Recently, 4 biological subtypes have been defined with SCLC-Inflamed (I) experiencing benefit from immunotherapy. Previously, we showed that chemotherapy and PARP/CHK1-i synergize with immunotherapy and activate STimulator of INterferon Genes (STING) pathway. We hypothesize that DDRi may sustain intratumoral shifts toward SCLC-I.
We tested anti-proliferative effect and changes in immune related protein (WB, ELISA) production after treatment of selected SCLC cell lines (n=10) with various DDRi (ATMi, ATRi, DNA-PKi) +/- radiotherapy (RT) +/- ENPP1-inhibitor (ENPP1i, that inhibits the phosphodiesterase that degrades the STING ligand, 2’3’-cGAMP). We also tested the drug effects on PBMCs. Finally, we investigated expression of innate immune pathways in SCLC cohort.
From George et al. cohort, STING gene levels were correlated with higher expression of other innate immune pathway, MAVS (like IFITH1 and DDX60) and IFI16 (p<0.001). Thus, we studied changes on innate immune pathways activation (STING, MAVS, IFI16), inflammatory cytokine production and anti-proliferative effects induced by DDRi +/- RT +/- ENPP1i. Among all drug tested, we found that DNA-PKi sustain STING, MAVS and IFI16 protein activation in SCLC cells. We also detected STING activation by ELISA for 2’3’-cGAMP and by ENPP1-i. The addition of ENPP1i and RT in vitro is able to further enhance all innate immune pathways activation and is accompanied by significant increase in pro-inflammatory cytokine productions by both cancer and PBMCs cells (e.g. INFbeta, IL-6, IL-1β, TNF-alfa, CCL2) and STING-related chemokines (CCL5 and CXCL10) along with PD-L1. Also, STING activation was confirmed by increased levels of extracellular and intracellular 2’3’-cGAMP following DNA-PKi +/- RT +/- ENPP1i (at various time points up to 72 hours). Finally, we found that TP53 is activated at early time-points of treatment in response to DNA-PKi and is then downregulated by combination with ENPP1i in SCLC cell lines, thus suggesting a potential novel mechanism of interaction between these stress-related pathways.
Our findings highlight for the first time a positive pro-immune effect of DNA-PKi in SCLC models and on immune cells, suggesting various innate immune pathways as mediator of immune responsive.
The authors.
AIRC.
All authors have declared no conflicts of interest.