Abstract A17: TRPM7 kinase domain is involved in breast tumor cell metastasis

Abstract

Abstract Introduction: TRPM7 (transient receptor potential melastatin 7) is a non-selective cation channel fused to protein kinase domain at the C-terminal whose activity is linked to the control of actomyosin contractility. TRPM7 mediates adhesion and migration of breast cancer cells and promotes breast tumor metastasis. The lack of cell-permeable inhibitors of the kinase domain represents a barrier to understand the kinase function. Methods: Herein, we discover the first small molecule (KD-1) that targets TRPM7 kinase activity and characterize its mechanism of action in-vitro, in-cells and in-vivo. By using this inhibitor, we are investigated the involvement of TRPM7 kinase domain in breast tumor cell metastasis. Results: Mg2+ starvation, which promotes TRPM7 kinase activity, induces phosphorylation of eEF2. Treatment of Mg2+-starved HEK293 cells with KD-1 decreased eEF2 phosphorylation, consistent with TRPM7 kinase activity suppression in-cells. KD-1 decreased the binding of Myosin IIB to TRPM7 in HEK293 and MDA-MB-231 cells. And when MDA-MB-231 and BT 549 cells were treated with increasing doses of KD-1, no change in cell viability was seen. Interestingly, KD-1 inhibited migration and invasion in the MDA-MB-231 and BT 549 cells that is reportedly regulated by TRPM7 kinase activity. Finally, the bioluminescent signals (to assess lung metastasis) were significantly lower in KD-1-treated mice (25 and 50 mg/kg/day) than in mice treated with vehicle control (P ≤0.05, 2-sided t-test.). Conclusion: The discovered compound represents the first inhibitor that targets the kinase activity of transient receptor potential melastatin 7 (TRPM7). Inhibition of TRPM7 kinase activity may reduce or block breast tumor progression and/or metastasis. Citation Format: Tamer S. Kaoud, Xuemei Xie, Jihyun Park, Clint D.J. Tavares, Shreya Mitra, Micael Cano, Mohamed F. Radwan, Chandra Bartholomeusz, Kevin N. Dalby. TRPM7 kinase domain is involved in breast tumor cell metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A17.