Manganese superoxide dismutase gene coding region polymorphisms lack clinical incidence in general population

Two functional polymorphisms within the manganese superoxide dismutase (MnSOD) gene have been reported to lead to increased oxidative stress damage. The MnSOD 58T > C single nucleotide polymorphism (SNP) within exon 3 changes isoleucine to threonine, leading to decreased thermal stability and reduced enzymatic activity in vivo and in vitro. The MnSOD 60C > T polymorphism within exon 3 changes leucine to phenylalanine, rendering the protein sensitive to redox regulation by intracellular thiols. Thus, the goal of this study was to evaluate the 58T > C and 60C > T MnSOD polymorphisms in a large case-control study. Taqman allelic discrimination assays were developed to identify the 58T > C and 60C > T SNPs in exon 3. Two hundred and eight lung cancer cases and 141 controls were evaluated for these two SNPs, and all 349 subjects were of the wild-type homozygous genotype for both 58C and 60T in exon 3. This study suggests that although the 58T > C and 60C > T polymorphisms reduce MnSOD enzymatic activity, these polymorphisms were not identified in the present case-control study population.

Incidence and clinical implications of GATA1 mutations in newborns with Down syndrome

Somatic mutations in the GATA1 gene are present in almost all cases of Down syndrome (DS)–associated acute megakaryoblastic leukemia (AMKL) and transient leukemia (TL). An in utero origin of the GATA1 mutation suggests it is an early leukemogenic event. To determine the detectable incidence and clinical relevance of GATA1 mutations in DS newborns, we screened Guthrie cards from 590 DS infants for mutations in the GATA1 gene. Twenty-two (3.8%) of 585 evaluable infants harbored a predicted functional GATA1 mutation; 2 were identified exclusively within intron 1. Hispanic newborns were 2.6 times more likely to have a mutated GATA1 gene than non-Hispanics (P = .02). Two newborns with a GATA1 mutation subsequently developed AMKL, and none of the infants without a functional GATA1 mutation were reported to have developed leukemia. In addition to screening for TL, a GATA1 mutation at birth might serve as a biomarker for an increased risk of DS-related AMKL.

Lung cancer survival and functional polymorphisms in MBL2, an innate-immunity gene

BACKGROUND

The relationship among chronic inflammation, innate immunity, and cancer is well established. Mannose-binding lectin (MBL) is a key player in innate immunity. Five polymorphisms in the promoter and first exon of the MBL2 gene alter the expression and function of MBL in humans and are associated with inflammation-related disease susceptibility. These five polymorphisms create six well-characterized haplotypes that result in lower (i.e., LYB, LYC, HYD, and LXA) or higher (i.e., HYA and LYA) serum MBL concentrations. We investigated whether survival of patients with lung cancer was associated with these polymorphisms.

METHODS

We used a multivariable Cox proportional hazards model to study the association between MBL2 polymorphisms and their haplotypes and diplotypes in 558 white and 173 African American patients with non-small-cell lung cancer in the Baltimore, MD, area and lung cancer mortality. Smoking history and race were obtained from interviews, tumor stage was obtained from medical records, and cause of death was obtained from the National Death Index. All statistical tests were two-sided.

RESULTS

We found a statistically significant association between the X allele of the promoter Y/X polymorphism (which results in a lower serum MBL concentration) and improved lung cancer survival among white patients (risk ratio [RR] of death from lung cancer with X/X or X/Y genotype compared with Y/Y genotype = 0.61, 95% confidence interval [CI] = 0.46 to 0.81) but not among African American patients (RR = 1.11, 95% CI = 0.69 to 1.77). The associations among white patients were strongest in heavy smokers and were independent of stage. We also found a statistically significant interaction between the Y/X polymorphism and race for lung cancer survival (P(interaction) = .019). The MBL2 LXA haplotype and XA/B diplotype, which are also associated with low serum MBL levels, were statistically significantly associated with improved lung cancer survival among white patients.

CONCLUSION

The functional Y/X polymorphism of the innate-immunity gene MBL2 and MBL2 haplotypes and diplotypes appear to be associated with lung cancer survival among white patients.

MDM2 SNP309 and SNP354 are not associated with lung cancer risk

A single nucleotide polymorphism (SNP) in the MDM2 promoter (a T to G exchange at nucleotide 309) has been found to be associated with tumor formation. Publication of this null report is important because an association between MDM2 SNP309 and lung cancer was previously reported in two independent studies. Our findings suggest that MDM2 SNP309 is not a strong factor in lung carcinogenesis. In addition, this is the first MDM2 SNP309 report on a population consisting of Caucasians in the United States and African-Americans. A strength of the study design is that the controls consist of both population and hospital controls.

