p53, secreted by K-Ras-Snail pathway, is endocytosed by K-Ras-mutated cells; implication of target-specific drug delivery and early diagnostic marker

Regulated secretion of mutant p53 negatively affects T lymphocytes in the tumor microenvironment

Several studies have demonstrated the role of the oncogenic mutant p53 in promoting tumor progression; however, there is limited information on the effects of secreted oncogenic mutant p53 on the tumor microenvironment and tumor immune escape. In this study, we found that secretion of mutant p53, determined by exosome content, is dependent on its N-terminal dileucine motif via its binding to β-adaptin, and inhibited by the CHK2-mediated-Ser 20 phosphorylation. Moreover, we observed that the mutant p53 caused downregulation and dysfunction of CD4+ T lymphocytes in vivo and downregulated the levels and activities of rate-limiting glycolytic enzymes in vitro. Furthermore, inhibition of mutant p53 secretion by knocking down AP1B1 or mutation of dileucine motif could reverse the quantity and function of CD4+ T lymphocytes and restrain the tumor growth. Our study demonstrates that the tumor-derived exosome-mediated secretion of oncogenic mutant p53 inhibits glycolysis to alter the immune microenvironment via functional suppression of CD4+ T cells, which may be the underlying mechanism for tumor immune escape. Therefore, targeting TDE-mediated p53 secretion may serve as a potential therapeutic target for cancer treatment.

Protein detection in blood with single-molecule imaging

The ability to characterize individual biomarker protein molecules in patient blood samples could enable diagnosis of diseases at an earlier stage, when treatment is typically more effective. Single-molecule imaging offers a promising approach to accomplish this goal. However, thus far, single-molecule imaging methods have not been translated into the clinical setting. The detection limit of these methods has been confined to the picomolar (10^-12 M) range, several orders of magnitude higher than the circulating concentrations of biomarker proteins present in many diseases. Here, we describe single-molecule augmented capture (SMAC), a single-molecule imaging technique to quantify and characterize individual protein molecules of interest down to the subfemtomolar (<10^-15 M) range. We demonstrate SMAC in a variety of applications with human blood samples, including the analysis of disease-associated secreted proteins, membrane proteins, and rare intracellular proteins. SMAC opens the door to the application of single-molecule imaging in noninvasive disease profiling.

Aberrant phase separation and cancer

Eukaryotic cells are intracellularly divided into numerous compartments or organelles, which coordinate specific molecules and biological reactions. Membrane-bound organelles are physically separated by lipid bilayers from the surrounding environment. Biomolecular condensates, also referred to membraneless organelles, are micron-scale cellular compartments that lack membranous enclosures but function to concentrate proteins and RNA molecules, and these are involved in diverse processes. Liquid-liquid phase separation (LLPS) driven by multivalent weak macromolecular interactions is a critical principle for the formation of biomolecular condensates, and a multitude of combinations among multivalent interactions may drive liquid-liquid phase transition (LLPT). Dysregulation of LLPS and LLPT leads to aberrant condensate and amyloid formation, which causes many human diseases, including neurodegeneration and cancer. Here, we describe recent findings regarding abnormal forms of biomolecular condensates and aggregation via aberrant LLPS and LLPT of cancer-related proteins in cancer development driven by mutation and fusion of genes. Moreover, we discuss the regulatory mechanisms by which aberrant LLPS and LLPT occur in cancer and the drug candidates targeting these mechanisms. Further understanding of the molecular events regulating how biomolecular condensates and aggregation form in cancer tissue is critical for the development of therapeutic strategies against tumorigenesis.

Urolithin A Inhibits Epithelial-Mesenchymal Transition in Lung Cancer Cells via P53-Mdm2-Snail Pathway

PURPOSE

The epithelial-to-mesenchymal transition (EMT) is a fundamental process in tumor progression that endows cancer cells with migratory and invasive potential. Snail, a zinc finger transcriptional repressor, plays an important role in the induction of EMT by directly repressing the key epithelial marker E-cadherin. Here, we assessed the effect of urolithin A, a major metabolite from pomegranate ellagitannins, on Snail expression and EMT process.

