Re: Infantile Leukemia And Soybeans - A Hypothesis

 http://www3.interscience.wiley.com/journal/118489870/abstract?CRETRY=1&SR...

Soy-derived isoflavones inhibit the growth of adult T-cell leukemia cells in vitro and in vivo

Adult T-cell leukemia occurs in human T-lymphotropic virus type I-infected individuals and is endemic to the south-western area of Kyushu in Japan. In this communication, we examined the effect of soy isoflavones on the growth of adult T-cell leukemia cells in vitroand in vivo. In the in vitro study, daidzein and genistein but not glycitein significantly inhibited the proliferation of ED-40515 and Hut102 cells in a dose-dependent manner. Among the isoflavones studied, genistein had the highest growth-inhibitory effect; however, genistein did not exert an apparent growth-inhibitory effect on Jurkat and Molt-4 cells, which were non-adult T-cell leukemia cells. Genistein prevented the G₁/S or G₂/M transition at 3 and 10 or 30 µM, respectively. Genistein upregulated p21 protein expression together with p53 accumulation. In addition, treatment with 30 µM genistein strongly induced phosphorylation of checkpoint kinase (CHK) 2 and p53 at serines 15, 20 and 37. Caffeine, an inhibitor of ataxia-telangiectasia mutated protein kinase, alleviated the genistein-induced p53 and CHK2 phosphorylation, suggesting the involvement of DNA damage at 30 µM. However, marked phosphorylation of CHK2 and p53 could not be detected at 3 and 10 µM genistein. These data indicate that genistein has biphasic growth-inhibitory properties. The in vivo studies demonstrated that soy-derived isoflavones significantly inhibit ED-40515 cell growth and infiltration into various organs in non-obese diabetic severe combined-immunodeficiency common γ-chain knockout mice. Taken together, it is evident that soy isoflavones might serve as a promising compound for the treatment of adult T-cell leukemia. (Cancer Sci2007; 98: 1740–1746)