Recent updates on the role of microRNAs in prostate cancer

Prostate cancer (PCa) is considered to be the most diagnosed cancer [1] and the second leading cause of cancer death in men older than 40 years of age in the USA [2]. The major problem of PCa is the development and acquisition of castrate resistant prostate cancer (CRPC) phenotype which eventually leads to the development of skeletal metastasis (mCRPC), at which point it becomes an incurable disease [1]. Therefore, investigations are underway to find the molecular basis of mCRPC so that novel therapeutic strategies could be devised. To that end many novel molecules are being tested and interrogated, among which microRNAs (miRNAs) are becoming an attractive area of research.The miRNAs are small, noncoding subset of RNAs which consist of about 18-22 nucleotides and bind to the 3' untranslated region of messenger RNAs (mRNAs) [3]. By this action, they cause post-transcriptional inhibition or degradation of target mRNA, depending on the degree of complementary base pairing [4-6]. The miRNAs were first discovered in 1993 while studying Caenorhabditis elegans [7]. The first miRNA discovered was lin-4. It is a small, non-coding RNA molecule that was found to play a role in the development through a negative effect on lin-14 expression [7-9]. Seven years later, in 2000, let-7, the second miRNA was discovered, again in the C. elegans [9,10]. During the past 12 years, significant advances have been made in miRNA research leading to the discovery of over 4,500 miRNAs in vertebrates, flies, worms, plants, and viruses [9,11,12] out of which more than 1,000 miRNAs have been fully characterized and the number is expected to grow in the coming years. The miRNAs are being implicated in the regulation of an increasing number of physiological processes. It is also believed now that they play an important role in the regulation of many cellular functions ranging from maintenance to differentiation and tissue development, from metabolism to cell cycle [13-16]. All of these facts leads t