Figure 1.

(A) SRA737 IC₅₀ values in a panel of 51 SCLC cell lines, seven NSCLC cell lines, three other cancer type cell lines (one pancreatic-SW1990, one colon-SNUC1 and one bladder-5637 cancer cell line) indicate a wide range of sensitivities in vitro.

(B) Representative image showing micronuclei (MN) formation following SRA737 treatment in SCLC cell line H69, after DAPI staining.

(C) Quantification of MN formation shows a significant increase of MN following 24h treatment with SRA737 in multiple cell lines (two human SCLC cell lines, H69 and H446 cells, and one SCLC murine cell line RPP, two NSCLC cell lines, Calu-1 and Calu-6, and one murine breast cancer cell lines, EMT6/P). Data presented as mean ± SD and p values by t-test ***p<0.001, **p<0.01, *p<0.05.

(D) Immunoblot analysis shows increased PD-L1 protein expression in a panel of SCLC cell lines treated with 1 μM SRA737 for 24 hours.

(E) SRA737 treatment for 72 hours augments PD-L1 cell surface expression, as measured by flow cytometry, in SCLC cell lines. Data presented as mean ± SD and p values by t-test ***p<0.001.

(F) Immunoblot analysis of protein markers of the STING pathway, including total and phospho STING (S366), total and phospho IRF3 (S396), in lysates collected from two SCLC cell lines treated with 1 μM SRA737 for 24 and 72 hours.

(G) Quantitative PCR (qPCR) measurement of CCL5, CXCL10 and IFNβ mRNA expression in three SCLC cell lines treated with 1 μM SRA737 or 24 and 72 hours. Data presented as mean ± SD and p values by t-test ***p<0.001.