Extended Data Figure 6. Histology of Braf(D631A)-driven lung adenocarcinoma and evaluation of Braf(D631A)-dependent activation of MAPK signalling in vitro.

a, Haematoxylin and eosin staining of paraffin-embedded lung sections from Ad-Cre-infected Braf ^+/LSLD631A mice killed at humane end point. Sections display moderately to poorly circumscribed tumours occupying nearly an entire lung lobe, with compressed adjacent lung parenchyma and peripherally infiltrated by mononuclear inflammatory cells, mainly macrophages. Tumour masses are composed by papillary outgrowths or less-differentiated areas with increased cellular pleomorphism. Images correspond to three independent mice. Scale bar, 100 μm. b, Schematic representation of BRAF mutations detected in human tumours with high (top) or low/absent (bottom) kinase activity when compared to the wild-type isoform (see also the accompanying manuscript by Yao et al.²⁴). c, Primary keratinocytes derived from Braf ^+/LSLD631A (B), Braf ^lox/LSLD631A (BL) and Braf ^+/LSLD631A; Craf ^lox/lox (BC) mice were infected with Ad-Cre (5 MOI) and treated with recombinant EGF (150 ng ml⁻¹ for 1 h) where indicated. The activation of MAPK signalling was assessed by western blot analysis of p-Erk1/2, demonstrating that the activation of MAPK signalling by Braf(D631A) in epithelial cells requires upstream RTK activation and is enhanced by elimination of the wild-type Braf allele. Efficient recombination of the Craf conditional alleles in Ad-Cre-infected BC cells is also shown, demonstrating that MAPK activation by Braf(D631A) is Craf-dependent. Expression levels of Erk1/2 and Gapdh are shown as loading controls. For gel source data, see Supplementary Fig. 1.