Abstract
Upper aerodigestive tract (UADT) cancers of the oral cavity and esophagus are a significant global health burden, and there is an urgent need to develop relevant animal models to identify chemopreventive and therapeutic strategies to combat these diseases. Antizyme (AZ) is a multifunctional negative regulator of cellular polyamine levels, and here, we evaluate the susceptibility of keratin 5 (K5)-AZ transgenic mice to tumor models that combine chemical carcinogenesis with dietary and genetic risk factors known to influence human susceptibility to UADT cancer and promote UADT carcinogenesis in mice. First, p53(+/-) and K5-AZ/p53(+/-) (AZ/p53(+/-)) mice were placed on a zinc-deficient (ZD) or zinc-sufficient (ZS) diet and chronically exposed to 4-nitroquinoline 1-oxide. Tongue tumor incidence, multiplicity and size were substantially reduced in both ZD and ZS AZ/p53(+/-) mice compared with p53(+/-). AZ expression also reduced progression to carcinoma in situ or invasive carcinoma and decreased expression of the squamous cell carcinoma biomarkers K14, cyclooxygenase-2 and metallothionein. Next, AZ-expressing p53(+/-) and p53 null mice were placed on the ZD diet and treated with a single dose of N-nitrosomethylbenzylamine. Regardless of p53 status, forestomach (FST) tumor incidence, multiplicity and size were greatly reduced with AZ expression, which was also associated with a significant decrease in FST epithelial thickness along with reduced proliferation marker K6 and increased differentiation marker loricrin. These studies demonstrate the powerful tumor suppressive effects of targeted AZ expression in two distinct and unique mouse models and validate the polyamine metabolic pathway as a target for chemoprevention of UADT cancers.