p53 family members in cancer diagnosis and treatment

MDM2: current research status and prospects of tumor treatment

Mousedouble minute 2 (MDM2) is one of the molecules activated by p53 and plays an important role in the regulation of p53. MDM2 is generally believed to function as a negative regulator of p53 by facilitating its ubiquitination and subsequent degradation. Consequently, blocked p53 activity often fails in damaged cells to undergo cell cycle arrest or apoptosis. Given that around 50% of human cancers involve the inactivation of p53 through genetic mutations, and directly targeting p53 through drug development has limited feasibility, targeting molecular regulation related to p53 has great potential and has become a research hotspot. For example, developing drugs that target the interaction between p53 and MDM2. Such drugs aim to reactivate p53 by targeting either MDM2 binding or p53 phosphorylation. Researchers have identified various compounds that can serve as inhibitors, either by directly binding to MDM2 or by modifying p53 through phosphorylation. Furthermore, a significant correlation exists between the expression of MDM2 in tumors and the effectiveness of immunotherapy, predominantly in the context of immune checkpoint inhibition. This review presents a comprehensive overview of the molecular characteristics of MDM2 and the current state of research on MDM2-targeting inhibitors. It includes a review of the impact of MDM2 targeting on the efficacy of immunotherapy, providing guidance and direction for the development of drugs targeting the p53-MDM2 interaction and optimization of immunotherapy.

Interaction mechanisms between autophagy and ferroptosis: Potential role in colorectal cancer

Colorectal cancer (CRC) is a common malignancy that has the second highest incidence and mortality rate. Although there are many personalized treatment options for CRC, the therapeutic effects are ultimately limited by drug resistance. Studies have aimed to block the initiation and progression of CRC by inducing cell death to overcome this obstacle. Substantial evidence has indicated that both autophagy and ferroptosis play important regulatory roles in CRC. Autophagy, a lysosome-dependent process by which cellular proteins and organelles are degraded, is the basic mechanism for maintaining cell homeostasis. The duality and complexity of autophagy in cancer therapy is a hot topic of discussion. Ferroptosis, a regulated cell death pathway, is associated with iron accumulation-induced lipid peroxidation. The activation of ferroptosis can suppress CRC proliferation, invasion and drug resistance. Furthermore, recent studies have suggested an interaction between autophagy and ferroptosis. Autophagy can selectively degrade certain cellular contents to provide raw materials for ferroptosis, ultimately achieving antitumor and anti-drug resistance. Therefore, exploring the interaction between autophagy and ferroptosis could reveal novel ideas for the treatment of CRC. In this review, we describe the mechanisms of autophagy and ferroptosis, focusing on their roles in CRC and the crosstalk between them.

Morusin shows potent antitumor activity for melanoma through apoptosis induction and proliferation inhibition

BACKGROUND

The discovery of new anti-melanoma drugs with low side effect is urgently required in the clinic. Recent studies showed that morusin, a flavonoid compound isolated from the root bark of Morus Alba, has the potential to treat multiple types of cancers, including breast cancer, gastric cancer, and prostate cancer. However, the anti-cancer effect of morusin on melanoma cells has not been investigated.

METHODS

We analyzed the effects of morusin on the proliferation, cell cycle, apoptosis, cell migration and invasion ability of melanoma cells A375 and MV3, and further explored the effects of morusin on tumor formation of melanoma cell. Finally, the effects of morusin on the proliferation, cycle, apoptosis, migration and invasion of A375 cells after knockdown of p53 were detected.

RESULTS

Morusin effectively inhibits the proliferation of melanoma cells and induces cell cycle arrest in the G2/M phase. Consistently, CyclinB1 and CDK1 that involved in the G2/M phase transition were down-regulated upon morusin treatment, which may be caused by the up-regulation of p53 and p21. In addition, morusin induces cell apoptosis and inhibits migration of melanoma cells, which correlated with the changes in the expression of the associated molecules including PARP, Caspase3, E-Cadherin and Vimentin. Moreover, morusin inhibits tumor growth in vivo with little side effect on the tumor-burden mice. Finally, p53 knockdown partially reversed morusin-mediated cell proliferation inhibition, cell cycle arrest, apoptosis, and metastasis.

CONCLUSION

Collectively, our study expanded the spectrum of the anti-cancer activity of morusin and guaranteed the clinical use of the drug for melanoma treatment.

Z-Guggulsterone Induces Cell Cycle Arrest and Apoptosis by Targeting the p53/CCNB1/PLK1 Pathway in Triple-Negative Breast Cancer

Myrrh is the dried resin of Commiphora Myrrh Engl., which exerts anticancer properties. However, its effects and molecular mechanisms in triple-negative breast cancer (TNBC) remain unclear. In this study, we used network pharmacology to screen Z-Guggulsterone (Z-GS) as a characteristic active component of myrrh. Cell Counting Kit-8 proliferation assays showed that Z-GS inhibited proliferation of the TNBC cell lines MDA-MB-468 and BT-549. Transwell assays also showed that Z-GS inhibited TNBC migration and invasion phenotypes. Our network pharmacology combined with RNA-sequencing analyses showed that Z-GS affected cell cycle and apoptosis processes in TNBC cells, mainly via p53 signaling, to regulate key CCNB1 (cyclin B1), PLK1 (polo-like kinase 1), and p53 targets. Flow cytometry revealed that Z-GS arrested the cell cycle at the G2/M phase and increased apoptosis in TNBC cells. Western blotting and quantitative real-time polymerase chain reaction studies confirmed that Z-GS functioned via the p53-mediated downregulation of CCNB1 and PLK1 expression. In vivo studies showed that Z-GS effectively inhibited TNBC progression. Collectively, Z-GS exhibited potential anti-TNBC activity and may functions via the p53/CCNB1/PLK1 pathway.

Deciphering the Role of p53 and TAp73 in Neuroblastoma: From Pathogenesis to Treatment

Neuroblastoma (NB) is an embryonic cancer that develops from neural crest stem cells, being one of the most common malignancies in children. The clinical manifestation of this disease is highly variable, ranging from spontaneous regression to increased aggressiveness, which makes it a major therapeutic challenge in pediatric oncology. The p53 family proteins p53 and TAp73 play a key role in protecting cells against genomic instability and malignant transformation. However, in NB, their activities are commonly inhibited by interacting proteins such as murine double minute (MDM)2 and MDMX, mutant p53, ΔNp73, Itch, and Aurora kinase A. The interplay between the p53/TAp73 pathway and N-MYC, a known biomarker of poor prognosis and drug resistance in NB, also proves to be decisive in the pathogenesis of this tumor. More recently, a strong crosstalk between microRNAs (miRNAs) and p53/TAp73 has been established, which has been the focused of great attention because of its potential for developing new therapeutic strategies. Collectively, this review provides an updated overview about the critical role of the p53/TAp73 pathway in the pathogenesis of NB, highlighting encouraging clues for the advance of alternative NB targeted therapies.

