PIK3CA and malignant colon neoplasm: Recently, NVP-TNKS656 and XAV939 were reported to negatively regulate the protein stability of β-catenin through inhibition of tankyrase 1/2, which interacts with a highly conserved domain of AXIN and stimulates its degradation through the ubiquitin–proteasome pathway.2 Therefore, we investigated the combinatorial effect of a TNKS inhibitor NVP-TNKS656 with MEK inhibition in KRAS and PIK3CA mutant colon cancer cells.