Abstract
The integrated stress response (ISR) is an adaptive pathway hijacked by cancer cells to survive cellular stresses in the tumor microenvironment. ISR activation potently induces PD-L1, leading to suppression of antitumor immunity. In this study, we sought to uncover additional immune checkpoint proteins regulated by the ISR to elucidate mechanisms of tumor immune escape. The ISR coordinately induced cluster of differentiation 155 (CD155) and PD-L1, enhancing translation of both immune checkpoint proteins through bypass of inhibitory upstream open reading frames in their 5' untranslated regions. Analysis of primary human lung tumors identified a significant correlation between expression of PD-L1 and CD155. ISR activation accelerated tumorigenesis and inhibited T-cell function, which could be overcome by combining PD-1 and TIGIT blockade with the ISR inhibitor ISRIB. This study uncovers a mechanism by which two immune checkpoint proteins are coordinately regulated and suggests a therapeutic strategy for patients with lung cancer.
Significance:
The integrated stress response represents a targetable axis to improve the efficacy of immunotherapy in lung cancer by inhibiting the coordinated translational regulation of the PD-L1/PD-1 and CD155/TIGIT immune checkpoint pathways.