RASSF9 and neoplasm: Recent studies have shown that TAK1 uses MAPKs and nuclear factor κB as two main downstream targets to execute its tumor suppression or activation activities.[8, 9, 10, 14, 16, 34] In this study, we performed co‐immunoprecipitation coupled with mass spectrometry and found RASSF9 to be a downstream target of TAK1.