Chemopreventive effects of Paullinia cupana Mart var. sorbilis, the guaraná, on mouse hepatocarcinogenesis.

Guaraná (Paullinia cupana) is originally from Amazon, Brazil. Its effects on mouse hepatocarcinogenesis have been investigated in this study. Mice were treated with N-nitrosodiethylamine (DEN), received three different doses of P. cupana added to commercial food, and euthanized after 25 weeks. Gross lesions were quantified, and preneoplastic lesions (PNL) were histologically measured. Cellular proliferation was evaluated by immunobloting for the proliferating cell nuclear antigen (PCNA). The incidence and multiplicity of macroscopic lesions were reduced. The PNL number and PCNA expression were reduced in the highest P. cupana dose. According to these results, guaraná presented inhibitory effects on DEN hepatocarcinogenesis in mice.

Increased susceptibility to urethane-induced lung tumors in mice with decreased expression of connexin43.

Gap junction intercellular communication capacity and connexin expression are reportedly decreased in human lung cancer. The mechanisms by which connexins, the gap junction proteins, act as tumor suppressors are unclear. In order to understand the involvement of connexins in tumorigenesis, we analyzed the effect of the heterologous deletion of Gja1 [the connexin43 (Cx43) gene] on the development of lung adenomas in mice. Heterozygous (Cx43(+/-)) and wild-type mice (Cx43(+/+)) were treated or not with single doses of urethane at 15 and 17 days after birth. Twenty-five weeks later, both the number and size of nodules were increased in Cx43(+/-) mice as compared with Cx43(+/+) mice. Moreover, the lesions were histologically more aggressive in the heterozygous mice. However, no increase in spontaneous lesions was observed in the lungs of untreated Cx43(+/-) mice. Heterozygous mice effectively presented lower expression of Cx43 genes and decreased amounts of Cx43. In conclusion, our results indicate that deletion of one allele of the Cx43 gene clearly favors the carcinogenic effect of urethane administration and results in a higher susceptibility to lung adenoma formation in mice.