Live Cell Imaging Supports a Key Role for Histone Deacetylase as a Molecular Target during Glioblastoma Malignancy Downgrade through Tumor Competence Modulation

Figure 6

HDAC activity blockade in synergy with the developing embryo leads to tunneling tube formation in U87-MG cells. U87-MG oncospheres were generated in vitro, exposed to iHDACs (100 nM TSA) for 72 hours prior xenogaft and placed on the neuroepithelium wall (A) or inside the developing neural tube at the prosencephalic level (B). At E5 chick developmental stage (C), embryos were fixed and in situ hybridization was performed using Alu probe. In situ hybridization revealed that both control and iHDAC-treated U87-MG cells were integrated into the embryonic mesenchyme. iHDAC-treated cells spread for longer distances than control cells (D). The embryonic environment efficiently promoted cell proliferation in both control and iHDAC-treated cells (E and F, red asterisks), bypassing iHDAC inhibition of cell proliferation observed in vitro as more mitotic figures Alu⁺ were found in the iHDAC group (K). Tunneling tube formation was observed in vivo only in iHDAC-treated cells (G and I, asterisks). Tunneling tubes connected neighboring tumor cells (G and I, asterisks) as well as tumor cells and embryonic vessels (H, arrow head). More embryonic vessels were found close to Alu⁺ nuclei in iHDAC-treated cells than in control cells (J, L). NE = neuroepithelium; V = embryonic vessel.