Mutational inactivation of transforming growth factor β receptor type II in microsatellite stable colon cancers

We previously demonstrated that mutational inactivation of transforming growth factor β type II receptors (RIIs) is very common among the 13% of human colon cancers with microsatellite instability. These mutations principally cluster in the BAT-RII polyadenine sequence repeat. Among microsatellite stable (MSS) colon cancers, we now find that non- BAT-RII point mutations inactivate RII in another 15% of cases, thus doubling the known number of colon cancers in which RII mutations are pathogenetic. Functional analysis confirms that these mutations inactivate RII signaling. Moreover, another 55% of MSS colon cancers demonstrate a transforming growth factor β signaling blockade distal to RII. The transforming growth factor β pathway and RII in particular are major targets for inactivation in MSS colon cancers as well as in colon cancers with microsatellite instability.