الفهرس 
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Abstract
Cancer is a term used to describe a group of disorders defined by the uncontrollable division of cells. To comprehend and combat cancer, we must first comprehend what constitutes ”normal” and the ”rules” that permit the production and maintenance of a healthy multicellular organism.
BC is a cancerous tumour that arises from the epithelial cells of the glandular milk ducts or lobules of the breast. Invasive carcinomas are cancers that expand across the body’s connective tissues and can migrate to other organs.
BC is the most common cancer in women, as well as the world’s second most common cancer. With almost 22,000 new cases discovered each year, it accounts for 33 percent of all female cancer cases in Egypt. Despite major gains in survival rates in many affluent countries, Egypt’s five-year survival rate remained low, ranging from 28% to 68%.
Surgery is considered as the primary treatment of breast cancer. Chemotherapy may also be used after surgery as an adjuvant therapy. Chemotherapy is given to most women following surgery, however breast and axillary surgery is still required after neoadjuvant chemotherapy.
In the therapy of early BC, radiotherapy (RT) is a common treatment option. RT is given to more than half of patients at some point during their disease therapy
TGF-β is a large family of proteins with a lot of different functions. It controls the growth, differentiation, motility, organisation, apoptosis, and tumorigenesis of epithelial cells. In the early stages of a tumour, the signalling pathway can operate as both a tumour suppressor and an activator.
miRNAs are single-stranded, non-protein coding RNAs that are produced endogenously. They control gene expression, transcriptionally and post-transcriptionally
miRNAs can be used for therapeutic purposes in two ways: inhibition and mimicry. Both methods escape nuclease destruction and transport miRNAs to precise target sites.
Subjects and methods: The present study is an in vitro study employing two human breast cancer cell lines MCF-7 and MDA-MB-231, each of which was divide into five groups: Group1: Cells not treated by miR-195 mimic or inhibitor and exposed to radiation doses 0, 4, 6, 8,10 Gy. group 2: Cells were treated by miR195 mimic, and were exposed to radiation at doses 0, 4, 6, 8 and 10 Gy. group 3: Cells were treated by miR195 mimic. group 4: Cells were exposed to a combination of miR195 inhibitor and radiation at doses 0, 4, 6, 8 and 10 Gy. group 5: Cells were exposed to miR195 inhibitor. Methods: The human breast cancer MCF-7(Her2+ve) and MDA-MB-231(Her2-ve) cells line were cultured. Exposure to radiation was carried out using X-ray from linear accelerator 6 MV at 0, 4, 6, 8 and 10 Gy. MiR195 inhibition and mimic were done using commercial kits. Expression Analysis by Real-time PCR was done to detect the expression of miR-195 and TGF-β. Cell viability was measured by MTT assay.