Zinc stabilizes adenomatous polyposis coli (APC) protein levels and induces cell cycle arrest in colon cancer cells

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Zinc intake, SLC30A8 rs3802177 polymorphism, and colorectal cancer risk in a Korean population: a case-control study

PURPOSE

Zinc is an essential micronutrient involving in multiple enzymatic reactions of human metabolism and biological functions affecting the cancer development. However, the relationship between dietary zinc intake and colorectal cancer (CRC) risk has been unclear. Herein, our study investigated the relationship between dietary zinc intake and CRC risk, and examined how the SLC30A8 rs3802177 genetic variant affects this association.

METHODS

A total of 1431 CRC cases and 2704 controls were selected to investigate the relationship between dietary zinc intake and CRC risk. After excluding individuals without genotype data, 1097 CRC cases and 1559 controls were used to evaluate the interaction between dietary zinc intake and the rs3802177 polymorphism in CRC risk. The odds ratios (ORs) and 95% confidence intervals (CIs) were measured using unconditional logistic regression models.

RESULTS

Higher dietary zinc intake was inversely associated with the risk of CRC in the total population [adjusted OR (aOR) = 0.80, 95% CI 0.66-0.96, p for trend = 0.018]. In the codominant model, G+ carriers of the SLC30A8 rs3802177 with higher consumption of zinc were observed to have a significantly lower risk of CRC in all participants (p for interaction = 0.020). In females, GG carriers with higher zinc intake showed a stronger protective effect against the development of CRC (p for interaction = 0.008).

CONCLUSIONS

In summary, our findings suggest an inverse association between dietary zinc intake and CRC risk, and this relationship may be modified by SLC30A8 rs3802177 polymorphism.

Interplay between zinc and cell proliferation and implications for the growth of livestock

Zinc (Zn) plays a critical role in the growth of livestock, which depends on cell proliferation. In addition to modifying the growth associated with its effects on food intake, mitogenic hormones, signal transduction and gene transcription, Zn also regulates body weight gain through mediating cell proliferation. Zn deficiency in animals leads to growth inhibition, along with an arrest of cell cycle progression at G0/G1 and S phase due to depression in the expression of cyclin D/E and DNA synthesis. Therefore, in the present study, the interplay between Zn and cell proliferation and implications for the growth of livestock were reviewed, in which Zn regulates cell proliferation in several ways, especially cell cycle progression at the G0/G1 phase DNA synthesis and mitosis. During the cell cycle, the Zn transporters and major Zn binding proteins such as metallothioneins are altered with the requirements of cellular Zn level and nuclear translocation of Zn. In addition, calcium signaling, MAPK pathway and PI3K/Akt cascades are also involved in the process of Zn-interfering cell proliferation. The evidence collected over the last decade highlights the necessity of Zn for normal cell proliferation, which suggests Zn supplementation should be considered for the growth and health of poultry.

The Role of Chosen Essential Elements (Zn, Cu, Se, Fe, Mn) in Food for Special Medical Purposes (FSMPs) Dedicated to Oncology Patients-Critical Review: State-of-the-Art

The scoping review aimed to characterise the role of selected essential elements (Zn, Cu, Se, Fe, Mn) in food for special medical purposes (FSMPs) aimed at oncology patients. The scope review was conducted using Scopus, Google Scholar, and Web of Science to find published references on this subject. Data from the reviewed literature were related to the physiological functions of the element in the body, and the effects of deficiencies and excesses, referring to the latest ESPEN and EFSA guidelines, among others. Important dietary indices/parameters based on the literature review are provided for each element. On the basis of the literature, data on the level of elements in patients with cancer were collected. The content of these elements in 100 mL of FSMPs was read from the manufacturers' declarations. The literature has been provided on the importance of each element in cancer. Our findings show that the essential elements (Zn, Cu, Se, Fe, and Mn) of FSMPs for cancer patients are not adequately treated. We suggest solutions to ensure the safe use of FSMPs in oncology patients.

Antitumor Effect of Zinc Acetate in Hepatocellular Carcinoma Cell Lines via the Induction of Apoptosis

We aimed to verify antitumor effects of zinc acetate on hepatocellular carcinoma (HCC) in vitro. Five HCC cell lines (HepG2, Hep3B, Huh7, HLE and Alex) were used to evaluate the antitumor effects of zinc acetate. Cell viability was determined by the Cell Counting Kit-8 assay. The cell-cycle alteration was evaluated by a flow cytometric analysis and the detection of cell cycle-related proteins. Apoptosis was determined based on the caspase-cleaved cytokeratin 18 (cCK18) levels. The microRNAs (miRNAs) related to an antitumor effect of zinc acetate were identified using microarrays. Zinc acetate significantly inhibited the proliferation of HCC cells in a dose-dependent manner. The treatment with zinc acetate resulted in significantly increased cCK18 levels in the supernatant and enhanced the expression of heme oxygenase-1 (HO-1) in HCC cells. The flow cytometric analysis revealed an increase of HCC cells in the S and G₂/M phases by the administration of zinc acetate, and the expressions of Cdk2 and cyclin E were increased. The miRNA expression profile of the HCC cells treated with zinc acetate was extremely different from that of the untreated HCC cells. These results suggest that the zinc acetate supplementation induces the apoptosis of HCC cells, but does not affect the cell cycle progression. Upregulation of HO-1 and the alteration of miRNAs' profile may be involved in antitumor effects of zinc acetate in HCC cells.

Micronutrient Food Supplements in Patients with Gastro-Intestinal and Hepatic Cancers

Colorectal carcinogenesis is the second most common cause of mortality across all types of malignancies, followed by hepatic and stomach cancers. Chemotherapy and radiotherapy are key approaches to treating cancer patients, but these carry major concerns, such as a high risk of side effects, poor accessibility, and the non-selective nature of chemotherapeutics. A number of natural products have been identified as countering various forms of cancer with fewer side effects. The potential impact of vitamins and minerals on long-term health, cognition, healthy development, bone formation, and aging has been supported by experimental and epidemiological studies. Successful treatment may thus be highly influenced by the nutritional status of patients. An insufficient diet could lead to detrimental effects on immune status and tolerance to treatment, affecting the ability of chemotherapy to destroy cancerous cells. In recent decades, most cancer patients have been taking vitamins and minerals to improve standard therapy and/or to decrease the undesirable side effects of the treatment together with the underlying disease. On the other hand, taking dietary supplements during cancer therapy may affect the effectiveness of chemotherapy. Thus, micronutrients in complementary oncology must be selected appropriately and should be taken at the right time. Here, the potential impact of micronutrients on gastro-intestinal and hepatic cancers is explored and their molecular targets are laid down.

