Background: Asparaginase-associated pancreatitis (AAP) is a well-known toxicity of childhood acute lymphoblastic leukemia (ALL) therapy. Recent multi-trial group phenotyping of 465AAP caseshas documented severe complications to AAP, including 8% risk of needing assisted mechanical ventilation, 26% risk of developing pancreatic pseudocysts and 9% risk of developing persisting diabetes (Wolthers et al. Lancet Oncology, 2017) . Investigation of host genome variation associated with AAP has been limited by varying phenotype definition, inclusion criteria and small study sizes.

Objectives and Methods: To investigate genetic variants associated with risk of developing AAP, this genome-wide association study reports data on 1544 children (1.0−17.9 years) from 10 ALL trial groups treated with ALL from January 2000−January 2016. The Ponte di Legno toxicity working group consensus definition (Schmiegelow et al. Lancet Oncology, 2016) was used to diagnose AAP: At least two of i) amylase, pancreatic amylase, or pancreatic lipase >3x upper normal limit (UNL), ii) abdominal pain, iii) imaging compatible with AAP. Controls included children treated for ALL with verified completion of intended asparaginase therapy, 78% of whom (1024/1320) received at least 8 injections of PEG-asparaginase without developing AAP. Germline DNA obtained after clinical remission was genotyped on Illumina Infinium Omni2.5exome-8 BeadChip arrays. Association analyses were done in PLINK and annotation in Ensembl.

Results: Of 1564 patients passing genotype quality control, 244 had AAP. 205 of 244 (84%) of cases and 1185/1320 (90%) of controls were of European ancestry. Median age was 8.1 years (IQR 4.3−13.1) and 5 (IQR: 3−9) for cases and controls, respectively. After filtering, 1401908 single nucleotide polymorphisms (SNPs) with a minor allele frequency above 1% were analyzed. In logistic regression analysis, adjusting for age and ancestry, the variant rs62228256 (reference allele=C, minor allele=T (C>T)) on 20q13.2 had the strongest association to AAP (OR=3.75; 95% CI 2.33−6.04; p=5.2∙10-8). rs62228256 is located in a non-coding region without known regulatory effects. rs13228878 (A>G; OR=0.61; 95% CI 0.5−0.76; p=7.1∙10-6) and rs10273639 (C>T; OR=0.62; 95% CI 0.5−0.77; p =1.1∙10-5) were among the top 30 SNPs most significantly associated to AAP. They are in high linkage disequilibrium (R2=0.94) and located in the PRSS1-PRSS2 locus on chromosome 7. The rs13228878 A risk allele was not associated with level of amylase (p=0.1) or lipase (p=0,68) at diagnosis of AAP, age at diagnosis of AAP (p=0.63), or risk of pseudocysts (p=0.78). Using identical diagnostic criteria for pancreatitis, the major C allele in rs10273639 has been associated with pancreatitis risk in adults (Whitcomb et al. Nature Genetics, 2012; Masson et al. Gut, 2017) with identical risk allele and similar odds ratios. PRSS1 and PRSS2 encode cationic and anionic trypsinogen, respectively. rs10273639 is an expressive quantitative locus for PRSS1 and the C risk-variant is associated with elevated expression of trypsinogen in pancreatic tissue. Gain of function mutations in PRSS1, known from hereditary pancreatitis, lead to increased autoactivation, increased intra-acinar trypsin levels, and increased risk of auto-digestion leading to pancreatitis. Further investigation of previously validated SNPs known to regulate trypsin activation gave the following results for associations with AAP; rs17107315 in pancreatic secretory trypsin inhibitor (SPINK1; OR=2.87; 95% CI 1.36−5.8; p=4∙10-3), rs10436957 in chymotrypsin C (CTRC ; OR=0.69; 95% CI 0.53−0.89; p=5∙10-3) and rs4409525 in Claudin-2 (CLDN2 ; OR=1.41; 95% CI 1.08−1.83; p=1∙10-2). In total, 207 out of 244 cases were homozygous for the risk allele in rs13228878 (n=104), rs17107315 (n=1), rs10436957 (n=165) and/or rs4409525 (n=16). However, no significant additive effect of having more than one risk allele was found.

Conclusion: Children who develop AAP possess the same pancreatitis risk variants as adults with non-asparaginase associated pancreatitis. This shared genetic disposition may facilitate research into pathogenesis and identification of effective interventions towards AAP.

Disclosures

No relevant conflicts of interest to declare.

Topics:
acute lymphocytic leukemia, asparaginase, child, genetics, pancreatitis, toxic effect, trypsin, genes, amylases, trypsinogen

Author notes

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Asterisk with author names denotes non-ASH members.

© 2017 by The American Society of Hematology
2017
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