Procarcinogenic Effects Research Articles

Retracted: Response to dual blockade of epidermal growth factor receptor (EGFR) and cycloxygenase‐2 in nonsmall cell lung cancer may be dependent on the EGFR mutational status of the tumor

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have demonstrated clinical benefit in patients with nonsmall cell lung cancer (NSCLC), particularly those with tumors that have EGFR-TK domain mutations. Moreover, the EGFR and cyclooxygenase (COX)-2 pathways are known to enhance the procarcinogenic effects of each other in different tumor types. Therefore, it was hypothesized that tumor EGFR mutation status may influence the effectiveness of simultaneous EGFR and COX-2 inhibition in patients with NSCLC. Three NSCLC cell lines with varying EGFR mutation status and sensitivities to EGFR-TKIs were selected: H3255 (L858R), H1650 (del E746-A750), and H1781 (wild-type EGFR). Cells were treated with erlotinib, gefitinib, or celecoxib alone, and the combination of both EGFR-TKI inhibitors with celecoxib. Cell survival and apoptosis was assessed and correlated with the expression of COX-2, EGFR, pEGFR, Akt, pAkt, expression, and derived prostaglandin E2 (PGE(2)). Celecoxib by itself was found to have no effects on cell growth or apoptosis in any of the cell lines. Erlotinib and gefitinib inhibited cell growth and induced apoptosis in both mutant cell lines and did so in H1781 cells at 10-fold higher concentrations. Celecoxib when added to erlotinib or gefitinib significantly enhanced the antiproliferative and proapoptotic effects in both mutant cell lines but had no additional effects in H1781 cells. Greater down-regulation of COX-2, EGFR, pEGFR, Akt, pAkt, and PGE(2) was found when H3255 cells were treated with the combination compared with any of the single agents alone. The results of the current study demonstrate that the effectiveness of the addition of celecoxib to an EGFR-TKI is significantly greater in NSCLC cells with EGFR mutations, which is likely due to more complete inhibition of both pathways.

Helicobacter and Gastric Malignancies

Over the past year Helicobacter pylori has been confirmed as the most important risk factor for non-cardia gastric adenocarcinomas and gastric mucosa-associated lymphoid tissue (MALT) lymphomas. Eradication therapy has been proven to be beneficial when given prior to the development of intestinal metaplasia, but is less efficacious when administered later. However, the best data from clinical trials indicate that H. pylori eradication alone will have only a moderate effect on gastric cancer incidence worldwide. The mechanisms responsible for H. pylori-associated gastric carcinogenesis continue to be dissected. Accumulating evidence suggests that some H. pylori may be able to invade through the gastric epithelial barrier, though pro-carcinogenic effects may also be related to the complex and evolving pathways of altering signal transduction pathways within gastric epithelial cells that are stimulated by adherence and translocation of H. pylori products through its type IV secretory system. Determinants of the host response to H. pylori infection continue to focus on polymorphisms in genes related to the innate and acquired immune responses, including NOD2, COX-2, and TLR-4. H. pylori eradication is indicated for low-grade gastric B-cell MALT lymphoma and may even provide "cure" in some apparently H. pylori-negative cases. How and why does H. pylori promote lymphomagenesis? Some evidence from human and murine models points to specific chromosomal translocations and host genetic polymorphisms as relating to the outcome of infection. Finally, Helicobacter hepaticus infection has been linked to both intestinal and breast tumorigenesis in susceptible strains of female mice - a provocative and novel finding warranting further investigation.

Curcumin Inhibits Neurotensin-Mediated Interleukin-8 Production and Migration of HCT116 Human Colon Cancer Cells

