ATPase Family, AAA Domain Containing 2 Research Articles

Impact of Combinatorial Histone Modifications on Acetyllysine Recognition by the ATAD2 and ATAD2B Bromodomains.

The ATPase family AAA+ domain containing 2 (ATAD2) protein and its paralog ATAD2B have a C-terminal bromodomain (BRD) that functions as a reader of acetylated lysine residues on histone proteins. Using a structure-function approach, we investigated the ability of the ATAD2/B BRDs to select acetylated lysine among multiple histone post-translational modifications. The ATAD2B BRD can bind acetylated histone ligands that also contain adjacent methylation or phosphorylation marks, while the presence of these modifications significantly weakened the acetyllysine binding activity of the ATAD2 BRD. Our structural studies provide mechanistic insights into how ATAD2/B BRD-binding pocket residues coordinate the acetyllysine group in the context of adjacent post-translational modifications. Furthermore, we investigated how sequence changes in amino acids of the histone ligands impact the recognition of an adjacent acetyllysine residue. Our study highlights how the interplay between multiple combinations of histone modifications influences the reader activity of the ATAD2/B BRDs, resulting in distinct binding modes.

ATAD2 is a driver and a therapeutic target in ovarian cancer that functions by upregulating CENPE

Ovarian cancer is a complex disease associated with multiple genetic and epigenetic alterations. The emergence of treatment resistance in most patients causes ovarian cancer to become incurable, and novel therapies remain necessary. We identified epigenetic regulator ATPase family AAA domain-containing 2 (ATAD2) is overexpressed in ovarian cancer and is associated with increased incidences of metastasis and recurrence. Genetic knockdown of ATAD2 or its pharmacological inhibition via ATAD2 inhibitor BAY-850 suppressed ovarian cancer growth and metastasis in both in vitro and in vivo models. Transcriptome-wide mRNA expression profiling of ovarian cancer cells treated with BAY-850 revealed that ATAD2 inhibition predominantly alters the expression of centromere regulatory genes, particularly centromere protein E (CENPE). In ovarian cancer cells, changes in CENPE expression following ATAD2 inhibition resulted in cell-cycle arrest and apoptosis induction, which led to the suppression of ovarian cancer growth. Pharmacological CENPE inhibition phenotypically recapitulated the cellular changes induced by ATAD2 inhibition, and combined pharmacological inhibition of both ATAD2 and CENPE inhibited ovarian cancer cell growth more potently than inhibition of either alone. Thus, our study identified ATAD2 as regulators of ovarian cancer growth and metastasis that can be targeted either alone or in combination with CENPE inhibitors for effective ovarian cancer therapy.

Identification of POLQ as a key gene in cervical cancer progression using integrated bioinformatics analysis and experimental validation.

As the most common gynecologic malignancy worldwide, cervical cancer (CC) is a serious hazard to health. Therefore, the present study aimed to identify the key genes in CC progression using integrated bioinformatics analysis and experimental validation. The mRNA microarray GSE63514 and microRNA (miRNA) microarray GSE86100 were obtained from the Gene Expression Omnibus database, and the differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) in the progression of CC were identified. Thereafter, GO and KEGG functional enrichment analysis, protein‑protein interaction (PPI) network and significant subnetworks construction, and miRNA‑target regulatory network construction were performed. Based on the results of integrated bioinformatics analysis, the DEGs structural maintenance of chromosomes 4 (SMC4), ATPase family, AAA domain‑containing 2 (ATAD2) and DNA polymerase θ (POLQ) were identified as hub genes in the PPI network and were involved in the first significant subnetwork. In addition, these DEGs were predicted to be regulated by miR‑106B, miR‑17‑5P, miR‑20A and miR‑20B, which were identified as DEMs. Of note, SMC4 and ATAD2 are tumor‑promotors in CC. In the present study, small interfering (si)RNAs were used to knock down POLQ expression. Cell Counting Kit‑8, Transwell, cell cycle and apoptosis analyses revealed that the downregulation of POLQ restrained cell proliferation, migration and invasion, and promoted apoptosis and the arrest of the cell cycle in the G2 phase. In conclusion, POLQ, which may have a close interaction with SMC4 and ATAD2, may serve a vital role in the progression of CC.

