Inhibition Of P53 Expression Research Articles

LncRNA LINC00673 inhibits p53 expression by interacting with EZH2 and DNMT1 in papillary thyroid carcinoma.

This study aims to elucidate the regulatory role of long noncoding RNA (lncRNA) LINC00673 in proliferative, invasive and metastatic capacities of papillary thyroid carcinoma (PTC), and to investigate the possible underlying mechanism. LINC00673 expression in PTC tissues and cell lines was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between LINC00673 expression and PTC prognosis was analyzed. By plasmid transfection, we constructed PTC cell lines with stable knockdown of LINC00673. The regulatory effect of LINC00673 on the proliferation of K1 and TPC-1 cells were determined by Cell Counting Kit-8 (CCK-8) assay and colony formation assay. The transwell assay was conducted to evaluate the effect of LINC00673 on the metastatic ability of PTC cells. The binding condition between LINC00673 with enhancer of zeste homolog 2 (EZH2) and DNA Methyltransferase 1 (DNMT1) was verified by RNA immunoprecipitation (RIP), chromatin immunoprecipitation (ChIP) and Western blot. The cellular mechanism of p53 in regulating biological behaviors of PTC cells was explored by Western blot. Finally, the gain-of-function experiment was performed to elucidate whether LINC00673 could regulate PTC development by inhibiting p53 expression. LINC00673 expression in PTC tissues was significantly higher than that of the adjacent normal tissues. Besides, higher expression of LINC00673 indicated worse prognosis of PTC. The knockdown of LINC00673 in K1 and TPC-1 cells markedly reduced the proliferative rate. Meanwhile, LINC00673 down-regulation remarkably inhibited the migratory and invasive capacities of K1 and TPC-1 cells. RIP and ChIP assay demonstrated that LINC00673 could bind to EZH2 and DNMT1. Besides, Western blot analysis showed that LINC00673 negatively regulated p53 expression. In addition, the knockdown of p53 in K1 and TPC-1 cells partially reversed the inhibitory effect of LINC00673 deficiency on the proliferation and metastasis of PTC cells. High expression of LINC00673 in PTC predicts a poor prognosis. LINC00673 remarkably promotes the proliferation and invasion of PTC cells by inhibiting p53 expression by binding to EZH2 and DNMT1.

Role of smooth muscle cell p53 in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterized by remodeling and narrowing of the pulmonary arteries, which lead to elevation of right ventricular pressure, heart failure, and death. Proliferation of pulmonary artery smooth muscle cells (PASMCs) is thought to be central to the pathogenesis of PAH, although the underlying mechanisms are still being explored. The protein p53 is involved in cell cycle coordination, DNA repair, apoptosis, and cellular senescence, but its role in pulmonary hypertension (PH) is not fully known. We developed a mouse model of hypoxia-induced pulmonary hypertension (PH) and found significant reduction of p53 expression in the lungs. Our in vitro experiments with metabolomic analyses and the Seahorse XF extracellular flux analyzer indicated that suppression of p53 expression in PASMCs led to upregulation of glycolysis and downregulation of mitochondrial respiration, suggesting a proliferative phenotype resembling that of cancer cells. It was previously shown that systemic genetic depletion of p53 in a murine PH model led to more severe lung manifestations. Lack of information about the role of cell-specific p53 signaling promoted us to investigate it in our mouse PH model with the inducible Cre-loxP system. We generated a mouse model with SMC-specific gain or loss of p53 function by crossing Myh11-Cre/ERT2 mice with floxed Mdm4 mice or floxed Trp53 mice. After these animals were exposed to hypoxia for 4 weeks, we conducted hemodynamic and echocardiographic studies. Surprisingly, the severity of PH was similar in both groups of mice and there were no differences between the genotypes. Our findings in these mice indicate that activation or suppression of p53 signaling in SMCs has a minor role in the pathogenesis of PH and suggest that p53 signaling in other cells (endothelial cells, immune cells, or fibroblasts) may be involved in the progression of this condition.

HOX transcript antisense RNA is elevated in gastric carcinogenesis and regulated by the NF-κB pathway.

