DMBA Application Research Articles

Carcinogénesis experimental con 7,12-dimetilbenzantraceno (DMBA) y su inhibición con aceite de oliva virgen extra y dieta con aceitunas maduras (variedad Picual)

DMBA is a carcinogen that induces carcinomas within a few weeks of application. Forty-four male hamsters were divided into four groups: DMBA dissolved in paraffin oil (DMBA-Po), DMBA dissolved in olive oil (DMBA-Oo), paraffin oil and olive oil. Their mouths were swabbed daily with paraffin oil or extra virgin olive oil alternatively for the first two weeks, during the biweekly application of DMBA at 0.5% diluted in paraffin oil or olive oil for five weeks and daily until the twentieth week. The animals in the DMBA-Oo and olive oil groups received an additional diet of mature Picual olives. The DMBA-Po carcinogen effect (35 carcinomas) is 100% and the inhibitory effect 0. The combination of olive oil as DMBA solvent and the ad libitum diet with Picual olive has an inhibitory effect of 80%, with only three intraepithelial carcinomas and four verrucous carcinomas occurring and no invasive carcinomas.

The administration of multipotent stromal cells at precancerous stage precludes tumor growth and epithelial dedifferentiation of oral squamous cell carcinoma

Multipotent stromal cells (MSCs) are envisioned as a powerful therapeutic tool. As they home into tumors, secrete trophic and vasculogenic factors, and suppress immune response their role in carcinogenesis is a matter of controversy. Worldwide oral squamous cell carcinoma (OSCC) is the fifth most common epithelial cancer.Our aim was to determine whether MSC administration at precancerous stage modifies the natural progression of OSCC.OSCC was induced in Syrian hamsters by topical application of DMBA in the buccal pouch. At papilloma stage, the vehicle or 3×106 allogenic bone marrow-derived MSCs were locally administered. Four weeks later, the lesions were studied according to: volume, stratification (histology), proliferation (Ki-67), apoptosis (Caspase 3 cleaved), vasculature (ASMA), inflammation (Leukocyte infiltrate), differentiation (CK1 and CK4) and gene expression profile (mRNA).Tumors found in individuals that received MSCs were smaller than those presented in the vehicle group (87±80 versus 54±62mm3, p<0.05). The rate of proliferation was two times lower and the apoptosis was 2.5 times higher in lesions treated with MSCs than in untreated ones. While the laters presented dedifferentiated cells, the former maintained differentiated cells (cytokeratin and gene expression profile similar to normal tissue).Thus, MSC administration at papilloma stage precludes tumor growth and epithelial dedifferentiation of OSCC.

Prophylaxis of Diallyl Disulfide on Skin Carcinogenic Model via p21-dependent Nrf2 stabilization.

Cancer prevention through intake of biologically active natural products appears to be an accessible way to reduce the risk of cancer. Diallyl disulfide (DADS), a major garlic derivative, has exhibited potential role in cancer therapy. The study is aimed to evaluate the prophylactic effect of DADS in chemically induced mouse skin carcinogenesis and investigate the molecular targets mediated by DADS. Two-stage chemically induced carcinogenesis model by cutaneous application of DMBA and subsequent TPA was established to study the prophylactic effect of DADS. As a result, we observed that DADS dose-dependently attenuated skin tumor incidence and multiplicity in the model mice, which was related to the up-regulation of a bunch of antioxidant enzymes activities and the nuclear accumulation of Nrf2. Furthermore, we developed skin carcinogenesis in Nrf2 knockout mice which could reverse the activity of DADS. Finally, we uncovered the underlying mechanism that DADS promoted the endogenous interaction between p21 and Nrf2, which was critical for impairing the Keap1-mediated degradation of Nrf2. Based on the results, we concluded that DADS was a promising cancer chemoprevention agent and suggested a garlic-rich diet might be beneficial to reduce the cancer risk in our daily life.

