Vincristine regulates the phosphorylation of the antiapoptotic protein HSP27 in breast cancer cells

Vincristine is an antitumor drug that inhibits microtubule polymerization, causes G2/M arrest and induces apoptosis. 2D-PAGE and MALDI-TOF-MS analysis of vincristine effects on MCF7 cells, revealed a vincristine upregulated form and a vincristine downregulated form of the antiapoptotic protein HSP27. These findings linked to the lack of vincristine effect over HSP27 mRNA, suggest a protein post-translational modification. Further assays indicated the presence of a phosphorylated peptide, containing serine 82, only in the vincristine upregulated form. Serine 82 phosphorylation was confirmed using specific antibodies. Thus, phosphorylation of HSP27 may play a role in the cellular response to vincristine.