Characterization of inorganic phosphate transport in the triple-negative breast cancer cell line, MDA-MB-231

Abstract

BackgroundRecent studies demonstrate that interstitial inorganic phosphate is significantly elevated in the breast cancer microenvironment as compared to normal tissue. In addition it has been shown that breast cancer cells express high levels of the NaPi-IIb carrier (SLC34A2), suggesting that this carrier may play a role in breast cancer progression. However, the biochemical behavior of inorganic phosphate (Pi) transporter in this cancer type remains elusive.MethodsIn this work, we characterize the kinetic parameters of Pi transport in the aggressive human breast cancer cell line, MDA-MB-231, and correlated Pi transport with cell migration and adhesion.ResultsWe determined the influence of sodium concentration, pH, metabolic inhibitors, as well as the affinity for inorganic phosphate in Pi transport. We observed that the inorganic phosphate is dependent on sodium transport (K0,5 value = 21.98 mM for NaCl). Furthermore, the transport is modulated by different pH values and increasing concentrations of Pi, following the Michaelis-Menten kinetics (K0,5 = 0.08 mM Pi). PFA, monensin, furosemide and ouabain inhibited Pi transport, cell migration and adhesion.ConclusionsTaken together, these results showed that the uptake of Pi in MDA-MB-231 cells is modulated by sodium and by regulatory mechanisms of intracellular sodium gradient.General Significance: Pi transport might be regarded as a potential target for therapy against tumor progression.

Ectophosphatase activity in the triple‐negative breast cancer cell line MDA‐MB‐231

“…Therefore, cells depend on a pool of Pi to support such mechanisms (Bobko et al, 2017; Brown & Razzaque, 2018; Moreno‐Sánchez et al, 2007). Since Pi is an anionic molecule, its uptake from the extracellular medium to the cytosol is mediated by transporters (Biber et al, 2013; Lacerda‐Abreu et al, 2018), which was recently described in breast cancer (Lacerda‐Abreu et al, 2019; Russo‐Abrahão et al, 2018). Ectophosphatases may also participate in the process of obtaining Pi because these enzymes catalyze hydrolysis of phosphorylated molecules, releasing free Pi (Fontanillo & Köhn, 2016).…”

“…Acid ectophosphatase catalyzes the dephosphorylation of phosphorylated molecules (P‐molecules) and phosphorylated proteins (P‐proteins). The Pi released by ectonucleotidase and ectophosphatase enzymes is taken up by Pi transporters (Na + ‐dependent or H + ‐dependent) in breast cancer cells (Lacerda‐Abreu & Meyer‐Fernandes,2019; Lacerda‐Abreu et al,2019; Russo‐Abrahão et al,2018)…”

“…Recently, it has been demonstrated that two Pi transporters, a Na + ‐dependent Pi transporter (with high affinity to Pi) and a H + ‐dependent Pi transporter (with low affinity to Pi), participate in making phosphate available to breast tumor cells (Lacerda‐Abreu et al, 2019; Russo‐Abrahão et al, 2018). In addition to NTPDases, NPPs, and ecto‐5ʹ‐nucleotidases, acid phosphatase should be considered another important enzyme for release of Pi in the tumor microenvironment, possibly captured by Pi transporters to meet the high Pi demand required for cell proliferation, adhesion, and migration.…”

“…Pi is an essential nutrient for cells and is present in the tumor microenvironment. Recently, two Pi transporters were described in breast cancer: H + ‐dependent Pi transporter and Na + ‐dependent Pi transporter, which play a role in tumor progression (Lacerda‐Abreu et al, 2019, 2018; Russo‐Abrahão et al, 2018). Certain ectoenzyme groups are involved in the availability of extracellular phosphate to the cells; these enzymes are responsible for dephosphorylation processes on the external surface of cells (Lacerda‐Abreu & Meyer‐Fernandes, 2019).…”

Resveratrol is an inhibitor of sodium‐dependent inorganic phosphate transport in triple‐negative MDA‐MB‐231 breast cancer cells

“…Pi-reaction mixture incubated on ice for 60 min(Russo-Abrahão et al, 2018).To determine Na + -dependent Pi transport, values of Pi uptake in the presence of 116 mM NaCl were subtracted the values obtained in the absence of sodium (116 mM Chloride Choline)(Lacerda-Abreu et al, 2019;Russo-Abrahão et al, 2018).…”