Zinc Gluconate Induces Potentially Cancer Chemopreventive Activity in Barrett's Esophagus: A Phase 1 Pilot Study

BACKGROUND

Chemopreventive effects of zinc for esophageal cancer have been well documented in animal models. This prospective study explores if a similar, potentially chemopreventive action can be seen in Barrett's esophagus (BE) in humans.

AIMS

To determine if molecular evidence can be obtained potentially indicating zinc's chemopreventive action in Barrett's metaplasia.

METHODS

Patients with a prior BE diagnosis were placed on oral zinc gluconate (14 days of 26.4 mg zinc BID) or a sodium gluconate placebo, prior to their surveillance endoscopy procedure. Biopsies of Barrett's mucosa were then obtained for miRNA and mRNA microarrays, or protein analyses.

RESULTS

Zinc-induced mRNA changes were observed for a large number of transcripts. These included downregulation of transcripts encoding proinflammatory proteins (IL32, IL1β, IL15, IL7R, IL2R, IL15R, IL3R), upregulation of anti-inflammatory mediators (IL1RA), downregulation of transcripts mediating epithelial-to-mesenchymal transition (EMT) (LIF, MYB, LYN, MTA1, SRC, SNAIL1, and TWIST1), and upregulation of transcripts that oppose EMT (BMP7, MTSS1, TRIB3, GRHL1). miRNA arrays showed significant upregulation of seven miRs with tumor suppressor activity (-125b-5P, -132-3P, -548z, -551a, -504, -518, and -34a-5P). Of proteins analyzed by Western blot, increased expression of the pro-apoptotic protein, BAX, and the tight junctional protein, CLAUDIN-7, along with decreased expression of BCL-2 and VEGF-R2 were noteworthy.

CONCLUSIONS

When these mRNA, miRNA, and protein molecular data are considered collectively, a cancer chemopreventive action by zinc in Barrett's metaplasia may be possible for this precancerous esophageal tissue. These results and the extensive prior animal model studies argue for a future prospective clinical trial for this safe, easily-administered, and inexpensive micronutrient, that could determine if a chemopreventive action truly exists.

Colorectal cancer and trace elements alteration

BACKGROUND

Trace elements have important influence on body function primarily because of the vital role they have in many physiological processes. Their alterations have been found in many disorders, including cancer. It has been well known for decades that disturbances in elemental concentration may lead to cell damaging, DNA injuries and imbalance in oxidative burden. Our study tried to determine the difference of trace elements concentrations between colorectal adenocarcinoma and adjacent healthy intestinal tissue.

METHODS

59 subjects participated in this study. Healthy colon mucosa samples and colon tumor tissue samples were obtained from patients previously diagnosed with colon carcinoma by standard diagnostic procedures. Analysis of the elements was performed by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

The results showed that Na, K, Mg, Ca, Cu, Zn, Se, Mn, Cd, Cr and Hg significantly differ between malignant tissue of colorectal cancer (CRC) and adjacent healthy bowel tissue. We have, also, found that Cu/Zn tissue ratio was significantly higher in CRC compared to a healthy tissue and that patients with higher CRC stages had also significantly higher ratio.

CONCLUSIONS

Since this is the first such study in Balkan region, we assume that results of our study could be a good indicator of elemental alterations in colorectal cancer of Balkan population, due to similarity in lifestyle, dietary intake, pollution and exposure to toxic elements.

The Role of Carcinogenesis-Related Biomarkers in the Wnt Pathway and Their Effects on Epithelial-Mesenchymal Transition (EMT) in Oral Squamous Cell Carcinoma

As oral squamous cell carcinoma (OSCC) can develop from potentially malignant disorders (PMDs), it is critical to develop methods for early detection to improve the prognosis of patients. Epithelial-mesenchymal transition (EMT) plays an important role during tumor progression and metastasis. The Wnt signaling pathway is an intercellular pathway in animals that also plays a fundamental role in cell proliferation and regeneration, and in the function of many cell or tissue types. Specific components of master regulators such as epithelial cadherin (E-cadherin), Vimentin, adenomatous polyposis coli (APC), Snail, and neural cadherin (N-cadherin), which are known to control the EMT process, have also been implicated in the Wnt cascade. Here, we review recent findings on the Wnt signaling pathway and the expression mechanism. These regulators are known to play roles in EMT and tumor progression, especially in OSCC. Characterizing the mechanisms through which both EMT and the Wnt pathway play a role in these cellular pathways could increase our understanding of the tumor genesis process and may allow for the development of improved therapeutics for OSCC.

Zinc Inhibits Expression of Androgen Receptor to Suppress Growth of Prostate Cancer Cells

The prostate gland contains a high level of intracellular zinc, which is dramatically diminished during prostate cancer (PCa) development. Owing to the unclear role of zinc in this process, therapeutic applications using zinc are limited. This study aimed to clarify the role of zinc and its underlying mechanism in the growth of PCa. ZnCl₂ suppressed the proliferation of androgen receptor (AR)-retaining PCa cells, whereas it did not affect AR-deficient PCa cells. In LNCaP and TRAMP-C2 cells, zinc downregulated the expression of AR in a dose- and time-dependent fashion. Zinc-mediated AR suppression accordingly inhibited the androgen-mediated transactivation and expression of the androgen target, prostate specific antigen (PSA). This phenomenon resulted from facilitated protein degradation, not transcriptional control. In studies using mice bearing TRAMP-C2 subcutaneous tumors, the intraperitoneal injection of zinc significantly reduced tumor size. Analyses of both xenograft tumors and normal prostates showed reduced expression of AR and increased cell death. Considering the significant loss of intracellular zinc and the dominant growth-modulating role of AR during PCa development, loss of zinc may be a critical step in the transformation of normal cells to cancer cells. This study provides the underlying mechanism by which zinc functions as a PCa suppressor, and forms the foundation for developing zinc-mediated therapeutics for PCa.

