Phytocompounds from essential oil of Mentha aquatica L. cv. Lime prevent vemurafenib-promoted skin carcinogenesis via inhibiting HRASQ61L keratinocytes and reprogramming macrophage activities

BACKGROUND

Twenty to thirty percent of patients taking BRAF inhibitors such as vemurafenib (PLX4032) for melanoma develop cutaneous squamous cell carcinomas.

PURPOSE

This study aimed to elucidate the chemopreventive effect of essential oil from Mentha aquatica L. cv. Lime (EO) and its major constituents, limonene and carvone (L + C) that made up 45.68% of the EO, against PLX4032-induced cutaneous side effects.

METHODS

PLX4032 accelerated skin papilloma formation and keratinocyte HRAS mutation in 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced two-stage skin carcinogenesis mouse model was used to evaluate the in vivo bioefficacy of EO and L + C. The effects and molecular mechanisms of EO and L + C on deregulating mouse PDVHRASQ61L keratinocyte activities were demonstrated using a spectrum of bioactivity assays, western blotting, immunochemistry, and keratinocyte-macrophage co-culture assay.

RESULTS

Treatment with EO suppressed colony formation ability, cell migration, invasion, and induced G2/M cell-cycle arrest and apoptosis in PDVHRASQ61L keratinocytes, and L + C treatment inhibited colony formation, cell migration and invasion of PDV cells. In mouse skin irritated with DMBA/TPA (DT group) or DMBA/TPA with PLX4032 (DTP group), topical application of EO and L + C significantly delayed papilloma appearance and reduced papilloma incidence compared to DT or DTP controls. Histopathology results showed that EO and L + C treatment attenuated K14+ keratinocyte proliferation and paradoxical MAPK activation, and shifted the macrophage population from M2 (CD163+) to M1 (iNOS+) in the mouse skin microenvironment. The conditioned medium of EO or L + C pre-treated PDV keratinocytes promoted M0 macrophages to differentiate from THP-1 cells into M1-like macrophages.

CONCLUSION

This study demonstrates that EO and L + C in combination prevent PLX4032-induced cutaneous side-effects and skin carcinogenesis in mice through reprogramming the macrophage cell population and inhibiting keratinocyte activity. Both mint EO and the natural products L + C can be considered to be effective chemopreventive agents that might be useful in reducing cutaneous lesions in human patients administrated with BRAF inhibitors.

DOT1L modulates the senescence-associated secretory phenotype through epigenetic regulation of IL1A

Oncogene-induced senescence (OIS) is a stable cell cycle arrest that occurs in normal cells upon oncogene activation. Cells undergoing OIS express a wide variety of secreted factors that affect the senescent microenvironment termed the senescence-associated secretory phenotype (SASP), which is beneficial or detrimental in a context-dependent manner. OIS cells are also characterized by marked epigenetic changes. We globally assessed histone modifications of OIS cells and discovered an increase in the active histone marks H3K79me2/3. The H3K79 methyltransferase disruptor of telomeric silencing 1-like (DOT1L) was necessary and sufficient for increased H3K79me2/3 occupancy at the IL1A gene locus, but not other SASP genes, and was downstream of STING. Modulating DOT1L expression did not affect the cell cycle arrest. Together, our studies establish DOT1L as an epigenetic regulator of the SASP, whose expression is uncoupled from the senescence-associated cell cycle arrest, providing a potential strategy to inhibit the negative side effects of senescence while maintaining the beneficial inhibition of proliferation.

Deficiency of Cathelicidin-related Antimicrobial Peptide Promotes Skin Papillomatosis in Mus musculus Papillomavirus 1-infected Mice

Cathelicidins have been reported to inhibit human papillomavirus infection in vitro; however, nothing is known about their activity in vivo. In this study, experimental skin infection with Mus musculus papillomavirus 1 resulted in robust development of cutaneous papillomas in cyclosporine A-treated C57BL/6J mice deficient for the murine cathelicidin-related antimicrobial peptide (CRAMP), in contrast to wild-type controls. Analysis of the underlying mechanisms revealed moderate disruption of virion integrity and lack of interference with viral entry and intracellular trafficking by a synthetic CRAMP peptide. Differences in the immune response to Mus musculus papillomavirus 1 infection were observed between CRAMP-deficient and wild-type mice. These included a stronger reduction in CD4+ and CD8+ T-cell numbers in infected skin, and lack of Mus musculus papillomavirus 1-specific neutralizing antibodies in response to cyclosporine A in the absence of endogenous CRAMP. CRAMP has modest direct anti-papillomaviral effects in vitro, but exerts protective functions against Mus musculus papillomavirus 1 skin infection and disease development in vivo, primarily by modulation of cellular and humoral immunity.

A Polymorphic Variant in p19Arf Confers Resistance to Chemically Induced Skin Tumors by Activating the p53 Pathway

Identification of the specific genetic variants responsible for the increased susceptibility to familial or sporadic cancers is important. Using a forward genetics approach to map such loci in a mouse skin cancer model, we previously identified a strong genetic locus, Stmm3, conferring resistance to chemically induced skin papillomas on chromosome 4. Here, we report the cyclin-dependent kinase inhibitor gene Cdkn2a/p19^Arf as a major responsible gene for the Stmm3 locus. We provide evidence that the function of Stmm3 is dependent on p53 and that p19^ArfMSM confers stronger resistance to papillomas than p16^Ink4aMSMin vivo. In addition, we found that genetic polymorphism in p19^Arf between a resistant strain, MSM/Ms (Val), and a susceptible strain, FVB/N (Leu), alters the susceptibility to papilloma development, malignant conversion, and the epithelial-mesenchymal transition. Moreover, we demonstrated that the p19^ArfMSM allele more efficiently activates the p53 pathway than the p19^ArfFVB allele in vitro and in vivo. Furthermore, we found polymorphisms in CDKN2A in the vicinity of a polymorphism in mouse Cdkn2a associated with the risk of human cancers in the Japanese population. Genetic polymorphisms in Cdkn2a and CDKN2A may affect the cancer risk in both mice and humans.

Concentrations of polycyclic aromatic hydrocarbons in liver samples of juvenile green sea turtles from Brazil: Can these compounds play a role in the development of fibropapillomatosis?

Fibropapillomatosis (FP) poses a significant threat to the conservation of green sea turtles (Chelonia mydas). Polycyclic aromatic hydrocarbons-PAHs are considered mutagenic, carcinogenic and toxic, and can act as cofactor of this disease. In order to evaluate possible differences between green sea turtles with and without FP, we monitored 15 PAHs in liver samples of 44 specimens (24 with FP) captured in Brazil. We detected eight PAHs and quantified phenanthrene in all green sea turtles with FP. Specimens without FP presented lower values than the tumored ones (1.48 ng g^-1 and 17.35 ng g^-1, respectively; p < 0.0001). There were no significant differences between tumored and non-tumored specimens, among studied areas, or Southwest Atlantic Fibropapillomatosis Score. Even though we found higher concentrations in the liver samples of green sea turtles with FP, further studies are necessary to confirm if these pollutants are involved in the pathogenesis of the disease.

Poly-MVA attenuates 7,12- dimethylbenz[a]anthracene initiated and croton oil promoted skin papilloma formation on mice skin

Chemopreventive agents which exhibit activities such as anti-inflammation, inhibition of carcinogen induced mutagenesis and scavenging of free radical might play a decisive role in the inhibition of chemical carcinogenesis either at the initiation or promotion stage. Many synthesized palladium (Pd) complexes tested experimentally for antitumor activity are found effective. Poly-MVA is a liquid blend preparation containing B complex vitamins, ruthenium with Pd complexed with alpha lipoic acid as the major ingredients. The antitumor effect of Poly-MVA was evaluated against 7,12-dimethylbenz[a] anthracene-initiated croton oil-promoted papilloma formation on mice skin. Skin tumor was initiated with a single application of 390 nmol of DMBA in 20 µl acetone. The effect of Poly-MVA against croton oil- induced inflammation and lipid peroxidation on the mice skin was also evaluated. Topical application of Poly-MVA (100 µl, twice weekly for 18 weeks) 30 minutes prior to each croton oil application, significantly decreased the tumor incidence (11%) and the average number of tumor per animals. Application of Poly-MVA (100 µl) before croton oil significantly (p &amp;#60; 0.05) protected the mouse skin from inflammation (36%) and lipid peroxidation (14%) when compared to the croton oil alone treated group. Experimental results indicate that Poly-MVA attenuate the tumor promoting effects of croton oil and the effect may probably be due to its anti-inflammatory and antioxidant activity.

