Genetic variants in SLC22A17 and SLC22A7 are associated with anthracycline-induced cardiotoxicity in children

AIM

To identify novel variants associated with anthracycline-induced cardiotoxicity and to assess these in a genotype-guided risk prediction model.

PATIENTS & METHODS

Two cohorts treated for childhood cancer (n = 344 and 218, respectively) were genotyped for 4578 SNPs in drug ADME and toxicity genes.

RESULTS

Significant associations were identified in SLC22A17 (rs4982753; p = 0.0078) and SLC22A7 (rs4149178; p = 0.0034), with replication in the second cohort (p = 0.0071 and 0.047, respectively). Additional evidence was found for SULT2B1 and several genes related to oxidative stress. Adding the SLC22 variants to the prediction model improved its discriminative ability (AUC 0.78 vs 0.75 [p = 0.029]).

CONCLUSION

Two novel variants in SLC22A17 and SLC22A7 were significantly associated with anthracycline-induced cardiotoxicity and improved a genotype-guided risk prediction model, which could improve patient risk stratification.

Pharmacogenomic prediction of anthracycline-induced cardiotoxicity in children

PURPOSE

Anthracycline-induced cardiotoxicity (ACT) is a serious adverse drug reaction limiting anthracycline use and causing substantial morbidity and mortality. Our aim was to identify genetic variants associated with ACT in patients treated for childhood cancer.

PATIENTS AND METHODS

We carried out a study of 2,977 single-nucleotide polymorphisms (SNPs) in 220 key drug biotransformation genes in a discovery cohort of 156 anthracycline-treated children from British Columbia, with replication in a second cohort of 188 children from across Canada and further replication of the top SNP in a third cohort of 96 patients from Amsterdam, the Netherlands.

RESULTS

We identified a highly significant association of a synonymous coding variant rs7853758 (L461L) within the SLC28A3 gene with ACT (odds ratio, 0.35; P = 1.8 × 10(-5) for all cohorts combined). Additional associations (P < .01) with risk and protective variants in other genes including SLC28A1 and several adenosine triphosphate-binding cassette transporters (ABCB1, ABCB4, and ABCC1) were present. We further explored combining multiple variants into a single-prediction model together with clinical risk factors and classification of patients into three risk groups. In the high-risk group, 75% of patients were accurately predicted to develop ACT, with 36% developing this within the first year alone, whereas in the low-risk group, 96% of patients were accurately predicted not to develop ACT.

CONCLUSION

We have identified multiple genetic variants in SLC28A3 and other genes associated with ACT. Combined with clinical risk factors, genetic risk profiling might be used to identify high-risk patients who can then be provided with safer treatment options.

Estimating arterial stiffness using transmission line model

An arterial stiffness index based on the transmission line model is defined. The parameters of the transmission line model are initially estimated using measured pressure, flow and aortic root diameter. Pressure is measured at the carotid using applanation tonometry. Flow is measured using Doppler at the ascending aorta. Aortic root diameter is measured using 2-D echocardiography. The initial estimates are then refined using grey-box identification. The resulting estimate of the distributive compliance of the transmission line model is proposed to be an arterial stiffness index. Similar to the Windkessel compliance, this index describes the global stiffness. However, it is based on a more realistic 1-D model that can simulate wave propagation and wave reflection.

Is the nuchal index increased in fetuses with congenital structural heart defects?

OBJECTIVES

To determine if the Nuchal index (NIx) is increased in euploid fetuses with structural congenital heart defects (CHD).

METHODS

Euploid fetuses with CHD between 18 and 24 weeks gestation were identified. The next fetus meeting the same criteria with a normal fetal echocardiogram were selected as a control. The NIx [(mean nuchal thickness /mean biparietal diameter) x 100] and cardiac axis (CA; degrees) were calculated for each fetus. Standard descriptive tests and two-tailed t test were used.

RESULTS

The NIx in the abnormal (n = 20) and control (n = 20) groups were 9.10 (2.35) and 7.54 (p = 0.04) and CA was 55.8 degrees and 48.6 degrees (p = 0.02), respectively.

CONCLUSIONS

The NIx and CA were significantly different in fetuses with CHD. A prospective study to confirm these findings and determine clinical utility is warranted.

Left ventricular systolic and diastolic function after two-stage anatomic correction of transposition of the great arteries

Anatomic repair of transposition of the great arteries (TGA) has been developed because of concerns about right ventricular function after atrial repair by the Mustard or the Senning technique. This study assessed left ventricular systolic and diastolic function in three patients after two-stage anatomic repair. Two patients had a ventricular septal defect (one with coarctation), and the third patient had right ventricular dysfunction precluding atrial repair. All had pulmonary artery banding. The mean ages at the time of repair and catheterization were 2.75 and 4.9 years, respectively. The control group included 10 patients with insignificant or no cardiac disease. At cardiac catheterization the group with TGA had a higher mean end-diastolic volume index (110.9 +/- 4.74 ml/m2) compared to normal subjects (79.1 +/- 14.55; p less than 0.001), mean end-systolic volume index (37.3 +/- 3.69 vs 22.7 +/- 4.42; p less than 0.001), mass index (101.0 +/- 16.9 vs 68.2 +/- 12.34; p = 0.038), and stroke volume index (73.6 +/- 3.52 vs 56.5 +/- 12.1; p = 0.0027). The ejection fractions, end-diastolic and peak systolic pressures, and stresses were not different. There was no difference in the relationship between the mean rate-corrected velocity of circumferential fiber shortening and end-systolic stress for the group with TGA, but myocardial stiffness was markedly elevated (29.5 +/- 1.84 vs 10.8 +/- 2.20; p less than 0.001). Thus, this study found abnormalities of left ventricular size after two-stage anatomic repair of TGA in this group of patients with TGA.(ABSTRACT TRUNCATED AT 250 WORDS)

Premature rupture of membranes and effects of prophylactic antibiotics

A series of 100 infants born after prolonged rupture of membranes was studied to evaluate the risk of infection to the infant due to this circumstance alone, and to assess the effect of prophylactic antibiotics in its prevention. Evidence of bacterial colonization at birth was limited to 6 cases and no clinical infection ensued. Neonatal infection was uniformly low but the administration of antibiotics led to clinical candidiasis in 18% and the development of a replacement flora of fungi in the intestinal tract in 70%. It is concluded that the routine administration of prophylactic antibiotics to the infant born in these circumstances is unnecessary and potentially hazardous.