Hydrogen Peroxide Generation as an Underlying Response to High Extracellular Inorganic Phosphate (Pi) in Breast Cancer Cells

• Published in: International journal of molecular sciences 2021-09, Vol.22 (18), p.10096
• Main Authors: Lacerda-Abreu, Marco Antonio, Russo-Abrahão, Thais, Rocco-Machado, Nathália, Cosentino-Gomes, Daniela, Dick, Claudia Fernanda, Carvalho-Kelly, Luiz Fernando, Cunha Nascimento, Michelle Tanny, Rocha-Vieira, Thaís Cristino, Meyer-Fernandes, José Roberto
• Format: Article
• Language: English
• Subjects: Acetylcysteine; Adhesion; Antioxidants; Breast cancer; breast cancer cells; Cell adhesion & migration; cell migration; Cell proliferation; Growth rate; H+-dependent Pi transport; Hydrogen peroxide; Mesenchyme; Metabolism; Metastases; Metastasis; Mitochondria; Na+-dependent Pi transport; NAD(P)H oxidase; Oxygen consumption; Pi-induced H2O2 production; Protein kinase C; Tumors
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms221810096

According to the growth rate hypothesis (GRH), tumour cells have high inorganic phosphate (Pi) demands due to accelerated proliferation. Compared to healthy individuals, cancer patients present with a nearly 2.5-fold higher Pi serum concentration. In this work, we show that an increasing concentration of Pi had the opposite effect on Pi-transporters only in MDA-MB-231 when compared to other breast cell lines: MCF-7 or MCF10-A (non-tumoural breast cell line). Here, we show for the first time that high extracellular Pi concentration mediates ROS production in TNBC (MDA-MB-231). After a short-time exposure (1 h), Pi hyperpolarizes the mitochondrial membrane, increases mitochondrial ROS generation, impairs oxygen (O2) consumption and increases PKC activity. However, after 24 h Pi-exposure, the source of H2O2 seems to shift from mitochondria to an NADPH oxidase enzyme (NOX), through activation of PKC by H2O2. Exogenous-added H2O2 modulated Pi-transporters the same way as extracellular high Pi, which could be reversed by the addition of the antioxidant N-acetylcysteine (NAC). NAC was also able to abolish Pi-induced Epithelial-mesenchymal transition (EMT), migration and adhesion of MDA-MB-231. We believe that Pi transporters support part of the energy required for the metastatic processes stimulated by Pi and trigger Pi-induced H2O2 production as a signalling response to promote cell migration and adhesion.