Attenuation of DMBA/croton oil induced mouse skin papilloma by Apodytes dimidiata mediated by its antioxidant and antimutagenic potential

Context Considering the role of cellular oxidative stress in mutations and subsequent transformation, phytochemicals with antioxidant potential has become a primary choice as chemopreventives. Apodytes dimidiata E. Mey. Ex. Arn (Icacinaceae), a widely used plant in Zulu traditional medicine, is reported to possess antioxidant activity. Objective To investigate the chemopreventive efficacy of methanol extract of A. dimidiata leaf (AMF). Materials and methods Antimutagenic potential of AMF (25, 50 and 75 μg/plate) was evaluated by the Ames test. The ability of AMF (100 and 250 mg/kg orally) on restoration of depleted antioxidant status by sodium fluoride (NaF) was analysed on BALB/c mice. 7,12-Dimethylbenz[a]anthracene/croton oil induced mouse skin papilloma model was studied up to 20 weeks to analyse the anticarcinogenic effect of AMF (1%, 3% and 5% topically, twice weekly for 6 weeks). Phytochemicals of AMF were characterized by GC-MS. Results AMF (75 μg/plate) reverted 4-nitro-o-phenylenediamine (NPDA) induced mutations in Salmonella typhimurium strains, TA 98, 100 and 102 by 74.8%, 72.5% and 69.3%, respectively. Against sodium azide, the percentage reversion was 80.4, 71.3 and 71.3. In mice, AMF (250 mg/kg for 4 days) increased the serum superoxide dismutase (SOD) and catalase activities by 48.71% and 30.3% against the NaF-induced drop. GSH level was improved by 48.59% with a concomitant decrease in TBARS (57.67%). The skin papilloma reduction was 79.32% for 5% AMF. Squalene, dodecanoic, tetradecanoic and hexadecanoic acids are the known antioxidant and chemopreventive molecules identified by GC-MS. Discussion and conclusion Antioxidant and antimutagenic activities of AMF might have contributed to its anticarcinogenic potential.

A 26-Week Carcinogenicity Study of 2-Amino-3-Methylimidazo[4,5-f]Quinoline in rasH2 Mice

To evaluate the carcinogenic susceptibility of rasH2 mice to 2-amino-3-methylimidazo[4,5- f ]quinoline (IQ), 7-week-old rasH2 mice and their wild-type littermates (non-Tg mice) of both the sexes were fed a diet containing 0 or 300 ppm IQ for 26 weeks. Microscopical examinations revealed that the proliferative lesions of the forestomach, including squamous cell hyperplasias, papillomas, and carcinomas, were frequently encountered in male and female rasH2 mice fed with IQ. In non-Tg mice, no significant differences in the incidence of forestomach lesions were observed between the 0 ppm and 300 ppm groups. Histopathological changes such as periportal hepatocellular hypertrophy and oval cell proliferation in the liver were more apparent in female rasH2 and non-Tg mice than in males, and the incidence of hepatocellular altered foci significantly increased in female rasH2 mice in the 300 ppm group as compared to that in the 0 ppm group. These results suggest that the carcinogenic potential of IQ can be detected in rasH2 mice by a 26-week, short-term carcinogenicity test.

Loss of endogenous Nfatc1 reduces the rate of DMBA/TPA-induced skin tumorigenesis

Immunosuppressive therapies using calcineurin inhibitors, such as cyclosporine A, are associated with a higher incidence of squamous cell carcinoma formation in mice and humans. Calcineurin is believed to suppress tumorigenesis in part through Nfatc1, a transcription factor expressed primarily in hair follicle bulge stem cells in mice. However, mice overexpressing a constitutively active Nfatc1 isoform in the skin epithelium developed increased spontaneous skin squamous cell carcinomas. Because follicular stem cells can contribute to skin tumorigenesis, whether the endogenous expression of Nfatc1 inhibits or enhances skin tumorigenesis is unclear. Here we show that loss of the endogenous expression of Nfatc1 suppresses the rate of DMBA/TPA-induced skin tumorigenesis. Inducible deletion of Nfatc1 in follicular stem cells before tumor initiation significantly reduces the rate of tumorigenesis and the contribution of follicular stem cells to skin tumors. We find that skin tumors from mice lacking Nfatc1 display reduced Hras codon 61 mutations. Furthermore, Nfatc1 enhances the expression of genes involved in DMBA metabolism and increases DMBA-induced DNA damage in keratinocytes. Together these data implicate Nfatc1 in the regulation of skin stem cell-initiated tumorigenesis via the regulation of DMBA metabolism.

UCP2 knockout suppresses mouse skin carcinogenesis

Mitochondrial uncoupling (uncouples electron transport from ATP production) has recently been proposed as a novel survival mechanism for cancer cells, and reduction in free radical generation is the accepted mechanism of action. However, there is no direct evidence supporting that uncoupling proteins promote carcinogenesis. Herein, we examined whether mitochondrial uncoupling affects mouse skin carcinogenesis using uncoupling protein 2 (UCP2) homozygous knockout and wild-type mice. The results indicate that knockout of Ucp2 significantly reduced the formation of both benign (papilloma) and malignant (squamous cell carcinoma) tumors. UCP2 knockout did not cause increases in apoptosis during skin carcinogenesis. The rates of oxygen consumption were decreased only in the carcinogen-treated UCP2 knockout mice, whereas glycolysis was increased only in the carcinogen-treated wild-type mice. Finally, the levels of metabolites pyruvate, malate, and succinate showed different trends after carcinogen treatments between the wild-type and UCP2 knockout mice. Our study is the first to demonstrate that Ucp2 knockout suppresses carcinogenesis in vivo. Together with early studies showing that UCP2 is overexpressed in a number of human cancers, UCP2 could be a potential target for cancer prevention and/or therapy. Cancer Prev Res; 8(6); 487-91. ©2015 AACR.

Inflammasome activation is critical to the protective immune response during chemically induced squamous cell carcinoma

Chronic inflammation affects most stages of tumorigenesis, including initiation, promotion, malignant differentiation, invasion and metastasis. Inflammasomes have been described as involved with persistent inflammation and are known to exert both pro and antitumour effects. We evaluated the influence of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase (CASP)-1 in the antitumor immune response using a multistage model of squamous cell carcinoma (SCC) development. Absence of ASC and CASP-1 resulted in an earlier incidence and increased number of papilloma. Loss of inflammassome function in mice resulted in decreased presence of natural killer (NK), dendritic (DC), CD4⁺, CD8⁺ and CD45RB⁺ T cells in the tumor lesions as well as in lymph nodes (LN) compared with WT mice. Increased percentage of CD4⁺CD25⁺Foxp3⁺ T cells was associated with association with inflammasome loss of function. Moreover, significant differences were also found with neutrophils and macrophage infiltrating the lesions. Myeloperoxidase (MPO), but not elastase (ELA), activity oscillated among the groups during the SCC development. Levels of proinflammatory cytokines IL-1β, IL-18, Tumor Necrosis Factor (TNF)-α and Interferon (IFN)-γ were decreased in the tumor microenvironment in the absence of inflammasome proteins. These observations suggest a link between inflammasome function and SCC tumorigenesis, indicating an important role for inflammasome activation in the control of SCC development.