Hepatic Arginase - Nitric oxide imbalance: Impact of carcinogenesis and therapeutic effect of sodium channel blockage in an in vivo rat model

Abstract Objective: Nitric oxide synthase and arginase are frequently antagonistic and interactive, although both use L-arginine as common substrate. Their balance is of potential functional importance. How the balance changes in cancer is unknown. Increasing evidence suggests that progression of carcinomas involves functional voltage-gated sodium channel (VGSC) activity. Methods: The present study extended this study to liver and aimed to determine whether (i) DMBA carcinogenesis would affect the activities of arginase and NOS and (ii) treatment with Na-channel blocker RS100642 would ameliorate the impact of the carcinogen on the arginase-NOS balance. Results: DMBA application significantly increased arginase activity and, correspondingly, the level of L-ornithine by 25-33%. In contrast, NOS activity decreased by 11%. Importantly, RS100642 treatment completely suppressed the effect on arginase. Conclusion: It is concluded (i) that DMBA carcinogenesis changes the hepatic arginase-NOS balance, increasing the overall dominance of arginase and (ii) that VGSC inhibition has a protective effect on liver.

Chemomodulatory Potential of Bartogenic Acid Against DMBA/Croton Oil Induced Two-Step Skin Carcinogenesis in Mice.

Barringtonia racemosa fruits are believed to be useful in cancer treatment in Ayurveda, the Indian system of medicine. In present study, bartogenic acid (BA), a triterpenoid constituent of Barringtonia fruits was evaluated for its cytotoxicity property using the human skin carcinoma cell line (SCC-13) and human peripheral blood mononuclear cells (PBMC). The chemopreventive efficacy of BA was evaluated against the DMBA/Croton oil-induced skin carcinogenesis in mice.BA was orally administered at the doses of 1, 2 or 4 mg/kg/day or applied topically every day for 12 weeks following DMBA application. The in vitro data from cell lines revealed that BA induces cytotoxicity against the SCC-13 cells (IC50=7.5 µM). It was found 4.05 times more selective to exert cytotoxicity against SCC-13 as compared to the PBMC (IC50=30.4 µM). The in vivo datacollected from mice model of DMBA/Croton oil-induced skin carcinogenesis revealed that BA administered orally or applied topically, both reduced the precancerous skin lesions andthe incidence of tumor bearing. The oral doses of BA (2 and 4 mg/kg) and topical treatment significantly reduced the incidence and number of skin papillomas. At these doses, BA also increased the activities of catalase and superoxide dismutase and induced an increase in glutathionecontent and inhibited lipid peroxidation in the skin. These findings reveal the chemopreventive efficacy of BA and also demonstrate that it contributes to the cytotoxic and antioxidative effects of Barringtonia racemosa fruits. The study also validates the traditional claims of Barringtonia fruits and provides a scientific basis of its chemopreventive property.

Skin response to a carcinogen involves the xenobiotic receptor pregnane X receptor.

Skin is in daily contact with potentially harmful molecules from the environment such as cigarette smoke, automobile emissions, industrial soot and groundwater. Pregnane X receptor (PXR) is a transcription factor expressed in liver and intestine that is activated by xenobiotic chemicals including drugs and environmental pollutants. Topical application of the tumor initiator 7,12-dimethylbenz(a)anthracene (DMBA) enhances Pxr, Cyp1a1, Cyp1b1 and Cyp3a11, but not Ahr expression in the skin. Surprisingly, DMBA-induced Pxr upregulation is largely impaired in Langerin(+) cell-depleted skin, suggesting that DMBA mainly triggers Pxr in Langerin(+) cells. Furthermore, PXR deficiency protects from DNA damage in epidermal cells but to a lesser extent than aryl hydrocarbon receptor (AHR) deficiency. Interestingly, skin exposure to low doses of DMBA induces migration of PXR-deficient but not of wild-type and AHR-deficient Langerhans cells (LCs). PXR-humanized mice show a marked increase in DNA damage to epidermal cells after topical application of DMBA, demonstrating relevance of these findings in human tissue. This is the first report suggesting that carcinogens might trigger PXR in epidermal cells, particularly in LCs, thus leading to DNA damage. Further studies are required to better delineate the role of PXR in cutaneous carcinogenesis.

