Suppression of familial adenomatous polyposis by CP-31398, a TP53 modulator, in APCmin/+ mice

The Antagonistic and Synergistic Role of Fe3+ Compounds in Chemo- and Electrochemotherapy in Human Colon Cancer In Vitro

Colon cancer (CC) management includes surgery, radio- and chemotherapy based on treatment with 5-fluorouracil (5-FU) or its derivatives. However, its application is limited to low-grade carcinomas. Thus, much research has been conducted to introduce new techniques and drugs to the therapy. CC mostly affects older people suffering from cardiac diseases, where iron compounds are commonly used. Ferric citrate and iron (III)-EDTA complexes have proven to be effective in colon cancer in vitro. This study aimed to determine the potency and action of iron-containing compounds in colon cancer treatment by chemo- and electrochemotherapy in both nano- and microsecond protocols. The viability of the cells was assessed after standalone iron (III) citrate and iron (III)-EDTA incubation. Both compounds were also assessed with 5-FU to determine the combination index. Additionally, frataxin expression was taken as the quantitative response to the exposition of iron compounds. Each of the substances exhibited a cytotoxic effect on the LoVo cell line. Electroporation with standalone drugs revealed the potency of 5-FU and iron(III)-EDTA in CC treatment. The combination of 5-FU with iron(III)-EDTA acted synergistically, increasing the viability of the cells in the nanosecond electrochemotherapy protocol. Iron(III)-EDTA decreased the frataxin expression, thus inducing ferroptosis. Iron(III) citrate induced the progression of cancer; therefore, it should not be considered as a potential therapeutic option. The relatively low stability of iron(III) citrate leads to the delivery of citrate anions to cancer cells, which could increase the Krebs cycle rate and promote progression.

Lentiviral in situ targeting of stem cells in unperturbed intestinal epithelium

BACKGROUND

Methods for the long-term in situ transduction of the unperturbed murine intestinal epithelium have not been developed in past research. Such a method could speed up functional studies and screens to identify genetic factors influencing intestinal epithelium biology. Here, we developed an efficient method achieving this long-sought goal.

RESULTS

We used ultrasound-guided microinjections to transduce the embryonic endoderm at day 8 (E8.0) in utero. The injection procedure can be completed in 20 min and had a 100% survival rate. By injecting a small volume (0.1-0.2 μl) of concentrated virus, single shRNA constructs as well as lentiviral libraries can successfully be transduced. The new method stably and reproducibly targets adult intestinal epithelium, as well as other endoderm-derived organs such as the lungs, pancreas, liver, stomach, and bladder. Postnatal analysis of young adult mice indicates that single transduced cells at E8.0 gave rise to crypt fields that were comprised of 20-30 neighbouring crypts per crypt-field at 90 days after birth. Lentiviral targeting of ApcMin/+ mutant and wildtype mice revealed that heterozygous loss of Apc function suppresses the developmental normal growth pattern of intestinal crypt fields. This suppression of crypt field sizes did not involve a reduction of the crypt number per field, indicating that heterozygous Apc loss impaired the growth of individual crypts within the fields. Lentiviral-mediated shRNA knockdown of p53 led to an approximately 20% increase of individual crypts per field in both Apc+/+ and ApcMin/+ mice, associating with an increase in crypt size in ApcMin/+ mice but a slight reduction in crypt size in Apc+/+ mice. Overall, p53 knockdown rescued the reduction in crypt field size in Apc-mutant mice but had no effect on crypt field size in wildtype mice.

CONCLUSIONS

This study develops a novel technique enabling robust and reproducible in vivo targeting of intestinal stem cells in situ in the unperturbed intestinal epithelium across different regions of the intestine. In vivo somatic gene editing and genetic screening of lentiviral libraries has the potential to speed up discoveries and mechanistic understanding of genetic pathways controlling the biology of the intestinal epithelium during development and postnatal life. The here developed method enables such approaches.

Transition of amyloid/mutant p53 from tumor suppressor to an oncogene and therapeutic approaches to ameliorate metastasis and cancer stemness

The tumor suppressor p53 when undergoes amyloid formation confers several gain-of-function (GOF) activities that affect molecular pathways crucial for tumorigenesis and progression like some of the p53 mutants. Even after successful cancer treatment, metastasis and recurrence can result in poor survival rates. The major cause of recurrence is mainly the remnant cancer cells with stem cell-like properties, which are resistant to any chemotherapy treatment. Several studies have demonstrated the role of p53 mutants in exacerbating cancer stemness properties and epithelial-mesenchymal transition in these remnant cancer cells. Analyzing the amyloid/mutant p53-mediated signaling pathways that trigger metastasis, relapse or chemoresistance may be helpful for the development of novel or improved individualized treatment plans. In this review, we discuss the changes in the metabolic pathways such as mevalonate pathway and different signaling pathways such as TGF-β, PI3K/AKT/mTOR, NF-κB and Wnt due to p53 amyloid formation, or mutation. In addition to this, we have discussed the role of the regulatory microRNAs and lncRNAs linked with the mutant or amyloid p53 in human malignancies. Such changes promote tumor spread, potential recurrence, and stemness. Importantly, this review discusses the cancer therapies that target either mutant or amyloid p53, restore wild-type functions, and exploit the synthetic lethal interactions with mutant p53.

Molecular Targets in Precision Chemoprevention of Colorectal Cancer: An Update from Pre-Clinical to Clinical Trials

Colorectal cancer (CRC) is one of the leading causes of cancer deaths worldwide. The initiation and progression of CRC is a multi-step process that proceeds via precursor lesions to carcinoma, with each stage characterized by its distinct molecular and tissue microenvironment changes. Precursor lesions of CRC, aberrant crypt foci, and adenoma exhibit drastic changes in genetic, transcriptomic, and proteomic profiles compared to normal tissue. The identification of these changes is essential and provides further validation as an initiator or promoter of CRC and, more so, as lesion-specific druggable molecular targets for the precision chemoprevention of CRC. Mutated/dysregulated signaling (adenomatous polyposis coli, β-catenin, epidermal growth factor receptor, V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), tumor protein53, Akt, etc.), inflammatory (cyclooxygenase-2, microsomal prostaglandin E synthase-1, inducible nitric oxide synthase, and other pro-inflammatory mediators), and metabolic/growth factor (fatty acid synthase, β-Hydroxy β-methylglutaryl-CoA reductase, and ornithine decarboxylase) related targets are some of the well-characterized molecular targets in the precision chemoprevention of CRC. In this review, we discuss precursor-lesion specific targets of CRC and the current status of pre-clinical studies regarding clinical interventions and combinations for better efficacy and safety toward future precision clinical chemoprevention. In addition, we provide a brief discussion on the usefulness of secondary precision chemopreventive targets for tertiary precision chemoprevention to improve the disease-free and overall survival of advanced stage CRC patients.