Chemopreventive potential of Apium leptophyllum (Pers.) against DMBA induced skin carcinogenesis model by modulatory influence on biochemical and antioxidant biomarkers in Swiss mice

AIM

The study was designed to investigate the chemopreventive potential of flavonoidal fractions of Apium leptophyllum fruits (FFALF) on Swiss mice.

MATERIALS AND METHODS

Skin tumor or papilloma was developed by topical application of DMBA (25 μg in 0.1 ml acetone) on intrascapular region of mice, twice weekly for 8 weeks. The animals were divided into six groups: Group I (vehicle control); group II (FFALF control, 5 mg/kg); group III (carcinogenic control, DMBA treated initially for 8 weeks); and group IV, V and VI as pre-treated group (FFALF 5, 10 and 20 mg/kg respectively for 16 weeks along with DMBA treatment). After the 16(th) week of treatment; the tumor morphology, skin histopathology, and biochemical and antioxidant biomarkers were measured and compared with carcinogenic control as well as vehicle control.

RESULTS

The co-administration of FFALF with DMBA-treated groups showed significant (P ≤ 0.001) prevention against skin papilloma and normalized the status of lipid peroxidation with antioxidant biomarkers in a dose-dependent manner as compared to carcinogenic control.

CONCLUSIONS

Thus, the present study suggests that the FFALF is non-carcinogenic and has chemopreventive potential on DMBA-induced carcinogenesis in mouse, which may be due to the modulation of cutaneous lipid peroxidation or enhancement of total antioxidant capacity.

Meis1 regulates epidermal stem cells and is required for skin tumorigenesis

Previous studies have shown that Meis1 plays an important role in blood development and vascular homeostasis, and can induce blood cancers, such as leukemia. However, its role in epithelia remains largely unknown. Here, we uncover two roles for Meis1 in the epidermis: as a critical regulator of epidermal homeostasis in normal tissues and as a proto-oncogenic factor in neoplastic tissues. In normal epidermis, we show that Meis1 is predominantly expressed in the bulge region of the hair follicles where multipotent adult stem cells reside, and that the number of these stem cells is reduced when Meis1 is deleted in the epidermal tissue of mice. Mice with epidermal deletion of Meis1 developed significantly fewer DMBA/TPA-induced benign and malignant tumors compared with wild-type mice, suggesting that Meis1 plays a role in both tumor development and malignant progression. This is consistent with the observation that Meis1 expression increases as tumors progress from benign papillomas to malignant carcinomas. Interestingly, we found that Meis1 localization was altered to neoplasia development. Instead of being localized to the stem cell region, Meis1 is localized to more differentiated cells in tumor tissues. These findings suggest that, during the transformation from normal to neoplastic tissues, a functional switch occurs in Meis1.

Congenic mapping and allele-specific alteration analysis of Stmm1 locus conferring resistance to early-stage chemically induced skin papillomas

Genome-wide association studies have revealed that many low-penetrance cancer susceptibility loci are located throughout the genome; however, a very limited number of genes have been identified so far. Using a forward genetics approach to map such loci in a mouse skin cancer model, we previously identified strong genetic loci conferring resistance to early-stage chemically induced skin papillomas on chromosome 7 with a large number of [(FVB/N×MSM/Ms)×FVB/N] F1 backcross mice. In this report, we describe a combination of congenic mapping and allele-specific alteration analysis of the loci on chromosome 7. We used linkage analysis and congenic mouse strains to refine the location of Stmm1 (Skin tumor modifier of MSM 1) locus within a genetic interval of about 3 cM on proximal chromosome 7. In addition, we used patterns of allele-specific imbalances in tumors from F1 backcross and N10 congenic mice to narrow down further the region of Stmm1 locus to a physical distance of about 5.4 Mb. To gain the insight into the function of Stmm1 locus, we carried out a long term BrdU labelling experiments with congenic mice containing Stmm1 locus. Interestingly, we observed a decrease of BrdU-LRCs (Label Retaining Cells) in a congenic strain heterozygous or homozygous for MSM allele of Stmm1. These results suggest that Stmm1 responsible genes may have an influence on papillomagenesis in the two-stage skin carcinogenesis by regulating epidermal quiescent stem cells.

Does increase in DNA repair allow "tolerance-to-insult" in chemical carcinogenesis? Skin tumor experiments with MGMT-overexpressing mice

Several genotoxicity endpoints have been evaluated to define nonlinear dose-responses for SN 1 and SN 2 alkylating genotoxicants. Dose-response studies acknowledging the process of multistage tumorigenesis are important; however, data pertaining nonlinearity are not yet available. In this communication, the role of DNA repair in the dose-response relationship for benign papillomas was examined using the two-stage skin carcinogenesis protocol. The data obtained with O(6) -methylguanine-DNA methyltransferase (MGMT) overexpressing mice in which papillomas were induced by a single topical treatment with N-methyl-N-nitrosourea (MNU) followed by promotion with 12-O-tetradecanoylphorbol-13-acetate are reported. As MGMT efficiently protects cells from mutations by repairing O(6) -methylguanine, a miscoding lesion induced by MNU, the question whether MGMT is able to nullify carcinogenic lesions to an extent where they would be considered nonhazardous has been addressed. It is shown here that MGMT overexpression significantly protects against, but does not completely nullify, the effect of MNU in tumor initiation. The possible mechanisms involved have also been discussed.

Loss of Grainy head-like 1 is associated with disruption of the epidermal barrier and squamous cell carcinoma of the skin

The Grainyhead-like 1 (GRHL1) transcription factor regulates the expression of desmosomal cadherin desmoglein 1 (Dsg1) in suprabasal layers of the epidermis. As a consequence, the epidermis of Grhl1-null mice displays fewer desmosomes that are abnormal in structure. These mice also exhibit mild chronic skin barrier defects as evidenced by altered keratinocyte terminal differentiation, increased expression of inflammatory markers and infiltration of the skin by immune cells. Exposure of Grhl1^−/− mice to a standard chemical skin carcinogenesis protocol results in development of fewer papillomas than in wild type control animals, but with a rate of conversion to squamous cell carcinoma (SCC) that is strikingly higher than in normal littermates. The underlying molecular mechanism differs from mice with conditional ablation of a closely related Grhl family member, Grhl3, in the skin, which develop SCC due to the loss of expression of phosphatase and tensin homolog (PTEN) and activation of the phosphatidylinositol 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) signaling pathway.

IL-13 but not IL-4 signaling via IL-4Rα protects mice from papilloma formation during DMBA/TPA two-step skin carcinogenesis

Interleukin 4 (IL-4) was shown to be tumor-promoting in full carcinogenesis studies using 3-methylcholanthrene (MCA). Because heretofore the role of IL-4 in DMBA/TPA (9,10-dimethyl-1,2-benz-anthracene/12-O-tetradecanoylphorbol-13-acetate) two-stage carcinogenesis was not studied, we performed such experiments using either IL-4(-/-) or IL-4Rα(-/-) mice. We found that IL-4Rα(-/-) but not IL-4(-/-) mice have enhanced papilloma formation, suggesting that IL-13 may be involved. Indeed, IL-13(-/-) mice developed more papillomas after exposure to DMBA/TPA than their heterozygous IL-13-competent littermate controls. However, when tested in a full carcinogenesis experiment, exposure of mice to 25 μg of MCA, both IL-13(-/-) and IL-13(+/-) mice led to the same incidence of tumors. While IL-4 enhances MCA carcinogenesis, it does not play a measurable role in our DMBA/TPA carcinogenesis experiments. Conversely, IL-13 does not affect MCA carcinogenesis but protects mice from DMBA/TPA carcinogenesis. One possible explanation is that IL-4 and IL-13, although they share a common IL-4Rα chain, regulate signaling in target cells differently by employing distinct JAK/STAT-mediated signaling pathways downstream of IL-13 or IL-4 receptor complexes, resulting in different inflammatory transcriptional programs. Taken together, our results indicate that the course of DMBA/TPA- and MCA-induced carcinogenesis is affected differently by IL-4 versus IL-13-mediated inflammatory cascades.

