At 4 h after RT, apoptosis was an uncommon event in both tumor types (Figure 5C).Taken together, these assays provide functional data to demonstrate that only in primary lung tumors from LSL-Kras; Ink4a/ARFFL/FL mice, which retain p53, is the radiation-induced p53 response functionally intact. The gene discussed is CDKN2A; the disease is neoplasm.