.  It is not clear if the migration defect resulting from loss of p00Kip (Besson et al., 0000), is mechanistically distinct from the invasion phenotype reported here. In their previous publication, it was shown that inhibition of Rho kinase rescued migration. Does Rho kinase inhibition also restore the ability of the p00 -/- cells to invade through thin collagen layers? If not, it would strengthen the conclusion that the authors are investigating a novel migration mechanism downstream of p00^kip0^.  