A role for NF-κB activity in skin hyperplasia and the development of keratoacanthomata in mice

BACKGROUND

Previous studies have implicated NF-κB signaling in both cutaneous development and oncogenesis. However, these studies have been limited in part by the lethality that results from extreme over- or under-expression of NF-κB in available mouse models. Even cre-driven tissue specific expression of transgenes, or targeted deletion of NF-κB can cause cell death. Therefore, the present study was undertaken to evaluate a novel mouse model of enhanced NF-κB activity in the skin.

METHODS

A knock-in homologous recombination technique was utilized to develop a mouse model (referred to as PD mice) with increased NF-κB activity.

RESULTS

The data show that increased NF-κB activity leads to hyperproliferation and dysplasia of the mouse epidermis. Chemical carcinogenesis in the context of enhanced NF-κB activity promotes the development of keratoacanthomata.

CONCLUSION

Our findings support an important role for NF-κB in keratinocyte dysplasia. We have found that enhanced NF-κB activity renders keratinocytes susceptible to hyperproliferation and keratoacanthoma (KA) development but is not sufficient for transformation and SCC development. We therefore propose that NF-κB activation in the absence of additional oncogenic events can promote TNF-dependent, actinic keratosis-like dysplasia and TNF-independent, KAs upon chemical carcinogensis. These studies suggest that resolution of KA cannot occur when NF-κB activation is constitutively enforced.

Effects of two disiloxanes ALIS-409 and ALIS-421 on chemoprevention in model experiments

Morpholino-disiloxane (ALIS-409) and piperazino-disiloxane (ALIS-421) compounds were developed as inhibitors of multidrug resistance of various types of cancer cells. In the present study, the effects of ALIS-409 and ALIS-421 compounds were investigated on cancer promotion and on co-existence of tumor and normal cells. The two compounds were evaluated for their inhibitory effects on Epstein-Barr virus immediate-early antigen (EBV-EA) expression induced by tetradecanoyl-phorbol-acetate (TPA) in Raji cell cultures. The method is known as a primary screening test for antitumor effect, below the (IC50) concentration. ALIS-409 was more effective in inhibiting EBV-EA (100 μg/ml) and tumor promotion, than ALIS-421, in the concentration range up to 1000 μg/ml. However, neither of the compounds were able to reduce tumor promotion significantly, expressed as inhibition of TPA-induced tumor antigen activation. Based on the in vitro results, the two disiloxanes were investigated in vivo for their effects on mouse skin tumors in a two-stage mouse skin carcinogenesis study. The application of dimethyl-benzanthracene (DMBA; 390 nmol) as a tumor initiator was followed by exposure to TPA (1.7 nmol/l) as a tumor promoter. The experiments showed that ALIS-409 at a concentration of 85 nmol/l had a weak EBV-EA inhibitory effect in vitro and a moderate antitumor activity, compared to the positive control of DMBA plus TPA-treated mice. Flow cytometry by differential staining demonstrated interactions in co-cultures of MCF7 breast cancer and MRC5 human lung fibroblasts. The growth rate of tumor cells in mixed populations of MCF7 breast cancer and MRC5 normal fibroblast cells was reduced in the presence of ALIS-409, as compared to the control non-treated cell populations. The two disiloxanes were moderately-effective in chemoprevention in DMBA-induced and TPA-promoted in vivo tumor formation. Authors suggest that the inhibition of tumor cell and fibroblast interaction by ALIS409 might have some perspective in the development of anti-stromal therapy.

Study on extraction process of tannins from Semen Cuscutae and their anti-papilloma activity

The objective of this paper was to study the extraction methods of tannin constituents from Semen Cuscutae and their anti-papilloma effects. Single factor test and orthogonal design methods were used to determine the optimal extraction method; the mouse skin papilloma model induced by DMBA/croton oil was established, which was a classic two-stage carcinogenesis model being used to observe and evaluate the anti-carcinogenic effects of tannins extracted from Semen Cuscutae in different stages. The optimal extraction method of Semen Cuscutae was a 20-fold volume of solvent, a temperature of 50 °C, three times of extraction, with 20 min each, skin papilloma experiment revealed that the number of bearing tumors gradually reduced, and the inhibition rate gradually increased with the increase of dose, in the high-dose group, its inhibition rate reached 70.2%. Tannin extract from Semen Cuscutae has an obvious inhibitory effect on skin papilloma development.

Toxicology and carcinogenesis studies of pyrogallol (CAS No. 87-66-1) in F344/N rats and B6C3F1/N mice (dermal studies)

The current main commercial use of pyrogallol is the production of pharmaceuticals and pesticides. In analytical chemistry, pyrogallol is used as a complexing agent, reducing agent, and, in alkaline solution, as an indicator of gaseous oxygen. Pyrogallol was nominated for testing by private individuals based on its frequent occurrence in natural and manufactured products, including hair dyes, and the apparent lack of carcinogenicity data. Male and female F344/N rats and B6C3F1/N mice were administered pyrogallol (99% pure) dermally for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats received dermal applications of pyrogallol in 95% ethanol at doses of 0, 9.5, 18.75, 37.5, 75, or 150 mg pyrogallol/kg body weight, 5 days per week for 14 weeks. Additional groups of 10 male and 10 female special study rats were administered the same doses, 5 days per week for 23 days. All rats survived until the end of the study except for one vehicle control female. Mean body weights of dosed groups of males and females were generally similar to those of the vehicle controls. Chemical-related clinical findings included brown staining and irritation of the skin at the site of application. There were no changes in the hematology, serum clinical chemistry, thyroid hormone values, or organ weights attributable to the dermal administration of pyrogallol. The incidences of squamous hyperplasia, hyperkeratosis, and chronic active inflammation of the skin at the site of application were significantly increased in all dosed groups of males and females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice received dermal applications of pyrogallol in 95% ethanol at doses of 0, 38, 75, 150, 300, or 600 mg pyrogallol/kg body weight, 5 days per week for 14 weeks. All mice survived until the end of the study. Mean body weights of dosed groups of males and females were similar to those of the vehicle controls. Chemical-related clinical findings included brown staining and irritation at the site of application. There were no changes in the hematology values or organ weights attributable to the dermal administration of pyrogallol. The incidences of squamous hyperplasia, hyperkeratosis, and chronic active inflammation of the skin at the site of application were significantly increased in all dosed groups of males and females. The incidence of hematopoietic cell proliferation of the spleen in 600 mg/kg males was significantly greater than that in the vehicle control group. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats received dermal applications of pyrogallol in 95% ethanol at doses of 0, 5, 20, or 75 mg pyrogallol/kg body weight, 5 days per week for up to 104 weeks. Survival of dosed groups of male and female rats was similar to that of the vehicle control groups. Mean body weights of dosed male and female rats were similar to those of the vehicle control groups throughout the study. Irritation of the skin at the site of application was the only chemical-related clinical finding and occurred in the 20 and 75 mg/kg groups. In the skin at the site of application, there were significant increases in the incidences of hyperplasia in all dosed groups of males and females, hyperkeratosis in 20 and 75 mg/kg males and all dosed groups of females, inflammation in 75 mg/kg males and 20 and 75 mg/kg females, and sebaceous gland hyperplasia in 20 and 75 mg/kg males and females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice received dermal applications of pyrogallol in 95% ethanol at doses of 0, 5, 20, or 75 mg pyrogallol/kg body weight, 5 days per week for up to 105 weeks. Survival of dosed groups of male mice was similar to that of the vehicle control group. Survival was significantly decreased in 75 mg/kg females; most early deaths in this group were due to ulcers at or adjacent to the site of application. The mean body weights of 75 mg/kg female mice were generally over 10% less than those of the vehicle controls during year 2 of the study. Irritation and/or ulceration of the skin at the site of application were the only chemical-related clinical findings and occurred predominantly in the 20 and 75 mg/kg groups. In the skin at the site of application, the incidence of squamous cell carcinoma in 75 mg/kg females was significantly greater than that in the vehicle control group. Two 75 mg/kg males had squamous cell papillomas; squamous cell papillomas have not been observed in historical control male mice in four ethanol dermal studies. Increased incidences of nonneoplastic lesions at the site of application included hyperplasia and hyperkeratosis in all dosed groups; inflammation, fibrosis, and pigmentation in the 20 and 75 mg/kg groups; and sebaceous gland hyperplasia and ulcer in the 75 mg/kg groups. Similar lesions in the skin of the neck and back immediately adjacent to the site of application were observed; the incidences of hyperplasia, hyperkeratosis, ulcer, inflammation, and fibrosis at these sites were significantly increased in 75 mg/kg male and female mice, and the incidence of sebaceous gland hyperplasia was significantly increased in 75 mg/kg female mice. Dermal application of pyrogallol also resulted in significant increases in the incidences of bone marrow hyperplasia in males and females and lymphoid hyperplasia of the axillary, inguinal, and mandibular lymph nodes; adrenal cortical hematopoietic cell proliferation; and mammary gland hyperplasia in females.

