Emerging roles of AATF: Checkpoint signaling and beyond

TACE inhibition: a promising therapeutic intervention against AATF-mediated steatohepatitis to hepatocarcinogenesis

Metabolic dysfunction-associated steatohepatitis-driven hepatocellular carcinoma (MASH-HCC) is a global clinical challenge for which there is a limited understanding of disease pathogenesis and a subsequent lack of therapeutic interventions. We previously identified that tumor necrosis factor-alpha (TNF-α) upregulated apoptosis antagonizing transcription factor (AATF) in MASH. Here, we investigated the effect of TNF-α converting enzyme (TACE) inhibition as a promising targeted therapy against AATF-mediated steatohepatitis to hepatocarcinogenesis. A preclinical murine model that recapitulates human MASH-HCC was used in the study. C57Bl/6 mice were fed with chow diet normal water (CD) or western diet sugar water (WD) along with a low dose of carbon tetrachloride (CCl4; 0.2 μL·g-1, weekly) for 24 weeks. TACE activity, TNF-α levels, and AATF expression were measured. The mice were treated with the TACE inhibitor Marimastat for 12 weeks, followed by analyses of liver injury, fibrosis, inflammation, and oncogenic signaling. In vitro experiments using stable clones of AATF control and AATF knockdown were also conducted. We found that AATF expression was upregulated in WD/CCl4 mice, which developed severe MASH at 12 weeks and advanced fibrosis with HCC at 24 weeks. WD/CCl4 mice showed increased TACE activity with reduced hepatic expression of sirtuin 1 (Sirt1) and tissue inhibitor of metalloproteinase 3 (Timp3). The involvement of the SIRT1/TIMP3/TACE axis was confirmed by the release of TNF-α, which upregulated AATF, a key molecular driver of MASH-HCC. Interestingly, TACE inhibition by Marimastat reduced liver injury, dyslipidemia, AATF expression, and oncogenic signaling, effectively preventing hepatocarcinogenesis. Furthermore, Marimastat inhibited the activation of JNK, ERK1/2, and AKT, which are key regulators of tumorigenesis in WD/CCl4 mice and in AATF control cells, but had no effect on AATF knockdown cells. This study shows that TACE inhibition prevents AATF-mediated inflammation, fibrosis, and oncogenesis in MASH-HCC, offering a potential target for therapeutic intervention.

Monocytic Differentiation of Human Acute Myeloid Leukemia Cells: A Proteomic and Phosphoproteomic Comparison of FAB-M4/M5 Patients with and without Nucleophosmin 1 Mutations

Even though morphological signs of differentiation have a minimal impact on survival after intensive cytotoxic therapy for acute myeloid leukemia (AML), monocytic AML cell differentiation (i.e., classified as French/American/British (FAB) subtypes M4/M5) is associated with a different responsiveness both to Bcl-2 inhibition (decreased responsiveness) and possibly also bromodomain inhibition (increased responsiveness). FAB-M4/M5 patients are heterogeneous with regard to genetic abnormalities, even though monocytic differentiation is common for patients with Nucleophosmin 1 (NPM1) insertions/mutations; to further study the heterogeneity of FAB-M4/M5 patients we did a proteomic and phosphoproteomic comparison of FAB-M4/M5 patients with (n = 13) and without (n = 12) NPM1 mutations. The proteomic profile of NPM1-mutated FAB-M4/M5 patients was characterized by increased levels of proteins involved in the regulation of endocytosis/vesicle trafficking/organellar communication. In contrast, AML cells without NPM1 mutations were characterized by increased levels of several proteins involved in the regulation of cytoplasmic translation, including a large number of ribosomal proteins. The phosphoproteomic differences between the two groups were less extensive but reflected similar differences. To conclude, even though FAB classification/monocytic differentiation are associated with differences in responsiveness to new targeted therapies (e.g., Bcl-2 inhibition), our results shows that FAB-M4/M5 patients are heterogeneous with regard to important biological characteristics of the leukemic cells.

