Abstract A004: The role of calcium in metastatic progression

Calcium is essential to the structural stability of integrin proteins implicated in platelet–cancer cell interactions, namely integrins GPIIb/IIIa and a_vb_3, which share a common beta subunit (Pelletier et al., J Biol Chem, 1996), (Zhang and Chen, Cell Adh Migr, 2012). Additionally, calcium is essential for ligand binding to these integrins (e.g., fibrinogen) that bridge platelets and cancer cells (Raborn et al., Biochemistry, 2011) and for the downstream signaling following mechanical and chemical stimulation in the integrin microenvironment (Michelson, Platelets, 2013). Platelet-cancer cell interactions are key players in cancer progression as platelets support metastatic dissemination (Morris et al., Biochim. Biophys. Acta BBA - Rev. Cancer, 2022). Despite previous studies recognizing calcium’s role in integrin stability and function, calcium’s importance for platelet support in cancer progression is not well understood. Therefore, we aim to (1) characterize the receptor expression and ligand binding ability of GPIIb/IIIa and a_vb₃ on respective cells via anti-CD41a (for platelets and breast cancer MDA-MB-231 cells) and anti-a_vb₃ antibody (for lung cancer A549 cells), (2) characterize platelet function by assessing platelet aggregation using light transmission aggregometry and platelet adhesion on a thrombogenic surface, (3) characterize platelet-cancer cell interaction via flow cytometry, and (4) assess cancer cell invasion in the presence of platelets via transwell assay; all in the presence of an environment with calcium chelation and hypercalcemic conditions. Our results demonstrate that platelet GPIIb/IIIa, cancer cell GPIIb/IIIa (MDA-MB-231) and cancer cell integrin a_vb₃ (A549) are modulated with calcium chelation. Additionally, platelet function, specifically aggregation is significantly decreased with calcium chelation and significantly increased with hypercalcemia. We also observed that the interaction between platelets and cancer cells is reduced with calcium chelation, platelet-MDA-MB-231 interaction specifically being significantly reduced in the presence of sodium citrate. Our overall hypothesis is that the observed effect of calcium levels of platelet and cancer cell integrins could have a significant influence on platelet-cancer cell interactions and cancer cell migration in hypercalcemia, often seen in patients with malignancy. A greater understanding of these interactions could have impact for the design of specific inhibitors with anti-metastatic effects and potentially lead to novel targeted therapies to combat metastatic dissemination.

Citation Format: Kenise Morris, Anne-Laure Papa. The role of calcium in metastatic progression [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A004.