Discovered in nematodes in 1993 [see RNA silencing], microRNAs (19 to 25 nucleotide-long regulatory noncoding RNAs derived from fold-back hairpin precursors) 1 have since then, been shown to be important regulators of gene expression, controlling a wide array of biological processes, including differentiation, proliferation, and apoptosis.It has been reported that alterations in miRNA expression are involved in the initiation, progression, and metastasis of human tumors.
Indeed, depending on their targets, there are, in principle, several possible mechanisms through which miRNAs could affect tumorigenesis2.
For example, genetic alterations (in tumors) that lead to overexpression, amplification, or to changes in the silencing chromatin structure of a gene encoding an miRNA that targets one or more tumor suppressor genes, could inhibit an anti-oncogenic pathway. On the other hand, disruption (or silencing) of a gene encoding a miRNA that normally represses the expression of an oncogene, could lead to enhanced oncogeny3. This is of course, an oversimplification: the functional consequences of altered patterns of miRNA expression are just beginning to be understood and may not be as straightforward as this.
The latest Snapshot from Cell is entitled: MicroRNAs in Cancer, and lists several miRNAs that are deregulated in certain types of cancer, their molecular mechanisms, targets and their use in diagnosis.
While on the matter, let me also direct your attention to a Web Focus on MicroRNAs and Cancer (although it was freely available only until last September), which includes "original Research and Review articles, as well as Research Highlights from Nature Genetics, Nature Reviews Genetics and Nature Reviews Cancer".
Indeed, depending on their targets, there are, in principle, several possible mechanisms through which miRNAs could affect tumorigenesis2.
For example, genetic alterations (in tumors) that lead to overexpression, amplification, or to changes in the silencing chromatin structure of a gene encoding an miRNA that targets one or more tumor suppressor genes, could inhibit an anti-oncogenic pathway. On the other hand, disruption (or silencing) of a gene encoding a miRNA that normally represses the expression of an oncogene, could lead to enhanced oncogeny3. This is of course, an oversimplification: the functional consequences of altered patterns of miRNA expression are just beginning to be understood and may not be as straightforward as this.
The latest Snapshot from Cell is entitled: MicroRNAs in Cancer, and lists several miRNAs that are deregulated in certain types of cancer, their molecular mechanisms, targets and their use in diagnosis.
While on the matter, let me also direct your attention to a Web Focus on MicroRNAs and Cancer (although it was freely available only until last September), which includes "original Research and Review articles, as well as Research Highlights from Nature Genetics, Nature Reviews Genetics and Nature Reviews Cancer".
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1 I won myself a drink for giving the shortest definition I know.
2 Esquela-Kerscher A, Slack FJ (2006) Oncomirs - microRNAs with a role in cancer. Nat Rev Cancer. 2006 Apr;6(4):259-69.
3 Ventura A, Jacks T (2009) MicroRNAs and cancer: short RNAs go a long way. Cell. 2009 Feb 20;136(4):586-91.
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