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Pancreatic ductal adenocarcinoma (PDAC) is one of the most debilitating malignancies in humans, and one of the reasons for this is the inability to diagnose this disease early in its development. To search for biomarkers that can be used for early diagnosis of PDAC, we established a rat model of human PDAC in which expression of a human K-ras(G12V) oncogene and induction of PDAC are regulated by the Cre/lox system. In the present study, transgenic rats bearing PDAC and control transgenic rats with normal pancreatic tissues were used for metabolomic analysis of serum and pancreatic tissue by non-targeted and targeted gas chromatography-mass spectrometry and transcriptomic analysis of pancreatic tissue by microarray. Comparison of the metabolic profiles of the serum and pancreatic tissue of PDAC-bearing and control rats identified palmitoleic acid as a metabolite, which was significantly decreased in the serum of PDAC-bearing animals. Transcriptomic analysis indicated that several transcripts involved in anaerobic glycolysis and nucleotide degradation were increased and transcripts involved in the trichloroacetic acid cycle were decreased. Other transcripts that were changed in PDAC-bearing rats were adenosine triphosphate citrate lyase (decreased: fatty acid biosynthesis), fatty acid synthase (increased: fatty acid biosynthesis) and arachidonate 5-lipoxygenase activating protein (increased: arachidonic acid metabolism). Overall, our results suggest that the decreased serum levels of palmitoleic acid in rats with PDAC was likely due to its decrease in pancreatic tissue and that palmitoleic acid should be investigated in human samples to assess its diagnostic significance as a serum biomarker for human PDAC.

Oral squamous cell carcinoma is one of the most common human neoplasms, and prevention of this malignancy requires a better understanding of its carcinogenesis process. To this end, we tried to establish an animal model using the human c-Ha-ras proto-oncogene-carrying transgenic (Tg) rats and the carcinogen 4-nitroquinoline 1-oxide (4-NQO). 4-NQO (20 p.p.m.) was administered to Tg and non-Tg rats for 8 weeks in their drinking water, and then the occurrence of tongue carcinogenesis was compared during the experimental period of 22 weeks. In addition, we determined the DNA ploidy in tongue lesions and examined the immunohistochemical expression of five biomarkers such as cyclin D1, glutathione S-transferase placental form, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) and beta-catenin. Next, the cancer chemopreventive effects of nimesulide, pioglitazone and a synthetic geranylated derivative, which have been reported to be inhibitors of tongue carcinogenesis, were examined in Tg rats treated with 4-NQO. Either during or after treatment with 4-NQO in the drinking water, tongue dysplasia and tumors were observed on the tongues of both Tg and non-Tg rats, with a greater incidence and multiplicity in Tg rats. Histopathologically, squamous cell dysplasia, papilloma and carcinoma with or without invasion were present in the tongue. Immunohistochemistry revealed that expression levels against five biomarkers increase with disease progression, and the changes correlated with those of the DNA ploidy pattern. Interestingly, a strong expression of COX-2, iNOS and beta-catenin was observed on the invasive front of squamous cell carcinomas. A subsequent chemoprevention study using Tg rats showed that the chemicals tested suppressed the occurrence of tongue carcinomas when they were administered after 4-NQO-exposure. These results may thus indicate that our 4-NQO-induced Tg rat tongue carcinogenesis model simulates many aspects of human oral carcinogenesis and it can be applied for an analysis of oral cancer development while also helping to identify potentially effective cancer chemopreventive agents against oral cancer.