Co‑expression of Axin and APC gene fragments inhibits colorectal cancer cell growth via regulation of the Wnt signaling pathway

Adenomatous polyposis coli (APC) and Axin interactions serve an important role in colorectal cancer (CRC) pathogenesis. The aim of the present study was to assess the combined effects of Axin and APC co-expression in CRC cells, and to determine the underlying mechanisms involved. SW480 cells were divided into the following groups: Untransfected (SW480 group), transfected with pEGFP-N₃plus pCS2-MT (SW480/vector-vector), transfected with pEGFP-N₃-APC5 (SW480/APC5), and transfected with pEGFP-N₃-APC5 pluspCS2-MT-Axin (SW480/APC5-Axin). APC5 and Axin mRNA levels were determined by reverse transcription-polymerase chain reaction. MTT assays and flow cytometry analysis were performed to assess cell growth and cell cycle distribution, respectively. Quantitative PCR and western blot analyses were conducted to evaluate the mRNA and protein levels, respectively, of Wnt signaling effectors, including β-catenin, c-myc and survivin. Successful transfection of SW480 cells was determined with APC and APC-Axin plasmids as indicated by the green fluorescence signals. Notably, SW480/APC5 cell growth was inhibited by 40.33%, and cells co-expressing APC5 and Axin demonstrated 61.27% inhibition of cell growth compared with SW480 control cells. The results demonstrate that APC5 may induce G1/S arrest in SW480 cells, and Axin may enhance cell growth arrest induced by APC5. The mRNA and protein levels of β-catenin, c-myc and survivin were significantly reduced in SW480/APC-Axin cells when compared with the SW480/APC group. In conclusion, co-expression of APC5 and Axin genes significantly downregulated Wnt signaling in human SW480 CRC cells and inhibited cell growth, when compared with cells transfected with APC5 alone. These results may provide experimental evidence to support combined gene therapy in CRC.

Low zinc environment induces stress signaling, senescence and mixed cell death modalities in colon cancer cells

Currently it is not clear what type of the final cellular response (i.e. cell death modality or senescence) is induced upon chronic intracellular zinc depletion in colon cancer cells. To address this question, isogenic colon cancer lines SW480 and SW620 exposed to low zinc environment were studied over the period of 6 weeks. Low zinc environment reduced total as well as free intracellular zinc content in both cell lines. Decreased intracellular zinc content resulted in changes in cellular proliferation, cell cycle distribution and activation of stress signaling. In addition, colonocytes with low zinc content displayed increased levels of oxidative stress, changes in mitochondrial activity but in the absence of significant DNA damage. Towards the end of treatment (4th-6th week), exposed cells started to change morphologically, and typical markers of senescence as well as cell death appeared. Of two examined colon cancer cell lines, SW480 cells proved to activate predominantly senescent phenotype, with frequent form of demise being necrosis and mixed cell death modality but not apoptosis. Conversely, SW620 cells activated mostly cell death, with relatively equal distribution of apoptosis and mixed types, while senescent phenotypes and necrosis were present only in a small fraction of cell populations. Addition of zinc at the beginning of 4th week of treatment significantly suppressed cell death phenotypes in both cell lines but had no significant effect on senescence. In conclusion, presented results demonstrate variability of responses to chronic zinc depletion in colon cancer as modeled in vitro.

Zinc in gut-brain interaction in autism and neurological disorders

A growing amount of research indicates that abnormalities in the gastrointestinal (GI) system during development might be a common factor in multiple neurological disorders and might be responsible for some of the shared comorbidities seen among these diseases. For example, many patients with Autism Spectrum Disorder (ASD) have symptoms associated with GI disorders. Maternal zinc status may be an important factor given the multifaceted effect of zinc on gut development and morphology in the offspring. Zinc status influences and is influenced by multiple factors and an interdependence of prenatal and early life stress, immune system abnormalities, impaired GI functions, and zinc deficiency can be hypothesized. In line with this, systemic inflammatory events and prenatal stress have been reported to increase the risk for ASD. Thus, here, we will review the current literature on the role of zinc in gut formation, a possible link between gut and brain development in ASD and other neurological disorders with shared comorbidities, and tie in possible effects on the immune system. Based on these data, we present a novel model outlining how alterations in the maternal zinc status might pathologically impact the offspring leading to impairments in brain functions later in life.

Zinc and gastrointestinal disease

This review is a current summary of the role that both zinc deficiency and zinc supplementation can play in the etiology and therapy of a wide range of gastrointestinal diseases. The recent literature describing zinc action on gastrointestinal epithelial tight junctions and epithelial barrier function is described. Zinc enhancement of gastrointestinal epithelial barrier function may figure prominently in its potential therapeutic action in several gastrointestinal diseases.

hZIP1 that is down-regulated in clear cell renal cell carcinoma is negatively associated with the malignant potential of the tumor

OBJECTIVE

The human ZRT, IRT-like protein 1 (hZIP1) has been associated with tumorigenesis. However, its role in clear cell renal cell carcinoma (ccRCC) has not been yet reported. The objective was to investigate hZIP1 expression in ccRCC and its association with clinicopathological features.

MATERIALS AND METHODS

A total of 106 ccRCC tissue samples and corresponding normal kidney tissue samples were examined, along with 3 ccRCC cell lines (ACHN, 769-P, and 786-O). Real-time polymerase chain reaction, Western blot, and immunohistochemistry were used to investigate the expression of hZIP1 and its relationship with clinicopathological features. The ACHN cell line, exhibiting the highest hZIP1 expression, was transfected with hZIP1 small interfering RNA or mock small interfering RNA. Cellular proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Invasion was determined by Transwell assay.

RESULTS

The level of hZIP1 was decreased in ccRCC tissues when compared with normal tissues. hZIP1 expression significantly decreased with increasing clinical stage and pathological grade in ccRCC samples (P<0.05), showing a significant negative correlation with the histological grade (P<0.05). High hZIP1 expression was associated with a better disease-free survival (P<0.01). Silencing of hZIP1 expression enhanced the proliferative and invasive abilities of ACHN cells.