Isolation and evaluation of anticancer efficacy of stigmasterol in a mouse model of DMBA-induced skin carcinoma.

Stigmasterol (99.9% pure) was isolated from Azadirachta indica and its chemopreventive effect on 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin cancer was investigated in Swiss albino mice. Skin tumors were induced by topical application of DMBA and promoted by croton oil. To assess the chemopreventive potential of stigmasterol, it was orally administered at a concentration of 200 mg/kg and 400 mg/kg three times weekly for 16 weeks. Reduction in tumor size and cumulative number of papillomas were seen as a result of treatment with stigmasterol. The average latency period was significantly increased as compared with the carcinogen-treated control. Stigmasterol induced a significant decrease in the activity of serum enzymes, such as aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and bilirubin as compared with the control. Stigmasterol significantly increased glutathione, superoxide dismutase, and catalase as compared with the control. Elevated levels of lipid peroxide and DNA damage in the control group were significantly inhibited by administration of stigmasterol. From the present study, it can be inferred that stigmasterol has chemopreventive activity in an experimental model of cancer. This chemopreventive activity may be linked to the oxidative stress of stigmasterol. The antigenotoxic properties of stigmasterol are also likely to contribute to its chemopreventive action.

Immunoprevention of chemical carcinogenesis through early recognition of oncogene mutations.

Prevention of tumors induced by environmental carcinogens has not been achieved. Skin tumors produced by polyaromatic hydrocarbons, such as 7,12-dimethylbenz(a)anthracene (DMBA), often harbor an H-ras point mutation, suggesting that it is a poor target for early immunosurveillance. The application of pyrosequencing and allele-specific PCR techniques established that mutations in the genome and expression of the Mut H-ras gene could be detected as early as 1 d after DMBA application. Further, DMBA sensitization raised Mut H-ras epitope-specific CTLs capable of eliminating Mut H-ras(+) preneoplastic skin cells, demonstrating that immunosurveillance is normally induced but may be ineffective owing to insufficient effector pool size and/or immunosuppression. To test whether selective pre-expansion of CD8 T cells with specificity for the single Mut H-ras epitope was sufficient for tumor prevention, MHC class I epitope-focused lentivector-infected dendritic cell- and DNA-based vaccines were designed to bias toward CTL rather than regulatory T cell induction. Mut H-ras, but not wild-type H-ras, epitope-focused vaccination generated specific CTLs and inhibited DMBA-induced tumor initiation, growth, and progression in preventative and therapeutic settings. Transferred Mut H-ras-specific effectors induced rapid tumor regression, overcoming established tumor suppression in tumor-bearing mice. These studies support further evaluation of oncogenic mutations for their potential to act as early tumor-specific, immunogenic epitopes in expanding relevant immunosurveillance effectors to block tumor formation, rather than treating established tumors.

Modulating Effect of Enicostemma littorale on the Expression Pattern of Apoptotic, Cell Proliferative, Inflammatory and Angiogenic Markers During 7, 12-Dimethylbenz (a) Anthracene Induced Hamster Buccal Pouch Carcinogenesis.

