ABSTRACT
The fi rst ever documented discovery of the existence of miRNAs dates back to 1993, whereby researchers focusing on the development of the C. elegans nematode identifi ed the gene lin-4 which coded for the production of small non coding RNA products that affected growth at the larval stage (R.C. Lee et al. 1993). Since this ground-breaking revelation in the fi eld of miRNA discovery, there are now over 1000 differing miRNAs identifi ed in humans alone, all of which sequences are catalogued in a comprehensive, publically accessible database has known as miRBase (www. mirbase.org) (Griffi ths-Jones et al. 2008). This chapter aims at giving a brief overview regarding the processing of the mature miRNA within the cell, the molecular functions which enable it to regulate fi nely the expression of its target mRNA/s, and will also delve into the roles that miRNAs play within major cancer biology processes such as oncogenesis, tumour suppression and resistance to chemotherapeutics.