ATAD2 suppression enhances the combinatorial effect of gemcitabine and radiation in pancreatic cancer cells

Amalgamation of target-based approach along with chemo and/or radiotherapy could be an effective strategy to combat pancreatic cancer (PC). ATAD2 (ATPase family AAA domain containing 2) is a potential oncoprotein and a poor prognostic factor in PC. ATAD2 inhibition sensitizes pancreatic cancer cells (PCCs) to gemcitabine (GEM). ATAD2 silencing also enhances radio-sensitivity in lung cancer cells. We therefore hypothesise that ATAD2 suppression along with application of GEM and radiation could show additive/synergistic response in reducing PC progression. At first, immunofluorescence and western blot analysis are carried out to investigate ATAD2 expression upon irradiation in PCCs (BxPC3, and PANC1). Colony forming assay is performed to analyse the radio-sensitization effect of ATAD2 suppressed PCCs in absence and presence of GEM. To evaluate the consequences of irradiation, expression of markers for DNA damage and repair as well as apoptosis and autophagy are also assessed. Results indicate that ATAD2 is elevated in irradiated PCCs. Silencing ATAD2 sensitizes PCCs to radiation. Survival fraction analysis of PCCs shows that combination treatment of GEM and radiation (with minimal doses) is more effective when ATAD2 is suppressed. Further, when GEM-radiation combination is applied to ATAD2 silenced PCCs, expression of DNA damage marker like γH2AX is induced, whereas DNA damage repair proteins (pChk1, and pChk2) are downregulated. Moreover, ATAD2 suppressed PCCs are more susceptible to apoptosis and autophagy in presence of radiation and GEM. Collectively, these findings support our hypothesis and demonstrate that targeting ATAD2 enhances efficacy of GEM-radiation treatment in PCCs.

Proteolysis of a histone acetyl reader, ATAD2, induces chemoresistance of cancer cells under severe hypoxia by inhibiting cell cycle progression in S phase.

Cancer cells acquire chemoresistance in hypoxic regions of solid tumors, which is suggested to be at least partly due to reduction of their proliferative activity. However, molecular mechanisms behind it have not been fully elucidated. Here, we revealed the importance of active proteolysis of a histone acetylation reader, ATPase family AAA domain containing 2 (ATAD2), under hypoxia. We found that inactivation of an O2/Fe2+/α-ketoglutarate-dependent dioxygenase triggered ATAD2 proteolysis by the proteasome system upon severe hypoxia in a hypoxia-inducible factors (HIFs)-independent manner. Consistently, ATAD2 expression levels were markedly lower in perinecrotic hypoxic regions in both xenografted and clinical tumor tissues. The ATAD2 proteolysis was accompanied by a decrease in the amount of acetylated histone H3 lysine 27 and inhibited cell cycle progression from the early to late S phase under severe hypoxia. The retardation of S phase progression induced chemoresistance, which was blocked by overexpression of ATAD2. Together, these results indicate that ATAD2 proteolysis upon severe hypoxia induces chemoresistance of cancer cells through heterochromatinization and the subsequent retardation of S phase progression; therefore, inhibition of ATAD2 proteolysis is expected to be a strategy to overcome chemoresistance of hypoxic tumor cells.

LncRNA MALAT1 regulated ATAD2 to facilitate retinoblastoma progression via miR-655-3p.

Long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was reported as an oncogene in many tumors including retinoblastoma (RB). This research mainly focused on the functions and mechanism of MALAT1 in RB. MALAT1 was upregulated in RB tissues and cells, and it served as a competing endogenous RNA (ceRNA) and inhibited miRNA-655-3p (miR-655-3p) expression, which eventually regulated the expression of miR-655-3p downstream target ATPase Family AAA Domain Containing 2 (ATAD2). The level of ATAD2 significantly increased, while that of miR-655-3p remarkably decreased in RB tissues and cells. MALAT1 depletion inhibited cell proliferation, metastasis, and epithelial–mesenchymal transition (EMT), but promoted apoptosis in vitro and blocked xenograft tumor growth in vivo. MALAT1 exerted its oncogenic functions in RB by regulating miR-655-3p/ATAD2 axis.

MiR-200b-5p inhibits proliferation of ovarian cancer cells by targeting ATAD2 and regulating PI3K/AKT signaling pathway.

