The mRNA expression of placental glutathione S-transferase isoenzyme in hamster buccal-pouch carcinomas using reverse transcription-polymerase chain reaction

Is placental glutathione S-Transferase (GST-P) a suitable biomarker for oral carcinogenesis: A scoping review

Placental Glutathione S-Transferase (GST-P) can be considered a useful marker of not only of preneoplastic lesion in rat hepatocarcinogenesis and hamster pancreatic carcinogen but also as a potential marker for premalignant and malignant lesions in cases of buccal pouch mucosa. In this context, the aim of this review is to elucidate the following question whether the GST-P is a suitable biomarker for oral carcinogenesis. A total of 16 studies were carefully selected. Our results demonstrate that GST-P expression is a useful and coherent marker for oral carcinogenesis. Regarding the samples, most studies evaluated hamsters, two evaluated GST-P expression in rats and three evaluated GST-P expression in human cells. All studies demonstrated positive findings allowing us to consider such studies reliable. In summary, our conclusion is that GST-P can be a suitable biomarker for oral carcinogenesis.

DMBA-induced hamster buccal pouch carcinoma and VX2-induced rabbit cancer as a model for human oral carcinogenesis

In this article, we have described and compared the advantages and disadvantages of two potential animal cancer models (the hamster buccal pouch cancer model and the VX2-induced rabbit cancer model) for human squamous cell carcinomas of the oral mucosa. Currently, no animal cancer model is perfectly applicable to human oral squamous cell carcinomas. This is because the hamster buccal pouch cancer model has a different etiology and genetic constitution compared with human oral carcinomas. In addition, the VX2-induced rabbit cancer model is not produced in situ and, consequently, its natural behavior is totally reliant on the location of transplantation. Nonetheless, with the use of these two animal cancer models together, researchers could evaluate different aspects of the cellular and molecular biological characteristics or assess potential novel treatment regimens for squamous cell carcinomas of the human oral mucosa.

Evaluation of Azadirachta indica leaf fractions for in vitro antioxidant potential and in vivo modulation of biomarkers of chemoprevention in the hamster buccal pouch carcinogenesis model

We evaluated the chemopreventive potential of Azadirachta indica (neem) leaf fractions based on in vitro antioxidant assays, and in vivo inhibitory effects on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. In addition we also identified the major constituents in neem leaf fractions by HPLC. Analysis of the free radical scavenging activities and reducing potential of crude ethanolic extract (CEE), ethyl acetate fraction (EAF) and methanolic fraction (MF) of neem leaf revealed a concentration-dependent increase in antioxidant potential that was in the order EAF>MF>CEE. Administration of neem leaf fractions reduced the incidence of DMBA-induced HBP carcinomas at a lower concentration compared to the crude extract. Chemoprevention by neem leaf fractions was associated with modulation of phase I and phase II xenobiotic-metabolising enzymes, lipid and protein oxidation, upregulation of antioxidant defences, inhibition of cell proliferation and angiogenesis, and induction of apoptosis. However, EAF was more effective than MF in terms of antiproliferative and antiangiogenic effects, and expression of CYP isoforms. The greater efficacy of EAF may be due to higher content of constituent phytochemicals as revealed by HPLC analysis. The results of the present study suggest that the antioxidant properties of neem leaf fractions may be responsible for modulating key hallmark capabilities of cancer cells such as cell proliferation, angiogenesis and apoptosis in the HBP carcinogenesis model.

Expression of placental glutathione S-transferase in rat tongue mucosa exposed to cigarette smoke

Glutatione S-transferases (GSTs) are a family of enzymes involved in detoxification of xenobiotics. Placental GST, known as GST-P, has been detected in tissues following exposure to carcinogenic agents being regarded a reliable biomarker of exposure and susceptibility in early phases of carcinogenesis. The aim of this study was to investigate the expressivity of GST-P positive foci in the rat tongue mucosa exposed to cigarette smoke by means of immunohistochemistry. A total of twelve male Wistar rats were distributed into two groups: negative control and experimental group exposed to cigarette smoke during 75 days. After experimental period, no histopathological changes in the tongue mucosa were evidenced in the negative control and the experimental group. However, a total of five GST-P positive foci were detected in two out of six animals exposed to cigarrette smoke. None control animals were noticed GST-P positive foci. These data indicate that expression of GST-P may reflect the carcinogenic effect of cigarette smoke as well as the genetic susceptibility of animals in relation to continuous carcinogens exposure.

Comparative evaluation of antiproliferative, antiangiogenic and apoptosis inducing potential of black tea polyphenols in the hamster buccal pouch carcinogenesis model

BACKGROUND

To evaluate the relative chemopreventive efficacy of two black tea polyphenols, Polyphenon-B [P-B] and BTF-35 on 7,12-dimethylbenz [a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis.

