HDAC8 Inhibition Blocks SMC3 Deacetylation and Delays Cell Cycle Progression without Affecting Cohesin-dependent Transcription in MCF7 Cancer Cells

Abstract

Cohesin, a multi-subunit protein complex involved in chromosome organization, is frequently mutated or aberrantly expressed in cancer. Multiple functions of cohesin, including cell division and gene expression, highlight its potential as a novel therapeutic target. The SMC3 subunit of cohesin is acetylated (ac) during S phase to establish cohesion between replicated chromosomes. Following anaphase, ac-SMC3 is deacetylated by HDAC8. Reversal of SMC3 acetylation is imperative for recycling cohesin so that it can be reloaded in interphase for both non-mitotic and mitotic functions. We blocked deacetylation of ac-SMC3 using an HDAC8-specific inhibitor PCI-34051 in MCF7 breast cancer cells, and examined the effects on transcription of cohesin-dependent genes that respond to estrogen. HDAC8 inhibition led to accumulation of ac-SMC3 as expected, but surprisingly, had no influence on the transcription of estrogen-responsive genes that are altered by siRNA targeting of RAD21 or SMC3. Knockdown of RAD21 altered estrogen receptor ␣ (ER) recruitment at SOX4 and IL20, and affected transcription of these genes, while HDAC8 inhibition did not. Rather, inhibition of HDAC8 delayed cell cycle progression, suppressed proliferation and induced apoptosis in a concentration-dependent manner. We conclude that HDAC8 inhibition does not change the estrogen-specific transcriptional role of cohesin in MCF7 cells, but instead, compromises cell cycle progression and cell survival. Our results argue that candidate inhibitors of cohesin function may differ in their effects depending on the cellular genotype and should be thoroughly tested for predicted effects on cohesin's mechanistic roles.The cohesin complex is a chromatin-associated multi-subunit protein comprised of two SMC (structural maintenance of chromosomes, SMC1A and SMC3) 2 and two non-SMC subunits (RAD21, STAG1/2). Cohesin's canonical function establishes cohesion between replicated sister chromatids, thus ensuring their precise segregation at anaphase (1, 2). Research over the last one and a half decades has revealed that cohesin has additional cohesion-independent functions in interphase nuclei, such as chromatin organization and transcription regulation (3, 4).Recently, cancer genome sequencing projects have revealed that genes encoding cohesin subunits are frequently mutated in several different types of cancer, with particularly high frequency in acute myeloid leukemia (AML) (5-9). Recent mouse models indicate that cohesin contributes to leukemia progression likely through controlling transcription and genome organization, rather than through chromosome separation (10 -12). In breast cancer, the cohesin subunit RAD21 is overexpressed and confers poor prognosis (13,14). We previously showed that cohesin mediates transcription of the MYC gene (15-17) and modulates the transcription of estrogen-dependent genes in MCF7 breast cancer cells (18). The emergence of cohesin as an important contributor to cancer has generated interest in the development of therapeutics that compromise ...

Cooperativity of HOXA5 and STAT3 Is Critical for HDAC8 Inhibition-Mediated Transcriptional Activation of PD-L1 in Human Melanoma Cells

“…The specificity of PCI-34051 toward HDAC8 was confirmed using HDAC activity assays, which showed that treatment with the inhibitor significantly inhibited HDAC8 activity without affecting activities of other class I HDACs (Supplementary Figure S1 online) (Yang et al, 2014). As reported before (Balasubramanian et al, 2008;Dasgupta et al, 2016;Tian et al, 2015), inhibition of HDAC8 reduced melanoma cell proliferation (Supplementary Figure S2 online). However, it did not induce apoptosis (Supplementary Figure S2).…”

“…Indeed, a number of HDAC8-specific inhibitors are in early development for the treatment of cancer. For instance, the HDAC8 inhibitor PCI-34051 kills hepatocellular carcinoma (Tian et al, 2015), breast cancer cells (Dasgupta et al, 2016), T-cell lymphomas (Balasubramanian et al, 2008), and malignant peripheral nerve sheath tumors (Lopez et al, 2015) in vitro, whereas its variant PCI-48012 displays potent anti-tumor effect in preclinical neuroblastoma models (Rettig et al, 2015). Because increased PD-L1 expression resulting from HDAC8 inhibition implies a better response to treatment with anti-PD-1/PD-L1 (Chen and Han, 2015;He et al, 2015), further investigations of the combinatorial effect of HDAC8 inhibitors and anti-PD-1/PD-L1 antobodies in the treatment of cancer are clearly warranted.…”

Identification of drug targets and potential molecular mechanisms for Wantong Jingu Tablet extract in treatment of rheumatoid arthritis: bioinformatics analysis of fibroblast-like synoviocytes

“…Among the four subunits, STAG2 predominantly functions in sister chromatid cohesion and segregation. Some recent research demonstrated that a greater abundance of the STAG2 subunit in the cohesin complex assured that sister chromatid cohesion is maintained during the S phase (DNA replication) [36,37]. SMC3, a subunit of cohesion complex, is responsible for sister chromatid cohesion during mitosis and meiosis in eukaryotes.…”

“…And SMC3 inhibited cell apoptosis and promoted cell growth, migration, and invasion [38,39]. Another report found that PCI34051, a histone deacetylase 8 (HDAC8)-speci c inhibitor, blocked SMC deacetylation and thus blocked cell cycle progression and cell survival in MCF7 breast cancer cells [36].…”

Time-dependent effects of histone deacetylase inhibition in sepsis-associated acute kidney injury

“…Histone deacetylase inhibitors (HDIs) modulate a variety of biological processes through modifying histone and non-histone targets; they regulate inflammation reactions [11][12][13] and therefore may have roles in affecting outcomes from sepsis. We recently discovered a novel class of HDIs, phenylthiobutanoic acids (PTBAs), that, through modulating HDAC8, regulate cell cycle progression after injury [14]. Our previous work has shown that a PTBA prodrug, UPHD186, promotes regeneration after AKI in zebrafish [15] and decreases fibrosis in a murine AKI model even when administered days after the initial insult [16][17][18].…”