Modulating the p53 pathway

Post-translational modification in the pathogenesis of vitiligo

Vitiligo is a chronic dermatological condition marked by the loss of skin pigmentation. Its complex etiology involves multiple factors and has not been completely elucidated. Protein post-translational modification pathways have been proven to play a significant role in inflammatory skin diseases, yet research in the context of vitiligo remains limited. This review focuses on the role of post-translational modifications in vitiligo pathogenesis, especially their impact on cellular signaling pathways related to immune response and melanocyte survival. Current therapeutic strategies targeting these pathways are discussed, emphasizing the potential for novel treatments in vitiligo management.

PX-478 induces apoptosis in acute myeloid leukemia under hypoxia by inhibiting the PI3K/AKT/mTOR pathway through downregulation of GBE1

Acute myeloid leukemia (AML) is a highly heterogeneous hematologic malignancy characterized by limited therapeutic options and a pronounced tendency for relapse. PX-478, a novel inhibitor of hypoxia-inducible factor 1-alpha (HIF-1α), has demonstrated antitumor activity across various cancer models, but its specific role in AML remains unexplored. This study aimed to explore the potential target and mechanism of PX-478-induced AML cell apoptosis. First, PX-478 induced AML cell apoptosis in vitro under hypoxia via modulation of the Bcl-2 family and activation of the mitochondria-mediated caspase cascade, exhibiting a concentration-dependent effect. Additionally, in vivo administration of PX-478 led to notable inhibition of subcutaneous AML xenograft growth in mice, coupled with increased tumor cell apoptosis. RNA sequencing and cellular studies revealed downregulation of the PI3K/AKT/mTOR signaling pathway in PX-478-treated cells. Consistently, cellular studies also implicated PI3K/AKT/mTOR pathway in PX-478-induced AML cell apoptosis. Furthermore, by screening for RNA sequencing differential genes and subsequent experimental verification, Glycogen branching enzyme 1 (GBE1) may be involved in PX-478-induced apoptosis in AML cells. We found that inhibiting GBE1 expression in AML cells (siGBE1) led to downregulation of the PI3K/AKT/mTOR pathway and induced apoptosis. In experiments using AML cells with reduced GBE1 expression (shGBE1), PX-478 treatment did not further downregulate the pathway or enhance apoptosis. Re-expression of GBE1 in shGBE1 cells alleviated apoptosis and reduced PX-478- induced apoptosis and pathway downregulation. In conclusion, our findings provide convincing evidence that PX-478 induces apoptosis by inhibiting the PI3K/AKT/mTOR pathway through downregulation of GBE1 in AML cells.

The phosphorylation-deubiquitination positive feedback loop of the CHK2-USP7 axis stabilizes p53 under oxidative stress

p53 regulates multiple signaling pathways and maintains cell homeostasis under conditions of DNA damage and oxidative stress. Although USP7 has been shown to promote p53 stability via deubiquitination, the USP7-p53 activation mechanism has remained unclear. Here, we propose that DNA damage induces reactive oxygen species (ROS) production and activates ATM-CHK2, and CHK2 then phosphorylates USP7 at S168 and T231. USP7 phosphorylation is essential for its deubiquitination activity toward p53. USP7 also deubiquitinates CHK2 at K119 and K131, increasing CHK2 stability and creating a positive feedback loop between CHK2 and USP7. Compared to peri-tumor tissues, thyroid cancer and colon cancer tissues show higher CHK2 and phosphorylated USP7 (S168, T231) levels, and these levels are positively correlated. Collectively, our results uncover a phosphorylation-deubiquitination positive feedback loop involving the CHK2-USP7 axis that supports the stabilization of p53 and the maintenance of cell homeostasis.

