Investigation of mirna-based gene therapy roles of let-7A and mir-335 in advanced stage breast cancer stem cells


Thesis Type: Postgraduate

Institution Of The Thesis: Uludağ Üniversitesi, Turkey

Approval Date: 2017

Thesis Language: Turkish

Student: HAVVA TEZCAN

Supervisor: GÜLŞAH ÇEÇENER

Abstract:

Breast cancer is one of the most common types of cancer among women and has many subtypes. Recent studies have shown that breast cancer is developed by cell populations with stem cell potential and these cells directly affect the progression, relapse and drug resistance of the disease. It is believed that shedding light on the little-known genes in the pathways that regulate the microRNAs which play a role in the development of breast cancer may be useful in identifying novel therapeutic targets for advanced breast cancer treatment and in developing innovative miRNA based treatment strategies. The interaction between 3'UTR sites of PIK3CA and MAP2K1 genes that are potential target for let-7a and miR-335 in HCC1937 and MDA MB 231 cell lines with a high level of stem cell potential, was investigated. For this purpose; HCC1937 and MDA MB 231 cells were labeled according to their CD44+/CD24- characteristics and cell populations with high stem cell potential were obtained. After the transfection of miR-335 and MAP2K1 3'UTR into CD44+/CD24- MDA MB 231 cells, it was shown that miR-335 binds to the MAP2K1 3'UTR region and suppresses the expression (p=0,04292) of the MAP2K1 gene. In these cells, significant cell death (p=0,002) was detected after miR-335 and MAP2K1 3'UTR transfection. A significant decrease in PIK3CA expression (p=0,0435) was detected with PIK3CA 3'UTR and let-7a transfection in CD44 +/CD24- MDA MB 231 cells. However, let-7a decreased the expression of PIK3CA gene in CD44+/CD24- HCC1937 cells by 15,20-fold and cell death was significant (p=0,0046) in these cells. In the current thesis study, the binding properties of miR-335 and MAP2K1 3'UTR regions together with let-7a and PIK3CA 3'UTR and the cytotoxic effect of this binding in breast cancer stem cells were investigated for the first time. In the context of our findings, we think that let-7a and miR-335 may be new therapeutic tools in advanced breast cancer treatment.