Enicostemma littorale leaves are traditionally used for the treatment of several diseases, including inflammation and cancer. This study has taken effort to explore the antitumor initiating potential of E. littorale leaves (ElELet) by analyzing the expression pattern of apoptotic (p53, Bcl-2 and Bcl-2 associated X-protein), cell-proliferative (cyclin D1 and proliferating cell nuclear antigen), angiogenic (vascular endothelial growth factor), invasive (matrix metalloproteinase-2 and 9), and inflammatory (NF-κB and cyclooxygenase-2) markers during 7, 12-dimethylbenz (a) anthracene (DMBA) induced hamster buccal pouch carcinogenesis. Oral tumors were induced in the buccal pouches of hamsters using the potent site and organ specific carcinogen, DMBA. DMBA application 3 times a week for 14 weeks resulted in tumor formation in the buccal pouches. Hundred percent tumor formations with dysregulation in the expression pattern of apoptotic, cell proliferative, inflammatory, angiogenic, and invasive markers were observed in the buccal pouches of hamsters treated with DMBA alone. ElELet at a dose of 250 mg/kg body weight orally to DMBA treated hamsters significantly prevented the tumor formation as well as corrected the abnormalities in the expression pattern of above mentioned molecular markers. ElELet thus modulated the expression pattern of all the above mentioned molecular markers in favor of the suppression of cell proliferation occurring in DMBA induced hamster buccal pouch carcinogenesis.

Combinatorial chemopreventive effect of butyric acid, nicotinamide and calcium glucarate against the 7,12-dimethylbenz(a)anthracene induced mouse skin tumorigenesis attained by enhancing the induction of intrinsic apoptotic events

We explored the basis of the combinatorial chemopreventive effect of butyric acid (BA), nicotinamide (NA) and calcium glucarate (CAG) on mouse skin exposed to 7,12-dimethylbenz(a)anthracene (DMBA). We studied the effects of topical application of DMBA in the presence or absence of BA, NA and CAG on the regulators of apoptosis. DMBA treatment suppressed Bax, Bax/Bcl-2 ratio, release of cyt c, Apaf1, caspase-9, -3 mediated apoptosis. Downregulation of p21 and upregulation of Bcl-2, mut p53 were also observed in only DMBA treated mice. Simultaneous application of BA, NA and CAG induced a mitochondria-mediated apoptosis, characterized by a rise in the Bax, Bax/Bcl-2 ratio, release of cyt c, upregulation of Apaf1 with down-stream activation of caspase-9, -3. Furthermore treatment with BA, NA and CAG demonstrated an upregulation of p21 and downregulation of Bcl-2, mut p53. But this effect was enhanced in the presence of all the three compounds together in combination. Chemoprevention by a combination of BA, NA and CAG by inducing the apoptosis, the natural cell death, suggest the importance of the potential combinational strategies capable of preventing skin tumor development.

Deoxynivalenol induced mouse skin cell proliferation and inflammation via MAPK pathway

Several toxicological manifestations of deoxynivalenol (DON), a mycotoxin, are well documented; however, dermal toxicity is not yet explored. The effect of topical application of DON to mice was studied using markers of skin proliferation, inflammation and tumor promotion. Single topical application of DON (84–672nmol/mouse) significantly enhanced dermal hyperplasia and skin edema. DON (336 and 672nmol) caused significant enhancement in [3H]-thymidine uptake in DNA along with increased myeloperoxidase and ornithine decarboxylase activities, suggesting tissue inflammation and cell proliferation. Furthermore, DON (168nmol) caused enhanced expression of RAS, and phosphorylation of PI3K/Akt, ERK, JNK and p38 MAPKs. DON exposure also showed activation of transcription factors, c-fos, c-jun and NF-κB along with phosphorylation of IkBα. Enhanced phosphorylation of NF-κB by DON caused over expression of target proteins, COX-2, cyclin D1 and iNOS in skin. Though a single topical application of DMBA followed by twice weekly application of DON (84 and 168nmol) showed no tumorigenesis after 24weeks, however, histopathological studies suggested hyperplasia of the epidermis and hypertrophy of hair follicles. Interestingly, intestine was also found to be affected as enlarged Peyer's patches were observed, suggesting inflammatory effects which were supported by elevation of inflammatory cytokines after 24weeks of topical application of DON. These results suggest that DON induced cell proliferation in mouse skin is through the activation of MAPK signaling pathway involving transcription factors NFκB and AP-1, further leading to transcriptional activation of downstream target proteins c-fos, c-jun, cyclin D1, iNOS and COX-2 which might be responsible for its inflammatory potential.

