Telomere damage enhances immunogenicity of neuroblastoma and accelerates response to anti-PD-L1 treatment

Telomerase is active in the majority of high-risk neuroblastomas, a pediatric tumor associated with poor patient outcomes. In other cancer types, resistance to immune checkpoint blockade was overcome by induction of telomere dysfunction using the telomerase substrate precursor 6-thio-2'-deoxyguanosine (6-thio-dG). Here, we explored whether induction of telomere dysfunction improves the anti-tumor efficacy of immune checkpoint inhibition in neuroblastoma. 6-thio-dG treatment induced the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway and programmed cell death ligand-1 (PD-L1) expression in murine neuroblastoma cells in vitro. In a MYCN;ALK^F1174L-driven transgenic neuroblastoma mouse model, 6-thio-dG treatment delayed tumor growth and prolonged survival. Treatment with anti-PD-L1 also led to growth delay and improved survival, which occurred; however, only after an initial lag phase. Combination with anti-PD-L1 improved the anti-tumor effects of 6-thio-dG and overcame the initial lag phase of anti-PD-L1 treatment. Mechanistically, 6-thio-dG combined with anti-PD-L1 treatment induced cGAS and PD-L1 expression and promoted immune cell infiltration in the tumors. Our findings suggest that 6-thio-dG treatment activates the cGAS-STING pathway in neuroblastoma and that induction of telomere dysfunction in combination with immune checkpoint blockade boosts intratumoral immune cell infiltration and improves survival in a high-risk neuroblastoma mouse model.