Irradiation suppresses ifnγ-mediated pd-l1 and mcl1 expression in egfr-positive lung cancer to augment cd8+ t cells cytotoxicity

Chun I. Wang, Yi Fang Chang, Zong Lin Sie, Ai Sheng Ho, Jung Shan Chang, Cheng Liang Peng, Chun Chia Cheng

Research output: Contribution to journalArticlepeer-review

Abstract

Tumor cells express immune checkpoints to exhaust CD8+ T cells. Irradiation damages tumor cells and augments tumor immunotherapy in clinical applications. However, the radiother-apy-mediated molecular mechanism affecting CD8+ T cell activity remains elusive. We aimed to uncover the mechanism of radiotherapy augmenting cytotoxic CD8+ T cells in non-small-cell lung cancer (NSCLC). EGFR-positive NSCLC cell lines were co-cultured with CD8+ T cells from healthy volunteers. Tumor cell viability and apoptosis were consequently measured. IFNγ was identified secreted by CD8+ T cells and PBMCs. Therefore, RNAseq was used to screen the IFNγ-mediated gene expression in A549 cells. The irradiation effect to IFNγ-mediated gene expression was inves-tigated using qPCR and western blots. We found that the co-culture of tumor cells stimulated the increase of granzyme B and IFNγ in CD8+ T, but A549 exhibited resistance against CD8+ T cytotox-icity compared to HCC827. Irradiation inhibited A549 proliferation and enhanced apoptosis, augmenting PBMCs-mediated cytotoxicity against A549. We found that IFNγ simultaneously increased phosphorylation on STAT1 and STAT3 in EGFR-positive lung cancer, resulting in overexpression of PD-L1 (p < 0.05). In RNAseq analysis, MCL1 was identified and increased by the IFNγ-STAT3 axis (p < 0.05). We demonstrated that irradiation specifically inhibited phosphorylation on STAT1 and STAT3 in IFNγ-treated A549, resulting in reductions of PD-L1 and MCL1 (both p < 0.05). More-over, knockdowns of STAT3 and MCL1 increased the PBMCs-mediated anti-A549 effect. This study demonstrated that A549 expressed MCL1 to resist CD8+ T cell-mediated tumor apoptosis. In addi-tion, we found that irradiation suppressed IFNγ-mediated STAT3 phosphorylation and PD-L1 and MCL1 expression, revealing a potential mechanism of radiotherapy augmenting immune surveil-lance.

Original languageEnglish
Article number2515
JournalCells
Volume10
Issue number10
DOIs
Publication statusPublished - Oct 2021

Keywords

  • CD8 T cells
  • Irradiation
  • MCL1
  • Non-small-cell lung cancer
  • PD-L1
  • Radiotherapy
  • STAT1
  • STAT3

ASJC Scopus subject areas

  • Medicine(all)

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