Study identifies potential target for treating childhood blood cancer

Their findings in zebrafish and JMML patients suggest that treatment using anti-inflammatories could be a possible new approach to combating the disease.

JMML is a highly aggressive blood cancer with poor outcomes for patients. Children with a relatively common developmental syndrome called Noonan Syndrome (NS) have a high risk of developing a condition similar to JMML, called myeloproliferative neoplasm, which can then progress to JMML. The most frequent genetic cause of JMML and NS is a mutation in the PTPN11 gene, which encodes the protein-tyrosine phosphatase SHP2.

"Hematopoietic stem and progenitor cells are considered to be the cells of origin for JMML," says first author Maja Solman, Postdoctoral Fellow at the Hubrecht Institute, Utrecht, Netherlands. "Currently, hematopoietic stem cell transplantation is the only treatment for the disease, but it has a relapse rate of 50%. With such limited treatment options for JMML, we wanted to gain a better understanding of how the disease develops to identify other possible ways of targeting it."

To do this, Solman and the team used a novel zebrafish model with a mutation in SHP2 -- equivalent to the most common mutation in NS patients which can cause JMML. They used a technique called single-cell transcriptomics to examine the level of gene expression in the animals' hematopoietic stem and progenitor cells. The analysis showed an increase in the number of monocyte and macrophage progenitor cells in the fish embryos, and that these cells expressed genes associated with the immune response.

The team next compared these results with their analysis of hematopoietic stem and progenitor cells, which contained SHP2 mutations, from the bone marrow of JMML patients. They found a similar pattern of proinflammatory gene expression in these cells as the one they identified in the zebrafish.

Finally, they treated the zebrafish embryos with an anti-inflammatory drug called dexamethasone. They found that the drug helped rescue JMML-like blood defects in the fish, suggesting that anti-inflammatories could one day be an important treatment strategy for JMML.

"Our work reveals striking similarities in the proinflammatory response of human and zebrafish cells containing SHP2 mutations, and shows that inhibiting this response can improve JMML-like symptoms in a zebrafish model," concludes senior author Jeroen den Hertog, Group Leader and Managing Director at the Hubrecht Institute, and Professor of Molecular Developmental Zoology at Leiden University, Netherlands. "Together, these findings lay the groundwork for future studies to verify the effectiveness of anti-inflammatories as a potential new treatment approach for JMML patients."