METHODS

The role of Snail in urolithin A-induced EMT inhibition in lung cancer cells was explored by wound healing assay and cell invasion assay. The qRT-PCR and CHX assay were performed to investigate how urolithin A regulates Snail expression. Immunoprecipitation assays were established to determine the effects of urolithin A in mdm2-Snail interaction. In addition, the expression of p53 was manipulated to explore its effect on the expression of mdm2 and Snail.

RESULTS

The urolithin A dose-dependently upregulated epithelial marker and decreased mesenchymal markers in lung cancer cells. In addition, exposure to urolithin A decreased cell migratory and invasive capacity. We have further demonstrated that urolithin A inhibits lung cancer cell EMT by decreasing Snail protein expression and activity. Mechanistically, urolithin A disrupts the interaction of p53 and mdm2 which leads Snail ubiquitination and degradation.

CONCLUSION

We conclude that urolithin A could inhibit EMT process by controlling mainly Snail expression. These results highlighted the role of pomegranate in regulation of EMT program in lung cancer.

Oncogenic Gain of Function in Glioblastoma Is Linked to Mutant p53 Amyloid Oligomers

Tumor-associated p53 mutations endow cells with malignant phenotypes, including chemoresistance. Amyloid-like oligomers of mutant p53 transform this tumor suppressor into an oncogene. However, the composition and distribution of mutant p53 oligomers are unknown and the mechanism involved in the conversion is sparse. Here, we report accumulation of a p53 mutant within amyloid-like p53 oligomers in glioblastoma-derived cells presenting a chemoresistant gain-of-function phenotype. Statistical analysis from fluorescence fluctuation spectroscopy, pressure-induced measurements, and thioflavin T kinetics demonstrates the distribution of oligomers larger than the active tetrameric form of p53 in the nuclei of living cells and the destabilization of native-drifted p53 species that become amyloid. Collectively, these results provide insights into the role of amyloid-like mutant p53 oligomers in the chemoresistance phenotype of malignant and invasive brain tumors and shed light on therapeutic options to avert cancer.

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Amyloid oligomers transform p53 tumor suppressor into an oncogene

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Amyloid-like mutant p53 oligomers occur in chemoresistant glioblastoma cells

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p53 oligomer larger than tetramers is detected in the nuclei of living cells

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Gain-of-function p53 phenotypes is attributed to p53 amyloid oligomers

Snail1: A Transcriptional Factor Controlled at Multiple Levels

Snail1 transcriptional factor plays a key role in the control of epithelial to mesenchymal transition and fibroblast activation. As a consequence, Snail1 expression and function is regulated at multiple levels from gene transcription to protein modifications, affecting its interaction with specific cofactors. In this review, we describe the different elements that control Snail1 expression and its activity both as transcriptional repressor or activator.

Control of the Epithelial-to-Mesenchymal Transition and Cancer Metastasis by Autophagy-Dependent SNAI1 Degradation

Autophagy, an intracellular degradation process, is essential for maintaining cell homeostasis by removing damaged organelles and proteins under various conditions of stress. In cancer, autophagy has conflicting functions. It plays a key role in protecting against cancerous transformation by maintaining genomic stability against genotoxic components, leading to cancerous transformation. It can also promote cancer cell survival by supplying minimal amounts of nutrients during cancer progression. However, the molecular mechanisms underlying how autophagy regulates the epithelial-to-mesenchymal transition (EMT) and cancer metastasis are unknown. Here, we show that starvation-induced autophagy promotes Snail (SNAI1) degradation and inhibits EMT and metastasis in cancer cells. Interestingly, SNAI1 proteins were physically associated and colocalized with LC3 and SQSTM1 in cancer cells. We also found a significant decrease in the levels of EMT and metastatic proteins under starvation conditions. Furthermore, ATG7 knockdown inhibited autophagy-induced SNAI1 degradation in the cytoplasm, which was associated with a decrease in SNAI1 nuclear translocation. Moreover, cancer cell invasion and migration were significantly inhibited by starvation-induced autophagy. These findings suggest that autophagy-dependent SNAI1 degradation could specifically regulate EMT and cancer metastasis during tumorigenesis.

