FBW7 suppression leads to SOX9 stabilization and increased malignancy in medulloblastoma (2016)
Figure 4

Figure 4. FBW7α circumvented SOX9-induced cell migration and metastasis in medulloblastoma.

(A) Overall survival analysis of mice bearing Daoy cell line expressing SOX9 with doxycycline (dox) -inducible FBW7α (Daoy-SOX9/T–FBW7α). The dox-preconditioned or the control cells (105 cells) were orthotopically xenografted to the cerebellum of 6-weeks old Athymic Nude-Foxn1nu mice, which were continuously fed with either the dox-containing chow (red line) or the regular chow food (green line), respectively. Mice xenografted with dox-preconditioned Daoy-SOX9/T-FBW7α and fed continuously with dox-containing chow (red line) survived longer (p= 0.0285) than the control group (green line)

(B) Representative of Haemotoxylin & Eosin (H&E) staining of medulloblastoma tumors arising from the orthotopic xenograft experiment described in (A). Both the control (no dox-treated) and the dox-treated mice developed primary intracerebellar tumors (green and red arrows, respectively). SOX9-expressing Daoy tumors disseminated to the spinal cord (3/4; green asterisks), while the group continuously receiving dox-containing chow showed no metastatic spread (0/4).

(C) Representative bright field images of migrating Daoy-SOX9/T-FBW7α in the absence or presence of Dox. Daoy-SOX9/T-FBW7α cells were either maintain in regular culture or pre-conditioned with dox prior to experiments. The cells (2 x 105 cells / insert) were seeded and let to migrate across 5 μm filter pore toward the laminin-coated trans-well for 4 hours prior to fixation and staining with crystal violet. Histogram quantification of cell migration were performed by measuring the crystal violet absorbance of the stained-migrating cells and presented as mean + standard deviation from 2 independent experiments each containing 2 technical replicates.

(D) Representative H&E staining of primary (arrow) and disseminated tumors (asterisk) arising from orthotopic xenograft of parental and SOX9-expressing medulloblastoma initiating cells (MIC and MIC-Sox9, respectively). Quantification of primary and metastatic tumors arising from both of MIC (n=16) and MIC-SOX9 (n=8) is shown in the histogram (p=0.0000136).

(E) Quantitative comparison of MIC and MIC-SOX9 cells to migrate across 5 μm filter pore toward the laminin-coated trans-well for 4 hours. Quantification of cell migration were performed as described in (C) and presented as mean + standard error mean from 6 replicates.

(F) Transwell migration of SOX9-expressing MIC with dox-inducible FBW7α or dominant negative ∆F FBW7α. The cells were either maintain in regular culture or pre-conditioned with dox prior to assessment of in vitro transwell migration as described in (C). Data are mean + standard deviation from 2 independent experiments each containing 2 technical replicates.

(G) Representative bright field images of (F)

(H) Correlation between clinical metastatic staging and SOX9 protein across the TMA of 142 cases of human medulloblastoma. The SOX9 protein levels were determined by IHC in Figure 3F. Tumors with SOX9 protein level frequently presented (p=0.038, Fisher’s exact test,) with the M3 metastatic staging, spread to the spinal cord (red bars). Analysis was carried out by comparing patients with high SOX9 protein rank (Rank 5-7) versus patients with low SOX9 protein rank (Rank 1-3).