Ovarian tumor deubiquitinase 6A regulates cell proliferation via deubiquitination of nucleolin and caspase‑7

Most proteins maintain protein homeostasis via post‑translational modifications, including the ubiquitin‑proteasome system. Deubiquitinating enzymes (DUBs) have essential intercellular roles, such as responses to DNA damage, proteolysis and apoptosis. Therefore, it is important to understand DUB‑related diseases to identify DUBs that target abnormally regulated proteins in cells. Ovarian tumor deubiquitinase 6A (OTUD6A) was previously reported as a downregulated DUB in HCT116 cells with p53 knockdown. Therefore, it was expected that the relationship between OTUD6A and p53 would affect cell proliferation. In the present study, putative substrates of OTUD6A related to the p53 signaling pathway were identified. Application of liquid chromatography‑tandem mass spectrometry and proteomic analysis led to the identification of nucleolin (known to bind p53) as a binding protein. In addition, immunoprecipitation studies determined that caspase‑7, an apoptotic protein, is associated with p53 signaling and is regulated by OTUD6A. It was further identified that OTUD6A regulates the protein stability of nucleolin, but not caspase‑7. It was also demonstrated that OTUD6A acts as a respective DUB through the deubiquitination of K48‑linked polyubiquitin chain of nucleolin and the K63‑linked polyubiquitin chain of caspase‑7. Furthermore, overexpression of OTUD6A induced cell proliferation via enhancing cell cycle progression of MCF7 cells. Taken together, OTUD6A may be proposed as a target for anticancer therapy.

Identifying the Effect of Ursolic Acid Against Triple-Negative Breast Cancer: Coupling Network Pharmacology With Experiments Verification

Triple negative breast cancer (TNBC) is a subtype of breast cancer with complex heterogeneity, high invasiveness, and long-term poor prognosis. With the development of molecular pathology and molecular genetics, the gene map of TNBC with distinctive biological characteristics has been outlined more clearly. Natural plant extracts such as paclitaxel, vinblastine, colchicine etc., have occupied an important position in the treatment of hormone-independent breast cancer. Ursolic acid (UA), a triterpenoid acid compound derived from apple, pear, loquat leaves, etc., has been reported to be effective in a variety of cancer treatments, but there are few reports on the treatment of TNBC. This study performed comprehensive bioinformatics analysis and in vitro experiments to identify the effect of UA on TNBC treatment and its potential molecular mechanism. Our results showed that UA could not only reduce the proliferation, migration, and invasion in MDA-MB-231 and MDA-MB-468 cell lines with a dose-dependent manner but also induce cell cycle arrest and apoptosis. Meanwhile, we collected the gene expression data GSE45827 and GSE65194 from GEO for comparison between TNBC and normal cell type and obtained 724 DEGs. Subsequently, PLK1 and CCNB1 related to TNBC were screened as the key targets via topological analysis and molecular docking, and gene set enrichment analysis identified the key pathway as the p53 signaling pathway. In addition, quantitative real-time PCR and western blot verified the key genes were PLK1 and CCNB1. In vivo and in vitro experiments showed that UA could inhibit the growth of TNBC cells, and down-regulate the protein expression levels of PLK1 and CCNB1 by mediating p53 signaling pathway. These findings provide strong evidence for UA intervention in TNBC via multi-target therapy.

Δ133p53β isoform pro-invasive activity is regulated through an aggregation-dependent mechanism in cancer cells

The p53 isoform, Δ133p53β, is critical in promoting cancer. Here we report that Δ133p53β activity is regulated through an aggregation-dependent mechanism. Δ133p53β aggregates were observed in cancer cells and tumour biopsies. The Δ133p53β aggregation depends on association with interacting partners including p63 family members or the CCT chaperone complex. Depletion of the CCT complex promotes accumulation of Δ133p53β aggregates and loss of Δ133p53β dependent cancer cell invasion. In contrast, association with p63 family members recruits Δ133p53β from aggregates increasing its intracellular mobility. Our study reveals novel mechanisms of cancer progression for p53 isoforms which are regulated through sequestration in aggregates and recruitment upon association with specific partners like p63 isoforms or CCT chaperone complex, that critically influence cancer cell features like EMT, migration and invasion.

Identified a disintegrin and metalloproteinase with thrombospondin motifs 6 serve as a novel gastric cancer prognostic biomarker by bioinformatics analysis

Objective: We aimed to explore the prognostic value of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) genes in gastric cancer (GC). Methods: The RNA-sequencing (RNA-seq) expression data for 351 GC patients and other relevant clinical data were acquired from The Cancer Genome Atlas (TCGA). Survival analysis and a genome-wide gene set enrichment analysis (GSEA) were performed to define the underlying molecular value of the ADAMTS genes in GC development. Besides, qRT-PCR and immunohistochemistry were all employed to validate the relationship between the expression of these genes and GC patient prognosis. Results: The Log rank test with both Cox regression and Kaplan–Meier survival analyses showed that ADAMTS6 expression profile correlated with the GC patients clinical outcome. Patients with a high expression of ADAMTS6 were associated with poor overall survival (OS). Comprehensive survival analysis of the ADAMTS genes suggests that ADAMTS6 might be an independent predictive factor for the OS in patients with GC. Besides, GSEA demonstrated that ADAMTS6 might be involved in multiple biological processes and pathways, such as the vascular endothelial growth factor A (VEGFA), kirsten rat sarcoma viral oncogene (KRAS), tumor protein P53, c-Jun N-terminal kinase (JNK), cadherin (CDH1) or tumor necrosis factor (TNF) pathways. It was also confirmed by immunohistochemistry and qRT-PCR that ADAMTS6 is highly expressed in GC, which may be related to the prognosis of GC patients. Conclusion: In summary, our study demonstrated that ADAMTS6 gene could be used as a potential molecular marker for GC prognosis.

Cellular Mechanism of Gene Mutations and Potential Therapeutic Targets in Ovarian Cancer

Ovarian cancer is a common and complex malignancy with poor prognostic outcome. Most women with ovarian cancer are diagnosed with advanced stage disease due to a lack of effective detection strategies in the early stage. Traditional treatment with cytoreductive surgery and platinum-based combination chemotherapy has not significantly improved prognosis and 5-year survival rates are still extremely poor. Therefore, novel treatment strategies are needed to improve the treatment of ovarian cancer patients. Recent advances of next generation sequencing technologies have both confirmed previous known mutated genes and discovered novel candidate genes in ovarian cancer. In this review, we illustrate recent advances in identifying ovarian cancer gene mutations, including those of TP53, BRCA1/2, PIK3CA, and KRAS genes. In addition, we discuss advances in targeting therapies for ovarian cancer based on these mutated genes in ovarian cancer. Further, we associate between detection of mutation genes by liquid biopsy and the potential early diagnostic value in ovarian cancer.

Intronic TP53 Polymorphisms Are Associated with Increased Δ133TP53 Transcript, Immune Infiltration and Cancer Risk

We investigated the influence of selected TP53 SNPs in exon 4 and intron 4 on cancer risk, clinicopathological features and expression of TP53 isoforms. The intron 4 SNPs were significantly over-represented in cohorts of mixed cancers compared to three ethnically matched controls, suggesting they confer increased cancer risk. Further analysis showed that heterozygosity at rs1042522(GC) and either of the two intronic SNPs rs9895829(TC) and rs2909430(AG) confer a 2.34-5.35-fold greater risk of developing cancer. These SNP combinations were found to be associated with shorter patient survival for glioblastoma and prostate cancer. Additionally, these SNPs were associated with tumor-promoting inflammation as evidenced by high levels of infiltrating immune cells and expression of the Δ133TP53 and TP53β transcripts. We propose that these SNP combinations allow increased expression of the Δ133p53 isoforms to promote the recruitment of immune cells that create an immunosuppressive environment leading to cancer progression.