Prenatal cadmium exposure impairs neural tube closure via inducing excessive apoptosis in neuroepithelium

Birth defects have become a public health concern. The hazardous environmental factors exposure to embryos could increase the risk of birth defects. Cadmium, a toxic environmental factor, can cross the placental barrier during pregnancy. Pregnant woman may be subjected to cadmium before taking precautionary protective actions. However, the link between birth defects and cadmium remains obscure. Cadmium exposure can induce excessive apoptosis in neuroepithelium during embryonic development progresses. Cadmium exposure activated the p53 via enhancing the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and reactive oxygen species' (ROS) level. And cadmium decreases the level of Paired box 3 (Pax3) and murine double minute 2 (Mdm2), disrupting the process of p53 ubiquitylation. And p53 accumulation induced excessive apoptosis in neuroepithelium during embryonic development progresses. Excessive apoptosis led to the failure of neural tube closure. The study emphasizes that environmental materials may increase the health risk for embryos. Cadmium caused the failure of neural tube closure during early embryotic day. Pregnant women may be exposed by cadmium before taking precautionary protective actions, because of cadmium concentration-containing foods and environmental tobacco smoking. This suggests that prenatal cadmium exposure is a threatening risk factor for birth defects.

Discovery of Novel Antitumor Small-Molecule Agent with Dual Action of CDK2/p-RB and MDM2/p53

Cell cycle-dependent kinase 2 (CDK2) is located downstream of CDK4/6 in the cell cycle and regulates cell entry into S-phase by binding to Cyclin E and hyper-phosphorylating Rb. Proto-oncogene murine double minute 2 (MDM2) is a key negative regulator of p53, which is highly expressed in tumors and plays an important role in tumorigenesis and progression. In this study, we identified a dual inhibitor of CDK2 and MDM2, III-13, which had good selectivity for inhibiting CDK2 activity and significantly reduced MDM2 expression. In vitro results showed that III-13 inhibited proliferation of a wide range of tumor cells, regardless of whether Cyclin E1 (CCNE1) was overexpressed or not. The results of in vivo experiments showed that III-13 significantly inhibited proliferation of tumor cells and did not affect body weight of mice. The results of the druggability evaluation showed that III-13 was characterized by low bioavailability and poor membrane permeability when orally administered, suggesting the necessity of further structural modifications. Therefore, this study provided a lead compound for antitumor drugs, especially those against CCNE1-amplified tumor proliferation.

Knockdown of hCINAP sensitizes colorectal cancer cells to ionizing radiation

Colorectal cancer (CRC) poses a significant challenge in terms of treatment due to the prevalence of radiotherapy resistance. However, the underlying mechanisms responsible for radio-resistance in CRC have not been thoroughly explored. This study aimed to shed light on the role of human coilin interacting nuclear ATPase protein (hCINAP) in radiation-resistant HT-29 and SW480 CRC cells (HT-29-IR and SW480-IR) and investigate its potential implications. Firstly, radiation-resistant CRC cell lines were established by subjecting HT-29 and SW480 cells to sequential radiation exposure. Subsequent analysis revealed a notable increase in hCINAP expression in radiation-resistant CRC cells. To elucidate the functional role of hCINAP in radio-resistance, knockdown experiments were conducted. Remarkably, knockdown of hCINAP resulted in an elevation of reactive oxygen species (ROS) generation upon radiation treatment and subsequent activation of apoptosis mediated by mitochondria. These observations indicate that hCINAP depletion enhances the radiosensitivity of CRC cells. Conversely, when hCINAP was overexpressed, it was found to enhance the radio-resistance of CRC cells. This suggests that elevated hCINAP expression contributes to the development of radio-resistance. Further investigation revealed an interaction between hCINAP and ATPase family AAA domain containing 3A (ATAD3A). Importantly, ATAD3A was identified as an essential factor in hCINAP-mediated radio-resistance. These findings establish the involvement of hCINAP and its interaction with ATAD3A in the regulation of radio-resistance in CRC cells. Overall, the results of this study demonstrate that upregulating hCINAP expression may improve the survival of radiation-exposed CRC cells. Understanding the intricate molecular mechanisms underlying hCINAP function holds promise for potential strategies in targeted radiation therapy for CRC. These findings emphasize the importance of further research to gain a comprehensive understanding of hCINAP's precise molecular mechanisms and explore its potential as a therapeutic target in overcoming radio-resistance in CRC. By unraveling the complexities of hCINAP and its interactions, novel therapeutic approaches may be developed to enhance the efficacy of radiation therapy and improve outcomes for CRC patients.

