Cell lines and culturing

Primary desmoid and normal fibroblast cell cultures were established as previously described^68,69. Tumor cell line 141 (T141) was genotyped to have the T41A beta-catenin mutation, while tumor cell line 219 (T219) was S45F beta-catenin mutation. Both of the desmoid cell lines had matched normal fibroblast cell lines, which are denoted N141 and N219. For normal fibroblasts, the cells are derived similarly but from skin tissue from the same desmoid tumor patients. Obtaining paired samples is extremely difficult, and it is possible that at the time of this experiment that these matched cell lines are the only ones of their kind. The fibroblast cell line (CRL7518) was purchased from ATCC and culture identically to the primary cell lines; this ATCC cell line served as the unaffected cell line. Monolayer cell cultures were grown in DMEM supplemented with 10% fetal bovine serum and maintained at 37 °C in 5% CO₂. Cells were divided when confluent and experiments were performed between the third and sixth passages.