Identification of novel candidate biomarkers of epithelial ovarian cancer by profiling the secretomes of three-dimensional genetic models of ovarian carcinogenesis

Epithelial ovarian cancer (EOC) is still considered the most lethal gynecological malignancy and improved early detection of ovarian cancer is crucial to improving patient prognoses. To address this need, we tested whether candidate EOC biomarkers can be identified using three-dimensional (3D) in vitro models. We quantified changes in the abundance of secreted proteins in a 3D genetic model of early-stage EOC, generated by expressing CMYC and KRAS^G12V in TERT-immortalized normal ovarian epithelial cells. Cellular proteins were labeled in live cells using stable isotopic amino acid analogues, and secreted proteins identified and quantified using liquid chromatography-tandem mass spectrometry. Thirty-seven and 55 proteins were differentially expressed by CMYC and CMYC+KRAS^G12V expressing cells respectively (p-‰<-‰0.05; >2-fold). We evaluated expression of the top candidate biomarkers in â210 primary EOCs: CHI3L1 and FKBP4 are both expressed by >96% of primary EOCs, and FASN and API5 are expressed by 86 and 75% of cases. High expression of CHI3L1 and FKBP4 was associated with worse patient survival (p-‰=-‰0.042 and p-‰=-‰0.002, respectively). Expression of LGALS3BP was positively associated with recurrence (p-‰=-‰0.0001) and suboptimal debulking (p-‰=-‰0.018) suggesting that these proteins may be novel prognostic biomarkers. Furthermore, within early stage tumours (I/II), high expression of API5, CHI3L1 and FASN was associated with high tumour grade (p-‰=-‰3 × 10^-4, p-‰=-‰0.016, p-‰=-‰0.010, respectively). We show in vitro cell biology models of early-stage cancer development can be used to identify novel candidate biomarkers for disease, and report the identification of proteins that represent novel potential candidate diagnostic and prognostic biomarkers for this highly lethal disease. What's new? Early detection of epithelial ovarian cancer (EOC) remains a substantial clinical challenge. The authors built a 3D in vitro model of early stage EOC by expressing known oncogenes in immortalized primary ovarian epithelial cells. They then quantified changes in abundance of secreted proteins using mass spectrometry at the earliest stages of neoplastic transformation. Candidate biomarkers were followed in >200 primary EOCs, and three (API5, CHI3L1, FASN) were associated with high tumor grade in early-stage EOCs, validating the in vitro approach to in vivo biomarkers for this deadly cancer.