Role of m6A modification in regulating the PI3K/AKT signaling pathway in cancer

The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays a crucial role in the pathogenesis of cancer. The dysregulation of this pathway has been linked to the development and initiation of various types of cancer. Recently, epigenetic modifications, particularly N6-methyladenosine (m6A), have been recognized as essential contributors to mRNA-related biological processes and translation. The abnormal expression of m6A modification enzymes has been associated with oncogenesis, tumor progression, and drug resistance. Here, we review the role of m6A modification in regulating the PI3K/AKT pathway in cancer and its implications in the development of novel strategies for cancer treatment.

A multi-omics approach based on 1H-NMR metabonomics combined with target protein analysis to reveal the mechanism of RIAISs on cervical carcinoma patients

Cervical carcinoma (CC) is the fourth most common cancer in females and radiotherapy is always as the definitive therapy for cervical cancer patients who are not suitable for surgery. Radiation-induced acute intestinal symptoms (RIAISs) occur in 50-80% of cervical cancer patients. Some research shows that RIAISs may relate to inflammatory reaction by radiotherapy but the action mechanism is also not clearly and the details of the molecular mechanism are still urgently needed. In this paper, basing on ¹H-NMR metabonomic and bioinformatics analysis, an integrated multi-omics analysis including metabonomics and bioinformatics was performed. We propose a hypothesis about pathogenic mechanism on RIAISs and proofed it through western-blot. Our results indicated significant dysregulation of metabolic pathways in RIAIS patients. Most importantly, we found that RIAISs were associated p53 and PI3K-AKT pathway.

Value of glycogen synthase 2 in intrahepatic cholangiocarcinoma prognosis assessment and its influence on the activity of cancer cells

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver tumor with increasing incidence worldwide. Metabolic reprogramming caused by metabolic related gene disorders is a prominent hallmark of tumors, among which Glycogen Synthase 2 (GYS2) is the key gene responsible for regulating cellular energy metabolism, and its expression disorders are closely related to various tumors and glycometabolic diseases. However, we still know nothing about its role in ICC. This study is intended to reveal the functional role of GYS2 in the ICC progress and explore the underlying mechanism. Based on the integrated pan-cancer analysis of GYS2 in the GEPIA database, the expression of GYS2 in paired ICC and adjacent non tumor tissues was detected by qPCR. It was found that the expression of GYS2 was significantly down-regulated in ICC. Further analysis showed that its low expression was not only associated with the degree of pathological differentiation, tumor size, microvascular invasion and lymph node metastasis, but also an independent risk factor for unfavorable prognosis. Functional studies have shown that GYS2 overexpression can significantly impair the proliferation, replication, cloning, migration and invasion of cholangiocarcinoma cells, while the silencing GYS2 dramatically promotes the development of the aforementioned phenotypes, the underlying mechanism may be that GYS2 activates the P53 pathway. In conclusions,low GYS2 expression in ICC predicted unfavorable patient outcomes; GYS2 overexpression could significantly impair the proliferation, migration and invasion of cholangiocarcinoma cells via activating the P53 pathway and GYS2 was expected to become a potential therapeutic target for such patients.

The potential risks of chronic fluoride exposure on nephrotoxic via altering glucolipid metabolism and activating autophagy and apoptosis in ducks

Fluoride is one of the most widely distributed elements in nature, while some fluorine-containing compounds are toxic to several vertebrates at certain levels. The current study was performed to evaluate the nephrotoxic effects of fluoride exposure in ducks. The results showed that the renal index was decreased in NaF group, and fluoride exposure significantly decreased the levels of serum Albumin, Glucose, Total cholesterol, Urea, protein and Triglycerides, confirming that NaF exhibited adverse effects on the kidney. The overall structure of renal cells showed damage with the signs of nuclelytic, vacuolar degeneration, atrophy, renal cystic cavity widening after fluoride induction. Renal vascular growth was impaired as the expression of VEGF and HIF-1α decreased (p > 0.05). More importantly, autophagy and apoptosis levels of CYT C, LC3, p62, Beclin, M-TOR, Bax and Caspase-3 were increased (p < 0.05) in the NaF treated group. Interestingly, our results showed that Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) activated the M-TOR autophagy pathway. Meanwhile, the PE acted on Atg5/ LC3 autophagy factor, followed by the auto-phagosome generation and activation of cell autophagy. These results indicate that NaF exposure to duck induced nephron-toxicity by activating autophagy, apoptosis and glucolipid metabolism pathways, which suggest that fluorine exposure poses a risk of poisoning.