HAX1 is a novel binding partner of Che-1/AATF. Implications in oxidative stress cell response

HAX1 is a multifunctional protein involved in the antagonism of apoptosis in cellular response to oxidative stress. In the present study we identified HAX1 as a novel binding partner for Che-1/AATF, a pro-survival factor which plays a crucial role in fundamental processes, including response to multiple stresses and apoptosis. HAX1 and Che-1 proteins show extensive colocalization in mitochondria and we demonstrated that their association is strengthened after oxidative stress stimuli. Interestingly, in MCF-7 cells, resembling luminal estrogen receptor (ER) positive breast cancer, we found that Che-1 depletion correlates with decreased HAX1 mRNA and protein levels, and this event is not significantly affected by oxidative stress induction. Furthermore, we observed an enhancement of the previously reported interaction between HAX1 and estrogen receptor alpha (ERα) upon H2O2 treatment. These results indicate the two anti-apoptotic proteins HAX1 and Che-1 as coordinated players in cellular response to oxidative stress with a potential role in estrogen sensitive breast cancer cells.

MitomiR-1736-3p regulates copper-induced mitochondrial pathway apoptosis by inhibiting AATF in chicken hepatocytes

Copper (Cu) is a toxic heavy metal pollutant. The hepatic toxicity of Cu has attracted widespread attention from researchers. However, its underlying mechanism remains elusive. Mitochondrial microRNAs (mitomiRs) are considered important factors in regulating mitochondrial and cellular functions, and their roles have been implicated in the mechanisms of metal toxicity. Therefore, this research revealed the changes in the mitomiRs expression profile of chicken liver after Cu exposure. It was ultimately determined that mitomiR-1736-3p can be involved in Cu-induced chicken liver damage by targeting AATF. In particular, our investigations have uncovered that exposure to Cu can trigger heightened levels of apoptosis in the hepatic tissue of chickens and primary chicken embryo hepatocytes (CEHs). It is noteworthy that we found upregulation of miR-1736-3p expression can exacerbate Cu-induced cell apoptosis, while inhibition of miR-1736-3p can effectively reduce apoptosis occurrence. Subsequently, we found that Cu-induced cell apoptosis could be restored by overexpressing AATF, while silencing AATF exacerbated the level of apoptosis. Fascinatingly, this change in apoptotic level is directly influenced by AATF on Bax and Bak1, rather than on p53 and Bcl-2. Overall, these findings suggest that the mitomiR-1736-3p/AATF axis mediates the mitochondrial pathway of cell apoptosis potentially involved in Cu-induced chicken liver toxicity.

Apoptosis antagonizing transcription factor-mediated liver damage and inflammation to cancer: Therapeutic intervention by curcumin in experimental metabolic dysfunction associated steatohepatitis-hepatocellular carcinoma

In tandem with the expanding obesity pandemic, the prevalence of metabolic dysfunction associated steatohepatitis (MASH, formerly known as NASH)- driven hepatocellular carcinoma (HCC) is predicted to rise globally, creating a significant need for therapeutic interventions. We previously identified the upregulation of apoptosis antagonizing transcription factor (AATF), which is implicated in facilitating the progression from MASH to HCC. The objective of this study was to examine whether the intervention of curcumin could alleviate AATF-mediated MASH, inhibit tumor growth, and elucidate the underlying mechanism. A preclinical murine model mimicking human MASH-HCC was employed, subjecting mice to either a chow diet normal water (CDNW) or western diet sugar water (WDSW) along with very low dose of carbon tetrachloride (CCl4 - 0.2 μL/g, weekly). Mice receiving curcumin (CUR) alongside WDSW/CCl4 exhibited significant improvements, including reduced liver enzymes, dyslipidemia, steatosis, inflammation, and hepatocellular ballooning. Curcumin treatment also suppressed hepatic expression of inflammatory, fibrogenic, and oncogenic markers. Of note, there was a significant reduction in the expression of AATF upon curcumin treatment in WDSW/CCl4 mice and human HCC cells. In contrast, curcumin upregulated Kruppel-like factor 4 (KLF4) in MASH liver and HCC cells, which is known to downregulate sp1 (specificity protein-1) expression. Thus, curcumin treatment effectively inhibited the progression of MASH to HCC by downregulating the expression of AATF via the KLF4-Sp1 signaling pathway. These preclinical findings establish a novel molecular connection between curcumin and AATF in reducing hepatocarcinogenesis, and provide a strong rationale for the development of curcumin as a viable treatment for MASH-HCC in humans.