Revisiting cancer hallmarks: insights from the interplay between oxidative stress and non-coding RNAs

Cancer is one of the most common disease worldwide, with complex changes and certain traits which have been described as “The Hallmarks of Cancer.” Despite increasing studies on in-depth investigation of these hallmarks, the molecular mechanisms associated with tumorigenesis have still not yet been fully defined. Recently, accumulating evidence supports the observation that microRNAs and long noncoding RNAs (lncRNAs), two main classes of noncoding RNAs (ncRNAs), regulate most cancer hallmarks through their binding with DNA, RNA or proteins, or encoding small peptides. Reactive oxygen species (ROS), the byproducts generated during metabolic processes, are known to regulate every step of tumorigenesis by acting as second messengers in cancer cells. The disturbance in ROS homeostasis leads to a specific pathological state termed “oxidative stress”, which plays essential roles in regulation of cancer progression. In addition, the interplay between oxidative stress and ncRNAs is found to regulate the expression of multiple genes and the activation of several signaling pathways involved in cancer hallmarks, revealing a potential mechanistic relationship involving ncRNAs, oxidative stress and cancer. In this review, we provide evidence that shows the essential role of ncRNAs and the interplay between oxidative stress and ncRNAs in regulating cancer hallmarks, which may expand our understanding of ncRNAs in the cancer development from the new perspective.

Role of tumor suppressor molecules in genomic perturbations and damaged DNA repair involved in the pathogenesis of cancer and neurodegeneration (Review)

Genomic perturbations due to inaccurate DNA replication, including inappropriate chromosomal segregation often underlie the development of cancer and neurodegenerative diseases. The incidence of these two diseases increases with age and exhibits an inverse association. Therefore, elderly subjects with cancer exhibit a reduced risk of a neurodegenerative disease, and vice versa. Both of these diseases are associated with aging and share several risk factors. Cells have multiple mechanisms to repair DNA damage and inaccurate replication. Previous studies have demonstrated that tumor suppressor proteins serve a critical role in the DNA damage response, which may result in genomic instability and thus induction of cellular apoptosis. Tumor suppressor genes, such as phosphatase and tensin homologue deleted on chromosome 10 (PTEN), breast cancer susceptibility gene 1 (BRCA1) and TP53 reduce genomic susceptibility to cancer by repairing the damaged DNA. In addition, these genes work cooperatively to ensure the inhibition of the development of several types of cancer. PTEN, BRCA1 and TP53 have been recognized as the most frequently deleted and/or mutated genes in various types of human cancer. Recently, tumor suppressor genes have also been shown to be involved in the development of neurodegenerative diseases. The present review summarizes the recent findings of the functions of these tumor suppressors that are associated with genomic stability, and are involved in carcinogenic and neurodegenerative cell signaling. A summary is presented regarding the interactions of these tumor suppressors with their partners which results in transduction of downstream signals. The implications of these functions for cancer and neurodegenerative disease-associated biology are also highlighted.

Development of Triptolide Self-Microemulsifying Drug Delivery System and Its Anti-tumor Effect on Gastric Cancer Xenografts

Purpose: To develop a triptolide (TP) self-microemulsifying drug delivery system and to investigate its anti-tumor effect on human gastric cancer line MGC80-3 xenografts in nude mice.

Methods: The medium chain triglyceride (MCT) was selected as oil phase; polyoxyethylene castor oil (EL) was selected as surfactant, and PEG-400 was selected as cosurfactant. The mass ratio of each phase was optimized by central composite design and response surface methodology to prepare TP-SMEDDS (self-microemulsifying drug delivery system). The quality of TP-SMEDDS was evaluated, and its inhibitory effect on tumor growth investigated in nude mice transplanted with MGC80-3 cells.

Results: The final prescription process was defined as follows: MCT mass ratio: 25.3%; EL mass ratio: 49.6%; PEG-400 mass ratio: 25.1%. The prepared TP-SMEDDS was a transparent liquid with a clear appearance (the theoretical particle size: 31.168 nm). On transmission electron microscopy, the microemulsion particles were spherical in size and uniformly distributed without adhesions. The in vitro release experiment showed complete release of the prepared TP-SMEDDS in PBS solution in 6 h. In vivo antitumor activity showed its inhibitory effect in the xenograft model.

Conclusion: The self-microemulsifying delivery system improved the oral bioavailability and the in vivo antitumor effect of TP.

The role of p53 isoforms' expression and p53 mutation status in renal cell cancer prognosis

OBJECTIVES

To analyze p53 mutations and gene expression of p53, ∆40p53, and ∆133p53 isoforms in renal cell cancer (RCC) tissues and normal adjacent tissue (NAT) and to associate them to clinical features and outcome.

PATIENTS AND METHODS

Forty-one randomly selected patients, with primary, previously untreated RCC, with complete clinicopathohistological data were analyzed. NAT samples were available for 37 cases. Expression of p53, ∆40p53 and ∆133p53 was determined using RT-qPCR. A functional yeast-based assay was performed to analyze p53 mutations.

RESULTS

More than half (56.1%) of patients harbored functional p53 mutations, and they were significantly younger than those with wild type (WT) p53 (P = 0.032). Expression of p53, ∆40p53, and ∆133p53 was upregulated in mutant (MT) p53 RCC compared to WT p53 RCC tissues. However, there was no difference in expression of these isoforms between MT p53 RCC tissues and NAT. Expression of ∆133p53 was significantly downregulated in WT p53 tissues compared to NAT (P = 0.006). Patients that harbored functional p53 mutation had better overall survival (hazard ratio 4.32, 95% confidence interval 1.46-18.82, P = 0.006). Multivariate analysis demonstrated that tumor stage and p53 mutation might be used as independent prognostic marker for overall survival in RCC patients.

CONCLUSIONS

Our findings support the specific events in the carcinogenesis of RCC. p53 isoforms can be differentially expressed depending on p53 mutational status.

PLAGL1 gene function during hepatoma cells proliferation

Hepatocellular carcinoma develops as a multistep process, in which cell cycle deregulation is a central feature, resulting in unscheduled proliferation. The PLAGL1 gene encodes a homonym zinc finger protein that is involved in cell-proliferation control. We determined the genomic profile and the transcription and expression level of PLAGL1, simultaneously with that of its molecular partners p53, PPARγ and p21, in cell-lines derived from patients with liver cancer, during in vitro cell growth. Our investigations revealed that genomic and epigenetic changes of PLAGL1 are also present in hepatoma cell-lines. Transcription of PLAGL1 in tumor cells is significantly lower than in normal fibroblasts, but no significant differences in terms of protein expression were detected between these two cell-types, indicating that there is not a direct relationship between the gene transcriptional activity and protein expression. RT-PCR analyses on normal fibroblasts, used as control, also showed that PLAGL1 and p53 genes transcription occurs as an apparent orchestrated process during normal cells proliferation, which gets disturbed in cancer cells. Furthermore, abnormal trafficking of the PLAGL1 protein may occur in hepatocarcinogenesis.

