Association of anthracycline-related cardiac histological lesions with NADPH oxidase functional polymorphisms

OBJECTIVE

Treatment with anthracyclines may cause cardiac dysfunction, but the sequence of anthracycline-induced heart lesions has been incompletely characterized. NADPH oxidase, a key mediator of oxidative cardiac damage and remodeling, modulates anthracycline clinical cardiotoxicity. Our aim was to determine which cardiac histological lesions are specifically induced by anthracycline treatment and to investigate the role of NADPH functional genetic polymorphisms in their development.

PATIENTS AND METHODS

Using a retrospective case-control design, we evaluated cardiac histological lesions and NADPH genotype (polymorphisms rs1883112, rs4673, and rs13058338) in 97 consecutive decedents with a cancer diagnosis (48 treated with anthracyclines).

RESULTS

Myocytolysis (60%), patched myocardial necrosis (19%), and myocardial fibrosis (diffuse and patched; 62% and 23%, respectively) were associated with anthracycline treatment. In patients receiving anthracyclines, NADPH oxidase polymorphism rs4673 protected against focal myocardial necrosis (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.20-0.63) whereas rs1883112 was strongly associated with cardiac fibrosis (OR, 5.11; 95% CI, 1.59-16.43), which was present in all homozygotes.

CONCLUSION

Anthracyclines induce a cardiac remodeling pattern characterized by interstitial or patched fibrosis. The contribution of the functionally relevant NADPH polymorphisms rs1883112 and rs4673 to anthracycline-related heart lesions provides a plausible explanation for their modulation of cardiotoxicity. If confirmed, these findings may lead to better individualized strategies for early detection and prevention of anthracycline cardiotoxicity.

Clinical and genetic determinants of anthracycline-induced cardiac iron accumulation

BACKGROUND

The involvement of iron in anthracycline cardiotoxicity is supported by extensive experimental data, and by the preventive efficacy of dexrazoxane, an iron chelator. However, no clinical evidence of anthracycline-induced cardiac iron accumulation is available and the influence of previous iron overload or of genetic factors in human-induced heart disease is largely unknown. Our aim was to test the hypothesis that anthracyclines increase iron heart concentration and that HFE genotype modulates this iron deposit.

METHODS

We retrospectively evaluated cardiac events, cardiac iron and HFE genotype in 97 consecutive necropsies from patients with solid and hematological neoplasms. Heart and liver iron concentration was determined by atomic absorption spectroscopy. HFE gene mutations (C282Y and H63D) linked to hereditary hemochromatosis were analyzed by Fluorescence Resonance Energy Transfer (FRET) genotyping.

RESULTS

Heart iron concentration was increased in cases treated with a cumulative doxorubicin dose greater than 200mg/m(2) (490 vs 240 μg/g; p=0.01), independently of liver iron load or transfusion history. HFE mutated haplotypes 282C/63D (p=0.049) and 282Y/63H (p=0.027) were associated to higher cardiac iron deposits. The haplotype C282Y-Y/H63D-H interacted with anthracyclines for increasing cardiac iron load. In a multivariate linear regression analysis both HFE genotypes and anthracyclines contributed to heart iron concentration (R(2)=0.284).

CONCLUSIONS

Our data support the occurrence of an HFE-modulated heart iron accumulation in individuals treated with anthracyclines, independently of systemic iron load. If prospectively confirmed, iron-related parameters might be useful as predictive factors for anthracycline cardiotoxicity.

Functional consequences of the prothrombotic SERPINC1 rs2227589 polymorphism on antithrombin levels

Genetic factors involved in the interindividual variability of antithrombin have not been identified. We studied two polymorphisms of the gene coding for antithrombin (SER-PINC1) in 298 Spanish Caucasian blood donors: rs3138521, a DNA length polymorphism located on the promoter region and rs2227589, a SNP located on intron 1 that has been described as a mild thrombotic risk factor. We detected a complete linkage disequilibrium between these polymorphisms (D'=0.999). The rs3138521 polymorphism has no functional consequences. However, the rs2227589 SNP significantly associated with plasma anti-FXa activity and antithrombin levels: carriers of the A allele had slightly but significantly lower anticoagulant activity and levels than GG subjects (97.0+/-7.3% vs. 94.6+/-8.4%; p=0.032; 99.5+/-5.8% vs. 94.8+/-5.6%; p=0.001; respectively). Our results identified a functional effect of the rs2227589 polymorphism not explained by its linkage with the promoter polymorphism that support the moderate thrombotic risk associated with the A allele.