Unique structural features of the adenylate kinase hCINAP/AK6 and its multifaceted functions in carcinogenesis and tumor progression

Human coilin-interacting nuclear ATPase protein (hCINAP), also known as adenylate kinase 6 (AK6), is an atypical adenylate kinase with critical roles in many biological processes, including gene transcription, ribosome synthesis, cell metabolism, cell proliferation and apoptosis, DNA damage responses, and genome stability. Furthermore, hCINAP/AK6 dysfunction is associated with cancer and various inflammatory diseases. In this review, we summarize the structural features and biological roles of hCINAP in several important signaling pathways, as well as its connection with tumor onset and progression.

Mice with a Mutation in the Mdm2 Gene That Interferes with MDM2/Ribosomal Protein Binding Develop a Defect in Erythropoiesis

MDM2, an E3 ubiquitin ligase, is an important negative regulator of tumor suppressor p53. In turn the Mdm2 gene is a transcriptional target of p53, forming a negative feedback loop that is important in cell cycle control. It has recently become apparent that the ubiquitination of p53 by MDM2 can be inhibited when certain ribosomal proteins, including RPL5 and RPL11, bind to MDM2. This inhibition, and the resulting increase in p53 levels has been proposed to be responsible for the red cell aplasia seen in Diamond-Blackfan anemia (DBA) and in 5q- myelodysplastic syndrome (MDS). DBA and 5q- MDS are associated with inherited (DBA) or acquired (5q- MDS) haploinsufficiency of ribosomal proteins. A mutation in Mdm2 causing a C305F amino acid substitution blocks the binding of ribosomal proteins. Mice harboring this mutation (Mdm2^C305F), retain a normal p53 response to DNA damage, but lack the p53 response to perturbations in ribosome biogenesis. While studying the interaction between RP haploinsufficiency and the Mdm2^C305F mutation we noticed that Mdm2^C305F homozygous mice had altered hematopoiesis. These mice developed a mild macrocytic anemia with reticulocytosis. In the bone marrow (BM), these mice showed a significant decrease in Ter119^hi cells compared to wild type (WT) littermates, while no decrease in the number of mature erythroid cells (Ter119^hiCD71^low) was found in the spleen, which showed compensated bone marrow hematopoiesis. In methylcellulose cultures, BFU-E colonies from the mutant mice were slightly reduced in number and there was a significant reduction in CFU-E colony numbers in mutant mice compared with WT controls (p < 0.01). This erythropoietic defect was abrogated by concomitant p53 deficiency (Trp53^ko/ko). Further investigation revealed that in Mdm2^C305F animals, there was a decrease in Lin^-Sca-1⁺c-Kit⁺ (LSK) cells, accompanied by significant decreases in multipotent progenitor (MPP) cells (p < 0.01). Competitive BM repopulation experiments showed that donor BM harboring the Mdm2^C305F mutation possessed decreased repopulation capacity compared to WT BM, suggesting a functional stem cell deficit. These results suggest that there is a fine tuned balance in the interaction of ribosomal proteins with the MDM2/p53 axis which is important in normal hematopoiesis.

