eIF5B regulates the expression of PD-L1 in prostate cancer cells by interacting with Wig1.

BACKGROUND: Eukaryotic translation initiation factors (eIFs) are the key factors to synthesize translation initiation complexes during the synthesis of eukaryotic proteins. Besides, eIFs are especially important in regulating the immune function of tumor cells. However, the effect mechanism of eIFs in prostate cancer remains to be studied, which is precisely the purpose of this study. METHODS: In this study, three groups of prostate cancer cells were investigated. One group had its eIF5B gene knocked down; another group had its Programmed death 1 (PD-L1) overexpressed; the final group had its Wild-type p53-induced gene 1 (Wig1) overexpressed. Genetic alterations of the cancer cells were performed by plasmid transfection. The expression of PD-L1 mRNA was detected by quantitative real-time PCR (qRT-PCR), and the expressions of PD-L1 and eIF5B proteins were observed by western blot assays. Cell Counting Kit-8 (CCK-8), flow cytometry, Transwell and Transwell martrigel were used to investigated cell proliferation, apoptosis, migration and invasion, respectively. The effect of peripheral blood mononuclear cells (PBMCs) on tumor cells was observed, and the interaction between eIF5B and Wig1 was revealed by co-immunoprecipitation (CoIP) assay. Finally, the effects of interference with eIF5B expression on the growth, morphology, and immunity of the tumor, as well as PD-L1 expression in the tumor, were verified by tumor xenograft assays in vivo. RESULTS: Compared with normal prostate epithelial cells, prostate cancer cells revealed higher expressions of eIF5B and PD-L1 interference with eIF-5B expression can inhibit the proliferation, migration, invasion and PD-L1 expression of prostate cancer cells. Meanwhile, the cancer cell group with interference with eIF5B expression also demonstrated greater, apoptosis and higher vulnerability to PBMCs. CoIP assays showed that Wig1 could bind to eIF5B in prostate cancer cells, and its overexpression can inhibit the proliferation, migration, invasion and PD-L1 expression of cancer cells while promoting apoptosis. Moreover, interference with eIF5B expression can inhibit tumor growth, destroy tumor morphology, and suppress the proliferation of tumor cells. CONCLUSION: eIF5B can promote the expression of PD-L1 by interacting with Wig1. Besides, interference with eIF5B expression can inhibit the proliferation, migration, invasion and immunosuppressive response of prostate cancer cells. This study proposes a new target, eIF5B, for immunotherapy of prostate cancer.

The interplay between DNA damage and autophagy in lung cancer: A mathematical study.

The rising mortality in lung cancer, as well as the constraints of the existing drugs, have made it a major research topic. DNA damage marks the early onset of cancer as it often results from vulnerabilities due to UV rays, oxidative stress, ionizing radiation, and various types of genotoxic attacks. p53 plays an unequivocal role in the DNA repair process and has an abiding presence at the crossroads of the pathways linking DNA damage and cancer. p53 also regulates autophagy in a dual manner based on its cellular localization. The plexus of autophagy regulated by p53 includes AMPK and BCL2, which are positive and negative regulators of prime autophagy inducer beclin1, respectively. Although autophagy is a quintessential process, its levels need to be monitored as uncontrolled autophagy may lead to cell death. The association of p53 and autophagic cell death is very vital as the former acts whenever any threat comes to DNA while the latter may play a role in getting rid of the culprit cell. Therefore, in this paper, we have formulated a seven-dimensional mathematical model connecting p53, DNA damage, and autophagy in lung cancer. We performed both local and global sensitivity analysis along with parameter recalibration analysis to understand the system dynamics. We hypothesized that, by the modulation of beclin1 level, the regulation of AMPK and BCL2 could be a possible strategy to mitigate the progression of lung cancer.

The role of TP53 pathogenic variants in early-onset HER2-positive breast cancer.