Neurotensin, a gut tridecapeptide, acts as a potent cellular mitogen for various colorectal and pancreatic cancers that possess high-affinity neurotensin receptors. Cytokine/chemokine proteins are increasingly recognized as important local factors that play a role in the metastasis and invasion of multiple cancers. The purpose of this study was to (a) determine the effect of neurotensin on cytokine/chemokine gene expression and cell migration in human cancer cells and (b) assess the effect of curcumin, a natural dietary product, on neurotensin-mediated processes. The human colorectal cancer, HCT116, was treated with neurotensin, with or without curcumin, and interleukin (IL)-8 expression and protein secretion was measured. Signaling pathways, which contribute to the effects of neurotensin, were assessed. Finally, the effect of curcumin on neurotensin-mediated HCT116 cell migration was analyzed. We show that neurotensin, acting through the native high-affinity neurotensin receptor, induced IL-8 expression in human colorectal cancer cells in a time- and dose-dependent fashion. This stimulation involves Ca2+-dependent protein kinase C, extracellular signal-regulated kinase-dependent activator protein-1, and extracellular signal-regulated kinase-independent nuclear factor-kappaB pathways. Curcumin inhibited neurotensin-mediated activator protein-1 and nuclear factor-kappaB activation and Ca2+ mobilization. Moreover, curcumin blocked neurotensin-stimulated IL-8 gene induction and protein secretion and, at a low concentration (i.e., 10 micromol/L), blocked neurotensin-stimulated colon cancer cell migration. Neurotensin-mediated induction of tumor cell IL-8 expression and secretion may contribute to the procarcinogenic effects of neurotensin on gastrointestinal cancers. Furthermore, a potential mechanism for the chemopreventive and chemotherapeutic effects of curcumin on colon cancers may be through the inhibition of gastrointestinal hormone (e.g., neurotensin)-induced chemokine expression and cell migration.

Androgen regulation of soluble guanylyl cyclaseα1 mediates prostate cancer cell proliferation

The growth and progression of prostate cancer are dependent on androgens and androgen receptor (AR), which act by modulating gene expression. Utilizing a gene microarray approach, we have identified the alpha1-subunit gene of soluble guanylyl cyclase (sGC) as a novel androgen-regulated gene. A heterodimeric cytoplasmic protein composed of one alpha and one beta subunit, sGC mediates the widespread cellular effects of nitric oxide (NO). We report here that, in prostate cancer cells, androgens stimulate the expression of sGCalpha1. A cloned human sGCalpha1 promoter is activated by androgen in an AR-dependent manner, suggesting that sGCalpha1 may be a direct AR target gene. Disruption of sGCalpha1 expression severely compromises the growth of both androgen-dependent and androgen-independent AR-positive prostate cancer cells. Overexpression of sGCalpha1 alone is sufficient for stimulating prostate cancer cell proliferation. Interestingly, the major growth effect of sGCalpha1 is independent of NO and cyclic guanosine monophosphate, a major mediator of the sGC enzyme. These data strongly suggest that sGCalpha1 acts in prostate cancer via a novel pathway that does not depend on sGCbeta1. Tissue studies show that sGCalpha1 expression is significantly elevated in advanced prostate cancer. Thus, sGCalpha1 may be an important mediator of the procarcinogenic effects of androgens.

Genetic and Epigenetic Interactions between Folate and Aging in Carcinogenesis

Folate is among the most strongly implicated dietary components to convey protection against colon cancer, and diminished folate status is associated with an enhanced risk of colon cancer. Age is also regarded as one of the most important risk factors for colonic carcinogenesis. It is therefore of considerable interest to determine whether the process of aging influences folate metabolism in the colon and whether folate supplementation might prevent the procarcinogenic effects associated with aging. Recent studies in our laboratory demonstrated that the colonic mucosa of elder rats is more susceptible to folate depletion than that of young rats. Depletion of folate results in a shift in the forms of folate in the colon as well as increased uracil incorporation into DNA, a purported mechanism for colonic carcinogenesis. However, modest folate supplementation eliminates evidence of inadequate folate status in the colons of elder rats, suggesting that the relation between age and folate status in the colon might be one mechanism by which aging modulates colorectal cancer risk. Interactions between folate and aging also affect a spectrum of epigenetic and genetic phenomena such as uracil misincorporation, DNA methylation, protein methylation, mitochondrial deletion, and critical gene expression, which could be related to carcinogenesis. Aging and inadequate dietary folate may interact and collectively induce derangements in folate metabolism, thereby provoking subsequent molecular aberrations, which may enhance carcinogenesis. However, folate supplementation appears to reverse these adverse effects of aging, which is potentially of substantial import because the latter is an unmodifiable risk factor.