The expression pattern of HOX transcript antisense RNA (HOTAIR) in the progression of gastric cancer and the regulation of its expression are still unclear. In the current study, HOTAIR expressions in gastric tissues collected from patients with superficial gastritis, atrophic gastritis, atypical hyperplasia, and gastric cancer as well as normal controls was quantitatively examined. The results showed that the expression of HOTAIR was higher in gastric cancer than in normal tissues, but reached the highest level in atrophic gastritis, suggesting that HOTAIR may be involved in the molecular process of nonresolving inflammation. Then tumor necrosis factor-α-induced protein-8 like-2 (TIPE2), a known gene associated with nonresolving inflammation, was overexpressed and the results showed that the promotion in TIPE2 expression triggered HOTAIR reduction, this result was further verified by microarray analysis and TIPE2 knockout mice. Subsequently, the data obtained from HOTAIR knockdown experiment showed that it significantly enhanced colony forming capability and inhibited p27 expression in AGS cells. Furthermore, deletion constructs and luciferase-based activity assays indicated that the -475 to -443bp region of HOTAIR promoter contained a crucial regulatory element. Transcription factor prediction with software TRANSFAC revealed that nuclear factor-κB signaling protein p65 had a binding site in this region and might have roles in HOTAIR expression. The binding of phosphor-p65 to HOTAIR promoter was verified by chromatin immunoprecipitation, and succeeding experiment results demonstrated that p65 reduction by p65 small interfering RNA and TIPE2 overexpression also decreased HOTAIR expression. Conclusively, our results suggest that HOTAIR was associated with nonresolving inflammation, and its expression is regulated by p65.

Proteinase-activated receptor-2 enhances Bcl2-like protein-12 expression in lung cancer cells to suppress p53 expression.

IntroductionThe pathogenesis of lung cancer is unclear. Less expression of p53 or p53 mutation was identified in lung cancer cells, which plays a role in the development of lung cancer. Recent reports indicate that Bcl2-like protein-12 (Bcl2L12) can inhibit the expression of p53. Lung cancer cells express proteinase-activated receptor-2 (PAR2). This study tests the hypothesis that activation of PAR2 inhibits the expression of p53 in lung cancer cells.Material and methodsLung cancer cells were collected from patients with non-small cell lung cancer (NSCLC). The cells were exposed to active peptides or trypsin in the culture for 48 h. The expression of p53 was assessed by RT-qPCR and Western blotting.ResultsWe observed that lung cancer cells express Bcl2L12. Activation of PAR2 increases expression of Bcl2L12 in lung cancer cells. Bcl2L12 mediates PAR2-suppressed p53 expression in lung cancer cells. IgE-activated mast cell suppression of p53 expression in lung cancer cells can be prevented by knocking down Bcl2L12. The Bcl2L12 bound Mdm2, the transcription factor of p53, to prevent the Mdm2 from binding to the promoter of p53 and thus inhibited p53 expression in lung cancer cells. PAR2 could attenuate lung cancer cell apoptosis via inducing Bcl2L12.ConclusionsLung cancer cells express Bcl2L12, which mediates the effects of activation of PAR2 on suppressing the expression of p53 in lung cancer cells, implying that Bcl2L12 may be a novel therapeutic target for the treatment of lung cancer.

Activating Mas receptor protects human pulmonary microvascular endothelial cells against LPS-induced apoptosis via the NF-kB p65/P53 feedback pathways.

The balance between Ang II/AT1R and Ang-(1-7)/Mas plays a pivotal role in the development of lipopolysaccharides (LPS)-induced acute respiratory distress syndrome. However, the mechanisms underlying the balancing process still remain unclear. Here we investigated the roles of nuclear factor (NF)-κB and p53 in regulating AT1R and Mas expression. The results demonstrated that Ang II pretreatment resulted in downregulation of Mas and upregulation of AT1R, phosphorylated p65, and apoptosis in LPS-treated Human pulmonary microvascular endothelial cells (HPMVECs), but had no effect on p53 expression. Lentiviral vector-mediated P65 knockdown, but not a P53 knockdown, reversed all these effects of Ang II. On the other hand, Ang-(1-7) pretreatment lead to an increased in Mas expression and a decrease in AT1R, p53, and phosphorylated p65 expressions with suppressed apoptosis in LPS-treated cells. P65 knockdown promoted the protein expression of both AT1R and Mas while inhibiting p53 expression. P53 knockdown, but not a p65 knockdown, reversed all these effects of Ang-(1-7). Interestingly, p65 overexpression upregulated p53 and AT1R but downregulated Mas. P53 knockdown activated p65. These results suggest that there is a two-way feedback regulation between AT1R and Mas receptor via the NF-kB p65/P53 pathway, which may play a key role in LPS-induced HPMVECs apoptosis.