Molecular mechanisms of etoposide

Etoposide derives from podophyllotoxin, a toxin found in the American Mayapple. It was first synthesized in 1966 and approved for cancer therapy in 1983 by the U.S. Food and Drug Administration (Hande, 1998[25]). Starting from 1980s several studies demonstrated that etoposide targets DNA topoisomerase II activities thus leading to the production of DNA breaks and eliciting a response that affects several aspects of cell metabolisms. In this review we will focus on molecular mechanisms that account for the biological effect of etoposide.

iTRAQ-based proteomic analysis of dioscin on human HCT-116 colon cancer cells

Dioscin shows various pharmacological effects. However, its activity on colorectal cancer is still unknown. The present work showed that dioscin significantly inhibited cell proliferation on human HCT-116 colon cancer cells, and affected Ca(2+) release and ROS generation. The content of nitric oxide (NO) and its producer inducible NO synthase (iNOS) associated with DNA damage and aberrant cell signaling were assayed using the kits. DNA damage and cell apoptosis caused by dioscin were also analyzed through single-cell gel electrophoresis and in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling assays. The results showed that dioscin increased the levels of NO and inducible NO synthase. The comet length in dioscin-treated groups was much longer than that of the control group, and the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling positive cells (apoptotic cells) was significantly increased by the compound (p < 0.01). Furthermore, dioscin caused mitochondrial damage and G2/M cell cycle arrest through transmission electron microscopy and flow cytometry analysis, respectively. To study the cytotoxic mechanism of dioscin, an iTRAQ-based proteomics approach was used. There were 288 significantly different proteins expressed in response to dioscin, which were connected with each other and were involved in different Kyoto Encyclopedia of Genes and Genomes pathways. Then, some differentially expressed proteins involved in oxidative phosphorylation, Wnt, p53, and calcium signaling pathways were validated by Western blotting and quantitative real-time PCR assays. Our work elucidates the molecular mechanism of dioscin-induced cytotoxicity in colon cancer cells, and the identified targets may be useful for treatment of colorectal cancer in future.

Screening and evaluation of traditional Chinese medicine by microarray expression analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza is a Chinese medicinal herb, which is widely used for the treatment of cardiovascular disorders. In this article, we investigated the effects of Salvia miltiorrhiza and its hydrophilic and lipophilic components (HCS and LCS) on human umbilical vein endothelial cells (HUVECs), and the molecular mechanism was explored by microarray gene expression profiling.

MATERIALS AND METHODS

Cell proliferation and migration were used to evaluate the angiogenic effects of HCS, LCS and total extract of Salvia miltiorrhiza (TES). Microarray technology was applied to detect the gene expression of HUVECs treated with TES, HCS and LCS. Besides, quantitative real-time PCR was used to verify the microarray results.

RESULTS

Our results showed that LCS inhibited the proliferation and migration of HUVECs, HCS promoted the proliferation and migration of HUVECs, and TES did not affect the viability of HUVECs at the concentration of 5 µg/mL. From the result of principle component analysis (PCA) of microarray data, the effect of LCS on HUVECs was significantly different from the other components. Moreover, there were more differentially expression genes in LCS group than in the other groups, which meant LCS had a strong influence on HUVECs. Compared with untreated cells, 511 significantly changed genes had been detected in LCS treated cells and 236 (approximately 46%) of them were up-regulated. The mRNA expression of IL-6 was found to be increased significantly in LCS group.

CONCLUSIONS

In Salvia miltiorrhiza, HCS and LCS had opposite effects on HUVECs. LCS showed significantly inhibitory action on HUVECs proliferation and migration. It was proposed that LCS could apply in the diseases caused by vascular anomaly hyperplasia. In the mechanism of action of LCS on HUVECs, the pathways of ErbB, MAPK, p53, oxidative phosphorylation and inflammatory response were involved.

Impact of the p53 status of tumor cells on extrinsic and intrinsic apoptosis signaling

Background

The p53 protein is the best studied target in human cancer. For decades, p53 has been believed to act mainly as a tumor suppressor and by transcriptional regulation. Only recently, the complex and diverse function of p53 has attracted more attention. Using several molecular approaches, we studied the impact of different p53 variants on extrinsic and intrinsic apoptosis signaling.

Results

We reproduced the previously published results within intrinsic apoptosis induction: while wild-type p53 promoted cell death, different p53 mutations reduced apoptosis sensitivity. The prediction of the impact of the p53 status on the extrinsic cell death induction was much more complex. The presence of p53 in tumor cell lines and primary xenograft tumor cells resulted in either augmented, unchanged or reduced cell death. The substitution of wild-type p53 by mutant p53 did not affect the extrinsic apoptosis inducing capacity.