Breast cancer is the most frequent event in Li-Fraumeni syndrome associated with germline TP53 variants. Some studies have shown that breast cancers in women with Li-Fraumeni syndrome are commonly HER2-positive, suggesting that HER2 amplification or over-expression in a young woman may be a useful criterion to test for germline variants in the TP53 gene. We assessed the prevalence of germline TP53 variants by Sanger sequencing or next-generation sequencing in 149 women with HER2-positive breast cancer diagnosed until age 40. The pattern of HER2 amplification was evaluated with dual-probe FISH in a subset of breast carcinomas from patients with germline TP53 variants as compared with those of noncarriers. Among 149 women tested, three presented a deleterious TP53 germline variant (2%), with one patient diagnosed at age 31 and the other two with bilateral breast cancer at ages 29/33 and 28/32, respectively. Three of the 36 patients (8.3%) with the first breast cancer diagnosed at age 31 or younger presented a pathogenic TP53 variant. Additionally, all TP53 deleterious variant carriers had a first degree relative diagnosed with different early-onset cancers (frequently not belonging to the Li-Fraumeni syndrome tumor spectrum) diagnosed at age 45 or younger. Higher levels of HER2 amplification were found in breast carcinomas of TP53 pathogenic variant carriers than in those of noncarriers. Deleterious germline TP53 variants account for a small proportion of early-onset HER2-positive breast cancers, but these seem to have higher HER2 amplification ratios. All TP53 pathogenic variant carriers found in this study had the first breast carcinoma diagnosed at age 31 or younger and a first-degree relative with early-onset cancer. Further studies are needed to clarify if HER2 status in early-onset breast cancer patients, in combination with other personal and/or familial cancer history, is useful to update the TP53 testing criteria.

Upregulation of mir-132 induces dopaminergic neuronal death via activating SIRT1/P53 pathway.

For several neurodegenerative disorders, including Parkinson's Disease (PD) and Alzheimer's Disease (AD), microRNAs (miRNAs) have been known to play a crucial role. So, in this study miR-132 and its role in PD cell models was investigated. We wanted to investigate the survival or death pathway involved in PD. We observed the expression levels of miR-132 in MPP+ - treated SH-SY5Y cell line, which acted as a PD cell model, and found an increased expression of miR-132. Moreover, through the Dual-Luciferase® Reporter (DLR™) Assay, it was also revealed that miR-132 targets SIRT1 3'UTR, a histone deacetylase, and decreases its activity, which results in increased acetylation of p53, an apoptotic inducer. p53 acetylation leads to overexpression of other pro-apoptotic genes like Puma and Noxa, which eventually leads to cell death. Here, we show that the upregulation of miR-132 in SH-SY5Y cells can induce apoptosis through the SIRT1/p53 pathway.

p53: 800 million years of evolution and 40 years of discovery.

The evolutionarily conserved p53 protein and its cellular pathways mediate tumour suppression through an informed, regulated and integrated set of responses to environmental perturbations resulting in either cellular death or the maintenance of cellular homeostasis. The p53 and MDM2 proteins form a central hub in this pathway that receives stressful inputs via MDM2 and respond via p53 by informing and altering a great many other pathways and functions in the cell. The MDM2-p53 hub is one of the hubs most highly connected to other signalling pathways in the cell, and this may be why TP53 is the most commonly mutated gene in human cancers. Initial or truncal TP53 gene mutations (the first mutations in a stem cell) are selected for early in cancer development inectodermal and mesodermal-derived tissue-specific stem and progenitor cells and then, following additional mutations, produce tumours from those tissue types. In endodermal-derived tissue-specific stem or progenitor cells, TP53 mutations are functionally selected as late mutations transitioning the mutated cell into a malignant tumour. The order in which oncogenes or tumour suppressor genes are functionally selected for in a stem cell impacts the timing and development of a tumour.

Cancer-Related Mutations Identified in Primed and Naive Human Pluripotent Stem Cells.

Human pluripotent stem cells (hPSCs) are known to harbor chromosomal aberrations, affecting their tumorigenic potential. We established a strategy to identify cancer-related point mutations in hPSCs, detecting recurrent mutations in over 20 genes, alongside those previously detected in p53. Importantly, naive hPSCs harbor, on average, four times more mutations than their primed counterparts, which appear primarily in pathways inhibited during naive conversion. Such cancer-related mutations should be taken into consideration in future applications, especially in clinical contexts.

The role of TP53 in acute myeloid leukemia: Challenges and opportunities.

