MDM2 and neoplasm: Interventional cell cycle inhibitor therapy, exemplified by DeltaRex-G—a tumor-targeted retrovector encoding a cytocidal “dominant-negative” (dnG1) expression construct of the cyclin G1 (CCNG1 oncogene); dnG1 expression blocks cell-activation, transcription control, and survival functions of the cyclin G1/Cdk/myc/Mdm2/P53 axis.