MicroRNAs in Cancer: the 22nd Hiroshima Cancer Seminar/the 4th Japanese Association for RNA Interference Joint International Symposium, 30 August 2012, Grand Prince Hotel Hiroshima.

The joint international symposium of the 22nd Hiroshima Cancer Seminar and the 4th Japanese Association for RNA Interference focused on a pivotal role of microRNAs in carcinogenesis, progression and therapy of human cancer. Mammalian immune regulator MCPIP1 (Zc3h12a) RNase acts as a novel suppressor of microRNA activity and biogenesis, suggesting the involvement of MCPIP1 in the alteration of microRNA biogenesis in tumorigenesis. Gene set enrichment analysis and functional assignment of microRNAs via enrichment analysis enable the prediction of microRNA activities from mRNA expression data by combining rank-based enrichment analysis and weighted evaluation of microRNA-mRNA interactions. MiR-124 and miR-203 function as tumor-suppressor microRNAs silenced by DNA methylation in hepatocellular carcinoma. Stella-induced DNA hypomethylation would confer the pathogenic function of DNA hypomethylation in cancer. Senescence-associated microRNA, miR-22, suppresses tumor growth and metastasis in vivo in a murine breast cancer model, and exosomal senescence-associated microRNA may affect the tumor microenvironment. The therapeutic potential of microRNAs for preventing and treating lung cancer using the Kras(LSL-G12D/+);p53(LSL-R172H/+)mouse model suggests that miR-34 may be useful in sensitizing tumors to other conventional therapeutics. MiR-1 and miR-133a cluster may function as tumor suppressors regulating novel pathways in human cancers. The down-regulation of miR-148a is implicated in invasion of gastric cancer, while high miR-21 expression in colorectal cancer is associated with poor survival. Neutral sphingomyelinase 2 regulates exosomal microRNA secretion and promotes angiogenesis within the tumor microenvironment as well as metastasis; in particular, the exosomal miR-210 secretion by neutral sphingomyelinase 2 confers the formation of the tumor vessel network.