To visualise canonical Wnt pathway activity during cancer progression we generated HT1080 human fibrosarcoma cells genetically engineered to express β-catenin/TCF-activated Venus fluorescent protein (pBARV, Biechele and Moon, 2008; here, called TOP-Venus) in a background of constitutively expressed tdTomato (Fig. 1A; Fig. S1A,B). The gene discussed is HNF4A; the disease is fibrosarcoma.