Abstract 2095: Selective inhibition of the STAT3 pathway suppresses K-ras mutant lung tumorigenesis

K-ras mutant lung adenocarcinoma (KM-LUAD) is a difficult-to-drug cancer subtype characterized by a chronic inflammatory tumor microenvironment (TME). Resistance to therapies, including immune checkpoint blockade (ICB), necessitates therapies that target this inflammatory TME. A major transcription factor that mediates chronic inflammation in KM-LUAD is signal transducer and activator of transcription 3 (STAT3). Inhibiting STAT3 may attenuate pro-tumor inflammation. Moreover, STAT3 modulates PD-L1 transcription, so STAT3 inhibitors in conjunction with ICB may increase ICB response rates. Here, we tested the anti-tumor ability of TTI-101, a selective STAT3 inhibitor, in a STAT3 addicted lung cancer cell line (MDA-F471) and in a transgenic mouse model of KM-LUAD (CCSPCre/LSL-KrasG12D, CC-LR). For in vivo experiments, CC-LR mice were treated daily with 50 mg/kg TTI-101 by oral gavage from 10 to 14 weeks of age to model a preventative regimen or from 14 to 18 weeks of age to survey the treatment effect on established tumors. TTI-101 was compared to anti-PD-1 ICB, with 200 μg injected intraperitoneally 3 times per week. In MDA-F471 cells, TTI-101 treatment decreased cell viability, with an IC50 of ~ 20 μM. In mice treated from 10 to 14 weeks of age, TTI-101 therapy significantly reduced the tumor burden compared to ICB. TTI-101 also reduced the number of proliferating cells within tumors. Mice in the 14-18-week group displayed similar trends, but these experiments are ongoing, as are combination TTI-101 and ICB treatment regimens. Our studies show that TTI-101 can reduce K-ras driven tumor cell proliferation in vitro and in vivo, suggesting STAT3 inhibition as an alternative preventive and therapeutic modality for KM-LUAD. The ongoing combination treatments and the 14-18-week cohorts will elucidate the timing of treatments as well as reveal if by targeting the inflammatory TME we are able to improve response to ICB. Funded by: R01 grant from NIH/NCI (R01CA225977) Citation Format: Michael J. Clowers, Cody Chou, Bo Yuan, Walter V. Velasco, Melody Zarghooni, Stephen Peng, T Kris Eckols, Humam Kadara, David J. Tweardy, Seyed Javad Moghaddam. Selective inhibition of the STAT3 pathway suppresses K-ras mutant lung tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2095.