Genetic Alterations That Confer High Risk to Oral Premalignant Lesions

Oral squamous cell carcinoma (OSCC) is the sixth most common human cancer worldwide. Approximately 30% of the oral premalignant lesions (OPLs) progress to OSCC, a process that may have a multifocal origin and can be promoted by carcinogens such as those found in tobacco. Our long-term goal is to identify the genetic alterations that promote high risk of progression to OPLs and to determine how those alterations modulate the response of OPLs to preventive strategies. The TP53 gene (also known as p53) and CDKN2A are the most frequently mutated genes in oral cancer, also found altered in OPLs. p53 GOF mutations and genomic alterations that result in loss of the CDKN2A gene associate with “cold” immune microenvironments in OPLs and OSCCs, with high risk of progression to carcinoma, and with extremely poor outcomes in OSCC patients. We hypothesize that the early appearance of mutations in p53 and CDKN2A inactivation modulate the oral tissue microenvironment and predispose OPLs to progress to OSCC. To test this hypothesis we will study mouse models that develop OPLs upon exposure to the tobacco-surrogate 4NQO, in the presence of p53 and/or CDKN2A mutations. Patients with high-risk OPLs could benefit from preventive strategies designed to block the malignant progression of OPLs. However, previous attempts with different chemopreventive agents have not been successful. Recently, immune checkpoint blockade with antibodies directed at programmed cell death protein 1 (PD-1) has been shown to improve the survival of patients with advanced OSCC in clinical trials, confirming the importance of the immune system in containing progression of invasive tumors. Moreover, our previous studies, confirmed by multiple independent groups, demonstrated that anti-PD-1 antibodies can also prevent the progression of OPLs to OSCC, in a 4NQO mouse model for oral carcinogenesis. Our preliminary studies indicate that the p53 and CDKN2A status of the OPLs may determine the response to anti-PD-1-mediated immunoprevention. In this proposal, we will assess the long-term benefits of anti-PD-1-mediated oral cancer prevention, to determine whether PD-1 blockade, administered in a preventive setting, can confer survival benefits, and to assess how p53 and CDKN2A mutations affect the sustained response to PD-1 blockade. To overcome resistance to anti-PD-1 we hypothesize that reactivation of p53 in OPLs carrying p53 mutations sensitizes the oral lesions to anti-PD-1. Our mouse models will allow us to test this hypothesis in vivo.