Tobacco Smoke Stimulates the Transcription of Amphiregulin in Human Oral Epithelial Cells: Evidence of a Cyclic AMP-Responsive Element Binding Protein–Dependent Mechanism

Activation of epidermal growth factor receptor (EGFR)-mediated signaling has been implicated in the pathogenesis of tobacco smoke-induced cancers. Recently, elevated levels of amphiregulin, a ligand of the EGFR, were found in the oral mucosa of smokers. The main objective of this study was to elucidate the mechanism by which tobacco smoke induces amphiregulin. Treatment of a nontumorigenic human oral epithelial cell line (MSK-Leuk1) with a saline extract of tobacco smoke stimulated amphiregulin (AR) transcription resulting in increased amounts of amphiregulin mRNA and protein. Tobacco smoke stimulated the cyclic AMP (cAMP)-->protein kinase A (PKA) pathway leading to increased cAMP-responsive element binding protein-dependent activation of AR transcription. These inductive effects of tobacco smoke were dependent on the aryl hydrocarbon receptor (AhR). In fact, alpha-naphthoflavone, an AhR antagonist, blocked tobacco smoke-mediated induction of binding of cAMP-responsive element binding protein to the AR promoter and thereby suppressed the induction of amphiregulin. Notably, treatment of MSK-Leuk1 cells with tobacco smoke or exogenous amphiregulin stimulated DNA synthesis. An inhibitor of EGFR tyrosine kinase or a neutralizing antibody to amphiregulin abrogated the increase in DNA synthesis mediated by tobacco smoke. Taken together, these findings suggest that tobacco smoke stimulated a signaling pathway comprised of AhR-->cAMP-->PKA resulting in enhanced AR transcription and increased DNA synthesis. The ability of tobacco smoke to induce amphiregulin and thereby enhance DNA synthesis is likely to contribute to the procarcinogenic effects of tobacco smoke.

Sanguinarine activates polycyclic aromatic hydrocarbon associated metabolic pathways in human oral keratinocytes and tissues

Sanguinarine's use in human clinical applications is currently controversial. While some studies have demonstrated sanguinarine's anti-inflammatory and anti-oxidant properties, other investigations reported sanguinarine's procarcinogenic effects. Like the tobacco-associated carcinogen, benzo( a)pyrene (B( a)P), sanguinarine is a polycyclic aromatic hydrocarbon (PAH). PAH exposure activates the aryl hydrocarbon transcription activating factor (AhR), resulting in nuclear translocation, binding to the aryl hydrocarbon nuclear translocator (ARNT), which thereby increases expression of a pool of carcinogen metabolizing enzymes. The goal of this study was to investigate whether sanguinarine activates this PAH-associated signaling cascade in human oral cells and tissues. Our results demonstrate that sanguinarine: (i) results in formation of the AhR–ARNT complex, (ii) induces AhR-associated gene expression, (iii) inhibits cytochrome P450 1A1 (CYP 1A1) microsomal oxidative activity and (iv) pretreatment upregulates CYP 1A1 function. Collectively, these data provide evidence that sanguinarine activates PAH-associated signaling and metabolic pathways. Notably, previous studies have demonstrated that mammalian hepatic microsomes metabolize sanguinarine to a mutagenic epoxide. Persons who respond to sanguinarine exposure with induction of primarily Phase I relative to Phase II enzymes are, therefore, at risk for sanguinarine bioactivation and its potential mutagenic effects.

