They are short, single-stranded, non-coding RNA sequences that regulate gene/protein expression and play critical roles in many key cellular functions.



The X chromosome is highly enriched in miRNA coding sequences with 111 different known miRNAs, about 6% of all known miRNAs compared with only four miRNAs noted on the Y chromosome.



Range from 18-25 nucleotides.

Noncoding RNA molecules that regulate the translation of many genes.

Expressed in a tissue and development specific manner.

Transcribed as long primary transcripts which fold back to form double stranded structures.

Often clustered.

Can arise from intergenic or intragenic genomic regions.

Regulate cellular processes of apoptosis, proliferation and differentiation of cells.

Approximately 50% of human MicroRNAs located at cancer associated regions of the genome indicating a role in the pathogenesis of human malignancies.

CLL cells, CD5+B cells, have a distinct pattern of expression of microRNA that differs from that of normal CD5+ B cells.

Related to the prognosis in CLL, neuroblastomas, lung and pancreatic cancer.

miR-155 is a microRNA that is dysregulated in the aggressive lymphomas, in aggressive forms of CLL and in some solid malignancies such as lung, breast, and colorectal cancers.

miR-155 inhibits expression of tumor suppressors and genes involved in DNA repair.

miR-155 Is an independent prognostic factor in patients with cytogegenetically normal AML.

Higher miR-155 expression has a negative impact on the outcome of younger and older patients and is associated with a lower complete response rate and shorter disease-free survival and overall survival in younger patients with AML.

Higher miR-155 expression is associated with lower complete remission rate and shorter overall survival in older patients with AML.

Micro RNA-155 is a biomarker for CLL and it’s increased expression is correlated with poor survival and therapeutic response.

High mir-21 expression in colon cancer associated with poor survival and poor treatment outcome.

Regulate smoking induced gene expression changes in airway epithelium.

Are biomarkers for cancer diagnosis and prognosis.

Expression of microRNA 26a and 26b in non-tumor hepatic tissues is higher from women than men.

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