Role of vitamin D3 combined to alginates in preventing acid and oxidative injury in cultured gastric epithelial cells

Background

Gastric diseases are a worldwide problem in modern society, as reported in the USA, in the range of 0.5–2 episodes/year/person and an incidence of 5–100 episodes/1000/week according to seasons and age. There is convincing evidence that oxidative stress is involved in the pathogenesis of acute gastric injury. Acid secreted from gastric parietal cells determines mucosal injuries which in turn cause inflammation and oxidative stress. Consequent inflammation produces free radicals by mitochondria thus causing lipid peroxidation, oxidative and acidic stress, which can lead to cell apoptosis. Vitamin D_3, the active form of vitamin D, may counteract intracellular cell death and improve epithelial regeneration.

Methods

This study was planned to assess whether vitamin D₃ is a protective factor against acid injury and oxidative stress in gastric epithelial cells. Primary epithelial cells and GTL-16 cells have been used to test the effects of Grisù® alone or in combination with vitamin D₃ during oxidative stress or high acid exposition measuring cell viability, ROS production, cellular adhesion time along with apoptotic, autophagic and survival pathways. The combined effect of Grisù® and vitamin D₃ was found more effective in counteracting the negative consequences of oxidative stress and acidity conditions than some other gastroprotective agents, such as Maalox® or Gaviscon®.

Results

In case of oxidative stress or acidity condition the stimulation with Grisù® alone caused an improvement of cell viability and a reduction of ROS production on epithelial gastric cells. In addition, the adhesion time of the cells was improved. All these effects were increased by the presence of vitamin D₃. Similar data were also observed in primary gastric epithelial cells confirming the results obtained in GTL-16 cells.

Conclusions

These results suggest that Grisù® in combination with vitamin D₃ may exert a gastroprotective effect to maintain or restore the integrity of gastric epithelium through an antioxidant pathway, inhibiting apoptosis and activating survival kinases. Moreover, the combination of Grisù® and vitamin D₃ improves cell viability and decreases ROS production compared to other gastroprotective agents combined with vitamin D₃. All these data were validated using primary cells isolated from gastric tissue.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0543-z) contains supplementary material, which is available to authorized users.

Protective effects of 1α,25-Dihydroxyvitamin D3 on cultured neural cells exposed to catalytic iron

Recent studies have postulated a role for vitamin D and its receptor on cerebral function, and anti‐inflammatory, immunomodulatory and neuroprotective effects have been described; vitamin D can inhibit proinflammatory cytokines and nitric oxide synthesis during various neurodegenerative insults, and may be considered as a potential drug for the treatment of these disorders. In addition, iron is crucial for neuronal development and neurotransmitter production in the brain, but its accumulation as catalytic form (Fe³⁺) impairs brain function and causes the dysregulation of iron metabolism leading to tissue damage due to the formation of toxic free radicals (ROS). This research was planned to study the role of vitamin D to prevent iron damage in neuroblastoma BE(2)M17 cells. Mechanisms involved in neurodegeneration, including cell viability, ROS production, and the most common intracellular pathways were studied. Pretreatment with calcitriol (the active form of vitamin D) reduced cellular injury induced by exposure to catalytic iron.

Aggregation and Prion-Like Properties of Misfolded Tumor Suppressors: Is Cancer a Prion Disease?