Conclusions

In summary, we have identified a non-expected impact of p53 on extrinsic cell death induction. We suggest that the impact of the p53 status of tumor cells on extrinsic apoptosis signaling should be studied in detail especially in the context of therapeutic approaches that aim to restore p53 function to facilitate cell death via the extrinsic apoptosis pathway.

hCINAP is a novel regulator of ribosomal protein-HDM2-p53 pathway by controlling NEDDylation of ribosomal protein S14

The tumor-suppressor p53 provides a critical brake on tumor development. HDM2 (human double-minute 2), a p53 E3 ubiquitin ligase, is the principal cellular antagonist of p53. Mounting evidence has suggested that ribosomal proteins (RPs) modulate HDM2-p53 as a novel pathway for regulating p53 signaling. However, the upstream regulators that mediate RP-HDM2-p53 circuits remain poorly understood. Here we identify human coilin-interacting nuclear ATPase protein (hCINAP) as an interacting partner of ribosomal protein S14 (RPS14). RPS14 stabilized and activated p53 by inhibiting HDM2-mediated p53 polyubiquitination and degradation. More importantly, RPS14 was specifically modified with NEDD8 and hCINAP inhibited RPS14 NEDDylation by recruiting NEDD8-specific protease 1. The decrease in RPS14 NEDDylation led to reduced stability and incorrect localization of RPS14, thereby attenuating the interaction between RPS14 and HDM2. Free HDM2 stimulated p53 polyubiquitination and degradation. In conclusion, we demonstrate that hCINAP acts as a novel regulator of RPS14-HDM2-p53 by regulating the interaction between RPS14 and HDM2 through the control of RPS14 NEDDylation. These findings suggest that hCINAP is an important regulator of RP-HDM2-p53 pathway and a potential anticancer drug target.

Dietary downregulation of mutant p53 levels via glucose restriction: mechanisms and implications for tumor therapy

The majority of human tumors express mutant forms of p53 at high levels, promoting gain of oncogenic functions and correlating with disease progression, resistance to therapy and unfavorable prognosis. p53 mutant accumulation in tumors is attributed to the ability to evade degradation by the proteasome, the only currently recognized machinery for p53 disruption. We report here that glucose restriction (GR) induces p53 mutant deacetylation, routing it for degradation via autophagy. Depletion of p53 leads, in turn, to robust autophagic activation and to cell death, while expression of degradation-defective mutant p53 blocks autophagy and enables survival to GR. Furthermore, we found that a carbohydrate-free dietetic regimen that lowers the fasting glucose levels blunts p53 mutant expression and oncogenic activity relative to a normal diet in several animal model systems. These findings indicate that the stability of mutant forms of p53 is influenced by the levels of glucose and by dietetic habits. They also unravel the existence of an inhibitory loop between autophagy and mutant p53 that can be exploited therapeutically.

Triptolide sensitizes TRAIL-induced apoptosis in prostate cancer cells via p53-mediated DR5 up-regulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent for cancer therapy. However, a number of prostate cancer cells exhibit high resistance to TRAIL effect. In this study, we found that Triptolide, a Chinese medicine, significantly sensitizes prostate cancer cells to TRAIL-mediated cellular apoptosis by up-regulating DR5 expression. Triptolide treatment can suppress Akt/Hdm2 signaling pathway, and lead to p53 accumulation, thereby up-regulating DR5 expression. Taken together, all evidences indicate that Triptolide may become a promising therapeutic agent that prevents the progression of prostate cancer.

