Figure 2.

miRNA biogenesis and miRNAs that are distinctly different in pancreatic cancer tissues and blood. Primary miRNA (Pri-miRNA) is transcribed in the nucleus and then processed by Drosha into Pre-miRNA before export to the cytoplasm by Exportin ⁵. In the cytoplasm, the pre-miRNA, a hairpin/stem loop, is further processed by the enzyme Dicer, producing a double-stranded miRNA. One strand of the mature miRNA is then incorporated with the RISC to regulate its gene targets. There are 2 distinct regulatory mechanisms: (1) mRNA cleavage if the miRNA is perfectly matched with its targets 3’ UTR and (2) protein synthesis inhibition if the miRNA is imperfectly matched with the targets’ 3’ UTR. The targeted genes’ mRNA will be transported to P-bodies or stress granules and are thus inaccessible to the translational machinery. Some of the miRNAs found in tumor cells will, with necrosis, be released into plasma/serum or alternatively released in exosomes.