Elevation of the TP53 isoform Δ133p53β in glioblastomas: an alternative to mutant p53 in promoting tumor development

As tumor protein 53 (p53) isoforms have tumor‐promoting, migration, and inflammatory properties, this study investigated whether p53 isoforms contributed to glioblastoma progression. The expression levels of full‐length TP53α (TAp53α) and six TP53 isoforms were quantitated by RT‐qPCR in 89 glioblastomas and correlated with TP53 mutation status, tumor‐associated macrophage content, and various immune cell markers. Elevated levels of Δ133p53β mRNA characterised glioblastomas with increased CD163‐positive macrophages and wild‐type TP53. In situ‐based analyses found Δ133p53β expression localised to malignant cells in areas with increased hypoxia, and in cells with the monocyte chemoattractant protein C‐C motif chemokine ligand 2 (CCL2) expressed. Tumors with increased Δ133p53β had increased numbers of cells positive for macrophage colony‐stimulating factor 1 receptor (CSF1R) and programmed death ligand 1 (PDL1). In addition, cells expressing a murine ‘mimic’ of Δ133p53 (Δ122p53) were resistant to temozolomide treatment and oxidative stress. Our findings suggest that elevated Δ133p53β is an alternative pathway to TP53 mutation in glioblastoma that aids tumor progression by promoting an immunosuppressive and chemoresistant environment. Adding Δ133p53β to a TP53 signature along with TP53 mutation status will better predict treatment resistance in glioblastoma. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Effects of zerumbone on proliferation and apoptosis of esophageal cancer cells and on P53 and Bcl-2 expression levels

The effects of zerumbone on the proliferation and apoptosis of esophagus cancer cells and on the P53 and Bcl-2 expression levels were studied. The esophagus cancer EC-109 cells were cultured and inoculated. The effect of zerumbone on proliferation of EC-109 cells was detected via the Cell Counting Kit-8 (CCK-8) method. Cell apoptosis was detected via TdT-mediated dUTP nick end-labeling (TUNEL) staining. Moreover, the mRNA expression levels of P53 and Bcl-2 were detected via reverse transcription-polymerase chain reaction (RT-PCR), and the protein expression levels of P53 and Bcl-2 were evaluated via western blotting. CCK-8 detection results showed that compared with control group, zerumbone in different concentrations could inhibit the activity of EC-109, and the proliferation inhibition rate was significantly increased in a concentration-dependent manner with the increase of concentration. TUNEL staining showed that cell apoptosis gradually occurred in administration group, and the number of apoptotic cells was increased in a concentration-dependent manner with the increase of concentration. RT-PCR detection results showed that the mRNA expression level of P53 in administration group was significantly increased compared with that in control group, but that of Bcl-2 was significantly decreased. Western blotting showed that the protein expression level of Bcl-2 in administration group in different concentrations was significantly increased with the increase of zerumbone concentration, but that of Bcl-2 was significantly decreased in a concentration-dependent manner. Zerumbone can inhibit the proliferation and induce apoptosis of esophageal cancer EC-109 cells, and its induction of apoptosis may be realized through upregulating the mRNA expression of P53 and downregulating the mRNA expression of Bcl-2, and upregulating the protein expression of P53 and downregulating the protein expression of Bcl-2.

A mouse model of the Δ133p53 isoform: roles in cancer progression and inflammation

This review paper outlines studies on the Δ122p53 mouse, a model of the human Δ133p53 isoform, together with studies in other model organisms, cell culture, and where available, clinical investigations. In general, these studies imply that, in contrast to the canonical p53 tumor suppressor, Δ133p53 family members have oncogenic capability. Δ122p53 is multi-functional, conferring survival and proliferative advantages on cells, promoting invasion, metastasis and vascularization, as does Δ133p53. Cancers with high levels of Δ133p53 often have poor prognosis. Δ122p53 mediates its effects through the JAK-STAT and RhoA-ROCK signaling pathways. We propose that Δ133p53 isoforms have evolved as inflammatory signaling molecules to deal with the consequent tissue damage of p53 activation. However, if sustained expression of the isoforms occur, pathologies may result.

Mandarin fish p53: Genomic structure, alternatively spliced variant and its mRNA expression after virus challenge

A number of size variants of the p53 protein have been described in mammal, but little is known about alternative splicing of p53 expression and function in the fish. In our previous study, the immune defense and antiviral responses of p53 had been determined in mandarin fish (Siniperca chuatsi). However, the role of its splicing variants remains unknown. In the present study, the organization of mandarin fish p53 (Sc-p53) genome sequence was determined and a novel splice variant was characterized. The Sc-p53 genomic sequence was composed of 5543 bp, containing 11 exons and 10 introns, which was similar to other species. Then, a 1106 bp full-length cDNA of a novel splice variant p53 from mandarin fish (designed as Sc-p53I6) was cloned and characterized. Quantitative real-time PCR assays revealed that Sc-p53I6 was expressed in all tissues examined, and it was most abundant in the gill, hemocyte and hind kidney. Western blotting analysis revealed that Sc-p53I6 protein was abundant in liver, trunk kidney, hind kidney, stomach and heart. In addition, the regulation of Sc-p53I6 gene expression after virus infection was determined and characterized. The results showed twice rise expression pattern of Sc-p53I6 in CPB cells and spleen of mandarin fish in response to infectious kidney and spleen necrosis virus (ISKNV). However, a different expression pattern, once rise, of Sc-p53I6 in response to Siniperca chuatsi rhabdovirus (SCRV) infection was found. The mRNA expression of Sc-p53I6 was significantly up-regulated in CPB at 4 h and spleen of mandarin fish at 12 h post-infection. These results will shed a new light on antiviral response mechanisms of p53 in mandarin fish.

Status quo of p53 in the treatment of tumors

The p53 gene is pivotal for oncogenesis in a combination of mutations in oncogenes and antioncogenes. The ubiquitous loss of the p53 pathway in human cancers has generated considerable interest in developing p53-targeted cancer therapies, but current ideas and approaches targeting p53 are conflicting. Current researches focus on cancer-selective drugs with therapeutic strategies that both activate and inhibit p53. As p53 is ubiquitously lost in human cancers, the strategy of exogenous p53 addition is reasonable. However, p53 acts not equally in all cell types; thus, individualized p53 therapy is the direction of future research. To clarify the controversies on p53 for improvement of future antitumor studies, the review focuses on the available technological protocols, including their advantages and limitations in terms of future therapeutic use of p53 in the management of tumors.

