional stress response associated with a poor relapse-free survival. Consistent with the phosphorylation of the p38 substrate HSP27 and the (de)phosphorylation of multiple regulators of Rho family GTPases, AA impaired actin filament organization and inhibited actin-driven macropinocytosis. AA also affected the phosphorylation of proteins regulating vesicle biogenesis, and consistently, AA enhanced the release of tetraspanin-containing exosome-like vesicles. Finally, we identified phospholipase A2 group 2A (PLA2G2A) as the clinically most relevant enzyme producing extracellular AA, providing further potentially theranostic options. Conclusion: Our results suggest that AA contributes to an unfavorable clinical outcome of OC by impacting the phenotype of tumor-associated macrophages. Besides critical AA-regulated signal transduction proteins identified in the present study, PLA2G2A might represent a potential prognostic tool and therapeutic target to interfere with OC progression.

Keywords: arachidonic acid; macropinocytosis; ovarian cancer; phosphoproteomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arachidonic Acid / pharmacology*
  • Calcium / metabolism
  • Extracellular Vesicles / drug effects
  • Extracellular Vesicles / metabolism
  • Female
  • Group II Phospholipases A2 / metabolism
  • Humans
  • Macrophages / drug effects*
  • Neoplasm Recurrence, Local / drug therapy
  • Neoplasm Recurrence, Local / metabolism
  • Ovarian Neoplasms / drug therapy*
  • Ovarian Neoplasms / metabolism
  • Phosphorylation / drug effects*
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects*
  • Transcription, Genetic / drug effects
  • Tumor Microenvironment / drug effects


  • Reactive Oxygen Species
  • Arachidonic Acid
  • Group II Phospholipases A2
  • Calcium