Dual-platform affinity proteomics identifies links between the recurrence of ovarian carcinoma and proteins released into the tumor microenvironment

Theranostics. 2019 Aug 22;9(22):6601-6617. doi: 10.7150/thno.37549. eCollection 2019.


The peritoneal fluid (ascites), replete with abundant tumor-promoting factors and extracellular vesicles (EVs) reflecting the tumor secretome, plays an essential role in ovarian high-grade serous carcinoma (HGSC) metastasis and immune suppression. A comprehensive picture of mediators impacting HGSC progression is, however, not available. Methods: Proteins in ascites from HGSC patients were quantified by the aptamer-based SOMAscan affinity proteomic platform. SOMAscan data were analyzed by bioinformatic methods to reveal clinically relevant links and functional connections, and were validated using the antibody-based proximity extension assay (PEA) Olink platform. Mass spectrometry was used to identify proteins in extracellular microvesicles released by HGSC cells. Results: Consistent with the clinical features of HGSC, 779 proteins in ascites identified by SOMAscan clustered into groups associated either with metastasis and a short relapse-free survival (RFS), or with immune regulation and a favorable RFS. In total, 346 proteins were linked to OC recurrence in either direction. Reanalysis of 214 of these proteins by PEA revealed an excellent median Spearman inter-platform correlation of ρ=0.82 for the 46 positively RFS-associated proteins in both datasets. Intriguingly, many proteins strongly associated with clinical outcome were constituents of extracellular vesicles. These include proteins either linked to a poor RFS, such as HSPA1A, BCAM and DKK1, or associated with a favorable outcome, such as the protein kinase LCK. Finally, based on these data we defined two protein signatures that clearly classify short-term and long-term relapse-free survivors. Conclusion: The ascites secretome points to metastasis-promoting events and an anti-tumor response as the major determinants of the clinical outcome of HGSC. Relevant proteins include both bone fide secreted and vesicle-encapsulated polypeptides, many of which have previously not been linked to HGSC recurrence. Besides a deeper understanding of the HGSC microenvironment our data provide novel potential tools for HGSC patient stratification. Furthermore, the first large-scale inter-platform validation of SOMAscan and PEA will be invaluable for other studies using these affinity proteomics platforms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascites / metabolism
  • Ascites / pathology
  • Biomarkers, Tumor / analysis
  • Biomarkers, Tumor / metabolism
  • Blood Proteins / analysis
  • Cystadenocarcinoma, Serous / metabolism
  • Cystadenocarcinoma, Serous / mortality
  • Cystadenocarcinoma, Serous / pathology*
  • Extracellular Vesicles / metabolism
  • Extracellular Vesicles / pathology
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / mortality
  • Ovarian Neoplasms / pathology*
  • Proteomics / methods*
  • Recurrence
  • Tumor Microenvironment*


  • Biomarkers, Tumor
  • Blood Proteins