Long non-coding RNA DANCR promotes the progression of non-small-cell lung cancer by inhibiting p21 expression.

BackgroundLong non-coding RNAs (lncRNAs) play important roles in human cancers. However, the functional roles of lncRNAs in non-small-cell lung cancer (NSCLC) and the underlying mechanisms are not well understood.MethodsWe examined the expression of lncRNA DANCR in NSCLC by qRT-PCR and explored its biological roles in NSCLC progression by cell and molecular biology studies.ResultsDANCR expression level was increased in human NSCLC. The knockdown of DANCR inhibited NSCLC cell proliferation by inducing cell apoptosis and cell cycle arrest. In addition, DANCR knockdown suppressed NSCLC cell migration and invasion via inhibition of epithelial–mesenchymal transition (EMT). On the contrary, DANCR overexpression had the opposite effects. DANCR knockdown inhibited EZH-2-mediated epigenetic silencing of p21 promoter and increased p21 expression. Moreover, DANCR knockdown inhibited NSCLC cell proliferation, migration, and invasion in a p21-dependent manner.ConclusionDANCR plays oncogenic roles in NSCLC and may provide a novel biomarker for NSCLC diagnosis and prognosis.

TRIB2 functions as novel oncogene in colorectal cancer by blocking cellular senescence through AP4/p21 signaling

BackgroundCellular senescence is a state of irreversible cell growth arrest and senescence cells permanently lose proliferation potential. Induction of cellular senescence might be a novel therapy for cancer cells. TRIB2 has been reported to participate in regulating proliferation and drug resistance of various cancer cells. However, the role of TRIB2 in cellular senescence of colorectal cancer (CRC) and its molecular mechanism remains unclear.MethodsThe expression of TRIB2 in colorectal cancer tissues and adjacent tissues was detected by immunohistochemistry and RT-PCR. The growth, cell cycle distribution and cellular senescence of colorectal cancer cells were evaluated by Cell Counting Kit-8 (CCK8) assay, flow cytometry detection and senescence-associated β-galactosidase staining, respectively. Western blot, RT-PCR and luciferase assay were performed to determine how TRIB2 regulates p21. Immunoprecipitation (IP) and chromatin-immunoprecipitation (ChIP) were used to investigate the molecular mechanisms.ResultsWe found that TRIB2 expression was elevated in CRC tissues compared to normal adjacent tissues and high TRIB2 expression indicated poor prognosis of CRC patients. Functionally, depletion of TRIB2 inhibited cancer cells proliferation, induced cell cycle arrest and promoted cellular senescence, whereas overexpression of TRIB2 accelerated cell growth, cell cycle progression and blocked cellular senescence. Further studies showed that TRIB2 physically interacted with AP4 and inhibited p21 expression through enhancing transcription activities of AP4. The rescue experiments indicated that silencing of AP4 abrogated the inhibition of cellular senescence induced by TRIB2 overexpression.ConclusionThese data demonstrate that TRIB2 suppresses cellular senescence through interaction with AP4 to down-regulate p21 expression. Therefore, TRIB2 could be a potential target for CRC treatment.

