Research in the Cancer Prevention Basic Research Project is primarily focused on the anticarcinogenic properties of a wide variety of natural and synthetic substances. Elucidation of environmental as well as endogenous factors involved in human cancer development is also a major objective. It is hoped that the results obtained will facilitate the development of preventive measures against human cancers.

Mutagenic/carcinogenic aminophenylnorharman (APNH) is formed from norharman and aniline in the presence of CYP3A4/1A2. Because both precursors are widely distributed in the environment, human exposure is unavoidable. To clarify APNH formation in the human body, amounts of this compound in 24-h urine samples collected from healthy volunteers and inpatients were analyzed by LC-ESI/MS. APNH could be detected in all urine samples at levels of 21 to 594 pg for healthy volunteers and 12 to 338 pg for inpatients in 24-h urine samples. Similar to APNH, all urine samples contained norharman and aniline at levels of 46 to 447 ng and 0.49 to 8.12 mg for healthy volunteers and 6 to 75 ng and 0.33 to 1.86 mg for inpatients, respectively. These results suggest that APNH should be considered as a novel endogenous mutagen/carcinogen ⁽¹³⁰⁾. In addition, an APNH-RNA adduct was yielded by reaction between the ultimate mutagenic form of APNH, N-acetoxy-APNH, and guanosine (Guo). The chemical structure was concluded to be Guo-C8-APNH, as in the case of the APNH-DNA adduct. When APNH was administered to rats, formation of APNH-RNA adducts was observed in the liver, at six times higher levels than APNH-DNA ⁽¹³¹⁾. A report related to the cancer-initiating activity of APNH in inflamed mouse colon can be found in the attached list of references ⁽¹³²⁾.

4-Amino-3,3'-dichloro-5,4'-dinitrobiphenyl (ADDB) is a novel chemical exerting strong mutagenicity in the absence of S9 mix. To conduct a comprehensive survey of the levels of ADDB and suspected starting materials or intermediates of ADDB, water samples were collected from the Waka River, and ADDB-related chemicals, including 3,3'-dichlorobenzidine (DCB), were analyzed by HPLC. ADDB (12.0 ng/L-equivalent) and DCB (and 20,400 ng/L-equivalent) were detected in the samples collected at the site where wastewater was discharged from chemical plants into the river. This suggests that ADDB is formed during the process of wastewater treatment of drainage water containing DCB from chemical plants ⁽¹³³⁾.

Reports related to other environmental mutagens/carcinogens can be found in the attached list of references ^(134-136).

Expression of inducible nitric oxide (iNOS) and cyclooxygenase (COX)-2 is known to be elevated in colon cancers, in both humans and experimental animals. Bowel inflammation induced by dextran sodium sulfate (DSS) enhances colon tumor development in Min mice. Increased expression of COX-2 and iNOS was observed in the tumors. Colon tumor development in Min mice treated with DSS was suppressed by an iNOS inhibitor, ONO-1714 ⁽¹³⁷⁾.

Epidemiologically, consumption of a high-fat diet and high serum levels of triglycerides (TG) and cholesterol are suggested to be associated with the risk of colon cancer. Interestingly, Apc- deficient Min mice show an age-dependent hyperlipidemic state along with downregulation of the mRNA expression of lipoprotein lipase (LPL), which catalyzes the hydrolysis of TG. The cyclooxygenase inhibitor, indomethacin, is known to suppress intestinal polyp development in Min mice. Treatment with indomethacin reduced the serum TG levels in a dose-dependent manner, along with induction of LPL and modification of expression of sterol regulatory element binding protein(SREBP)-1c-regulated genes ⁽¹³⁸⁾. These results indicate that indomethacin might suppress intestinal tumor formation and also the hyperlipidemic state by regulating LPL and other lipid-metabolic factors.

It has been reported that fat intake and obesity are positively correlated with pancreatic cancer in humans. A pancreatic carcinogen, N-nitrosobis (2-oxopropyl)amine (BOP), induces pancreatic ductal adenocarcinomas limited to Syrian golden hamsters, other rodents not being susceptible. The hyperlipidemic state in hamsters was improved by administration of the PPARg agonist, pioglitazone, accompanied by suppression of the development of invasive pancreatic adenocarcinomas ⁽¹³⁹⁾. Thus, hyperlipidemia could enhance the risk of development of pancreatic cancer in hamsters.

The effects of diabetes/hyperlipidemia on BOP-induced cancer development were examined in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, model animals for non-insulin-dependent diabetes mellitus, and Long-Evans Tokushima Otsuka (LETO) rats, the corresponding controls. The highest yields were noted for thyroid tumors, the incidence and multiplicity of BOP-induced thyroid cancers with marked fibrosis being significantly higher in the OLETF than in the LETO rats ⁽¹⁴⁰⁾, indicating that a diabetic/hyperlipidemic state can enhance carcinogenesis of the thyroid gland.

Reports related to cancer promotion and prevention can be found in the attached list of publications ^(141-144).

Crude extracts of the cabbage white butterfly, Pieris rapae, have the ability to induce apoptosis in human cancer cell lines. As an apoptosis- inducing protein, pierisin-1 has been isolated from P. rapae and shown to exhibit DNA ADP- ribosylating activity. Persistence of the pierisin-1 activities in adult P. rapae after killing was estimated by analyzing the cytotoxicity against HeLa cells and DNA ADP-ribosylation ability. During storage for 8 weeks, the cytotoxicity decreased to 22%, and the DNA ADP- ribosylating activity also decreased to 23% ⁽¹⁴⁵⁾. These results suggest that cytotoxic and DNA ADP-ribosylating activities persist to some extent in the body after death.

Reports related to DNA ADP-ribosylation can be found in the attached list of publications ^{(146, 147)}.