CONCLUSIONS

Results suggest that hZIP1 may act as a tumor suppressor in ccRCC. hZIP1 is closely correlated with clinicopathological features. High hZIP1 expression may be an indicator of good prognosis in ccRCC.

Lack of protective effects of zinc gluconate against rat colon carcinogenesis

Zinc has been proposed as a promising chemopreventive candidate against colon cancer. However, few studies on the potential beneficial effects of this trace element on cancer chemoprevention are available. The present study was designed to investigate the potential modifying influence of zinc gluconate (ZnGly) on the initiation step of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Male Wistar rats received orally ZnGly (15 mg elemental zinc/kg, 3 times per wk) 2 wk before and during DMH treatment (3 × 40 mg/kg, once a wk). The animals were euthanized at the end of 4th and 16th wk. Colons were analyzed for aberrant crypt foci (ACF) and tumor development. Blood and colon zinc levels, cell proliferation, and apoptosis indexes in colonic crypts were analyzed 24 h after the last DMH administration. Oral treatment with ZnGly did neither alter the number of ACF nor the indexes of cell proliferation and apoptosis in the colonic mucosa. The incidence and multiplicity of colon tumors induced by DMH and their histopathological patterns were not modified by previous treatment with ZnGly. These findings indicate a lack of chemopreventive action of zinc gluconate supplementation on the initiation step of rat colon carcinogenesis induced by DMH.

Naringin accelerates the regression of pre-neoplastic lesions and the colorectal structural reorganization in a murine model of chemical carcinogenesis

The aim of this study was to investigate the effect of Naringin on pre-neoplastic colorectal lesions induced by chemical carcinogen in rats. Female Wistar rats weighing 130.8±27.1 g received weekly one subcutaneous injection of 1,2-dimethylhydrazine (DMH, 20 mg/kg) for 10 weeks. The animals were divided into 5 groups with 6 animals in each group. Group 1: 0.9% saline; Group 2: DMH+0.9% saline; Group 3: DMH+Naringin (10 mg/kg); Group 4: DMH+Naringin (100 mg/kg); Group 5: DMH+Naringin (200 mg/kg). G2 and G3 showed a significant increase in ACF number, AgNOR/nucleus and mitosis compared to G1. G4 and G5 presented a significant reduction in these parameters compared to G2. The number of cells producing acidic and neutral mucins, red blood cells and the level of antioxidant minerals, such as copper, magnesium, selenium and zinc, were significantly reduced in G2 and G3, but similar in G4 and G5 compared to G1. Naringin, especially at 200 mg/kg, was effective in reducing the number of pre-neoplastic lesions in rats exposed to DMH. Some of these effects may be due to reduction in cellular proliferation and tissue levels of iron together with the recovery of antioxidant mineral levels induced by this flavonoid.

Association between zinc intake and risk of digestive tract cancers: a systematic review and meta-analysis

BACKGROUND & AIMS

Association between zinc intake and digestive tract cancers risk has been reported in several epidemiological studies, while the results were controversial. The aim of our study was to get a systemic review of this issue.

METHODS

PUBMED and EMBASE were searched up to April 2013, supplemented with manual-screening for relevant articles. Two independent reviewers independently extracted data from eligible studies, risk ratio (RR) or odds ratio (OR) with 95% CIs for the highest versus lowest categories of zinc intake was adopted. Either a fixed- or a random-effects model was adopted to estimate overall odds ratios. Besides, dose-response, subgroup, and publication bias analyses were applied.

RESULTS

Nineteen studies with approximately 400,000 participants were included in this meta-analysis. The pooled relative risk (RR) of overall digestive tract cancers for the highest versus lowest categories of zinc intake was 0.82 (95% CI: 0.70-0.96; p = 0.013). Comparing the highest with lowest categories, higher zinc intake was significantly associated with reduced colorectal cancer risk (pooled RR = 0.80, 95% CI: 0.70-0.92; p = 0.002), while zinc intake was not statistically associated with gastric cancer risk (pooled RR = 0.91, 95% CI: 0.64-1.29; p = 0.581) or esophageal cancer risk (pooled RR = 0.72, 95% CI: 0.44-1.17; p = 0.187). However, subgroup analyses showed that zinc intake was significantly associated with esophageal cancer risk and gastric cancer risk in Asia, but not in America and Europe.

CONCLUSIONS

Dietary zinc intake was inversely associated with digestive tract cancers, especially colorectal cancer risk in this study.

Apc regulates the function of hematopoietic stem cells largely through β-catenin-dependent mechanisms

Emerging evidence suggests that adenomatous polyposis coli (Apc) plays a critical role in the maintenance of hematopoietic stem/progenitor cells (HSCs/HPCs). The molecular pathways responsible for the function of Apc in HSCs/HPCs remain unclear. By genetic approach, we demonstrated that inactivation of β-catenin rescued the exhaustion of Apc-deficient HSCs/HPCs, thereby preventing bone marrow failure in Apc-deficient mice. β-catenin loss inhibited the excessive proliferation and apoptosis of Apc-deficient HSCs/HPCs, as well as their defects in myeloid and erythroid differentiation. In addition, loss of β-catenin reversed the down-regulation of Cdkn1a, Cdkn1b, and Mcl1 induced by Apc ablation in Lin(-)Sca(+)c-Kit(+). In assays of long-term stem cell function, the HSCs with deficiency of both Apc and β-catenin displayed a significantly enhanced self-renewal capacity compared with β-catenin-deficient and control HSCs. Our findings suggest that Apc regulates the survival, proliferation, and differentiation of HSCs/HPCs largely through a β-catenin-mediated pathway. They also indicate that multiple downstream targets of Apc including β-catenin may coordinately regulate HSC self-renewal.

