In vitro chemopreventive properties of a soybean peptide, lunasin

High soy intake is linked to cancer prevention. There are several known anticarcinogenic compounds in soybean, but their mechanisms of action remain unclear.; Lunasin is a novel compound from soybean shown to be chemopreventive in vitro and in vivo. Lunasin, a 43-amino acid peptide, contains a –RGD-cell adhesion motif followed by 8 aspartic acid residues at the carboxyl end and a structurally conserved helix region. Lunasin binds to chromatin and leads to mitosis arrest when lunasin gene is transfected into mammalian cells. Addition of lunasin peptide to chemical carcinogen treated mouse fibroblast cells greatly reduces foci formation. In the first animal study, lunasin applied topically inhibits skin tumorigenesis in SENCAR mice. Lunasin binds preferentially to deacetylated histones and inhibits core histone acetylation, suggesting an epigenetic mechanism of action.; The goals of my project are to: (a) demonstrate the anti-transformation properties of lunasin in oncogene-induced cell culture systems; (b) investigate the effects of lunasin on cell proliferation; and (c) elucidate the chemopreventive mechanism of lunasin by establishing cellular localization of lunasin and the effects of lunasin on protein expression. The efficacy of lunasin in inhibition of oncogene-induced transformation in mouse fibroblast cells is determined. Cells are transfected with ras oncogene or E1A tumor suppressor gene in the presence or absence of lunasin. Results show that lunasin suppresses ras- or E1A-induced foci formation by 40% at a concentration as low as 100 nM using a 3-day treatment protocol. The polyaspartic end of lunasin is necessary for the suppressive effect. Furthermore, lunasin reduces anchorage independent growth of stably ras-transfected mouse fibroblast cells by 30% in colony assay. In contrast to its strong inhibitory effects on cell transformation, lunasin peptide does not affect cell proliferation in normal and transformed cells. Lunasin internalizes into the nucleus of cells within hours of administration when observed under immunostaining. Lastly, Western analyses show that lunasin significantly increases p21 expression in ras or E1A-transfected NIH 3T3 cells.