OBJECTIVES: DNA repair proteins have emerged as potential predictors for immunotherapy response alongside PD-L1 expression, tumor-infiltrating lymphocytes (TILs) and tumor mutational burden. We analyzed expression of PD-L1, TILs count and expression of the homologous recombination (HR) protein RAD51, as potential prognostic factors in patients with resected non-small-cell lung carcinoma (NSCLC). MATERIALS AND METHODS: Discovery set included 96 NSCLC patients from the University Hospital Olomouc (Czech Republic) and a replication set included 1109 NSCLC patients from University Hospital Zurich (Switzerland). Tissue microarrays (TMAs) were stained using the automated staining platform Ventana Benchmark Ultra with antibodies against RAD51,CD3, CD8, CD68 and PD-L1. RESULTS: Loss of nuclear RAD51 protein was associated with high TILs (r=-0.25, p = 0.01) and PD-L1 status (10.6 vs. 2.4 %, p = 0.012) in patients receiving neoadjuvant chemo-/radiotherapy (CT/RT). In silico analysis from the TCGA data set showed a negative relationship between RAD51 mRNA expression and CD45 (r = ‒0.422, p < 0.0001), CD68 (r = ‒0.326, p < 0.001), CD3 (r = ‒0.266, p < 0.001) and CD8 (r = ‒0.102, p < 0.001). RAD51 low/PD-L1 high patients were clustered as separate entity in the replication set and in TCGA dataset. High TILs status was significantly associated with improved OS in the replication set (unadjusted HR = 0.57, 95 % CI 0.42-0.76, p < 0.001). Similar results have been seen for CD3, CD8 and CD68. CONCLUSIONS: In conclusion, RAD51 nuclear loss is weakly associated with increased TILs and high PD-L1 at the time of surgery in curatively resected NSCLC and after prior exposure to neoadjuvant chemo- or radiotherapy. Both high TILs and RAD51 nuclear loss were confirmed as independent prognostic factors in curatively resected NSCLC.

Clinic of Oncology University Hospital Zurich Switzerland

Department of Clinical and Molecular Pathology Institute of Translational and Molecular Medicine Faculty of Medicine and Dentistry Palacky University Hnevotinska 3 775 15 Olomouc Czech Republic

Department of Medical Oncology and Hematology Cantonal Hospital CH 9007 St Gallen Switzerland

Department of Pathology and Molecular Pathology University Hospital Zurich Switzerland

Department of Thoracic Surgery University Hospital Zurich Switzerland

Department of Tuberculosis and Respiratory Diseases Faculty of Medicine and Dentistry Palacky University and University Hospital Olomouc Czech Republic

Faculty of Medicine and Dentistry Palacky University Olomouc Czech Republic

Institute of Molecular and Translational Medicine Faculty of Medicine and Dentistry Palacky University and University Hospital in Olomouc Olomouc Czech Republic

Laboratory of Genomics Institute of Molecular and Translational Medicine Faculty of Medicine and Dentistry Palacky University Olomouc Czech Republic

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