More recent studies provide scope for the development of sophisticated miRNA-based

cancer therapy. Yu et al28 have reported ectopic expression of miR-96 through a synthetic miRNA precursor inhibited KRAS oncogene and the result in decreased cancer cell invasion, migration and slowed tumor growth in pancreatic cancer cells, and it provides a novel therapeutic strategy for treatment of pancreatic cancer. There exists another interesting study by Kota et al29 in the murine liver cancer HSP cancer model of hepatocellular carcinoma (HCC). Their systemic administration of miR-26a using an adeno-associated virus (AAV) effects in inhibiting cancer cell proliferation, induction of tumor-specific apoptosis, and effective protection from disease progression without

toxicity. Above suggested evidences demonstrate that miRNAs are promising agents in cancer therapy. Animal miRNAs have been shown to play pivotal role in the development and physiological processes by directing post-transcriptional regulation of genes,13 and many of these are phylogenetically conserved. Hornstein et al30 observed that miR-196 acts upstream of transcription factor Hoxb8 and developmental factor sonic hedgehog (Shh) seems to mediate the induction during limb development of chick. Number of researchers have isolated the miRNA from vertebrate nervous system and they underlined its role for miRNAs in later stages of neuronal maturation and synapse development.31 Schratt et al32 reported mTOR inhibitor out in synapto dendritic compartment of rat hippo campal neurons, brain-specific miRNA, miR-134 negatively regulates the size of dendritic spines-postsynaptic sites of excitatory synaptic transmission. During spine development miR-134 control through inhibition of translation of an mRNA encoding a protein kinase, Limk1. Bolleyn et al33 observed miRNA expression profile

of primary rat hepatocytes after 7 days treatment of 25 μM Trichostatin A (TSA), a prototype hydroxamate-based histone deacetylase inhibitor by microarray analysis. In this study, they investigated differential expression of miR-122, miR-143 and miR-379, the miRNAs could be related to the inhibitory effects of TSA on hepatocellular proliferation. Similar study of biological effects of curcumin (diferuloylmethane) on human pancreatic cells, the flavonoid alters miRNA expression in human pancreatic cells, up-regulating miRNA-22 and down-regulating miRNA-199a* analyzed by TaqMan real-time PCR.34 Recently, over 66 miRNAs have been identified in mosquito genome and miRNA expression level altered during the plasmodium infection, the potential role is controlling parasite infection in the mosquito midgut.35 Altogether, it is evident that the miRNA machinery is involved in various aspects of animal development and physiological roles. A number of researchers have found that miRNA expression levels altered upon aging.