Emodin promotes the arrest of human lymphoma Raji cell proliferation through the UHRF1‑DNMT3A‑∆Np73 pathways

Emodin is an active constituent found in the roots and rhizomes of numerous Chinese medicinal herbs. It exerts antitumor activity against Dalton's lymphoma in vivo, although the detailed mechanisms by which emodin induces apoptosis remains to be elucidated. The present study aimed to analyze the mechanisms underlying the response to emodin treatment. Using lymphoma Raji cells, an emodin‑induced cell proliferating inhibition model was first established, then flow cytometry, western blotting, reverse transcription‑quantitative polymerase chain reaction and luciferase reporter assay were performed. It was found that emodin decreased the percentage of Raji cell viability, induced apoptosis, and increased the activation of caspase 3, caspase 9 and poly (ADP‑ribose) polymerase through the downregulation of ubiquitin‑like protein containing PHD and RING domains 1 (UHRF1). The emodin‑induced downregulation of UHRF1 led to an increase in the level of DNA methyltransferase 3A, which in turn inhibited the activity of p73 promoter 2 and decreased the levels of NH2‑terminally truncated dominant‑negative p73. The treatment of Raji cells with emodin combined with doxorubicin led increased cell death of Raji cells, indicating that emodin may sensitize Raji cells to doxorubicin‑induced apoptosis.

Effect of the p53α gene on the chemosensitivity of the H1299 human lung adenocarcinoma cell line

To investigate the effects of tumor protein p53 (p53 or TP53) α gene on the chemosensitivity of the H1299 human lung adenocarcinoma cell line, the recombinant vector pEGFP-p53α was constructed. The vector pEGFP-p53α was transfected into the cultured p53-null H1299 cells using Lipofectamine 2000. The G418-resistant cells were then selected. The expression of the p53α gene in these cells was examined using reverse transcription-polymerase chain reaction, and TP53 protein expression was examined using western blot analysis and immunocytochemistry. An MTT assay and colony formation assay were used to analyze the response of the transfected cells to cisplatin (CDDP). DAPI staining was used to determine the level of apoptosis of the transfected cells. The transfected H1299 human lung adenocarcinoma cells stably expressed TP53 protein. The MTT assay demonstrated that the 50% inhibitory concentrations for the H1299, H1299/pEGFP-N₁ and H1299/pEGFP-p53α cells were 28, 24 and 18 µmol/l, respectively. The survival rate of H1299/pEGFP-p53α cells was significantly reduced compared with that of H1299 and H1299/pEGFP-N₁ cells (P<0.05). The colony formation assay and DAPI staining identified that the colony formation rate and the number of apoptotic cells of H1299/pEGFP-p53α were significantly reduced, compared with those of the H1299 and H1299/pEGFP-N₁ cells (P<0.05). Therefor, the present study demonstrated that the transfection of H1299 cells with the p53α gene resulted in an increase in sensitivity to CDDP chemotherapy. The combination of CDDP and gene therapy for H1299 lung adenocarcinoma cell line provides an experimental basis for clinical research.

The TP53 intron 6 G13964C polymorphism and risk of thyroid and breast cancer development in the Iranian Azeri population

BACKGROUND

TP53 mutations are the most common genetic alterations in human cancers. There are also several polymorphisms in both exons and introns of TP53 that may influence its anti-tumor functions and increase the risk of cancer development. Associations of the TP53 intron 6 G13964C polymorphism with increased risk of development of several cancers have been investigated in numerous studies, but the results were controversial and conflicting. In this study, we aimed to investigate the probable association of this polymorphism with risk of both thyroid and breast cancers among the Iranian-Azeri population.

MATERIALS AND METHODS

We performed two separate case control studies on associations of the intron 6 polymorphism with two different kinds of cancer. In one case-control study, a total of 75 patients with thyroid carcinoma and 180 controls were analyzed and the other study included 170 patients with breast cancer and 135 healthy women. The intron 6 genotype was determined by RFLP-PCR and the SPSS 16 program was applied for data analysis.

RESULTS

For thyroid cancer, the frequencies of GG genotype were 96.0% in patients and 93.3% in controls. The GC genotype had a frequency of 4.0% in patients and 6.7% in controls. In the study on breast cancer, the frequency of GG and GC genotypes in patients were 95.3% and 4.7%, respectively. In breast related control group, the frequency of GG genotype was 93.3% and the frequency of GC genotype was 6.7%. None of the cases and controls had the CC genotype.

CONCLUSIONS

There was no significant association between the TP53 intron 6 G13964C polymorphism and risk of development of both thyroid and breast cancer in Iranian-Azeri patients.

The p53 isoform Δ133p53β promotes cancer stem cell potential

Cancer stem cells (CSC) are responsible for cancer chemoresistance and metastasis formation. Here we report that Δ133p53β, a TP53 splice variant, enhanced cancer cell stemness in MCF-7 breast cancer cells, while its depletion reduced it. Δ133p53β stimulated the expression of the key pluripotency factors SOX2, OCT3/4, and NANOG. Similarly, in highly metastatic breast cancer cells, aggressiveness was coupled with enhanced CSC potential and Δ133p53β expression. Like in MCF-7 cells, SOX2, OCT3/4, and NANOG expression were positively regulated by Δ133p53β in these cells. Finally, treatment of MCF-7 cells with etoposide, a cytotoxic anti-cancer drug, increased CSC formation and SOX2, OCT3/4, and NANOG expression via Δ133p53, thus potentially increasing the risk of cancer recurrence. Our findings show that Δ133p53β supports CSC potential. Moreover, they indicate that the TP53 gene, which is considered a major tumor suppressor gene, also acts as an oncogene via the Δ133p53β isoform.

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The Δ133p53β isoform promotes stemness of breast cancer cells

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The Δ133p53β isoform regulates SOX2, OCT3/4, and NANOG expression, but not C-MYC

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Etoposide promotes cancer cell stemness through Δ133p53β induction

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Δ133p53β expression, like p53 mutations, promotes cancer cell stemness

Lack of association of intron 3 16 bp polymorphism of TP53 with breast cancer among Iranian-Azeri patients

BACKGROUND

p53 gene is a well-known tumor suppressor gene that has several polymorphisms in both its exons and introns. It has been suggested that intron 3 16 bp duplication polymorphism may affect the gene function resulting in reduction or suppression of p53 anti tumor activity. In most case control studies a duplicated allele has been noticeably more frequent in cases rather than controls but there are also conflicting results. The aim of this study was to assess the association of intron 3 16 bp duplication polymorphism of p53 with breast cancer risk among Iranian-Azeri population. We also analyzed the clinicopathological information of patients as an epidemiological description of breast cancer in the north-west of Iran.

MATERIALS AND METHODS

This case-control study was performed on 221 breast cancer patients and 170 controls. Genomic DNA was extracted from peripheral blood samples and tumor tissues. p53 PIN3 genotype was determined using electrophoresis of PCR products on 8% non-denaturing polyacrylamide gels and silver staining.

RESULTS

In the control and case groups, respectively, 62.9% and 61.1% had no 16 bp insertion (A1A1 genotype), 7.1% and 7.7% had insertion in both p53 alleles (A2A2) and 30% and 31.2% were heterozygous (A1A2). There was no significant difference between genotype frequencies as well as allelic frequencies in two case and control groups.

CONCLUSIONS

According to the result of the present study, the intron 3 16 bp duplication polymorphism of p53 could not be assessed as a marker of risk factor for predisposition to breast cancer in Azeri population. However, a high frequency of A2 allele (22.1%) in our population suggested that intron 3 16 bp duplication polymorphism may be a valuable marker for study in other cancers with well designed large groups.