The tumor suppressor gene TP53 is one of the most frequently mutated genes in human cancer. The central role of the TP53 protein in several fundamental processes such as cancer, aging, senescence, and DNA repair has ensured enormous attention. However, the role of TP53 in acute myeloid leukemia (AML) is enigmatic. Unlike many other human cancers, a vast majority of AMLs display no genomic TP53 alterations. There is now growing appreciation of the fact that the unaltered TP53 status of tumor cells can be exploited therapeutically. As most AMLs have an intact TP53 gene, its physiological tumor-suppressive roles could be harnessed. Therefore, the use of pharmacological activators of the TP53 pathway may provide clinical benefit in AML. Conversely, even though the frequency of TP53 mutations in AML is substantially lower than in other human cancers, TP53 mutations are associated with chemoresistance and high risk of relapse. In patients with TP53 mutations, these alterations may lead to novel, selective vulnerabilities, creating opportunities for therapeutic targeting of TP53 mutant AML. The mutational status of TP53 therefore poses challenges and opportunities in terms of advancing effective treatment strategies in AML. An increasing armamentarium of small-molecule activators of the TP53 pathway, and a growing understanding of molecular pathways triggered by mutant TP53 have accelerated efforts aimed at targeting TP53 function in AML. In combination with standard AML chemotherapy or emerging targeted therapies, pharmacological targeting of the TP53 pathway may provide therapeutic benefit in AML.

A novel androgen-reduced prostate-specific lncRNA, PSLNR, inhibits prostate-cancer progression in part by regulating the p53-dependent pathway.

BACKGROUND: Prostate cancer (PCa) is one of the most common cancers in males in China. Long noncoding RNAs (lncRNAs) reportedly play crucial roles in human cancer progression in many studies. However, the molecular mechanisms underlying PCa progression remain unclear. MATERIALS AND METHODS: We investigated the lncRNA transcriptome using publicly available RNA-sequencing data to identify prostate-specific lncRNAs. Then, the chromatin immunoprecipitation (ChIP) assay identified lncRNA with a direct binding to androgen receptor (AR), hereafter denoted as PSLNR. Quantitative real-time polymerase chain reaction analysis and Western blot analysis were performed to detect the expression of p53 signaling-related genes after overexpression PSLNR. The effects of overexpression of PSLNR on cell proliferation, cell cycle, and cell apoptosis were assessed by using CCK-8 and flow cytometric analysis. We then detected the expression of PSLNR in tissues. RESULT: We reported a novel androgen-reduced prostate-specific lncRNA, PSLNR, that inhibited PCa progression via the p53-dependent pathway. By analyzing the NOCODE data set, we reported that PSLNR was specifically expressed in the prostate, suggesting the potential of PSLNR as a biomarker for PCa treatment. The AR pathway was also confirmed to be an upstream regulation signaling pathway of PSLNR by transcriptionally regulating its expression in androgen-dependent PCa cells. PSLNR also significantly inhibited PCa proliferation by inducing cell apoptosis in a p53-dependent manner. Thus, PSLNR may be a candidate diagnosis and therapeutic target for PCa. CONCLUSIONS: Our study revealed for the first time a novel androgen-reduced prostate-specific lncRNA, PSLNR, which inhibited PCa progression via the p53-dependent pathway, suggesting that PSLNR may be a candidate diagnosis and therapeutic target for PCa.

Association of p53 expression with poor prognosis in patients with triple-negative breast invasive ductal carcinoma.

TP53 gene is mutated in approximately 80% of triple-negative breast cancer (TNBC). However, the prognostic significance of immunohistochemical (IHC)-detected p53 protein expression remains controversial in TNBC. In this study, we retrospectively analyzed the association between IHC-detected p53 expression and the prognosis in a cohort of 278 patients with stage I-III triple-negative breast invasive ductal carcinoma (IDC), who received surgery at the department of breast surgery in the Fourth Hospital of Hebei Medical University from 2010-01 to 2012-12. We found a positive expression ratio of IHC-detected p53 in triple-negative breast IDC of 58.6% (163/278). Furthermore, levels of expression were significantly associated with vessel tumor emboli and higher histologic grade (P = .038, P = .043, respectively), with the highest expression level observed in G3 breast cancer (64.7%). Additionally, Kaplan-Meier analysis showed that p53 expression indicated worse overall survival (OS) in the whole cohort (79.6% vs 89.6%, Log-rank test P = .025) as well as in stratified prognostic stage II patients (90.8% vs 100%, Log-rank test P = .027). The mortality risk of p53 expression patients was 2.22 times higher than that of p53 negative patients (HR: 2.222; 95%CI: 1.147-4.308). In addition, p53 expression was also associated with poor disease-free survival (DFS) (76.7% vs 86.8%, P = .020). Cox proportional hazard ratio model showed p53 expression was an independent risk factor for OS (P = .018) and DFS (P = .018) after controlling for tumor size, lymph node status, and vessel tumor emboli. Altogether, our data showed that IHC-detected p53 expression is a promising prognostic candidate for poor survival in triple-negative breast IDC patients. However, more studies are needed to determine if p53 may be applied to clinical practice as a biomarker and/or novel therapeutic target for TNBC.