The flavonoid chrysin attenuates colorectal pathological remodeling reducing the number and severity of pre-neoplastic lesions in rats exposed to the carcinogen 1,2-dimethylhydrazine

Phenolic compounds are naturally occurring, bioactive substances with marked antioxidant and anti-inflammatory potential. The flavonoid chrysin, found in high levels in honey bee propolis, inhibits the activity of enzymes involved in carcinogenesis. We have investigated the effect of chrysin on pre-neoplastic colorectal lesions (ACF, aberrant crypt foci) in a rat model of chemical carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Female Wistar rats weighing 137.2 ± 24.3 g received weekly one subcutaneous injection of DMH (20 mg/kg) for 10 weeks. The animals were divided into five groups each with seven animals: Group 1, 0.9% saline; Group 2, DMH+0.9% saline; Group 3, DMH+chrysin (10 mg/kg); Group 4, DMH+chrysin (100 mg/kg); Group 5, DMH+chrysin (200 mg/kg). Groups 2 and 3 showed a significant increase in ACF number, nucleolus organizer regions per enterocyte nucleus and nitrite/nitrate serum levels compared with Group 1. Groups 4 and 5 presented a significant reduction in all these parameters compared with Group 2. The levels of antioxidant minerals (copper, magnesium, selenium, zinc) and the number of enteroendocrine and mucin-producing cells were significantly reduced in Groups 2 and 3 but were similar in Groups 4 and 5 compared with Group 1. Chrysin, at 100 mg/kg and 200 mg/kg, was effective in attenuating pathological colorectal remodeling, reducing the number of pre-neoplastic lesions in rats exposed to DMH. Some of these effects might be attributable to the recovery of antioxidant mineral levels, a reduction in systemic nitrosative stress and an inhibition of the cellular proliferation induced by this flavonoid.

Inhibition by zinc of deoxycholate-induced apoptosis in HCT-116 cells

The bile acid, deoxycholate, can induce apoptosis although the effect of trace elements on such cell death is unknown. The aim of this study was to determine if deoxycholate-induced apoptosis is influenced by zinc. HCT-116 colon epithelial cells were pre-treated with zinc and then exposed to deoxycholate. Membrane blebbing, formation of apoptotic bodies, and greater overall production of reactive oxygen species (ROS) occurred in cells exposed to deoxycholate, but zinc inhibited the occurrence of these three events caused by deoxycholate. Upon finer analysis, stimulation of mitochondrial superoxide production, mitochondrial dysfunction, and cytochrome c release were detected in cells exposed to deoxycholate, but zinc did not inhibit any of these three effects caused by deoxycholate. Additionally, caspase-3 activation, plasma membrane phospholipid translocation, and also chromatin condensation and fragmentation were observed in cells exposed to deoxycholate, but all of these effects of deoxycholate, including the greater overall ROS production, were all inhibited by zinc. Because zinc did not prevent the three mitochondrial effects caused by deoxycholate, the last set of findings suggested that zinc hampered activation of an initiator caspase upstream of effector caspase-3, in inhibiting deoxycholate-induced HCT-116 cell death. In examining this possibility, it was found that caspase-8 activation caused by deoxycholate was blocked by zinc. Collectively, the results suggest that zinc can inhibit deoxycholate-induced apoptotic cell death mediated by caspases.

The supplementation of zinc increased the apoptosis of airway smooth muscle cells by increasing p38 phosphorylation

Proliferation of airway smooth muscle cells (ASMCs) is believed to play an important role in causing airway hyperresponsiveness (AHR). It has also been reported that platelet-derived growth factor (PDGF) can stimulate proliferation of ASMCs. We hypothesize that the concentration of zinc in the bodies of asthmatic patients may play a role in PDGF activity and therefore may be related to the variations in severity of airway inflammation and narrowing seen in asthmatic patients. We investigated the effects and mechanisms of zinc supplementation in PDGF-treated ASMCs. In this study, PDGF-treated primary ASMCs were cultured with 3, 12, 24, or 96 μM ZnSO₄. We found that the highest concentration of ZnSO₄ (96 μM) was cytotoxic for ASMCs. PDGF was used to induce ASMCs proliferation under different zinc concentrations. Neither 3 μM nor 12 μM ZnSO₄ inhibited proliferation of PDGF-treated ASMCs, although 24 μM ZnSO₄ caused treatment-induced apoptosis in PDGF-treated ASMCs. Supplementation with 24 μM ZnSO₄ may therefore increase p38 activation and reduce Akt phosphorylation. Zinc supplementation may reduce proliferation of PDGF-treated ASMCs through the activation of p38 mitogen-activated protein kinase (MAP kinase) and suppression of Akt phosphorylation, which both drive the induction of cellular apoptosis, subsequently reducing the proliferation of ASMCs.

Elemental fingerprinting of tumorous and adjacent non-tumorous tissues from patients with colorectal cancer using ICP-MS, ICP-OES and chemometric analysis

Tumorous and adjacent non-tumorous paired biopsies from 38 patients with colorectal cancer were analyzed by inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry after low-volume microwave digestion. 18 elements were investigated: Ag, Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, P, Pb, S, Se and Zn. Different chemometric tools were used for data evaluation: Wilcoxon signed rank test, Hieratical clustering analysis, principal component analysis (PCA) and linear discriminant analysis (LDA). With the exception of Al, tumours were observed to have significantly more elevated concentrations of essential elements as compared to non-tumours. On the contrary, elements considered potentially carcinogenic such as Cr, Ni, Mo or Co do not display significant differences. When PCA was applied, different components were obtained for tumorous and non-tumorous tissues. When LDA was applied for the elements studied (including essential and non-essential elements) about 90% of cases were correctly classified.

Prevention of mutation, cancer, and other age-associated diseases by optimizing micronutrient intake

I review three of our research efforts which suggest that optimizing micronutrient intake will in turn optimize metabolism, resulting in decreased DNA damage and less cancer as well as other degenerative diseases of aging. (1) Research on delay of the mitochondrial decay of aging, including release of mutagenic oxidants, by supplementing rats with lipoic acid and acetyl carnitine. (2) The triage theory, which posits that modest micronutrient deficiencies (common in much of the population) accelerate molecular aging, including DNA damage, mitochondrial decay, and supportive evidence for the theory, including an in-depth analysis of vitamin K that suggests the importance of achieving optimal micronutrient intake for longevity. (3) The finding that decreased enzyme binding constants (increased Km) for coenzymes (or substrates) can result from protein deformation and loss of function due to an age-related decline in membrane fluidity, or to polymorphisms or mutation. The loss of enzyme function can be compensated by a high dietary intake of any of the B vitamins, which increases the level of the vitamin-derived coenzyme. This dietary remediation illustrates the importance of understanding the effects of age and polymorphisms on optimal micronutrient requirements. Optimizing micronutrient intake could have a major effect on the prevention of cancer and other degenerative diseases of aging.

