Inhibition of TAF1B impairs ribosome biosynthesis and suppresses cell proliferation in stomach adenocarcinoma through promoting c-MYC mRNA degradation.

Hyperactivation of ribosome biosynthesis (RiBi) is a hallmark of cancer, and targeting ribosome biogenesis has emerged as a potential therapeutic strategy. The depletion of TAF1B, a major component of selectivity factor 1 (SL1), disrupts the pre-initiation complex, preventing RNA polymerase I from binding ribosomal DNA and inhibiting the hyperactivation of RiBi. Here, we investigate the role of TAF1B, in regulating RiBi and proliferation in stomach adenocarcinoma (STAD). We disclosed that the overexpression of TAF1B correlates with poor prognosis in STAD, and found that knocking down TAF1B effectively inhibits STAD cell proliferation and survival in vitro and in vivo. TAF1B knockdown may also induce nucleolar stress, and promote c-MYC degradation in STAD cells. Furthermore, we demonstrate that TAF1B depletion impairs rRNA gene transcription and processing, leading to reduced ribosome biogenesis. Collectively, our findings suggest that TAF1B may serve as a potential therapeutic target for STAD and highlight the importance of RiBi in cancer progression.

TAF1B depletion leads to apoptotic cell death by inducing nucleolar stress and activating p53-miR-101 circuit in hepatocellular carcinoma.

Background: TAF1B (TATA Box Binding Protein (TBP)-Associated Factor) is an RNA polymerase regulating rDNA activity, stress response, and cell cycle. However, the function of TAF1B in the progression of hepatocellular carcinoma (HCC) is unknown. Objective: In this study, we intended to characterize the crucial role and molecular mechanisms of TAF1B in modulating nucleolar stress in HCC. Methods: We analyzed the differential expression and prognostic value of TAF1B in hepatocellular carcinoma based on The Cancer Genome Atlas (TCGA) database, tumor and paraneoplastic tissue samples from clinical hepatocellular carcinoma patients, and typical hepatocellular carcinoma. We detected cell proliferation and apoptosis by lentiviral knockdown of TAF1B expression levels in HepG2 and SMMC-7721 cells using clone formation, apoptosis, and Western blotting (WB) detection of apoptosis marker proteins. Simultaneously, we investigated the influence of TAF1B knockdown on the function of the pre-initiation complex (PIC) by WB, and co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation (ChIP) assays verified the interaction between the complexes and the effect on rDNA activity. Immunofluorescence assays measured the expression of marker proteins of nucleolus stress, fluorescence in situ hybridization (FISH) assays checked the rDNA activity, and qRT-PCR assays tested the pre-rRNA levels. Regarding molecular mechanisms, we investigated the role of p53 and miR-101 in modulating nucleolar stress and apoptosis. Finally, the impact of TAF1B knockdown on tumor growth, apoptosis, and p53 expression was observed in xenograft tumors. Result: We identified that TAF1B was highly expressed in hepatocellular carcinoma and associated with poor prognosis in HCC patients. TAF1B depletion modulated nucleolar stress and apoptosis in hepatocellular carcinoma cells through positive and negative feedback from p53-miR-101. RNA polymerase I transcription repression triggered post-transcriptional activation of miR-101 in a p53-dependent manner. In turn, miR-101 negatively feeds back through direct inhibition of the p53-mediated PARP pathway. Conclusion: These findings broaden our comprehension of the function of TAF1B-mediated nucleolar stress in hepatocellular carcinoma and may offer new biomarkers for exploring prospective therapeutic targets in HCC.

Cinobufacini retards progression of pancreatic ductal adenocarcinoma through targeting YEATS2/TAK1/NF-κB axis.

BACKGROUND: Cinobufacini, a sterilized hot water extract of dried toad skin, had significant effect against several human cancers. However, there are few studies reporting the effect of cinobufacini on pancreatic cancer. PURPOSE: To investigate the effects of cinobufacini on the progress of pancreatic ductal adenocarcinoma and the underlying mechanisms. METHODS: Cell counting, EdU incorporation and flow Cytometry were performed to evaluate the effect of cinobufacini on cell cycle and growth. MIA-PaCa2 cells were implanted into the nude mice to determine whether cinobufacini represses PDAC progression in vivo. Luciferase reporter assay, western blotting and qPCR were carried out to measure the activity of NF-κB pathway and the alteration of YEATS2 and TAK1. Ectopic gene expression introduced by plasmids was used to verify the molecular mechanism. RESULTS: Our results showed that cinobufacini induced cell cycle arrest and inhibited the growth of PDAC cell in vitro, and repressed MIA-derived PDAC in vivo. Cinobufacini inhibited the phosphorylation of IKK, IκB and NF-κB p65 in PDAC cells. Furthermore, cinobufacini decreased the abundance of intracellular YEATS2 and total TAK1 protein in a time- and dose dependent manner. Ectopic expression of YEATS2 re-elevated the level of TAK1 and phosphorylated IKKα/ß, IκBα and p65 after cinobufacini treatment in PANC-1 cells. CONCLUSION: Cinobufacini retards the growth and progression of PDAC in vitro and in vivo through YEATS2/TAK1/NF-κB axis.