GENETIC TOXICOLOGY

Pyrogallol was tested in two independent bacterial mutation studies; both studies gave positive results in one or more strains of S. typhimurium or E. coli. In the first study, positive results were seen in S. typhimurium strain TA100 with and without S9 exogenous metabolic activation, and negative results were obtained in strain TA98. In the second study, which was conducted with the same lot of pyrogallol that was used in the 3-month and 2-year studies, positive results were obtained in S. typhimurium strains TA98, TA100, and in E. coli strain WP2 uvrA/pKM101 in the absence of S9. With S9, this sample of pyrogallol was mutagenic in the E. coli strain but gave equivocal responses in S. typhimurium strains TA98 and TA100. In vivo, a micronucleus test that measured frequency of micronucleated polychromatic erythrocytes in bone marrow of male B6C3F1/N mice following three intraperitoneal injections of pyrogallol, gave negative results. In a second in vivo test, no increase in the frequency of micronucleated erythrocytes was observed in the peripheral blood of female B6C3F1/N mice treated with pyrogallol via dermal application for 3 months; in male mice, however, results were equivocal, based on a significant increase in micronucleated erythrocytes observed at a single dose level at the end of the 3-month study.

CONCLUSIONS

Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of pyrogallol in male or female F344/N rats administered 5, 20, or 75 mg/kg. There was equivocal evidence of carcinogenic activity of pyrogallol in male B6C3F1/N mice based on increased incidences of squamous cell papilloma of the skin at the site of application. There was some evidence of carcinogenic activity of pyrogallol in female B6C3F1/N mice based on increased incidences of squamous cell carcinoma of the skin at the site of application. Dermal administration of pyrogallol caused increased incidences of nonneoplastic lesions of the skin at the site of application in male and female rats and mice, skin adjacent to the site of application in male and female mice, and mammary gland in female mice.

Inhibition of CXCR2 profoundly suppresses inflammation-driven and spontaneous tumorigenesis

The chemokine receptor CXCR2 is a key mediator of neutrophil migration that also plays a role in tumor development. However, CXCR2 influences tumors through multiple mechanisms and might promote or inhibit tumor development depending on context. Here, we used several mouse models of spontaneous and inflammation-driven neoplasia to define indispensable roles for CXCR2 in benign and malignant tumors. CXCR2-activating chemokines were part of the secretome of cultured primary benign intestinal adenomas (ApcMin/+) and highly expressed by all tumors in all models. CXCR2 deficiency profoundly suppressed inflammation-driven tumorigenesis in skin and intestine as well as spontaneous adenocarcinoma formation in a model of invasive intestinal adenocarcinoma (AhCreER;Apcfl/+;Ptenfl/fl mice). Pepducin-mediated CXCR2 inhibition reduced tumorigenesis in ApcMin/+ mice. Ly6G+ neutrophils were the dominant source of CXCR2 in blood, and CXCR2 deficiency attenuated neutrophil recruitment. Moreover, systemic Ly6G+ cell depletion purged CXCR2-dependent tumor-associated leukocytes, suppressed established skin tumor growth and colitis-associated tumorigenesis, and reduced ApcMin/+ adenoma formation. CXCR2 is thus a potent protumorigenic chemokine receptor that directs recruitment of tumor-promoting leukocytes into tissues during tumor-inducing and tumor-driven inflammation. Similar leukocyte populations were also found in human intestinal adenomas, which suggests that CXCR2 antagonists may have therapeutic and prophylactic potential in the treatment of cancer.

JWA deficiency suppresses dimethylbenz[a]anthracene-phorbol ester induced skin papillomas via inactivation of MAPK pathway in mice

Our previous studies indicated that JWA plays an important role in DNA damage repair, cell migration, and regulation of MAPKs. In this study, we investigated the role of JWA in chemical carcinogenesis using conditional JWA knockout (JWA^Δ2/Δ2) mice and two-stage model of skin carcinogenesis. Our results indicated that JWA^Δ2/Δ2 mice were resistant to the development of skin papillomas initiated by 7, 12-dimethylbenz(a)anthracene (DMBA) followed by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). In JWA^Δ2/Δ2 mice, the induction of papilloma was delayed, and the tumor number and size were reduced. In primary keratinocytes from JWA^Δ2/Δ2 mice, DMBA exposure induced more intensive DNA damage, while TPA-promoted cell proliferation was reduced. The further mechanistic studies showed that JWA deficiency blocked TPA-induced activation of MAPKs and its downstream transcription factor Elk1 both in vitro and in vivo. JWA^Δ2/Δ2 mice are resistance to tumorigenesis induced by DMBA/TPA probably through inhibition of transcription factor Elk1 via MAPKs. These results highlight the importance of JWA in skin homeostasis and in the process of skin tumor development.

Chk1 is essential for chemical carcinogen-induced mouse skin tumorigenesis

Chk1 is a key regulator of DNA damage checkpoint responses and genome stability in eukaryotes. To better understand how checkpoint proficiency relates to cancer development, we investigated the effects of genetic ablation of Chk1 in the mouse skin on tumors induced by chemical carcinogens. We found that homozygous deletion of Chk1 immediately before carcinogen exposure strongly suppressed benign tumor (papilloma) formation, and that the few, small lesions that formed in the ablated skin always retained Chk1 expression. Remarkably, Chk1 deletion rapidly triggered spontaneous cell proliferation, γ-H2AX staining and apoptosis within the hair follicle, a principal site of origin for carcinogen-induced tumors. At later times, the ablated skin was progressively repopulated by non-recombined Chk1-expressing cells and ultimately normal sensitivity to tumor induction was restored when carcinogen treatment was delayed. In marked contrast, papillomas formed normally in Chk1 hemizygous skin but showed an increased propensity to progress to carcinoma. Thus, complete loss of Chk1 is incompatible with epithelial tumorigenesis, whereas partial loss of function (haploinsufficiency) fosters benign malignant tumor progression.

Anticancer efficacy of perillyl alcohol-bearing PLGA microparticles

In the present study, a novel poly-lactic glycolic acid (PLGA)-based microparticle formulation of perillyl alcohol (POH) was prepared and characterized. Further, its efficacy was evaluated against di-methyl benzo anthracene-induced skin papilloma in Swiss albino mice. The characterization studies showed that POH-bearing PLGA microparticles were of the size 768 ± 215 nm with a ζ-potential value of -7.56 ± 0.88 mV. The entrapment efficiency of the active drug in particles was 42.4% ± 3.5%. POH-bearing PLGA microparticles were stable and released entrapped drug gradually over an extended time period. The in vitro efficacy of POH-bearing PLGA microparticles was evaluated by examining their differential cytotoxicity and assessing their ability to inhibit epidermoid carcinoma cell line (A253). The POH-based microparticles when administered to tumor-bearing animals caused greater tumor regression and increased survival rate (∼80%) as compared with the group receiving free form of POH (survival rate 40%). The superiority of POH-PLGA microparticles over free form of POH was further evident from their ability to modulate apoptosis-regulating factors.