Aspirin Reduces Colorectal Tumor Development in Mice and Gut Microbes Reduce its Bioavailability and Chemopreventive Effects

BACKGROUND & AIMS

Alterations in the intestinal microbiota affect development of colorectal cancer and drug metabolism. We studied whether the intestinal microbiota affect the ability of aspirin to reduce colon tumor development in mice.

METHODS

We performed studies with APC^min/+ mice and mice given azoxymethane and dextran sulfate sodium to induce colorectal carcinogenesis. Some mice were given antibiotics to deplete intestinal microbes, with or without aspirin, throughout the entire experiment. Germ-free mice were studied in validation experiments. Colon tissues were collected and analyzed by histopathology, quantitative reverse-transcription polymerase chain reaction, and immunoblots. Blood samples and gut luminal contents were analyzed by liquid chromatography/mass spectrometry and an arylesterase activity assay. Fecal samples were analyzed by 16S ribosomal RNA gene and shotgun metagenome sequencing.

RESULTS

Administration of aspirin to mice reduced colorectal tumor number and load in APC^min/+ mice and mice given azoxymethane and dextran sulfate sodium that had been given antibiotics (depleted gut microbiota), but not in mice with intact microbiota. Germ-free mice given aspirin developed fewer colorectal tumors than conventionalized germ-free mice given aspirin. Plasma levels of aspirin were higher in mice given antibiotics than in mice with intact gut microbiota. Analyses of luminal contents revealed that aerobic gut microbes, including Lysinibacillus sphaericus, degrade aspirin. Germ-free mice fed L sphaericus had lower plasma levels of aspirin than germ-free mice that were not fed this bacterium. There was an inverse correlation between aspirin dose and colorectal tumor development in conventional mice, but this correlation was lost with increased abundance of L sphaericus. Fecal samples from mice fed aspirin were enriched in Bifidobacterium and Lactobacillus genera, which are considered beneficial, and had reductions in Alistipes finegoldii and Bacteroides fragili, which are considered pathogenic.

CONCLUSIONS

Aspirin reduces development of colorectal tumors in APC^min/+ mice and mice given azoxymethane and dextran sulfate sodium, depending on the presence of intestinal microbes. L sphaericus in the gut degrades aspirin and reduced its chemopreventive effects in mice. Fecal samples from mice fed aspirin were enriched in beneficial bacteria, with reductions in pathogenic bacteria.

Metabolite Profiling in Anticancer Drug Development: A Systematic Review

Drug metabolism is one of the most important pharmacokinetic processes and plays an important role during the stage of drug development. The metabolite profile investigation is important as the metabolites generated could be beneficial for therapy or leading to serious toxicity. This systematic review aims to summarize the research articles relating to the metabolite profile investigation of conventional drugs and herb-derived compounds for cancer chemotherapy, to examine factors influencing metabolite profiling of these drugs/compounds, and to determine the relationship between therapeutic efficacy and toxicity of their metabolites. The literature search was performed through PubMed and ScienceDirect databases up to January 2019. Out of 830 published articles, 78 articles were included in the analysis based on pre-defined inclusion and exclusion criteria. Both phase I and II enzymes metabolize the anticancer agents/herb-derived compounds . The major phase I reactions include oxidation/hydroxylation and hydrolysis, while the major phase II reactions are glucuronidation, methylation, and sulfation. Four main factors were found to influence metabolite formation, including species, gender, and route and dose of drug administration. Some metabolites were identified as active or toxic metabolites. This information is critical for cancer chemotherapy and anticancer drug development.

Awakening the "guardian of genome": reactivation of mutant p53

The role of tumor suppressor protein p53 is undeniable in the suppression of cancer upon oncogenic stress. It induces diverse conditions such as cell-cycle arrest, cell death, and senescence to protect the cell from carcinogenesis. The rate of mutations in p53 gene nearly accounts for 50% of the human cancers. Upon mutations, the conformation gets altered and becomes non-native. Mutant p53 displays long half-life and accumulates in the nucleus and interacts with oncoproteins to promote carcinogenesis and these interactions present a formidable challenge for clinicians in therapy of the disease. Variety of approaches have been developed, through which native-like function of p53 can be restored, such as restoration of the native-like structure of p53, activating the p53 family members, etc. Modern scientific techniques have led to the discovery of a variety of molecules to reactivate mutant p53 and restore its transcriptional activity. These compounds include small molecules, various peptides, and phytochemicals. In this review article, we comprehensively discuss these molecules to reactivate mutant p53 to restore the normal function with a particular focus on molecular mechanisms.

Targeting cancer stem cells with p53 modulators

Cancer stem cells (CSC) typically over-express aldehyde dehydrogenase (ALDH). Thus, ALDH^bright tumor cells represent targets for developing novel cancer prevention/treatment interventions. Loss of p53 function is a common genetic event during cancer development wherein small molecular weight compounds (SMWC) that restore p53 function and reverse tumor growth have been identified. Here, we focused on two widely studied p53 SMWC, CP-31398 and PRIMA-1, to target ALDH^bright CSC in human breast, endometrial and pancreas carcinoma cell lines expressing mutant or wild type (WT) p53. CP-31398 and PRIMA-1 significantly reduced CSC content and sphere formation by these cell lines in vitro. In addition, these agents were more effective in vitro against CSC compared to cisplatin and gemcitabine, two often-used chemotherapeutic agents. We also tested a combinatorial treatment in methylcholantrene (MCA)-treated mice consisting of p53 SMWC and p53-based vaccines. Yet using survival end-point analysis, no increased efficacy in the presence of either p53 SMWC alone or with vaccine compared to vaccine alone was observed. These results may be due, in part, to the presence of immune cells, such as activated lymphocytes expressing WT p53 at levels comparable to some tumor cells, wherein further increase of p53 expression by p53 SMWC may alter survival of these immune cells and negatively impact an effective immune response. Continuous exposure of mice to MCA may have also interfered with the action of these p53 SMWC, including potential direct interaction with MCA. Nonetheless, the effect of p53 SMWC on CSC and cancer treatment remains of great interest.