AATF inhibition exerts antiangiogenic effects against human hepatocellular carcinoma

Background and aims

Angiogenesis is a key factor in the growth and metastasis of hepatic tumors and thus a potential therapeutic target in hepatocellular carcinoma (HCC). In this study, we aim to identify the key role of apoptosis antagonizing transcription factor (AATF) in tumor angiogenesis and its underlying mechanisms in HCC.

Methods

HCC tissues were analyzed for AATF expression by qRT-PCR and immunohistochemistry. Stable clones of control and AATF knockdown (KD) were established in human HCC cells. The effect of AATF inhibition on the angiogenic processes was determined by proliferation, invasion, migration, chick chorioallantoic membrane (CAM) assay, zymography, and immunoblotting techniques.

Results

We identified high levels of AATF in human HCC tissues compared to adjacent normal liver tissues, and the expression was found to be correlated with the stages and tumor grades of HCC. Inhibiting AATF in QGY-7703 cells resulted in higher levels of pigment epithelium-derived factor (PEDF) than controls due to decreased matric metalloproteinase activity. Conditioned media from AATF KD cells inhibited the proliferation, migration, and invasion of human umbilical vein endothelial cells as well as the vascularization of the chick chorioallantoic membrane. Furthermore, the VEGF-mediated downstream signaling pathway responsible for endothelial cell survival and vascular permeability, cell proliferation, and migration favoring angiogenesis was suppressed by AATF inhibition. Notably, PEDF inhibition effectively reversed the anti-angiogenic effect of AATF KD.

Conclusion

Our study reports the first evidence that the therapeutic strategy based on the inhibition of AATF to disrupt tumor angiogenesis may serve as a promising approach for HCC treatment.

AATF Competitively Interacts with Nuclear AIF and Inhibits Parthanatos of Neurons in dMCAO/R and OGD/R Models

Ischemic stroke (IS) poses a heavy burden on the healthcare system, and revascularization is the most effective treatment. However, ischemia/reperfusion (I/R) injury, one main cause of revascularization complications, significantly hinders IS recovery. Unfortunately, none of the neuroprotectants tested to date has been successfully translated clinically for post-revascularization I/R injury therapy. In multiple pathophysiological processes, apoptosis antagonizing transcription factor (AATF) serves as a cell protector, but its role in neuronal I/R injury is unknown. Therefore, we firstly demonstrated the expression profiles of AATF in a distal middle cerebral artery occlusion/reperfusion (dMCAO/R) model and found that AATF expression was increased in cortical neuron after dMCAO/R. Over-expressing AATF reduced infarct volume, alleviated neuronal death, and promoted neurological functions. Next, we used an oxygen-glucose deprivation/reoxygenation (OGD/R) model to investigate the mechanism of AATF. Results indicated that AATF alleviated OGD/R-induced large-scale DNA fragmentation, which suggested that the protective effect of AATF may be attributed to parthanatos inhibition. After that, we examined the regulatory mechanism of AATF. We found that AATF did not affect poly (ADP-ribose) accumulation and apoptosis-inducing factor (AIF) nucleus translocation. AATF competitively interacted with nuclear AIF, which inhibited AIF from binding DNA. At last, we verified the effect and mechanism of AATF in dMCAO/R model. The present study, for the first time, demonstrates the expression, function, and mechanism of AATF in the context of neuronal I/R injury via dMCAO/R and OGD/R model, which provides new evidence in this area and may facilitate exploring new therapeutic targets.

Rcl1 suppresses tumor progression of hepatocellular carcinoma: a comprehensive analysis of bioinformatics and in vitro experiments

Background

RNA 3’-terminal phosphate cyclase-like protein (Rcl1) is involved in pre-rRNA processing, but its implication in cancers remains unclear.

Methods

RCL1 expressions in 21 malignancies was examinated through GEPIA website portal. Clinical implication data related to RCL1 level in Hepatocellular Carcinoma (HCC) samples were downloaded through TCGA, ICGC, GEO databases. Survival analysis and gene function enrichment analyses were performed through R software. The correlation between RCL1 expression and tumor immune infiltration was assessed via the TIMER2.0 database. The effects of Rcl1 overexpression or knockdown on cell growth and metastasis was evaluated by CCK8, transwell, and cell cycle assays.

