Promotion of Lung Tumorigenesis By Beta-catenin

Although mutations in Kras are present in 21% of lung tumors, there is a high level of heterogeneity in phenotype and outcomes amongst lung cancer patients suggesting the importance of other pathways. Wnt/β-catenin signaling is a known oncogenic pathway that plays a well defined role in colon and skin cancer but its role in lung cancer remains unclear. We show that activation of Wnt/β-catenin in the bronchiolar epithelium of the adult lung does not promote tumor development by itself. However, activation of Wnt/β- catenin signaling leads to a dramatic increase in tumor formation both in overall tumor number and size compared to KrasG12D alone. We show that activation of Wnt/β- catenin signaling significantly alters the KrasG12D tumor phenotype resulting in a phenotypic switch from bronchiolar epithelium to the highly proliferative distal progenitors found in the embryonic lung. This is associated with a decrease in E- cadherin expression at the cell surface which may increase metastasis in Wnt/β-catenin signaling positive tumors. Together, these data suggest that activation of Wnt/β-catenin signaling in combination with other oncogenic pathways in lung epithelium may lead to a more aggressive phenotype due to the imposition of an embryonic distal progenitor phenotype accompanied by decreased E-cadherin expression. We performed microarray analysis of control murine lung, CC10-cre:KrasG12D, and CC10-cre:Ctnnb1ex3flox:LSL-KrasG12D double mutant micro-dissected murine lung tumors to determine their transcriptional phenotype. Lungs of five-month-old mice were PBS inflated and all the tumors in each lobe were dissected. The total number of tumors obtained from three out of the 5 pulmonar lobes of each animal was called a sample the other two lobes were saved in case there were problems and the array needed to be repeated. Trizol was used to isolate RNA for microarray analysis. Samples & Genotypes: control murine lung n=2 animals, CC10-cre:KrasG12D n=2 animals, and CC10-cre:Ctnnb1ex3flox:LSL-KrasG12D n=2 animals.