The purpose of this study was to investigate the influences of micro ribonucleic acid (miR)-200b-5p on proliferation and apoptosis of ovarian cancer (OC) cells, and to explore its correlations with the target gene ATPase family, AAA domain containing 2 (ATAD2), and the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Human ovarian fibroblasts (HOFs) or human OC cell lines (A2780) were cultured in vitro, and then, A2780 cells were separately transfected with miR-200b mimics or miR-NC or cultured with ATAD2-specific inhibitor BAY-850. Thereafter, the expression levels of miR-200b and ATAD2 messenger RNA (mRNA) were measured via qRT-PCR, and the proliferative capacity of cells was detected by CCK-8 assay. Next, the cell apoptosis was determined by means of flow cytometry and one-step TUNEL assay. Finally, the targeted regulatory relationship between miR-200b and ATAD2 was examined using a Luciferase reporter assay system, and the protein expressions were detected through Western blot (WB) assay. It was found that the expression level of miR-200b was remarkably lower (p<0.05), while the mRNA expression level of ATAD2 was notably higher (p<0.05) in A2780 cells than those in HOFs. The transfection with miR-200b mimics markedly reduced the mRNA expression level of ATAD2 (p<0.05) and the proliferative capacity (p<0.05) and increased the apoptosis rate (p<0.05) of A2780 cells. Besides, it was detected via the Luciferase reporter assay system that miR-200b inhibited ATAD2. BAY-850 significantly decreased the expression level of ATAD2 protein (p<0.05) and the proliferative capacity (p<0.05) but improved the apoptosis rate (p<0.05) of cells. Moreover, both miR-200b mimics and BAY-850 could distinctly repress the protein expression levels of PI3K and p-Akt of the PI3K/Akt signaling pathway (p<0.05) and enhance the expression of suppressor gene p53 (p<0.05). MiR-200b-5p can inhibit the proliferation and promote the apoptosis of OC cells through targeted inhibition of ATAD2 expression and regulation of the PI3K/Akt signaling pathway.

Silence of ATAD2 inhibits proliferation of colorectal carcinoma via the Rb-E2F1 signaling.

This study aims to clarify the potential function of ATAD2 (ATPase family, AAA domain containing 2) in regulating proliferative and apoptotic abilities of colorectal carcinoma (CRC). ATAD2 levels in CRC specimens and cell lines were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Overall survival in CRC patients with high or low level of ATAD2 was assessed by Kaplan-Meier method. The correlation between ATAD2 level and clinical characteristics of CRC patients was analyzed by χ2 test. Univariable and multivariable Cox regression models were generated to illustrate potential risk factors for the overall survival of CRC. After knockdown of ATAD2 in SW620 cells, relative levels of Cyclin D1, ppRb, pRb, E2F1, Cyclin E and cleaved Caspase 3 were detected by Western blot. Regulatory effects of ATAD2 on viability, clonality, cell cycle distribution, and apoptosis in SW620 and HCT15 cells were examined by a series of functional experiments. Upregulated ATAD2 in CRC was correlated to tumor size, tumor node metastasis (TNM) staging, and histological classification of CRC. High level of ATAD2 predicted poor prognosis in CRC patients. Cox regression test suggested that ATAD2 level, tumor size, TNM staging and histological classification were independent factors influencing overall survival in CRC. Knockdown of ATAD2 reduced viability and clonality in SW620 and HCT15 cells. In addition, cell cycle was arrested in G1 phase and apoptosis was stimulated in CRC cells with ATAD2 knockdown. In SW620 cells transfected with ATAD2 shRNA, protein levels of Cyclin D1, ppRb, E2F1 and Cyclin E were downregulated, and cleaved Caspase 3 was upregulated. ATAD2 is upregulated in CRC tissues and correlated to poor prognosis of CRC patients. It exerts an anti-proliferation role in CRC by arresting cell cycle in G1/S phase and triggering apoptosis via the Rb-E2F1 signaling.

Optimization of Potent ATAD2 and CECR2 Bromodomain Inhibitors with an Atypical Binding Mode.

