Glioblastoma Multiforme (GBM) is a lethal primary brain tumor with poor survival lifespan and dismal outcome. Surgical resection of GBM is greatly limited due to the biological significance of brain, giving rise to tumor relapse in GBM patients. Transactive response DNA binding protein-43 (TDP-43) is a DNA/RNA-binding protein known for causing neurodegenerative diseases through post-translational modification; but little is known about its involvement in cancer development. In this study, we found that nutrient deprivation in GBM cell lines elevated TDP-43 expression by a mechanism of evasion from ubiquitin-dependent proteolytic pathway, and subsequently activated the autophagy process. Exogenous overexpression of TDP-43 consistently activated autophagy and suppressed stress-induced apoptosis. The inhibition of autophagy in TDP-43-overexpressing cells effectively increased the apoptotic population under nutrition shortage. Furthermore, we demonstrated that HDAC6 was involved in the activation of autophagy in TDP-43-overexpressing GBM cell lines. The treatment with SAHA, a universal HDAC inhibitor, significantly reduced TDP-43-mediated anti-apoptotic effect. Additionally, the results of immunohistochemistry showed that TDP-43 and HDAC6 collaborated in GBM-tumor lesions and negatively correlated with the relapse-free survival of GBM patients. Taken together, our results suggest that the TDP-43-HDAC6 signaling axis functions as a stress responsive pathway in GBM tumorigenesis and combats nutrient deprivation stress via activating autophagy, while inhibition of HDAC6 overpowers the pathway and provides a novel therapeutic strategy against GBM.
Keywords: HDAC6; TDP-43; autophagy; glioblastoma; nutrient deprivation.