Abstract 2508: Clinical significance of PARP7 (TIPARP) gene copy number alterations in human non-small cell and head & neck carcinomas

Abstract

Abstract Introduction: PARP7, encoded by the TIPARP gene, is a monoART involved in cellular stress responses and with immunomodulatory functions in cancer. The PARP7 gene is amplified in a subset of squamous cell carcinomas and ongoing clinical studies are assessing its role as anti-cancer therapeutic target (NCT04053673, NCT05127590) Here, we analyzed the frequency of PARP7 copy number alterations and its association with tumor immune microenvironment (TIME) features and outcomes in non-small cell lung cancer (NSCLC) and head & neck squamous-cell carcinoma (HNSCC) cohorts. Methods: The PARP7 gene copy number and amplification was analyzed using a dual probe fluorescence in situ hybridization (FISH) assay in two retrospective cohorts of NSCLC (Cohort #1, n=124) and HNSCC (Cohort #2, n=83) represented in tissue microarray format. In a subset of cases, the PARP7 copy number was also studied using whole exome DNA sequencing. The TIME was assessed on consecutive tumor sections using a multiplexed quantitative immunofluorescence panel including the markers DAPI, cytokeratin, CD4, CD8 and PD-L1 coupled to computational pathology analysis. The association between the markers, with clinicopathologic variables and survival was studied. Results: Increased PARP7 copy number (>2 copies/cell) was identified in 55% of NSCLCs (85% of them of squamous-cell histology) and 76% of HNSCCs. A high copy number (>3 copies/cell) was identified in 22% cases from both tumor type cohorts. After adjustment of the PARP7 gene copy number by the chromosome 3 centromeric probe (CEN3) signal, PARP7 amplification (>1.5 PARP7/CEN3 signal) was detected in 22% of NSCLC cases and 34% of HNSCC. A higher number of cases with PARP7 copy number gains were identified using FISH than with whole exome DNA sequencing. No significant associations between the PARP7 gains/losses and major clinicopathologic variables were found. However, higher PARP7 copy number was associated with reduced CD8+ or CD4+ tumor infiltrating lymphocytes (TILs) and a numerically lower tumor PD-L1 protein levels in HNSCC. Elevated PARP7 copy number was associated with shorter overall survival in both studied tumor types. Conclusion: Elevated PARP7 gene copy number identifies a subset of lung and head & neck squamous-cell carcinomas with unfavorable TIME features and adverse prognosis. Detection of PARP7 gene abnormalities using FISH in tumor biopsy samples is sensitive and has potential as a predictive biomarker. Citation Format: Viviana A. Ahumada, Kristen McEachern, Kristy Kuplast-Barr, Kurt Alex Schalper. Clinical significance of PARP7 (TIPARP) gene copy number alterations in human non-small cell and head & neck carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2508.