Abstract 4067: PD-L1 Expression, CD8 Cells and MHC-class-1 Beta-2-microglobulin Expression in Advanced Non-Small Lung Cancer

Introduction: PD-L1 expression has been approved as predictive biomarker for immune checkpoint inhibitors (ICI) in non-small cell lung carcinoma (NSCLC). In case of lack of PD-L1 expression in tumor biopsies, 8-10% of patients will respond to ICI. However, in case of > 50% PD-L1 tumor expression half of patients show no response. Tumor immune escape phenotypes are characterized by loss of MHC-class-I and a lower grade of CD8 T-cell infiltration, despite upregulation of PD-L1 expression. At least one of the four phenotypes of MHC-class-I and PD-L1 co-expression is considered responsible for non-responsiveness. We investigated the frequency of PD-L1, MHC-class-I β2-microglobulin (β-2M) co-expression and presence of CD8 cells in advanced NSCLC. Methods: Analysis was performed on formalin fixed, paraffin embedded (FFPE) transbronchial or transthoracic tumor biopsies of 27 patients with advanced NSCLC. Immunohistochemistry was performed using Ventana Benchmark Ultra immunostainer. PD-L1 was detected using Ventana PD-L1 (SP263) Assay (CE IVD), CD8 by Ventana CONFIRM anti-CD8 (SP57) antibody and MHC-class I β2-M by Agilent-Dako polyclonal rabbit anti-human beta-2-Microglobulin. PDL1 expression was scored as percentage positive tumor cells according to the manufacturers guideline, β2-M was scored as positive or negative in tumor cells and CD8 cells as low (+), intermediate (++) or high (+++) numbers in tumor or peritumoral stroma. Results: In 27 patients IHC staining was performed. PDL1 expression was scored as <1%, 1-49% and ≥50% in 17, 3, and 7 patients, respectively. PD-L1 positive (>1%) patients had positive β-2M in 10 of 10 cases. PD-L1 negative tumors showed presence of β-2M in 10 of 17 cases. Seven out of 27 cases (26%) were β-2M negative; all of them were PD-L negative cases. Low CD8 score was seen in 7 patients and 2 of these patients have a PD-L1 expression >1% and positive β-2M. Conclusion: In this ongoing study one quarter of advanced NSCLC patients had no tumor MHC-class-1 β-2M expression. In our cohort β-2M negative phenotype was associated with lack of PD-L1 tumor expression. Citation Format: Lucie Hijmering-Kappelle, Jeroen Hiltermann, Birgitta Hiddinga, Anthonie van der Wekken, Nils 't Hart, Harry Groen, Wim Timens. PD-L1 expression, CD8 cells and MHC-class-1 Beta-2-microglobulin expression in advanced non-small lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4067.