The histone deacetylase inhibitor SAHA induces HSP60 nitration and its extracellular release by exosomal vesicles in human lung-derived carcinoma cells

Abstract

HSP60 undergoes changes in quantity and distribution in some types of tumors suggesting a participation of the chaperonin in the mechanism of transformation and cancer progression. Suberoylanilide hydroxamic acid (SAHA), a member of a family of histone deacetylase inhibitors (HDACi), has anti-cancer potential but its interaction, if any, with HSP60 has not been elucidated. We investigated the effects of SAHA in a human lung-derived carcinoma cell line (H292). We analysed cell viability and cycle; oxidative stress markers; mitochondrial integrity; HSP60 protein and mRNA levels; and HSP60 post-translational modifications, and its secretion. We found that SAHA is cytotoxic for H292 cells, interrupting the cycle at the G2/M phase, which is followed by death; cytotoxicity is associated with oxidative stress, mitochondrial damage, and diminution of intracellular levels of HSP60; HSP60 undergoes a post-translational modification and becomes nitrated; and nitrated HSP60 is exported via exosomes. We propose that SAHA causes ROS overproduction and mitochondrial dysfunction, which leads to HSP60 nitration and release into the intercellular space and circulation to interact with the immune system. These successive steps might constitute the mechanism of the anti-tumor action of SAHA and provide a basis to design supplementary therapeutic strategies targeting HSP60, which would be more efficacious than the compound alone.

The dissociation of the Hsp60/pro-Caspase-3 complex by bis(pyridyl)oxadiazole copper complex ( CubipyOXA ) leads to cell death in NCI-H292 cancer cells

“…For instance, the biological activity of a copper complex with oxadiazoles has been studied in two cancer-cell models [11]. A copper complex reduced the viability of HepG2 and HT29 cells in a dose-and time-dependent manner and the cells showed signs of apoptosis.…”

“…This could regulate the degradation of the chaperone by the ubiquitin-proteosome system [12,55]. Otherwise, the post-translational modifications could constitute a signal for extracellular secretion through the lipid raft pathway [11,49,56]. The function of extracellular Hsp60 is still under discussion.…”

“…The function of extracellular Hsp60 is still under discussion. For instance, it may mediate interactions with the immune cells and other body tissues and alter the tumor microenvironment [11,12,55,57].…”

“…The synthesis of the copper and zinc complexes [11] was performed by mixing a solution of the metal as perchlorate salt, with the bipyOXA ligand in ethanol (Fig. 1A).…”

“…Our recent studies have shown that the induction of stress on cancer cells affects the Hsp60 levels [6,11,12] and it is known that this chaperone plays a crucial role in apoptosis. Furthermore, we found that Hsp60 interacts with Pro-Caspase-3 (pC3) in the mucoepidermoid carcinoma cell line NCI-H292 and this association persists after the induction of oxidative stress [5].…”