Pancreatic cancer is characterized by oncogenic activation of K-Ras and inactivation of the cell cycle inhibitor p16(INK4a) . We previously demonstrated that reintroduction of p16(INK4a) reversed anoikis resistance and clonogenicity of human pancreatic cancer cells, properties commonly attributed to the transforming potential of oncogenic K-Ras. Therefore, we aimed to determine the role of Ras after p16(INK4a) re-expression. Here, we show that restitution of p16(INK4a) in pancreatic cancer cell lines elicits a profound suppression of K-Ras activity. A more detailed analysis in p16(INK4a) reconstituted Capan-1 cells indicated selective reduction of both K-Ras activity and protein stability. Re-expression of K-Ras in p16(INK4a) restituted Capan-1 cells reversed the anoikis-sensitive phenotype and increased colony formation, indicating that K-Ras suppression was required for p16(INK4a) -mediated reversion of the transformed phenotype. Inducible expression of p16(INK4a) in DanG cells confirmed inhibition of K-Ras activity as well as an increase in anoikis susceptibility. Thus, our results delineate a novel functional interaction with defined biological consequences for the two most frequent alterations observed in pancreatic cancer.
© 2011 Japanese Cancer Association.