Figure 3. Kras^G12D/Twist1-induced lung tumors regress following combined oncogene inactivation.

(A) Gross appearance of CRT lung tumors following 4 weeks of combined Kras^G12D and Twist1 oncogene inactivation (n = 4). H – heart and L – liver. (B) Serial axial microCT of the same CRT mouse following 4 weeks of combined Kras^G12D and Twist1 oncogene inactivation (n = 4) demonstrates tumor regression. Blue arrowheads denote lung tumors. S –spine. (C) Serial coronal FDG microPET-CT demonstrate decreased metabolic tumor burden after 1 week of combined Kras^G12D and Twist1 oncogene inactivation (n = 2). (D) Normal appearing H&E histologic section from lung tumor moribund CTR OFF mouse following 4 weeks of combined Kras^G12D and Twist1 oncogene inactivation (n = 4). Black bar equals 200 µm. CRT lung tumors demonstrate (E) decreased proliferation and (F) increased apoptosis following combined Kras^G12D and Twist1 oncogene inactivation. CRT lung tumors were assayed for proliferation using Ki-67 IHC and quantified as in Figure 2E (n≥2 mice per time point). CRT lung tumors were assayed for levels of apoptosis using cleaved caspase 3 IHC and quantified (n≥2 mice per time point). Low - <1%; Med – 1–4%; and High - >4%. (G) Percentage of senescent lung tumors per mouse does not increase following combined Kras^G12D and Twist1 oncogene inactivation. The level of senescence associated-beta-galactosidase (SA-β-Gal) correlates inversely with proliferative capacity of individual tumors. CRT lung tumors were assayed for levels of SA-β-Gal and quantified (n≥2 mice per time point). Low - <10%; Med – 10–30%; and High - >30%. Representative panels of tumors with “Low” and “High” SA-β-Gal staining.