Prion diseases are disorders that share several characteristics that are typical of many neurodegenerative diseases. Recently, several studies have extended the prion concept to pathological aggregation in malignant tumors involving misfolded p53, a tumor-suppressor protein. The aggregation of p53 and its coaggregation with p53 family members, p63 and p73, have been shown. Certain p53 mutants exert a dominant-negative regulatory effect on wild-type (WT) p53. The basis for this dominant-negative effect is that amyloid-like mutant p53 converts WT p53 into an aggregated species, leading to a gain-of-function (GoF) phenotype and the loss of its tumor-suppressor function. Recently, it was shown that p53 aggregates can be internalized by cells and can coaggregate with endogenous p53, corroborating the prion-like properties of p53 aggregates. The prion-like behavior of oncogenic p53 mutants provides an explanation for its dominant-negative and GoF properties, including the high metastatic potential of cancer cells carrying p53 mutations. The inhibition of p53 aggregation appears to represent a promising target for therapeutic intervention in patients with malignant tumors.

Protective effects of vitamin D3 on fimbrial cells exposed to catalytic iron damage

Background

Recently, vitamin D₃ (1alpha, 25-dihydroxyvitamin D) has shown its capability to take part in many extraskeletal functions and its serum levels have been related to patient survival rate and malignancy of many types of neoplasms, including ovarian cancers. Catalytic iron is a free circulating form of iron that is able to generate reactive oxygen species and consequently to promote a number of cellular and tissutal dysfunctions including tumorigenesis. In fertile women an important source of catalytic iron is derived from retrograde menstruation. Epithelial secretory cells from fimbriae of fallopian tubes are greatly exposed to catalytic iron derived from menstrual reflux and so represent the site of origin for most serous ovarian cancers.

The aim of this study was to assess whether vitamin D₃ can play a role in counteracting catalytic iron-induced oxidative stress in cells from fimbriae of fallopian tubes.

Methods

The cells, isolated from women undergoing isteroannessiectomy, were treated with catalytic iron 50-75-100 mM and vitamin D₃ at a concentration ranging from 0.01 to 10 nM to study cell viability, radical oxygen species production, p53, pan-Ras, Ki67 and c-Myc protein expressions through Western Blot, and immunocytochemistry or immunofluorescence analysis.

Results

The pre-treatment with vitamin D₃ 1 nM showed its beneficial effects that consists in a significant decrease in ROS production. In addition a novel finding is represented by the demonstration that pre-treatment with vitamin D₃ is also able to significantly counteract tumoral biomarkers activation, such as p53, pan-Ras, Ki67 and c-Myc, and consequently the catalytic iron-induced cellular injury.

Conclusions

This study demonstrates for the first time that vitamin D₃ plays an important role in preventing catalytic iron-dependent oxidative stress in cultured fimbrial cells. These results support the hypothesis that vitamin D₃ could counteract carcinogenic changes induced by catalytic iron.

Inhibiting DX2-p14/ARF Interaction Exerts Antitumor Effects in Lung Cancer and Delays Tumor Progression

The aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2) splice variant designated DX2 is induced by cigarette smoke carcinogens and is often detected in human lung cancer specimens. However, the function of DX2 in lung carcinogenesis is obscure. In this study, we found that DX2 expression was induced by oncogenes in human lung cancer tissues and cells. DX2 prevented oncogene-induced apoptosis and senescence and promoted drug resistance by directly binding to and inhibiting p14/ARF. Through chemical screening, we identified SLCB050, a novel compound that blocks the interaction between DX2 and p14/ARF in vitro and in vivo SLCB050 reduced the viability of human lung cancer cells, especially small cell lung cancer cells, in a p14/ARF-dependent manner. Moreover, in a mouse model of K-Ras-driven lung tumorigenesis, ectopic expression of DX2 induced small cell and non-small cell lung cancers, both of which could be suppressed by SLCB050 treatment. Taken together, our findings show how DX2 promotes lung cancer progression and how its activity may be thwarted as a strategy to treat patients with lung cancers exhibiting elevated DX2 levels. Cancer Res; 76(16); 4791-804. ©2016 AACR.

