Cancer Prevention Division

11. Cancer Prevention Division

Research in the Cancer Prevention Division is primarily focused on the anticarcinogenic properties of a wide variety of natural and synthetic substances. Elucidation of environmental as well as en dogenous factors involved in human cancer development, is also a main objective. The results obtained are anticipated to facilitate the development of preventive measures against human cancers.
Mutagens in Water from the Nishitakase River

Water samples from the Nishitakase river in Kyoto, especially taken at sites below sewage plants, show significantly high mutagenicity. Among five mutagenic compounds detected, the structure of a compound was determined to be 2-[2-(acetylamino)-4-[bis(2-methoxyethyl) amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole(PBTA-1).⁽¹⁵⁹⁾ PBTA-1 is a newly identified mutagen, inducing 3,000,000 revertants of S. typhimurium YG1024 per mg with S9 mix. PBTA-1 is suggested to be derived from an azo dye which is an industrial material.
Comutagenic Action of Norharman

Norharman, found widely in our environment, is not mutagenic to S.typhimurium strains, but it becomes mu tagen ic to TA98 and YG1024 in the presence of non-mu tagenic aniline with S9 mix.⁽¹⁶⁰⁾ Two mutagenic compounds were isolated from a reaction mixture between norharman and aniline with S9 mix, and their structures were determined to be a coupled compound of norharman and aniline, 9-(4'-aminophenyl)-9H-pyrido[3,4-b]indole, and its hydroxyamino derivative. Thus, the appearance of mutagenicity by norharman with aniline in the pres ence of S9 mix was suggested to be as follows. First the cou pled mutagenic compound is formed by an enzymatic reaction be tween norharman and aniline. Then, the amino group is converted to ahydroxyamino group and further activated by forming esters. These ultimate forms react with DNA bases to induce mutations in TA98 and YG1024.
Suppression of Intestinal Polyp Development by a Selective Inhibitor of Cyclooxygenase-2 (COX-2), Nimesulide

NSAIDs have been shown to sup press development of colon tumors, but gastrointestinal side effects caused by the inhibition of COX-1 activity are recognized as a serious problem for clinical application. Therefore, the effect of nimesulide, a selective in hibitor of COX-2, on the development of intestinal polyps in Min mice, which have a mutation in Apc gene, was in vestigated. Female Min mice at 4 weeks old were given 400 ppm nimesulide in a diet for 11 weeks. This treatment decreased the number of intestinal polyps to 52% of the control value, and also re duced the size of the polyps.⁽¹⁶¹⁾ The results suggest that nimesulide is a good candidate chemopreventive agent for human colon cancer with fewer gastrointestinal side effects.
Increased Expression of Inducible Nitric Oxide Synthase (iNOS) in Colon Carcinomas

Excessive nitric oxide (NO) production is recognized as a causative factor in cancer development. In order to elucidate the involvement of NO in colon carcinogenesis, the expression level and localization of iNOS in normal colonic mucosa and colon carcinomas induced by azoxymethane (AOM) in male F344 rats were examined. All colon carcinoma tissues examined were found to have an increased expression of iNOS protein as compared to normal colonic mucosa. A pronounced staining of iNOS protein was detectable on the luminal surface of carcinoma epithelial cells, but not in normal colon epithelium.⁽¹⁶²⁾ The find ings sug gest that inhibition of NO production could be a possible approach to cancer prevention. Docosahexaenoic acid and1'-acetoxychavicol acetate, which have suppressive effects on colon carcinogenesis, decreased NO production in LPS-stimulated murine macrophages by suppressing iNOS gene expression.⁽¹⁶³⁾ Reports related to these investigations can be found in the attached list of publications.^{(164-166, 254)}
Cytotoxic Factor Present in the Cabbage Butterfly

Insects might be a good source of novel bioactive materials such as anti-cancer drugs. Cytotoxic activity against human gastric carcinoma TMK-1 cells has been found in ex tracts of the body fluid of Pieris brassicae and Pieris rapae, both known as the cab bage butterfly. When TMK-1 cells were treated with an extract from pupae of P. brassicae, the resultant morphological changes in dying cells were similar to those found for pupae of P. rapae. The extract of P. brassicae exerted cytotoxicity with the IC₅₀ value against TMK-1 cells at the 1/10⁷ dilution. The cytotoxic substance in the pupae of P. brassicae was suggested to be a protein, like pierisin, the anti-cancer principle in P. rapae.⁽¹⁶⁷⁾