Enhanced Gadd45 expression and delayed G2/M progression are p53-dependent in zinc-supplemented human bronchial epithelial cells

Zinc is an essential nutrient for humans; however, this study demonstrated for the first time that an elevated zinc status, created by culturing cells at optimal plasma zinc concentration attainable by oral zinc supplementation, is cytotoxic for normal human bronchial epithelial (NHBE) cells. p53 plays a central role in the modulation of cell signal transduction in response to the stress from DNA damage, hypoxia and oncogene activation. The present study was designed to determine whether the previously reported increased Gadd45 expression and delayed G2/M cell cycle progression in zinc-supplemented NHBE cells is p53-dependent, and to decipher the mechanisms responsible for the regulation of Gadd45 expressions by p53, and elucidate the Gadd45 functions in impaired cell growth and cell cycle progression in NHBE cells. Cells were cultured for one passage in different concentrations of zinc: <0.4 micromol/L (ZD) as severe zinc-deficient; 4 micromol/L (ZN) as normal zinc level in culture medium; 16 micromol/L (ZA) as normal human plasma zinc level; and 32 micromol/L (ZS) as the high end of plasma zinc attainable by oral supplementation. Inhibition of cell growth and upregulation of p53 mRNA and protein expression were observed in ZS cells. Most importantly, ZS treatment also enhanced Gadd45 nuclear protein level and promoter activity, decreased CDK1-Cyclin B1 level and delayed G2/M cell cycle progression. These changes were normalized to those observed in ZN by treating ZS cells with Pifitherin, an inhibitor of p53 transactivation activity. Thus, our findings support the p53 dependency of the Gadd45-CDK1/Cyclin B1-G2/M cell cycle progression pathway in ZS NHBE cells.

Optimal micronutrients delay mitochondrial decay and age-associated diseases

Three of our research efforts are reviewed, which suggest that optimizing metabolism will delay aging and the diseases of aging in humans. (1) Research on delay of the mitochondrial decay of aging by supplementing rats with lipoic acid and acetyl carnitine. (2) The triage theory, which posits that modest micronutrient deficiencies (common in much of the population) accelerate molecular aging, including mitochondrial decay, and supportive evidence, including an analysis in depth of vitamin K, that suggests the importance of achieving optimal micronutrient intake for longevity. (3) The finding that decreased enzyme binding constants (increased Km) for coenzymes (or substrates) can result from protein deformation and loss of function due to loss of membrane fluidity with age, or to polymorphisms or mutation. The loss of enzyme function can be ameliorated by high doses of a B vitamin, which raises coenzyme levels, and indicates the importance of understanding the effects of age, or polymorphisms, on micronutrient requirements.

Topoisomerase IIalpha binding domains of adenomatous polyposis coli influence cell cycle progression and aneuploidy

BACKGROUND

Truncating mutations in the tumor suppressor gene APC (Adenomatous Polyposis Coli) are thought to initiate the majority of colorectal cancers. The 15- and 20-amino acid repeat regions of APC bind beta-catenin and have been widely studied for their role in the negative regulation of canonical Wnt signaling. However, functions of APC in other important cellular processes, such as cell cycle control or aneuploidy, are only beginning to be studied. Our previous investigation implicated the 15-amino acid repeat region of APC (M2-APC) in the regulation of the G2/M cell cycle transition through interaction with topoisomerase IIalpha (topo IIalpha).

METHODOLOGY/PRINCIPAL FINDINGS

We now demonstrate that the 20-amino acid repeat region of APC (M3-APC) also interacts with topo IIalpha in colonic epithelial cells. Expression of M3-APC in cells with full-length endogenous APC causes cell accumulation in G2. However, cells with a mutated topo IIalpha isoform and lacking topo IIbeta did not arrest, suggesting that the cellular consequence of M2- or M3-APC expression depends on functional topoisomerase II. Both purified recombinant M2- and M3-APC significantly enhanced the activity of topo IIalpha. Of note, although M3-APC can bind beta-catenin, the G2 arrest did not correlate with beta-catenin expression or activity, similar to what was seen with M2-APC. More importantly, expression of either M2- or M3-APC also led to increased aneuploidy in cells with full-length endogenous APC but not in cells with truncated endogenous APC that includes the M2-APC region.

CONCLUSIONS/SIGNIFICANCE

Together, our data establish that the 20-amino acid repeat region of APC interacts with topo IIalpha to enhance its activity in vitro, and leads to G2 cell cycle accumulation and aneuploidy when expressed in cells containing full-length APC. These findings provide an additional explanation for the aneuploidy associated with many colon cancers that possess truncated APC.

Zinc at clinically-relevant concentrations potentiates the cytotoxicity of polysorbate 80, a non-ionic surfactant

Polysorbate 80, a non-ionic surfactant, is used in the formula of water-insoluble anticancer agents for intravenous application. In our recent studies, this surfactant decreased cellular thiol content and the chemicals decreasing cellular thiol content increased intracellular Zn(2+) concentration. In this study using rat thymocytes, the effect of polysorbate 80 on FluoZin-3 fluorescence, an indicator for intracellular Zn(2+), and the influence of ZnCl(2) on cytotoxicity of polysorbate 80 were examined in order to test the possibility that Zn(2+) is involved in cytotoxic action of polysorbate 80. The surfactant at concentrations of 10 microg/ml or more significantly augmented FluoZin-3 fluorescent in a concentration-dependent manner, indicating an increase in intracellular Zn(2+) concentration. The increase by polysorbate 80 was also observed after removing extracellular Zn(2+), suggesting an intracellular Zn(2+) release. The simultaneous application of polysorbate 80 (30 microg/ml) and ZnCl(2) (10-30 microM) significantly increased cell lethality. The simultaneous application of ZnCl(2) accelerated the process of cell death induced by polysorbate 80 and the combination increased oxidative stress. Results may indicate that the cytotoxicity of polysorbate 80 at clinical concentrations is modified by micromolar zinc. Although there is no clinical report that polysorbate 80 and zinc salt are simultaneously applied to human as far as our knowledge, it may be speculated that zinc induces some diverse actions in cancer treatment with water-insoluble anticancer agent including nanoparticle drug of which the solvent is polysorbate 80.