GATA1 as a new target to detect minimal residual disease in both transient leukemia and megakaryoblastic leukemia of Down syndrome

Acquired mutations in exon 2 of the GATA1 gene are detected in most Down syndrome (DS) patients with transient leukemia (TL) and acute megakaryoblastic leukemia (AMKL). We sought to determine if GATA1 mutations can be utilized as markers for minimal residual disease (MRD). GATA1 mutations were screened by SSCP analysis and sequenced. Using GATA1 mutation-specific primers, follow-up bone marrow samples from four patients were assayed by quantitative PCR. We show that molecular monitoring of GATA1 mutations is possible in Down syndrome patients with TL and AMKL, and GATA1 could be a stable marker for MRD monitoring.

Detection of central nervous system leukemia in children with acute lymphoblastic leukemia by real-time polymerase chain reaction

Accurate detection of central nervous system (CNS) involvement in children with newly diagnosed acute lymphoblastic leukemia (ALL) could have profound prognostic and therapeutic implications. We examined various cerebrospinal fluid (CSF) preservation methods to yield adequate DNA stability for polymerase chain reaction (PCR) analysis and developed a quantitative real-time PCR assay to detect occult CNS leukemia. Sixty CSF specimens were maintained in several storage conditions for varying amounts of time, and we found that preserving CSF in 1:1 serum-free RPMI tissue culture medium offers the best stability of DNA for PCR analysis. Sixty CSF samples (30 at diagnosis and 30 at the end of induction therapy) from 30 children with ALL were tested for CNS leukemic involvement by real-time PCR using patient-specific antigen receptor gene rearrangement primers. Six of thirty patient diagnosis samples were PCR-positive at levels ranging from 0.5 to 66% leukemic blasts in the CSF. Four of these patients had no clinical or cytomorphological evidence of CNS leukemia involvement at that time. All 30 CSF samples drawn at the end of induction therapy were PCR-negative. The data indicate that real-time PCR analysis of CSF is an excellent tool to assess occult CNS leukemia involvement in patients with ALL and can possibly be used to refine CNS status classification.

Tetrasomy 21 transient leukemia with a GATA1 mutation in a phenotypically normal trisomy 21 mosaic infant: case report and review of the literature

Infants with constitutional trisomy 21 are at increased risk of developing transient and acute megakaryoblastic leukemia (AMKL). Mutations in GATA1 have been identified in trisomy 21 patients with AMKL, and this lesion is thought to be an initial event by virtue of its presence during transient leukemia. Transient leukemia is also observed in phenotypically normal infants albeit much less commonly so. Almost all these infants are mosaic for trisomy 21, and the clinical course of transient leukemia recapitulates that observed in constitutional trisomy 21. We report a phenotypically normal infant with tetrasomy 21 transient leukemia, GATA1 mutation within exon 2, and trisomy 21 mosaicism restricted to the hematopoietic tissue. Two years after diagnosis, low levels of trisomy 21 persisted in the peripheral blood, which resolved 2.5 years after diagnosis. The GATA1 mutation was not detected at last follow-up. The literature review identified 32 phenotypically normal infants with transient leukemia. Ninety-one percent (29 of 32) were observed and three received chemotherapy at diagnosis of transient leukemia. Nineteen percent (6 of 32) developed acute leukemia, and four continued in remission (two died). Transient leukemia in trisomy 21 mosaicism recapitulates the condition observed in constitutional trisomy 21 at the biological and clinical levels. Infants should be followed for the development of acute leukemia.

Real-time quantitative PCR: standardized detection of minimal residual disease in pediatric acute lymphoblastic leukemia. Polymerase chain reaction

PURPOSE

To develop a standardized real-time polymerase chain reaction (PCR) method of quantifying minimal residual disease (MRD) in patients with pre-B acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

In a series of 24 follow-up bone marrow (BM) samples in 11 patients (14 clonal markers), we performed real-time PCR assays using one consensus and one clone-specific primer for each marker. The markers analyzed included immunoglobulin heavy chain (IgH), T-cell receptor (TCR) and TEL-AML1 rearrangements.

RESULTS

We achieved a detection limit of 3.3 x 10(-5) +/- 1.2 x 10(-5) and an accurate quantitation (r = -0.99) limit of 2.0 x 10(-4) +/- 8.8 x 10(-5) blasts. Both inter- and intra-assay reproducibility were exceptional. Additionally, we found comparable results to those of a "gold standard" limiting-dilution PCR assay (r = 0.62).

CONCLUSIONS

The IgH, TCR and TEL-AML1 markers can be used as targets by real-time PCR under the same cycling profile, allowing quantitation of MRD in more 95% of patients with pre-B ALL. This standardized, real-time PCR technique should simplify monitoring MRD in clinical trials.