	11. Cancer Prevention Division



		Research in the Cancer Prevention Division is primarily focused on the anticarcinogenic properties of a wide variety of natural and synthetic substances. Elucidation of environmental as well as en dogenous factors involved in human cancer development, is also a main objective. The results obtained are anticipated to facilitate the development of preventive measures against human cancers. Mutagens in Water from the Nishitakase River Water samples from the Nishitakase river in Kyoto, especially taken at sites below sewage plants, show significantly high mutagenicity. Among five mutagenic compounds detected, the structure of a compound was determined to be 2-[2-(acetylamino)-4-[bis(2-methoxyethyl) amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole(PBTA-1).⁽¹⁵⁹⁾ PBTA-1 is a newly identified mutagen, inducing 3,000,000 revertants of S. typhimurium YG1024 per mg with S9 mix. PBTA-1 is suggested to be derived from an azo dye which is an industrial material. Comutagenic Action of Norharman Norharman, found widely in our environment, is not mutagenic to S.typhimurium strains, but it becomes mu tagen ic to TA98 and YG1024 in the presence of non-mu tagenic aniline with S9 mix.⁽¹⁶⁰⁾ Two mutagenic compounds were isolated from a reaction mixture between norharman and aniline with S9 mix, and their structures were determined to be a coupled compound of norharman and aniline, 9-(4'-aminophenyl)-9H-pyrido[3,4-b]indole, and its hydroxyamino derivative. Thus, the appearance of mutagenicity by norharman with aniline in the pres ence of S9 mix was suggested to be as follows. First the cou pled mutagenic compound is formed by an enzymatic reaction be tween norharman and aniline. Then, the amino group is converted to ahydroxyamino group and further activated by forming esters. These ultimate forms react with DNA bases to induce mutations in TA98 and YG1024. Suppression of Intestinal Polyp Development by a Selective Inhibitor of Cyclooxygenase-2 (COX-2), Nimesulide NSAIDs have been shown to sup press development of colon tumors, but gastrointestinal side effects caused by the inhibition of COX-1 activity are recognized as a serious problem for clinical application. Therefore, the effect of nimesulide, a selective in hibitor of COX-2, on the development of intestinal polyps in Min mice, which have a mutation in Apc gene, was in vestigated. Female Min mice at 4 weeks old were given 400 ppm nimesulide in a diet for 11 weeks. This treatment decreased the number of intestinal polyps to 52% of the control value, and also re duced the size of the polyps.⁽¹⁶¹⁾ The results suggest that nimesulide is a good candidate chemopreventive agent for human colon cancer with fewer gastrointestinal side effects. Increased Expression of Inducible Nitric Oxide Synthase (iNOS) in Colon Carcinomas Excessive nitric oxide (NO) production is recognized as a causative factor in cancer development. In order to elucidate the involvement of NO in colon carcinogenesis, the expression level and localization of iNOS in normal colonic mucosa and colon carcinomas induced by azoxymethane (AOM) in male F344 rats were examined. All colon carcinoma tissues examined were found to have an increased expression of iNOS protein as compared to normal colonic mucosa. A pronounced staining of iNOS protein was detectable on the luminal surface of carcinoma epithelial cells, but not in normal colon epithelium.⁽¹⁶²⁾ The find ings sug gest that inhibition of NO production could be a possible approach to cancer prevention. Docosahexaenoic acid and1'-acetoxychavicol acetate, which have suppressive effects on colon carcinogenesis, decreased NO production in LPS-stimulated murine macrophages by suppressing iNOS gene expression.⁽¹⁶³⁾ Reports related to these investigations can be found in the attached list of publications.^{(164-166, 254)} Cytotoxic Factor Present in the Cabbage Butterfly Insects might be a good source of novel bioactive materials such as anti-cancer drugs. Cytotoxic activity against human gastric carcinoma TMK-1 cells has been found in ex tracts of the body fluid of Pieris brassicae and Pieris rapae, both known as the cab bage butterfly. When TMK-1 cells were treated with an extract from pupae of P. brassicae, the resultant morphological changes in dying cells were similar to those found for pupae of P. rapae. The extract of P. brassicae exerted cytotoxicity with the IC₅₀ value against TMK-1 cells at the 1/10⁷ dilution. The cytotoxic substance in the pupae of P. brassicae was suggested to be a protein, like pierisin, the anti-cancer principle in P. rapae.⁽¹⁶⁷⁾