Fig. 1From: Untargeted LC–MS/MS analysis reveals metabolomics feature of osteosarcoma stem cell response to methotrexateSpherical colonies (sarcospheres) generated from single-cell suspensions of OS cells cultured in serum-free medium supplemented with growth factors in non-adherent conditions. OS cells gradually aggregated and formed tumor spheres (Original magnification: 200 ×)Back to article page