Potential tumor suppressor. Acts as a KRAS-specific effector protein. May promote apoptosis and cell cycle arrest. Stabilizes STK3/MST2 by protecting it from proteasomal degradation. {ECO:0000269|PubMed:12732644; ECO:0000269|PubMed:16012945; ECO:0000269|PubMed:19525978}.