NF2 blocks Snail-mediated p53 suppression in mesothelioma

Although asbestos causes malignant pleural mesothelioma (MPM), rising from lung mesothelium, the molecular mechanism has not been suggested until now. Extremely low mutation rate in classical tumor suppressor genes (such as p53 and pRb) and oncogenes (including Ras or myc) indicates that there would be MPM-specific carcinogenesis pathway. To address this, we treated silica to mimic mesothelioma carcinogenesis in mesothelioma and non-small cell lung cancer cell lines (NSCLC). Treatment of silica induced p-Erk and Snail through RKIP reduction. In addition, p53 and E-cadherin were decreased by silica-treatment. Elimination of Snail restored p53 expression. We found that NF2 (frequently deleted in MPM) inhibited Snail-mediated p53 suppression and was stabilized by RKIP. Importantly, GN25, an inhibitor of p53-Snail interaction, induced p53 and apoptosis. These results indicate that MPM can be induced by reduction of RKIP/NF2, which suppresses p53 through Snail. Thus, the p53-Snail binding inhibitor such as GN25 is a drug candidate for MPM.

Potential functional applications of extracellular vesicles: a report by the NIH Common Fund Extracellular RNA Communication Consortium

The NIH Extracellular RNA Communication Program's initiative on clinical utility of extracellular RNAs and therapeutic agents and developing scalable technologies is reviewed here. Background information and details of the projects are presented. The work has focused on modulation of target cell fate by extracellular vesicles (EVs) and RNA. Work on plant-derived vesicles is of intense interest, and non-mammalian sources of vesicles may represent a very promising source for different therapeutic approaches. Retro-viral-like particles are intriguing. Clearly, EVs share pathways with the assembly machinery of several other viruses, including human endogenous retrovirals (HERVs), and this convergence may explain the observation of viral-like particles containing viral proteins and nucleic acid in EVs. Dramatic effect on regeneration of damaged bone marrow, renal, pulmonary and cardiovascular tissue is demonstrated and discussed. These studies show restoration of injured cell function and the importance of heterogeneity of different vesicle populations. The potential for neural regeneration is explored, and the capacity to promote and reverse neoplasia by EV exposure is described. The tremendous clinical potential of EVs underlies many of these projects, and the importance of regulatory issues and the necessity of general manufacturing production (GMP) studies for eventual clinical trials are emphasized. Clinical trials are already being pursued and should expand dramatically in the near future.

Misfolding, Aggregation, and Disordered Segments in c-Abl and p53 in Human Cancer

The current understanding of the molecular mechanisms that lead to cancer is not sufficient to explain the loss or gain of function in proteins related to tumorigenic processes. Among them, more than 100 oncogenes, 20-30 tumor-suppressor genes, and hundreds of genes participating in DNA repair and replication have been found to play a role in the origins of cancer over the last 25 years. The phosphorylation of serine, threonine, or tyrosine residues is a critical step in cellular growth and development and is achieved through the tight regulation of protein kinases. Phosphorylation plays a major role in eukaryotic signaling as kinase domains are found in 2% of our genes. The deregulation of kinase control mechanisms has disastrous consequences, often leading to gains of function, cell transformation, and cancer. The c-Abl kinase protein is one of the most studied targets in the fight against cancer and is a hotspot for drug development because it participates in several solid tumors and is the hallmark of chronic myelogenous leukemia. Tumor suppressors have the opposite effects. Their fundamental role in the maintenance of genomic integrity has awarded them a role as the guardians of DNA. Among the tumor suppressors, p53 is the most studied. The p53 protein has been shown to be a transcription factor that recognizes and binds to specific DNA response elements and activates gene transcription. Stress triggered by ionizing radiation or other mutagenic events leads to p53 phosphorylation and cell-cycle arrest, senescence, or programed cell death. The p53 gene is the most frequently mutated gene in cancer. Mutations in the DNA-binding domain are classified as class I or class II depending on whether substitutions occur in the DNA contact sites or in the protein core, respectively. Tumor-associated p53 mutations often lead to the loss of protein function, but recent investigations have also indicated gain-of-function mutations. The prion-like aggregation of mutant p53 is associated with loss-of-function, dominant-negative, and gain-of-function effects. In the current review, we focused on the most recent insights into the protein structure and function of the c-Abl and p53 proteins that will provide us guidance to understand the loss and gain of function of these misfolded tumor-associated proteins.