Results

RCL1 expression is commonly down-regulated in HCC. The lower expression of RCL1 is associated with higher tumor stage, higher AFP level, vascular invasion, and poor prognosis. RCL1 expression has a significant correlation with immune cells infiltration in HCC, especially myeloid-derived suppressor cell (MDSC). Moreover, it was further identified that Rcl1 expression was reduced in HCC cell lines and negatively correlated with invasion of HCC cell lines. Immunofluorescence (IF) analysis revealed that the level of Rcl1 expression in the cytoplasm of HCC cells is significantly lower than that in the cytoplasm of L-02 cell. Moreover, both gain- and loss-of-function studies demonstrated that Rcl1 inhibited the growth and metastasis of HCC cells and regulated cell cycle progression in vitro.

Conclusions

Rcl1 may serve as a novel tumor suppressor in HCC, and its biological effect needs further study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02533-x.

Rcl1 mRNA expression is down-regulated within HCC tissues and associated with poor prognosis and disease progression. Anti-cancer effects of Rcl1 on HCC were confirmed in vitro. Rcl1 may be a potential tumor suppressor in HCC.

AATF is Overexpressed in Human Bladder Cancer and Regulates Chemo-Sensitivity Through Survivin

Objective

Dysregulation of apoptosis antagonizing transcription factor (AATF) has been reported to be closely associated with human cancers. However, its involvement in human bladder cancer (BC) remains unexplored. This study aimed to investigate the clinical significance and biological roles of AATF in human bladder cancers.

Methods

AATF protein expression was examined in 107 cases of bladder cancer tissues using immunohistochemistry. AATF plasmid transfection and small interfering RNA (siRNA) knockdown were performed in T24 and 5637 cell lines. CCK-8, colony formation, annexin V/PI, JC-1 staining, and Western blotting were carried out to investigate the biological roles and underlying mechanisms of AATF in bladder cancer cells.

Results

Our results showed that AATF expression was upregulated in human bladder cancer specimens and correlated with T stage. Analysis of the Oncomine database showed elevation of AATF mRNA in BC tissues. The Cancer Genome Atlas (TCGA) data suggested that high AATF expression correlated with poor patient survival. Western blotting showed that AATF protein expression was higher in BC cell lines compared to normal bladder transitional epithelial cell line SV-HUC-1. CCK-8 and colony assays showed that ectopic AATF expression upregulated cell growth rate and colony numbers. CCK-8, annexin V/propidium iodide (PI), JC-1 assays and Western blotting showed that AATF overexpression decreased cisplatin sensitivity, downregulated cisplatin-induced apoptosis and upregulated mitochondrial membrane potential, with decreased cytochrome c and cleaved-PARP expression. AATF siRNA knockdown showed the opposite effects. Mechanistically, AATF overexpression upregulated cyclin E and Survivin at both mRNA and protein levels. The decreased cisplatin sensitivity/apoptosis induced by ectopic AATF were reversed after treatment with Survivin inhibitor YM155.

Conclusion

Our results showed that AATF was overexpressed in human bladder cancers and promoted malignant behavior by regulating cyclin E and Survivin, indicating AATF could serve as a malignant biomarker and potential therapeutic target in BC.

AATF is Overexpressed in Human Head and Neck Squamous Cell Carcinoma and Regulates STAT3/Survivin Signaling

Objective

Dysregulation of apoptosis antagonizing transcription factor (AATF) has been implicated in several cancers. However, its involvement in human head and neck squamous cell carcinoma (HNSCC) remains unclear. This study aimed to explore the expression pattern and biological roles of AATF in head and neck squamous cell carcinoma tissues and cell lines.

Methods

Immunohistochemistry was used to detect the level of AATF protein in 119 cases of HNSCC samples. CCK-8, colony formation, Annexin V/PI staining, Western blotting and RNA-sequencing were carried out to examine the change of proliferation, apoptosis and potential underlying mechanisms.

