الفهرس 
Aknowledgement
Histopathological typingOnly 14 pages are availabe for public view
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Abstract
Globally, BC is the most common cancer and the leading cause of cancer mortality in women. Approximately, 1.7 million new BC cases are affected with over half million deaths each year. There is a large variation in BC survival rates around the world, with an estimated 5-year survival of 80% in high income countries to below 40% for low income countries. Such variation is attributed to early detection and diagnosis of BC with extremely better outcome.
DNA methylation is a reversible inheritable posttranslational addition of methyl (ch3) group on cytosine residue. Such modification affect transcriptional activity according to degree of methylation change. DNA methylation has very crucial role in pathogenesis and development of BC. Recently, DNA methylation represent the most promising cost-effective tool for early detection of BC cases.
The present study was designed to:
1) Detect methylation state of DKK3 and SOX17 genes in BC, high risk and control groups by measuring their methylation percentage.
2) Reveal the alterations of methylation of DKK3 and SOX17gene in BC patients and their corresponding relatives for early detections of BC in those high risk subjects.
3) Correlate methylation percentage with demographic data and BC risk factors.
4) Examine the association of methylation of DKK3 and SOX17 genes with breast tumor characteristics for better understanding of the molecular mechanism in the development and progression of BC.
This study is a case control study with 30 new diagnosed BC patients (stage I, II and III) who attended surgical oncology department in South Egypt Cancer Institute from march 2017 to February 2018, with exclusion criteria: a prior history of other cancer, bilateral BC or receiving radiotherapy or chemotherapy. All patients provided informed consent for obtaining the study specimens. All patient’s medical history has been taken and they were subjected to mammography, Ultrasound, MRI, CT and tru-cut needle biopsy with pathological examination of the specimens. In addition , 30 subjects with age matched women had family history of BC in first degree relatives (mother, sister or daughter) and were overweight with BMI (25-29) or obese (BMI more than 30). Finally, 30 apparently healthy, age matched subjects with no family history of breast cancer and with normal BMI (18.5-25).
3 ml of venous blood were drawn on EDTA containing tubes and stored at -80°C until DNA extraction. DNA was extracted, then bisulfide conversion of unmethylated cytosine to uracil but methylated cytosine remained unchanged. Methylation-Specific SYBER green PCR (qPCR) was done by using specific methylated and unmethylated primers by 7500 fast real-time PCR system (Applied Biosystems) then methylation percentages of DKK3 and SOX17 were calculated.
The study demonstrates that DKK3 and SOX17 methylation percentages were significantly different in three studied groups. Highest DKK3 and SOX17 methylation percentages were in BC group with significant p value ( < 0.001 and = 0.002 ) respectively and methylation percentages of DKK3 and SOX17 were significantly higher in high risk group than control group.
DKK3 methylation percentage was significantly associated with age at diagnosis, age at menarche, duration of breast feeding, menopausal status and BMI.
SOX17 methylation percentage was negatively correlated with age at diagnosis and positively correlated with BMI.
Moreover, DKK3 methylation percentage was significantly higher in progesterone receptor negative staining cases with significant p value = 0.024. SOX17 methylation percentage was significantly higher in tumor sizes larger than 2 cm with significant p value = 0.044.
Limitations in this study include small sample size, technical difficulties and high cost of the kit.
Conclusion
DKK3 and SOX17 methylation percentages were significantly different between BC patients, high risk women and control samples. And DKK3 methylation percentage was found to be significantly correlated with PR receptor status whereas SOX17 methylation percentage was significantly correlated with tumor size. These findings suggest that DNA methylation could be an appropriate, reliable, sensitive and noninvasive tool for early detection of BC cases.
Detection of promoter methylation of certain genes in peripheral blood is highly sensitive and specific method that can be used in early detection of breast cancer cases and proper choice of treatment modalities.