L-asparaginase-induced pancreatitis in children with acute lymphoblastic leukemia: is allopurinol protective?

General control nonderepressible 2 deletion predisposes to asparaginase-associated pancreatitis in mice

Treatment with the antileukemic agent asparaginase can induce acute pancreatitis, but the pathophysiology remains obscure. In the liver of mice, eukaryotic initiation factor 2 (eIF2) kinase general control nonderepressible 2 (GCN2) is essential for mitigating metabolic stress caused by asparaginase. We determined the consequences of asparaginase treatment on the pancreata of wild-type (WT, GCN2-intact) and GCN2-deleted (ΔGcn2) mice. Mean pancreas weights in ΔGcn2 mice treated with asparaginase for 8 days were increased (P < 0.05) above all other groups. Histological examination revealed acinar cell swelling and altered staining of zymogen granules in ΔGcn2, but not WT, mice. Oil Red O staining and measurement of pancreas triglycerides excluded lipid accumulation as a contributor to acini appearance. Instead, transmission electron microscopy revealed dilatation of the endoplasmic reticulum (ER) and accumulation of autophagic vacuoles in the pancreas of ΔGcn2 mice treated with asparaginase. Consistent with the idea that loss of GCN2 in a pancreas exposed to asparaginase induced ER stress, phosphorylation of protein kinase R-like ER kinase (PERK) and its substrate eIF2 was increased in the pancreas of asparaginase-treated ΔGcn2 mice. In addition, mRNA expression of PERK target genes, activating transcription factors 4, 3, and 6 (Atf4, Atf3, and Atf6), fibroblast growth factor 21 (Fgf21), heat shock 70-kDa protein 5 (Hspa5), and spliced Xbp1 (sXbp1), as well as pancreas mass, was elevated in the pancreas of asparaginase-treated ΔGcn2 mice. Furthermore, genetic markers of oxidative stress [sirtuin (Sirt1)], inflammation [tumor necrosis factor-α (Tnfα)], and pancreatic injury [pancreatitis-associated protein (Pap)] were elevated in asparaginase-treated ΔGcn2, but not WT, mice. These data indicate that loss of GCN2 predisposes the exocrine pancreas to a maladaptive ER stress response and autophagy during asparaginase treatment and represent a genetic basis for development of asparaginase-associated pancreatitis.

L-asparaginase-induced pancreatic injury is associated with an imbalance in plasma amino acid levels

BACKGROUND

The use of L-asparaginase (ASNase) to modify amino acid metabolism is one of the most effective chemotherapeutic means of inducing remission in acute lymphoblastic leukemia (ALL). However, severe pancreatitis sometimes occurs in patients receiving ASNase, because of an unknown mechanism.

OBJECTIVE

The purpose of the present study was to evaluate the relationship between ASNase-induced pancreatic injury and plasma amino acid levels in patients undergoing ASNase therapy.

METHODS

A total of 29 children aged 1-13.25 years (median age 4 years; male : female ratio 19 : 10) with ALL, who received induction therapy according to the Tokyo Children's Cancer Study Group L04-16 protocol, were studied. Levels of plasma amino acids and serum rapid turnover proteins (RTPs), pancreatic enzymes, and pancreatic protease inhibitors were measured before and 1, 2, 3, 4, 5, and 7 weeks after the first administration of ASNase.

RESULTS

Plasma asparagine levels were significantly lower after the first injection of ASNase (p < 0.01) and had almost recovered 2 weeks after the last ASNase injection. At 4 weeks after the first ASNase injection, serum aspartic acid, trypsin, and pancreatic secretory trypsin inhibitor (PSTI) levels remained significantly higher than those before the first ASNase injection (p < 0.01), and serum levels of prealbumin and transferrin remained significantly lower than those before the first ASNase injection (p < 0.01). Plasma amino acid and serum RTP levels gradually normalized after the last ASNase injection.

CONCLUSIONS

Levels of serum trypsin and PSTI were elevated during the 2 weeks after administration of ASNase, which suggested the presence of subclinical pancreatitis. This period is similar to the time period in the present study when the levels of plasma amino acids changed, thus suggesting that ASNase-induced pancreatic injury could be caused by the imbalance of plasma amino acid levels.