HDAC‐inhibitor (S)‐8 disrupts HDAC6‐PP1 complex prompting A375 melanoma cell growth arrest and apoptosis

Abstract

Histone deacetylase inhibitors (HDACi) are agents capable of inducing growth arrest and apoptosis in different tumour cell types. Previously, we reported a series of novel HDACi obtained by hybridizing SAHA or oxamflatin with 1,4-benzodiazepines. Some of these hybrids proved effective against haematological and solid cancer cells and, above all, compound (S)-8 has emerged for its activities in various biological systems. Here, we describe the effectiveness of (S)-8 against highly metastatic human A375 melanoma cells by using normal PIG1 melanocytes as control. (S)-8 prompted: acetylation of histones H3/H4 and α-tubulin; G0/G1 and G2/M cell cycle arrest by rising p21 and hypophos-phorylated RB levels; apoptosis involving the cleavage of PARP and caspase 9, BAD protein augmentation and cytochrome c release; decrease in cell motility, invasiveness and pro-angiogenic potential as shown by results of wound-healing assay, down-regulation of MMP-2 and VEGF-A/VEGF-R2, besides TIMP-1/TIMP-2 up-regulation; and also intracellular accumulation of melanin and neutral lipids. The pan-caspase inhibitor Z-VAD-fmk, but not the antioxidant N-acetyl-cysteine, contrasted these events. Mechanistically, (S)-8 allows the disruption of cytoplasmic HDAC6-protein phosphatase 1 (PP1) complex in A375 cells thus releasing the active PP1 that dephosphorylates AKT and blocks its downstream pro-survival signalling. This view is consistent with results obtained by: inhibiting PP1 with Calyculin A; using PPP1R2-transfected cells with impaired PP1 activity; monitoring drug-induced HDAC6-PP1 complex re-shuffling; and, abrogating HDAC6 expression with specific siRNA. Altogether, (S)-8 proved very effective against melanoma A375 cells, but not normal melanocytes, and safe to normal mice thus offering attractive clinical prospects for treating this aggressive malignancy.

Inhibition of polypyrimidine tract-binding protein 3 induces apoptosis and cell cycle arrest, and enhances the cytotoxicity of 5- fluorouracil in gastric cancer cells

“…Furthermore, PTB knockdown improved the phosphorylation of Akt (Figure 5E). Among all the proteins whose mRNA has been identified to physically interact with PTBP3 (Brazão et al , 2012), HDAC6 has been reported to be a regulator of p-Akt level (Balliu et al , 2015). We thus tested whether HDAC6 mediated PTBP3 inhibition-induced cell chemosensitisation.…”

“…Indeed, HDAC6 has been reported to form a complex with protein phosphatase 1 (PP1). Disruption of HDAC6/PP1 complex released active PP1 which could dephosphorylate Akt (Balliu et al , 2015). Inhibition of Akt was found to decrease the expression of TYMS (Ahn et al , 2015), critical determinant of 5-FU sensitivity in cancers.…”

Histone Deacetylase Inhibitors as Anticancer Drugs

“…A decrease in HDAC activity alters expression of MHC (Major histocompatibility complex) and costimulatory molecules [ 118 , 119 ]. The subsequent increase in immunogenicity intensifies activation of T cells and the prolonged survival of experimental animals [ 120 , 121 ].…”

2-Methylquinazoline derivative 23BB as a highly selective histone deacetylase 6 inhibitor alleviated cisplatin-induced acute kidney injury

“…HDAC6 is a unique histone deacetylase harboring two active N-terminal deacetylating domains and a C-terminal ubiquitin-binding domain [26,27]. HDAC6, which is primarily expressed in the cytoplasm, clears the acetyl group from lysine residues in a number of non-histone substrates, including α-tubulin, stress granules and HSP90 [14,28,29]. Aberrant expression of HDAC6 is involved in several physiological processes such as stress response (ER stress), apoptosis and autophagy that play crucial roles in tumors, neurodegenerative disorders, inflammation and kidney diseases [15,30,31].…”

“…Multiple cellular functions, including cell apoptosis, were modulated by the acetylation of histone and non-histone proteins. An acetylation could be added to a lysine residue by histone acetyl transferases and be cleaved by histone deacetylases (HDACs) [14]. HDACs were classified based on their structure and homology: class I (HDAC1, 2, 3 and 8); class II (HDAC4, 5, 6, 7, 9 and 10); class III (SIRT1-7); and class IV (HDAC11) [15].…”