Epstein-Barr Virus MicroRNA miR-BART5-3p Inhibits p53 Expression

Epstein-Barr virus (EBV) is the first human virus found to encode many microRNAs. It is etiologically linked to nasopharyngeal carcinoma and EBV-associated gastric carcinoma. During the latent infection period, there are only a few EBV proteins expressed, whereas EBV microRNAs, such as the BamHI-A region rightward transcript (BART) microRNAs, are highly expressed. However, how these BART miRNAs precisely regulate the tumor growth in nasopharyngeal carcinoma and gastric carcinoma remains obscure. Here, we report that upregulation of EBV-miR-BART5-3p promotes the growth of nasopharyngeal carcinoma and gastric carcinoma cells. BART5-3p directly targets the tumor suppressor gene TP53 on its 3'-untranslated region (3'-UTR) and consequently downregulates CDKN1A, BAX, and FAS expression, leading to acceleration of the cell cycle progress and inhibition of cell apoptosis. BART5-3p contributes to the resistance to chemotherapeutic drugs and ionizing irradiation-induced p53 increase. Moreover, BART5-3p also facilitates degradation of p53 proteins. BART5-3p is the first EBV-microRNA to be identified as inhibiting p53 expression and function, which suggests a novel mechanism underlying the strategies employed by EBV to maintain latent infection and promote the development of EBV-associated carcinomas.IMPORTANCE EBV encodes 44 mature microRNAs, which have been proven to promote EBV-associated diseases by targeting host genes and self-viral genes. In EBV-associated carcinomas, the expression of viral protein is limited but the expression of BART microRNAs is extremely high, suggesting that they could be major factors in the contribution of EBV-associated tumorigenesis. p53 is a critical tumor suppressor. Unlike in most human solid tumors, TP53 mutations are rare in nasopharyngeal carcinoma and EBV-associated gastric carcinoma tissues, suggesting a possibility that some EBV-encoded products suppress the functions of p53. This study provides the first evidence that a BART microRNA can suppress p53 expression by directly targeting its 3'-UTR. This study implies that EBV can use its BART microRNAs to modulate the expression of p53, thus maintaining its latency and contributing to tumorigenesis.

LncRNA HOXB-AS3 promotes hepatoma by inhibiting p53 expression.

We investigate the mechanism of HOXB-AS3 in promoting the development of hepatocellular carcinoma. The expression of HOXB-AS3 in tumor tissues and adjacent tissues of hepatocellular carcinoma was detected by quantitative real time-polymerase chain reaction (qRT-PCR), and the relationship between the expression of HOXB-AS3 and tumor tissues was analyzed. The effects of HOXB-AS3 and p53 on cell proliferation, cell cycle and apoptosis were detected by plate cloning experiment and flow cytometry. The binding relationship between HOXB-AS3 and DNMT1 and the regulation mechanism of DNMT1 on p53 were tested by RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) experiments, respectively. Western blot was used to detect the expression of p53 after knockdown of HOXB-AS3. The torsion experiment was performed to assess whether HOXB-AS3 regulated the proliferation and apoptosis of hepatoma cells by inhibiting p53 expression. The results of qRT-PCR showed that the expression of HOXB-AS3 was significantly higher in cancerous tissues of patients with hepatocellular carcinoma than in adjacent tissues. The expression of HOXB-AS3 in patients in stage III and IV was significantly higher than that in stage I and II. Inhibition of HOXB-AS3 expression in liver cancer cells including Hep3B and LM3 could promote cell proliferation, inhibit cell apoptosis and induce cell cycle arrest in the G0/G1 phase. The results of RIP and ChIP experiments showed that HOXB-AS3 inhibited the expression of p53 by binding to DNMT1, and overexpression of p53 in Hep3B cells could partially reverse the changes in cell proliferation and apoptosis induced by HOXB-AS3. Highly expressed HOXB-AS3 was confirmed to promote the proliferation of hepatocellular carcinoma cells and inhibit apoptosis, and the mechanism was related to the regulation role of HOXB-AS3 in p53 expression by binding to DNMT1.

Syringa pinnatifolia Hemsl. fraction protects against myocardial ischemic injury by targeting the p53-mediated apoptosis pathway

