Farmacogenética aplicada al tratamiento de la leucemia linfoide aguda / Pharmacogenetics applied to the treatment of acute lymphoid leukemia

Las enzimas de biotransformación y eliminación de los fármacos en pacientes con leucemia linfoide aguda tienen una acción determinante en el efecto terapéutico de los medicamentos antineoplßsicos. La presencia y actividad de estos complejos enzimáticos está codificada genéticamente y sujeta a variaciones alélicas, cuyas frecuencias son variables en las diferentes poblaciones humanas. Este polimorfismo genético influye sobre la efectividad terapéutica de los medicamentos y condiciona la carencia de toxicidad o presencia de esta, que en ocasiones puede ser fatal. Las enzimas tiopurin-metil-transferasa, metilén-tetrahidrofolato-reductasa y glutatión-tranferasa son sistemas destoxificadores de algunos de los quimioterápicos empleados en el tratamiento de la leucemia linfoide aguda. En este trabajo se revisan las características genéticas de estas enzimas, la frecuencia de sus polimorfismos y las implicaciones clínicas de su expresión. De igual modo se discute la importancia y los beneficios del genotipaje previo al inicio del tratamiento, con el fin de modificar las dosis de los medicamentos para optimizar su efecto terapéutico y disminuir su toxicidad. La farmacogenética constituye un área de creciente interés que ha tenido un desarrollo considerable en los últimos años, su conocimiento e implementación nos colocará en el camino de la medicina personalizada

The biotransformation and elimination enzymes of drugs in patients suffering from acute lymphoid leukemia play a decisive role on the therapeutical effect of anti-neoplastic drugs. The presence and activity of these enzymatic complexes are genetically coded and subjected to allele variations, the frequency of which is variable in the different human populations. This genetic polymorphism has an impact on the therapeutic effectiveness of drugs and determines the lack or the existence of toxicity that may sometimes become lethal. The enzymes called thiopurine-methyltransferase, methylen-tetrahydropholate-reductase and glutathione-transferase are detoxifying systems of some of the chemotherapeutic drugs that are used for the treatment of acute lymphoid leukemia. This paper reviewed the genetic characteristics of the enzymes, the frequency of polymorphisms and the clinical implications of their expression. Similarly, the importance and the benefits of genotyping before the treatment were discussed in order to change the drug doses to maximize the therapeutic effect and reduce toxicity. Pharmacogenetics has experienced great development in the last few years and draws growing interest; the knowledge about and the implementation of this discipline will take us to the customized medicine

Platelet enzyme abnormalities in leukemias.

Aim of the Study: The aim of this study was to evaluate platelet enzyme activity in cases of leukemia. Materials and Methods: Platelet enzymes glucose-6-phosphate dehydrogenase (G6PD), pyruvate kinase (PK) and hexokinase (HK) were studied in 47 patients of acute and chronic leukemia patients, 16 patients with acute myeloid leukemia (AML)(13 relapse, three in remission), 12 patients with acute lymphocytic leukemia (ALL) (five in relapse, seven in remission), 19 patients with chronic myeloid leukemia (CML). Results: The platelet G6PD activity was significantly low in cases of AML, ALL and also in CML. G6PD activity was normalized during AML remission. G6PD activity, although persistently low during ALL remission, increased significantly to near-normal during remission (P < 0.05) as compared with relapse (P < 0.01). Platelet PK activity was high during AML relapse (P < 0.05), which was normalized during remission. Platelet HK however was found to be decreased during all remission (P < 0.05). There was a significant positive correlation between G6PD and PK in cases of AML (P < 0.001) but not in ALL and CML. G6PD activity did not correlate with HK activity in any of the leukemic groups. A significant positive correlation was however seen between PK and HK activity in cases of ALL remission (P < 0.01) and CML (P < 0.05). Conclusions: Both red cell and platelet enzymes were studied in 36 leukemic patients and there was no statistically significant correlation between red cell and platelet enzymes. Platelet enzyme defect in leukemias suggests the inherent abnormality in megakaryopoiesis and would explain the functional platelet defects in leukemias.

Immune status & enzymes activity in blood lymphocytes in adult patients at different stages of acute lymphoblastic leukaemia.

Background & objectives: Pathogenesis acute lymphoblastic leukaemia (ALL) in adults is not well understood, as it is more common in children. We examined the immunological status and the activity of certain enzymes in blood lymphocytes in adult patients of ALL at different stages. Methods: ALL patients (n=71) admitted during 2000-2005 were included in this study. All patients had decreased T-lymphocytes content. At first attack, they had CD4 +-cells decreasing and increasing IgM and IgG concentration. In complete remission all examined parameters were low. The peculiarities of ALL recurrence were high NK-cells content and disbalances of the main immunoglobulin concentrations. Results: In the first attack and recurrence the anaerobe glucose oxidation intensity and the reactions of macromolecular synthesis were lower in lymphocytes compared to control. In remission all these processes restored to normal. In all stages in lymphocytes GR had decreased activity. Interpretation & Conclusions: Our results showed that most of changes in immune status of ALL patients were in a stage of complete remission when patients arrived on its maintenance through the small period from spent before therapy when the immune system of the patient has not been restored. Thus, probably cytostatic action causes immune failure in the future and starts disease again.

