Previous studies localized p16 protein expression to conducting airway Club cells and distal alveolar epithelial type II cells; two progenitor cell types believed to be cells of origin for NSCLC.11, 13, 14 p16 message was induced ninefold in RB1-deficient primary type II cell isolates as compared to RB1-proficient control cells consistent with RB1 mediating suppression of p16 at the transcriptional level (Figure 1c). Here, RB1 is linked to non-small cell lung carcinoma.