Evaluation of mikroRNAs in cancer stem cell signaling pathways as biomarkers in breast tumors

Breast cancer is the most common type of cancer among women worldwide and is the most common cause of cancer death. It is thought that microRNAs (miRNAs) can be used as biomarkers and/or therapeutic targets due to their effective role in the initiation and progression of cancer and in the formation of cancer stem cells. In this thesis work, it is aimed to investigate miRNAs effective in cancer stem cell signaling pathways in breast tumors. Expression analyzes of 15 miRNAs were performed by RT-qPCR method in fresh tumor tissue samples of 50 breast cancer patients and in normal tissue samples of 20 of the related patients. In the evaluation of the data, Chi-Square, Kolmogorov Smirnov, T, Tukey, Mann Whitney U, Spearman's Rho correlation test, Binary Logistic Regression and ROC analysis were performed. The increase in miR-31 (p=0.034) and miR-150-3p (p=0.034) expression levels was statistically significant in all breast cancer patients. When the diagnostic values of miR-31 and miR-150-3p were investigated, it was determined that the use of these two miRNAs together could be important in the diagnosis of breast cancer. When the miRNA expressions were examined among the patients who were divided into 4 groups as Luminal A, Luminal B, HER2 (+) and TNBC according to molecular subgroups, the increase in miR-200c (p = 0.039) and miR-27a (p = 0.018) expressions in the mild (Luminal A and B) group and a decrease in the expressions of the same miRNAs in the aggressive (HER2 (+) and TNBC) group were statistically significant. When the diagnostic power of miR-200c and miR-27a was evaluated, these two miRNAs were found to be effective in determining whether the disease was Luminal A and B or HER2+ and TNBC. In the light of these findings, it is thought that miR-31 and miR-150-3p miRNAs can be a guide the evaluation of the prognosis of breast cancer patients and the metastatic process that may develop, miR-200c and miR-27a can be thought to have predictive potential in the differentiation of subtypes of breast tumors. As a result, it was concluded that the use of miRNA expression differences as a biomarker in breast tumors may be possible in the near future and further functional analyzes should be performed accordingly.