Modulation of miR-203 and its regulators as a function of time during the development of 7, 12 dimethylbenz [a] anthracene induced mouse skin tumors in presence or absence of the antitumor agents

We investigated the chemopreventive effects of naturally occurring compounds like butyric acid (BA), nicotinamide (NA) and calcium glucarate (CAG) individually or in combination in 7, 12-dimethylbenz [a] anthracene (DMBA) treated mouse skin at 4 and 16weeks, the time before and after the tumor development. DMBA application did not show any skin tumors at 4weeks but well defined tumors appeared at 16weeks. BA, NA or CAG prevented the tumor development significantly but the protection was highly enhanced when all these compounds were given together. In order to see the molecular changes progressing with tumors, we showed the downregulation of tumor suppressor miR-203 at 16weeks and upregulation of histone deacetylases (HDAC), DNA methyltransferase, promoter methylation of miR-203 at 4 or 16weeks. Regulators of micro RNA biogenesis such as DICER1 and Ago2 were also deregulated by DMBA. Proto-oncogene c-myc and BMI1 were upregulated and tumor suppressor gene p16 was downregulated by DMBA as a function of time. Effects of BA, NA or CAG were more pronounced after 16weeks as compared to 4weeks in preventing the tumor development and altered gene expression. Concomitant administration of BA, NA and CAG tried to prevent these alterations more effectively than that of individual compound possibly by regulating miR-203 status through epigenetic or biogenetic modulations before and after the tumor development. Study provides a rationale for chemoprevention by combination of different compounds targeting miR-203.

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 16th 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.

Biochemical profiling and chemopreventive activity of phloretin on 7,12-Dimethylbenz (a) anthracene induced oral carcinogenesis in male golden Syrian hamsters.

Objectives:The present study was designed to examine the chemopreventive effects of phloretin against 7, 12-dimethylbenz (a) anthracene (DMBA) induced buccal pouch carcinogenesis in male golden Syrian hamsters in order to discover resources to improve the traditional medicine.Materials and Methods:Hamsters were divided into four groups of 10 animals each. Group I was served as an untreated control. Group II hamsters were painted with 0.5% DMBA in liquid paraffin on the left buccal pouches three times a week for 14 weeks. Group III hamsters were orally administrated with phloretin at a dose of 40 mg/kg body Weight (b.wt) on days alternate to DMBA application. Group IV hamsters were orally administrated with phloretin alone and served as the drug control. The experiment was terminated at the end of fourteenth week. The experimental animal's tumors were subjected into morphological examination and subsequently screened the pathological changes and estimate the activities of bi-products of lipid peroxidation, antioxidants enzymes and phase I and II detoxification enzyme status.Results:In DMBA alone treated hamster showed increased levels of lipid peroxidation by products, leads to decreased levels of enzymatic and non-enzymatic antioxidants status, activities of phase I and II detoxification enzyme status were altered. Normalized the neoplastic changes, decreased the levels of lipid by products, retain the antioxidants and restored the phase I and II enzymes were observed in phloretin administrated animals during DMBA induced oral carcinogenesis.Conclusion:Phloretin has possible chemopreventive role in which modulating the antioxidant and detoxification enzyme status, thereby retarding DMBA induced buccal pouch carcinogenesis.

Extraction optimization of Tinospora cordifolia and assessment of the anticancer activity of its alkaloid palmatine.

Objective. To optimize the conditions for the extraction of alkaloid palmatine from Tinospora cordifolia by using response surface methodology (RSM) and study its anticancerous property against 7,12-dimethylbenz(a)anthracene (DMBA) induced skin carcinogenesis in Swiss albino mice. Methods. The effect of three independent variables, namely, extraction temperature, time, and cycles was investigated by using central composite design. A single topical application of DMBA (100 μg/100 μL of acetone), followed 2 weeks later by repeated application of croton oil (1% in acetone three times a week) for 16 weeks, exhibited 100 percent tumor incidence (Group 2). Results. The highest yield of alkaloid from Tinospora cordifolia could be achieved at 16 hours of extraction time under 40°C with 4 extraction cycles. Alkaloid administration significantly decreases tumor size, number, and the activity of serum enzyme when compared with the control (Group 2). In addition, depleted levels of reduced glutathione (GSH), superoxide dismutase (SOD), and catalase and increased DNA damage were restored in palmatine treated groups. Conclusion. The data of the present study clearly indicate the anticancer potential of palmatine alkaloid in DMBA induced skin cancer model in mice.