Association of p53 (-16ins-pro) haplotype with the decreased risk of differentiated thyroid carcinoma in Iranian-Azeri patients

Association of P53 polymorphisms with the increased risk of various cancers has been investigated in numerous studies. However, the results were conflicting and no polymorphism has been determined as a definite risk factor. It is likely that the study of P53 combined genotypes and haplotypes may be more useful than individual polymorphisms. Thus, in this study, we analyzed the associations of intron 3 Ins16bp and exon 4 Arg72Pro polymorphisms, as well as their combined genotypes and haplotypes with the risk of differentiated thyroid carcinoma in Iranian-Azeri patients. This case-control study was performed on 84 Iranian Azeri patients with differentiated thyroid carcinoma and 150 healthy subjects. Intron 3 genotype was determined using PCR products analysis on polyacrylamide gels and AS-PCR was used for genotyping Arg72Pro polymorphism. The javastat online statistics package software and SHEsis program were applied for data analysis. There was no significant difference in genotype frequencies of both two polymorphisms between cases and controls. However, the (-16 ins/-16 ins) (Arg/Pro) genotype combination had a noticeable but not significant association with decreased risk of thyroid cancer development (OR = 0.497 95%CI: 0.209-1.168 P = 0.080) and also the frequency of (-16 ins-Pro) haplotype was significantly higher in controls rather than patients (OR = 0.543 95%CI: 0.326-0.903 P = 0.018). In our study, there was association between (-16 ins-Pro) haplotype with decreased risk of differentiated thyroid carcinoma development in Iranian-Azeri patients.

Direct T cell activation via CD40 ligand generates high avidity CD8+ T cells capable of breaking immunological tolerance for the control of tumors

CD40 and CD40 ligand (CD40L) are costimulatory molecules that play a pivotal role in the proinflammatory immune response. Primarily expressed by activated CD4⁺ T cells, CD40L binds to CD40 on antigen presenting cells (APCs), thereby inducing APC activation. APCs, in turn, prime cytotoxic T lymphocytes (CTLs). Here, two tumor-associated antigen (TAA) animal models, p53-based and GP100-based, were utilized to examine the ability of CD40-CD40L to improve antigen-specific CTL-mediated antitumor immune responses. Although p53 and GP100 are self-antigens that generate low affinity antigen-specific CD8⁺ T cells, studies have shown that their functional avidity can be improved with CD40L-expressing APCs. Therefore, in the current study, we immunized mice with a DNA construct encoding a TAA in conjunction with another construct encoding CD40L via intramuscular injection followed by electroporation. We observed a significant increase in the antigen-specific CTL-mediated immune responses as well as the potent antitumor effects in both models. Antibody depletion experiments demonstrated that CD8⁺ T cells play a crucial role in eliciting antitumor effects in vaccinated mice. Furthermore, we showed that in vitro stimulation with irradiated tumor cells expressing both TAA and CD40L improved the functional avidity of antigen-specific CD8⁺ T cells. Thus, our data show that vaccination with TAA/CD40L DNA can induce potent antitumor effects against TAA-expressing tumors through the generation of better functioning antigen-specific CD8⁺ T cells. Our study serves as an important foundation for future clinical translation.

Dominant effects of Δ40p53 on p53 function and melanoma cell fate

The TP53 gene encodes 12 distinct isoforms, some of which can alter p53 activity in the absence of genomic alteration. Endogenous p53 isoforms have been identified in cancers; however, the function of these isoforms remains unclear. In melanoma, the frequency of TP53 mutations is relatively low compared with other cancers, suggesting that these isoforms may have a larger role in regulating TP53 activity. We hypothesized that p53 function and therefore cell fate might be altered by the presence of Δ40p53, an embryonic isoform missing the first 40 N-terminal amino acids of the full-length protein including the transactivation and Mdm2-binding domains. To test this hypothesis, we transduced tumor and normal cells with a lentivirus encoding Δ40p53. We found that exogenous Δ40p53 caused apoptosis and increased the levels of endogenous, activated p53 in both cancerous and non-cancerous cells, which led to significant levels of cell death, particularly in cancer cells. Activated p53 molecules formed nuclear heterotetramers with Δ40p53 and altered downstream p53 transcription target levels including p53-induced protein with death domain and cyclin-dependent kinase inhibitor, p21. Δ40p53 altered the promoter occupancy of these downstream p53 target genes in such a way that it shifted cell fate toward apoptosis and away from cell cycle arrest. We show that tumor suppression by p53 can occur via an alternate route that relies on its interaction with Δ40p53.

[P53 family proteins provide new insights into lung carcinogenesis and clinical treatment]

P53作为转录因子，其转录激活功能维持了基因组的稳定性，对防止肿瘤的形成起着重要作用，是目前研究得最为广泛、深入的抑癌基因，被称为“基因卫士”。P53家族的成员p63、p73与p53在DNA结合结构域上有高度的同源性，某些p53家族亚型可以与p53-反应基因相结合起着转录激活的作用，另外一些则起着负性调节作用。肺癌是世界上患病率最高的恶性肿瘤之一，p53家族成员在肺癌中的异常表达与肺癌的发生有密切联系，并导致不良的预后及对放疗、化疗的抵抗。对p53家族成员在肺癌致病机制的深入研究可有助于为临床提供合理的化疗方案及靶向治疗策略。本文着重回顾总结p53家族成员在肺癌发生、化疗敏感性以及肺癌靶向治疗中的独特的作用。

p73 expression is associated with cellular chemosensitivity in human non-small cell lung cancer cell lines

p73 is a member of the p53 tumor suppressor protein family and induces apoptosis in tumor cells that lack functional p53. It has been demonstrated that methylation of CpG islands in the promoter and exon 1 region may result in silencing of the p73 gene. The aim of this study was to investigate the correlation between p73 gene expression and chemosensitivity in non-small cell lung cancer (NSCLC) cell lines. The expression of the p73 transcript in six NSCLC cell lines was investigated by reverse transcription-polymerase chain reaction (RT-PCR). The methylation status in these cell lines was determined by methylation-specific PCR (MSP) analysis. An in vitro demethylation assay was conducted using the DNA methyltransferase inhibitor 5-aza-2-deoxycytidine (5-aza-dC). Restored expression of p73 in the human lung squamous cell carcinoma cell line C57, both at the mRNA and protein level, was investigated by RT-PCR and immunohistochemistry, respectively. A colony formation assay was used to measure the surviving fraction of the C57 cell line. Transcript silencing of the p73 gene in the six NSCLC cell lines was observed and related to aberrant methylation. The expression of the p73 transcript and protein in the C57 cell line was restored by 5-aza-dC. The surviving fraction for colony formation in C57 cells pre-treated with 5-aza-dC was 0.059±0.006, which was significantly different from that of the control group (0.12±0.008; P<0.05). Our data demonstrated a significant correlation between expression of p73 and cellular chemosensitivity in NSCLC.

