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CLINICAL OBSERVATIONS, INTERVENTIONS, AND THERAPEUTIC TRIALS
From the Istituto di Ematologia, Universita' Cattolica
S. Cuore and Dipartmento di Biotecnologie Cellulari ed Ematologia,
Universita' La Sapienza, Rome, Italy.
Glutathione S-transferases (GSTs) are enzymes involved in the
detoxification of several environmental mutagens, carcinogens, and
anticancer drugs. GST polymorphisms resulting in decreased enzymatic
activity have been associated with several types of solid tumors. We
determined the prognostic significance of the deletion of 2 GST
subfamilies genes, M1 and T1, in patients with acute myeloid
leukemia (AML). Using polymerase chain reactions, we analyzed the
GSTM1 and GSTT1 genotype in 106 patients with AML (median age, 60.5 years; range, 19-76 years). The relevance of
GSTM1 and GSTT1 homozygous deletions was
studied with respect to patient characteristics, response to therapy,
and survival. Homozygous deletions resulting in null genotypes at the
GSTM1 and GSTT1 loci were detected in 45 (42%)
and 30 (28%) patients, respectively. The double-null genotype was
present in 19 patients (18%). GST deletions predicted poor response to
chemotherapy (P = .04) and shorter survival
(P = .04). The presence of at least one GST deletion
proved to be an independent prognostic risk factor for response to
induction treatment and overall survival in a multivariate analysis
including age and karyotype (P = .02). GST genotyping was
of particular prognostic value in the cytogenetically defined
intermediate-risk group (P = .003). In conclusion,
individuals with GSTM1 or GSTT1 deletions (or
deletions of both) may have an enhanced resistance to chemotherapy and
a shorter survival.
(Blood. 2002;100:2703-2707) Chemical carcinogens react with DNA after metabolic
activation by hydrolysis, reduction, or oxidation. The results of this interaction are mutations and eventually the initiation of cancer. Glutathione S-transferases (GSTs) are a family of cytosolic enzymes contributing to the detoxification of activated
carcinogens.1-3 Substrates for the GST enzymes are
environmental pollutants, such as benzo(a)pyrene and other polyaromatic
hydrocarbons, but also anticancer drugs, including alkylating agents,
anthracyclines, and cyclophosphamide metabolites.1-3
Four major classes of GSTs have been described ( Recently, some studies have addressed the role of GST
polymorphisms in the development of hematologic malignancies. Few data were reported so far for adults with acute myeloid leukemia
(AML),10-15 and, in particular, to our knowledge, there
are only few reports on the relationship between GST genotypes,
clinical outcome, and established indicators of prognosis in adult AML.
We examined the frequency of GSTM1 and GSTT1
deletions in adults with AML and correlated the genotypic status to
patient clinical and biologic characteristics. Finally, we investigated
the impact of GST genotyping on response to induction therapy and
overall survival of adult AML.
Patient characteristics
The diagnosis of AML was established according to morphology and
immunophenotype, following the French-American-British (FAB) classification criteria. Fifteen patients had a leukemia secondary to a
previous malignancy. Karyotype was available for 77 patients; none of
them had abnormalities of chromosomes 1p (location of GSTM1)
or of chromosome 22q (location of GSTT1). Patients were treated according to current AML protocols of the Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto (GIMEMA group), combining an
anthracycline (doxorubicin or idarubicin or mitoxantrone), cytarabine,
and etoposide for induction, followed by chemotherapy consolidation
and, for eligible patients, autologous or allogeneic stem cell
transplantation (EORTC-GIMEMA AML 10, 12, and 13). Eleven patients with
acute promyelocytic leukemia were treated according to the GIMEMA-AIDA
0493 protocol (www.gimema.org). Toxic deaths were defined as
all deaths occurring after start of treatment and before bone marrow
evaluation on day +28 (n = 11). Complete remission (CR) or partial
remission and resistance to induction treatment were assessed by bone
marrow evaluation on day +28 in 95 patients (excluding 11 toxic
deaths), according to standard National Cancer Institute
criteria.16 Informed consent was obtained from all
patients, according to institutional guidelines.
