Chunk #61 — 4. WIP1 SUPPRESSES THE STRESS RESPONSE: UPDATE — 4.5. Wip1 attenuates the response to oncogenic stress and promotes tumorigenesis — 4.5.1. Cooperation of Wip1 with oncogenes in tumorigenesis
Several reports have characterized the incidence of PPM1D amplification and Wip1 overexpression in breast cancer (11, 13, 17, 98–100), and there is a positive correlation between PPM1D amplification and poor prognosis (98). More recently, Lambros et al. showed that Wip1 overexpression was more prevalent than PPM1D amplification, since Wip1 was overexpressed in 21% of the tumors, whereas PPM1D amplification was present in only 6% of the tumors (107). It should be noted, however, that the reported 6% PPM1D amplification in breast cancer is low compared to previous reports (11, 13, 17, 98–100), and the reason for this inconsistency is unclear. Lambros et al. also showed a significant correlation of Wip1 overexpression and tumor grade. Most of the tumors that exhibited Wip1 overexpression were also negative for p53 (107), which is consistent with other reports that p53 is frequently wild-type and not overexpressed, whereas mutant p53 frequently is overexpressed (98). On the other hand, and unlike the results of Rauta et al. (98), PPM1D amplification was not correlated with a poor prognosis (107). These results imply that, in addition to PPM1D
