Radiation therapy (RT), a critical modality in the treatment of lung cancer, induces direct tumor cell death and augments tumor-specific immunity. However, despite initial tumor control, most patients suffer from locoregional relapse and/or metastatic disease following RT. The use of immunotherapy in non–small-cell lung cancer (NSCLC) could potentially change this outcome by enhancing the effects of RT. Here, we report significant (up to 70% volume reduction of the target lesion) and durable (up to 12 weeks) tumor regressions in conditional Kras-driven genetically engineered mouse models (GEMMs) of NSCLC treated with radiotherapy and a programmed cell death 1 antibody (α PD-1). However, while α PD-1 therapy was beneficial when combined with RT in radiation-naive tumors, α PD-1 therapy had no antineoplastic efficacy in RT-relapsed tumors and further induced T cell inhibitory markers in this setting. Furthermore, there was differential efficacy of α PD-1 plus RT among Kras-driven GEMMs, with additional loss of the tumor suppressor serine/threonine kinase 11/liver kinase B1 (Stk11/Lkb1) resulting in no synergistic efficacy. Taken together, our data provide evidence for a close interaction among RT, T cells, and the PD-1/PD-L1 axis and underscore the rationale for clinical combinatorial therapy with immune modulators and radiotherapy.
Grit S. Herter-Sprie, Shohei Koyama, Houari Korideck, Josephine Hai, Jiehui Deng, Yvonne Y. Li, Kevin A. Buczkowski, Aaron K. Grant, Soumya Ullas, Kevin Rhee, Jillian D. Cavanaugh, Neermala Poudel Neupane, Camilla L. Christensen, Jan M. Herter, G. Mike Makrigiorgos, F. Stephen Hodi, Gordon J. Freeman, Glenn Dranoff, Peter S. Hammerman, Alec C. Kimmelman, and Kwok-Kin Wong