A second-generation microRNA-based assay for diagnosing tumor tissue origin.

10575 Background: Cancer of unknown primary (CUP) constitutes 3%-5% of all newly diagnosed cancer cases. It presents a major diagnostic challenge as knowing the tumor tissue of origin (ToO) of the cancer is crucial for choosing the optimal treatment. MicroRNAs are a family of non-coding, regulatory RNA genes involved in development and differentiation that were shown to be involved in carcinogenesis. MicroRNAs, highly stable in clinical samples and tissue-specific, serve as ideal biomarkers for cancer diagnosis. Our first generation assay identifies the ToO using a set of 48 microRNAs measured on a qRT-PCR platform and differentiates 25 different tumor types. We present here the development and validation of a second generation clinical assay that can identify 42 different tumor types using a custom array platform. Methods: Over 1300 primary and metastatic tumor formalin-fixed and paraffin-embedded (FFPE) tissue samples were used for the training and development of the assay. High-purity RNA was extracted...