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

Marco Antonio Lacerda-Abreu,Daniela Cosentino-Gomes,Nathália Rocco-Machado,Thais Russo-Abrahão,José Roberto Meyer-Fernandes,Claudia Fernanda Dick,Michelle Tanny Cunha Nascimento,Thaís Cristino Rocha-Vieira,Luiz Fernando Carvalho-Kelly

doi:10.3390/ijms221810096

Abstract

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.

Highlights

Breast cancer is a heterogeneous and complex disease that varies in morphological and molecular structure, as well as the clinical course, requiring different approaches to diagnosis and treatment [1,2]
Cell lines are classified based on their expression patterns of oncogenic receptors: oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor type 2 (HER2), such as MCF-7 (Luminal A, ER+, PR+, and HER2− ) or MDA-MB-231 [2]
Our group demonstrated that MDA-MB-231 cells, after

Summary

Introduction

Breast cancer is a heterogeneous and complex disease that varies in morphological and molecular structure, as well as the clinical course, requiring different approaches to diagnosis and treatment [1,2]. Cell lines are classified based on their expression patterns of oncogenic receptors: oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor type 2 (HER2), such as MCF-7 (Luminal A, ER+ , PR+ , and HER2− ) or MDA-MB-231 (triple-negative expression: ER− , PR− and HER2− ) [2]. Triple-negative breast cancer cells (TNBC) are significantly more aggressive than tumours of the other molecular subtypes, mainly because the patients have substantially shorter survival following their first metastatic event [3]. High levels of dietary Pi have been associated with the tumorigenesis of various types of cancer [10,11,12]

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