PHLDA1 is a P53 target gene involved in P53-mediated cell apoptosis.

Pleckstrin homeolike domain, family A, member 1 (PHLDA1) is a multifunctional protein that plays diverse roles in A variety of biological processes, including cell death, and hence its altered expression has been found in different types of cancer. Although studies have shown a regulatory relationship between p53 and PHLDA1, the molecular mechanism is still unclear. Especially, the role of PHLDA1 in the process of apoptosis is still controversial. In this study, we found that the expression of PHLDA1 in human cervical cancer cell lines was correlated with the up-expression of p53 after treatment with apoptosis-inducing factors. Subsequently, the binding site and the binding effect of p53 on the promoter region of PHLDA1 were verified by our bioinformatics data analysis and luciferase reporter assay. Indeed, we used CRISPR-Cas9 to knockout the p53 gene in HeLa cells and further confirmed that p53 can bind to the promoter region of PHLDA1 gene, and then directly regulate the expression of PHLDA1 by recruiting P300 and CBP to change the acetylation and methylation levels in the promoter region. Finally, a series of gain-of-function experiments further confirmed that p53 re-expression in HeLap53-/- cell can up-regulate the reduction of PHLDA1 caused by p53 knockout, and affect cell apoptosis and proliferation. Our study is the first to explore the regulatory mechanism of p53 on PHLDA1 by using the p53 gene knockout cell model, which further proves that PHLDA1 is a target-gene in p53-mediated apoptosis, and reveals the important role of PHLDA1 in cell fate determination.

STAT3-Mediated Promoter-Enhancer Interaction Up-Regulates Inhibitor of DNA Binding 1 (ID1) to Promote Colon Cancer Progression.

BACKGROUND: High expression of inhibitor of DNA binding 1 (ID1) correlates with poor prognosis in colorectal cancer (CRC). Aberrant enhancer activation in regulating ID1 transcription is limited. METHODS: Immunohistochemistry (IHC), quantitative RT-PCR (RT-qPCR) and Western blotting (WB) were used to determine the expression of ID1. CRISPR-Cas9 was used to generate ID1 or enhancer E1 knockout cell lines. Dual-luciferase reporter assay, chromosome conformation capture assay and ChIP-qPCR were used to determine the active enhancers of ID1. Cell Counting Kit 8, colony-forming, transwell assays and tumorigenicity in nude mice were used to investigate the biological functions of ID1 and enhancer E1. RESULTS: Human CRC tissues and cell lines expressed a higher level of ID1 than normal controls. ID1 promoted CRC cell proliferation and colony formation. Enhancer E1 actively regulated ID1 promoter activity. Signal transducer and activator of transcription 3 (STAT3) bound to ID1 promoter and enhancer E1 to regulate their activity. The inhibitor of STAT3 Stattic attenuated ID1 promoter and enhancer E1 activity and the expression of ID1. Enhancer E1 knockout down-regulated ID1 expression level and cell proliferation in vitro and in vivo. CONCLUSIONS: Enhancer E1 is positively regulated by STAT3 and contributes to the regulation of ID1 to promote CRC cell progression and might be a potential target for anti-CRC drug studies.

Purine-Induced IFN-γ Promotes Uric Acid Production by Upregulating Xanthine Oxidoreductase Expression.

Objective: Limiting purine intake, inhibiting xanthine oxidoreductase (XOR) and inhibiting urate reabsorption in proximal tubule by uricosuric drugs, to reduce serum uric acid (UA) levels, are recognized treatments for gout. However, the mechanism of increased how XOR expression and activity in hyperuricemia and gout remains unclear. This study aims to explore whether exogenous purines are responsible for increased XOR expression and activity. Methods: HepG2 and Bel-7402 human hepatoma cells were stimulated with exogenous purine, or were exposed to conditioned growth medium of purine-stimulated Jurkat cells, followed by measurement of XOR expression and UA production to determine the effect of lymphocyte-secreted cytokines on XOR expression in hepatocytes. The expression of STAT1, IRF1 and CBP and their binding on the XDH promoter were detected by western blotting and ChIP-qPCR. The level of DNA methylation was determined by bisulfite sequencing PCR. Blood samples from 117 hyperuricemia patients and 119 healthy individuals were collected to analyze the correlation between purine, UA and IFN-γ concentrations. Results: Excess of purine was metabolized to UA in hepatocyte metabolism by XOR that was induced by IFN-γ secreted in the conditioned growth medium of Jurkat cells in response to exogenous purine, but it did not directly induce XOR expression. IFN-γ upregulated XOR expression due to the enhanced binding of STAT1 to IRF1 to further recruit CBP to the XDH promoter. Clinical data showed positive correlation of serum IFN-γ with both purine and UA, and associated risk of hyperuricemia. Conclusion: Purine not only acts as a metabolic substrate of XOR for UA production, but it induces inflammation through IFN-γ secretion that stimulates UA production through elevation of XOR expression.