YEATS2 regulates the activation of TAK1/NF-κB pathway and is critical for pancreatic ductal adenocarcinoma cell survival.

The prognosis of pancreatic ductal adenocarcinoma (PDAC) is poor despite diagnostic progress and new chemotherapeutic regimens. Constitutive activation of NF-κB is frequently observed in PDAC. In this study, we found that YEATS2, a scaffolding protein of ATAC complex, was highly expressed in human PDAC. Depletion of YEATS2 reduced the growth, survival, and tumorigenesis of PDAC cells. The binding of YEATS2 is crucial for maintaining TAK1 activation and NF-κB transcriptional activity. Of importance, our results reveal that YEATS2 promotes NF-κB transcriptional activity through modulating TAK1 abundance and directly interacting with NF-κB as a co-transcriptional factor.

Celastrol inhibits TXNIP expression to protect pancreatic ß cells in diabetic mice.

BACKGROUND: Celastrol (CEL) has a great potential in the treatment of a wide variety of metabolic diseases. However, whether CEL protects pancreatic ß cells and its underlying mechanism are not yet clear. PURPOSE: This study investigates to determine the effects of CEL on the pathogenesis of pancreatic ß cells damage. METHODS: C57BLKS/Leprdb (db/db) mice and rat insulinoma INS-1 cell line or mouse J774A.1 cell line were used as in vivo and in vitro models for investigating the protective effect of CEL on pancreatic ß cells under high glucose environment and the related mechanism. The phenotypic changes were evaluated by immunofluorescence, immunohistochemical staining, flow cytometry and the measurement of biochemical indexes. The molecular mechanism was explored by biological techniques such as western blotting, qPCR, ChIP-qPCR, co-immunoprecipitation and lentivirus infection. RESULTS: Our results showed that CEL at the high dose (CEL-H, 0.2 mg/kg) protects db/db mice against increased body weight and blood glucose. CEL-H inhibits pancreatic ß cell apoptosis in db/db mice and high glucose-induced INS-1 cells. CEL-H also reduced IL-1ß production in islet macrophages. The further study found that CEL suppressed TXNIP expression and NLRP3 inflammasome activation in pancreatic ß cells and islet macrophages. Importantly, the inhibitory effect of CEL on pancreatic ß cell apoptosis and IL-1ß production was also dependent on TXNIP. Mechanically, CEL inhibits Txnip transcription by promoting the degradation of ChREBP. CONCLUSION: Celastrol inhibits TXNIP expression to protect pancreatic ß cells in vivo and in vitro. Our research pointed out another mechanism by which celastrol functions under the condition leptin signaling is ineffective.

Limonin, an AMPK Activator, Inhibits Hepatic Lipid Accumulation in High Fat Diet Fed Mice.

NAFLD is the most prevalent liver disease in human history. The treatment is still limited yet. In the current study, we reported that limonin inhibited hepatic lipid accumulation and fatty acid synthesis in HFD fed mice. Using AMPK inhibitor and AMPK deficient C. elegans, we revealed the effect was dependent on the activation of AMPK. We found that limonin activated AMPK through inhibition of cellular energy metabolism and increasing ADP:ATP ratio. Furthermore, the treatment of limonin induced AMPK mediated suppression of the transcriptional activity of SREBP1/2. Our study suggests that limonin may a promising therapeutic agent for the treatment of NAFLD.

Nobiletin Alleviates Non-alcoholic Steatohepatitis in MCD-Induced Mice by Regulating Macrophage Polarization.

Non-alcoholic steatohepatitis (NASH) is an inflammatory disorder that is characterized by chronic activation of the hepatic inflammatory response and subsequent liver damage. The regulation of macrophage polarization in liver is closely related to the progression of NASH. The orphan nuclear receptor retinoic-acid-related orphan receptor α (RORα) and Krüppel-like factor 4 (KLF4) are key regulators which promote hepatic macrophages toward M2 phenotype and protect against NASH in mice. Nobiletin (NOB), a natural polymethoxylated flavone, is previously reported as a RORα regulator in diet-induced obese mice. However, it is still unclear whether NOB has the protective effect on NASH. In this study, we investigated the role of NOB in NASH using a methionine and choline deficient (MCD)-induced NASH mouse model. Our results showed that NOB ameliorated hepatic damage and fibrosis in MCD fed mice. NOB treatment reduced the infiltration of macrophages and neutrophils in the liver in MCD-fed mice. Of importance, NOB significantly increased the proportion of M2 macrophages and the expression of anti-inflammatory factors in vivo and in vitro. Meanwhile, NOB also decreased the population of M1 macrophages and the expression of proinflammatory cytokines. Mechanistically, NOB elevated KLF4 expression in macrophages. Inhibition of KLF4 abolished NOB regulated macrophage polarization. Furthermore, the regulation of NOB in KLF4 expression was dependent on RORα.