Chemomodulatory Effect of Trigonella foenum graecum (L.) Seed Extract on Two Stage Mouse Skin Carcinogenesis.

Cancer is not a single disease but a group of complex genetic diseases of aged cells. Chemoprevention of cancer is the attempt to use natural and synthetic compounds to intervene in the early stages of cancer, before invasive disease begins. Consuming a diet rich in plant foods can provide a milieu of phytochemicals and non-nutritive plant substances that possess health-protective effects. Some phytochemicals derived in spices and herbs as well as other plants possess substantial cancer preventive properties. Thus the cancer chemo preventive potential of naturally occurring phytochemicals is of great interest because of their preventive role and as they are not perceived as “medicine”. During the course of present study Trigonella foenum graecum (L.) seed- TFGS (commonly called fenugreek) extract was given at pre-initiational, post-initiational, promotional and throughout the experiment along with 7,12-dimethylbenz [a] anthracene DMBA and 12-O-tetradecanoylphorbol-13-acetate TPA treatment in Swiss albino mice. A significant reduction of papillomas in DMBA + TPA + TFGS (400 mg/kg. body wt.) treated group was found to be effective in decreasing the rate of tumor incidence in comparison to control. Furthermore, cumulative number of papillomas, tumor yield and tumor burden were also found to be reduced. The TFGS extract treatment before DMBA and TPA application (i.e. Pre initiation) were more effective than that of treatment during, and /or after DMBA treatment, however TFGS extract treatment was most effective when treated throughout all the stages of tumorigenesis. The TFGS treatment also showed a modulatory influence on mouse hepatic antioxidant defense system (GSH and LPO level).

Protective effect of 18β-glycyrrhetinic acid on cell surface glycoconjugates abnormalities in 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch carcinogenesis

Aim: The aim of this study was to evaluate the protective effect of 18β-glycyrrhetinic acid against cell surface glycoconjugates (protein-bound hexose, hexosamine, sialic acid, and fucose) abnormalities in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Materials and Methods: Topical application of DMBA three times a week for 14 weeks on the buccal pouches of hamsters resulted in well-developed squamous cell carcinoma. Glycoconjugates status in plasma and tumor tissues were estimated using specific and sensitive colorimetric methods. Results: Increases in plasma and tumor tissue glycoconjugates were noticed in hamsters treated with DMBA. Oral administration of glycyrrhetinic acid at a dose of 45 mg/kg body weight restored the status of glycoconjugates in hamsters treated with DMBA. Conclusion: The results of this study suggest that glycyrrhetinic acid might provide protection against cell surface abnormalities during DMBA-induced buccal pouch carcinogenesis in hamsters.

Inhibitory effect of vitamin D-binding protein-derived macrophage activating factor on DMBA-induced hamster cheek pouch carcinogenesis and its derived carcinoma cell line.

