This invention relates to methods of inducing dephosphorylation of a hyperphosphorylated cell cycle regulatory protein in a tumor cell in which hyperphosphorylation of said protein contributed to cell transformation, the method comprising contacting the tumor cell with a procyanidin oligomer of five monomeric units connected via a C-4.fwdarw.C-8 linkage. Examples of such compounds are [EC-(4.beta..fwdarw.8)].sub.4-EC, and [EC-(4.beta..fwdarw.8)].sub.3-EC-(4.beta..fwdarw.8)-C, wherein EC is epicatcchin and C is catechin.
This application claims the benefit, under 35 USC Section 119, of the U.S. Provisional Appl. No. 60/540,641 filed Jan. 30, 2004, the disclosure of which is hereby incorporated herein by reference.
