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Title: Translational regulation of ABCB1 gene in acute myeloid leukaemia (AML)
Author: Bajuaifer, Nada A.
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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Introduction: Multidrug Resistance (MDR) was and remains a major obstacle in the way of successful chemotherapy for cancer patients and especially acute myeloid leukaemia (AML) patients. In AML, MOR mediated by ABCBl over-expression accounts for the majority of MOR cases. The ABCB1 gene encodes a surface protein known as P-glycoprotein (Pgp) which plays a major role in MOR by effluxing drugs out of cells leading to increased relapse rates in AML patients. The regulation of ABCBl and subsequently Pgp is multifactorial and can be altered at many levels. Common regulators of genes expression may play a role in the regulation of this gene such as genetic sequence variation in the form of single nucleotide polymorph isms and short noncoding RNAs known as microRNAs. Results and Discussion: Role of different regulators in the regulation of ABeBl gene was investigated; these were microRNAs and 3'UTR SNP (specifically rs3842). Microarray profiling of 11 AML cell lines and 45 NeRN AMLl4 and AMLl5 trial patients samples showed significant down-regulation of miR-34b and miR-503 in Pgp positive cell lines when compared with Pgp negative cell lines and miR-l48a, miR-45l, miR-659, miR-499-5p, miR-l97 and miR-642 in Pgp positive patient samples when compared with Pgp negative patient samples. This suggests a role of these miRs in MDR in AML. No significant up-regulation was found in the Pgp positive cell lines and patients samples when compared with the Pgp negative group. Functionally, no direct effect of miR-l48a and miR-34b on ASeSl3'UTR constructs and Pgp protein level (for miR-34b) was found but an indirect effect of these miRs on ASeS! still needs to be tested. Second, the role of rs3842 on regulation of ABeBl gene was investigated. rs3842 genotyping of 455 NCRN AMll4 and AML15 trial patients showed comparable distribution to the reported distribution of the genotypes of normal healthy European population. Furthermore, an effect of the rs3842 polymorphism on Pgp protein expression and function (but not at the mRNA level) was seen in the 35% of patients where ASeS! expression is high. Functionally, higher baseline activity of the ASeS! wild type 3'UTR construct was found when compared with the ABeBl variant 3'UTR construct and a further construct mutated by site-directed mutagenesis. On examination of the rs3842 polymorphism and surrounding sequence, it was predicted that miR-374a targets AseSl very close to the SNP. This went to show that miR-374a causes down-regulation of ASCSl 3'UTR activity but only when the wild type rs3842 allele A is expressed. In addition, an effect of miR-374a on Pgp protein expression was found at the protein level but not at the mRNA suggesting a role of miR-374a in the translational regulation of the ABCBl gene. To conclude, the role found of microRNAs (miR-374a) and rs3842 in ABCBl regulation in this work suggests a significant role of the 3'UTR of ABCBl gene in its regulation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available