METHODS

Hamsters were divided into 6 groups. The right buccal pouches of animals in groups 1-3 were painted with 0.5% of DMBA three times a week for 14 weeks. While hamsters in group 1 received no further treatment, animals in groups 2 and 3 received diet containing 0.05% P-B and BTF-35 respectively, four weeks before DMBA painting that was continued until the end of the experiments. Animals in groups 4 and 5 were given P-B and BTF-35 alone respectively as in groups 2 and 3. Group 6 animals served as the untreated control. All the animals were sacrificed after 18 weeks. The expression of p21, cyclin D1, glutathione S-transferase pi (GST-P), nuclear factor kappa B (NF-kappaB), Bcl-2, Bax, cytochrome C, caspase-3, caspase-9, poly(ADP-ribose) polymerase (PARP), cytokeratins and vascular endothelial growth factor (VEGF) was analysed by RT-PCR, immunohistochemical and Western blot analyses.

RESULTS

DMBA treated animals developed buccal pouch carcinomas that displayed increased expression of p21, cyclin D1, GST-P, NF-kappaB, cytokeratins, VEGF and Bcl-2 with decreased expression of Bax, cytochrome C, caspase-3, caspase-9, and PARP. Dietary administration of both P-B and BTF-35 reduced the incidence of DMBA-induced HBP carcinomas by modulating markers of cell proliferation, cell survival, tumour infiltration, angiogenesis, and apoptosis.

CONCLUSION

The results of the present study provide a mechanistic basis for the chemopreventive potential of black tea polyphenols. The greater efficacy of BTF-35 in inhibiting HBP carcinogenesis and modulating multiple molecular targets may have a potential role in the prevention of oral cancer.

Placental glutathione S-transferase correlates with cellular proliferation during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide

Taking into consideration that glutatione S-transferase (GST) and cellular proliferation play a crucial role during carcinogenesis, the goal of this study was to investigate the expression of placental GST, called GST-P, and proliferating cellular nuclear antigen (PCNA) by means of immunohistochemistry during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide (4NQO). This is a useful model for studying oral squamous cell carcinoma phase by phase. Male Wistar rats were distributed into three groups of 10 animals each and treated with 50 ppm 4NQO solution by drinking water for 4, 12 or 20 weeks. Ten animals were used as negative control. GST-P positive foci were detected in non-neoplastic oral cells at 4 weeks of 4NQO administration. In the same way, GST-P positive cells were detected in pre-neoplastic lesions and squamous cell carcinomas induced after 12 and 20 weeks-treatment, respectively. None of the control animals expressed GST-P positive cells. Regarding cellular proliferation, PCNA positive nuclei were higher at 12 and 20 weeks following 4NQO exposure (p<0.05) when compared to negative control. These results suggest that the expression of GST-P is correlated with cellular proliferation, in which GST-P is associated with risk and progression of oral cancer, whereas PCNA is closely involved during neoplastic conversion.

Reducing the expression of glutathione transferase D mRNA in Drosophila melanogaster exposed to phenol and aniline

Phenol and aniline are toxic to animals. The purpose of the present study was to examine the expression of glutathione transferase D mRNA in fruit flies altered by long-term exposure to phenol and aniline. Changes in the amount of mRNA were measured by a semiquantitative reverse-transcription polymerase chain reaction assay. The level of each glutathione transferase D mRNA expressed in the phenol-treated and aniline-treated strains of adult fruit flies differed after chemical treatment. Aniline was more potent than phenol in suppressing the expression of cytosolic glutathione transferase D mRNA. Aniline reduced the level of glutathione transferase mRNA expressed in the aniline-treated strain to less than a 0.5 fraction as compared to that measured in the wild-type strain. But phenol was only able to suppress the GstD7 and GstD4 mRNAs expressed in the phenol-treated strain. Neither aniline nor phenol reduced the expression of microsomal glutathione transferase mRNA in fruit flies.

Combinatorial antigenotoxic and anticarcinogenic effects of tomato and garlic through modulation of xenobiotic-metabolizing enzymes during hamster buccal pouch carcinogenesis

OBJECTIVE

Combination chemoprevention by dietary agents is a promising approach toward cancer control. Many dietary agents are known to prevent experimental mutagenesis and carcinogenesis by modulating xenobiotic-metabolizing enzymes. The present study evaluated the combinatorial chemopreventive effects of tomato and garlic on hamster buccal pouch carcinogenesis induced by 7,12-dimethylbenz[a]anthracene (DMBA).