Synergistic role between p53 and JWA: prognostic and predictive biomarkers in gastric cancer

Expression of p53 appears to be correlated to prognosis in patients with malignancy, but its role in gastric carcinoma has remained controversial. Recently we reported that JWA, an ADP-ribosylation-like factor 6 interacting protein 5 (ARL6ip5), was both prognostic for overall survival and predictive for platinum-based treatment of gastric cancer. In this study, we aimed to investigate p53 expression as a prognostic and predictive marker in resectable gastric cancer, alone and in combination with JWA. Expression of p53 was examined in three large patient cohorts (total n = 1155) of gastric cancer. High expression of p53 was significantly correlated with unfavorable clinicopathologic parameters and decreased overall patient survival. Furthermore, patients with high p53 expression in tumors acquired remarkable survival benefit from adjuvant first-line platinum-based-chemotherapy. The synergy between p53 and JWA in predicting patient outcome was demonstrated, while no significantly elevated predictive value concerning chemotherapy was observed. Thus, p53 expression is a potent prognostic and predictive factor for resectable gastric cancer with adjuvant platinum-based chemotherapy. A combined effect of p53 with JWA as efficient prognostic indicators was found for the first time.

Mutant p53: one name, many proteins

There is now strong evidence that mutation not only abrogates p53 tumor-suppressive functions, but in some instances can also endow mutant proteins with novel activities. Such neomorphic p53 proteins are capable of dramatically altering tumor cell behavior, primarily through their interactions with other cellular proteins and regulation of cancer cell transcriptional programs. Different missense mutations in p53 may confer unique activities and thereby offer insight into the mutagenic events that drive tumor progression. Here we review mechanisms by which mutant p53 exerts its cellular effects, with a particular focus on the burgeoning mutant p53 transcriptome, and discuss the biological and clinical consequences of mutant p53 gain of function.

p53 isoform profiling in glioblastoma and injured brain

The tumor suppressor p53 has been found to be the most commonly mutated gene in human cancers; however, the frequency of p53 mutations varies from 10 to 70% across different cancer types. This variability can partly be explained by inactivating mechanisms aside from direct genomic polymorphisms. The p53 gene encodes 12 isoforms, some of which can modulate full-length p53 activity in cancer. In this study, we characterized p53 isoform expression patterns in glioblastoma, gliosis, non-tumor brain and neural progenitor cells by SDS-PAGE, immunoblot, mass spectrometry and reverse transcription-PCR. We found that the most consistently expressed isoform in glioblastoma, Δ40p53, was uniquely expressed in regenerative processes, such as those involving neural progenitor cells and gliosis compared with tumor samples. Isoform profiling of glioblastoma tissues revealed the presence of both Δ40p53 and full-length p53, neither of which were detected in non-tumor cerebral cortex. Upon xenograft propagation of tumors, p53 levels increased. The variability of overall p53 expression and relative levels of isoforms suggest fluctuations in subpopulations of cells with greater or lesser capacity for proliferation, which can change as the tumor evolves under different growth conditions.

Influenza A viruses control expression of proviral human p53 isoforms p53β and Delta133p53α

Previous studies have described the role of p53 isoforms, including p53β and Δ133p53α, in the modulation of the activity of full-length p53, which regulates cell fate. In the context of influenza virus infection, an interplay between influenza viruses and p53 has been described, with p53 being involved in the antiviral response. However, the role of physiological p53 isoforms has never been explored in this context. Here, we demonstrate that p53 isoforms play a role in influenza A virus infection by using silencing and transient expression strategies in human lung epithelial cells. In addition, with the help of a panel of different influenza viruses from different subtypes, we also show that infection differentially regulates the expressions of p53β and Δ133p53α. Altogether, our results highlight the role of p53 isoforms in the viral cycle of influenza A viruses, with p53β and Δ133p53α acting as regulators of viral production in a p53-dependent manner.

p53 in stem cells

p53 is well known as a “guardian of the genome” for differentiated cells, in which it induces cell cycle arrest and cell death after DNA damage and thus contributes to the maintenance of genomic stability. In addition to this tumor suppressor function for differentiated cells, p53 also plays an important role in stem cells. In this cell type, p53 not only ensures genomic integrity after genotoxic insults but also controls their proliferation and differentiation. Additionally, p53 provides an effective barrier for the generation of pluripotent stem cell-like cells from terminally differentiated cells. In this review, we summarize our current knowledge about p53 activities in embryonic, adult and induced pluripotent stem cells.

Biological functions of p53 isoforms through evolution: lessons from animal and cellular models

The TP53 tumour-suppressor gene is expressed as several protein isoforms generated by different mechanisms, including use of alternative promoters, splicing sites and translational initiation sites, that are conserved through evolution and within the TP53 homologues, TP63 and TP73. Although first described in the eighties, the importance of p53 isoforms in regulating the suppressive functions of p53 has only become evident in the last 10 years, by analogy with observations that p63 and p73 isoforms appeared indispensable to fully understand the biological functions of TP63 and TP73. This review summarizes recent advances in the field of 'p53 isoforms', including new data on p63 and p73 isoforms. Details of the alternative mechanisms that produce p53 isoforms and cis- and trans-regulators identified are provided. The main focus is on their biological functions (apoptosis, cell cycle, aging and so on) in cellular and animal models, including mouse, zebrafish and Drosophila. Finally, the deregulation of p53 isoform expression in human cancers is reviewed. Based on these latest results, several developments are expected in the future: the identification of drugs modulating p53 isoform expression; the generation of animal models and the evaluation of the use of p53 isoform as biomarkers in human cancers.

p53 expression predicts dismal outcome for medulloblastoma patients with metastatic disease

Medulloblastoma (MB) is the most common malignant primary brain tumour in childhood. Metastatic disease (M+) at diagnosis is the most important negative prognostic clinical marker and, despite craniospinal irradiation and intensive chemotherapy, it remains one of the leading causes of treatment failure. To date, few clinical and biological data have been evaluated to obtain an additional prognostic profile for these high-risk patients. In this study, 169 patients with metastatic MB registered in the multicentre HIT2000 trial of the German Society of Pediatric Oncology and Haematology (GPOH) have been investigated to determine the importance of p53 protein expression in predicting survival. At a median follow-up of 4.1 years, 159 patients with p53-negative tumours had significantly better four-year event-free survival (EFS) and progression-free survival (PFS) (56 ± 11, 59 ± 4%) than 10 patients with p53-positive tumours (40 ± 16, 40 ± 16%; P = 0.018 for EFS, P = 0.007 for PFS, respectively). Furthermore, four-year overall survival (OS) of children with p53-negative tumours was higher than for children with p53-positive tumours (72 ± 4 vs. 35 ± 18%, P = 0.05). Three of the p53-positive MBs harbored a point mutation in the TP53 gene. p53 protein assessment by immunohistochemistry may be a useful tool for sub-stratification of metastatic high-risk MB patients.

High expression of testes-specific protease 50 is associated with poor prognosis in colorectal carcinoma

Background

Testes-specific protease 50 (TSP50) is normally expressed in testes and abnormally expressed in breast cancer, but whether TSP50 is expressed in colorectal carcinoma (CRC) and its clinical significance is unclear. We aimed to detect TSP50 expression in CRC, correlate it with clinicopathological factors, and assess its potential diagnostic and prognostic value.