Most bromodomain inhibitors mimic the interactions of the natural acetylated lysine (KAc) histone substrate through key interactions with conserved asparagine and tyrosine residues within the binding pocket. Herein we report the optimization of a series of phenyl sulfonamides that exhibit a novel mode of binding to non-bromodomain and extra terminal domain (non-BET) bromodomains through displacement of a normally conserved network of four water molecules. Starting from an initial hit molecule, we report its divergent optimization toward the ATPase family AAA domain containing 2 (ATAD2) and cat eye syndrome chromosome region, candidate 2 (CECR2) domains. This work concludes with the identification of (R)-55 (GSK232), a highly selective, cellularly penetrant CECR2 inhibitor with excellent physicochemical properties.

Silencing METTL3 inhibits the proliferation and invasion of osteosarcoma by regulating ATAD2

BackgroundOsteosarcoma is the most common primary malignant bone tumor in children and young adults. RNA N6-methyladenosine (m6A) is the most abundant internal modification in mammalian mRNA, which is involved in tumorigenesis and tumor progression. It has been reported that methyltransferase-like 3 (METTL3), the first reported m6A “writer”, plays critical roles in cancer progression. However, its role and molecular mechanism in osteosarcoma is poor studied. In this study, we aimed to investigate the functional role and underlying mechanism of METTL3 in the progression of osteosarcoma. MethodsWe detected the mRNA expression of METTL3 in osteosarcoma cell lines, and immunofluorescence assay was performed to observe the location of METTL3. Cell lines with METTL3 gene overexpression or knockdown were established by pcDNA3.1-METTL3 or siRNA interferences in order to determine the function of METTL3 in osteosarcoma in vitro. Transcriptomic RNA sequencing (RNA-seq) were used to screen the target genes of METTL3 in osteosarcoma. ResultsWe found that METTL3 localized in cytoplasm and nucleus of osteosarcoma cells. Silencing METTL3 in SAOS-2 and MG63 cells significantly inhibited the m6A methylation level, proliferation, migration, and invasion abilities, as well as promoted cell apoptosis. However, up-regulation of METTL3 had no significant effect on the biological behaviors of U2OS cells. Further mechanism analysis suggested that METTL3 knockdown inhibited the expression of ATPase family AAA domain containing 2 (ATAD2). Moreover, ATAD2 knockdown inhibited the proliferation and invasion of SAOS-2 and MG63 cells, while its overexpression showed a significant increase in cell proliferation and invasion. Furthermore, METTL3 knockdown abrogated the promoting effects of ATAD2 overexpression on osteosarcoma cells proliferation and invasion. ConclusionOverall, our study revealed that METTL3 functions as an oncogene in the growth and invasion of osteosarcoma by regulating ATAD2, suggesting a potential therapeutic target for osteosarcoma treatment.

Immunohistochemical Determination of ATAD2 Protein Overexpression for Predicting Prognostic Value in Patients with Different Types of Cancer: A Meta-Analysis

Background: Increasing number of studies has reported that Atpase family AAA domain-containing 2 (ATAD2) is nuclear coactivator, which is associated with tumor cell proliferation and invasion. Previous studies have demonstrated conflicting results on the relationship between high ATAD2 expression and clinicopathological characteristics of the tumors or patients’ survival outcomes. Considering the discordant results of published studies, we performed a metaanalysis to evaluate the ATAD2 expression in predicting prognosis, and to assess the relationship between high ATAD2 expression and clinicopathological parameters.Methods: We systematically searched electronic database of PubMed, Web of Science and Embase, and selected all immunohistochemical studies of hepatocellular cancer specimens for ATAD2, to analyze the relationship between high ATAD2 expression and prognosis of hepatocellular cancer patients. Pooled data of eligible studies together from individual studies and analyzed data using STATA software to perform this meta-analysis.Results: A total of 5 studies with 719 liver cancer patients were included. ATAD2 protein overexpression wassignificantly correlated with poorer overall survival (HR 3.53, 95% CI: 1.87-6.63, P = 0.000). In addition, high ATAD2 expression was also negatively related with tumor stage [RR, relative risk: 1.46 (95% CI: 1.30-1.64); P &lt; 0.001], as well as tumor size [RR: 1.23(95% CI: 1.06-1.43); P &lt; 0.001], and tumor recurrence [RR: 1.34 (95% CI: 1.05-1.72); P &lt; 0.001].Conclusions: These data suggested that immunohistochemical determination of ATAD2 Protein might be aprognostic biomarker for the patients of hepatocellular cancer.

