Philip A. Roehrs

The genomic landscape of juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm (MPN) of childhood with a poor prognosis. Mutations in NF1, NRAS, KRAS, PTPN11 or CBL occur in 85% of patients, yet there are currently no risk stratification algorithms capable of predicting which patients will be refractory to conventional treatment and could therefore be candidates for experimental therapies. In addition, few molecular pathways aside from the RAS-MAPK pathway have been identified that could serve as the basis for such novel therapeutic strategies. We therefore sought to genomically characterize serial samples from patients at diagnosis through relapse and transformation to acute myeloid leukemia to expand knowledge of the mutational spectrum in JMML. We identified recurrent mutations in genes involved in signal transduction, splicing, Polycomb repressive complex 2 (PRC2) and transcription. Notably, the number of somatic alterations present at diagnosis appears to be the major determinant of outcome.

Increased BCR responsiveness in B cells from patients with chronic GVHD.

Although B cells have emerged as important contributors to chronic graft-versus-host-disease (cGVHD) pathogenesis, the mechanisms responsible for their sustained activation remain unknown. We previously showed that patients with cGVHD have significantly increased B cell-activating factor (BAFF) levels and that their B cells are activated and resistant to apoptosis. Exogenous BAFF confers a state of immediate responsiveness to antigen stimulation in normal murine B cells. To address this in cGVHD, we studied B-cell receptor (BCR) responsiveness in 48 patients who were >1 year out from allogeneic hematopoietic stem cell transplantation (HSCT). We found that B cells from cGVHD patients had significantly increased proliferative responses to BCR stimulation along with elevated basal levels of the proximal BCR signaling components B cell linker protein (BLNK) and Syk. After initiation of BCR signaling, cGVHD B cells exhibited increased BLNK and Syk phosphorylation compared with B cells from patients without cGVHD. Blocking Syk kinase activity prevented relative post-HSCT BCR hyper-responsiveness of cGVHD B cells. These data suggest that a lowered BCR signaling threshold in cGVHD associates with increased B-cell proliferation and activation in response to antigen. We reveal a mechanism underpinning aberrant B-cell activation in cGVHD and suggest that therapeutic inhibition of the involved kinases may benefit these patients.

Corrigendum: The genomic landscape of juvenile myelomonocytic leukemia.

Nat. Genet. 47, 1326–1333 (2015); published online 12 October 2015; corrected after print 7 December 2015 In the version of this article initially published, two patients were stated on page 5 to have been excluded owing to insufficient follow-up data. These patients were included in the final analysis, but two additional patients were excluded owing to the presence of Noonan syndrome.

Erratum: Corrigendum: The genomic landscape of juvenile myelomonocytic leukemia

Nat. Genet. 47, 1326–1333 (2015); published online 12 October 2015; corrected after print 7 December 2015 In the version of this article initially published, two patients were stated on page 5 to have been excluded owing to insufficient follow-up data. These patients were included in the final analysis, but two additional patients were excluded owing to the presence of Noonan syndrome.

Successful use of palifermin following severe anaphylaxis to pegaspargase in a pediatric patient with acute lymphoblastic leukemia

Palifermin and pegaspargase are Escherichia coli-derived drug products. Hypersensitivity reactions, including anaphylaxis, are frequently reported with pegaspargase. In high-risk acute lymphoblasic leukemia (ALL), patients undergoing allogeneic hematopoietic stem cell transplant may be treated with palifermin as a supportive care measure for mucositis prophylaxis. However, no literature exists documenting the cross-reactivity between palifermin and pegaspargase. We report a case in which a child with very high-risk ALL having experienced severe anaphylaxis with pegaspargase was later successfully treated with palifermin during stem cell transplant conditioning.

Erratum: The genomic landscape of juvenile myelomonocytic leukemia (Nature Genetics (2015) 47 (1326-1333))

Nat. Genet. 47, 1326–1333 (2015); published online 12 October 2015; corrected after print 7 December 2015 In the version of this article initially published, two patients were stated on page 5 to have been excluded owing to insufficient follow-up data. These patients were included in the final analysis, but two additional patients were excluded owing to the presence of Noonan syndrome.