This study investigated the inhibitory effect of vitamin D-binding protein-derived macrophage-activating factor (GcMAF) on carcinogenesis and tumor growth, using a 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced hamster cheek pouch carcinogenesis model, as well as the cytocidal effect of activated macrophages against HCPC-1, a cell line established from DMBA-induced cheek pouch carcinoma. DMBA application induced squamous cell carcinoma in all 15 hamsters of the control group at approximately 10 weeks, and all 15 hamsters died of tumor burden within 20 weeks. By contrast, 2 out of the 14 hamsters with GcMAF administration did not develop tumors and the remaining 12 hamsters showed a significant delay of tumor development for approximately 3.5 weeks. The growth of tumors formed was significantly suppressed and none of the hamsters died within the 20 weeks during which they were observed. When GcMAF administration was stopped at the 13th week of the experiment in 4 out of the 14 hamsters in the GcMAF-treated group, tumor growth was promoted, but none of the mice died within the 20-week period. On the other hand, when GcMAF administration was commenced after the 13th week in 5 out of the 15 hamsters in the control group, tumor growth was slightly suppressed and all 15 hamsters died of tumor burden. However, the mean survival time was significantly extended. GcMAF treatment activated peritoneal macrophages in vitro and in vivo, and these activated macrophages exhibited a marked cytocidal effect on HCPC-1 cells. Furthermore, the cytocidal effect of activated macrophages was enhanced by the addition of tumor-bearing hamster serum. These findings indicated that GcMAF possesses an inhibitory effect on tumor development and growth in a DMBA-induced hamster cheek pouch carcinogenesis model.

Protective role of cathepsin L in mouse skin carcinogenesis

Lysosomal cysteine protease cathepsin L (CTSL) is believed to play a role in tumor progression and is considered a marker for clinically invasive tumors. Studies from our laboratory using the classical mouse skin carcinogenesis model, with 7,12-dimethyl-benz[a]anthracene (DMBA) for initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA) for promotion, showed that expression of CTSL is increased in papillomas and squamous cell carcinomas (SCC). We also carried out carcinogenesis studies using Ctsl-deficient nackt (nkt) mutant mice on three different inbred backgrounds. Unexpectedly, the multiplicity of papillomas was significantly higher in Ctsl-deficient than in wild-type mice on two unrelated backgrounds. Topical applications of TPA or DMBA alone to the skin of nkt/nkt mice did not induce papillomas, and there was no increase in spontaneous tumors in nkt/nkt mice on any of the three inbred backgrounds. Reduced epidermal cell proliferation in Ctsl-deficient nkt/nkt mice after TPA treatment suggested that they are not more sensitive than wild-type mice to TPA promotion. We also showed that deficiency of CTSL delays terminal differentiation of keratinocytes, and we propose that decreased elimination of initiated cells is at least partially responsible for the increased papilloma formation in the nackt model.

Azadirachta indica Exerts Chemopreventive Action Against Murine Skin Cancer: Studies on Histopathological, Ultrastructural Changes and Modulation of NF-κB, AP-1, and STAT1

The present study reports the histopathological, ultrastructural changes and modulation of NF-kappaB, AP-1, and STAT 1 during skin carcinogenesis in LACA mice and its intervention with Azadirachta indica. Skin tumors were induced by topical application of 7,12-dimethylbenz(a)anthracene (DMBA) (500 nmol/100 microl for 2 weeks) followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) (1.7 nmol/100 microl of acetone, twice weekly) as a promoter. Male LACA mice were divided into four groups: Control, DMBA/TPA, aqueous Azadirachta indica leaf extract (AAILE), and AAILE + DMBA/TPA. AAILE was administered orally at a dose level of 300 mg/kg body weight three times a week for 20 weeks. Topical application of DMBA/ TPA to the skin resulted in well-developed squamous cell carcinomas characterized by hyperproliferation, hyperkeratosis, and corrugation of the epidermis. Degenerative changes were observed in the tumors of AAILE + DMBA/TPA-treated animals. Scanning electron microscopy revealed surface disruptions and certain rounded structures on the skin tumors of DMBA/TPA-treated animals. Topographical changes were also observed in the tumors of AAILE + DMBA/TPA-treated animals, which resembled regions of degeneration. Tumors obtained in DMBA/TPA group were associated with enhanced expression of NF-kappaB and AP-1 when compared to the control counterparts. Inhibition in tumorigenesis in response to A. indica treatment was accompanied by an overexpression of STAT 1 and AP-1 and decrease in NF-kappaB expression. The results of the present study provide a basis for the chemopreventive potential of A. indica against murine skin carcinogenesis.