Full text
| |
| Author(s): |
Bruna Palodetto
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas |
| Defense date: | 2012-01-20 |
| Examining board members: |
Sara Teresinha Olalla Saad;
Elvira Deolinda Rodrigues Pereira Velloso;
Carmen Sílvia Bertuzzo
|
| Advisor: | Sara Teresinha Olalla Saad |
| Abstract | |
Myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic disorders characterized by ineffective hematopoiesis resulting in peripheral blood cytopenia, about 30% of MDS patients progresses to acute myeloid leukemia. Acute leukemia (AL) are malignant blood diseases characterized by accumulation of blasts and they can be classified into acute myeloid (AML), when there is myeloblasts involvement or acute lymphoid (ALL), when there is lymphoblasts involvement. The median survival of acute leukemia patients is very low and many of them are resistant to treatment or relapsed. The better understanding of the myelodysplasia progression mechanisms and the acute leukemia response to treatment could improve the treatment response rate and patients survival. The metabolism and drug efflux are defense mechanisms responsible for protection against toxic agents and are involved in the biotransformation of various xenobiotics. The drug metabolism can be divided into two phases (Phase I: Oxidation; Phase II: Conjugation), both being mediated by drug metabolizing enzymes. The drug efflux is a similar mechanism of protection but is mediated by membrane proteins. These enzymes are polymorphic and these polymorphisms alter the enzyme activity and may modify treatment response and resistance. The CYP2B6 gene encodes a phase I enzyme responsible for drug activation. This gene has the G15631T polymorphism where there is exchange of the amino acid (Gln172His) resulting in loss of enzyme activity. The GSTM1, GSTT1 and NQO1 genes encoding phase II metabolizing enzymes that are responsible for combining with other substances to facilitate drug excretion. GSTM1 and GSTT1 genes have a polymorphism that causes homozygous deletion of the gene; and the NQO1 gene has the C609T polymorphism that results in amino acid changes (Pro187Ser). These polymorphisms lead to loss of enzyme activity. The MDR-1 gene encodes P-glycoprotein (P-gp) which is a membrane protein responsible for drug efflux. This gene has the C3435T polymorphism that despite being silent (Ile1142Ile) leads to lower P-gp expression. The aim of this study was to identify the influence of CYP2B6 G15631T, GSTT1, GSTM1, NQO1 C609T and MDR-1 C3435T polymorphisms in acute leukemia and MDS risk, MDS progression and acute leukemia response to treatment. We analyzed 90 patients with acute leukemia (66 AML and 24 ALL), 68 MDS patients and 100 normal controls using the PCRRFLP and Multiplex methods. There was no statistical difference in the frequency of polymorphisms between patients and control group. In MDS we found higher frequency of GST deletions in patients who progressed compared to patients who did not progress: 50% and 21% (P = 0.019). We also found less frequently polymorphic allele T of MDR-1 C3435T polymorphism in patients who progressed compared to patients who did not progress: 50% and 81% (P = 0.012). In acute leukemia response to the treatment, we found a trend toward a higher frequency of NQO1 C609T polymorphism in patients with induction failure compared to patients in remission, with acute leukemia in general, (P = 0.093) and AML patients only (P = 0.125); and induction failure when compared with the control group in acute leukemia in general (P = 0.101) and only in AML patients (P = 0.08). We observed the same trend when comparing the frequency of NQO1 C609T polymorphism in patients with early death versus normal population (P = 0.058). In conclusion, these results suggest that theses polymorphisms are not related to acute leukemia and MDS risk, although the sample analyzed here may have been insufficient; GST deletions and MDR-1 C3435T polymorphism are involved in MDS progression and NQO1 C609T polymorphism has a tendency to be related to induction failure and early death in patients with acute leukemia, in general, and AML only (AU) | |
| FAPESP's process: | 09/11403-3 - Influence of CYP2B6 G15631T,GSTM1, GSTT1, MDR-1 C3435T and NQO1 C609T polymorphisms in the response to treatment of acute leukemia and myelodysplastic syndrome |
| Grantee: | Bruna Palodetto |
| Support Opportunities: | Scholarships in Brazil - Master |