Modulation of YY1 and p53 expression by transforming growth factor-β3 in prostate cell lines

Transforming growth factor-β (TGF-β) is the prototype of a family of secreted polypeptide growth factors. These cytokines play very important roles during development, as well as in normal physiological and disease processes, by regulating a wide array of cellular processes, such as cell growth, differentiation, migration, apoptosis, and extracellular matrix production. TGF-β utilizes a multitude of intracellular signalling pathways in addition to Smads with actions that are dependent on circumstances, including dose, target cell type, and context. The aims of this research were (i) to verify the effects of dose-dependent TGF-β3 treatment on YY1 and p53 expression, in BPH-1 cell line, human benign prostate hyperplasia, and two prostate cancer cell lines, LNCaP, which is androgen-sensitive, and DU-145, which is androgen-non responsive, (ii) establish a correlation between p53 and YY1 and (iii) determine the expression of a number of important intracellular signalling pathways in TGF-β3-treated prostate cell lines. The expression of YY1, p53, PI3K, AKT, pAKT, PTEN, Bcl-2, Bax, and iNOS was evaluated through Western blot analysis on BPH-1, LNCaP, and DU-145 cultures treated with 10 and 50 ng/ml of TGF-β3 for 24 h. The production of nitric oxide (NO) was determined by Griess reagent and cell viability through MTT assay. The results of this research demonstrated profound differences in the responses of the BPH-1, LNCaP, and DU-145 cell lines to TGF-β3 stimulation. We believe that the findings could be important because of the clinical relevance that they may assume and the therapeutic implications for TGF-β treatment of prostate cancer.

Synthesis and biological evaluation of thio-benzodiazepines as novel small molecule inhibitors of the p53-MDM2 protein-protein interaction

A series of thio-benzodiazepine p53-MDM2 inhibitors were designed and synthesized based on the principle of bioisosterism. Most of the thio-benzodiazepines had nanomolar to micromolar affinity toward MDM2. Particularly, compounds 8a (K(i) = 0.52μM) and 8f (K(i) = 0.32 μM) showed binding activity comparable to the positive drug nutlin-3a (K(i) = 0.23 μM). Meanwhile, compound 8j exhibited excellent antitumor activity against the U-2 OS human osteosarcoma cell line with an IC(50) value of 1.06 μM, which was about 23 times higher than that of nutlin-3a. The docking model also successfully predicted that this class of compounds mimicked three p53 critical residues binding to MDM2. The thio-benzodiazepines represent a promising class of non-peptide inhibitors of the p53-MDM2 interaction.

Multifactorial origins of heart and gut defects in nipbl-deficient zebrafish, a model of Cornelia de Lange Syndrome

Cornelia de Lange Syndrome (CdLS) is the founding member of a class of multi-organ system birth defect syndromes termed cohesinopathies, named for the chromatin-associated protein complex cohesin, which mediates sister chromatid cohesion. Most cases of CdLS are caused by haploinsufficiency for Nipped-B-like (Nipbl), a highly conserved protein that facilitates cohesin loading. Consistent with recent evidence implicating cohesin and Nipbl in transcriptional regulation, both CdLS cell lines and tissues of Nipbl-deficient mice show changes in the expression of hundreds of genes. Nearly all such changes are modest, however--usually less than 1.5-fold--raising the intriguing possibility that, in CdLS, severe developmental defects result from the collective action of many otherwise innocuous perturbations. As a step toward testing this hypothesis, we developed a model of nipbl-deficiency in zebrafish, an organism in which we can quantitatively investigate the combinatorial effects of gene expression changes. After characterizing the structure and embryonic expression of the two zebrafish nipbl genes, we showed that morpholino knockdown of these genes produces a spectrum of specific heart and gut/visceral organ defects with similarities to those in CdLS. Analysis of nipbl morphants further revealed that, as early as gastrulation, expression of genes involved in endodermal differentiation (sox32, sox17, foxa2, and gata5) and left-right patterning (spaw, lefty2, and dnah9) is altered. Experimental manipulation of the levels of several such genes--using RNA injection or morpholino knockdown--implicated both additive and synergistic interactions in causing observed developmental defects. These findings support the view that birth defects in CdLS arise from collective effects of quantitative changes in gene expression. Interestingly, both the phenotypes and gene expression changes in nipbl morphants differed from those in mutants or morphants for genes encoding cohesin subunits, suggesting that the transcriptional functions of Nipbl cannot be ascribed simply to its role in cohesin loading.

