Bone Abstracts

Tumor development occurs often by over-activation of members of the RAS-oncogene family (small GTPases (sGTPs)). By blocking the mevalonate pathway, aminobisphosphonates (BPs), and statines prevent activation of GTPs by inhibiting their post-translational prenylation. As we have shown, this induces apoptosis in U2OS osteosarcoma cells by re-activation of FAS expression via epigenetic DNA demethylation (1).

The histone demethylase JHDM1D exerts a tumor-suppressive function by down-regulating angiogenesis (2). Furthermore, weak JHDM1D expression correlates with Rho-GTPase dependent increased cell motility and invasiveness of MDA-MB-231 and MCF-7 breast cancer cells (3)

Bone metastatic human PC-3 prostate and MDA-MB-231 breast cancer and U2OS and MG63 osteosarcoma cells were treated up to 72 h with increasing concentrations of ibandronate (Ibn) or with the statin simvastatin (Sim). JHDM1D expression was suppressed by siRNA techniques, cDNA over-expressing cell lines where created. Gene expression was analyzed by Affymetrix gene array, RT-qPCR, and immunoblotting. Caspases activities and cell proliferation were measured.

While Sim strongly repressed proliferation in all cell-lines tested, Ibn showed a similar effect only in osteosarcoma cells having a considerable effect on PC-3 and MDA-MB-231 cells.

For all cell lines, both compounds increased significantly the expression of JHDM1D. Knock down of JHDM1D largely abrogated Simv or Ibn dependent inhibition of cell proliferation in PC3 and MDA-MB-231 cells or in osteosarcoma cells respectively.

Tumor related genes like FAS, CEACAM1, DRAM1, ESM1, or PTX3 where strongly up-regulated by both drugs in the cell-lines tested. Re-expression of all these genes by Sim or Ibn was JHDM1D dependent. Cell proliferation rates where halved in Esm1 or PTX3 over-expressing osteosarcoma cells. For PTX3 this may be due to increased FAS expression.

Our data demonstrate a central role for JHDM1D in suppression of RAS-oncogene family mediated bone tumor development.