الفهرس 
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Abstract
Breast cancer is the second most common cancer in the world and the most frequent among women. Breast cancer can be classified according to the three immunohistochemistry (IHC) markers into four main molecular subtypes which include luminal-A, luminal-B, HER2 enriched, and basal cell-like (BCL) or triple-negative breast cancer (TNBC).
Several recent studies have shown that microRNAs could provide a potential diagnostic, prognostic and therapeutic approach for human breast cancer. The circulating forms of miRNA are increasingly recognized as a non-invasive promising biomarkers that can be used as a tool for early diagnosis and provide a new approach for breast cancer management.
The present study aimed to evaluateserum expression levels of miR-497-5p and miR-182-5p in Egyptian female patients with breast cancer and their possible association with different clinicopathological features.
The study was conducted on twenty five primary breast cancer patients in addition to twenty five healthy female volunteers as a control group. Preoperative sera samples were taken from all cases. Females receiving preoperative radio- or chemotherapy as well as those suffering from malignancies other than breast cancer were excluded.
Full clinical examination and radiological investigations were done for all cases. Histopathologically confirmed diagnosis of breast cancer including staging was also done. Immunohistochemical determination of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 (HER2) were carried out in paraffin embedded breast tissue sections. Relative quantifications of serum miR-182-5p and miR-497-5p expression levels were done using a reverse transcription - quantitative real time PCR (RT-qPCR).
The present study showed that the median serum miR-497-5p expression value was significantly lower (down-regulated) in BC casescompared to the control group. A ROC curve generated cut-off value of 0.54 for serum miR-497-5p expression level was used to discriminate BC patients from normal females with a diagnostic specificity of 88%, a sensitivity of 56% and an overall test accuracy of 68.8%. On the other hand, no statistically significant difference was noted in serum miR-182-5p expression level between BC cases and control group. Nevertheless, its serum expression level was significantly up-regulated in cases with nodal involvement compared to cases without nodal involvement.
In conclusion, the significantly down-regulated serum miR-497-5p expression in BC cases compared to healthy control group could support its use as a non-invasive diagnostic biomarker in BC. However, further studies of this miRNA on a larger sample of patients with different molecular subtypes are highly warranted.