Viljoen, C. D.Lamprecht, G. A.2015-09-012015-09-012009-05http://hdl.handle.net/11660/1118English: Chronic myelogenous leukaemia (CML) is a malignant clonal disorder that results in the uncontrolled production of white blood cells. This disease is a result of a reciprocal translocation of the long arms of chromosome 9 and 22 resulting in a shortened chromosome 22, harbouring the BCR-ABL fusion gene, known as the Philadelphia chromosome. The BCR-ABL oncogene encodes for a constitutively activated tyrosine kinase that interferes with normal cell differentiation and apoptosis. CML can be effectively treated with tyrosine kinase inhibitors, such as imatinib mesylate (GleevecÒ). However, some CML patients experience adverse drugs reactions (ADRs) to imatinib and cannot be treated at the recommended dose. There is a concern that lowering the dose of imatinib to reduce the side effects can result in the development of resistant cancer cells, and thus a cessation in treatment is rather recommended. Imatinib is metabolized by the cytochrome P450 enzyme, CYP3A4. However, if the ADRs were a result of decreased metabolic effect of CYP3A4, it would be possible to reduce the dose of imatinib without effecting efficacy. It is hypothesised that single nucleotide polymorphisms (SNPs) can alter the catalytic activity of the CYP3A4 enzyme. Thus a decrease in metabolic rate can result in ADRs due an increased exposure to the drug. Therefore, the aim of this study was to determine whether SNPs in the CYP3A4 gene are associated with ADRs from imatinib treatment. In this study, the DNA sequence of the CYP3A4 gene from 25 CML patients treated with imatinib were compared to a reference DNA sequence obtained from Genbank. The SNPs identified during this study was statistically analysed, and their association with the presence of ADRs was determined using the online statistics package, SNPator. A total of six SNPs were detected, I193I, T15871G, CYP3A4*1G, C23187T, I369V and G73239A. Of these, I369V and G73239A are novel and not described previously in literature. It was found that I369V resulted in an amino acid change, involving a substitution of isoleucine with valine. The remaining SNPs identified in this study were located in intron regions, with the exception of I193I which is a synonymous SNP. There is little information available on the frequency of SNPs located in introns, since these SNPs are generally regarded to have no impact on the expression or activity of a protein. However, in this study an SNP located in intron 10 was significantly associated with the presence ADRs. Current hypothesises suggest that intron SNPs could affect the expression levels of a protein by influencing the splicing efficiency of mRNA and subsequently translation efficacy. Future research needs to elaborate on the role of CYP3A4*1G on CYP3A4 expression as well as on the prevalence of other alleles identified in this study in South African populations.Afrikaans: Chroniese meloïede leukemie (CML) is ʼn kwaadaardige klonale toestand wat lei tot onbeheersde produksie van witbloedselle. Die toestand ontstaan as gevolg van ʼn resiproke translokasie tussen die lang arms van chromosoom 9 en 22. Dit lei tot ʼn verkorte chromosoom 22, die sogenaamde Philadelphia chromosoom, wat die BCRABL fusiegeen bevat. Die BCR-ABL onkogeen kodeer vir ʼn tirosienkinase wat permanent aangeskakel is en inmeng met normale selfdifferensiasie en apoptose. CML kan effektief behandel word met tirosienkinase inhibitore soos imatinib mesylate (GleevecÒ). Sommige CML pasiënte ervaar egter newe-effekte teen imatinib en die aanbevole dosis moet aangepas word. Die gevaar bestaan ook dat indien die dosis verlaag word om newe-effekte te verminder, dit kan lei tot die ontwikkeling van imatinib bestande kankerselle. Om weerstand te voorkom word opskorting van behandeling voorgestel. Imatinib word deur die sitochroom P450 ensiem, CYP3A4, gemetaboliseer. Indien die newe-effekte onstaan as gevolg van ʼn verlaagde metaboliese effek van die CYP3A4-ensiem, sou dit moontlik wees om die dosis van imatinib te verlaag sonder om die effektiwiteit daarvan te beïnvloed. Daar word gespekuleer dat enkelnukleotiedpolimorfismes (SNPs) die katalitiese aktiwiteit van die CYP3A4-ensiem kan beïnvloed. ʼn Verlaging van die metaboliese tempo kan dus lei tot newe-effekte as gevolg van ʼn verlengde blootstelling aan die middel. Die doel van die studie was dus om te bepaal of SNPs in die CYP3A4 geen gekoppel kon word aan newe-effekte as gevolg van imatinib behandeling. In hierdie studie is die DNA opeenvolging van die CYP3A4-geen vanaf 25 CML pasiënte vergelyk met die standaard DNA opeenvolging vanaf Genbank. Statistiese analises is gedoen om die assosiasie van die SNPs wat voorgekom het met die verskyning van newe-effekte te bepaal. Die SNPator program is hiervoor aangewend. In totaal is ses SNP’s waargeneem nl. I1931I, T15871G, CYP3A4*1G, C23187T, I369V en G73239A. Twee van hierdie SNPs, I369V en G73239A, is nog nie voorheen beskryf nie. Daar is vasgestel dat I369V lei tot ʼn aminosuur verandering nl. die vervanging van isoleusien met valien. Die ander SNPs wat voorgekom het was in introne geleë, met die uitsondering van I193I wat ʼn sinverwante SNP is. Daar is min inligting bekend aangaande die frekwensie van SNPs wat in introne voorkom, aangesien daar gereken word dat hierdie SNPs geen invloed het op die uitdrukking of aktiwiteit van proteïene nie. In hierdie studie is daar egter gevind dat twee intron SNPs, CYP3A4*1G en T15871G, statisties beduidend met die teenwoordigheid van newe-effekte geassosieer kon word. Huidige voorstelle dui daarop dat intron SNPs die uitdrukkingsvlakke van ʼn proteïen kan beïnvloed deur middel van ʼn effek op die snydingseffektiwiteit van mRNA te hê en dus ook die vertalingseffektiwiteit. Toekomstige navorsing moet uitbrei op die rol van CYP3A4*1G en T15871G op CYP3A4 uitdrukking asook die voorkoms van ander allele wat in hierdie studie gevind is, in Suid Afrikaanse bevolkings.enImatinibDrugs -- Side effectsProteinsChronic myeloid leukemiaDissertation (M.Med.Sc. (Haematology and Cell Biology))--University of the Free State, 2009Chromosome polymorphismDissertationUniversity of the Free State