PTEN Deficiency Contributes to the Development and Progression of Head and Neck Cancer

The sequencing of the head and neck cancer has provided a blueprint of the most frequent genetic alterations in this cancer type. They include inactivating mutations in Notch, p53, and p16(ink4a) tumor suppressor genes, in addition to nonoverlapping activating mutations of the PIK3CA and RAS oncogenes or inactivation of the tumor suppressor gene PTEN. Notably, these genetic alterations, along with epigenetic changes, result in increased activity of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, which is present in most head and neck squamous cell carcinomas (HNSCCs). Moreover, we show here that approximately 30% of HNSCCs exhibit reduced PTEN expression. We challenged the biologic relevance of this finding by combining the intraoral administration of a tobacco surrogate, 4-nitroquinoline 1-oxide, with a genetically defined animal model displaying reduced PTEN expression, achieved by the conditional deletion of Pten using the keratin promoter 14 CRE-lox system. This provided a specific genetic and environmentally defined animal model for HNSCC that resulted in the rapid development of oral-specific carcinomas. Under these experimental conditions, control mice did not develop HNSCC lesions. In contrast, most mice harboring Pten deficiency developed multiple SCC lesions in the lateral border and ventral part of the tongue and floor of the mouth, which are the preferred anatomic sites for human HNSCC. Overall, our study highlights the likely clinical relevance of reduced PTEN expression and/or inactivation in HNSCC progression, while the combined Pten deletion with exposure to tobacco carcinogens or their surrogates may provide a unique experimental model system to study novel molecular targeted treatments for HNSCC patients.