DNA extraction and amplification
Statistical analysis The statistical significance of the differences between groups was calculated using the Fisher exact test (2-sided). Crude odds ratios (ORs) were performed separately for GSTM1 and GSTT1 deletions and are given within 95% CIs. Age, sex, FAB subtype, history of previous cancer, and cytogenetics were included as covariables as were all genotypes and possible interactions. Cytogenetic risk groups were defined according to Grimwade et al17: favorable: t(8;21), t(15;17), inv(16); intermediate: normal, +8, +21, +22, del(7q), del(9q), abnormal 11q23, all other structural/numerical abnormalities without additional favorable or adverse cytogenetic changes; unfavorable: 5,
7, del(5q), abnormal 3q, complex karyotype. Multivariate regression
models were performed to examine the relationship between the dependent
variable (presence of GSTM1 or GSTT1 deletion) and potential predictor variables, both continuous and dichotomic, that
is, age and karyotype. Event-free survival was defined as the time
between initial diagnosis and relapse or death, whereas overall
survival was the time between diagnosis and death. Survival curves were
estimated using the Kaplan-Meier product-limit method. Differences in
the survival curves were evaluated with the log-rank test. All
computations were performed using the Stata 6.0 software (Stata,
College Station, TX).
Frequency of GST deletions and patient characteristics The GSTM1 null genotype was detected in 45 AML patients (42.4%) and the GSTT1 null genotype in 30 patients (28%); 19 patients (17.9%) had a double-null genotype.The GST genotype was correlated to patient characteristics by examining
the GSTM1 and GSTT1 deletions separately (Table
1). We grouped patients according to age,
sex, history of previous cancer, FAB type, and cytogenetics. The effect
of age was compared splitting the patients into 2 age groups (19-59 years, n = 48, and 60-75 years, n = 58). A higher frequency of GST
deletions was found in patients over 60 years of age (Table 1). When
compared to patients with a double-positive GST genotype, an
association between the presence of any GST null genotype and age of 60 years and older was found (P = .006; OR, 3.2, 95% CI,
1.4-7). No association between sex and GST genotypes was found (Table
1). Because GSTs are involved in detoxification of both natural and
drug carcinogens, we analyzed the distribution of GST genotypes with
respect to the history of previous cancer. No differences were observed
comparing de novo leukemias versus leukemias secondary to other
malignancies (Table 1). Furthermore, no differences were found when
grouping patients according to FAB subtype, although it should be
recognized that the numbers in each category might have been too small
to detect significant effects (Table 1).
Cytogenetic data were available for 77 patients. Thirty-four patients had a normal karyotype, 20 had a simple balanced translocation, and 23 patients had a complex karyotype. This corresponds to 19 patients with prognostically favorable, 48 with intermediate, and 10 with unfavorable cytogenetics, according to Grimwade et al.17 No differences in the frequency of GST deletions were found when comparing the different groups (Table 1). Prognostic value of GSTM1 and GSTT1 deletions The role of GSTs in the detoxification of chemotherapy agents prompted us to examine the relationship between response to chemotherapy and GST genotype. When considering patients who died of toxic complications after initiation of chemotherapy, but before response assessment at day 28 (n = 11), no associations between GST deletions and toxic deaths were found, although the number of patients might have been too low to detect differences.Ninety-five patients were evaluable for the response to induction
treatment analysis. Following induction therapy, 67 patients achieved
CR, whereas 28 patients were resistant. When compared to patients with
GSTM1 or GSTT1 deletions, patients with an
undeleted genotype had a significantly better response to induction
therapy (Figure 1). Thirty-six of 44 (81.8%) patients with undeleted genotype and 31 of 51 (60.8%) of
those with GSTM1 or GSTT1 deletions achieved CR
(OR for risk of not achieving CR = 2.9; 95% CI, 1.2-7.5;
P = .04). The multivariate analysis showed that this risk
was independent of age and karyotype (P = .02; Table
2).
The higher rate of CRs in patients with both an undeleted
GSTM1 and GSTT1 genotype translated in a
significantly longer event-free and overall survival as compared with
patients with single or combined deletions (median event-free survival,
11.2 and 7.5 months, P = .05, and median overall survival,
15 and 8 months, respectively, P = .04; Figure
2).
We next analyzed whether the presence of at least one GST null genotype
was an independent prognostic factor. In the multivariate analysis
using the Cox regression model, we included age and cytogenetics as
well established prognostic factors (Table 2). In this analysis, the
presence of at least one GST deletion proved to be a poor prognostic
factor for survival (P = .01, Table 2). GST genotyping could discriminate between favorable and unfavorable prognosis in
patients with intermediate-risk karyotype (hazard ratio [HR] = 2.9
for at least one GST null genotype, P = .003), whereas no impact of GST genotyping on prognosis became evident in patients with
either favorable or unfavorable karyotype17 (Figure
3).