Methodology/Principal Findings

TSP50 mRNAs and proteins were detected in 7 CRC cell lines and 8 CRC specimens via RT-PCR and Western blot analysis. Immunohistochemical analysis of TSP50, p53 and carcinoembryonic antigen (CEA) with tissue microarrays composed of 95 CRCs, 20 colorectal adenomas and 20 normal colorectal tissues were carried out and correlated with clinicopathological characteristics and disease-specific survival for CRC patients. There was no significant correlation between the expression levels of TSP50 and p53 (P = 0.751) or CEA (P = 0.663). Abundant expression of TSP50 protein was found in CRCs (68.4%) while it was poorly expressed in colorectal adenomas and normal tissues (P<0.0001). Thus, CRCs can be distinguished from them with high specificity (92.5%) and positive predictive value (PPV, 95.6%). The survival of CRC patients with high TSP50 expression was significantly shorter than that of the patients with low TSP50 expression (P = 0.010), specifically in patients who had early-stage tumors (stage I and II; P = 0.004). Multivariate Cox regression analysis indicated that high TSP50 expression was a statistically significant independent risk factor (hazard ratio  = 2.205, 95% CI = 1.214–4.004, P = 0.009).

Conclusion

Our data demonstrate that TSP50 is a potential effective indicator of poor survival for CRC patients, especially for those with early-stage tumors.

p53-targeted cancer pharmacotherapy: move towards small molecule compounds

OBJECTIVES

For the past three decades of research, p53 has been identified as one of the most targetable molecules for developing anticancer treatments. This tumour suppressor protein is involved in apoptosis, cell cycle arrest and senescence. A wide range of pharmaceutical drugs and radiotherapy treatments activate this protein and rely on p53 signalling for therapeutic outcome. Promising small molecular weight compounds, some of which are undergoing clinical trials, are discussed in this review.

KEY FINDINGS

The spectrum of potential therapeutic approaches trialled for p53 stretch from gene therapy to the more recent development of small molecules capable of activating wild-type p53 or reactivating mutant p53.

SUMMARY

Our ever-growing knowledge leads us to better understand this protein, from its structure and activities to its potential therapeutic application, firstly for cancer and then for other diseases and maybe even for reversal of ageing.

Clinical significance of P53 and Ki67 expression in gastric cancer

AIM: To investigate the correlation of P53 and Ki67 protein expression with the clinicopathological parameters in gastric cancer.

METHODS: A total of 1 107 surgical specimens of gastric cancer were collected from the Fuzhou General Hospital of Nanjing Military Command, The expression of P53 and Ki67 was examined by immunohistochemistry in 775 gastric cancer specimens taken from patients with complete clinical data.

RESULTS: The positive rates of P53 and Ki67 protein expression were 46.84% and 78.97%, respectively. Higher positive rates of P53 and Ki67 protein expression were noted in intestinal-type gastric cancer than in diffuse-type gastric cancer (54.7% vs 38.0%, 86.0% vs 70.0%, both P < 0.05) and in well-differentiated cancer than in poorly-differentiated cancer (54.7 vs 35.4%, 87.0% vs 67.2%, both P < 0.05). A higher positive rate of P53 protein expression was noted in gastroesophageal junction (GEJ) cancer than in gastric cancer (53.7% vs 41.9%, P < 0.05) and in cancer without distant metastasis than in that with distant metastasis (49.0% vs 30.3%, P < 0.05). A higher positive rate of Ki67 protein expression was noted in invasive cancer than in less invasive cancer ( 80.3% vs 60.4%, P < 0.05) and in cancer with lymph node metastasis than in that without lymph node metastasis (81.4% vs 72.6 %, P < 0.05).

CONCLUSION: P53 and Ki67 protein expression might be associated with the development, invasion, and metastasis of gastric cancer, and can be used to evaluate the malignant behavior and prognosis of gastric cancer.

Sequence-dependent cooperative binding of p53 to DNA targets and its relationship to the structural properties of the DNA targets

The prime mechanism by which p53 acts as a tumor suppressor is as a transcription factor regulating the expression of diverse downstream genes. The DNA-binding domain of p53 (p53DBD) interacts with defined DNA sites and is the main target for mutations in human primary tumors. Here, we show that the CWWG motif, found in the center of each consensus p53 half-site, is a key player in p53/DNA interactions. Gel-mobility-shift assays provide a unique opportunity to directly observe the various oligomeric complexes formed between p53DBD and its target sites. We demonstrate that p53DBD binds to p53 consensus sites containing CATG with relatively low cooperativity, as both dimers and tetramers, and with even lower cooperativity to such sites containing spacer sequences. p53DBD binds to sites containing CAAG and CTAG with measurable affinity only when imbedded in two contiguous p53 half-sites and only as tetramers (with very high cooperativity). There are three orders-of-magnitude difference in the cooperativity of interaction between sites differing in their non-contacted step, and further two orders-of-magnitude difference as a function of spacer sequences. By experimentally measuring the global structural properties of these sites, by cyclization kinetics of DNA minicircles, we correlate these differences with the torsional flexibility of the binding sites.

Δ160p53 is a novel N-terminal p53 isoform encoded by Δ133p53 transcript

p53 gene expresses several protein isoforms modulating p53-mediated responses through regulation of gene expression. Here, we identify a novel p53 isoform, Δ160p53, lacking the first 159 residues. By knockdown experiments and site-directed mutagenesis, we show that Δ160p53 is encoded by Δ133p53 transcript using ATG160 as translational initiation site. This hypothesis is supported by endogenous expression of Δ160p53 in U2OS, T47D and K562 cells, the latter ones carrying a premature stop codon that impairs p53 and Δ133p53 protein expression but not the one of Δ160p53. Overall, these results show that the Δ133p53 transcript generates two different p53 isoforms, Δ133p53 and Δ160p53.

Intracellular signaling and hepatocellular carcinoma

Liver cancer is the fifth most common cancer and the third most common cause of cancer related death in the world. The recent development of new techniques for the investigations of global change in the gene expression, signaling pathways and wide genome binding has provided novel information for the mechanisms underlying liver cancer progression. Although these studies identified gene expression signatures in hepatocellular carcinoma, the early steps of the development of hepatocellular carcinomas (HCC) are not well understood. The development of HCC is a multistep process which includes the progressive alterations of gene expression leading to the increased proliferation and to liver cancer. This review summarizes recent progress in the identification of the key steps of the development of HCC with the focus on early events of carcinogenesis and on the role of translational and epigenetic alterations in the development of HCC. Quiescent stage of the liver is supported by several tumor suppressor proteins including p53, Rb and C/EBPα. Studies with chemical models of liver carcinogenesis and with human HCC have shown that the elevation of gankyrin is responsible for the elimination of these three proteins at early steps of carcinogenesis. Later stages of progression of the liver cancer are associated with alterations in many signaling pathways including translation which leads to epigenetic silencing/activation of many genes. Particularly, recent reports suggest a critical role of histone deacetylase 1, HDAC1, in the development of HCC through the interactions with transcription factors such as C/EBP family proteins.