Southern Arizona Veterans Affairs Health Care System 1 article published in JoVE Biology Deficient Pms2, ERCC1, Ku86, CcOI in Field Defects During Progression to Colon Cancer Huy Nguyen1, Cristy Loustaunau1, Alexander Facista1, Lois Ramsey1, Nadia Hassounah1, Hilary Taylor1, Robert Krouse2,3, Claire M. Payne1,4, V. Liana Tsikitis3, Steve Goldschmid5, Bhaskar Banerjee5, Rafael F. Perini5, Carol Bernstein1 1Department of Cell Biology and Anatomy, College of Medicine, University of Arizona, Tucson, 2Southern Arizona Veterans Affairs Health Care System, Tucson, AZ, 3Department of Surgery, College of Medicine, University of Arizona, Tucson, 4Biomedical Diagnostics and Research, Tucson, AZ, 5Department of Medicine, College of Medicine, University of Arizona, Tucson Reduced/absent expression of Pms2 and/or ERCC1 in entire crypts is a frequent event within 10 cm on each side of colonic adenocarcinomas, likely the basis of a field defect with high mutability and progression to cancer. Deficiency in Ku86 or CcOI is much less frequent in these field defects.