Abstract 4456: Inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX2) inhibition reprogram the tumor microenvironment and suppress tumor growth in hepatocellular carcinoma
Authors: Wang Ronghua , Kaltenmeier Christof , Yang Ruiqi , Haykal Tony , Yazdani Hamza , Tohme Celine , Geller David , Tohme Samer , Billiar Timothy 
Published: June 2023

Abstract
Hepatocellular carcinoma is a common cancer worldwide and a leading cause of cancer-related death. Chronic inflammation, accumulation of genetic changes and alternations of the liver microenvironment are critical during the process of carcinogenesis and development of HCC. Inducible nitric oxide synthase (iNOS or NOS2)-derived NO and cyclooxygenase-2 (COX2) are important parts of the neoplastic inflammatory environment. Continuous exposure to moderate to high concentrations of NO, produced by inducible NO synthase (iNOS) and COX2, promotes neoplastic transformation, chemotherapeutic resistance, enhanced cell proliferation, increased inflammation and immune resistance. Our previous study reported that iNOS promoted stem-like characteristics and activation of liver cancer stem cells through Notch signaling pathway. iNOS activity in both the liver cancer stem cells and the microenvironment contributes to tumor progression in mice, suggesting that targeting iNOS in the entire tumor could have therapeutic benefit in HCC. iNOS-derived NO and COX2-derived prostaglandin E2 (PGE2) were shown to promote feed-forward iNOS/COX2 crosstalk because NO induced COX2 and PGE2 induced NOS2. Our research showed that iNOS inhibition with the iNOS inhibitor (1400W) and COX2 inhibitor (Celebrex) diminished HCC tumor growth. The cytokine analysis revealed considerably lower levels of inflammatory cytokines including, IL-6, tissue inhibitor of matrix metalloproteinase-1 (TIMP1), macrophage inflammatory protein-3alpha (MIP-3alpha), IL-1B, CC chemokine subfamily of eosinophil chemotactic proteins eotaxins (CCL11), M-CSF, thymus and activation-regulated chemokine (TARC, CCL17) and leukemia inhibitory factor (LIF) in HCC with iNOS/COX2 inhibition. iNOS/COX2 levels influence the polarization and spatial location of lymphoid cells including CD8+ T cells. Targeting iNOS/COX2 blockade improved CD8+ T cell penetration into the tumor core. We also found that iNOS/COX2 blockade result in more CD4+ T helper cells and CD8+ tumor infiltrating lymphocyte (TIL), but reduce the number of exhausted CD4+ T cells and CD8+ T cells (PD1-high, Lag3+, CD39+ Tex). The results suggesting that iNOS/COX2 inhibitor therapy may alleviate HCC growth by promoting a anti-tumorigenic TME, modifying lymphoid spatial localization and gene expression phenotypes and decreasing T-cell exhaustion.
Citation Format: Ronghua Wang, Christof Kaltenmeier, Ruiqi Yang, Tony Haykal, Hamza Yazdani, Celine Tohme, David Geller, Samer Tohme, Timothy Billiar. Inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX2) inhibition reprogram the tumor microenvironment and suppress tumor growth in hepatocellular carcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4456.