We have shown that, in contrast to selenomethionine (SeMet) or selenite, methylseleninic acid (MSeA) and Se-methylselenocysteine (MSeC) exert prostate cancer (PCa) inhibitory effect in preclinical models. Here we investigated the prostate proteome signatures of mice treated with each selenium (Se) form for hypothesis generation concerning their potential in vivo molecular targets and cancer risk modification. Nude mice bearing subcutaneous PC-3 xenografts were treated daily with each Se form (3 mg Se/kg) orally for 45 days. Five prostates were pooled from each group. Their proteomes were profiled by LC-MS/MS with iTRAQ labeling. Of the 1,088 proteins identified, 72 were significantly modulated by one or more Se forms. MSeA and MSeC each induced separate sets of tumor suppressor proteins and suppressed different onco-proteins. Proteins induced by selenite and shared with MSeC were related to energy metabolism (e.g., fatty-acid synthase), and those induced by SeMet included vimentin and heat-shock protein-70, favoring cancer growth. While proteome changes induced by MSeA were associated with PCa risk reduction, desirable risk-reducing signatures induced by MSeC were counterbalanced by risk-promoting patterns shared with selenite and SeMet. We propose that the balance of oncogenic vs. suppressor protein patterns in the prostate may impact the direction of PCa risk modification by a given selenium.
Bibliographical noteFunding Information:
We thank Dr. LeeAnn Higgins, Mr. Todd Markowski, and Mr. Thomas F. McGowan of the Mass Spectrometry and Proteomics Facility in Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota for helpful discussion and technical support. We are also grateful to Dr. Fekadu Kassie and Prof. Stephen S. Hecht of the University of Minnesota Masonic Cancer Center for advice concerning iTRAQ application. This research was supported by National Cancer Institute Grants R01CA126880 and R01CA95642 and the Hormel Foundation. No potential conflicts of interest were disclosed.
Copyright 2012 Elsevier B.V., All rights reserved.