BackgroundPeeled stems of Syringa pinnatifolia Hemsl. (SP) have been widely used to treat extra “He-Yi” induced myocardial ischemia for hundreds of years in Inner Mongolia, China and previous result showed that intragastric pretreatment with total extract (T) of SP has a protective effect against myocardial infarction (MI). HypothesisThis study aims to describe the pharmacological investigation and chemical characterization of the major (M) and minor (N) fractions obtained from T through column chromatography fractionation on macroporous resin and to explore whether the regulatory effects were linked to the p53-mediated apoptosis pathways. Study designLeft anterior descending (LAD) coronary artery-ligated mice and H9c2 cells cultured in serum-free medium under hypoxic conditions were treated with T, M, and N. MethodsEchocardiography was performed and biomarkers in serum were determined in mice, and pathological changes were observed through histopathology assay. Immunofluorescence staining and qRT-PCR were used to detect the expression levels of p53 in heart tissue. Flow cytometry was used to measure the level of apoptosis and caspase-3 activity in H9c2 cells. Western blot analysis was conducted to detect p53 and p53-mediated proteins apoptosis pathways of in both tissue and H9c2 cells. ResultsBoth T and M have an equivalent cardioprotective effect whereas N is non-active. M decreased MI-induced myocardial compensatory expansion by decrease of left ventricular end-systolic diameter (LVESd) and left ventricular end-diastolic diameter (LVEDd) and prevented decreases in ejection fraction (EF) and fractional shortening (FS). The MI-induced increased levels of creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and hypersensitive C-reactive protein (hs-CRP) were decreased and the expanded infarction size was reduced. M could also improve cell viability and inhibit apoptosis in H9c2 cells under hypoxic conditions. Immunofluorescence and qRT-PCR assay showed that M suppressed p53 expression in the myocardium. Western blot analysis showed that M could prevent MI-induced activation of p53-mediated apoptosis pathway in both myocardium and H9c2 cells. ConclusionThe results demonstrated that M may protect against myocardial ischemia by improving cardiac function and inhibiting cardiomyocytes apoptosis. Overall, the present findings supported the clinical application of SP and enriched the research of anti-myocardial ischemia drug from traditional medicines.

MicroRNA-1254 exertsoncogenic effects by directly targeting RASSF9 in human breast cancer.

MicroRNAs (miRNAs or miRs) play crucial roles in human breast cancer. Although miR-1254 has been shown to have oncogenic activity in several cancer types, its biological function in breast cancer and its mechanisms of action remain unclear. In this study, we investigated the role of miR-1254 in human breast cancer and sought to elucidate the relevant underlying mechanisms. We found that miR-1254 expression was markedly increased in breast cancer tissues and cell lines. Additionally, miR-1254 overexpression accelerated breast cancer cell proliferation, cell cycle G1-S phase transition and inhibited apoptosis. Nevertheless, the inhibition of miR-1254 suppressed cell proliferation and induced apoptosis. Further analyses revealed that miR-1254 expression negatively correlated with RASSF9 expression in breast cancer tissues. We verified that RASSF9 was a direct target of miR-1254 using a luciferase reporter assay. The overexpression of miR-1254 reduced the RASSF9 mRNA and protein levels, and the suppression of miR-1254 promoted RASSF9 expression. Notably, the knockdown or overexpression of RASSF9 corroborated the biological effects observed upon miR-1254 overexpression or inhibition. Taken together, these results demonstrate that miR-1254 accelerates breast cancer cell growth by activating the AKT signaling pathway and suppresses apoptosis by inhibiting p53 expression through the targeting of RASSF9. The data indicate that miR-1254 plays a crucial role in human breast cancer, and may represent a novel therapeutic target for this malignancy.

Hexavalent chromium induces oxidative stress and mitochondria-mediated apoptosis in isolated skin fibroblasts of Indo-Pacific humpback dolphin

The increasing gas emissions and industrial wastewater discharge of anthropogenic hexavalent chromium (Cr(VI)) have been growing health concerns to the high trophic level marine mammals. Our previous studies showed that Indo-Pacific humpback dolphin (Sousa chinensis), stranded on the Pearl River Estuary region, contained exceedingly high levels of Cr in their skin-tissues. Unfortunately, the molecular toxic mechanisms on this mammal are absent, limiting our understanding of the eco-physiological impacts of Cr(VI) on dolphins. Thus, the cytotoxicity effects of Cr(VI) were analyzed on fibroblasts we isolated from the skin of S. chinensis (ScSF). This study showed that Cr(VI) markedly inhibited the viability of ScSF cells via induction of apoptosis accompanied by an increase in the production of reactive oxygen species and the population of G2/M arrest or apoptotic sub-G1 phase cells, up-regulation of p53, and activation of caspase-3. Further investigation on intracellular mechanisms indicated that Cr(VI) induced depletion of mitochondrial membrane potential in cells through regulating the expression of anti-apoptotic (Bcl-2) and pro-apoptotic (Bax) proteins, resulting in decrease of the ATP level, cytochrome c release from mitochondria into cytosol, and the activation of caspase-9. Furthermore, antioxidants N-acetylcysteine and vitamin C displayed chemoprotective activity against Cr(VI) via suppression of p53 expression, indicating that the Cr(VI)-induced cell death may be mediated by oxidative stress. Overall, these results provide insights into the potential mechanisms underlying the cytotoxicity of Cr(VI) in Indo-Pacific humpback dolphin skin cells, offer experimental support for the proposed protective role of antioxidants in Cr(VI)-induced toxicity, and suggest that Cr(VI) contamination is one of key health concern issues for the protection of Indo-Pacific humpback dolphin.

