In vitro selection of RNA aptamers against CA125 tumor marker in ovarian cancer and its study by optical biosensing

The epithelial ovarian carcinomas represent approximately 90% of all types of ovarian malignant neoplasms [1], and are currently among the most difficult cancers to early diagnose due to the lack of specific signs and symptoms, coupled to the absence of reliable screening strategies. Most patients are diagnosed in the advanced stage of the disease, resulting in low overall cure rates. Ovarian cancer patients are generally treated with surgical resection and subsequent chemotherapy [2]. Although many patients initially respond well to chemotherapy, long term survival remains poor due to eventual tumor recurrence and emergence of drug- resistant disease. Overall, the five years survival rate is 45% [1]. The most widely used tumor marker for ovarian cancer is the CA125/MUC16 antigen. Measurement of serum level of this bio- marker has become a gold standard component of routine manage- ment of women with ovarian cancer [3,4]. CA125 antigen, identified for the first time in 1981 [5], is a high molecular weight glycoprotein which is raised in 90% of patients with epithelial ovar- ian cancer. Several studies have confirmed the usefulness of CA125 ! Corresponding authors. E-mail addresses: defranci@unina.it (V. De Franciscis), maria.minunni@unifi.it (M. Minunni). http://dx.doi.org/10.1016/j.ymeth.2015.10.022 1046-2023/! 2015 Elsevier Inc. All rights reserved. abstract Early identification of neoplastic diseases is essential to achieve timely therapeutic interventions and sig- nificantly reduce the mortality of patients. A well-known biomarker is the Cancer Antigen 125 (CA125) or 16 mucin (MUC 16), a glycoprotein of the human family of mucins, already used for the diagnostic and prognostic evaluation of ovarian cancer. Therefore, the detection of CA125 to now remains a promising tool in the early diagnosis of this tumor. In this paper, we describe the development of RNA aptamers that bind with high affinity the tumor antigen CA125. We performed eight cycles of selection against CA125 purified protein. The selected aptamers were cloned and sequenced and the binding properties of the most promising sequences were studied by Real Time PCR and Surface Plasmon Resonance (SPR) to eval- uate their ability in targeting CA125 protein with perspective applications in aptamer-based bioassays.