Post-irradiation intratumoral heterogeneity modulates response to immune checkpoint inhibition therapy in a murine melanoma model

Jie Wang, Shivani Sud, Yanli Qu, Liantao Li, Jiajie Zhang, David Marron, Nicole Michelle Knape, Isaiah James Kim, Kyle Thomas Wagner, Tian Zhang, Yuxia Zhao, Genyan Guo, Andrew Z. Wang

Research output: Contribution to journalArticlepeer-review


Purpose: The underlying mechanism for radiation as a potentiator of immune checkpoint inhibition (ICI) is unclear. We developed a novel murine model to investigate the effects of post-irradiation intratumoral heterogeneity (ITH) on response to ICI. Experimental design: Parental mouse melanoma B16F10 cells were irradiated in vitro (5Gy x 3 fractions), then an a priori determined number of resulting colonies were implanted in C57BL/6J immunocompetent mice creating syngeneic models of unirradiated (parental) and irradiated tumors with low (irradiated-L) and high (irradiated-H) ITH. Mice were treated with placebo, α-PD-L1, α-CTLA-4 or dual ICI. Murine tumors underwent whole exome sequencing (WES). Clinically correlated paired pre- and post-irradiation patient rectal adenocarcinoma samples underwent WES. Results: Irradiated-L tumors showed increased tumor mutational burden (TMB) and a sustained decrease in ITH. Irradiated-L tumors were predicted to express five neoantigens with high variant allele frequency/clonal distribution. Mice with irradiated-L and irradiated-H versus parental B16F10 tumors demonstrated longer overall survival with dual ICI. Only mice with irradiated-L tumors experienced an overall survival benefit with single agent ICI. Clinically correlated rectal adenocarcinoma samples showed similarly increased TMB and decreased ITH following irradiation. Conclusions: Post-irradiation ITH modulates ICI response in a murine melanoma model. Irradiation may offer a mechanism to widen the therapeutic window of ICI.

Original languageEnglish (US)
Article number100864
JournalNeoplasia (United States)
StatePublished - Feb 2023


  • checkpoint inhibition
  • immunotherapy
  • in situ vaccine
  • intra-tumor heterogeneity
  • neoantigen
  • radiation therapy
  • tumor mutational burden

ASJC Scopus subject areas

  • Cancer Research


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