Chemoprevention of spontaneous ovarian cancer in the domestic hen

The hen is an attractive animal model for in vivo testing of agents that thwart ovarian carcinogenesis because ovarian cancer in the domestic hen features clinical and molecular alterations that are similar to ovarian cancer in humans, including a high incidence of p53 mutations. The objective of the study was to test the potential ovarian cancer chemopreventive effect of the p53 stabilizing compound CP-31398 on hens that spontaneously present the ovarian cancer phenotype. Beginning at 79 wk of age, 576 egg-laying hens (Gallus domesticus) were randomized to diets containing different amounts of CP-31398 for 94 wk, 5 d, comprising a control group (C) (n = 144), which was fed a diet containing 0 ppm (mg/kg) of CP-31398; a low-dose treatment (LDT) group (n = 144), which was fed a diet containing 100 ppm of CP-31398; a moderate-dose treatment (MDT) group (n = 144) which was fed a diet containing 200 ppm of CP-31398; and a high-dose treatment (HDT) group (n = 144), which was fed a diet containing 300 ppm of CP-31398. Hens were killed at 174 wk of age to determine the incidence of ovarian and oviductal adenocarcinomas. Whereas the incidence of localized and metastatic ovarian cancers in the MDT and HDT groups was significantly lower (up to 77%) compared to levels in the C and LDT groups (P < 0.05), the incidence of oviductal cancer was unaffected by CP-31398. CP-31398 appears to be an effective tool for chemoprevention against ovarian malignancies, but does not appear to affect oviductal malignancies.

When the guardian sleeps: Reactivation of the p53 pathway in cancer

The p53 tumor suppressor is inactivated in most cancers, thus suggesting that loss of p53 is a prerequisite for tumor growth. Therefore, its reintroduction through different means bears great clinical potential. After a brief introduction to current knowledge of p53 and its regulation by the ubiquitin-ligases MDM2/MDMX and post-translational modifications, we will discuss small molecules that are able to reactivate specific, frequently observed mutant forms of p53 and their applicability for clinical purposes. Many malignancies display amplification of MDM genes encoding negative regulators of p53 and therefore much effort to date has concentrated on the development of molecules that inhibit MDM2, the most advanced of which are being tested in clinical trials for sarcoma, glioblastoma, bladder cancer and lung adenocarcinoma. These will be discussed as will recent findings of MDMX inhibitors: these are of special importance as it has been shown that cancers that become resistant to MDM2 inhibitors often amplify MDM4. Finally, we will also touch on gene therapy and vaccination approaches; the former of which aims to replace mutated TP53 and the latter whose goal is to activate the body's immune system toward mutant p53 expressing cells. Besides the obvious importance of MDM2 and MDMX expression for regulation of p53, other regulatory factors should not be underestimated and are also described. Despite the beauty of the concept, the past years have shown that many obstacles have to be overcome to bring p53 reactivation to the clinic on a broad scale, and it is likely that in most cases it will be part of a combined therapeutic approach. However, improving current p53 targeted molecules and finding the best therapy partners will clearly impact the future of cancer therapy.

TP53 modulating agent, CP-31398 enhances antitumor effects of ODC inhibitor in mouse model of urinary bladder transitional cell carcinoma

Mutations of the tumor suppressor p53 and elevated levels of polyamines are known to play key roles in urothelial tumorigenesis. We investigated the inhibition of polyamines biosynthesis and the restoration of p53 signaling as a possible means of preventing muscle invasive urothelial tumors using DFMO, an ODC-inhibiting agent, and CP-31398 (CP), a p53 stabilizing agent. Transgenic UPII-SV40T male mice at 6weeks age (n=15/group) were fed control diet (AIN-76A) or experimental diets containing DFMO (1000 and 2000 ppm) or 150 ppm CP or both. At 40 weeks of age, all mice were euthanized and urinary bladders were evaluated to determine tumor weight and histopathology. Low-dose DFMO had a moderate significant inhibitory effect on tumor growth (38%, P<0.02) and tumor invasion (23%). High-dose DFMO had a 47% tumor inhibition (P<0.0001) and 40% inhibition tumor invasion. There was no significant difference between 1000 and 2000 ppm doses of DFMO (P>0.05). CP at 150 ppm alone had a strong inhibitory effect on tumor growth by 80% (P<0.0001); however, no effect on tumor invasion was observed. Interestingly, the combination of DFMO (1000 ppm) and CP (150 ppm) led to significant decrease in tumor weight (70%, P<0.0001) and tumor invasion (62.5%; P<0.005). Molecular analysis of the urothelial tumors suggested a modulation of polyamine biosynthesis, proliferation, cell cycle regulators resulting from the use of these agents. These results suggest that targeting two or more pathways could be an effective approach for chemoprevention. A combination of CP and DFMO appears to be a promising strategy for urothelial TCC prevention.

CP-31398 prevents the growth of p53-mutated colorectal cancer cells in vitro and in vivo

Rescuing the function of mutant p53 protein is an attractive cancer therapeutic strategy. Small molecule CP-31398 was shown to restore mutant p53 tumor suppressor functions in cancer cells. Here, we determined the effects of CP-31398 on the growth of p53-mutated colorectal cancer (CRC) cells in vitro and in vivo. CRC cells which carry p53 mutation in codon 273 were treated with CP-31398 and the control, and the effects of CP-31398 on cell cycle, cell apoptosis, and proliferation were determined. The expression of p53-responsive downstream genes was evaluated by quantitative reverse transcriptase PCR (RT-PCR) and Western blot. CP-31398 was administrated into xenograft tumors created by the inoculation of HT-29 cells, and then the effect of CP-31398 on the growth of xenograft tumors was examined. CP-31398 induced p53 downstream target molecules in cultured HT-29 cells, which resulted in the inhibition of CRC cell growth assessed by the determination of cell cycle, apoptosis, and cell proliferation. In xenograft tumors, CP-31398 modulated the expression of Bax, Bcl-2, caspase 3, cyclin D, and Mdm2 and then blocked the growth of xenograft tumors. CP-31398 would be developed as a therapeutic candidate for p53-mutated CRC due to the restoration of mutant p53 tumor suppressor functions.

