Abstract

Background and PurposeTo directly reveal the change in genome mutation, RNA transcript of tumor cells, and tumor microenvironment (TME) after stereotactic body radiotherapy (SBRT) in paired human lung tumor specimens.Materials and MethodsPaired tumor samples were collected from 10 patients with non-small cell lung cancer (NSCLC) or lung metastatic carcinoma within a week before and after SBRT. DNA and RNA of tumor tissues was extracted from the paired samples. Whole-exome and RNA sequencing assays were performed by next-generation sequencing. Gene mutation, genomic expression, T-cell receptor (TCR) repertoire, and profiling of tumor-infiltrating immune cells were analyzed through bioinformatics analysis in paired tumor samples. CD8+ T-cell infiltration and PD-L1 expressions were detected by immunostaining in tumor tissues.ResultsThe diversity of TCR repertoire and PD-L1 expression increased significantly in the TME, and the most enriched term of the gene ontology analysis was the immune response gene after receiving SBRT. SBRT induced neo-mutation of genes in tumor cells but did not increase tumor mutation burden in tumor tissues. TME displayed complex immune cell changes and infiltration and expression of immune-regulating factors such as C-X-C motif chemokine (CXCL) 10, CXCL16, interferons (IFNs), and IFN receptors. CD8+ T-cells in tumor tissues did not improve significantly after SBRT while the infiltrating TH1 and TH2 cells decreased remarkably.ConclusionSBRT improved the TCR repertoire diversity and PD-L1 expression in the TME and induced neo-mutation of genes in tumor cells but did not increase CD8+ T-cell infiltration and IFN expression in the tumor tissue within a week.

Highlights

  • Significant synergy between radiotherapy and treatment with immune checkpoint inhibitors (ICIs) would potentiate the effect of irradiation on antitumor immune response

  • We analyzed a series of genomic variations including copy-number variation (CNV), single-nucleotide variants (SNVs), and fusion genes using whole-exome sequencing (WES) in tumor tissue before and after stereotactic body radiotherapy (SBRT)

  • The Tumor mutational burden (TMB) value of the tumor tissue did not increase coincidentally in 10 samples treated with SBRT (Figure 1A, P=0.612)

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Summary

Introduction

Significant synergy between radiotherapy and treatment with immune checkpoint inhibitors (ICIs) would potentiate the effect of irradiation on antitumor immune response. Radiation-induced antitumor immune response in patients varied widely depending on the doses delivered, fraction, and irradiation site of radiotherapy [5]. Several reports confirmed that stereotactic body radiotherapy (SBRT) is more potent in terms of improving ICI anti-tumor response compared with conventional fraction radiation in patients with non-small cell lung cancer (NSCLC) [6, 7]. Numerous reports demonstrated that radiotherapy enhanced the therapeutic effect of immunotherapy [8], the direct impact of SBRT on the tumor cell genome and the tumor microenvironment (TME) remains unclear in patients with cancer. To directly reveal the change in genome mutation, RNA transcript of tumor cells, and tumor microenvironment (TME) after stereotactic body radiotherapy (SBRT) in paired human lung tumor specimens

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