Vpliv polimorfizmov rs114611199, rs17839843 in rs2518469 ter tandemskih ponovitev v genu TPMT na izide zdravljenja s 6-merkaptopurinom pri bolnikih z akutno limfoblastno levkemijo

Smajlović, Elvisa (author), Karas Kuželički, Nataša (mentor), Urbančič, Dunja (comentor)

Akutna limfoblastna levkemija je najpogostejše maligno obolenje pri otrocih. Pri najdaljši fazi zdravljenja te bolezni, vzdrževalnem zdravljenju, uporabljamo tiopurine, natančneje 6 merkaptopurin. Tiopurini so citostatične in imunosupresivne učinkovine z zapleteno presnovo, ki delujejo kot antimetaboliti purinskih baz. Klinični odziv na tiopurine med posamezniki je intervariabilen zaradi mnogih dejavnikov, med katere poleg demografskih značilnosti bolnika in njegove bolezni, uvrščamo tudi genetsko predispozicijo, predvsem genetske polimorfizme v genih, ki zapisujejo metabolne encime. Najpomembnejši so polimorfizmi v genih za tiopurin S-metiltransferazo in nudiks hidrolazo 15, vendar trenutno validirani polimorfizmi ne pojasnijo vseh primerov neodzivnosti ali preobčutljivost na terapijo. V ta namen smo se odločili preučiti povezavo med genetskimi polimorfizmi v TPMT, rs114611199, rs17839843 in rs2518469, in kliničnimi podatki bolnikov z akutno limfoblastno levkemijo na terapiji s 6 merkaptopurinom. Polimorfizmi so bili izbrani glede na rezultate predhodne bioinformacijske analize v sklopu raziskave za namene druge magistrske naloge, v kateri je bilo ugotovljeno, da naj bi rs114611199 in rs17839843 povečevala aktivnost encima tiopurin S-metiltransferaza, rs2518469 pa naj bi jo zniževal. Dodatno smo zaradi morebitnega vpliva na ekspresijo gena za tiopurin S-metiltransferazo želeli določiti variabilno število tandemskih ponovitev in število trinukleotidnih ponovitev v promotorju omenjenega gena. Vsi proučevani polimorfizmi so bili v preiskovani populaciji v Hardy-Weinbergovem ravnotežju. Pri posameznikih s polimorfizmoma rs114611199 in rs17839843 smo ugotovili statistično značilno povezavo z višjim številom levkocitov in koncentracijo hemoglobina med tiopurinsko terapijo. Med relativnim kumulativnim odmerkom 6-merkaptopurina, številom trombocitov, aktivnostmi jetrnih transaminaz, koncentracijo tiogvaninskih nukleotidov in metiliranih presnovkov 6-merkaptopurina v krvi ter omenjenima polimorfizmoma nismo ugotovili statistično značilne povezave. Prav tako za polimorfizem rs2518469 nismo identificirali statistične odvisnosti z nobenim izmed prej omenjenih proučevanih kliničnih parametrov. Pri tandemskih ponovitvah v promotorski regiji smo pri bolnikih deloma potrdili frekvenco polimorfizmov, kakršno pričakujemo v splošni populaciji. Naši rezultati dokazujejo, da so med možnimi razlogi za neodzivnost na terapijo s 6-merkaptopurinom tudi do sedaj manj raziskani genetski polimorfizmi, kar ustvarja temelje za nadaljnje raziskave na tem področju.

• Language: Slovenian
• Keywords: akutna limfoblastna levkemija, 6-merkaptopurin, tiopurin-S-metiltransferaza, variabilno število tandemskih ponovitev
• Work type: Master's thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2024
• PID: 20.500.12556/RUL-156183
• Publication date in RUL: 12.05.2024

Secondary language

• Language: English
• Title: The influence of rs114611199, rs17839843, rs2518469 polymorphisms and tandem repeats in the TPMT gene on outcomes of 6-mercaptopurine treatment in patients with acute lymphoblastic leukemia

Abstract

Acute lymphoblastic leukemia is the most common malignancy in children. Thiopurines, in particular 6-mercaptopurine, are used for the maintenance therapy of this disease. Thiopurines are cytostatic and immunosuppressive drugs with a complex metabolism that act as purine antimetabolites. The clinical response to thiopurines varies due to demographic characteristics of the patient and their disease as well as genetic predisposition, especially genetic polymorphisms in genes for metabolic enzymes. The most important are polymorphisms in genes for thiopurine S-methyltransferase and nudix hidrolase 15, but currently validated polymorphisms do not always provide satisfactory explanation for inconsistent responses to therapy. For this purpose, we decided to investigate the association between genetic polymorphisms in TPMT namely, rs114611199, rs17839843 and rs2518469, and clinical data of patients with acute lymphoblastic leukemia treated with 6-mercaptopurine. The polymorphisms were selected based on the results of a previous bioinformatics analysis that was part of another master thesis, which indicated that rs114611199 and rs17839843 likely increase the enzymatic activity of the thiopurine S-methyltransferase, while rs2518469 could decrease it. Additionally, we aimed to determine the variable number of tandem repeats and the number of trinucleotide repeats in the promoter region of TPMT, as it has been shown that they might affect the expression of the gene. All investigated polymorphisms were in Hardy-Weinberg equilibrium in the study cohort. In individuals with polymorphisms rs114611199 and rs17839843, we found a statistically significant association with increased leukocyte count and hemoglobin concentration. We found no statistically significant correlation between the relative cumulative dose of 6-mercaptopurine, platelet count, liver transaminase activities, blood levels of thioguanine nucleotide and methylated metabolites of 6-mercaptopurine, and these polymorphisms. We also did not identify any statistically significant associations between the rs2518469 polymorphism and any of the abovementioned clinical data. We partially confirmed that the frequency of polymorphisms in promoter region was as expected in the general population. Our results show that also less studied genetic polymorphisms could be considered as possible causes for non response to 6-mercaptopurine therapy, which sets the basis for further research in this area.

• Keywords: acute lymphoblastic leukemia, 6-mercaptopurine, thiopurine-S-methyltransferase, variable number of tandem repeats