Induction of synergistic non‑apoptotic cell death by simultaneously targeting proteasomes with bortezomib and histone deacetylase 6 with ricolinostat in head and neck tumor cells

Abstract

Following surgery and chemoradiation, ~50% of patients with locally advanced head and neck tumors experience relapse within the first two years, with a poor prognosis. Therefore, a novel therapeutic approach is required. The aim of the present study was to investigate the effect of combination treatment with the proteasome inhibitor bortezomib (BTZ), and ricolinostat (RCS), a specific inhibitor of histone deacetylase 6 (HDAC6), on CAL27 and Detroit562 head and neck cancer cells. BTZ and RCS exhibited cytotoxicity in a dose-and time-dependent manner. Simultaneous treatment with BTZ and RCS resulted in the synergistic enhancement of non-apoptotic cell death and autophagy. The receptor-interacting serine/threonine-protein kinase 1 (RIPK1) inhibitor, necrostatin, but not the autophagy inhibitor, 3-methyladenine, attenuated the cytotoxicity of combined BTZ and RCS treatment. Thus, necroptosis [type-III programmed cell death (PCD)], but not autophagic cell death (type-II PCD), appeared to contribute to the pronounced cytotoxicity. However, no phosphorylation of RIPK1 or mixed lineage kinase domain-like protein was detectable in response to BTZ or RCS. Furthermore, RCS induced α-tubulin acetylation and inhibited BTZ-induced aggresome formation along with endoplasmic reticulum stress loading. Combined treatment with BTZ and RCS enhanced the production of reactive oxygen species (ROS). The ROS scavenger, N-acetyl cysteine, abrogated the increase in cytotoxicity. These results suggest the potential therapeutic value of the dual targeting of the proteasome and HDCA6 for head and neck cancers through the induction of necroptosis-like cell death along with ROS generation.

The Tubulin Code and Tubulin-Modifying Enzymes in Autophagy and Cancer

“…Concerning tubulin PTMs, the direct effects of modulating tubulin PTMs on autophagy induction and cancer growth have not yet been identified. On the other hand, several papers on cancer therapeutics suggest that autophagy can act to promote cell death of tumor cells in response to exposure to HDAC6 inhibitors [ 130 , 135 , 153 , 154 ]. Moreover, the novel small molecule SIRT2-specific inhibitor NCO-90/141 has been reported to inhibit cell growth of leukemic cell lines by simultaneously causing apoptosis and autophagic cell death [ 140 ].…”

Role of Selective Histone Deacetylase 6 Inhibitor ACY-1215 in Cancer and Other Human Diseases

“…In cholangiocarcinoma, reduction of autophagy caused by ACY-1215 decreases proliferation and increases cilia expression ( Peixoto et al, 2020 ). In primary lymphoma, head and neck cancer and melanoma, ACY-1215 and bortezomib have also been demonstrated to have strong synergic effects by dual targeting protein degradation pathways ( Amengual et al, 2015 ; Peng et al, 2017 ; Hattori et al, 2021 ).…”

Advances in mechanistic study of control of oxidative stress injury through modulating HDAC6 activity

“…Treatment with Tubastatin A further increase the expression amount of Atg7 and Beclin-1, indicating the autophagy due to renal injury is increased by HDAC6 inhibition (Tang et al, 2018). In CAL27 cells, a HDAC6 inhibitor Ricolinostat treatment for 24 h, cytoplasmic autophagosome and lysosomes increase signi cantly in amount, suggesting that Ricolinostat induces autophagy in CAL27 cells (Hattori, 2021)]. Other study reveals that HDAC inhibition promotes autophagy through activation of transcription factor EB (TFEB) (Brijmohan , et al 2018) .…”

“…The active role of gene knockout and inhibitors of HDAC6 on regulation of oxidative stress has also been proved (Shen et al, 2021, Bai et al, 2015, Ari n et al, 2015 . Inhibition of HDAC6, however, also stimulates oxidative stress in some other cells (Hattori et al, 2021) . Further investigations are prompted in terms of modulation of oxidative stress mediated by HDAC6 and the underlying mechanisms.…”