A 15-Gene Signature and Prognostic Nomogram for Predicting Overall Survival in Non-Distant Metastatic Oral Tongue Squamous Cell Carcinoma.

BACKGROUND: Oral tongue squamous cell carcinoma (OTSCC) is a devastating tumor with poor prognosis. There is an urgent need for reliable biomarkers to help predict prognosis and guide treatment for OTSCC. In the current study, we aimed to develop a robust multi-gene signature and prognostic nomogram to predict the prognosis of patients with non-distant metastatic OTSCC. METHODS: OTSCC-related differentially-expressed genes were screened from The Cancer Genome Atlas (TCGA) database. Univariate Cox regression based on 1,000 bootstrap replicates, LASSO regression and stepwise multivariate Cox regression were utilized to develop a novel multi-mRNA signature for predicting overall survival in OTSCC. The concordance index, area under receiver operating characteristic (ROC AUC) and calibration curve were employed to assess the prediction capacity of the novel multi-gene model. In addition, a prognostic nomogram was constructed to facilitate the clinical use of the fitted model. The Kaplan-Meier with log-rank test was employed to assess differences in overall survival. RESULTS: We successfully established a novel 15-mRNA prognostic model for predicting overall survival of non-distant metastatic OTSCC, involving ADTRP, ITGA3, RFC4, CCDC96, CYP2J2, NELL2, SPHK1, SPAG16, HBEGF, S100A9, EGFL6, ADGRG6, PDE4D, ABCA4, and CTTN. The prediction ability of this 15-gene signature was independent of other clinicopathological factors, with an HR of 11.5 (95% CI: 4.70-28.3). Moreover, internal validation by bootstrap analysis yielded a C-index of 0.849, with a 3-year AUC of 0.907 and 5-year AUC of 0.944, which implied excellent prediction accuracy of the fitted model. In addition, external validation by using the GEO dataset (GSE41116) yielded a C-index of 0.804, with a 3-year AUC of 0.868 and 5-year AUC of 0.855, which also indicated good prediction ability of the 15-gene model. Finally, a prognostic nomogram integrating risk group, grade, T stage and N stage was established. CONCLUSION: Our results demonstrate our 15-gene signature was independently associated with overall survival in non-distant metastatic OTSCC. Moreover, the prognostic nomogram integrating the 15-gene signature and clinicopathological factors has potential to be developed as a prognostic tool.

Berberine inhibits cancer cells growth by suppressing fatty acid synthesis and biogenesis of extracellular vesicles.

AIMS: Berberine is an isoquinoline alkaloid extracted from the root, rhizome and stem bark of Coptidis Rhizoma. Previous studies have revealed the anti-tumor potential of berberine against various types of cancer cells. However, the underlying mechanisms are not yet fully understood. In this study, we focused on the effects of berberine on fatty acid synthesis and extracellular vesicles formation in cancer cells, and revealed the internal mechanism of berberine inhibition on cancer cell proliferation. MATERIALS AND METHODS: Anti-proliferative activity of berberine was determined by cell counting and microscope observation and cell cycle analysis. Activities of AMPK and ACC, expression of extracellular vesicles markers were detected by western blotting. 13C labeling metabolic flux analysis was used for determination of de novo synthesis of fatty acids. The excreted extracellular vesicles in culture mediums were separated by both polyethylene glycol enrichment of extracellular vesicles and differential centrifugation separation. KEY FINDINGS: Among our early experiments, 5-10 µmol/L berberine exhibited the substantial anti-proliferative effect against human colon cancer cell line HCT116, cervical cancer cell line HeLa and other cancer cells. It was also revealed that, through activating AMPK, berberine inhibited ACC activity then suppressed intracellular fatty acid synthesis, finally decreased the biogenesis of extracellular vesicles. Moreover, supplement with citrate acid, palmitic acid, as well as exogenous extracellular vesicles, could rescue the inhibitory effect of berberine on cell proliferation, suggesting that inhibited ACC activity, suppressed fatty acid synthesis and decreased extracellular vesicles production were important mechanisms account for berberine inhibiting cancer cell proliferation. SIGNIFICANCE: Our study indicates that berberine suppresses cancer cell proliferation through inhibiting the synthesis of fatty acids and decreasing biogenesis and secretion of extracellular vesicles, suggests that berberine is a promising candidate for the development of new therapies for cancer.