Detection of the onset of ischemia and carcinogenesis by hypoxia-inducible transcription factor-based in vivo bioluminescence imaging

An animal model for the early detection of common fatal diseases such as ischemic diseases and cancer is desirable for the development of new drugs and treatment strategies. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that regulates oxygen homeostasis and plays key roles in a number of diseases, including cancer. Here, we established transgenic (Tg) mice that carry HRE/ODD-luciferase (HOL) gene, which generates bioluminescence in an HIF-1-dependent manner and was successfully used in this study to monitor HIF-1 activity in ischemic tissues. To monitor carcinogenesis in vivo, we mated HOL mice with rasH2 Tg mice, which are highly sensitive to carcinogens and are used for short-term carcinogenicity assessments. After rasH2-HOL Tg mice were treated with N-methyl-N-nitrosourea, bioluminescence was detected noninvasively as early as 9 weeks in tissues that contained papillomas and malignant lesions. These results suggest that the Tg mouse lines we established hold significant potential for monitoring the early onset of both ischemia and carcinogenesis and that these lines will be useful for screening chemicals for carcinogenic potential.

Chemomodulatory potential of Glycine max against murine skin and cervical papillomagenesis

In the present study, chemopreventive potential of Glycine max (G. Max) seeds was examined against DMBA-induced skin and MCA-induced cervical papillomagenesis in Swiss albino mice. Different doses (2.5, 5, and 7.5% w/w) of G. max were provided to animals in feed. Results exhibited a significant reduction in skin as well as cervical tumor incidence and tumor multiplicity (up to 75%) at all doses of test diet as compared to the control. Relatively, 7.5% test diet was most effective in protecting the animals against carcinogenesis. Further, detoxifying enzymes and antioxidative status was also evaluated in the liver of mice to understand the role of G. max in prevention of cancer. It was observed that the test diet containing G. max significantly elevated the specific activities of glutathione-S-transferase (GST), DT-diaphorase (DTD), superoxide dismutase (SOD), catalase (CAT), and glyoxalase I (Gly I). The test diet also elevated the content of reduced glutathione whereas it decreased the level of the peroxidative damage along with the specific activity of lactate dehydrogenase. It appeared that G. max seeds provided chemoprevention against skin and cervical papillomagenesis probably by modulating the detoxifying and antioxidative enzymes. It could be inferred that intake of G. max might help in reducing the risk of cancer.

Chemopreventive effects of wild carrot oil against 7,12-dimethyl benz(a)anthracene-induced squamous cell carcinoma in mice

CONTEXT

Daucus carota L. ssp. carota (Apiacea) is widely distributed throughout the world and has many uses in traditional medicine.

OBJECTIVE

The present study investigates the chemopreventive effects of oil extract of D. carota umbels on 7,12-dimethyl benz(a)anthracene (DMBA)-induced skin cancer in mice.

MATERIALS AND METHODS

D. carota oil extract (DCOE) was prepared by extracting the dried umbels with 50:50 acetone:methanol. Skin papilloma were initiated by DMBA and promoted by 12-O-tetradecanoyl phorobol-13-acetate (TPA). The extract was administered to animals via gavage (0.02 mL of 100% oil), intraperitoneal (0.3 mL of 2% oil), and topical (0.2 mL of 5, 50, and 100% oil) routes for 20 weeks. Tumor appearance, incidence, yield, and volume were compared with those of a non-treated control group.

RESULTS

Topical 100% treatment delayed tumor appearance, and inhibited tumor incidence and yield by 40 and 89%, respectively. Topical 50% treatment inhibited tumor incidence and yield by 30 and 83%, respectively, whereas the 5% treatment inhibited tumor yield by 36%. Tumor volume was decreased by 99, 91, and 70% following topical treatments with 100, 50, and 5% oil, respectively. Intraperitoneal treatment inhibited tumor yield by 43%, and decreased tumor volume by 85%, whereas gavage treatment showed minimal effects on both. Intraperitoneal and topical treatment decreased infiltration and hyperplasia with an increase in the level of hyperkeratosis.

CONCLUSION

These findings demonstrate that DCOE has remarkable antitumor activity against DMBA-induced skin cancer compared with non-treated animals paving the ground for further investigations.

Decreased incidence of papillomas in mice with impaired EGFR function during multi-stage skin carcinogenesis

Genetically modified mouse lines revealed that the epidermal growth factor receptor (EGFR) is essential for the development and homoeostasis of the epidermis and hair follicles. However, more detailed studies have been precluded by the shortened lifespan of Egfr knockout mice. We employed the mouse line Wa5 (carrying a point mutation resulting in the expression of a dominant negative receptor) to analyse the impact of significantly reduced EGFR signalling during multi-stage chemical skin carcinogenesis. Seven-week-old Wa5 females and control littermates received a single application of 7,12-dimethylbenz(a)anthracene followed by multiple applications of 12-O-tetradecanoylphorbol-13-acetate for 26 weeks. Wa5 mice remained free of papillomas for a longer time and developed significantly fewer tumors than control littermates. In contrast, the mean tumor size was not different between groups. The present data indicate that EGFR signalling contributes to tumor growth during multi-stage chemical carcinogenesis of the skin in mice possibly by acting as a survival factor for skin tumor cells.

Chemomodulatory effect of Dolichos biflorus Linn. on skin and forestomach papillomagenesis in Swiss albino mice

Effect of consumption of three different doses (2%, 4% and 6%, w/w) of Dolichos biflorus Linn. seeds on hepatic drug metabolizing enzymes, antioxidant enzymes, reduced glutathione content, lactate dehydrogenase and lipid peroxidation in Swiss albino mice has been reported. Anti-carcinogenic effect has been studied by 7,12-dimethylbenzanthracene (DMBA)-induced skin and benzo(a)pyrene[B(a)P]-induced forestomach papillomagenesis models. D. biflorus consumption resulted in a significant increase in hepatic carcinogen metabolizing enzyme systems especially at 4% and 6% doses. Significant increase in reduced glutathione content (GSH) and specific activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GR) in liver of mice, at 4% and 6% doses has been reported. Lactate dehydrogensae (LDH) activity and peroxidative damage has been significantly decreased at 4% and 6% doses. In skin papillomagenesis model, 4% and 6% dose in diet significantly reduced the tumor incidence (up to 25%), tumor multiplicity (up to 59%) and tumor volume per mouse (up to 70%) as compared to DMBA treated group. Importantly, significant reduction in tumor incidence (up to 33%) and tumor multiplicity (up to 61%) was evident for forestomach papillomagenesis model.

Effect of suppressive oligodeoxynucleotides on the development of inflammation-induced papillomas

Inflammation contributes to the development of papillomas and squamous cell carcinomas in the well-established 7,12-dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-l3-acetate (TPA) model of skin carcinogenesis. Synthetic oligonucleotides (ODN) containing repetitive TTAGGG motifs have been shown to block deleterious inflammatory reactions in murine models of autoimmunity, pneumonitis, and shock. This article examines whether treatment with suppressive (Sup) ODN can interfere with DMBA/TPA-induced inflammation, thereby reducing papilloma formation. Results indicate that Sup ODN block TPA-dependent skin hyperplasia, edema, and leukocytic infiltration. Sup ODN also inhibit the upregulation of genes encoding pro-oncogenic chemokines and other markers of inflammation including CXCL2, CCL2, COX-2, and ODC (ornithine decarboxylase). Of greatest import, Sup ODN reduce papilloma formation in a dose- and sequence-dependent manner. These findings suggest that Sup ODN may provide a novel means of preventing inflammation and associated oncogenesis.