p53 modulates Hsp90 ATPase activity and regulates aryl hydrocarbon receptor signaling

The aryl hydrocarbon receptor (AhR), a client protein of heat shock protein 90 (Hsp90), is a ligand-activated transcription factor that plays a role in polycyclic aromatic hydrocarbon (PAH)-induced carcinogenesis. Tobacco smoke activates AhR signaling leading to increased transcription of CYP1A1 and CYP1B1, which encode proteins that convert PAHs to mutagens. Recently, p53 was found to regulate Hsp90 ATPase activity via effects on activator of Hsp90 ATPase (Aha1). It is possible, therefore, that AhR-dependent expression of CYP1A1 and CYP1B1 might be affected by p53 status. The main objective of this study was to determine whether p53 modulated AhR-dependent gene expression and PAH metabolism. Here, we show that silencing p53 led to elevated Aha1 levels, increased Hsp90 ATPase activity, and enhanced CYP1A1 and CYP1B1 expression. Overexpression of wild-type p53 suppressed levels of CYP1A1 and CYP1B1. The significance of Aha1 in mediating these p53-dependent effects was determined. Silencing of Aha1 led to reduced Hsp90 ATPase activity and downregulation of CYP1A1 and CYP1B1. In contrast, overexpressing Aha1 was associated with increased Hsp90 ATPase activity and elevated levels of CYP1A1 and CYP1B1. Using p53 heterozygous mutant epithelial cells from patients with Li-Fraumeni syndrome, we show that monoallelic mutation of p53 was associated with elevated levels of CYP1A1 and CYP1B1 under both basal conditions and following treatment with benzo[a]pyrene. Treatment with CP-31398, a p53 rescue compound, suppressed benzo[a]pyrene-mediated induction of CYP1A1 and CYP1B1 and the formation of DNA adducts. Collectively, our results suggest that p53 affects AhR-dependent gene expression, PAH metabolism, and possibly carcinogenesis.

p53 protein regulates Hsp90 ATPase activity and thereby Wnt signaling by modulating Aha1 expression

The p53 tumor suppressor gene encodes a homotetrameric transcription factor which is activated in response to a variety of cellular stressors, including DNA damage and oncogene activation. p53 mutations occur in >50% of human cancers. Although p53 has been shown to regulate Wnt signaling, the underlying mechanisms are not well understood. Here we show that silencing p53 in colon cancer cells led to increased expression of Aha1, a co-chaperone of Hsp90. Heat shock factor-1 was important for mediating the changes in Aha1 levels. Increased Aha1 levels were associated with enhanced interactions with Hsp90, resulting in increased Hsp90 ATPase activity. Moreover, increased Hsp90 ATPase activity resulted in increased phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β), leading to enhanced expression of Wnt target genes. Significantly, levels of Aha1, Hsp90 ATPase activity, Akt, and GSK3β phosphorylation and expression of Wnt target genes were increased in the colons of p53-null as compared with p53 wild type mice. Using p53 heterozygous mutant epithelial cells from Li-Fraumeni syndrome patients, we show that a monoallelic mutation of p53 was sufficient to activate the Aha1/Hsp90 ATPase axis leading to stimulation of Wnt signaling and increased expression of Wnt target genes. Pharmacologic intervention with CP-31398, a p53 rescue agent, inhibited recruitment of Aha1 to Hsp90 and suppressed Wnt-mediated gene expression in colon cancer cells. Taken together, this study provides new insights into the mechanism by which p53 regulates Wnt signaling and raises the intriguing possibility that p53 status may affect the efficacy of anticancer therapies targeting Hsp90 ATPase.

Chemopreventive effects of the p53-modulating agents CP-31398 and Prima-1 in tobacco carcinogen-induced lung tumorigenesis in A/J mice

Lung cancer is the leading cause of cancer deaths worldwide. Expression of the p53 tumor suppressor protein is frequently altered in tobacco-associated lung cancers. We studied chemopreventive effects of p53-modulating agents, namely, CP-31398 and Prima-1, on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung adenoma and adenocarcinoma formation in female A/J mice. Seven-week-old mice were treated with a single dose of NNK (10 µmol/mouse) by intraperitoneal injection and, 3 weeks later, were randomized to mice fed a control diet or experimental diets containing 50 or 100 ppm CP-31398 or 150 or 300 ppm Prima-1 for either 17 weeks (10 mice/group) or 34 weeks (15 mice/group) to assess the efficacy against lung adenoma and adenocarcinoma. Dietary feeding of 50 or 100 ppm CP-31398 significantly suppressed (P < .0001) lung adenocarcinoma by 64% and 73%, respectively, after 17 weeks and by 47% and 56%, respectively, after 34 weeks. Similarly, 150 or 300 ppm Prima-1 significantly suppressed (P < .0001) lung adenocarcinoma formation by 56% and 62%, respectively, after 17 weeks and 39% and 56%, respectively, after 34 weeks. Importantly, these results suggest that both p53 modulators cause a delay in the progression of adenoma to adenocarcinoma. Immunohistochemical analysis of lung tumors from mice exposed to p53-modulating agents showed a significantly reduced tumor cell proliferation and increased accumulation of wild-type p53 in the nucleus. An increase in p21- and apoptotic-positive cells was also observed in lung tumors of mice exposed to p53-modulating agents. These results support a chemopreventive role of p53-modulating agents in tobacco carcinogen-induced lung adenocarcinoma formation.

p53-stabilizing agent CP-31398 prevents growth and invasion of urothelial cancer of the bladder in transgenic UPII-SV40T mice

