Dissecting the genetic basis of cancer immune evasion in squamous cell carcinoma

PROJECT SUMMARY/ABSTRACT While immunotherapies have revolutionized cancer treatment, a subset of patients, particularly those with squamous cell carcinomas (SCCs) found in the skin, oral cavity, larynx, esophagus, lung, and cervix, exhibit varying responses to immune checkpoint blockade (ICB), resulting in a 60% relapse rate. These disparities in patient outcomes strongly suggest the existence of genetic variations that underlie their distinct responses to ICB. Although the specific oncogenic mutations responsible for driving relapse in SCC patients remain unclear, it is imperative to grasp the mechanisms of cancer immune evasion in individuals with specific genetic profiles to enhance the precision of immunotherapy. Recent research has identified a population of tumor-initiating cells (TICs) within skin and oral cavity SCCs that resist anti-tumor immunity and drive relapse. These rare TICs are often overlooked in tumor immunology studies despite their critical role in promoting cancer recurrence. We have identified that activating mutations in the PIK3CA gene, found in 20% of cutaneous and head and neck SCCs, can enhance stemness and intrinsic immune resistance in SCCs, resulting in rapid relapse after ICB. The proposed research will consist of two main aims. The F99 phase aims to determine how PIK3CA mutations expand the immune-resistant TICs in SCC tumors. I will investigate whether PIK3CA activating mutations induce TIC self-renewal and dedifferentiation following ICB treatment. I will explore the role PIK3CA mutants have on the Sox2 protein, a critical transcription factor for maintaining stemness, and its stability in TICs. This aim will provide insights into the ability to disrupt PIK3CA mutant-induced Sox2 stability to reduce SCC relapse after immunotherapy. The K00 phase is broader with the goal of identifying how genetic alterations enhance the intrinsic immune resistance of TICs. In the first part of the K00 phase, I will design a genome-wide CRISPR screen to identify candidate genes responsible for endowing PIK3CA mutant TICs with resistance to T cell- mediated ferroptosis. I will explore how PIK3CA mutations reprogram the metabolism of TICs to enhance their intrinsic resistance to T cell-induced ferroptosis. I will then expand the scope to identify other genetic determinants beyond PIK3CA mutations that drive immune evasion in TICs. By CRISPR gene editing, I will introduce other oncogene activation, tumor suppressor inactivation, chromosomal rearrangements, gene fusions, and copy number variations into keratinocytes and evaluate their potential to promote immune evasion in vivo. This work will discover potential drug targets and biomarkers for predicting patient responses to immunotherapy. My ultimate goal is to become an independent investigator at a leading research institution and to conduct interdisciplinary, NIH-funded research contributing to the fields of cancer biology, stem cell biology, and immunology, and by characterizing novel mechanisms of cancer stem cell-specific immune resistance.