Evaluation of clinical utility of P53 gene variations in repeated implantation failure.

Repeated implantation failure (RIF) is one the most common causes which showed during IVF (In vitro fertilization) procedure. We aim to evaluate the possibility role of nucleotide changes in rs1042522 (R72P; G/C) and rs17878362 (Ins16bp; N/D) of P53 gene in patients with RIF. In a case-control survey, we have considered 200 women, consisting of 100 cases with RIF and 100 women with the normal pregnancy. In order to determine the genotype frequencies, we used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The NN + ND/DD (dominant) genotype frequencies of rs17878362 variant revealed a significant difference between two groups (P = 0.001; OR 2.652; 95% CI 1.480-4.754). In addition, the CC + GC/GG (recessive) genotype frequencies of rs1042522 (R72P) variant indicated a significant difference between two groups (P = 0.018; OR 3.353; 95% CI 1.169-9.616). Our findings suggested that rs1042522 (R72P; G/C) and rs17878362 (Ins16bp; N/D) of P53 gene polymorphisms could be a genetic predisposing factor for RIF.

Reactivation of p53 gene by MDM2 inhibitors: A novel therapy for cancer treatment.

Cancer is an uncontrolled and abnormal growth of cells in the body. Gene that guards the cell cycle and function as tumor suppressor is p53 (also called as the guardian of the genome) which is encoded by the TP53 gene. Various events like DNA damage, heat shock, hypoxia and oncogene over expression, results in activation of p53.Thus, it plays a major role as a regulatory protein which regulates various diverse biological responses, responsible for genetic stability by preventing genome mutation. More than 50% mutations in human cancers along with the increase in expression of murine double minute 2 gene (mdm2), has been found as one of the reason for cancer progression. Murine double minute 2 (MDM2) is the negative regulator of p53 gene forming an autoregulatory feedback loop controlling each other cellular levels. Murine double minute 2 is unique E3 ubiquitin ligase protein which is responsible for ubiquitination and degradation of p53 gene. Many drugs/compounds have been developed for reactivation of p53 gene by inhibiting MDM2 interaction with p53, using MDM2 antagonism, inhibiting E3 ubiquitination of p53. Many compounds have entered clinical trials in haematological malignancies. This review will throw some light on reactivation of p53 gene by MDM2 and its homologues.

p53 deletion rescues lethal microcephaly in a mouse model with neural stem cell abscission defects.

Building a cerebral cortex of the proper size involves balancing rates and timing of neural stem cell (NSC) proliferation, neurogenesis and cell death. The cellular mechanisms connecting genetic mutations to brain malformation phenotypes are still poorly understood. Microcephaly may result when NSC divisions are too slow, produce neurons too early or undergo apoptosis but the relative contributions of these cellular mechanisms to various types of microcephaly are not understood. We previously showed that mouse mutants in Kif20b (formerly called Mphosph1, Mpp1 or KRMP1) have small cortices that show elevated apoptosis and defects in maturation of NSC midbodies, which mediate cytokinetic abscission. Here we test the contribution of intrinsic NSC apoptosis to brain size reduction in this lethal microcephaly model. By making double mutants with the pro-apoptotic genes Bax and Trp53 (p53), we find that p53-dependent apoptosis of cortical NSCs accounts for most of the microcephaly, but that there is a significant apoptosis-independent contribution as well. Remarkably, heterozygous p53 deletion is sufficient to fully rescue survival of the Kif20b mutant into adulthood. In addition, the NSC midbody maturation defects are not rescued by p53 deletion, showing that they are either upstream of p53 activation, or in a parallel pathway. Accumulation of p53 in the nucleus of mutant NSCs at midbody stage suggests the possibility of a novel midbody-mediated pathway for p53 activation. This work elucidates both NSC apoptosis and abscission mechanisms that could underlie human microcephaly or other brain malformations.

New tanshinone I derivatives S222 and S439 similarly inhibit topoisomerase I/II but reveal different p53-dependency in inducing G2/M arrest and apoptosis.