Methylenetetrahydrofolate reductase gene polymorphisms and risk of acute lymphoblastic leukemia in children.

Introduction: Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and is involved in DNA synthesis, DNA repair and DNA methylation. Genetic polymorphisms of this enzyme have been shown to impact several diseases, including cancer. Leukemias are malignancies arising from rapidly proliferating hematopoietic cells having great requirement of DNA synthesis. This case-control study was undertaken to analyze the association of the MTHFR gene polymorphisms 677 C"T and 1298 A"C and the risk of acute lymphoblastic leukemia in children. Materials and Methods: Eighty-six patients aged below 15 years with a confirmed diagnosis of acute lymphoblastic leukemia (ALL) and 99 matched controls were taken for this study. Analysis of the polymorphisms was done using the polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) method. Results: Frequency of MTHFR 677 CC and CT were 85.9% and 14.1% in the controls, and 84.9% and 15.1% in the cases. The 'T' allele frequency was 7% and 7.5% in cases and controls respectively. The frequency of MTHFR 1298 AA, AC, and CC were 28.3%, 55.6% and 16.1% for controls and 23.3%, 59.3% and 17.4% for cases respectively. The 'C' allele frequency for 1298 A→C was 43.9% and 47% respectively for controls and cases. The odds ratio (OR) for C677T was 1.08 (95% CI 0.48- 2.45, p = 0.851) and OR for A1298C was 1.29(95% CI 0.65-2.29, p = 0.46) and OR for 1298 CC was 1.31 (95% CI 0.53-3.26, p =0.56). The OR for the combined heterozygous status (677 CT and 1298 AC) was 1.94 (95% CI 0.58 -6.52, p = 0.286). Conclusion: The prevalence of 'T' allele for 677 MTHFR polymorphism was low in the population studied. There was no association between MTHFR 677 C→T and 1298 A→C gene polymorphisms and risk of ALL, which may be due to the small sample size.

Glutathione S-transferase P1 genotypes, genetic susceptibility and outcome of therapy in thai childhood acute lymphoblastic leukemia.

Glutathione S-transferases (GSTs) are enzymes that involved in bio- transformation by conjugation of electrophillic compounds to glutathione. Polymorphisms within genes that encode GSTs may affect the function of the enzymes. Polymorphisms of GSTP1 at codon 105 residue forms GSTP1 active site for binding of hydrophobic electrophiles, and the Ile-Val substitution affect substrate specific catalytic activity of this enzyme and may associate with susceptibility to malignant human disease, especially acute lymphoblastic leukemia (ALL), which is the most common leukemia in children younger than 15 years old.Genetic polymorphisms within the GSTP1 gene of childhood ALL patients were studied. In addition, the association of genetic polymorphism of GSTP1 and genetic susceptibility of acute lymphoblastic leukemia (ALL) was also determined using Chi-square and Odds ratio. PCR-RFLP was used to study genetic polymorphism of GSTP1 in 100 ALL patients and 100 healthy individuals.The results show that there is no statistically significant association between each genotypes and genetic susceptibility of acute lymphoblastic leukemia (ALL) (OR=0.92, P -value=0.886). Moreover, there is no statistically significant association between each genotypes and demographic data of acute lymphoblastic leukemia (ALL). However, there are 2 cases of ALL with BM relapse show the polymorphic genotypes of GSTP1. It may suggest that GSTP1*V105 may be involved in relapse of ALL.

Erythrocyte enzyme abnormalities in leukemias.

Red cell enzymes were assayed in a total of 67 patient including 24 patients with AML (19 relapse, 5 remission), 16 patients with ALL (10 relapse, 6 remission), 22 patients with CML and 5 patients with blastic CML. Diagnosis of leukemia was based on clinical presentation, peripheral blood smear and bone marrow examination (as per FAB classification). PK activity was significantly high in case of CML and blastic CML (p<0.01). Red cell HK was high in all leukemia subtypes. There was no alteration in red cell G6PD. Notably there was no PK deficiency in AML or G6PD deficiency in ALL. Activities of G6PD and PK could be correlated in cases of CML, AML, (p<0.05) and ALL (p<0.01) i.e. when there was increased activity of G6PD, PK activity also tended to be higher. HK activity showed a positive correlation with PK and G6PD activity in cases of CML (p<0.05), however in acute leukemia there was no such correlation. Alteration of enzyme activities among red cells in leukemia occurred only during relapse. At the time of remission there has been no significant alteration in any of the enzyme activities. It would therefore, appear that enzyme alterations seen in leukemia patients is due to abnormal pluripotent stem cell that has given to a leukemia cell. The fact that enzyme alterations have primarily occurred at the time of relapse would further substantiate that abnormalities of red cell enzymes may be the result of a derivation some circulating red cells from the abnormal pluripotent stem cell. With the recovery of normal stem cells function during remission, enzyme abnormalities tend to become normal.

