Title:Inorganic Phosphate (Pi) in the Breast Cancer Microenvironment: Production,
Transport and Signal Transduction as Potential Targets for Anticancer
Strategies
Volume: 23
Issue: 3
Author(s): Marco Antonio Lacerda-Abreu*José Roberto Meyer-Fernandes*
Affiliation:
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, Brazil
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, Brazil
Keywords:
Inorganic phosphate, breast cancer microenvironment, ectonucleotidases, ectophosphatases, H+-dependent Pi transport, Na+-dependent Pi transport.
Abstract: Tumor cells develop a high demand for inorganic phosphate (Pi) due to their high growth
rates and energy requirements. Serum Pi concentrations in cancer patients have been found to be two
to four times higher than baseline levels in healthy individuals. Twofold Pi accumulation was observed
in breast cancer cells in the mouse tumor microenvironment. In the breast tumoral microenvironment,
ectonucleotidases and ectophosphatases—presenting catalytic sites facing the extracellular
environment—could be involved in the extracellular release of Pi to be internalized by Pi transporters
to fuel the high energy requirement typical of cancer cells. Two Pi transporters were characterized in
breast cancer cells (Na+-dependent and H+-dependent) with strong associations with tumor processes
such as proliferation, migration, adhesion, and epithelium-mesenchymal transition (EMT). Moreover,
a high extracellular Pi concentration stimulates ROS production in triple-negative breast cancer cells
by Pi transport stimulation. Several compounds show a potent ability to inhibit ectonucleotidases, ectophosphatases,
Pi transporters, and Pi-modulated signal pathways in breast cancer cells and regulate
proliferation, migration, adhesion, and EMT. This review article aimed to gather the relevant experimental
records regarding Pi's effects on the breast cancer microenvironment and points to possible inhibitors
for ectonucleotidases, ectophosphatases, Pi transporters, and Pi-modulated signal pathways as
potential chemotherapeutic agents or Pi acting as a potent enhancer of classical chemical-induced cytotoxicity
in triple-negative breast cancer cells.