The high prevalence of bladder cancer and its recurrence make it an important target for chemoprevention. About half of invasive urothelial tumors have mutations in p53. We determined the chemopreventive efficacy of a p53-stabilizing agent, CP-31398, in a transgenic UPII-SV40T mouse model of bladder transitional cell carcinoma (TCC) that strongly resembles human TCC. After genotyping, six-week-old UPII-SV40T mice (n = 30/group) were fed control (AIN-76A) or experimental diets containing 150 or 300 ppm of CP-31398 for 34 weeks. Progression of bladder cancer growth was monitored by magnetic resonance imaging. At 40 weeks of age, all mice were killed; urinary bladders were collected to determine weights, tumor incidence, and histopathology. There was a significant increase in bladder weights of transgenic versus wild-type mice (male: 140.2 mg vs 27.3 mg, P < .0001; female: 34.2 mg vs 14.8 mg, P < .0001). A significant decrease in the bladder tumor weights (by 68.6-80.2%, P < .0001 in males and by 36.9-55.3%, P < .0001 in females) was observed in CP-31398-treated mice. Invasive papillary TCC incidence was 100% in transgenic mice fed control diet. Both male and female mice exposed to CP-31398 showed inhibition of invasive TCC. CP-31398 (300 ppm) completely blocked invasion in female mice. Molecular analysis of the bladder tumors showed an increase in apoptosis markers (p53, p21, Bax, and Annexin V) with a decrease in vascular endothelial growth factor in transgenic mice fed CP-31398. These results suggest that p53-modulating agents can serve as potential chemopreventive agents for bladder TCC.

Targeting the p53 pathway

This article summarizes data on translational studies to target the p53 pathway in cancer. It describes the functions of the p53 and Mdm-2 signaling pathways, and discusses current therapeutic approaches to target p53 pathways, including reactivation of p53. In addition, direct interaction and colocalization of the p53 and focal adhesion kinase proteins in cancer cells have been demonstrated, and different approaches to target this interaction are reviewed. This is a broad review of p53 function as it relates to the diagnosis and treatment of a wide range of cancers.

Genotoxicity of the cancer chemopreventive drug candidates CP-31398, SHetA2, and phospho-ibuprofen

The genotoxic activities of three cancer chemopreventive drug candidates, CP-31398 (a cell permeable styrylquinazoline p53 modulator), SHetA2 (a flexible heteroarotinoid), and phospho-ibuprofen (PI, a derivative of ibuprofen) were tested. None of the compounds were mutagenic in the Salmonella/Escherichia coli/microsome plate incorporation test. CP-31398 and SHetA2 did not induce chromosomal aberrations (CA) in Chinese hamster ovary (CHO) cells, either in the presence or absence of rat hepatic S9 (S9). PI induced CA in CHO cells, but only in the presence of S9. PI, its parent compound ibuprofen, and its moiety diethoxyphosphoryloxybutyl alcohol (DEPBA) were tested for CA and micronuclei (MN) in CHO cells in the presence of S9. PI induced CA as well as MN, both kinetochore-positive (Kin+) and -negative (Kin-), in the presence of S9 at ≤100μg/ml. Ibuprofen was negative for CA, positive for MN with Kin+ at 250μg/ml, and positive for MN with Kin- at 125 and 250μg/ml. DEPBA induced neither CA nor MN at ≤5000μg/ml. The induction of chromosomal damage in PI-treated CHO cells in the presence of S9 may be due to its metabolites. None of the compounds were genotoxic, in the presence or absence of S9, in the GADD45α-GFP Human GreenScreen assay and none induced MN in mouse bone marrow erythrocytes.

Pharmacokinetics and tissue and tumor exposure of CP-31398, a p53-stabilizing agent, in rats

PURPOSE

CP-31398 (N0-[2-[(E)-2-(4-methoxyphenyl)ethenyl] quinazolin-4-yl]-N,N-dimethylpropane-1,3-diamine hydrochloride) is one of the new class of agents that can stabilize the DNA-binding domain of p53 and thereby maintain the activity of p53 as a tumor suppressor and transcription factor. Through its activity as a p53 stabilizer, CP-31398 demonstrates significant cancer preventive and therapeutic activity in several in vivo animal models. The objective of the current study was to describe the pharmacokinetic profile and tissue distribution of this novel agent following intravenous or oral (gavage and dietary) administration.

METHODS

CP-31398 was administered to male CD and F344 rats as a single intravenous bolus dose or by daily oral gavage dosing. Male F344 rats also received drug as an ad libitum dietary supplement. Plasma, liver, skin, colon, and colon tumor samples were collected after oral dosing. Concentrations of CP-31398 in plasma and tissue samples were analyzed using LC–MS/MS, and the resultant data were subjected to a non-compartmental pharmacokinetic analysis.

RESULTS

Bioavailability (12–32%), elimination half-life (14–20 h), clearance (4.2–4.8 l/h/kg), and volume of distribution (70–82 l/kg) were determined. Tissue levels of CP-31398 after oral (gavage or diet) administration were several orders of magnitude higher than were corresponding plasma concentrations; CP-31398 levels were especially high in colon and liver. Levels of CP-31398 in tissues were higher after gavage dosing than after dietary administration.

CONCLUSIONS

CP-31398 is bioavailable and has a relatively long elimination half-life, which supports the achievement of plasma steady-state levels with a once daily dosing regimen. CP-31398 exhibits a dramatically high volume of distribution, which is consistent with its tissue concentrations being much higher than corresponding plasma levels. It is accumulated in colon tumor tissues, albeit at lower concentrations than found in liver, skin, and colon.

Translational approaches targeting the p53 pathway for anti-cancer therapy

The p53 tumour suppressor blocks cancer development by triggering apoptosis or cellular senescence in response to oncogenic stress or DNA damage. Consequently, the p53 signalling pathway is virtually always inactivated in human cancer cells. This unifying feature has commenced tremendous efforts to develop p53-based anti-cancer therapies. Different strategies exist that are adapted to the mechanisms of p53 inactivation. In p53-mutated tumours, delivery of wild-type p53 by adenovirus-based gene therapy is now practised in China. Also, remarkable progress has been made in the development of p53-binding drugs that can rescue and reactivate the function of mutant or misfolded p53. Other biologic approaches include the development of oncolytic viruses that are designed to specifically replicate in and kill p53-defective cells. Inactivation of wt-p53 frequently results from dysregulation of MDM2, an E3 ligase that regulates p53 levels. Small-molecule drugs that inhibit the interaction of MDM2 and p53 and block p53 degradation are currently tested in clinical trials. This survey highlights the recent developments that attempt to modulate the function of p53 and outlines strategies that are being investigated for pharmacological intervention in the p53 pathway.

