Composition of protein expression of activin signaling proteins in colon cancers with loss of expression in at least one pathway member.

Two of the 51 tested MSS colon cancers lost ACVR1 protein expression, 7 lost ACVR2 expression, and 5 lost pSMAD2 expression. While one cancer lost expression of all three pathway components, the remaining 4 tumors with loss of pSMAD2 expression showed expression in activin's primary receptors, while maintaining expression of total SMAD2 and TGFBR2, indicative that loss of pSMAD2 may be a separate primary event. The remaining 39 primary MSS colon cancers revealed no loss of activin signaling components.