Chemoprevention by Triticum Aestivum of mouse skin carcinogenesis induced by DMBA and croton oil - association with oxidative status

Chemopreventive action of wheat grass (Triticum astivum) leaf extract in Swiss albino mice was evaluated. Oral administration of wheat grass leaf extract at a dose level of 20 ml/kg body weight per day at pre, peri, and post-initional phases and in combination group, caused significant variation in tumour incidence and tumour yield as compared to the control group. Moreover, the average latent period was significantly increased from 9.87 ± 0.12 to 13.4 ± 0.23 weeks in the combination group, together with significant elevation of reduced glutathione (GSH), superoxide dismutase (SOD) catalase (CAT) and reduction in lipid peroxidation (LPO) was observed as compared to the control group.

Suppression of DMBA/croton oil-induced mouse skin tumor promotion by Ardisia Crispa root hexane extract

Ardisia crispa (Family: Myrsinaceae) has been used as a traditional medicine for various ailments. Previous studies showed that Ardisia crispa possesses antimetastatic and anti-inflammatory properties. Nevertheless, research done on the plant is still limited. Therefore, the present study was designed to evaluate the suppression effect of Ardisia crispa root hexane (ACRH) extract on 7, 12-dimethylbenz (α) anthracene (DMBA)-induced mice skin tumor promotion in ICR mice with topical application twice weekly for 10 weeks. Results showed significant difference between treatment groups (mice treated with 30 mg/kg, 100 mg/kg and 300 mg/kg of ACRH extract; denoted as group I, II and III respectively) for tumor incidence and tumor burden (P<0.05). Significant reduction in tumor incidence (20%), tumor burden (1.5 ± 0.50), tumor volume (2.49 ± 1.70) and delayed latency period of tumor formation was observed in group I (30 mg/kg) in comparison to carcinogen control. This study indicates that ACRH extract could be a promising skin tumor promotion suppressing agent at a lower dosage (30 mg/kg). Further studies are required to elucidate the underlying mechanism(s) leading to this effect.

Phellinus rimosus (Berk.) pilat attenuates 7,12-dimethylbenz[a] anthracene induced and croton oil promoted skin papilloma formation in mice

The roles of 7,12-dimethylbenz[a]anthracene (DMBA), a polycyclic aromatic hydrocarbon (PAH), and 12-O-tetradecanoylphorbol-13-acetate (TPA) a skin tumor promoter present in croton oil, are clearly implicated in the formation of skin papilloma. The effect of ethyl acetate extract of Phellinus rimosus, a polypore macro fungus, against croton oil-induced skin inflammation, lipid peroxidation and tumor promotion was studied. The antiinflammatory and lipid peroxidation inhibiting activities were determined by topical application of extract of P. rimosus (10 and 20 mg) prior to the application of 0.1 ml of 50% croton oil in acetone. The tumor promotion inhibiting effect of P. rimosus was evaluated against DMBA-initiated, croton oil promoted two-stage carcinogenesis model in mouse skin. The results showed that topical application of the extract (10 and 20 mg) significantly (p < 0.01) and dose dependently attenuate the inflammatory edema as well as lipid peroxidation induced by croton oil. Similarly, topical application of extract (1 and 5 mg) effectively ameliorated the croton oil promoted skin papilloma formation. The results of this study concluded that ethyl acetate extract of P. rimosus showed antitumor activity against DMBA initiated, croton oil promoted skin papilloma formation which can be partially ascribed to the antiperoxidative and anti-inflammatory effects of the extract.

Ablation of TAK1 upregulates reactive oxygen species and selectively kills tumor cells

TAK1 kinase activates multiple transcription factors and regulates the level of reactive oxygen species (ROS). We have previously reported that ablation of TAK1 in keratinocytes causes hypersensitivity to ROS-induced cell apoptosis. It is known that some tumor cells produce ROS at higher levels compared with normal cells. We used inducible epidermal-specific TAK1 knockout mice and examined whether ablation of TAK1 in preexisting skin tumors could cause an increase in ROS and result in tumor cell death. Deletion of tak1 gene in skin tumors caused the accumulation of ROS and increased apoptosis, and skin tumors totally regressed within 5 to 10 days. Normal skin did not exhibit any significant abnormality on tak1 gene deletion. Thus, TAK1 kinase could be a new and effective molecular target for ROS-based tumor killing.

Arsenic exposure in utero and nonepidermal proliferative response in adulthood in Tg.AC mice

To expand our knowledge on the transplacental carcinogenic potential of inorganic arsenic, pregnant Tg.AC mice received drinking water with 0, 42.5, or 85 ppm arsenite from gestation day 8 to 18. After birth, groups (n = 25) of offspring received topical 12-O-tetradecanoyl phorbol-13-acetate (TPA) (2 microg twice a week) for 36 weeks and were killed; nonskin tumors were assessed. Arsenic increased adrenal cortical adenomas (ACAs; 25%-29%) compared with control (0%) independent of TPA in all male groups. Arsenic increased urinary bladder (UB) hyperplasia in males, but only with TPA. Arsenic induced ACAs in all female groups (control 0%; arsenic 17%-26%). Arsenic-treated females had UB hyperplasia in most groups (control 0%; arsenic 26%-32%), with 2 UB papillomas. All arsenic-treated females had uterine hyperplasia (26%-40%; control 4%) independent of TPA, and 3 had uterine tumors. Thus, arsenic in utero rapidly induces ACAs and uterine and UB preneoplasias in Tg.AC mice, showing transplacental carcinogenic potential in yet another strain of mice.

Enhancement of tongue carcinogenesis in Hras128 transgenic rats treated with 4-nitroquinoline 1-oxide

Transgenic rats carrying human c-Ha-ras proto-oncogene (Hras128 rats) have been shown to be highly susceptible to induction of tumors. We have found an early induction of tongue tumors in Hras128 rats treated with 4-nitroquinoline 1-oxide (4NQO). 4NQO was administered to the Hras128 and wild-type Sprague-Dawley (SD) rats for 4 and 8 weeks, respectively. The experiment was terminated at 14 (Hras128 rats) and 28 (SD rats) weeks. Either during or after treatment with 4NQO, dysplastic hyperplasia, papilloma and squamous cell carcinoma were found on the tongue of both Hras128 and wild-type rats, with a higher incidence and multiplicity in Hras128 rats. Treatment of the Hras128 rats with 4NQO significantly increased cell proliferation in the tumor compared to the control rats. In the tongue tumors of the Hras128 rats, there was a significant increase in the mRNA expression levels of cyclin D1 and COX2. To examine whether this experimental system is useful for screening of the candidate agents for cancer preventive effect, nimesulide, a selective COX2 inhibitor, was tested in the present model. Nimesulide significantly decreased total multiplicity of tongue lesions compared to the control rats. Treatment of Hras128 rats with nimesulide caused a significant decrease in the levels of mRNA expression of cyclin D1 and COX2 in the tumor. Therefore, the current 4NQO-induced Hras128 rat tongue carcinogenesis model provides a simple and rapid system for investigating carcinogenesis process and evaluating the effect of possible cancer preventive agents for human tongue cancer.