Environmental pollutants and anticancer drugs, including alkylating agents, anthracyclines, and cyclophosphamide metabolites, are detoxified by enzymes that catalyze reactions as glucuronidation, sulfonation, acetylation, methylation, and conjugation with glutathione or amino acids, following activation.1-3 We found an increased frequency of GSTM1 null genotypes in patients with AML over 60 years of age. Prolonged exposition of hematopoietic progenitor cells to toxic agents in combination with a reduced capability of detoxification might contribute to the pathogenesis of AML in the elderly. Because the incidence of AML evolving after cytotoxic treatment for malignant disease increases with age, one might also expect an association between GST null genotypes and the risk for therapy-related leukemia.18 In our study group, no differences between de novo and secondary leukemias were observed. Leukemias of the elderly and therapy-related leukemias often show a higher frequency of prognostically unfavorable cytogenetic changes.19-20 Rollinson et al10 found an increased frequency of GSTT1 null genotypes in patients with balanced translocations, whereas Crump et al14 reported an association between GSTT1 gene deletion and trisomy 8, as well as between GSTM1 gene deletion and trisomies other than +8 and inv(16). However, we could not find any association between karyotype and GST genotypes in the present series. Further studies on larger series of patients extensively characterized at the karyotypic level are probably needed to better investigate possible associations between GST genotype and cytogenetic abnormalities in AML. In the present study, AML patients with deletions of GSTM1 or GSTT1 or both had a lower probability to achieve CR on induction therapy as compared to patients with intact GST genes. The reasons underlying this finding are unclear. The lack of detoxification of electrophilic, DNA-damaging agents may contribute to the accumulation of genetic changes in the process of leukemogenesis. In this line, the absence of GST enzymes might simply reflect a biologically distinct, more aggressive disease. Although the available karyotypic results suggested absence of relevant associations between cytogenetic and GST genotypic status, we have no data on more subtle genetic changes including point mutations in oncogenes or tumor suppressor genes (ie, RAS, p53) and other karyotypically silent alterations such as FLT3 tandem duplication.19,20 Possible association of GST genotypes with molecular genetic alterations might represent an interesting topic for future investigation. An alternative mechanism to explain the impact of GST genotypes on outcome results from the putative role of these enzymes in the metabolism of several cytotoxic drugs, such as anthracyclines, used in induction chemotherapy for patients with AML. GSTs contribute to detoxification either by direct conjugation of the drug with glutathione, increasing its secretion via bile and urine, or by neutralization of reactive compounds induced by the cytotoxic drug.1 This detoxification can protect cells from the injuries of chemotherapy. Expression of GST enzymes has been linked to in vitro and in vivo chemoresistance of tumor and leukemic cells.21,22 One might expect that a GST deficiency caused by the null genotype results in better response to chemotherapy. In this line, Stanulla et al23 showed a reduced risk of relapse in childhood B-cell acute lymphoblastic leukemia (ALL) patients having GSTM1 null or GSTT1 null genotype, whereas in the study of Chen et al,6 no impact of GST genotypes was seen on patient response to therapy and outcome. A study on GST genotypes and outcome in childhood AML was recently published, where the authors described a worse prognosis for GSTT1 null individuals, largely due to an increase of toxic deaths.24 We found a lower chemotherapy response rate and, consequently, a worse outcome in adults with AML and at least one GST null genotype. In keeping with our findings, the combined GST null genotype was associated with reduced responsiveness to chemotherapy, shorter progression-free interval, and poorer survival in patients with ovarian cancer.25 The deficiency of GST enzymes may cause higher levels of glutathione (GSH) because of reduced consumption of GSH in GST-catalyzed reactions. Accordingly, in addition to its role in detoxification, intracellular glutathione has also been implicated in the control of cell proliferation and apoptosis. By increasing glutathione levels, proliferation of T lymphocytes could be enhanced and apoptosis inhibited.26,27 This concept is supported by data from a recent report in which high intracellular GSH levels in lymphoid blasts were correlated with greater risk of relapse and reduced overall survival in childhood ALL.21 Interestingly, in the same study there was no relationship between glutathione levels and in vitro drug sensitivity.21 The prognostic importance of the GST genotype was supported by our multivariate analysis, where the GST genotype was an independent predictor for overall survival. In particular, GST genotyping could discriminate between favorable and unfavorable prognosis in the cytogenetically defined intermediate-risk group, which contains the majority of AML patients. Therefore, GST genotyping might complement diagnostic cytogenetics, thereby providing a more accurate risk assessment, which may ultimately permit a more refined treatment approach.
