Targeting the Acidic Tumor Microenvironment: Unexpected Pro-Neoplastic Effects of Oral NaHCO3 Therapy in Murine Breast Tissue

Abstract

The acidic tumor microenvironment modifies malignant cell behavior. Here, we study consequences of the microenvironment in breast carcinomas. Beginning at carcinogen-based breast cancer induction, we supply either regular or NaHCO3-containing drinking water to female C57BL/6j mice. We evaluate urine and blood acid-base status, tumor metabolism (microdialysis sampling), and tumor pH (pH-sensitive microelectrodes) in vivo. Based on freshly isolated epithelial organoids from breast carcinomas and normal breast tissue, we assess protein expression (immunoblotting, mass spectrometry), intracellular pH (fluorescence microscopy), and cell proliferation (bromodeoxyuridine incorporation). Oral NaHCO3 therapy increases breast tumor pH in vivo from 6.68 ± 0.04 to 7.04 ± 0.09 and intracellular pH in breast epithelial organoids by ~0.15. Breast tumors develop with median latency of 85.5 ± 8.2 days in NaHCO3-treated mice vs. 82 ± 7.5 days in control mice. Oral NaHCO3 therapy does not affect tumor growth, histopathology or glycolytic metabolism. The capacity for cellular net acid extrusion is increased in NaHCO3-treated mice and correlates negatively with breast tumor latency. Oral NaHCO3 therapy elevates proliferative activity in organoids from breast carcinomas. Changes in protein expression patterns—observed by high-throughput proteomics analyses—between cancer and normal breast tissue and in response to oral NaHCO3 therapy reveal complex influences on metabolism, cytoskeleton, cell-cell and cell-matrix interaction, and cell signaling pathways. We conclude that oral NaHCO3 therapy neutralizes the microenvironment of breast carcinomas, elevates the cellular net acid extrusion capacity, and accelerates proliferation without net effect on breast cancer development or tumor growth. We demonstrate unexpected pro-neoplastic consequences of oral NaHCO3 therapy that in breast tissue cancel out previously reported anti-neoplastic effects.

Towards an Integral Therapeutic Protocol for Breast Cancer Based upon the New H+-Centered Anticancer Paradigm of the Late Post-Warburg Era

“…However, Na + , K + and BUN should be checked at least monthly during treatment. Unexpectedly, the alkalization of tumor pH and pHi with SB has shown cancer-promoting effects in BC tissues [ 361 ]. It is also paradoxical that the utilization of sodium bicarbonate, at least in certain circumstances, may lead to intracellular acidosis, with this phenomenon being more evident at higher starting intracellular pHs [ 362 ].…”

PTPRG is an ischemia risk locus essential for HCO3–-dependent regulation of endothelial function and tissue perfusion

“…Evidence supports that cells also possess sensors that respond to changes in [HCO 3 -] in the intracellular and extracellular space (12)(13)(14). Interventions-such as NaHCO 3 supplementationthat modify systemic acid-base status are available (15) but expected to carry considerable adverse effects and be too general for cardiovascular therapy. The identification of HCO 3 --related proteins (e.g., carbonic anhydrases, Na + ,HCO 3 --cotransporters, Cl -/HCO 3 --exchangers, and HCO 3 --sensors) opens largely unexplored avenues for pharmacological treatment.…”

“…Evidence supports that cells also possess sensors that respond to changes in [HCO 3 – ] in the intracellular and extracellular space ( Zhou et al, 2016 ; Boedtkjer et al, 2016c ; Chen et al, 2000 ). Interventions—such as NaHCO 3 supplementation—that modify systemic acid-base status are available ( Voss et al, 2020 ) but expected to carry considerable adverse effects and be too general for cardiovascular therapy. The identification of HCO 3 – -related proteins (e.g.…”

Putting Warburg to work: how imaging of tumour acidosis could help predict metastatic potential in breast cancer

“…− administration have shown opposing effects on metastasis in different models. 16,17 Curiously, HCO 3…”