Tanshinone I (Tanshinone-1), a major active principle of the traditional Chinese medicine Salvia miltiorrhiza, possesses excellent anticancer properties, including inhibiting proliferation, angiogenesis and metastasis and overcoming multidrug resistance (MDR). However, its direct anticancer molecular target(s) remain unknown. Here we report that tanshinone-1 and its two new derivatives, S222 and S439, directly inhibit DNA topoisomerase I/II (Top1/2). With significantly improved water solubility, S222 and S439 displayed 12- and 14-times more potent proliferative inhibition than their parent tanshinone-1 in a panel of 15 cancer cell lines. Both retained tanshinone-1's anti-MDR and anti-angiogenesis properties and its capability to reduce the phosphorylation of Stat3 at Tyr705 with apparently enhanced efficacy and in these regards, S439 was also slightly more potent than S222. Both derivatives and tanshinone-1 directly inhibited Top1 and Top2 at molecular and cellular levels; the derivatives displayed similar potency but both were more potent than tanshinone-1. The inhibition of S222 and S439 on Top1 and Top2 was also more potent than that of the Top1 inhibitor hydroxylcamptothecin and the Top2 inhibitor etoposide, respectively. Consistently, tanshinone-1 and its derivatives induced DNA double-strand breaks, G2/M arrest and apoptosis. Unexpectedly, the derivatives demonstrated different p53-dependency in inducing both cell cycle arrest and apoptosis. S222 showed no obvious p53-dependency. In contrast, S439 induced more G2/M arrest in p53-proficient cells than in p53-deficient cells while its apoptotic induction was the opposite. However, their proliferative inhibition was independent of the p53 status. Due to their structures different from the known Top1, Top2 and dual Top1/2 inhibitors, our results indicate that tanshinone-1 and its derivatives are a new type of dual Top1/2 inhibitors.

Catecholamine-Induced Senescence of Endothelial Cells and Bone Marrow Cells Promotes Cardiac Dysfunction in Mice.

Previous studies have suggested that cellular senescence plays a central role in the progression of pathologic changes in the failing heart. It is well known that the sympathetic nervous system is activated in patients with heart failure, and this change is associated with poor clinical outcomes. Sympathetic activation increases the levels of various catecholamines, such as epinephrine and norepinephrine, but the contribution of these catecholamines to cellular senescence associated with heart failure remains to be determined. We found that catecholamine infusion induced senescence of endothelial cells and bone marrow cells, and promoted cardiac dysfunction in mice. In C57BL/6NCr mice, the continuous infusion of isoproterenol-induced cardiac inflammation and cardiac dysfunction. Expression of p53, a master regulator of cellular senescence, was increased in the cardiac tissue and bone marrow cells of these mice. Suppression of cellular senescence by genetic deletion of p53 in endothelial cells or bone marrow cells led to improvement of isoproterenol-induced cardiac dysfunction. In vitro studies showed that adrenergic signaling increased the expression of p53 and adhesion molecules by endothelial cells and macrophages. Our results indicate that catecholamine-induced senescence of endothelial cells and bone marrow cells plays a pivotal role in the progression of heart failure. Suppression of catecholamine-p53 signaling is crucial for inhibition of remodeling in the failing heart.

Involvement of RPL11 in the enhancement of P53 stability by a podophyllum derivative, a topoisomerase II inhibitor.

In previous work, we presented experimental and theoretical evidence that D-3F or 4-N-(2-Amino-3-fluoropyridine)-4-deoxidation-4'-demethylepipofophyllotoxin induced G2 /M phase arrest and apoptosis, purportedly by increasing the expression of P53. However, the precise mechanism of D-3F action is currently unknown. Here, we investigated the mechanism by which D-3F treatment induces increased expression of P53. This study showed that D-3F definitively inhibited the activity of topoisomerase II in a dose-dependent manner and resulted in DNA damage. The results were in overall agreement with modeling and docking studies performed on D-3F. In addition, D-3F increased the levels of P53 and P21 in HeLa cells in a dose-dependent manner, this in turn prolonged the half-life of P53. Taken together, these data suggested that D-3F-mediated transient enhancement of P53 stabilization may be critical for the P53/P21 signalling pathway leading to G2 /M phase arrest on HeLa cells. Furthermore, D-3F downregulated the phosphorylation of E3 ubiquitin-protein ligase murine double minute 2 (Mdm2) at Ser166, inhibited Mdm2-mediated ubiquitination of P53, and released 60S ribosomal protein L11 (RPL11) from the nucleolus into the nucleoplasm. To conclude, the topoisomerase II inhibitor D-3F causes P53 to accumulate in HeLa cell lines by enhancing its stability as a result of DNA-damage induced RPL11 relocalization and subsequent blocking of the P53-Mdm2 feedback loop.

