Rb loss enhances DNA damage response (DDR) induced by oncogenic Ras and reduces the p-p38MAPK levels by upregulation of Wip1.

a, HRas^V12 is able to induce DDR markers expression, such as p16^INK4a, p21^Cip1 and p19^ARF, p53 and p53^ser15 and γ-H2AX^ser139. Rb loss, in the presence of oncogenic Ras, increases this response. Immunoblot analysis was performed on astrocytes lysates prepared at day 6 after co-infection and selection with puromycin. b, Immunoblot analysis of p-p38MAPK and Wip1 levels was performed on cell lysates prepared at day 5 from co-infection and selection with puromycin. Densitometric analysis (in relative densitometric units) of Wip1 and p-p38MAPK protein levels. c, TMA analysis of Wip1 expression in glioma clinical samples. Representative pictures of samples are shown. The table shows median values. Wip1 immunoreactivity intensity was assigned according to the following scale: NA, non-assessable cases; −, less than 10% of neoplastic cells displayed immunoreactivity; +, 11–29% of neoplastic cells displayed immunoreactivity; ++, 30% or greater percentage of neoplastic cells displayed immunoreactivity. Phospho-histone H3 was used as a proliferation marker. Scale bars, 50 µm.