In NSCLC patients, several clinical trials are testing the efficacy of DNA damage response inhibitors (DDRi) and chemotherapy in combination with anti-PDL1 drugs. DDRi activate antitumor immune responses in cancer through release of cytosolic DNA leading to STING activation, stimulation of neo-antigens and release of pro-inflammatory cytokines. Our group has previously demonstrated a strong correlation between EMT and immune activation, showing that tumors with high EMT score have the highest levels of targetable immune markers.
We analyzed mRNA and protein expression of immune and EMT genes in the lung adenocarcinoma (LUAD) and lung squamous carcinoma (LUSC) TCGA NSCLC and in a panel of NSCLC cells, correlating them with the presence of somatic mutations in DDR genes. Contemporary, we treated NSCLC cell lines in vitro with cisplatin and various DDRi combinations, including PARP/ATR/ATM/WEE-inhibitors, to determine the effect on DNA damage and immune markers expression (by western blot and RPPA analysis).
In both TCGA cohorts, immune markers mRNA expression clustered together and were positively correlated with EMT genes. In the LUAD cohort, high expression of CD274 (PDL1) was associated with high levels of other immune suppressive markers (LAG3, IDO1, PDCD1LG2, HAVCR2, CTLA4, ICOS, CD4, and CD40) and chemokines (CXCL10, CCL5, CCL2). Notably, expression of STING pathway mediators (TBK1 and TMEM173) and mesenchymal markers (TWIST1/2, SNAI1, SMO, and TGFB1) were positively related with CD274. Moreover, we found that mutations in DDR related genes TP53, RB1, POLE, FANCM and BRCA1 were allied with higher levels of targetable immune suppressive markers (LAG3, IDO1, and CD274) and the mesenchymal marker, TWIST1, but lower levels of TMEM173. Finally, in vitro treatments with DDRi and cisplatin increased DNA damage, as demonstrated by increased p-H2AX, and proportionally upregulated PDL1 and STING in some cell lines.
Our findings provide rationale to combine DNA damaging agents with immunotherapy drugs targeting immune suppressive markers in NSCLC. From our data, expression of EMT genes and deleterious mutations in DDR genes represent the best candidates to select patients that can benefit from these combinations.
Clinical trial identification
Legal entity responsible for the study
MD Anderson Cancer Center.
All authors have declared no conflicts of interest.