Extracellular p53 fragment re-enters K-Ras mutated cells through the caveolin-1 dependent early endosomal system

K-Ras mutation is detected in over 30% of human malignancies. In particular, 90% of human pancreatic cancers are initiated by K-Ras mutation. Thus, selective elimination of K-Ras mutated cells would be a plausible strategy to prevent or cure the malignancies. In our previous reports, it has been revealed that oncogenic K-Ras promotes the exocytosis of p53 with Snail. In this study, we have followed the final destination of extracellular p53, which is secreted by the Snail complex. Here we provide evidences that p53, exported from K-Ras-mutated cells, is specifically re-endocytosed by oncogenic K-Ras-containing cancer cells. The p53 DNA-binding domain directly associates with caveolin-1 and enters K-Ras mutated cells through early endosome-mediated endocytosis. Using a serial deletion approach, we revealed that a fragment of human p53 extending from 93-143 amino acids (AA) is responsible for binding with caveolin-1 and for endocytosis. In contrast, p53-Snail binding occurs at the 143-193 aa region. Finally, through in vivo study, we confirmed that injected recombinant p53 could be up-taken by tumor tissues, constructed by oncogenic K-Ras transformed MEF cells. In contrast, the tumors formed by H-Ras mutated MEF cells did not accumulate the injected p53 protein. These results indicate that the p53 fragment might be useful as a specific delivery tool into K- Ras mutated cells as well as a diagnostic method.

Caveolin-1 regulates metastatic behaviors of anoikis resistant lung cancer cells

Caveolin-1 (Cav-1), a protein component of cellular membrane, has been reported to regulate several cancer cell behaviors. However, its role on cancer metastasis in anoikis resistant cells is unknown. The present study aimed to investigate the correlation between Cav-1 level and aggressive behaviors of anoikis resistant cancer cells. Cav-1 and ShRNACav-1 stably transfected lung carcinoma cells, and anoikis resistant H_AR1 and H_AR2 cells expressing different levels of Cav-1 were subjected to anoikis, cell growth, anchorage-independent growth, extracellular matrix adhesion, cisplatin sensitivity, migration, and invasion assays. The correlations between cellular Cav-1 level and such cancer aggressive behaviors were evaluated. Results revealed that anoikis resistant lung cancer cells as well as Cav-1 overexpressing cells exhibit a significant increase in anchorage-independent growth, extracellular matrix adhesion, migration, and invasion in comparison to those of their parental H460 cells. Knock-down of Cav-1 by ShRNA transfection was able to reverse such metastatic potentials in H_AR2 cells. In addition, basal Cav-1 level of these cells was positively correlated with anoikis resistance, anchorage-independent growth, migration, and invasion behaviors of the cells, whereas such Cav-1 level showed poor correlation to cisplatin sensitivity, cell adhesion, and growth in attached condition. These findings give more information regarding role of Cav-1 in the regulation of behaviors of lung cancer cells.

