Genetic basis for iMCD-TAFRO.

Area of Science:

• Hematology
• Oncology
• Molecular Biology

Background:

• Idiopathic multicentric Castleman disease (iMCD) is a rare lymphoproliferative disorder.
• TAFRO syndrome is a clinical subtype of iMCD characterized by specific symptoms: thrombocytopenia, anasarca, fever, reticulin fibrosis/renal dysfunction, and organomegaly.
• The underlying causes of iMCD-TAFRO and its associated cytokine hypersecretion remain largely unknown.

Observation:

• Two iMCD-TAFRO patients were analyzed for genetic mutations.
• One patient presented with a somatic MEK2^P128L mutation.
• The other patient exhibited a germline RUNX1^G60C mutation.

Findings:

• The MEK2^P128L mutation leads to hyperactivated MAP kinase signaling, IL-3 hypersensitivity, and sensitivity to MEK inhibitors.
• The RUNX1^G60C mutation acts as a dominant-negative form, impairing RUNX1 transcriptional activity and enhancing hematopoietic stem/progenitor cell self-renewal.
• Both mutations resulted in significant ERK activation, suggesting a role for MAPK signaling in iMCD-TAFRO pathogenesis.

Implications:

• MAPK pathway activation is implicated in iMCD-TAFRO.
• Inhibiting the MAPK pathway presents a potential therapeutic strategy for iMCD-TAFRO.
• iMCD-TAFRO may share common pathogenetic mechanisms with clonal inflammatory disorders, including histiocytoses and myeloid neoplasms, that harbor MEK and RUNX1 mutations.