Targeting of histone deacetylase 10 causes neuroblastoma cell death via lysosomal dysfunctions and ROS release

Pan-HDAC (histone deacetylase) inhibitors are known to induce cell death in tumor cells and are currently being evaluated in clinical trials. However, due to their unselective nature, these compounds exhibit dose limiting side effects restricting their full anti-cancer potential. Therefore, characterization of the molecular function of single HDAC isozymes is of major importance. Here, we show that only those HDAC inhibitors covering class IIb HDAC10 in their inhibitory profile induced accumulation of lysosomes in several neuroblastoma cell lines associated with p53-independent cell death. Enforced expression of HDAC10 enhanced tumor cell survival and reduced endogenous as well as induced lysosome formation, whereas a catalytically inactive HDAC10 did not. Co-immunoprecipitation studies revealed the binding of the lysosomal chaperone HSC70 to HDAC10. RNAi-mediated knockdown of HSC70 or HDAC10 expression induced the accumulation of dysfunctional lysosomes in BE(2)-C neuroblastoma cells. Consequently, autophagic flux was disturbed and resulted in an accumulation of autophagosomes upon targeting of HDAC10. Additionally, the accumulation of dysfunctional lysosomes was accompanied by ROS release, leading to programmed cell death. Simultaneous inhibition of apoptosis and necroptosis with zVAD-fmk and necrostatin efficiently rescued cell death mediated by HDAC10 knockdown.

These results demonstrate for the first time that class IIb family member HDAC10 is involved in the regulation of lysosomal functions, such as chaperone-mediated autophagy in neuroblastoma cells. Selective targeting of this HDAC family member induces an alternative lysosomal-mediated tumor cell death pathway and may thus be a novel strategy for neuroblastoma therapy.