The present study was designed to investigate the modifying effects of dietary 5-hydroxy-4-(2-phenyl-(E)-ethenyl)-2(5H)-furanone (KYN-54), a new synthetic retinoidal butenolide, during the post-initiation phase on azoxymethane (AOM)-induced rat intestinal carcinogenesis. The number of aberrant crypt foci (ACF) in rat colon, colonic ornithine decarboxylase (ODC) activity and bromodeoxy-uridine (BrdUrd) labeling index in rat colonic epithelium were also assessed. At 7 weeks of age, male F344 rats (except the KYN-54 alone and control groups) were given weekly s.c. injections of AOM at 15 mg/kg body wt for 3 weeks. Starting 1 week after the last injection of AOM, rats (except the control group) were fed a diet containing KYN-54 at concentrations of 100 or 200 p.p.m. throughout the experiment. All animals were necropsied at 32 weeks after the start of the experiment. Compared with the AOM alone group, KYN-54 at both doses reduced the incidence and multiplicity of tumors in entire intestine (small and large intestines). In the 200 p.p.m. KYN-54 fed group especially, tumor incidence and multiplicity in the entire intestine were lower compared with the AOM alone group (P < 0.005 and P < 0.05 respectively). Also, the number of ACF/cm2 colon in the groups of rats treated with AOM and KYN-54 at both doses were significantly lower than that of rats treated with AOM alone (P < 0.05). Colonic ODC activity and BrdUrd labeling index in the groups of rats treated with AOM and KYN-54 at both doses were slightly lower than those treated with AOM alone. KYN-54 at 200 p.p.m. significantly lowered BrdUrd labeling index induced by AOM (P < 0.005). These results suggest that KYN-54 might be a promising chemopreventive agent for intestinal neoplasia.

The modifying effects of dietary administration of the plant phenolic antioxidants caffeic acid (CA), ellagic acid (EA), chlorogenic acid (CGA) and ferulic acid (FA) during the initiation phase on 4-nitroquinoline-1-oxide (4-NQO)-induced tongue carcinogenesis and on the number and area of silver-stained nucleolar organizer region proteins (AgNORs), a new cell proliferation marker, of the tongue squamous epithelium were investigated in male F344 rats. Rats were fed the diet containing 500 p.p.m. CA, 400 p.p.m. EA, 250 p.p.m. CGA or 500 p.p.m. FA for 7 weeks. One week after the commencement of the diets, 4-NQO (20 p.p.m.) was administered in the drinking water for 5 weeks. Feeding of four phenolic compounds significantly reduced the incidences of tongue neoplasms (squamous cell papilloma and carcinoma) and preneoplastic lesions (hyperplasia and dysplasia) by 32 weeks, and rats fed CA or EA had no tongue neoplasms. The number and area of AgNORs per nucleus were decreased significantly by dietary treatment with these four phenolics. Thus, CA, EA, CGA and FA inhibited the tongue carcinogenesis induced by 4-NQO when they were administered concurrently with the carcinogen. These results might suggest possible application of these natural substances for cancer chemoprevention in tongue in addition to other tissues (skin, lung, liver and esophagus).

The chemopreventive effects of two xanthophylls, astaxanthin (AX) and canthaxanthin (CX), on urinary bladder carcinogenesis induced by N-butyl-N(4-hydroxybutyl)nitrosamine (OH-BBN) was investigated in male ICR mice. Mice were given 250 p.p.m. OH-BBN in drinking water for 20 weeks and after a 1 week interval with tap water, water containing AX or CX at a concentration of 50 p.p.m. was administered during subsequent 20 weeks. Other groups of mice were treated with AX or CX alone or untreated. At the end of the study (week 41), the incidences of preneoplastic lesions and neoplasms in the bladder of mice treated with OH-BBN and AX or CX were smaller than those of mice given OH-BBN. In particular, AX administration after OH-BBN exposure significantly reduced the incidence of bladder cancer (transitional cell carcinoma) (P < 0.003). However, the inhibition of the frequencies of such lesions in mice treated with OH-BBN and CX was not significant. Treatment with AX or CX also decreased the number/nucleus of silver-stained nucleolar organizer region proteins (AgNORs), a new index of cell proliferation, in the transitional epithelium exposed to OH-BBN. Preneoplasms and neoplasms induced by OH-BBN, and the antiproliferative potential, was greater for AX than CX. These results indicate that AX is a possible chemopreventive agent for bladder carcinogenesis and such an effect of AX may be partly due to suppression of cell proliferation.