Disease overview: Hairy cell leukemia (HCL) and HCL‐like disorders, including HCL variant (HCL‐V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B‐cell disorders. They are characterized by the identification of hairy cells, a specific genetic profile, a different clinical course and the need for appropriate treatment.Diagnosis: Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of three or four based on the CD11C, CD103, CD123, and CD25 expression. Also, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAF V600E somatic mutation.Risk stratification: Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood and the immunoglobulin heavy chain variable region gene mutational status. The VH4‐34 positive HCL cases are associated with poor prognosis.Treatment: Risk adapted therapy with purine nucleoside analogs (PNA) are indicated in symptomatic first line HCL patients. The use of PNA followed by rituximab represents an alternative option. Management of progressive or refractory disease is based on the use of BRAF inhibitors associated or not with MEK inhibitors, recombinant immunoconjugates targeting CD22 or BCR inhibitors.

New generation sequencing of targeted genes in the classical and the variant form of hairy cell leukemia highlights mutations in epigenetic regulation genes New generation sequencing of targeted genes in the classical and the variant form of hairy cell leukemia highlights mutations in epigenetic regulation genes

Hairy cell leukemia (HCL) is characterized by abnormal villous lymphoid cells that express CD103, CD123, CD25 and CD11c. HCL-like disorders, including hairy cell leukemia variant (vHCL) and splenic diffuse red pulp lymphoma (SDRPL), have similar morphologic criteria and a distinct phenotypic and genetic profile. We investigated the immunophenotypic features of a large cohort of 82 patients: 68 classical HCL, 5 vHCL/SDRPL and 9 HCL-like NOS. The HCL immunophenotype was heterogeneous: positive CD5 expression in 7/68 (10%), CD10 in 12/68 (18%), CD38 in 24/67 (36%), CD23 in 22/68 (32%) and CD43 in 19/65 (31%) patients. CD26 was expressed in 35/36 (97%) of HCL patients, none of vHCL/SDRPL and one of seven HCL-like NOS (14%). When adding CD26 to the immunologic HCL scoring system (one point for CD103, CD123, CD25, CD11c and CD26), the specificity was improved, increasing from 78.6% to 100%. We used unsupervised analysis of flow cytometry raw data (median fluorescence, percentage of expression) and the mutational profile of BRAF, MAP2K1 and KLF2. The analysis showed good separation between HCL and vHCL/SDRPL. The HCL score is not sufficient, and the use of unsupervised analysis could be promising to achieve a distinction between HCL and HCL-like disorders. However, these preliminary results have to be confirmed in a further study with a higher number of patients.

Multiple myeloma (MM) is a plasma cell neoplasm that remains incurable due to innate or acquired resistance. Although MM cells produce high intracellular levels of reactive oxygen species (ROS), we hypothesised that they could remain sensitive to ROS unbalance. We tested if the inhibition of ROS, on one hand, or the overproduction of ROS, on the other, could (re)sensitise cells to bortezomib (BTZ). Two drugs were used in a panel of MM cell lines with various responses to BTZ: VAS3947 (VAS), an inhibitor of NADPH oxidase and auranofin (AUR), an inhibitor of thioredoxin reductase (TXNRD1), an antioxidant enzyme overexpressed in MM cells. We used several culture models: in suspension, on a fibronectin layer, in coculture with HS-5 mesenchymal cells, and/or in 3-D culture (or spheroids) to study the response of MM primary cells and cell lines. Several MM cell lines were sensitive to VAS but the combination with BTZ showed antagonistic or additive effects at best. By contrast, in all culture systems studied, the combined AUR/BTZ treatment showed synergistic effects on cell lines, including those less sensitive to BTZ and primary cells. MM cell death is due to the activation of apoptosis and autophagy. Modulating the redox balance of MM cells could be an effective therapy for refractory or relapse post-BTZ patients.