9-bromonoscapine-induced mitotic arrest of cigarette smoke condensate-transformed breast epithelial cells

In the present investigation, we determined the chemotherapeutic efficacy of 9-bromonoscapine (Br-Nos), a more potent noscapine analog, on MCF10A, spontaneously immortalized human normal breast epithelial cells and MCF10A-CSC3, cigarette smoke condensate (CSC)-transformed cells. The results from cytogenetic analysis showed that Br-Nos induced polyploidy and telomeric association in MCF10A-CSC3 cells, while MCF10A cells remained unaffected. Our immunofluorescence data further demonstrated that MCF10A-CSC3 cells were susceptible to mitotic catastrophe on exposure to Br-Nos and failed to recover after drug withdrawal. MCF10A-CSC3 cells exhibited Br-Nos-induced aberrant multipolar spindle formation, which irreversibly impaired the alignment of replicated chromosome to the equatorial plane and finally culminated in cell death. Although MCF10A cells upon Br-Nos treatment showed bipolar spindles with some uncongressed chromosomes, these cells recovered fairly well after drug withdrawal. Our flow-cytometry analysis data reconfirmed that MCF10A-CSC3 cells were more susceptible to cell death compared to MCF10A cells. Furthermore, our results suggest that decreased levels of cdc2/cyclin B1 and cdc2 kinase activity are responsible for Br-Nos-induced mitotic cell arrest leading to cell death in MCF10A-CSC3 cells. This study thus explores the underlying mechanism of Br-Nos-induced mitotic catastrophe in CSC-transformed MCF10A-CSC3 cells and its potential usefulness as a chemotherapeutic agent for prevention of cigarette smoke-induced breast cancer growth.

Farnesoid X receptor deficiency in mice leads to increased intestinal epithelial cell proliferation and tumor development

Increased dietary fat consumption is associated with colon cancer development. The exact mechanism by which fat induces colon cancer is not clear, however, increased bile acid excretion in response to high-fat diet may promote colon carcinogenesis. The farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily, and bile acids are endogenous ligands of FXR. FXR is highly expressed in the intestine and liver where FXR is essential for maintaining bile acid homeostasis. The role of FXR in intestine cancer development is not known. The current study evaluated the effects of FXR deficiency in mice on intestinal cell proliferation and cancer development. The results showed that FXR deficiency resulted in increased colon cell proliferation, which was accompanied by an up-regulation in the expression of genes involved in cell cycle progression and inflammation, including cyclin D1 and interleukin-6. Most importantly, FXR deficiency led to an increase in the size of small intestine adenocarcinomas in adenomatous polyposis coli mutant mice. Furthermore, after treatment with a colon carcinogen, azoxymethane, FXR deficiency increased the adenocarcinoma multiplicity and size in colon and rectum of C57BL/6 mice. Loss of FXR function also increased the intestinal lymphoid nodule numbers in the intestine. Taken together, the current study is the first to show that FXR deficiency promotes cell proliferation, inflammation, and tumorigenesis in the intestine, suggesting that activation of FXR by nonbile acid ligands may protect against intestinal carcinogenesis.

Interaction between tumor suppressor adenomatous polyposis coli and topoisomerase IIalpha: implication for the G2/M transition

The tumor suppressor adenomatous polyposis coli (APC) is implicated in regulating multiple stages of the cell cycle. APC participation in G1/S is attributed to its recognized role in Wnt signaling. APC function in the G2/M transition is less well established. To identify novel protein partners of APC that regulate the G2/M transition, APC was immunoprecipitated from colon cell lysates and associated proteins were analyzed by matrix-assisted laser desorption ionization/time of flight (MALDI-TOF). Topoisomerase IIalpha (topo IIalpha) was identified as a potential binding partner of APC. Topo IIalpha is a critical regulator of G2/M transition. Evidence supporting an interaction between endogenous APC and topo IIalpha was obtained by coimmunoprecipitation, colocalization, and Förster resonance energy transfer (FRET). The 15-amino acid repeat region of APC (M2-APC) interacted with topo IIalpha when expressed as a green fluorescent protein (GFP)-fusion protein in vivo. Although lacking defined nuclear localization signals (NLS) M2-APC predominantly localized to the nucleus. Furthermore, cells expressing M2-APC displayed condensed or fragmented nuclei, and they were arrested in the G2 phase of the cell cycle. Although M2-APC contains a beta-catenin binding domain, biochemical studies failed to implicate beta-catenin in the observed phenotype. Finally, purified recombinant M2-APC enhanced topo IIalpha activity in vitro. Together, these data support a novel role for APC in the G2/M transition, potentially through association with topo IIalpha.

Suppression of Gadd45 alleviates the G2/M blockage and the enhanced phosphorylation of p53 and p38 in zinc supplemented normal human bronchial epithelial cells

An adequate zinc status is essential for optimal cellular functions and growth. Yet, excessive zinc supplementation can be cytotoxic and can impair cell growth. Gadd45 plays a vital role as cellular stress sensor in the modulation of cell signal transduction in response to stress. The present study was designed to determine the influence of zinc status on Gadd45 expression and cell cycle progression in zinc deficient and supplemented normal human bronchial epithelial (NHBE) cells, and to decipher the molecular mechanism(s) exerted by the suppression of Gadd45 expression on cell growth and cell cycle progression in this cell type. Cells were cultured for one passage in different concentration of zinc: <0.4 muM (ZD) as severe zinc deficient; 4 muM as normal zinc level in culture medium; 16 microM (ZA) as normal human plasma zinc level; and 32 muM (ZS) as the high end of plasma zinc attainable by oral supplementation. Inhibition of cell growth, upregulation of Gadd45 mRNA and protein expression, and blockage of G2/M cell cycle progression were observed in ZS cells. In contrast, little or no changes in these parameters were seen in ZD cells. The siRNA-mediated knocking down of Gadd45 was found to relieve G2/M blockage in ZS cells, which indicated that the blockage was Gadd45 dependent. Moreover, the enhanced phosphorylation of p38 and p53 (ser15) in ZS cells was normalized after suppression of Gadd45 by siRNA, implicating that the enhanced phosphorylation of these proteins was Gadd45 dependent. Thus, we demonstrated for the first time that an elevated zinc status modulated signal transduction to produce a delay at G2/M during cell cycle progression in NHBE cells.

