Abstract
We discovered a crucial change common to all platinum resistant (CR) NSCLC cells, wherein a high level of reactive oxygen species (ROS) modulates tumor metabolism. CR cells activate the kynurenine (KYN) pathway (KP) during excessive oxidative stress to maintain high ROS for proliferation by catabolizing tryptophan (TRP) to KYN via indoleamine 2,3-dioxygenase-1 (IDO1); and by expressing (3-5x) higher levels of programmed death-ligand 1 (PD-L1) compared to platinum sensitive cells (p<0.02; n=8). We detected significant increases in IDO1 activity (3-4x), identified by the KYN/TRP ratio, in CR cells’ culture media (p<0.05; n=8). Extracellular KYN is known to program naïve T-cells to the immune suppressive regulatory T-cell (T-reg) phenotype. Using a human peripheral blood mononuclear cell (PBMC) co-culture system, we found a higher frequency of regulatory T-cells (Tregs; CD4+CD25+Foxp3+) and a lower frequency of effector T-cells (Teffs CD3+CD8+) and NK cell (CD3-CD314+CD335+) activity in co-culture with CR cells compared to cisplatin sensitive cancer cells. Importantly, inhibition of IDO1 and Tryptophan 2,3-Dioxygenase (TDO2), the enzymes involved in the rate limiting step in the KP, with the dual inhibitor AT-0174 at 20µM (48h) suppressed Tregs, but enhanced Teffs and NK cell populations in CR co-cultures. Next, we used a syngeneic mouse model of LLC (Lewis lung cancer) vs cisplatin resistant LLC-CR, to examine the effects of AT-0174 (170 mg/kg; P.O. once daily) in combination with anti-PD1 antibody (10 mg/ml; I.P. once every 3 days). Consistent with the in vitro model, analysis of mice with LLC-CR tumors found higher intratumoral T-reg and lower NK cell populations. Treatment with AT-0174 resulted in higher tumor infiltrating lymphocytes of Teffs and NK and lower Treg frequency in LLC-CR tumors than treatment with a selective IDO1 inhibitor (epacadostat). More importantly, the combination of AT-0174+antiPD1 reversed the immunosuppressive tumor microenvironments with further enhancement in Teffs and NK frequencies and diminished tumor growth in CR allografts with a significant reduction of total tumor weight compared with LLC mouse tumors (n=10, P<0.01). Our new findings support the potential therapeutic efficacy of the dual IDO/TDO inhibitor AT-0174 as an immuno-therapeutic treatment that enhances tumor immune surveillance and blocks tumor metabolism related survival mechanisms in platinum resistant NSCLC tumors. Support by the Dept. of Veterans Affairs.
Citation Format: Sydney Spector, Chunjing Wu, Dan Nguyen, George Theodore, Ashley Garcia, Lynn Feun, Niramol Savaraj, Medhi Wangpaichitr. Targeting kynurenine pathway using novel IDO/TDO dual inhibitor (AT0174) to modulate tumor microenvironment in platinum resistant non-small cell lung cancer cancer: An immunometabolism compliment markers [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 2325.