PEBP1 and cancer: Based on this grading scheme, we confirmed that loss of RKIP (mediated by A549-Ad-shRKIP injections) caused the appearance of severe malignant tumors (average tumor grade: ∼3) in the lung compared to control A549-Ad-shGFP-injected mice (average tumor grade: ∼1.5) (Figure 5C, 5D).