Current knowledge of miRNAs as biomarkers in breast cancer
Breast cancer (BC) is the most common malignancy in women worldwide.
Breast cancer related mortality has dropped significantly since the widespread
adoption of mammographic screening. Approximately, 5% of the patients with BC
carry germline mutations that are responsible for their condition. Women carrying a
BRCA 1 or 2 mutation have a 57% and 49% lifetime risk of developing breast cancer,
respectively. For BRCA1/2 patients reluctant to a prophylactic surgery, the only
risk reducing strategy remains an increased imaging and clinical surveillance.
Whereas a closer screening mammogram program is helpful in detecting BC at an
earlier stage, no laboratory markers exist. New markers would be helpful in identifying
BC, once the mutations are identified, and in monitoring the cancer behavior
and response to treatment, once the cancer is diagnosed. MicroRNAs (miRNAs) are key regulatory molecules operating in a post-transcriptional level by regulating
gene expression. Aberrant miRNA expression was documented in several pathological
conditions, including solid tumors, suggesting their involvement in tumorigenesis.
MiRNAs can be detected in human fluids and could be used as biomarkers.
A different pattern expression of miRNA in biological fluids of BC patients as compared
to healthy control is currently under consideration in many clinical trials. The
biologic mechanism of miRNAs, a rationale of its use as biomarker in cancer, and a
literature review of the most significant results achieved about miRNAS in BC will
be reported and discussed in this chapter.