Identification of cell membrane protein stress-induced phosphoprotein 1 as a potential ovarian cancer biomarker using aptamers selected by cell systematic evolution of ligands by exponential enrichment

ABSTRACT: In this paper, we describe the elucidation of the target of an aptamer against ovarian cancer previously obtained by cell-SELEX (SELEX = systematic evolution of ligands by exponential enrichment). The target’s identity, stress-induced phosphoprotein 1 (STIP1), was determined by mass spectrometry and validated by flow cytometry, using siRNA silencing and protein blotting. Initial oncologic studies show that the aptamer inhibits cell invasion, indicating that STIP1, which is currently under investigation as a potential biomarker for ovarian cancer, plays a critical role in this process. These results serve as an excellent example of how protein target identification of aptamers obtained by cell-SELEX can serve as a means to identify promising biomarker candidates and can promote the development of aptamers as a new drug class to block important oncological processes. Ovarian cancer is a lethal malignancy, which is typicallydiagnosed only at advanced stages, when metastasis has set in. Diagnosis at later stages significantly reduces treatment options. The identification of biomarkers that are specificall