Abstract 840: The modifying effects of the extract from Okinawan sweet potato leaves in mouse colon carcinogenesis
Authors: Nakachi Saori , Tokeshi Ai , Takamatsu Reika , Arakaki Kazunari , Uehara Masatsugu , Iguchi Akira , Taira Junsei , Yoshimi Naoki 
Published: July 2016

A) Introduction

Okinawa is the southernmost islands in Japan. The climate is subtropical and largely different from mainland of Japan. There are various kinds of Okinawan specific plants and they have been eaten as food. Okinawa is also known as the region where has large number of centenarians. Okinawan specific plants could be the reason of longevity. Okinawan sweet potato is one of these specific plants. Since old times, Okinawan people have eaten the sweet potato leaves but this custom has not be seen in mainland of Japan. In fact, Okinawan sweet potato contains much higher polyphenols such as caffeoylquinic acid (CQA) derivatives than other vegetables. It is reported that CQA derivatives have anti-oxidative activity and anti-mutagenic activity. We examined the modifying effect of Okinawan sweet potato leave extract in two-step mouse colon carcinogenesis.

B) Experimental procedures

71 male ICR mice, 5 week-old, were divided into 5 groups. Mice in groups 1-3 were given azoxymethane (AOM; 10 mg/kg body weight) by intraperitoneal injection once at experimental first week, and one week after AOM injection they were administrated 1.5% dextran sulfate sodium in drinking water for 7 days. Mice in group 1 were fed control diet (CE-2, CLEA Japan, Inc),and mice in groups 2 and 3 were fed diet contained Okinawan sweet potato leaves extract (200 ppm and 1000 ppm respectively). Mice in groups 4 and 5, which were not injected AOM, were fed diet contained Okinawan sweet potato leaves extract (1000 ppm), and control diet respectively. At 12 experimental week, all mice were sacrificed and the colon tissues were removed to count the number of preneoplastic lesion, aberrant crypt foci (ACF), and were histologically analyzed the nodules larger than 3mm on colonic mucosa.

C) Results

The mean number of ACF was 1.64±0.95 (/colon length cm) in group 1, 1.18±0.79 in group 2, 1.14±0.60 in group 3, respectively. In high dose treated rats (group 3), the appearance of ACF was slightly lower than that in group 1, although not significant (P = 0.09). Histopathologically, the most nodules were lymphoid follicles but some showed neoplastic lesions. The neoplastic lesions were revealed as adenoma or adenocarcinoma. The number of the neoplasm was 9, 8 and 2 in groups 1, 2 and 3, respectively. The tumor incidence in group 3 was inhibited those in groups 1 and 2 (P&lt;0.05 by Fisher exact test). No ACF and neoplastic lesions were observed in groups 4 and 5.

D) Conclusion

It was shown that Okinawan sweet potato leave extract has a possibility to prevent the development and progression of neoplasms in mouse colon carcinogenesis model.

Citation Format: Saori Nakachi, Ai Tokeshi, Reika Takamatsu, Kazunari Arakaki, Masatsugu Uehara, Akira Iguchi, Junsei Taira, Naoki Yoshimi. The modifying effects of the extract from Okinawan sweet potato leaves in mouse colon carcinogenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 840.