Nano hydroxyapatite induces glioma cell apoptosis by suppressing NF-B signaling pathway

Nano-sized hydroxyapatite (nHA) particles have been demonstrated to exert anti-cancer effects on multiple cancer cell lines and animal models of cancer biology. However, the molecular mechanism underlying the effects of nHA particles on glioma cells remains unclear. The present study aimed to examine the effects of nHA on the behavior of glioma cells and investigate its underlying molecular mechanism. Rat glioma C6 cells and human glioma U87MG ATCC cells were exposed to nHA (20-100 mu g/ml), and its effects on cell morphology, viability, apoptosis, cell cycle, invasion and nuclear factor (NF)-B signaling were analyzed. Exposure of C6 and U87MG ATCC cells to 20 mu g/ml nHA for 24 h caused cell detachment. Viability of C6 and U87MG ATCC cells were significantly reduced by nHA in a dose-dependent manner (P<0.05). Nuclear staining with Hoechst 33258 exhibited clear chromatin condensation in C6 cells following 24 h exposure to 25 mu g/ml nHA. Flow cytometry revealed that nHA (20-100 mu g/ml) significantly induced apoptosis and cell cycle G2/M arrest in C6 and U87MG ATCC cells (P<0.05). Transwell invasion assay demonstrated that nHA (20-60 mu g/ml) significantly inhibited invasion of U87MG ATCC cells (P<0.05). Furthermore, western blotting and confocal immunofluorescence microscopy revealed that nHA (20-100 mu g/ml) decreased NF-B p65 protein expression and blocked NF-B p65 nuclear translocation in C6 cells. The protein expression of NF-B target molecules, such as B cell lymphoma 2, cyclooxygenase-2 and survivin, were also significantly reduced by nHA in a dose-dependent manner in both C6 and U87MG ATCC cells (P<0.05). In conclusion, it was demonstrated that the inhibitory effect of nHA on glioma cells is likely associated with the downregulation of NF-B signaling.