TABLE 6.

Genetic susceptibility to anthracycline cardiomyopathy/cardiotoxicity (ACT)

Gene / Variant	Methods	Results	Comment / Conclusion
RARG36 The retinoic acid receptor (RAR) is a nuclear receptor that can also act as a transcription factor. RAR is activated by both all-trans retinoic acid and 9-cis retinoic acid. There are three RARs: RARα, RARβ, and RARγ, encoded by the RARA RARB and RARG genes, respectively.	• Genome-wide association study in 280 CCS of European ancestry with independent replication in similarly treated cohorts of 96 European and 80 non-European CCS	• Identified a nonsynonymous variant (rs2229774, p.Ser427Leu) in RARG highly associated with ACT [P=5.9 × 10−8, OR 4.7 (95%CI 2.7–8.3)].	• RARG may confer susceptibility to ACT in CCSs. • Variant alters RARG function, leading to derepression of the key ACT genetic determinant Top2b
UGT1A6 and SLC28A337 • UGT1A6: UDP-glucuronosyltransferase 1–6 is an enzyme of the glucuronidation pathway that transforms small lipophilic molecules into watersoluble, excretable metabolites. This gene is part of a complex locus that encodes several UDP-glucuronosyltransferases. UDP-glucuronosyltransferase is also responsible for the inactivation of drugs. • SLC28A3: The human concentrative nucleoside transporter CNT3 (SLC28A3) plays an important role in mediating the cellular entry of a broad array of physiologic nucleosides and synthetic anticancer nucleoside analog drugs	• 23 variants tested for association with ACT in an independent cohort of 218 patients	• Confirmed association of rs17863783 in UGT1A6 and ACT (P = 0.0062, OR 7.98). • Additional evidence for association of rs7853758 (P = 0.058, OR 0.46) and rs885004 (P = 0.058, OR 0.42) in SLC28A3 was found (combined P=1.6 × 10−5 and P=3.0 × 10−5, respectively).	• Validation of variants in SLC28A3 and UGT1A6 as genetic markers predictive of ACT in CCSs • An improved prediction model using replicated genetic variants as well as clinical factors discriminated significantly better between cases and controls than clinical factors alone
SLC22A17 and SLC22A738 • SLC22A17: Polyspecific organic cation transporter in liver, kidney, intestine, and other organs. Critical for eliminating endogenous small organic cations and wide array of drugs and environmental toxins. One of three similar cation transporter genes located in a cluster on chromosome 6. • SLC22A7: Involved in sodiumindependent transport and excretion of organic anions some potentially toxic. It’s a membrane protein localized to basolateral membrane of kidney. Alternatively, spliced transcript variants encoding different isoforms exist	• Two cohorts treated for childhood cancer (n = 344 and 218, respectively) were genotyped for 4578 SNPs in drug ADME and toxicity genes	• Significant associations 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)	• Genetic variants in SLC22A17 and SLC22A7 were associated with ACT in CSSs • SLC22A17 and SLC22A7 variants improved a genotype-guided risk prediction model, which could improve patient risk stratification
CELF439 • CUGBP Elav-like family member 4 (CELF4) also known as bruno-like protein 4 (BRUNOL4) is encoded by the CELF4 • Members of this protein family regulate pre-mRNA alternative splicing and may also be involved in mRNA editing, and translation.	• Genome-wide association study in CCSs with/without cardiomyopathy. SNPs surpassing a prespecified threshold for statistical significance were independently replicated	• No SNP was marginally associated with ACT • SNP rs1786814 on CELF4 gene passed significance cutoff for gene-environment interaction (Pge=1.14 × 10−5). In patients with A allele, cardiomyopathy infrequent and not dose related • If exposed to >300 mg/m2 anthracyclines, rs1786814 GG genotype conferred 10.2-fold (95%CI, 3.8- to 27.3-fold; P <.001) cardiomyopathy risk compared with GA/AA genotypes and exposure ≤300 mg/m2 • Gene-environment