Submitted June 18, 2001; accepted May 30, 2002.
Supported by grants from Ministero dell' Universita' e della Ricerca Scientifica e Tecnologica (MURST) and Associazione Italiana per la Ricerca sul Cancro (AIRC).
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
Reprints: Maria Teresa Voso, Istituto di Ematologia, Universita' Cattolica S. Cuore, L go A. Gemelli, 100168 Rome, Italy; e-mail: mtvoso{at}rm.unicatt.it.
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© 2002 by The American Society of Hematology.
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E. Goekkurt, S.-E. Al-Batran, J. T. Hartmann, U. Mogck, G. Schuch, M. Kramer, E. Jaeger, C. Bokemeyer, G. Ehninger, and J. Stoehlmacher Pharmacogenetic Analyses of a Phase III Trial in Metastatic Gastroesophageal Adenocarcinoma With Fluorouracil and Leucovorin Plus Either Oxaliplatin or Cisplatin: A Study of the Arbeitsgemeinschaft Internistische Onkologie J. Clin. Oncol., June 10, 2009; 27(17): 2863 - 2873. [Abstract] [Full Text] [PDF] |
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G. Leone, L. Pagano, D. Ben-Yehuda, and M. T. Voso Therapy-related leukemia and myelodysplasia: susceptibility and incidence Haematologica, October 1, 2007; 92(10): 1389 - 1398. [Abstract] [Full Text] [PDF] |
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M. Voso, E Fabiani, F D'Alo', F Guidi, A Di Ruscio, S Sica, L Pagano, M Greco, S Hohaus, and G Leone Increased risk of acute myeloid leukaemia due to polymorphisms in detoxification and DNA repair enzymes Ann. Onc., September 1, 2007; 18(9): 1523 - 1528. [Abstract] [Full Text] [PDF] |
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A. Agudo, N. Sala, G. Pera, G. Capella, A. Berenguer, N. Garcia, D. Palli, H. Boeing, G. Del Giudice, C. Saieva, et al. No Association between Polymorphisms in CYP2E1, GSTM1, NAT1, NAT2 and the Risk of Gastric Adenocarcinoma in the European Prospective Investigation into Cancer and Nutrition. Cancer Epidemiol. Biomarkers Prev., May 1, 2006; 15(5): 1043 - 1045. [Full Text] [PDF] |
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P. Yang, J. O. Ebbert, Z. Sun, and R. M. Weinshilboum Role of the Glutathione Metabolic Pathway in Lung Cancer Treatment and Prognosis: A Review J. Clin. Oncol., April 10, 2006; 24(11): 1761 - 1769. [Abstract] [Full Text] [PDF] |
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S. Hohaus, A. Di Ruscio, A. Di Febo, G. Massini, F. D'Alo', F. Guidi, G. Mansueto, M. T. Voso, and G. Leone Glutathione S-transferase P1 Genotype and Prognosis in Hodgkin's Lymphoma Clin. Cancer Res., March 15, 2005; 11(6): 2175 - 2179. [Abstract] [Full Text] [PDF] |
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M. Wrensch, K. T. Kelsey, M. Liu, R. Miike, M. Moghadassi, K. Aldape, A. McMillan, and J. K. Wiencke Glutathione-S-Transferase Variants and Adult Glioma Cancer Epidemiol. Biomarkers Prev., March 1, 2004; 13(3): 461 - 467. [Abstract] [Full Text] |
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S. Hohaus, G. Massini, F. D'Alo', F. Guidi, R. Putzulu, A. Scardocci, A. Rabi, A. L. Di Febo, M. T. Voso, and G. Leone Association between Glutathione S-Transferase Genotypes and Hodgkin's Lymphoma Risk and Prognosis Clin. Cancer Res., August 1, 2003; 9(9): 3435 - 3440. [Abstract] [Full Text] [PDF] |
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