Gene expression profiling of the 8q22-24 position in human breast cancer: TSPYL5, MTDH, ATAD2 and CCNE2 genes are implicated in oncogenesis, while WISP1 and EXT1 genes may predict a risk of metastasis.

Gene expression profiling has been suggested to predict breast cancer outcome. The prognostic value of the 8q22-24 position in breast cancer remains to be elucidated. The present study evaluated expression patterns of the genes located at this position in metastatic and non-metastatic breast cancer. A total of 85 patients with recurrent/metastatic (n=15) and non-metastatic (n=70) early-stage, estrogen receptor-positive and lymph node-negative breast tumors were included. In addition, 15 normal breast tissue samples were used as controls. Demographic and clinical features were recorded. Subsequently, mRNA copy numbers of exostosin glycosyltransferase 1 (EXT1), WNT1 inducible signaling pathway protein 1 (WISP1), ATPase family, AAA domain containing 2 (ATAD2), TSP-like 5 (TSPYL5), metadherin (MTDH) and cyclin E2 (CCNE2) genes were measured by reverse transcription-quantitative polymerase chain reaction assay. The expression of EXT1 and WISP1 exhibited a significant decline in the metastatic breast cancer group compared to the control (P=0.015 and P=0.012, respectively). The expression of TSPYL5, MTDH and ATAD2 was significantly decreased in the metastatic (P=0.002, P=0.018 and P=0.016, respectively) and non-metastatic (P=0.038, P=0.045 and P=0.000, respectively) breast cancer groups compared with the control. The expression of CCNE2 in the metastatic and non-metastatic breast cancer groups was significantly increased compared with the control (P=0.002 and P=0.001, respectively). WISP1 expression demonstrated a correlation with patient age and tumor size, and TSPYL5 expression was correlated with lymphovascular invasion. None of the genes investigated exhibited any correlation with stage and grade of disease. The TSPYL5, MTDH, ATAD2 and CCNE2 genes may be implicated in the pathogenesis of human breast cancer, while the WISP1 and EXT1 genes may have the potential to serve as promising indicators of the risk of metastasis. However, further studies are required to validate these results.

ATAD2 is overexpressed in gastric cancer and serves as an independent poor prognostic biomarker.

ATPase family, AAA domain containing 2 (ATAD2) has been found overexpressed in various cancer types and correlated with malignant status and poor prognosis. However, little is known about the clinical significance of ATAD2 in gastric cancer patients. The aim of this study was to explore the clinical and prognostic significance of ATAD2 in gastric cancer. The mRNA and protein levels expression of ATAD2 were detected in clinical tissue samples by qRT-PCR and immunohistochemistry, respectively. We examined the ATAD2 protein expression by immunohistochemistry. Furthermore, we analyzed the association between ATAD2 expression and clinicopathological features including prognosis in 166 gastric cancer samples. In our results, ATAD2 mRNA and protein were highly expressed in gastric cancer samples. ATAD2 overexpression was correlated with advanced clinical stage, tumor depth, lymph node metastasis, and distant metastasis. According to the survival analysis, ATAD2 protein overexpression was a poor independent prognostic factor for gastric cancer patients. In summary, ATAD2 could serve as a prognostic biomarker for gastric cancer patients.

Suppression of ATAD2 inhibits hepatocellular carcinoma progression through activation of p53- and p38-mediated apoptotic signaling.

The ATPase family, AAA domain containing 2 (ATAD2) is highly expressed in multiple cancers. We aim to understand the clinical and biological significance of ATAD2 over-expression in hepatocellular carcinoma (HCC), as a means to validate it as a therapeutic target in HCC. We demonstrated that ATAD2 was over-expressed in HCC patients, where high ATAD2 levels were significantly correlated with aggressive phenotypes such as high AFP levels, advanced tumor stages, and vascular invasion. Using RNA interference, suppression of ATAD2 in HCC cell lines decreased cell viability, migration, and invasion, and induced apoptosis in vitro. Furthermore, we identified p53 and p38 as key proteins that mediate apoptosis induced by ATAD2 suppression. In HCC cells, we demonstrated that ATAD2 directly interacted with MKK3/6, which prevented p38 activation and therefore inhibited p38-mediated apoptosis. In vivo, suppression of ATAD2 impaired the growth of HepG2 and Hep3B subcutaneous xenografts, accompanied by enhanced apoptosis and p-p53 and p-p38 levels. Our results validate that ATAD2 is an important negative regulator of apoptosis, and that neutralizing its activity has promising anti-tumor effects in HCC cells.