Determination and stability of CP-31398 in plasma from experimental animals by LC-MS/MS

A sensitive and accurate approach for the determination of CP-31398 (N-{2-[(E)-2-(4-methoxy-phenyl)-vinyl]-quinazolin-4-yl}-N',N'-dimethyl-propane-1,3-diamine hydrochloride) in rat and dog plasma by LC-MS/MS was validated to support preclinical toxicological and pharmacological studies. Based on the results of stability experiments with diluted CP-31398 solutions using NMR, LC-MS/MS and LC-Q-TOF, all sample preparation and handling steps were performed under yellow light to avoid CP-31398 decomposition. CP-31398 was extracted by protein precipitation with acetonitrile and separated using a Phenomenex Luna 3μm phenyl-hexyl, 100Å, 30×2.0mm column (rat plasma) or a Phenomenex Synergi 4μ Polar-RP, 80Å, 30×2.0mm column (dog plasma) at a flow rate of 0.30mL/min. The mobile phase consisted of A: 1% formic acid in water and B: 1% formic acid in methanol or acetonitrile. Total run times for rat and dog samples were 7 and 8min, respectively, with accompanying retention times of 1.8 for both columns. A turbo ion spray interface was used as the ion source operating in positive mode. Calibration curves were linear from 5 to 1000ng/mL. Linearity was assessed using the external standard method. Within-run and between-run accuracy was 93-109% of the true value for all analytes with precision (SD) of 8% or less for all experiments. The validated method was applied to preclinical toxicology studies in rats and dogs after oral administration of CP-31398.

Subchronic oral toxicity and metabolite profiling of the p53 stabilizing agent, CP-31398, in rats and dogs

CP-31398 (N'-[2-[2-(4-methoxyphenyl)ethenyl]-4-quinazolinyl]-N,N-dimethyl-1,3-propanediamine dihydrochloride) is a styrylquinazoline that stabilizes the DNA binding conformation of p53, thereby maintaining the activity of p53 as a transcription factor and tumor suppressor. In consideration of the potential use of p53 stabilizers for cancer prevention and therapy, 28-day studies (with recovery) were performed to characterize the toxicity of CP-31398 in rats and dogs. In the rat study, groups of 15 CD rats/sex received daily gavage exposure to CP-31398 at 0, 40, 80, or 160mg/kg/day (0, 240, 480, or 960mg/m(2)/day). In the dog study, groups of five beagle dogs received daily gavage exposure to CP-31398 at 0, 10, 20, or 40mg/kg/day (0, 200, 400, or 800mg/m(2)/day). The high dose of CP-31398 induced mortality in both species: seven male rats and four female rats died as a result of hepatic infarcts, and two female dogs died as a result of hepatic necrosis without evidence of thrombosis. No deaths were seen in the mid- or low-dose groups in either species. In dogs, sporadic emesis was seen in the high dose and mid dose groups, and reductions in body weight gain were observed in all drug-exposed groups. CP-31398 induced mild anemia in both species; clinical pathology data also demonstrated hepatic toxicity, renal toxicity, inflammatory reactions, and coagulopathies in rats in the high dose and mid dose groups. Treatment-related microscopic changes in high dose and mid dose rats were identified in the liver, kidney, heart, bone marrow, lung, adrenals, spleen, thymus, skeletal muscle, and ovary; microscopic changes in the liver, heart, lung, and adrenals persisted through the recovery period. In dogs, microscopic changes were identified in the central nervous system, lung, and liver; changes in all tissues remained at the end of the recovery period. The liver is the primary site of limiting toxicity for CP-31398 in rats, and is also a key site of toxicity in dogs. The maximum tolerated dose (MTD) for subchronic oral administration of CP-31398 is 80mg/kg/day (480mg/m(2)/day) in rats and 20mg/kg/day (400mg/m(2)/day) in dogs. Although only modest and apparently reversible toxicities (microscopic changes in rats; reductions in body weight gain and alterations in red cell parameters in dogs) were seen in the low dose groups, no observed adverse effect levels (NOAELs) for CP-31398 could not be established for either species. The toxicity of CP-31398 suggests that this agent may not be suitable for use in cancer prevention. However, should in vivo antitumor efficacy be achievable at doses that do not induce limiting toxicity, CP-31398 may have utility as a cancer therapeutic. Modification of the primary sites of CP-31398 metabolism (N-demethylation of the alkyl side chain; hydroxylation and O-demethylation of the styryl benzene group) may result in the development of CP-31398 analogs with comparable pharmacologic activity and reduced toxicity.

Pharmacological activation of p53 in cancer cells

Tumor suppressor p53 is a transcription factor that regulates a large number of genes and guards against genomic instability. Under multiple cellular stress conditions, p53 functions to block cell cycle progression transiently unless proper DNA repair occurs. Failure of DNA repair mechanisms leads to p53-mediated induction of cell death programs. p53 also induces permanent cell cycle arrest known as cellular senescence. During neoplastic progression, p53 is often mutated and fails to efficiently perform these functions. It has been observed that cancers carrying a wild-type p53 may also have interrupted downstream p53 regulatory signaling leading to disruption in p53 functions. Therefore, strategies to reactivate p53 provide an attractive approach for blocking tumor pathogenesis and its progression. p53 activation may also lead to regression of existing early neoplastic lesions and therefore may be important in developing cancer chemoprevention protocols. A large number of small molecules capable of reactivating p53 have been developed and some are progressing through clinical trials for prospective human applications. However, several questions remain to be answered at this stage. For example, it is not certain if pharmacological activation of p53 will restore all of its multifaceted biological responses, assuming that the targeted cell is not killed following p53 activation. It remains to be demonstrated whether the distinct biological effects regulated by specific post-translationally modified p53 can effectively be restored by refolding mutant p53. Mutant p53 can be classified as a loss-of-function or gain-of-function protein depending on the type of mutation. It is also unclear whether reactivation of mutant p53 has similar consequences in cells carrying gain-of-function and loss-of-function p53 mutants. This review provides a description of various pharmacological approaches tested to activate p53 (both wild-type and mutant) and to assess the effects of activated p53 on neoplastic progression.