Androgen Receptor-Activated Enhancers Simultaneously Regulate Oncogene TMPRSS2 and lncRNA PRCAT38 in Prostate Cancer.

Prostate cancer is a common carcinoma in males, the development of which involves the androgen receptor (AR) as a key regulator. AR transactivation induces the high expression of androgen-regulated genes, including transmembrane protease serine 2 (TMPRSS2) and long noncoding RNA prostate cancer-associated transcript 38 (PRCAT38). PRCAT38 and TMPRSS2 are both located on chromosome 21, separated by a series of enhancers. PRCAT38 is a prostate-specific long noncoding RNA that is highly expressed in cancer tissue as compared to normal tissue. Here, we show chromatin looping by enhancers E1 and E2 with the promoters for PRCAT38 and TMPRSS2, indicating the co-regulation of PRCAT38 and TMPRSS2 by the same enhancers. The knockout of enhancer E1 or E2 simultaneously impaired the transcription of PRCAT38 and TMPRSS2 and inhibited cell growth and migration. Moreover, the loop formation and enhancer activity were mediated by AR/FOXA1 binding and the activity of acetyltransferase p300. Our findings demonstrate the utilization of shared enhancers in the joint regulation of two oncogenes in prostate cancer cells.

Aberrant activation of CYR61 enhancers in colorectal cancer development.

BACKGROUND: High expression of secreted matricellular protein cysteine-rich 61 (CYR61) correlates with poor prognosis in colorectal cancer (CRC). Aberrant enhancer activation has been shown to correlate with expression of key genes involved in cancer progression. However, such mechanisms in CYR61 transcription regulation remain unexplored. METHODS: Expression of CYR61 was determined by immunohistochemistry (IHC), quantitative real-time PCR (qRT-PCR) and western blotting (WB) in CRC patients paraffin specimens and colon cell lines. ChIP-seq data of enhancer-characteristic histone modifications, in CRC tissues from the Gene Expression Omnibus (GEO) database, were reanalyzed to search for putative enhancers of CYR61. Dual-luciferase reporter assay was used to detected enhancer activity. Physical interactions between putative enhancers and CYR61 promoter were detected by chromosome conformation capture (3C) assay. Histone modification and transcription factors (TFs) enrichment were detected by ChIP-qPCR. Additionally, biological function of enhancers was investigated by transwell migration assays. RESULTS: CRC tissues and cell lines expressed higher level of CYR61 than normal colon mucosa. Three putative enhancers located downstream of CYR61 were found in CRC tissues by ChIP-seq data reanalysis. Consistent with the ChIP-seq analysis results in the GEO database, the normal colon mucosal epithelial cell line NCM460 possessed no active CYR61 enhancers, whereas colon cancer cells exhibited different patterns of active CYR61 enhancers. HCT116 cells had an active Enhancer3, whereas RKO cells had both Enhancer1 and Enhancer3 active. Pioneer factor FOXA1 promoted CYR61 expression by recruiting CBP histone acetyltransferase binding and increasing promoter-enhancer looping frequencies and enhancer activity. CBP knockdown attenuated H3K27ac enrichment, promoter-enhancer looping frequencies, and enhancer activity. Small molecule compound 12-O-tetradecanoyl phorbol-13-acetate (TPA) treatment, which stimulated CYR61 expression, and verteporfin (VP) treatment, which inhibited CYR61 expression, confirmed that the enhancers regulated CYR61 expression. Knockdown and ectopic expression of CYR61 rescued cell migration changes induced by over-expressing and knockdown of FOXA1, respectively. CONCLUSIONS: CYR61 enhancer activation, mediated by FOXA1 and CBP, occurs during CRC progression to up-regulate CYR61 expression and promote cell migration in CRC, suggesting inhibition of recruitment of FOXA1 and/or CBP to CYR61 enhancers may have therapeutic implications.