TEL-AML1 fusion precedes differentiation to pre-B cells in childhood acute lymphoblastic leukemia

The TEL-AML1 gene fusion results from a karyotypically cryptic t(12;21) translocation, the most common genetic abnormality in pediatric acute lymphoblastic leukemia (ALL). The presence of the TEL-AML1 fusion in utero, its protracted latency to overt leukemia, and secondary loss of the untranslocated TEL suggest it is an initiating event. Sequences of the TEL-AML1 genomic breakpoint and the immunoglobulin heavy chain (IgH) and/or T-cell receptor (TCR) gene rearrangements were characterized in four pediatric pre-B ALL patients. Analysis of these markers in relapsed patients revealed that immunophenotypically and cytogenetically distinct, and clonally unrelated antigen receptor leukemic cell populations harbored the same initiating TEL-AML1 molecular abnormality. Furthermore, TEL-AML1-positive cells persisted during remission even in the absence of detectable clone-specific IgH and TCR markers. We demonstrate that the TEL-AML1 translocation can occur in vivo during B-cell development before rearrangement of the IgH and TCR genes. We propose, in some cases, that the TEL-AML1 translocation occurs in a stem or B progenitor cell, and that recurrent TEL-AML1-positive pre-B ALL represents a de novo-transformed population that retains the same diagnostic initiating event.

Site-specific translocation and evidence of postnatal origin of the t(1;19) E2A-PBX1 fusion in childhood acute lymphoblastic leukemia

The t(1;19) translocation yields a fusion between E2A and PBX1 genes and occurs in 5% of acute lymphoblastic leukemia in children and adults. We used chromosomal translocations and Ig heavy chain (IGH)/T cell antigen receptor (TCR) rearrangements to develop an understanding of the etiology and natural history of this subtype of leukemia. We sequenced the genomic fusion between E2A and PBX1 in 22 preB acute lymphoblastic leukemias and two cell lines. The prenatal origin of the leukemia was assessed in 15 pediatric patients by screening for the clonotypic E2A-PBX1 translocation in neonatal blood spots, or Guthrie cards, obtained from the children at the time of birth. Two patients were determined to be weakly positive for the fusion at the time of birth, in contrast to previously studied childhood leukemia fusions, t(12;21), t(8;21), and t(4;11), which were predominantly prenatal. The presence of extensive N-nucleotides at the point of fusion in the E2A-PBX1 translocation as well as specific characteristics of the IGH/TCR rearrangements provided additional evidence for a postnatal, preB cell origin. Intriguingly, 16 of 24 breakpoints on the 3.2-kb E2A intron 14 were located within 5 bp, providing evidence for a site-specific recombination mechanism. Breakpoints on the 232-kb PBX1 intron 1 were more dispersed but highly clustered proximal to exon 2. In sum, the translocation breakpoints displayed evidence of unique temporal, ontological, and mechanistic formation than the previously analyzed pediatric leukemia translocation breakpoints and emphasize the need to differentiate cytogenetic and molecular subgroups for studies of leukemia causality.

Cholesterol limits estrogen uptake by liposomes and erythrocyte membranes

Multilamellar vesicles (MLV) were prepared from phospholipids with and without cholesterol in equimolar amounts and [4-14C]estradiol. Unincorporated estrogen was removed by petroleum ether extraction or by aqueous buffer washes. In either case, cholesterol-containing vesicles incorporated one-half the estradiol as vesicles without sterol. Addition of estradiol to preformed vesicles followed by buffer washes showed that vesicles without cholesterol invariably retained more estradiol than those with the sterol. Reduction of the cholesterol content to one-half increased estradiol incorporation. The pattern of estradiol removal from MLV with successive buffer washes indicated that much of the steroid associated with cholesterol-containing vesicles was superficially bound to the membrane but vesicles without cholesterol incorporated the estrogen into the bilayer structure. To test the role of cholesterol in limiting the uptake of an estrogen by cells, right-side out resealed ghosts of ox erythrocytes were prepared. They were partially depleted of cholesterol by exposure to small unilamellar vesicles of dioleoylphosphatidyl choline. A decrease in cholesterol content correlates with an increase in estradiol uptake by red cell ghosts. The experiments described point to a central role of cholesterol in limiting the uptake of steroids. The loss of cholesterol of steroid producing cells caused by tropic hormones may be key to their mode of action in promoting secretion of steroid hormones. Likewise, the long-term genomic responses of steroid target cells may depend upon their cholesterol content and the ease by which the steroid can penetrate the membrane barrier.