Corruption of homeostatic mechanisms in the guanylyl cyclase C signaling pathway underlying colorectal tumorigenesis

Colon cancer, the second leading cause of cancer-related mortality worldwide, originates from the malignant transformation of intestinal epithelial cells. The intestinal epithelium undergoes a highly organized process of rapid regeneration along the crypt-villus axis, characterized by proliferation, migration, differentiation and apoptosis, whose coordination is essential to maintaining the mucosal barrier. Disruption of these homeostatic processes predisposes cells to mutations in tumor suppressors or oncogenes, whose dysfunction provides transformed cells an evolutionary growth advantage. While sequences of genetic mutations at different stages along the neoplastic continuum have been established, little is known of the events initiating tumorigenesis prior to adenomatous polyposis coli (APC) mutations. Here, we examine a role for the corruption of homeostasis induced by silencing novel tumor suppressors, including the intestine-specific transcription factor CDX2 and its gene target guanylyl cyclase C (GCC), as early events predisposing cells to mutations in APC and other sequential genes that initiate colorectal cancer. CDX2 and GCC maintain homeostatic regeneration in the intestine by restricting cell proliferation, promoting cell maturation and adhesion, regulating cell migration and defending the intestinal barrier and genomic integrity. Elimination of CDX2 or GCC promotes intestinal tumor initiation and growth in aged mice, mice carrying APC mutations or mice exposed to carcinogens. The roles of CDX2 and GCC in suppressing intestinal tumorigenesis, universal disruption in their signaling through silencing of hormones driving GCC, and the uniform overexpression of GCC by tumors underscore the potential value of oral replacement with GCC ligands as targeted prevention and therapy for colorectal cancer.

Preclinical colorectal cancer chemopreventive efficacy and p53-modulating activity of 3',4',5'-trimethoxyflavonol, a quercetin analogue

Some naturally occurring flavonols, exemplified by quercetin, seem to possess experimental cancer chemopreventive efficacy. Modulation of p53 is a mechanism thought to contribute to their activity. The hypothesis was tested that a synthetic flavonol, 3',4',5'-trimethoxyflavonol (TMFol), can interfere with tumor development and p53 expression in two models of colorectal carcinogenesis, Apc(Min) mice and human-derived HCT116 adenocarcinoma-bearing nude mice. Mice received TMFol with their diet (0.2%) from weaning to week 16 in the case of Apc(Min) or from either day 7 before ("TMFol early") or day 7 after ("TMFol late") tumor inoculation in HCT116 mice. The ability of TMFol to affect tumor proliferation or apoptosis, as reflected by staining for Ki-67 or cleaved caspase-3, respectively, was studied in HCT116 tumors. TMFol tumor levels were measured by high-performance liquid chromatography. Consumption of TMFol reduced small intestinal adenoma burden in Apc(Min) mice by 47%, compared with control mice (P < 0.002). The TMFol early regimen approximately halved HCT116 tumor size (P < 0.05), decreased tumor proliferation, and increased apoptosis, whereas the TMFol late regimen had no significant effect when compared with controls. In tumor tissues from mice, in which TMFol reduced tumor development, p53 expression was increased 3-fold in Apc(Min) and 1.5-fold in HCT116 tumor-bearing mice (P = 0.02). TMFol increased p53 also in cells derived from these tumors. TMFol was detected in HCT116 tumors, but levels did not correlate with tumor burden. TMFol was not mutagenic in the Ames test. The results suggest that chemical modification of the flavonol structure may generate safe and efficacious cancer chemopreventive agents.

The p53 tumor suppressor: a master regulator of diverse cellular processes and therapeutic target in cancer

The tumor suppressor p53 has been implicated in a growing number of biological processes, including cell cycle arrest, senescence, apoptosis, autophagy, metabolism, and aging. Activation of p53 in response to oncogenic stress eliminates nascent tumor cells by apoptosis or senescence. p53 is regulated at the protein level by posttranslational modifications such as phosphorylation and acetylation. A p53 antisense gene, Wrap53, enhances p53 mRNA levels via the 5'UTR. Lack of Wrap53 transcripts that overlap with p53 abrogates the p53 DNA damage response. Around half of all human tumors carry p53 mutation that disrupt p53 specific DNA binding, and transcriptional transactivation of target genes. Reactivation of mutant p53 is a promising strategy for novel cancer therapy. The small molecule PRIMA-1 restores wild type conformation and DNA binding to mutant p53, induces mutant p53-dependent apoptosis, and inhibits tumor growth in vivo. The PRIMA-1 analog APR-246 is currently tested in a phase I clinical trial. Improved understanding of the p53 pathway should lead to better diagnosis and treatment of cancer in the future.

p53-based cancer therapy

Inactivation of p53 functions is an almost universal feature of human cancer cells. This has spurred a tremendous effort to develop p53 based cancer therapies. Gene therapy using wild-type p53, delivered by adenovirus vectors, is now in widespread use in China. Other biologic approaches include the development of oncolytic viruses designed to replicate and kill only p53 defective cells and also the development of siRNA and antisense RNA's that activate p53 by inhibiting the function of the negative regulators Mdm2, MdmX, and HPV E6. The altered processing of p53 that occurs in tumor cells can elicit T-cell and B-cell responses to p53 that could be effective in eliminating cancer cells and p53 based vaccines are now in clinical trial. A number of small molecules that directly or indirectly activate the p53 response have also reached the clinic, of which the most advanced are the p53 mdm2 interaction inhibitors. Increased understanding of the p53 response is also allowing the development of powerful drug combinations that may increase the selectivity and safety of chemotherapy, by selective protection of normal cells and tissues.

Therapeutic targeting of p53 by small molecules

Aberrant p53 function is one of the major requirements for tumor development. Reactivation of p53 function by small molecules is a promising strategy to combat cancer due to potent tumor suppressor activities of p53. Recent developments in p53 biology reveal that manipulation of p53 function might pave way to a long cancer-free life. A number of small molecules which rescue p53 function by different mechanisms, acting upstream of p53 or targeting the p53 protein itself have been identified. Notably, these molecules trigger different biological outcomes, suggesting that it might be feasible to direct p53-mediated response in a desired way. In this review I discuss the latest developments in the search for small molecules which rescue p53 function by targeting the p53 protein.