Glucocorticoid resistance in a multiple myeloma cell line is regulated by a transcription elongation block in the glucocorticoid receptor gene (NR3C1)

Glucocorticoid (GC) effects are mediated by the glucocorticoid receptor (GR). Several studies have demonstrated that a lower number of receptors per cell were associated with poor GC response. The regulation of GR expression is complex; the levels of GR can be autologously regulated by its ligand and also by transcriptional, post-transcriptional and post-translational mechanisms. Using three human myeloma cell lines that parallel the development of GC resistance, this work describes the mechanism involved in the downregulation of GR expression. The decreased expression was neither due to mutations in the gene encoding GR, NR3C1, nor due to methylation of the promoters. A gradual decrease in NR3C1 transcripts was seen during the development of resistance, the level of expression of exon 1 to 2 RNA fragments remained the same in sensitive and resistant cell lines but a chromatin immunoprecipitation assay demonstrated that RNA polymerase II, detectable throughout exon 2 to 3 in the sensitive cells, was undetectable on exon 3 in the resistant variant, suggesting lower or no transcription at this site. These studies demonstrated that downregulation of NR3C1 mRNA in a resistant cell line involves a block to transcriptional elongation within intron B of NR3C1. This block may represent an important element in the regulation of GR expression.

Glucocorticoid receptor transcriptional isoforms and resistance in multiple myeloma cells

Although glucocorticoids play an important role in the treatment of multiple myeloma, some patients do not respond or develop resistance. The glucocorticoid receptor (GR), a single gene, mediates the effects of glucocorticoids. Using a model system of a multiple myeloma cell line sensitive to glucocorticoids and its early and late resistant variants, we have analyzed mutations in the GR gene, detected the presence of different transcriptional isoforms, quantified their levels of expression, and identified the promoters that regulate their expression. Levels of GR transcripts were comparable with the expression of total GR protein. Development of resistance correlates with an overall reduction in GR mRNA levels. This decrease in GR levels is neither due to mutation of the gene nor due to methylation. GRalpha is the predominant isoform in the sensitive cell line decreasing in expression in the early resistant cells and virtually undetectable in late resistant cells. GR-P is expressed at equivalent levels in both sensitive and early resistant cells, whereas in the late resistant cells, GR-P is the predominant isoform. GR-A is only expressed in the early resistant cell line. GRbeta is the least expressed isoform in all cell lines. Interestingly, the level of expression of exon 1-exon 2 RNA fragments remains similar in sensitive and resistant cell lines. Resistant cells became sensitive to glucocorticoids after GRalpha transfection. In conclusion, we show different patterns of expression of the GR isoforms and provide evidence that a decline in the expression of GRalpha may be associated with development of resistance.

A missense mutation in gamma-glutamyl carboxylase gene causes combined deficiency of all vitamin K-dependent blood coagulation factors

To identify potential mutations in the gamma-glutamyl carboxylase gene, the sequence of all exons and intron/exon borders was determined in 4 patients from a consanguineous kindred with combined deficiency of all vitamin K-dependent procoagulants and anticoagulants and results were compared with normal genomic sequence. All 4 patients were homozygous for a point mutation in exon 9 that resulted in the conversion of an arginine codon (CTG) to leucine codon (CGG) at residue 394. Screening of this mutation based on introduction of Alu I site in amplified fragment from normal allele but not from the mutated allele showed that 13 asymptomatic members of the kindred were heterozygous for the mutation. The mutation was not found in 340 unrelated normal chromosomes. The segregation pattern of the mutation which is the first reported in the gamma-glutamyl carboxylase gene fits perfectly with phenotype of the disorder and confirms the suggested autosomal recessive pattern of inheritance of combined deficiency of all vitamin K-dependent procoagulants and anticoagulants in this kindred. The mutated carboxylase protein expressed in Drosophila cells was stable but demonstrated threefold reduced activity compared with WT carboxylase, confirming that the L394R mutation results in a defective carboxylase.