Antioxidant Vitamin Supplementation Reduces Benzo(a)pyrene-DNA Adducts and Potential Cancer Risk in Female Smokers

Abstract Background: Elevated benzo(a)pyrene [B(a)P]-DNA adducts have been associated with 3-fold increased risk of lung cancer in current smokers. We assessed the chemopreventive effects of antioxidant supplementation using B(a)P-DNA adducts in leukocytes as an intermediate cancer risk marker. Methods: Subjects were randomized to a double-blinded placebo-controlled clinical trial of antioxidant vitamin supplementation [500 mg vitamin C and 400 IU vitamin E (dl-α-tocopherol) daily] or placebo. Smokers with ≥10 cigarettes per day and serum cotinine ≥25 ng/mL were eligible for the study. B(a)P-DNA adduct level was the outcome. The randomization was stratified by gender and cigarettes per day (≤20 or >20). Smoking habits and blood samples were collected every 3 months during the 15-month treatment period. Samples were analyzed for B(a)P-DNA adducts (high-performance liquid chromatography), plasma cotinine, vitamin levels, and GSTM1 genotype. The intent-to-treat model adjusted for B(a)P-DNA and cotinine at randomization. Results: Overall and among men, there was no effect of treatment on B(a)P-DNA adduct levels. Among treated women, B(a)P-DNA adducts decreased by 31% compared with women on placebo (P = 0.03). Among treated women with the GSTM1 genotype, there was a 43% decrease in adducts (P = 0.04). Conclusion: Our primary hypothesis that the mean level of smoking-related B(a)P-DNA adducts would be lower in all subjects in the vitamin treatment group compared with all placebo-treated subjects was not substantiated. However, oursecondary gender-specific analysis found a significant reduction in B(a)P-DNA adducts in women with vitamin treatment, suggesting that antioxidant supplementation maymitigate some of the procarcinogenic effects of exposuretoB(a)P. The effect in GSTM1-null women suggeststhat certain subgroups may derive more benefit fromsupplementation. Although the results of this trial showthe potential chemopreventive role of antioxidants, thebest way for smokers to reduce their cancer risk remains smoking cessation.

Histologic Features in Primary Cutaneous Squamous Cell Carcinomas in Immunocompromised Patients Focusing on Organ Transplant Patients

BACKGROUND In organ transplant recipients (OTR) there is an increased incidence of cutaneous squamous cell carcinomas (CSCC), and they may be aggressive. OBJECTIVE We wanted to determine whether any histologic features were characteristic or more common in CSCC of OTR. METHODS A total of 518 immunocompetent individuals with 601 primary CSCC were examined. Seventy-nine OTR with 231 primary CSCC, 53 renal OTR, 25 heart/heart lung OTR, and 1 liver OTR were examined. RESULTS In all patient populations, CSCC occurred dominantly in chronically sun-exposed skin. In OTR, however, a greater percentage occurred on the extremity, particularly the upper extremity, and they occurred at an earlier age. Features that were significantly more common in OTR were acantholytic changes, early dermal invasion, an infiltrative growth pattern with or without desmoplasia, and Bowen's disease with carcinoma. In OTR primary CSCC were also significantly deeper at time of diagnosis. CONCLUSIONS Our findings confirmed the association of ultraviolet radiation exposure with development of CSCC in OTR. The increased depth of the primary CSCC in OTR is surprising because these patients are followed closely for skin cancer compared with immunocompetent patients. The other morphologic features that were significantly more common in OTR may theoretically reflect not only the type of iatrogenic immunosuppression in these patients, but also other procarcinogenic effects of their medications.

Histologic features in primary cutaneous squamous cell carcinomas in immunocompromised patients focusing on organ transplant patients.

In organ transplant recipients (OTR) there is an increased incidence of cutaneous squamous cell carcinomas (CSCC), and they may be aggressive. We wanted to determine whether any histologic features were characteristic or more common in CSCC of OTR. A total of 518 immunocompetent individuals with 601 primary CSCC were examined. Seventy-nine OTR with 231 primary CSCC, 53 renal OTR, 25 heart/heart lung OTR, and 1 liver OTR were examined. In all patient populations, CSCC occurred dominantly in chronically sun-exposed skin. In OTR, however, a greater percentage occurred on the extremity, particularly the upper extremity, and they occurred at an earlier age. Features that were significantly more common in OTR were acantholytic changes, early dermal invasion, an infiltrative growth pattern with or without desmoplasia, and Bowen's disease with carcinoma. In OTR primary CSCC were also significantly deeper at time of diagnosis. Our findings confirmed the association of ultraviolet radiation exposure with development of CSCC in OTR. The increased depth of the primary CSCC in OTR is surprising because these patients are followed closely for skin cancer compared with immunocompetent patients. The other morphologic features that were significantly more common in OTR may theoretically reflect not only the type of iatrogenic immunosuppression in these patients, but also other procarcinogenic effects of their medications.