Down-regulation of LHPP in cervical cancer influences cell proliferation, metastasis and apoptosis by modulating AKT

Cervical cancer is a leading severe malignancy throughout the world. Though various pathologies associated with cervical cancer progression have been demonstrated, further study is still necessary to reveal the tumorigenesis of cervical cancer. The protein histidine phosphatase LHPP is reported as a tumor suppressor. Histidine phosphorylation, also known as hidden phosphoproteome, is a poorly characterized post-translational modification of proteins. LHPP is evolutionarily conserved from worm to human. In the present study, we discovered that LHPP expression levels were lower in human cervical cancer tumors than that in adjacent normal tissue samples. LHPP expression levels were also reduced in several cervical cancer cell lines. Further, LHPP over-expression reduced the cell proliferation, migration and invasion, associated with the change of p53 and metastasis signaling pathways. Moreover, over-expressing LHPP markedly induced apoptosis in human cervical cancer cells via promoting the cleaved Caspse-3 and PARP. Importantly, we found that LHPP over-expression blocked AKT activation. Elevating AKT activity could abolish the role of LHPP over-expression in reducing cell proliferation and metastasis, as well as in inducing apoptotic response. Moreover, suppressing p53 expression with its inhibitor of PFTα abrogated the activity of LHPP to impede cell proliferation and metastasis, and to trigger apoptosis. AKT phosphorylation also restrained p53 expression levels in cervical cancer cells. In vivo, the anti-cervical cancer effects of LJPP were verified, which were also via the repression of cell proliferation and metastasis, and the induction of apoptosis. Therefore, LHPP could be considered as an effective candidate to develop effective therapeutic strategy against cervical cancer development.

Iron overloaded polarizes macrophage to proinflammation phenotype through ROS/acetyl-p53 pathway.

PurposeMacrophages play critical roles in inflammation and wound healing and can be divided into two subtypes: classically activated (M1) and alternatively activated (M2) macrophages. Macrophages also play important roles in regulating iron homeostasis, and intracellular iron accumulation induces M1‐type macrophage polarization which provides a potential approach to tumor immunotherapy through M2 tumor‐associated macrophage repolarization. However, the mechanisms underlying iron‐induced M1 polarization remain unclear.MethodsWestern blotting, qRT‐PCR, and flow cytometry were used to detect the polarization indexes in RAW 264.7 murine macrophages treated with iron, and Western bloting and qRT‐PCR were used to detect p21 expression. The compound 2,7‐dichlorofluorescein diacetate was used to measure reactive oxygen species (ROS) levels in macrophages after iron or N‐acetyl‐l‐cysteine (NAC) treatment. The p300/CREB‐binding protein (CBP) inhibitor C646 was used to inhibit p53 acetylation, and Western bloting, qRT‐PCR, and immunofluorescence were used to detect p53 expression and acetylation. BALB/c mice were subcutaneously injected with H22 hepatoma cells, and macrophage polarization status was investigated after tail intravenous injection of iron. Immunohistochemical staining was used to evaluate the protein expression of cluster of differentiation 86 (CD86) and EGF‐like module‐containing mucin‐like hormone receptor‐like 1 (F4/80) in the subcutaneous tumors.ResultsIron overload induced M1 polarization by increasing ROS production and inducing p53 acetylation in RAW cells, and reduction in ROS levels by NAC repressed M1 polarization and p53 acetylation. Inhibition of acetyl‐p53 by a p300/CBP inhibitor prevented M1 polarization and inhibited p21 expression. These results showed that high ROS levels induced by iron overload polarized macrophages to the M1 subtype by enhancing p300/CBP acetyltransferase activity and promoting p53 acetylation.