Metaloproteinasas como marcadores de progresión tumoral y futuros blancos de terapias en patologías linfoides / Metalloproteinases as markers of tumoral progression and future targets for therapies in neoplasms of lymphoid tissue

En las últimas décadas la medicina evolucionó hacia un enfoque molecular en la búsqueda de blancos específicos que permitan seguir adecuadamente la progresión de las patologías neoplásicas y desarrollar terapias exitosas. El conocimiento y comprensión de que la matriz extracelular (MEC) que rodea a un tumor influye sobre el comportamiento del mismo, reveló la importancia que cumplen las metaloproteinasas (MMPs) en la regulación de los componentes de la MEC, y por lo tanto en el desarrollo tumoral. Es por ello que actualmente se está evaluando la eficacia de inhibidores sintéticos de estas enzimas en ensayos clínicos, algunos ya en fase clínica III de investigación. También se propone que estas MMPs podrían ser utilizadas como marcadores bioquímicos, permitiendo evaluar la progresión de la enfermedad en pacientes que sufren patologías neoplásicas, e incluso dar un valor pronóstico. Es en este punto en que el laboratorio de análisis clínicos cumplirá un papel fundamental y deberá contar con los conocimientos y las herramientas necesarias para evaluar la presencia y actividad de estas enzimas. En este trabajo se expone el conocimiento actual de la estructura y funciones biológicas de las MMPs así como los antecedentes que muestran el papel que cumplen en las enfermedades neoplásicas, en especial en leucemias y linfomas

Leukocyte glucose 6 phosphate dehydrogenase (G6PD) as prognostic indicator in children with acute lymphocytic leukemia.

G6PD activity, estimated in 37 patients with acute lymphocytic leukemia (ALL) prior to therapy was found to be significantly decreased in 78.37% of the patients with ALL while it was normal in other patients. Variation in G6PD was found to be dependent on the percentage of myelocytes. Correlation analysis of leukocyte G6PD activity with karyotype indicated that patients with normal karyotype with normal G6PD activity had good prognosis while those with abnormal G6PD with abnormal karyotype had poor prognosis. Subjects with normal karyotype and abnormal G6PD and vice versa had intermediate prognosis. Thus the results clearly indicate that leukocyte G6PD may be used as a diagnostic and prognostic tool.

Alteraciones bioquímicas y citoquímicas de hidrolasas ácidas lisosomales en leucemias / Biochemical and citochemical alterations of lisosomal acid hydrolases in leukemias

La actividad enzimática total de ß-galactosidasa (ß-gal), hexosaminidasa (hex) y fosfatasa ácida (Fac) fue determinada bioquímicamente, tanto en suero como en sobrenadantes de homogenatos celulares de sujetos normales y pacientes portadores de leucemias, empleándose sustratos paranitrofenilados específicos. La actividad de ß-gal en leucemias mieloides, tanto agudas (LMA-M1) como crónicas (LMC), sólo mostró un incremento significativo en sobrenadantes de homogenato celulares, respecto a los valores de neutrófilos normales. En leucemias linfoidales agudas (LLA), como crónicas (LLC), su comportamiento no ofreció variaciones. Tanto los sueros como los sobrenadantes de homogenatos celulares de LMA-M1 y LMC mostraron un franco incremento en la actividad de hex, mientras en LLA y LLC esta actividad no mostró variaciones. La actividad sérica de fosfatasa ácida estuvo incrementada en el 86% de las LMC. En los sobrenadantes de homogenatos celulares de LLA y LLC, esta actividad enzimática se mostró significativamente disminuida respecto de los valores de linfocitos normales. En los tres casos de LMA-M4 analizados, fue observado en el contenido celular niveles elevados de ß-gal, hex y Fac (lo que estaría correlacionado con la presencia de monocitos y/o monoblastos normales, con alto contenido de hidrolasas ácidas). Citoquímicamente fue demostrado en médula ósea y sangre periférica de pacientes con LMA-M1 una ligera o nula actividad de hex, en tanto que en LLA la reacción fue localizada asimétricamente en un polo celular o en gránulos citoplasmáticos. Los resultados encontrados demuestran una gran heterogeneidad en el contenido lisosomal de los diferentes tipos de leucemias