8. Functional Characterization of CIGB-300, a Novel Proapoptotic Synthetic Peptide that Impairs the Casein Kinase 2(CK2)-mediated Phosphorylation

YASSER PERERA; JEOVANIS GIL; HERNÁN FARINA; LUIS J. GONZALEZ; ROBERTO GÓMEZ; DANIEL F. ALONSO; SILVIO E. PEREA

Varadero

Simposio; Satellite Meeting, Proteomics in Cancer and Infectious Diseases; 2007

Proteomics in Cancer and Infectious Diseases

CIGB-300, formerly know as P15-tat, is a pro-apoptotic peptide with demonstrated antiproliferative activity in vitro and antitumoral activity in vivo. This hypothesis-driven peptide was initially selected by their ability to impair the in vitro CK2-mediated phosphorylation in one of its substrates through direct binding to the conserved acidic phosphoaceptor domain. However, the actual in vivo target(s) on human cancer cells among the hundreds of CK2 substrates as well as the subsequent events that leads to apoptosis on tumor cells remains to be determined. In this work we identified the multifunctional oncoprotein nucleophosmin/B23 as a major target for CIGB-300. In vivo, the CIGB-300-B23 interaction was evidenced by pull-down experiments and confirmed by the early in situ co-localization of both molecules in the cell nucleolus. Moreover, CIGB-300 inhibits the CK2-mediated phosphorylation of B23 in a dose-dependent fashion both in vitro and in vivo as evidenced using the recombinant GST fusion protein and the metabolic labeling approach, respectively. Such phosphorylation impairment was correlated with the ability of CIGB-300 to induce nucleolar disassembly as documented by the use of established markers for nucleolar structure. Finally, we demonstrated both at molecular and cellular level that such sequence of events leads to the rapid and massive onset of apoptosis. Collectively, these findings provide important clues by which the CIGB-300 peptide exerts its proapoptotic effect on tumor cells and highlights the suitability of the B23/CK2 pathway for cancer targeted therapy.