Mitochondrial dysfunction suppresses p53 expression via calcium-mediated nuclear factor-kB signaling in HCT116 human colorectal carcinoma cells.

Mitochondrial DNA (mtDNA) mutations are often observed in various cancer types. Although the correlation between mitochondrial dysfunction and cancer malignancy has been demonstrated by several studies, further research is required to elucidate the molecular mechanisms underlying accelerated tumor development and progression due to mitochondrial mutations. We generated an mtDNA-depleted cell line, ρ0, via long-term ethidium bromide treatment to define the molecular mechanisms of tumor malignancy induced by mitochondrial dysfunction. Mitochondrial dysfunction in ρ0 cells reduced drug-induced cell death and decreased the expression of pro-apoptotic proteins including p53. The p53 expression was reduced by activation of nuclear factor-κB that depended on elevated levels of free calcium in HCT116/ρ0 cells. Overall, these data provide a novel mechanism for tumor development and drug resistance due to mitochondrial dysfunction.

IDH1 Arg-132 mutant promotes tumor formation through down-regulating p53

Resistance to apoptosis and uncontrolled proliferation are two hallmarks of cancer cells. p53 is crucial for apoptosis triggered by a broad range of stresses and a well-known gatekeeper for neoplastic transformation. Here we show that oncogenic IDH1 R132H/R132Q mutants robustly inhibit p53 expression and such an effect is attributed to 2-HG production. Mechanistically, 2-hydroxyglutarate (2-HG) stabilizes hypoxia-inducible factor-2α, which in turn activates the expression of miR-380-5p, a characterized microRNA against p53 expression. Rescue expression of p53 can inhibit the proliferation rate and impair the resistance of apoptosis induced by doxorubicin in IDH1 R132Q mouse embryonic fibroblast cells. Furthermore, p53 protein levels correlates negatively with IDH1 R132H levels in human glioma samples. Our results thus shed a new light on how p53 is down-regulated by 2-HG and suggests that impairment of p53-mediated apoptosis contributes to the tumorigenesis driven by IDH1 mutants.

Increased interleukin-17A levels promote rituximab resistance by suppressing p53 expression and predict an unfavorable prognosis in patients with diffuse large B cell lymphoma.

Rituximab resistance has become increasingly common in patients with diffuse large B cell lymphoma (DLBCL). However, the mechanisms involved remain unclear. In this study, we aimed to examine the effect of rituximab on interleukin (IL)-17A and to investigate the role of IL-17A in rituximab resistance and its prognostic value in patients with DLBCL. Our retrospective analysis revealed that rituximab increased IL-6 expression levels in patients with DLBCL, and the increased IL-6 levels in turn induced the differentiation of Th17 and IL-17+Foxp3+ Treg cells, which secreted IL-17A both in vivo and in vitro. We then examined the effects of IL-17A on the apoptosis and proliferation of, and p53 expression in DLBCL cells, and found that IL-17A prevented rituximab-induced apoptosis and promoted the proliferation of DLBCL cells by suppressing p53 expression in vitro. The survival data of 73 patients with DLBCL suggested that high peripheral blood levels of IL-17A predicted an unfavorable survival. On the whole, our data indicate that rituximab promotes Th17 and IL-17+Foxp3+ Treg cells to secrete IL-17A, which in turn promotes rituximab resistance, partially by suppressing p53 expression and inhibiting rituximab-induced DLBCL cell apoptosis. IL-17A may thus prove to be a useful prognostic marker in patients with DLBCL.

Effects of electroacupuncture on luteal regression and steroidogenesis in ovarian hyperstimulation syndrome model rat

