Browsing by Subject "14q31.32 miRNA cluster"
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Item Open Access Effects of depletion of CHRNA5 and/or TP53, and transient and stable overexpression of wildtype or mutant TP53 on expression of DLK1-MEG3 locus in MCF7 cells(Bilkent University, 2022-09) Arıcı, Burçin İremThe expression of CHRNA5 has a prominent role in lung cancer and nicotine addiction. Besides, depletion of CHRNA5 has been identified as being tumour suppressive in breast cancer. Moreover, CHRNA5 depletion causes increases in CDKN1A expression, downregulates the 14q32.31 miRNAs and decreases DLK1 expression. This thesis examined the effects of CHRNA5 and/or TP53 downregulation, as well as TP53 overexpression, on the expression of the DLK1-DIO3 region. My findings demonstrated that CHRNA5 depletion decreased the expression of the protein-coding DLK1 and the non-protein coding MEG3 genes in this locus in the presence or absence of TP53. Since these two genes have a vital role in tumour suppression and tumorigenesis, this provided more evidence for the importance of CHRNA5 in the modulation of expression in this locus in breast cancer. Since there is a relation between CHRNA5 and TP53 induction, the expression of one of the main TP53 regulators, MDM2, was also studied. Accordingly, it was found that combining CHRNA5 depletion with TP53 depletion caused a significant decrease in expression in both the MDM2 and MDM2 sequestering elements, PDLIM7 and CDH18. Additionally, the effects of both wild-type and mutant TP53 expression levels on DLK1-MEG3 locus and CHRNA5 were investigated in stable MCF7 breast cancer cells that we have generated. I have found that even if CHRNA5 depletion induced p53 expression, TP53 overexpression did not have CHRNA5-inducing effects regardless of the functionality of TP53. However, wild-type TP53 overexpressing MCF7 cells behaved differently than mutant TP53 overexpressing cells in their DLK1 expression levels. Future research should clarify the effects of CHRNA5 depletion on DLK1-MEG3 region for a given TP53 mutation status.Item Open Access Identification of modulatory functions of TP53, estrogen signaling, and 14q32.31 miRNA cluster on CHRNA5 knock-down expression profile and development of syneRgy APP(Bilkent University, 2021-09) Keşküş, Ayşe GökçeCholinergic receptor subunit alpha 5 (CHRNA5) is a ligand-gated ion channel expressed in not only the nervous system but also other tissues. Differential expression and the polymorphisms of CHRNA5 have been associated with addiction, particularly nicotine and various cancer types. The tumor-suppressive properties of CHRNA5 depletion, i.e., decrease in cell proliferation, induction of DNA damage response, and drug sensitivity, have been identified in breast cancer cell lines. This thesis focuses on identifying critical factors modulating or modulated by the knock-down of CHRNA5 in breast cancer cell lines using both wet-lab and bioinformatics approaches. Here I have first found the significant correlation between CHRNA5 and DNA damage response in breast cancer tumor datasets. Moreover, I discovered that the introduction of siTP53 antagonized the actions of siCHRNA5 and reverted the siCHRNA5-mediated cell cycle inhibition and drug sensitivity in the MCF7 breast cancer cell line. Furthermore, siCHRNA5 was found to inhibit the secondary signaling of estrogen/ESR1 in time and dosage-dependent manners. CHRNA5 depletion also downregulated the conserved 14q32.31 miRNA cluster expression. Among those miRNAs, miR495-3p appeared to be the most prominent candidate, exhibiting a similar expression profile with selective estrogen degraders and partially with siCHRNA5. However, the inhibitory effect of the combinatorial treatment with siCHRNA5 and miR495-3p on the secondary targets of estrogen signaling indicated that siCHRNA5 and miR495-3p might target converging pathways, evidenced by the antagonism (rather than addictiveness) between them. In addition, the Shiny-based syneRgy app was developed to analyze the transcriptome-based synergy between treatments and/or genetic modifications. As a case study, syneRgy analysis using novel MDM2 inhibitor and/or temozolomide treated neuroblastoma cell lines revealed that although the tumor-suppressor effect of combination therapy was more than each individual treatment, it was less than additive. syneRgy was applied to understand the combinatorial treatment of siCHRNA5 with siTP53 as well as siCHRNA5 with miR495-3p mimic and enhanced our understanding of the TFs that might have a role in the crosstalk. To our knowledge, syneRgy is the first-ever online tool to perform statistical synergy analysis using RNAseq count or logFC transcriptomic data and synreg, i.e. our novel methodology allowing for statistical tests of TF target enrichment using regression models.