Victor Ambons The Discovery Of Mirna By Victor Elegans

Since the discovery of miRNA by Victor Ambros, the function of miRNAs in developmental timing in C. elegans, was extended to the association of miRNAs with cancer. We now know that miRNAs can act as oncogenes (oncomiRs), by inducing different mechanism such as cell proliferation, migration and invasion, tumor growth and metastasis, or act as a tumor suppressors by inhibiting cell proliferation, migration and invasion [52]. The most common molecular genetic changes in miRNA expression level or genetic abnormality, which will be discussed below have been found to be linked to numerous cancers as follows: 1) Downregulation of miRNA processing enzymes, such as a) Drosha by inducing expression of the oncogenic transcription factor c MYC or†¦show more content†¦3) Molecular genetic alterations such as a) chromosomal deletion, for example, deletion(s) in the 13q14 chromosome, which is normally lost in B cell chronic lymphocytic leukemia (B CLL), containing tumor suppressor miR 15 and miR 16 [64]. b) Chromosomal amplifications such as amplification of the 17q23.2 chromosomal region, which contains the oncogenic mir-21, deregulated in many types of cancer (breast, lung, gastric, ovarian and prostate cancers) [40] or amplification of the miR-17-92 cluster family on chromosome 13q 31.1, which is amplified in B cell lymphoma [59, 65]. 1.10 EBV The Epstein–Barr virus (EBV), a human tumor virus, was discovered by Michael Anthony Epstein, Bert Geoffrey Achong and Yvonne Barr, using biopsy material of Burkitt’s lymphoma (BL) patients in 1964 [66]. It is estimated that more than 95 % of the adult human population is seropositive for EBV infection. In the infected individual, EBV persists probably without any gene expression in CD19+ memory B-cells, where it is occasionally reactivated and shed through the oropharynx into the saliva [67]. Although the viral infection usually occurs without symptoms in the infected individual, EBV can induce tumors under certain conditions. EBV is responsible for approximately, 1.8% of cancer deaths worldwide [68-70]. 1.11 EBV latent genes and transformation