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Vemurafenib acts as molecular switch in Langerhans Cell Histiocytosis

ABSTRACT: Langerhans cell histiocytosis (LCH) is a neoplasm marked by the accumulation of CD1a+CD207+ cells. It is most commonly driven by a somatic activating mutation in the BRAF kinase (BRAFV600E). Multisystem disease with risk-organ involvement requires intensive chemotherapy, making BRAF-inhibitors an attractive option. Here, we present a comprehensive analysis of the course of an LCH patient treated with the combination of vemurafenib with salvage chemotherapy who achieved complete clinical and molecular remission. We conclusively show that there is no relationship between blood-BRAF levels and clinical presentation during treatment with vemurafenib, but that vemurafenib leads to a fast, efficient, but reversible inhibition of clinical manifestations of high-risk LCH such as cytopenia, fever, and hypoproteinemia. In line, serum levels of inflammatory cytokines exactly mirror vemurafenib administration. Genotyping for the BRAFV600E mutation shows its presence in multiple hematopoietic cell types, including NK cells and granulocytes. Single-cell transcriptome analysis of peripheral blood and bone marrow cells at time of diagnosis and during treatment indicate that RAF-inhibition abrogates the expression of inflammatory cytokines previously implicated in LCH. Together, our data suggest that while the CD1a+CD207+ histiocytes are the hallmark of LCH, other BRAF-mutated cells themselves contribute significantly to morbidity in patients with multisystem LCH.

ORGANISM(S): Homo sapiens

PROVIDER: GSE175480 | GEO | 2021/09/23

REPOSITORIES: GEO

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