AimsElectroacupuncture (EA) is an effective and safe therapeutic method widely used for treating clinical diseases. Previously, we found that EA could decrease serum hormones and reduce ovarian size in ovarian hyperstimulation syndrome (OHSS) rat model. Nevertheless, the mechanisms that contribute to these improvements remain unclear. Materials and methodsHE staining was used to count the number of corpora lutea (CL) and follicles. Immunohistochemical and ELISA were applied to examine luteal functional and structural regression. Immunoprecipitation was used for analyzing the interaction between NPY (neuropeptide Y) and COX-2; western blotting and qRT-PCR were used to evaluate the expressions of steroidogenic enzymes and PKA/CREB pathway. Key findingsEA treatment significantly reduced the ovarian weight and the number of CL, also decreased ovarian and serum levels of PGE2 and COX-2 expression; increased ovarian PGF2α levels and PGF2α/PGE2 ratio; decreased PCNA expression and distribution; and increased cyclin regulatory inhibitor p27 expression to have further effect on the luteal formation, and promote luteal functional and structural regression. Moreover, expression of COX-2 in ovaries was possessed interactivity increased expression of NPY. Furthermore, EA treatment lowered the serum hormone levels, inhibited PKA/CREB pathway and decreased the expressions of steroidogenic enzymes. Hence, interaction with COX-2, NPY may affect the levels of PGF2α and PGE2 as well as impact the proliferation of granulosa cells in ovaries, thus further reducing the luteal formation, and promoting luteal structural and functional regression, as well as the ovarian steroidogenesis following EA treatment. SignificanceEA treatment could be an option for preventing OHSS in ART.

Reciprocity of Action of Increasing Oct4 and Repressing p53 in Transdifferentiation of Mouse Embryonic Fibroblasts into Cardiac Myocytes.

p53 is a barrier to somatic cell reprogramming. Deletion or transient suppression of p53 increases the efficiency of reprogramming of somatic cells into induced pluripotent stem cells. Whether p53 represents an obstacle to a similar process transdifferentiation of somatic cells is unknown. However, it is predicted that inhibition of p53 would promote transdifferentiation of fibroblasts into cardiomyocytes. In this study, the effect of p53 on the capacity of cardiogenic transdifferentiation is evaluated using p53 wild-type (p53+/+), p53 heterozygous mutant (p53+/-), and p53 homozygous mutant (p53-/-) mouse embryonic fibroblasts (MEFs). Repression of p53 in MEFs increases the expression level of mesoderm transcription factors Brachyury (T) and MESP1. The cardiac-specific markers, Myh6 (Myosin, Heavy Chain 6), Myh7 (Myosin, Heavy Chain 7), and cTnI (cardiac muscle troponin I), show elevated expression in p53+/- and p53-/- MEFs compared with wild-type MEFs, but cardiac muscle troponin T (cTnT) showed a lower expression level when p53 was inhibited. After induction to cardiac differentiation, cTnT expression increased and markers of endoderm and ectoderm decreased in p53+/- and p53-/- MEFs. The effect of an important reprogramming factor Oct4 on cardiac transdifferentiation was also evaluated in the allelic series of p53 MEFs. We found that overexpression of Oct4 significantly enhanced Mesp1, Tbx5, and Isl1 expression in p53+/+ and p53+/- MEFs. Oct4 also enhanced cTnT expression in all three cell lines, especially in p53+/- MEFs. Thus, inhibition of p53 expression and viral expression of Oct4 both promote transdifferentiation of MEFs into cardiomyocytes, establishing reciprocity of action in the process.

Cancer stem-like cells have cisplatin resistance and miR-93 regulate p21 expression in breast cancer

Aim: This study aims to examine the role of microRNAs (miRNAs) in regulating the expression of p21, a cyclin-dependent kinase inhibitor, and in inducing resistance to cisplatin, an anticancer drug. Methods: Human breast cancer cell line MDA-MB231 cells were separated into two subpopulations, cancer stem-like cells (CSCs) and cancer cells, based on the expression of cell surface antigens CD44 and CD24. Results: p21 protein expression was higher in CSCs than in cancer cells. Exposure of MDA-MB-231 cells to cisplatin increased p21 protein expression. However, p21 expression was significantly lower in cisplatin-treated CSCs than in cisplatin-treated cancer cells, suggesting that p21-dependent cell cycle suppression was lower in CSCs than in cancer cells. Moreover, caspase-3 activity was significantly lower in cisplatin-treated CSCs than in cisplatin-treated cancer cells, indicating that CSCs were more resistant to cisplatin-induced apoptosis than cancer cells. Treatment with miR-93 inhibitors increased p21 expression in CSCs, suggesting that miR-93 suppressed p21 expression. Conclusion: The results of the present study indicate that CSCs contribute to cisplatin resistance of MDA-MB231 cells and suggest that miR-93 inhibits the expression of p21, a factor involved in drug resistance.