Panhistone deacetylase inhibitors inhibit proinflammatory signaling pathways to ameliorate interleukin-18-induced cardiac hypertrophy

We investigated the genome-wide consequences of pan-histone deacetylase inhibitors (HDACIs) trichostatin A (TSA) and m-carboxycinnamic acid bis-hydroxamide (CBHA) in the hearts of BALB/c mice eliciting hypertrophy in response to interleukin-18 (IL-18). Both TSA and CBHA profoundly altered cardiac chromatin structure that occurred concomitantly with normalization of IL-18-induced gene expression and amelioration of cardiac hypertrophy. The hearts of mice exposed to IL-18+/-TSA or CBHA elicited distinct gene expression profiles. Of 184 genes that were differentially regulated by IL-18 and TSA, 33 were regulated in an opposite manner. The hearts of mice treated with IL-18 and/or CBHA elicited 147 differentially expressed genes (DEGs), a third of which were oppositely regulated by IL-18 and CBHA. Ingenuity Pathways and Kyoto Encyclopedia of Genes and Genomes analyses of DEGs showed that IL-18 impinged on TNF-α- and IFNγ-specific gene networks relegated to controlling immunity and inflammation, cardiac metabolism and energetics, and cell proliferation and apoptosis. These TNF-α- and IFNγ-specific gene networks, extensively connected with PI3K, MAPK, and NF-κB signaling pathways, were oppositely regulated by IL-18 and pan-HDACIs. Evidently, both TSA and CBHA caused a two- to fourfold induction of phosphatase and tensin homolog expression to counteract IL-18-induced proinflammatory signaling and cardiac hypertrophy.

The structure-based design of Mdm2/Mdmx-p53 inhibitors gets serious

The p53 protein is the cell's principal bastion of defense against tumor-associated DNA damage. Commonly referred as a "guardian of the genome", p53 is responsible for determining the fate of the cell when the integrity of its genome is damaged. The development of tumors requires breaching this defense line. All known tumor cells either mutate the p53 gene, or in a similar number of cases, use internal cell p53 modulators, Mdm2 and Mdmx proteins, to disable its function. The release of functional p53 from the inhibition by Mdm2 and Mdmx should in principle provide an efficient, nongenotoxic means of cancer therapy. In recent years substantial progress has been made in developing novel p53-activating molecules thanks to several reported crystal structures of Mdm2/x in complex with p53-mimicking peptides and nonpeptidic drug candidates. Understanding the structural attributes of ligand binding holds the key to developing novel, highly effective, and selective drug candidates. Two low-molecular-weight compounds have just recently progressed into early clinical studies.

Restoration of DNA-binding and growth-suppressive activity of mutant forms of p53 via a PCAF-mediated acetylation pathway

Tumor-derived mutant forms of p53 compromise its DNA binding, transcriptional, and growth regulatory activity in a manner that is dependent upon the cell-type and the type of mutation. Given the high frequency of p53 mutations in human tumors, reactivation of the p53 pathway has been widely proposed as beneficial for cancer therapy. In support of this possibility p53 mutants possess a certain degree of conformational flexibility that allows for re-induction of function by a number of structurally different artificial compounds or by short peptides. This raises the question of whether physiological pathways for p53 mutant reactivation also exist and can be exploited therapeutically. The activity of wild-type p53 is modulated by various acetyl-transferases and deacetylases, but whether acetylation influences signaling by p53 mutant is still unknown. Here, we show that the PCAF acetyl-transferase is down-regulated in tumors harboring p53 mutants, where its re-expression leads to p53 acetylation and to cell death. Furthermore, acetylation restores the DNA-binding ability of p53 mutants in vitro and expression of PCAF, or treatment with deacetylase inhibitors, promotes their binding to p53-regulated promoters and transcriptional activity in vivo. These data suggest that PCAF-mediated acetylation rescues activity of at least a set of p53 mutations. Therefore, we propose that dis-regulation of PCAF activity is a pre-requisite for p53 mutant loss of function and for the oncogenic potential acquired by neoplastic cells expressing these proteins. Our findings offer a new rationale for therapeutic targeting of PCAF activity in tumors harboring oncogenic versions of p53.