Anthocyanin-rich red grape extract impedes adenoma development in the Apc(Min) mouse: pharmacodynamic changes and anthocyanin levels in the murine biophase

PURPOSE

Red grape pomace extract (oenocyanin) is a cheap and rich source of anthocyanins, the agents suggested to possess cancer chemopreventive properties. Here the hypothesis was tested that oenocyanin added to the diet can interfere with intestinal adenoma development in the Apc(Min) mouse, a model of intestinal carcinogenesis linked to an Apc mutation.

METHODS

Mice received oenocyanin (0.3%) in their diet until week 16, when adenoma number and burden were recorded. Expression of Akt and ERK proteins was studied by Western blot in adenomas to discover effects of anthocyanins on cellular signalling via the PI3 and MAP kinase pathways. Levels of anthocyanins were measured by HPLC with visible spectroscopic or mass spectrometric detection.

RESULTS

In mice which had consumed oenocyanin, overall adenoma burden was halved and adenoma number was marginally reduced when compared with mice on control diet. The proliferation index in colonic adenomatous crypts, as reflected by Ki-67 staining, was significantly decreased from 88.14% in control mice to 75.6+/-4% in mice on oenocyanin (P=0.014). Expression of Akt in small intestinal adenomas from Apc(Min) mice on oenocyanin was reduced by 54% (P=0.003), when compared to controls. Oenocyanin anthocyanins and glucuronide metabolites were found in the urine and intestine but not in plasma.

CONCLUSIONS

The results suggest that oenocyanin may be a viable and economical alternative to anthocyanin-rich berry extracts for chemopreventive intervention. Akt and pErk might be suitable biomarkers of anthocyanin target organ efficacy.

Inhibition of azoxymethane-induced colorectal cancer by CP-31398, a TP53 modulator, alone or in combination with low doses of celecoxib in male F344 rats

Tumor suppressor p53 plays a major role in colorectal cancer development. The present study explores the effects of p53-modulating agent CP-31398 alone and combined with celecoxib on azoxymethane-induced aberrant crypt foci (ACF) and colon adenocarcinomas in F344 rats. Maximum tolerated doses were 400 and 3,000 ppm for CP-31398 and celecoxib, respectively. ACF and tumor efficacy endpoints were carried out on azoxymethane-treated 7-week-old rats (48 per group) fed the control AIN-76A diet. Two weeks after carcinogen treatment, rats were fed the diets containing 0, 150, or 300 ppm CP-31398, 300 ppm celecoxib, or 150 ppm CP-31398 plus 300 ppm celecoxib. ACF and colon adenocarcinomas were determined at 8 and 48 weeks after azoxymethane treatment, respectively. Dietary CP-31398 was shown to suppress mean colonic total ACF by 43% and multicrypt ACF by 63%; dietary CP-31398 at 150 and 300 ppm suppressed adenocarcinoma incidence by 30.4% (P < 0.02) and 44% (P < 0.005), respectively, and adenocarcinoma multiplicity by 51% (P < 0.005) and 65% (P < 0.0001), respectively. Dietary celecoxib suppressed colon adenocarcinoma incidence (60%; P < 0.0003) and multiplicity (70%; P < 0.0001). Importantly, combination of low-dose CP-31398 and celecoxib suppressed colon adenocarcinoma incidence by 78% and multiplicity by 90%. Rats that were fed the high-dose CP-31398 or a combination of low-dose CP-31398 and celecoxib showed considerable enhancement of p53 and p21(WAF1/CIP) expression, apoptosis, and reduced tumor cell proliferation in colonic tumors. These observations show, for the first time, that CP-31398 possesses significant dose-dependent chemopreventive activity in a well-established colon cancer model and that a combination of low-dose CP-31398 and celecoxib significantly enhanced colon cancer chemopreventive efficacy.

Flavones as colorectal cancer chemopreventive agents--phenol-o-methylation enhances efficacy

Flavonoids occur ubiquitously in plants, and some possess preclinical cancer chemopreventive activity. Little is known about molecular features that mediate chemopreventive efficacy of flavonoids. Here, three related flavones, apigenin (4',5,7-trihydroxyflavone), tricin (4',5,7-trihydroxy-3',5'-dimethoxyflavone), and 3',4',5',5,7-pentamethoxyflavone (PMF), were compared in terms of their effects on (a) adenoma development in Apc(Min) mice, a model of human gastrointestinal malignancies; (b) growth of APC10.1 mouse adenoma cells in vitro; and (c) prostaglandin E-2 generation in HCA-7 human-derived colorectal cancer cells in vitro. Life-long consumption of PMF with the diet at 0.2% reduced Apc(Min) mouse adenoma number and burden by 43% and 61%, respectively, whereas apigenin was inactive. Tricin has previously shown activity in this model. IC50 values for murine adenoma cell growth inhibition by PMF, tricin, and apigenin were 6, 13, and 18 micromol/L, respectively. In Apc(Min) mice that received flavones (0.2%) for 4 weeks, adenoma cell proliferation as reflected by Ki-67 staining was reduced by PMF and tricin, but not by apigenin. On incubation with HCA-7 cells for 6 hours, PMF reduced prostaglandin E-2 generation with an IC50 of 0.8 micromol/L, a fraction of the respective values reported for tricin or apigenin. In silico PMF docked into the cyclooxygenase active site with greater affinity than tricin or apigenin. The results suggest that the rank order of cancer chemopreventive efficacy in Apc(Min) mice is PMF > tricin > apigenin, supporting the notion that the presence of O-methyl in the flavone molecular scaffold promotes gastrointestinal cancer chemopreventive efficacy.

Apoptosis and colorectal cancer: implications for therapy

Colorectal cancer (CRC) is characterized by the partial suppression of apoptosis, which in turn gives tumours a selective advantage for survival and can cause current chemotherapy approaches to be ineffective. Recent progress in understanding the mechanisms of apoptosis in colorectal carcinogenesis has provided potential new targets for therapy. Here, we review recent studies of the regulation of apoptosis and its role in CRC initiation and progression, and we discuss the relationship between chemoresistance and the suppression of apoptosis. Recent progress in targeting apoptotic pathways and their regulators provide strategies for the exploration of novel therapies for CRC.