Results

Immunohistochemical staining showed that AATF was elevated in HNSCC, and high AATF level correlated with higher stage. The Cancer Genome Atlas (TCGA) and Oncomine data showed upregulated AATF expression in HNSCC compared with normal tissues. TCGA data also suggested that high AATF expression correlated with poor patient survival. Ectopic AATF expression upregulated the cell growth and colony formation ability in both FaDu and Detroit 562 cell lines, while AATF siRNA decreased the cell proliferation rate and colony numbers. AATF overexpression also decreased cisplatin sensitivity, downregulated cisplatin-induced apoptosis. Mechanistically, AATF overexpression upregulated survivin, while AATF knockdown downregulated survivin. RNA-sequencing (RNA-seq) and Gene Set Enrichment Analysis (GSEA) suggested that AATF knockdown decreased STAT3 signaling. Western blotting showed that AATF overexpression upregulated while AATF knockdown downregulated STAT3 phosphorylation. There was a positive correlation between AATF and survivin mRNA based on TCGA data analysis. Blockage of STAT3 signaling using inhibitor downregulated survivin expression and largely abolished the effects of AATF on survivin.

Conclusion

Our results showed that AATF was overexpressed in human HNSCC. AATF promoted cisplatin resistance and reduced apoptosis possibly through regulation of STAT3/survivin signaling. AATF could serve as a potential therapeutic target in HNSCC.

CK2-mediated phosphorylation of Che-1/AATF is required for its pro-proliferative activity

Background

Che-1/AATF (Che-1) is an RNA polymerase II binding protein involved in several cellular processes, including proliferation, apoptosis and response to stress. We have recently demonstrated that Che-1 is able to promote cell proliferation by sustaining global histone acetylation in multiple myeloma (MM) cells where it interacts with histone proteins and competes with HDAC class I members for binding.

Methods

Site-directed Mutagenesis was performed to generate a Che-1 mutant (Che-1 3S) lacking three serine residues (Ser³¹⁶, Ser³²⁰ and Ser³²¹) in 308–325 aa region. Western blot experiments were conducted to examine the effect of depletion or over-expression of Che-1 and Che-1 3S mutant on histone acetylation, in different human cancer cell lines. Proliferation assays were assessed to estimate the change in cells number when Che-1 was over-expressed or deleted. Immunoprecipitation assays were performed to evaluate Che-1/histone H3 interaction when Ser³¹⁶, Ser³²⁰ and Ser³²¹ were removed. The involvement of CK2 kinase in Che-1 phosphorylation at these residues was analysed by in vitro kinase, 2D gel electrophoresis assays and mass spectrometry analysis.

Results

Here, we confirmed that Che-1 depletion reduces cell proliferation with a concomitant general histone deacetylation in several tumor cell lines. Furthermore, we provided evidence that CK2 protein kinase phosphorylates Che-1 at Ser³¹⁶, Ser³²⁰ and Ser³²¹ and that these modifications are required for Che-1/histone H3 binding. These results improve our understanding onto the mechanisms by which Che-1 regulates histone acetylation and cell proliferation.

Conclusions

Che-1 phosphorylation at Ser³¹⁶, Ser³²⁰ and Ser³²¹ by CK2 promotes the interaction with histone H3 and represents an essential requirement for Che-1 pro-proliferative ability.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02038-x.

Fenofibrate Exerts Antitumor Effects in Colon Cancer via Regulation of DNMT1 and CDKN2A

Peroxisome proliferator-activated receptor alpha (PPARA) is the molecular target of fibrates commonly used to treat dyslipidemia and diabetes. Recently, the potential role of PPARA in other pathological conditions, such as cancers, has been recognized. Here, using bioinformatics analysis, we found that PPARA was expressed at relatively low levels in pancancers, and Kaplan-Meier analyses revealed that high PPARA protein expression was correlated with better survival of patients with colon cancer. In vitro experiments showed that fenofibrate regulated cell cycle distribution, promoted apoptosis, and suppressed cell proliferation and epithelial mesenchymal transition by activating PPARA. PPARA activation inhibited DNMT1 activity and abolished methylation-mediated CDKN2A repression. Downregulation of cyclin-CDK complexes led to the restoration of CDKN2A, which caused cell cycle arrest in the G1 phase via regulation of the CDKN2A/RB/E2F pathway. Finally, we demonstrated that fenofibrate administration inhibited tumor growth and DNMT1 activity in vivo. The PPARA agonist, fenofibrate, might serve as an applicable agent for epigenetic therapy of colon cancer patients.