All-trans-retinoic acid ameliorates doxorubicin-induced cardiotoxicity: in vivo potential involvement of oxidative stress, inflammation, and apoptosis via caspase-3 and p53 down-expression.

The present study aimed to investigate the potential protective effect of all-trans-retinoic acid (ATRA, a natural derivative of vitamin A) against doxorubicin (DOX)-induced in vivo cardiac toxicity and its underlying mechanisms. Forty male albino rats were allocated into control, ATRA (0.5 mg/kg bwt, intraperitoneally daily), DOX (2.5 mg/kg bwt, intraperitoneally twice weekly for 3 weeks), and DOX + ATRA groups. Serum lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase-cardiac type (CK-MB), troponin I, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) were measured. In addition, cardiac glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), and malondialdehyde (MDA) were determined. Cardiac tissues were examined for histopathologic changes and immunoexpression of pro-apoptotic caspase 3 and tumor-suppressor p53 proteins. DOX caused severe myocardial damage; degenerative and necrotic changes and worsened cardiac function biomarkers; and elevated serum LDH, CK, CK-MB, and troponin I. In addition, DOX inhibited cardiac antioxidative enzymes (GSH, GSH-Px, SOD, CAT) activities and enhanced MDA level. DOX increased serum proinflammatory cytokines (TNF-α, IL-6) and area percent of caspase 3 and p53 immunoexpression in heart tissues. Pretreatment with ATRA maintained cardiac function biomarkers, and reduced proinflammatory cytokines, lipid peroxidation, and immunoexpression of caspase 3 and p53. Moreover, ATRA improved cardiac histoarchitecture, as well as the activities of antioxidative enzymes. Collectively, ATRA can counteract DOX-induced cardiomyopathy through antioxidative and anti-inflammatory properties, besides suppression of the activation of the mitochondrial apoptotic pathway.

Eixo XPC-P53-H202 e disfunção mitocondrial: qual é o fator central? / XPC-p53-H2O2 axis and mitochondrial disfunction: Which is the key player

A ausência de XPC, uma proteína canonicamente envolvida em reparo de DNA por excisão de nucleotídeos, está associada a vários fenótipos característicos de disfunção mitocondrial como o desequilíbrio entre os complexos da cadeia transportadora de elétrons (CTE), redução no consumo de oxigênio, maior produção de peróxido de hidrogênio, e maior sensibilidade a agentes que causam estresse mitocondrial. Contudo, uma descrição mecanística da relação entre deficiência de XPC e disfunção mitocondrial ainda não está bem estabelecida. Aqui mostramos que a deficiência de XPC está associada ao aumento na expressão do supressor de tumor p53. Essa alteração é acompanhada pelo aumento da expressão de diversas proteínas que participam em importantes funções mitocondriais. A inibição de p53 reverte a superexpressão de algumas dessas proteínas. O tratamento com o inibidor do Complexo III da CTE antimicina A induz aumento da expressão de p53 de forma mais acentuada na linhagem Xpc-/-, enquanto o tratamento com o antioxidante N-acetilcisteína diminue a produção basal de H2O2, expressão de p53 e sensibilidade aumentada ao tratamento com antimicina A. Em conjunto, nossos resultados suportam a hipótese de que o aumento da produção de H2O2 em células Xpc-/- tem um papel causal na regulação da expressão de p53 e na disfunção mitocondrial

Although XPC has been initially implicated in the nucleotide excision DNA repair pathway, its deficiency is associated with mitochondrial dysfunction, including unbalanced electron transport chain (ETC) activity, lower oxygen consumption, increased hydrogen peroxide production, and greater sensitivity to mitochondrial stress. However, a mechanistic understanding of the role of XPC in regulating mitochondrial function is still not well established. Here we show that XPC deficiency is associated with increased expression of the tumor suppressor p53, which is accompanied by increased expression of several proteins that participate in important mitochondrial functions. Inhibition of p53 reverses the overexpression of some of these proteins. In addition, treatment with the ETC inhibitor antimycin A induces p53 expression more robustly in the Xpc-/- cells, while treatment with the antioxidant N-acetylcysteine decreases basal H2O2 production, p53 expression and sensitivity to antimycin A treatment. Together, our results support a model in which increased H2O2 production in Xpc-/- causes upregulation of p53 expression and mitochondrial dysfunction

Mycobacteria exploit nitric oxide-induced transformation of macrophages into permissive giant cells.

