الفهرس 
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Abstract
Breast cancer is the most commonly diagnosed cancer in women worldwide and the principal cause of cancer related mortality. In Egypt, the incidence of breast cancer ranks second after liver cancer.
MicroRNAs (miRs) are endogenous short noncoding transcripts that play important gene-regulatory roles. MiRs act as potential oncogenes (oncomiRs) or tumor suppressors (tsmiRs) and their altered expression in biological fluids was linked to the existence of many cancers, including breast cancer.
MiRs can be one of the novel strategies for cancer screening and monitoring. Therefore, there is a pressing need to further study circulating microRNAs (miRs) in order to categorize, validate and investigate their potential to serve as minimally invasive, early detection markers in early-stage breast cancer.
In the current study, plasma samples were collected from early-stage II breast cancer patients (n = 45), familial high-risk individuals (n=15), as well as healthy control individuals (n=20). A panel of five candidate miRs‟, including miR-21, miR-155, miR-10b, let-7c and miR-145 were selected and their expression levels were measured by using RT-qPCR technique. The plasma expression of the
Summary
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miR-21 and miR-10b were significantly increased in breast cancer patients (familial and sporadic) and high-risk individuals, while miR-155 was significantly decreased in breast cancer patients and high-risk individuals, and let7c was significantly decreased in BC patients, compared to the control group. The significant increased miR-21 and miR- 10b, along with the significant down-regulation in miR-155 expressions in high-risk subjects (those with a positive family history) had the importance of using these biomarkers to further predict which individuals require extreme follow up than others. Also, both miR-21 and miR-10b have the highest diagnostic accuracy to distinguish breast cancer patients or high-risk individuals from healthy controls. Also, high-risk individuals harbor classical mutations in BRCA1 and 2 genes, considering a high priority for these individuals to have had strict follow- up.