Overexpressed β-catenin Localizes to Plasma Membrane in Respiratory Papillomas

Recurrent respiratory papillomatosis (RRP), a disease characterized by recurrent tumors of the upper airway, is caused by human papillomavirus (HPV) types 6 and 11 (Doorbar et al., 2012). It has been suggested that the HPV early protein E6 regulates the function of the oncogene β-catenin, including a recent report which shows that HPV16 E6 can induce nuclear localization of β-catenin in a cutaneous mouse model (Bonilla-Delgado et al., 2012). β-catenin’s function in the cell is highly dependent on its localization (Brembeck et al., 2006). At the plasma membrane β-catenin mediates the interaction of the adherens junctions, which bind neighboring cells together, and the actin cytoskeleton, which is responsible for organizing internal structures of the cell (Meng and Takeichi, 2009). When β-catenin translocates to the nucleus, it functions as an oncogene because it activates transcription of a number of genes that are important in proliferation and migration. It is not known whether the “low risk” HPVs 6 and 11 induce β-catenin’s nuclear localization. We have addressed this question, comparing biopsies of respiratory papillomas to normal tissues from the same patients.