β-catenin is a well-established proto-oncogene, and mutations of this gene are common in many cancers.20, 21 Moreover, Wnts are known regulators of β-catenin signaling.11, 12, 13 To determine whether β-catenin signaling also had an important role in Wnt7a-mediated lung tumorigenesis, we probed the expression levels of β-catenin in the lungs of wild-type and Wnt7a-null mice (Figure 2). The gene discussed is WNT7A; the disease is cancer.