Immunity to mycobacteria involves the formation of granulomas, characterized by a unique macrophage (MΦ) species, so-called multinucleated giant cells (MGC). It remains unresolved whether MGC are beneficial to the host, that is, by prevention of bacterial spread, or whether they promote mycobacterial persistence. Here, we show that the prototypical antimycobacterial molecule nitric oxide (NO), which is produced by MGC in excessive amounts, is a double-edged sword. Next to its antibacterial capacity, NO propagates the transformation of MΦ into MGC, which are relatively permissive for mycobacterial persistence. The mechanism underlying MGC formation involves NO-induced DNA damage and impairment of p53 function. Moreover, MGC have an unsurpassed potential to engulf mycobacteria-infected apoptotic cells, which adds a further burden to their antimycobacterial capacity. Accordingly, mycobacteria take paradoxical advantage of antimicrobial cellular efforts by driving effector MΦ into a permissive MGC state.

Nutlin-3 plus tanshinone IIA exhibits synergetic anti-leukemia effect with imatinib by reactivating p53 and inhibiting the AKT/mTOR pathway in Ph+ ALL.

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is triggered by BCR/ABL kinase. Recent efforts focused on the development of more potent tyrosine kinase inhibitors (TKIs) that also inhibit mutant tyrosine kinases such as nilotinib and dasatinib. Although major advances in the treatment of this aggressive disease with potent inhibitors of the BCR/ABL kinases, patients in remission frequently relapse due to drug resistance possibly mediated, at least in part, by compensatory activation of growth-signaling pathways and protective feedback signaling of leukemia cells in response to TKI treatment. Continuous activation of AKT/mTOR signaling and inactivation of p53 pathway were two mechanisms of TKI resistance. Here, we reported that nutlin-3 plus tanshinone IIA significantly potentiated the cytotoxic and apoptotic induction effects of imatinib by down-regulation of the AKT/mTOR pathway and reactivating the p53 pathway deeply in Ph+ ALL cell line. In primary samples from Ph+ ALL patients, nutlin-3 plus tanshinone IIA also exhibited synergetic cytotoxic effects with imatinib. Of note, three samples from Ph+ ALL patients harboring T315I mutation also showed sensitivity to the combined treatment of imatinib, nutlin-3 plus tanshinone IIA. In Ph+ ALL mouse models, imatinib combined with nutlin-3 plus tanshinone IIA also exhibited synergetic effects on reduction in leukemia burden. These results demonstrated that nutlin-3 plus tanshinone IIA combined TKI might be a promising treatment strategy for Ph+ ALL patients.

F4/80+ Macrophages Contribute to Clearance of Senescent Cells in the Mouse Postpartum Uterus.

Cellular senescence, defined as an irreversible cell cycle arrest, exacerbates the tissue microenvironment. Our previous study demonstrated that mouse uterine senescent cells were physiologically increased according to gestational days and that their abnormal accumulation was linked to the onset of preterm delivery. We hypothesized that there is a mechanism for removal of senescent cells after parturition to maintain uterine function. In the current study, we noted abundant uterine senescent cells and their gradual disappearance in wild-type postpartum mice. F4/80+ macrophages were present specifically around the area rich in senescent cells. Depletion of macrophages in the postpartum mice using anti-F4/80 antibody enlarged the area of senescent cells in the uterus. We also found excessive uterine senescent cells and decreased second pregnancy success rate in a preterm birth model using uterine p53-deleted mice. Furthermore, a decrease in F4/80+ cells and an increase in CD11b+ cells with a senescence-associated inflammatory microenvironment were observed in the p53-deleted uterus, suggesting that uterine p53 deficiency affects distribution of the macrophage subpopulation, interferes with senescence clearance, and promotes senescence-induced inflammation. These findings indicate that the macrophage is a key player in the clearance of uterine senescent cells to maintain postpartum uterine function.