METHODS

Hamsters were assigned to one of four groups. The right buccal pouches of animals in group 1 were painted with 0.5% DMBA three times a week. The right buccal pouches of animals in group 2 were painted with DMBA and received intragastric administration of a combined dose of tomato and garlic on days alternate to DMBA application. Animals in group 3 were given chemopreventive agents alone. Animals in group 4 served as controls. Levels of phase I and II enzymes and the frequency of bone marrow micronuclei were used as biomarkers of chemoprevention.

RESULTS

All the hamsters painted with DMBA alone developed buccal pouch carcinomas that exhibited increased activities of xenobiotic-metabolizing enzymes associated with increased frequencies of bone marrow micronuclei. In the liver, an increase in phase I enzymes was accompanied by compromised phase II detoxification activities. Combined administration of tomato and garlic effectively suppressed the incidence and mean tumor burden of hamster buccal pouch carcinomas. In addition, tomato and garlic combination significantly decreased phase I enzymes and increased phase II enzyme activities in the pouch and liver with a decreased incidence of bone marrow micronuclei.

CONCLUSION

From these results, we suggest that modulation of xenobiotic-metabolizing enzymes exerted by tomato and garlic combination plays a key role in mitigating the mutagenic and carcinogenic effects of DMBA.

Correlation between inducible nitric oxide synthase and p53 expression for DMBA-induced hamster buccal-pouch carcinomas

Three isoforms of nitric oxide synthase (NOS) have been identified previously--endothelial NOS, neuronal NOS, and inducible NOS (iNOS). It has been reported previously that there may be a negative feedback loop existing between nitric oxide (NO) production and wild-type p53 tumor-suppressor gene, but the relationship has not previously been studied for oral experimental carcinogenesis. The purpose of the present study is to assess whether iNOS expression correlates with p53 expression at both protein and mRNA levels for 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal-pouch carcinomas.

MATERIALS AND METHODS

Thirty-five out-bred, young (6 week old), male, Syrian golden hamsters (Mesocricatus auratus) were randomly divided into one experimental group (15 animals), and two control groups (10 animals each). Bilaterally, the pouches of a group of 15 animals from the experimental group were painted with a 0.5% DMBA solution three times a week for 12 weeks whilst each animal from one of the control groups was similarly treated with only mineral oil. Another control group of 10 animals remained untreated throughout the experimental procedure. Specimens obtained from the hamster buccal-pouch mucosa were evaluated using immunohistochemical assessment of iNOS and p53 protein and in situ reverse transcription-polymerase chain reaction (IS RT-PCR), as well as reverse transcription-polymerase chain reaction (RT-PCR) for iNOS and p53 mRNA.

RESULTS

Two of the 15 animals of the DMBA-treated group died during the experiment. Squamous-cell carcinomas with a 100% tumor incidence were apparent for all of the 15-week DMBA pouch-treated animals. Animals from the mineral oil-treated and untreated pouch groups revealed no obvious changes. Inducible NOS mRNA was identified as a band corresponding to a 499-bp PCR product and was observed for all 13 of the hamster buccal-pouch tissue specimens treated with DMBA for 15 weeks. The p53 mRNA was found as a band corresponding to a 370-bp polymerase chain reaction (PCR) product and was noted for nine (9/13, 69%) of the 15-week DMBA-treated pouches. No such bands (iNOS and p53) were noted for the untreated animals, the mineral oil-treated tissues and the negative-control samples. Using IS RT-PCR, the proportional (percentage) expression of iNOS (13/13, 100%) and p53 (8/13, 62%) mRNA observed for the hamster buccal-pouch tissue specimens treated with DMBA for 15 weeks was noted to be consistent with the findings using RT-PCR. Furthermore, the proportional expression of iNOS (13/13, 100%) and p53 (8/13, 62%) proteins for the 15-week DMBA-treated hamster buccal-pouch tissue specimens was noted to be consistent with the findings using RT-PCR and IS RT-PCR. A significant association between iNOS and p53 expression (at both protein and mRNA levels) was noted (Fisher's exact probability test, P < 0.05). Neither iNOS nor p53 activity (at both protein and mRNA levels) was found for any of the untreated and mineral oil-treated pouches.

CONCLUSIONS

Enhanced expression of iNOS and p53 at both protein and mRNA levels in DMBA-induced hamster buccal-pouch carcinomas compared with the untreated and mineral oil-treated counterparts, has been demonstrated in the current study. Furthermore, we report what is, to the best of our knowledge, the first identification of a significant association between iNOS and p53 expression (at both protein and mRNA levels) in this experimental model system for oral carcinogenesis, although their precise interactions remain to be clarified.