Exposure of calf thymus DNA to autoxidized β-carotene results in the formation of 8-oxo-deoxyguanosine

Oxidized β-carotene (OBC) has been shown to have pro-oxidant and pro-carcinogenic effects. We recently reported that OBC induces oxidative DNA damage, measured as 8-hydroxy-deoxyguanosine (8-oxo-dG), in both calf thymus DNA and cellular DNA. However, the mechanism by which OBC induces the formation of 8-oxo-dG is unclear. To examine the hypothesis that reactive oxygen species (ROS), produced by BC autoxidation, cause the formation of 8-oxo-dG, radical scavengers were added to calf thymus DNA incubated with OBC. The results showed that butylated hydroxytoluene (BHT), a peroxyl radical scavenger, and diphenylamine, an alkoxyl radical scavenger, strongly decreased 8-oxo-dG levels. Singlet oxygen (1O2) was also a major ROS involved while small but detectable amounts of •OH were produced. Autoxidation of BC itself at 60 or 37 °C produced aldehydes (measured as cyclohexanedione-reactive substances) and thiobarbituric acid-reactive substances (TBARS), suggesting the presence of chain-propagated reactions during autoxidation. Thus, the present study demonstrates that ROS, produced by BC autoxidation, induce the formation of 8-oxo-dG in calf thymus DNA.

Cancer and the Cyclo-oxygenase Enzyme

The cyclo-oxygenase (COX) metabolic pathway and prostaglandin (PG) production appear to play a causal role in the promotion and progression of human cancers. COX-1 and COX-2 are the enzymes that convert arachidonic acid into PGs and thromboxanes. COX-2 has received a great deal of attention recently because it is commonly overexpressed in a wide range of cancers and precancerous lesions (e.g. in colon, lung, prostate and breast), and elevated production of prostanoids (particularly prostaglandin [PGE2]) via COX-2 is associated with several pro-carcinogenic effects including: increased proliferation, apoptosis resistance, host immunosuppression, tumor neoangiogenesis, and increased metastatic potential. Inhibitors of COX-1 and COX-2 (e.g. aspirin and most other nonsteroidal anti-inflammatory drugs) and of COX-2 alone (e.g. celecoxib and rofecoxib) have shown cancer preventative efficacy in epidemiological studies, experimental studies in laboratory animals, and in human clinical trials. Because of their improved tolerability profile, COX-2 selective inhibitors appear to hold substantial promise for long-term administration in the setting of cancer prevention. Emerging data suggest that these agents may have potential in cancer treatment as well. This article attempts to comprehensively review the role of the COX pathway in tumorigenesis, and the mechanisms, safety, and efficacy of COX nonselective and COX-2 selective inhibitors for cancer chemopreventive and chemotherapeutic applications.

Exposure to an environment containing the aromatic red cedar, Juniperus virginiana: procarcinogenic, enzyme-inducing and insecticidal effects

1. (1) Shavings from the Eastern Red Cedar ( Junuperus virginiana) were examined for three diverse biological properties, i.e. enzyme induction, procarcinogenicity and insecticidal activity. 2. (2) The ability of a cedar environment to stimulate liver drug-metabolizing enzymes in mice was confirmed by lowered values for barbiturate sleeping time. 3. (3) In susceptible strains of mice (C3H-A vy, C3H-A vyfB and CBA/J) the use of cedar shavings as bedding increased significantly the incidence of spontaneous tumors of the liver and mammary gland, and also reduced the average time at which tumors appeared. 4. (4) Cedar and some of its derivatives (Oil of Cedarwood, cedrene, cedrol) disrupted the reproductive and developmental cycle of a number of insects, including the Peanut Trash Bug ( Elasmolomus sordidus), the Indian Meal Moth ( Plodia interpunctella) and the Forage Mite ( Tyrophagus putrescentiae).