Fig. 1
GDF15 promotes PCa bone metastasis. a Expression of GDF15 protein in human PCa cell lines as indicated by Western blot analysis. b The expression of GDF15 at the transcriptional level was analyzed by RT–qPCR analysis in human PCa cell lines. c Western blot analyses to determine GDF15 expression in the lysates of PC3-Luc(i) and PC3-GDF15(i) cells after 48 h of doxycycline (Dox) induction. d Representative photographs of mice injected with PC3-Luc(i) and PC3-GDF15(i) cells to detect bone metastasis after Dox treatment at the indicated time points using IVIS imaging. e Representative ex vivo images of excised tissues from different skeletal sites after final in vivo imaging within 10 min of luciferin injection (bioluminescent images of the ribs and sternum, spine, forelimbs, and hind limbs) (left panel) and quantification of the number of skeletal sites with metastasis in mice injected with PC3-Luc(i) and PC3-GDF15(i) (right panel). f Histopathological staining of excised bone sections of PC3-Luc(i)- and PC3-GDF15(i)-injected mice. (Upper panel) Representative H&E staining and TRAP (osteoclast marker) staining of bone. Bone sections were immunostained for cathepsin K (a functional marker for bone resorption) and Ki67 and subjected to corresponding IgG staining. (Lower panel) Quantification of TRAP, cathepsin K and Ki67 staining. Bone marker analysis in serum obtained from PC3-Luc(i)- and PC3-GDF15-injected mice. Scale bar = 400 µm. g Serum CTX and P1NP were measured to assess bone turnover (n = 6 mice/group). The data are given as the mean ± SEM, and P ≤ 0.05 was considered to indicate statistical significance. *P < 0.05, **P < 0.01, ***P < 0.001 compared to the PC3-Luc(i)-injected group
