Expression of CDK9 in osteosarcoma cell lines and osteosarcoma patient fresh tissues. (A) Expression levels of CDK9 in osteosarcoma cell lines (U2OS, U2OSR2, KHOS, KHOSR2, MG63, Saos-2, 143B and MNNG/HOS) were stronger than the expression of CDK9 in the normal osteoblast cell line (HOB-c) measured by Western blotting. (B) Densitometry quantification of the Western blots of CDK9 from Fig. 4A, presented as relative to tubulin expression. The data represent the mean ± SE of the experiment carried out in triplicate. (C) CDK9 expression in eight human osteosarcoma fresh tissues measured by Western blotting. (D) Densitometry quantification of the Western blots of CDK9 from Fig. 4C, presented as relative to tubulin expression. The data represent the mean ± SE of the experiment carried out in triplicate. (E) Confirmation of CDK9 expression in osteosarcoma cell lines by immunofluorescence with antibodies to CDK9 (green) and Actin (red). Green fluorescence of CDK9 protein was mainly localized in the nucleus of osteosarcoma cells (Scale bar, 50 μm).