Fig. 1: Rsk2 deficiency impairs OS expansion by limiting osteoblastogenesis at the tumor surface.

A Representative images of undecalcified spine sections from 16-week-old mice with the indicated genotypes after Kossa-staining. Tumors are marked with white arrows. B Quantification of the number (nb) of tumors in spine sections (lumbar vertebral bodies L1–L6) from mice with the indicated genotypes (nb of tumor/6 vertebrae bodies) and quantification of tumor size by measuring the ratio of the area of each tumor on vertebral body area (n = 7–8 mice per genotype). C Representative images of osteosarcomas on undecalcified spine sections from mice with the indicated genotypes after staining with toluidine blue. D Quantification of osteoblast number (N.Ob/B.Pm), osteoclast number per bone perimeter (N.Oc/B.Pm), osteocyte number per bone perimeter (N.Ot/B.Pm) and chondrocyte number per bone perimeter (N.Ch./B.Pm) inside the tumor areas (n = 4 mice per genotype). E Representative images of osteosarcoma surfaces from mice with the indicated genotypes after staining with toluidine blue and quantification of the osteoblasts present at the tumor surface (N.Ob. at the surface/Tumor Pm), here marked with red arrows (n = 7–10 mice per genotype). F X-ray images of 16-week-old mice with the indicated genotypes. White arrows indicate the presence of osteosarcomas in the legs. Cells were extracted from these tumors and seeded in a flask to create cell lines after 10 passages. Image provided by Servier Medical Art (https://smart.servier.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Data are expressed as mean ± SD and analyzed by unpaired two-tailed t test: *p < 0.05, **p < 0.01, ***p < 0.001.