Fig. 5: BRAF^V600E-mediated oncogene-induced senescence in histiocytic lesions and in human grafts.

a Immunohistochemical analysis of serial sections of lungs lesions from a representative mouse transplanted with BRAF^V600E-expressing HSPCs at the time of sacrifice. Markers for immunohistochemistry include: GFP for vector marking, p16 for senescence/cell cycle arrest, S100, CD207, and PGM1 for dendritic cells and macrophages. Tissue morphology analyzed by hematoxylin and eosin (H&E). Yellow boxes indicate zoom-in areas. Scale bars: 300 or 50 µm. n = 1 representative mouse. b Representative immunohistochemical analysis for p16 expression in lung sections from mice transplanted with wtBRAF or BRAF^V600E-expressing HSPCs harvested at 9 and 24 days after transplantation. Immunofluorescence analysis for p16 (red) and the proliferation marker Ki67 (green) in lung lesions from a mouse of the BRAF^V600E group at 24 days post-transplantation. (n = 3 for each time point). Nuclei stained by DAPI (blu). Scale bar: 50 µm. c, d Frequency (in percentage) of GFP⁺ or GFP⁻ human myeloid cells (CD33⁺) which express the senescence markers p16 (c) or SA-β-gal (d). FACS analysis was performed on BM cells obtained at euthanasia from mice transplanted with wtBRAF (blue) or BRAF^V600E (red) HSPCs (n = 17 each group). Data are presented as mean values +/− SEM. Statistical test: two-tailed Mann−Whitney ****p < 0.0001, *p < 0.05. e Representative images of a skin lesion from a patient with histiocytosis stained for p16 (positive ∼85%), BRAF^V600E (VE1) (positive ∼25%), Ki67 (positive <1%), and SA-β-Gal (positive ∼48%). Tissue morphology was analyzed by hematoxylin and eosin. Scale bars: 100 or 200 µm.