Abstract 680: FLLL12 is a small molecule JAK2 inhibitor that inhibits JAK-STAT3 pathway in head and neck cancer

Abstract

Abstract Purpose: We have recently reported that FLLL12, a synthetic curcumin analog, induces apoptosis of lung cancer cells through a death receptor (DR) 5-dependent pathway and in squamous cell carcinoma of head and neck (SCCHN) by modifying multiple Bcl-2 proteins. However, the direct molecular target (receptor) of FLLL12 is unknown. The purpose of the current study is to identify the receptor of FLLL12. Methods: Computer-aided molecular docking was used to predict molecular interaction. Isothermal titration calorimetry and thermal shift assays were used to confirm molecular interactions in a cell free system. SCCHN cell lines were used to study the effect of this interaction on JAK-STAT3 pathway. Protein expression levels were measured by Western blotting. Results: Computer-aided molecular docking modeling of FLLL12 and JAK2 (PDB code: 5CF5) predicted that FLLL12 fit well into the JAK2 catalytic pocket. Although curcumin also fit into the JAK2 catalytic pocket, the binding sites were different for FLLL12 and curcumin. Docking score for FLLL12, natural ligand and curcumin were -7.2, -12.1 and -6.9, respectively. FLLL12 also docked into the STAT3 catalytic pocket (PDB code: 5AX3). However, the docking score was worse than those for natural ligand and curcumin (-5.1, -7.3 and -7.4 respectively). We confirmed that FLLL12 interacted with JAK2 in a cell free system using recombinant JAK2. Isothermal titration calorimetry assay revealed one binding site for both FLLL12 and the FDA-approved JAK inhibitor ruxolitinib. The Ka values were 3.84E6±1.03E5 and 2.31E7±6.78E6 M-1, respectively. FLLL12 and JAK2 interactions were further confirmed by thermal shift assay. Kd values were 1.12±0.14 μM and 2.24 ±0.18 μM for ruxolitinib and FLLL12, respectively. Two hour pretreatment with FLLL12 also inhibited IL-6 induced phosphorylation of JAK2 and STAT3. Finally, FLLL12 strongly inhibited constitutively active STAT3 phosphorylation in SCCHN cell lines, a downstream effector of JAK. Conclusions: Our results strongly suggest that FLLL12 is a novel small molecule inhibitor for JAK2 and FLLL12-JAK2 interaction inhibits IL-6-induced as well as constitutively active STAT3 phosphorylation, thus has great promise for cancer prevention and therapy. Grant Support: Start-up fund from Department of Hematology and Medical Oncology, Winship Cancer Institute of Emory University and from Department of Pharmaceutical Sciences and Research, Marshall University. Citation Format: ARM Ruhul Amin, ASM Anisuzzaman, Abu B. Siddique, James R. Fuchs. FLLL12 is a small molecule JAK2 inhibitor that inhibits JAK-STAT3 pathway in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 680.