Fragment-Based Discovery of Low-Micromolar ATAD2 Bromodomain Inhibitors.

Overexpression of ATAD2 (ATPase family, AAA domain containing 2) has been linked to disease severity and progression in a wide range of cancers, and is implicated in the regulation of several drivers of cancer growth. Little is known of the dependence of these effects upon the ATAD2 bromodomain, which has been categorized as among the least tractable of its class. The absence of any potent, selective inhibitors limits clear understanding of the therapeutic potential of the bromodomain. Here, we describe the discovery of a hit from a fragment-based targeted array. Optimization of this produced the first known micromolar inhibitors of the ATAD2 bromodomain.

ATAD2 as a Poor Prognostic Marker for Hepatocellular Carcinoma after Curative Resection.

PurposeCancer cells frequently express genes that are specifically or preferentially expressed in male germ cells under normal conditions. The ATPase family AAA domain-containing 2 (ATAD2) is one such and works as an important cofactor for MYC-dependent transcription. In hepatocellular carcinoma (HCC), ATAD2 has been identified as a candidate driver gene located within the amplified 8q24 locus. However, the prognostic significance of ATAD2 protein expression in HCC remains uncertain.Materials and MethodsWe investigated ATAD2 protein expression by immunohistochemistry in tumor tissue from 182 HCC patients who underwent curative resection. Associations of ATAD2 expression with clinicopathologic variables or prognosis of HCC patients were analyzed.ResultsATAD2 expression was observed in 119 (65.4%) of the 182 HCCs and tended to be independent predictor of early recurrence (p=0.059). ATAD2 expression showed an unfavorable influence on recurrence-free survival (RFS) (p < 0.001). Subgroup analysis among patients with tumor size ≤ 5.0 cm (n=109), patients at Barcelona Clinic Liver Cancer stage 0 or A (n=92), and patients with α-fetoprotein ≤ 20 ng/mL (n=61), the ATAD2-positive groups unfavorably influenced RFS (p=0.008, p=0.009, and p=0.013, respectively). In addition, ATAD2 expression was an independent predictor of shorter RFS (p=0.002). ATAD2 expression showed an unfavorable influence on disease-specific survival (p=0.001), but was not an independent predictor of shorter disease-specific survival (p=0.109).ConclusionATAD2 protein expression may be a potential predictor of RFS in HCC patients after curative resection and ATAD2 may have prognostic value in patients with early stage HCC or normal serum α-fetoprotein level.

ATAD2 Overexpression Identifies Colorectal Cancer Patients with Poor Prognosis and Drives Proliferation of Cancer Cells.

ATPase family AAA domain-containing 2 (ATAD2) has been identified as a critical modulator involved in cell proliferation and invasion. The purpose of this study was to explore the expression of ATAD2 in CRC tissues as well as its relationship with degree of malignancy. Data containing three independent investigations from Oncomine database demonstrated that ATAD2 is overexpressed in CRC compared with normal tissue, and similar result was also found in 32 pairs of CRC tissues by qPCR. The protein expression of ATAD2 was examined in six CRC cell lines and 300 CRC specimens. The results showed that high expression of ATAD2 was significantly correlated with tumor size (P < 0.001), serum CEA (P = 0.012), lymph node metastasis (P = 0.018), liver metastasis (P = 0.025), and clinical stage (P = 0.004). Kaplan-Meier method suggested that higher ATAD2 protein expression significantly associated with the overall survival (OS) of CRC patients (P < 0.001) and was an independent predictor of poor OS. Functional studies showed that suppression of ATAD2 expression with siRNA could significantly inhibit the growth in SW480 and HCT116 cells. These results indicated that ATAD2 could serve as a prognostic marker and a therapeutic target for CRC.