HDAC5 is required for maintenance of pericentric heterochromatin, and controls cell-cycle progression and survival of human cancer cells

Abstract

Histone deacetylases (HDACs) form a family of enzymes, which have fundamental roles in the epigenetic regulation of gene expression and contribute to the growth, differentiation, and apoptosis of cancer cells. In this study, we further investigated the biological function of HDAC5 in cancer cells. We found HDAC5 is associated with actively replicating pericentric heterochromatin during late S phase. We demonstrated that specific depletion of HDAC5 by RNA interference resulted in profound changes in the heterochromatin structure and slowed down ongoing replication forks. This defect in heterochromatin maintenance and assembly are sensed by DNA damage checkpoint pathways, which triggered cancer cells to autophagy and apoptosis, and arrested their growth both in vitro and in vivo. Finally, we also demonstrated that HDAC5 depletion led to enhanced sensitivity of DNA to DNAdamaging agents, suggesting that heterochromatin de-condensation induced by histone HDAC5 silencing may enhance the efficacy of cytotoxic agents that act by targeting DNA in vitro. Together, these results highlighted for the first time an unrecognized link between HDAC5 and the maintenance/assembly of heterochromatin structure, and demonstrated that its specific inhibition might contribute to increase the efficacy of DNA alteration-based cancer therapies in clinic.

Myoferlin plays a key role in VEGFA secretion and impacts tumor‐associated angiogenesis in human pancreas cancer

“…18 Myoferlin siRNA sequences are the same as above. ONTARGETplus nontargeting pool (Thermo Fisher-Dharmacon, Whaltham, MA) was used as irrelevant siRNA control.…”

Metabolic inhibitors accentuate the anti-tumoral effect of HDAC5 inhibition

“…Autophagy induction upon HDAC5 depletion/inhibition was attributed to induction of ROS, as it was prevented by ROS scavenger N-acetyl-L-cysteine (NAC) (Figures 2i and j). With published electron microscopy analysis showing presence of mitochondria engulfed in autophagosomes, 9 we hypothesized that ROS-producing mitochondria were selectively degraded by a specific autophagic process called mitophagy. 16 Parkin, p62 and LC3 proteins in the mitochondria-enriched fraction were more abundant in HDAC5-depleted cells (Figure 2k), suggesting a higher mitophagy flux in these cells.…”

“…Interestingly, iron dysregulation modulated the accumulation of ROS and cell death upon LMK235 (Figures 3f − h) or SAHA treatment (Supplementary Figures S4B − D). Finally, since we previuously reported that HDAC5 depletion potentiates the effect of chemotherapeutic agents such as cisplatin 9 and there are indications in the literature that iron can influence cisplatin toxicity, 17,18 we examined the role of iron in cisplatin-induced cell death upon HDAC5 depletion. Apoptosis of HDAC5-depleted cells co-treated with cisplatin was blocked after addition of NAC, suggesting that cisplatin-induced apoptosis upon HDAC5 depletion is associated with oxidative stress (Figure 3i).…”

“…Western blots were performed as described in Peixoto et al 9 All western blots are representative of at least three independent experiments.…”

“…We and others have investigated the function of Class IIa HDAC5 in cancer cells and found that its specific depletion by RNAi induced the growth arrest of cancer cells in vitro and decreased tumour growth in vivo. [9][10][11][12][13] Besides investigations on the specific role of individual HDAC members in cancer biology, a deeper understanding of the molecular mechanisms underlying specific HDAC functions would be helpful for identifying biological processes that will help to set the future direction of new combinatory strategies with HDAC inhibitor. Here, we wished to gain a better insight into the molecular mechanisms underlying the specific inhibition of HDAC5 in cancer cells.…”