interaction successfully replicated in independent set of ACT cases	• Modifying effect of a polymorphism of CELF4 (rs1786814) on the dose-dependent association between anthracyclines and cardiomyopathy; possibly through pathway involving expression of abnormally spliced TNNT2 variants • Coexistence of ≥1 cTnT variant results in temporally split myofilament response to calcium, and decreased contractility • Analysis of TNNT2 splicing variants in healthy human hearts suggested an association between the rs1786814 GG genotype and coexistence of ≥1 TNNT2 splicing variant (90.5% GG v 41.7% GA/AA; P=0.005)
HAS340 HAS3 (Hyaluronan 3): Encodes a protein involved in synthesis of hyaluronic acid, a major constituent of the extracellular matrix. This gene is a member of the NODC/HAS gene family. Compared to the proteins encoded by other members of this gene family, this protein appears to be more of a regulator of hyaluronan synthesis.	• Used two-stage design, to investigate host susceptibility to ACT by using the ITMAT/Broad CARe cardiovascular SNP array to profile common SNPs in 2,100 genes considered relevant to de novo cardiovascular disease	• Using matched case-control design (93 cases, 194 controls), identified a common SNP, rs2232228, in HAS3 gene that exerts a modifying effect on anthracycline dose-dependent cardiomyopathy risk (P=5.3 × 10−7) • Among individuals with rs2232228 GG genotype, cardiomyopathy infrequent and not dose related • In individuals exposed to >250 mg/m2 anthracyclines, rs2232228 AA genotype conferred 8.9-fold (95%CI, 2.137.5-fold; P=0.003) increased risk of cardiomyopathy compared with GG genotype • HAS3 mRNA levels in healthy hearts lower among individuals with AA compared with GA genotypes (P=0.09)	• HAS3 produces hyaluronic acid a ubiquitous component of the extracellular matrix that plays role in tissue remodeling and is known to reduce ROS-induced cardiac injury. • High cardiomyopathy risk associated with AA genotype could be due to inadequate remodeling and/or inadequate protection of the heart from ROSmediated injury after high anthracycline exposure
CBR341 CBR3: Carbonyl reductases (CBRs) catalyze reduction of anthracyclines to cardiotoxic alcohol metabolites. Polymorphisms in CBR1 and CBR3 influence synthesis of these metabolites.	• 170 CCSs with cardiomyopathy (patient cases) were compared with 317 survivors with no cardiomyopathy (controls; matched on cancer diagnosis, year of diagnosis, length of follow-up, and race/ethnicity) using conditional logistic regression techniques.	• Dose-dependent association observed between cumulative anthracycline exposure and cardiomyopathy risk: – 0 mg/m2: reference; – 1 to 100 mg/m2: OR 1.65 – 101 to 150 mg/m2: OR 3.85; 151 to 200 mg/m2: OR 3.69; – 201 to 250 mg/m2 OR 7.23; – 251 to 300 mg/m2: OR 23.47; – >300 mg/m2: OR 27.59; P(trend) < .001 • No increased risk of cardiomyopathy after exposure to low- to moderate-dose ANTH (1–250 mg/m2) with variant A allele (CBR1:GA/AA and/or CBR3:GA/AA) • Exposure to low- to moderate-dose anthracyclines increased cardiomyopathy risk among individuals with CBR3 V244M homozygous G genotypes (CBR3:GG), when compared with individuals with CBR3:GA/AA genotypes unexposed to anthracyclines (OR 5.48; P=0.003), as well as exposed to low- to moderate-dose anthracyclines (OR 3.30; P=0.006) • <250 mg/m2 anthracyclines associated with increased cardiomyopathy risk, irrespective of CBR genotype status	• ACT risk increased at doses as low as 101 to 150 mg/m2 • Homozygosis for G allele in CBR3 contributes to increased cardiomyopathy risk with low- to moderate-dose anthracyclines, such that there seems to be no safe dose for patients homozygous for the CBR3 V244M Gallele

Abbreviations: 95%CI, 95% confidence interval; Anth, anthracycline; ACT, anthracycline-induced cardiotoxicity; OR, odds ratio; ROS, reactive oxygen species; SNPs, single-nucleotide polymorphisms