The Role of Snail in EMT and Tumorigenesis

Epithelial-mesenchymal transition (EMT) is a highly conserved process in which polarized, immobile epithelial cells lose tight junctions, associated adherence, and become migratory mesenchymal cells. Several transcription factors, including the Snail/Slug family, Twist, δEF1/ZEB1, SIP1/ZEB2 and E12/E47 respond to microenvironmental stimuli and function as molecular switches for the EMT program. Snail is a zinc-finger transcriptional repressor controlling EMT during embryogenesis and tumor progression. Through its N-terminal SNAG domain, Snail interacts with several corepressors and epigenetic remodeling complexes to repress specific target genes, such as the E-cadherin gene (CDH1). An integrated and complex signaling network, including the RTKs, TGF-β, Notch, Wnt, TNF-α, and BMPs pathways, activates Snail, thereby inducing EMT. Snail expression correlates with the tumor grade, nodal metastasis of many types of tumor and predicts a poor outcome in patients with metastatic cancer. Emerging evidences indicate that Snail causes a metabolic reprogramming, bestows tumor cells with cancer stem cell-like traits, and additionally, promotes drug resistance, tumor recurrence and metastasis. Despite many new and exciting developments, several challenges remain to be addressed in order to understand more thoroughly the role of Snail in metastasis. Additional investigations are required to disclose the contribution of microenvironmental factors on tumor progression. This information will lead to a comprehensive understanding of Snail in cancer and will provide us with novel approaches for preventing and treating metastatic cancers.

Central role of Snail1 in the regulation of EMT and resistance in cancer: a target for therapeutic intervention

Snail1 is the founding member of the Snail superfamily of zinc-finger transcription factors, which also includes Snail2 (Slug) and Snail3 (Smuc). The superfamily is involved in cell differentiation and survival, two processes central in cancer research. Encoded by the SNAI1 gene located on human chromosome 20q13.2, Snail1 is composed of 264 amino acids and usually acts as a transcriptional repressor. Phosphorylation and nuclear localization of Snail1, governed by PI3K and Wnt signaling pathways crosstalk, are critical in Snail1’s regulation. Snail1 has a pivotal role in the regulation of epithelial-mesenchymal transition (EMT), the process by which epithelial cells acquire a migratory, mesenchymal phenotype, as a result of its repression of E-cadherin. Snail1-induced EMT involves the loss of E-cadherin and claudins with concomitant upregulation of vimentin and fibronectin, among other biomarkers. While essential to normal developmental processes such as gastrulation, EMT is associated with metastasis, the cancer stem cell phenotype, and the regulation of chemo and immune resistance in cancer. Snail1 expression is a common sign of poor prognosis in metastatic cancer, and tumors with elevated Snail1 expression are disproportionately difficult to eradicate by current therapeutic treatments. The significance of Snail1 as a prognostic indicator, its involvement in the regulation of EMT and metastasis, and its roles in both drug and immune resistance point out that Snail1 is an attractive target for tumor growth inhibition and a target for sensitization to cytotoxic drugs.

Prion-like aggregation of mutant p53 in cancer

p53 is a master regulatory protein that participates in cellular processes such as apoptosis, DNA repair, and cell cycle control. p53 functions as a homotetrameric tumor suppressor, and is lost in more than 50% of human cancers. Recent studies have suggested that the formation of mutant p53 aggregates is associated with loss-of-function (LoF), dominant-negative (DN), and gain-of-function (GoF) effects. We propose that these phenomena can be explained by a prion-like behavior of mutant p53. We discuss the shared properties of cancer and neurodegenerative diseases and how the prion-like properties of p53 aggregates offer potential targets for drug development.

NQO1 C609T polymorphism correlated to colon cancer risk in farmers from western region of Inner Mongolia

OBJECTIVE

To investigate the relationship between NAD(P)H:quinone oxidoreductase 1 (NQO1) C609T polymorphism and colon cancer risk in farmers from western region of Inner Mongolia.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to analyze NQO1 C609T polymorphism from 160 healthy controls and 76 colon cancer patients.

