Biomodulatory therapy induces durable remissions in multi-system Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is rare hematological neoplasia originating from the aberrant proliferation of CD207-positive dendritic cells. Refractory multi-system LCH is difficult to treat necessitating the continuous development of different salvage therapies. At our medical center, eleven patients (age 11 months to 77 years) with multi-system LCH were treated on a compassionate use basis with metronomic biomodulation therapy (MBT) involving the daily oral application of low-dose trofosfamide, etoricoxib, pioglitazone and low-dose dexamethasone. Overall, four patients including two heavily pretreated pediatric patients achieved ongoing complete remission. Moreover, partial disease remission was observed in three patients, and four patients attained stable disease. MBT demonstrated high activity against multi-system LCH even in patients, refractory to multiple systemic chemotherapies. Further confirmation of efficacy should be systematically evaluated in prospective trials.

Case Report: Characterizing the Role of the STXBP2-R190C Monoallelic Mutation Found in a Patient With Hemophagocytic Syndrome and Langerhans Cell Histiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory disorder. HLH can be considered as a threshold disease depending on the trigger and the residual NK-cell cytotoxicity. In this study, we analyzed the molecular and functional impact of a novel monoallelic mutation found in a patient with two episodes of HLH. A 9-month-old child was diagnosed at 2 months of age with cutaneous Langerhans cell histiocytosis (LCH). After successful treatment, the patient developed an HLH episode. At 16 month of age, the patient went through an HSCT losing the engraftment 5 months later concomitant with an HLH relapse. The genetic study revealed a monoallelic mutation in the STXBP2 gene (.pArg190Cys). We transfected COS7 cells to analyze the STXBP2-R190C expression and to test the interaction with STX11. We used the RBL-2H3 cell line expressing STXBP2-WT-EGFP or R190C-EGFP for degranulation assays. Mutation STXBP2-R190C did not affect protein expression or interaction with syntaxin-11. However, we have demonstrated that STXBP2-R190C mutation diminishes degranulation in the RBL-2H3 cell line compared with the RBL-2H3 cell line transfected with STXBP2-WT or nontransfected. These results suggest that STXBP2-R190C mutation acts as a modifier of the degranulation process producing a decrease in degranulation. Therefore, under homeostatic conditions, the presence of one copy of STXBP2-R190 could generate sufficient degranulation capacity. However, it is likely that early in life when adaptive immune system functions are not sufficiently developed, an infection may not be resolved with this genetic background, leading to a hyperinflammation syndrome and eventually develop HLH. This analysis highlights the need for functional testing of new mutations to validate their role in genetic susceptibility and to establish the best possible treatment for these patients.