Figure 6
Cdk2 is a therapeutic target in tumors that have bypassed senescence. A) Western blotting for the indicated proteins in Irbp-Cyclin D1, p18Ink4c -/- (D1p18null) pineal lysates at the indicated ages, Irbp-Cyclin D1, p18Ink4c -/- (D1p18null) tumors that are early (ET1, ET2) or well-established (T3 – T7), and in Irbp-Cyclin D1, p53 -/- (p53T) tumor lysates, as indicated. B) Representative immunohistochemical staining for Cdk2 and Ki67, as indicated, in serial sections of Irbp-Cyclin D1, p18Ink4c -/- pineal glands (PG1 and PG2) that have an emerging tumor within a senescent background. “T” denotes the emerging tumor; “PG” denotes the pineal gland background. C) Representative immunohistochemical staining for Cdk2 and Ki67, as indicated, in serial sections of Irbp-Cyclin D1, p18Ink4c -/- tumors (T1 and T2), showing areas of low Ki67 and low Cdk2 positivity (asterisks). D) Quantitation of cellular accumulation (upper panel) and SABG-positive proportion (lower panel) of Irbp-Cyclin D1, p18Ink4c -/- and Irbp-Cyclin D1, p53 -/- tumor cells after treatment for 7 days with CVT313 or vehicle, as indicated. Asterisk denotes statistical significance (p-value = 2.7 × 10-3, 9.8 × 10-4 respectively, for the upper panel; 6.4 × 10-4 and 6.3 × 10-4, respectively for the lower panel). E) Representative SABG staining of wild-type (WT, upper panel), pretumorigenic Irbp-Cyclin D1 (D1, second panel), Irbp-Cyclin D1, p18Ink4c -/- (D1p18n, 3rd panel) and Irbp-Cyclin D1, p53 -/- (D1p53n, lower panel) tumor cells in culture, treated for 7 days with CVT313 or vehicle, as indicated.