RESULTS

Among the colon cancer patients, the incidence of NQO1 T allele (53.29%) was significantly higher than it in control group (33.75%, P<0.001). The individuals with NQO1 T allele had higher risk [2.239 (95% CI: 
1.510-3.321) times] to develop colon cancer than individuals with NQO1 C allele. The incidence of NQO1
 (T/T) (34.21%) in colon cancer patients was higher than that in control group (15.62%, P<0.001). Odds ratios (OR) analysis suggested that NQO1 (T/T) and NQO1 (T/C) genotype carriers had 3.813 (95% CI: 1.836-7.920) times and 2.080 (1.026-4.219) times risk compared with wild-type NQO1 (C/C) gene carriers in developing colon cancer. Individuals with NQO1 (T/T) genotype had 2.541 (95% CI: 0.990-6.552) times, 3.713 (95% CI: 1.542-8.935) times, and 3.471 (95% CI: 1.356-8.886) times risk than individuals with NQO1 (T/C) or NQO1 (C/C) genotype in well-differentiated, moderately-differentiated, and poorly-differentiated colon cancer patients, respectively.

CONCLUSIONS

NQO1 gene C609T could be one of risk factors of colon cancer in farmers from western region of Inner Mongolia.

Molecular markers in pancreatic cancer diagnosis

Pancreatic ductal adenocarcinoma (PDAC) represents a fatal neoplasia with a high mortality rate. Effective early detection methods are needed since this is the best way to cure this disease. During the last several years, many investigations focused on determining relevant biomarkers that may be present during early stages of pancreatic tumor development. Although several biomarkers have been proposed for pancreatic cancer detection, the clinical applicability has been confusing. Currently, although CA19-9 is one test used, the sensitivity and specificity for the disease are less than optimal. Here, we review several new potential serum, plasma and stool markers that are currently under evaluation. Although these have not been sufficiently validated for routine clinical use, these markers could prove valuable with further investigations. We keep the hope that a combination of some of these novel biomarkers can be a useful tool for early PDAC diagnosis before image techniques and/or patient's symptoms reveal disease in an incurable state.

[The cooperation between p53 and Ras in tumorigenesis]

Inactivation of the tumor suppressor gene and activation of the oncogene cooperate to promote the multistep process of tumorigenesis. p53 is considered to be the most important tumor suppressor gene. p53 is usually found as a result of somatic missense mutation in approximately 50% of human cancers. Ras is found to be one of the most frequently mutated oncogenes in human tumors with the reported frequencies ranging from 30% to 90%. It has been found in many studies synergistic effect between tumor suppressor p53 and oncogene Ras occurs during the multistep process of tumorigenesis. According to the current reports, the cooperative effect between p53 and Ras can be divided into three types: the regulation of p53 for Ras function, , the regulation of Ras for p53, and the cooperation between p53 and Ras to control critical genes that are closely related to tumorigenesis. Understanding their synergistic effects will not only help us further disclose mechanism of tumorigenesis caused by p53 inactivation and Ras activation, but also facilitate personalized treatments and pharmacological target selection for cancer therapy. Therefore, we reviewed the recent progress of synergistic effect be-tween p53 and Ras and its role in tumorigenesis.

Antitumor effect of novel small chemical inhibitors of Snail-p53 binding in K-Ras-mutated cancer cells

p53 is frequently mutated by genetic alternation or suppressed by various kinds of cellular signaling pathways in human cancers. Recently, we have revealed that p53 is suppressed and eliminated from cells by direct binding with oncogenic K-Ras-induced Snail. On the basis of the fact, we generated specific inhibitors against p53-Snail binding (GN25 and GN29). These chemicals can induce p53 expression and functions in K-Ras-mutated cells. However, it does not show cytotoxic effect on normal cells or K-Ras-wild-type cells. Moreover, GN25 can selectively activate wild-type p53 in p53(WT/MT) cancer cells. But single allelic mt p53 containing cell line, Panc-1, does not respond to our chemical. In vivo xenograft test also supports the antitumor effect of GN25 in K-Ras-mutated cell lines. These results suggest that our compounds are strong candidate for anticancer drug against K-Ras-initiated human cancers including pancreatic and lung cancers.