Zinc-induced G2/M blockage is p53 and p21 dependent in normal human bronchial epithelial cells

The involvement of p53 and p21 signal pathway in the G2/M cell cycle progression of zinc-supplemented normal human bronchial epithelial (NHBE) cells was examined using the small interferring RNA (siRNA) approach. Cells were cultured for one passage in a different concentration of zinc: <0.4 microM (ZD) as zinc deficient; 4 microM as normal zinc level (ZN) in culture medium; 16 microM (ZA) as normal human plasma zinc level; and 32 microM (ZS) as the high end of plasma zinc attainable by oral supplementation. Nuclear p21 protein and mRNA levels as well as promoter activity in ZS cells, but not in ZD cells, were markedly elevated to almost twofold compared with ZN control cells. G2/M blockage in ZS cells was coupled with the observation of elevated p21 gene expression. In ZS cells, the abrogation of p21 protein induction by the transfection of p21 siRNA was shown to alleviate the G2/M blockage, demonstrating the positive linkage of p21 elevation and G2/M blockage. Abolishment of the increase in p53 protein in ZS cells with transfection of p53 siRNA normalized the elevated p21 protein to a similar level as in ZN control cells, which demonstrated that the p21 induction is p53 dependent. Furthermore, the normalization of p53 protein by siRNA treatment in ZS cells alleviated cell growth depression and G2/M blockage, which demonstrated that p53 was involved in the high zinc status-induced G2/M blockage and growth depression. Thus high zinc status in NHBE cells upregulates p53 expression which in turn elevates p21 that eventually induces G2/M blockage.

Zinc as an anti-tumor agent in prostate cancer and in other cancers

Human prostate glandular epithelial cells have the unique capability of accumulating high levels of zinc. This is essential to inhibit m-aconitase activity so that citrate can accumulate for secretion into prostatic fluid, which is a major function of the prostate gland. As a result, the Krebs cycle is truncated with the consequence of the lost ATP production that would result from citrate oxidation. The cellular accumulation of zinc also inhibits mitochondrial terminal oxidation and respiration. In addition to these metabolic effects, zinc accumulation exhibits anti-proliferative effects via its induction of mitochondrial apoptogenesis. Zinc accumulation also inhibits the invasive/migration activities in malignant prostate cells. The anti-proliferative effects and the effects on invasion and migration occur through zinc activation of specific intracellular signaling pathways. Consequently, these effects impose anti-tumor actions by zinc. The ability of prostate cells to accumulate zinc is due to the expression and activity of the zinc uptake transporter, ZIP1. To avoid the anti-tumor effects of zinc, in prostate cancer the malignant prostate cells exhibit a silencing of ZIP1 gene expression accompanied by a depletion of cellular zinc. Therefore we regard ZIP1 as a tumor suppressor gene in prostate cancer. In addition to prostate cells, similar tumor suppressor effects of zinc have been identified in several other types of tumors.

Zinc induced apoptosis in HEP-2 cancer cells: the role of oxidative stress and mitochondria

Induction of apoptosis by zinc sulfate was investigated during 96 h exposure on the cancer Hep-2 cell line. During 48 h of exposure, zinc translocated into mitochondria and stimulated production of reactive oxygen species (ROS), affected cellular GSH management and induced moderate activation of p53 and dissipation of mitochondrial membrane potential. In Zn-exposed cells, mitochondria released cytochrome c and AIF, whose translocation to the cytoplasm or the nucleus coincided with the activation of apoptosis. The use of various pharmacological inhibitors inhibiting particular apoptotic targets (antioxidants such as N-acetyl-cysteine and coenzyme Q, the caspase inhibitors z-DEVD-fmk and z-VAD-fmk, cyclosporin A and bonkgrekic acid) proved that Zn acts both directly and indirectly on mitochondria and observed apoptosis is executed by caspase-dependent and caspase-independent pathways.

Reduced levels of the adenomatous polyposis coli (APC) protein are associated with ceramide-induced apoptosis of colon cancer cells

PURPOSE

Mutations of the adenomatous polyposis coli (APC) and p53 genes are commonly found in colorectal cancers. We therefore analyzed the relative roles of APC and p53 in the induction of apoptosis of colon cancer cells by comparing the effects of the natural chemopreventive agent, C(2)-ceramide, on different human colon cancer cell lines with and without wild-type p53 and APC genes.

METHODS

We studied the effect of C(2)-ceramide and C(2)-dihydroceramide on proliferation and/or apoptosis of colon cancer cell lines in vitro and determined the role of p53 and APC proteins in these processes. The protein and mRNA levels in colon cancer cell lines with and without treatments were determined by Western and Northern blot analysis, respectively. The cell cycle and apoptosis profiles were determined by FACS analysis and PARP-1 cleavage.

RESULTS

Our findings indicate that C(2)-ceramide can induce apoptosis independently of the p53/p21(Waf-1/Cip-1) pathway. In addition, the C(2)-ceramide induction of apoptosis showed a correlation with a reduction in the levels of the APC protein and mRNA. Moreover, the C(2)-ceramide-induced apoptosis was blocked by pre-treatment with ZnCl(2), which stabilizes APC protein levels.

CONCLUSIONS

These results suggest that C(2)-ceramide treatment reduces the levels of APC protein and that the reduction in the levels of this protein plays a key role in the ability of C(2)-ceramide to induce apoptosis of colon cancer cells.