Chemopreventive action of Syzygium cumini on DMBA-induced skin papillomagenesis in mice

Syzygium cumini L. is widely used for the treatment of diabetes in various parts of India. The protective efficacy of S. cumini seed extract (SCE) against peroxidative damage contributing to skin carcinogenesis in Swiss albino mice was tested in the present study. A single topical application of 7,12-dimethyl benz(a)anthracene (100 microg/100 microl acetone), followed 2 weeks later by repeated application of croton oil (1% in acetone three times a week) and continued till the end of the experiment (i.e., 16 weeks) caused a 100% tumor incidence. In contrast, mice treated with the SCE (125 mg/ kg/ b.wt./ animal /day) in either the peri (i.e. 7 days before and 7 days after the application of DMBA) or post-initiation (i.e. from the day of start of croton oil treatment and continued till the end of the experiment) phases demonstrated significant reduction in cumulative numbers of papillomas and tumor incidence (75%). The average latency period in the SCE treated group was also significantly increased (Pre Group - 11.1 weeks; Post Group - 10.9 weeks) as compared with the carcinogen control group (7.9). Results from the present study indicate that the anticarcinogenic activity of SCE during DMBA-induced skin papillomagenesis is mediated through alteration of antioxidant status. Thus, SCE can be considered as a readily accessible, promising novel cancer chemopreventive agent.

Chemopreventive and anticarcinogenic effects of Momordica charantia extract

The aim of the study was to examine whether Momordica fruit extract (MFE) and Momordica leaves extract (MLE) might exert any chemopreventive effect in a two stage protocol in skin carcinogenesis with Swiss albino mice. The tumour incidence, tumour yield, tumour burden and cumulative no. of papillomas were found to be higher in the controls (without either extract) as compared to the MFE or MLE treated experimental groups. In a melanoma model, the mice which received fruit and leaf extracts of Momordica at the doses of 500 and 1000 mg/kg body weight for 30 days showed increase in life span of animals and tumour volume was significantly reduced as compared to control values. In cytogenetic studies, a single application of Momordica extracts at doses of 500, 1000 and 1500 mg/kg body weight, 24 hours prior the i.p. administration of cyclophosphamide, significantly prevented micronucleus formation and chromosomal aberrations in a dose dependent manner in bone marrow cells of mice. The present study demonstrate chemopreventive potential of Momordica fruit and leaf extracts on DMBA induced skin tumorigenesis, melanoma tumour and cytogenicity.

Anti-tumour, anti-mutagenic and chemomodulatory potential of Chlorophytum borivilianum

In the present investigation anti-tumour, anti-mutagenic and chemomodulatory potential of Chlorophytum borivilianum were evaluated. Chlorophytum borivilianum root extract had no toxic effect up to a dose of 800 mg/kg body weight/day. Significant increase (p<0.05 to p<0.001) in the activity of reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) and a significant decrease in the hepatic MDA level were observed at 100, 400, and 800 mg/kg body weight of Chlorophytum borivilianum root extract when compared with the control value. Skin papillomagenesis studies demonstrated a significant (p<0.001) decrease in cumulative numbers of papilloma, tumour incidence, tumour burden, tumour size and tumour weight and significant (p<0.01) increase in average latent period when the animals received Chlorophytum borivilianum root extract at a dose level of 800 mg/kg body weight/day orally in double distilled water at pre, peri and post initiation stages of carcinogenesis. A significant reduction in the frequency of chromosomal aberration and micronuclei was observed in the treated animals as compared to carcinogen controls. The present investigation suggests that Chlorophytum borivilianum has anti-tumour, anti-mutagenic and chemomodulatory effects.

SnoN functions as a tumour suppressor by inducing premature senescence

SnoN represses TGF-beta signalling to promote cell proliferation and has been defined as a proto-oncogene partly due to its elevated expression in many human cancer cells. Although the anti-tumourigenic activity of SnoN has been suggested, the molecular basis for this has not been defined. We showed here that high levels of SnoN exert anti-oncogenic activity by inducing senescence. SnoN interacts with the promyelocytic leukaemia (PML) protein and is recruited to the PML nuclear bodies where it stabilizes p53, leading to premature senescence. Furthermore, overexpression of SnoN inhibits oncogenic transformation induced by Ras and Myc in vitro and significantly blocks papilloma development in vivo in a carcinogen-induced skin tumourigenesis model. The few papillomas that were developed displayed high levels of senescence and spontaneously regressed. Our study has revealed a novel Smad-independent pathway of SnoN function that mediates its anti-oncogenic activity.

Multi-stage chemical carcinogenesis in mouse skin: fundamentals and applications

For more than 60 years, the chemical induction of tumors in mouse skin has been used to study mechanisms of epithelial carcinogenesis and evaluate modifying factors. In the traditional two-stage skin carcinogenesis model, the initiation phase is accomplished by the application of a sub-carcinogenic dose of a carcinogen. Subsequently, tumor development is elicited by repeated treatment with a tumor-promoting agent. The initiation protocol can be completed within 1-3 h depending on the number of mice used; whereas the promotion phase requires twice weekly treatments (1-2 h) and once weekly tumor palpation (1-2 h) for the duration of the study. Using the protocol described here, a highly reproducible papilloma burden is expected within 10-20 weeks with progression of a portion of the tumors to squamous cell carcinomas within 20-50 weeks. In contrast to complete skin carcinogenesis, the two-stage model allows for greater yield of premalignant lesions, as well as separation of the initiation and promotion phases.

Anticarcinogenic effects of Solanum lycopersicum fruit extract on Swiss albino and C57 Bl mice

In the present studies, the effect of Solanum lycopersicum extract on DMBA induced skin papillomas and B6 F10 melanomas was studied. Topical single application of DMBA at the dose of 4 mg/kg b.wt. followed by 1 % croton oil for 16 weeks produced a 100% incidence of skin papillomas which started appearing from the 6th week onwards. The mice which additionally received S. lycopersicum extract at 0.6 g/kg 2 day/week for 16 weeks showed a significant decrease in the number and incidence of tumors (p<0.05), with a delay in their appearance to week 10. Histopathological examination showed well and poorly differentiated squamous cell carcinomas in the group which received DMBA + Croton oil treatment whereas hyperkeratosis and hyperplasia were more prevalent in DMBA + Croton oil + Lycopersicum extract treated animals. In a second experiment the effect of cyclophosphamide alone and in combination with S. lycopersicum extract was studied in B16F10 melanoma tumour bearing mice. The inhibition rate was 25.9% in the cyclophosphamide treated group but this increased to 37.7% with S. lycopersicum. The life span of tumour bearing animals was also increased. Thus in two models, S. lycopersicum extract exerted protective potential against skin tumors.

Carcinogenesis studies of cresols in rats and mice

Cresols, monomethyl derivatives of phenol, are high production chemicals with potential for human exposure. The three isomeric forms of cresol are used individually or in mixtures as disinfectants, preservatives, and solvents or as intermediates in the production of antioxidants, fragrances, herbicides, insecticides, dyes, and explosives. Carcinogenesis studies were conducted in groups of 50 male F344/N rats and 50 female B6C3F1 mice exposed to a 60:40 mixture of m- and p-cresols (m-/p-cresol) in feed. Rats and mice were fed diets containing 0, 1500, 5000, or 15,000 ppm and 0, 1000, 3000, or 10,000 ppm, respectively. Survival of each exposed group was similar to that of their respective control group. Mean body weight gains were depressed in rats exposed to 15,000 ppm and in mice exposed to 3000 ppm and higher. A decrease of 25% over that of controls for the final mean body weight in mice exposed to 10,000 ppm appeared to be associated with lack of palatability of the feed. A marginally increased incidence of renal tubule adenoma was observed in the 15,000-ppm-exposed rats. The increased incidence was not statistically significant, but did exceed the range of historical controls. No increased incidence of hyperplasia of the renal tubules was observed; however, a significantly increased incidence of hyperplasia of the transitional epithelium associated with an increased incidence of nephropathy was observed at the high exposure concentration. The only significantly increased incidence of a neoplastic lesion related to cresol exposure observed in these studies was that of squamous cell papilloma in the forestomach of 10,000-ppm-exposed mice. A definitive association with irritation at the site-of-contact could not be made because of limited evidence of injury to the gastric mucosa at the time of necropsy. However, given the minimal chemical-related neoplastic response in these studies, it was concluded that there was no clear evidence of carcinogenicity in male rats or female mice exposed to the cresol mixture.