International Journal of Molecular Sciences

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17 pages, 5195 KiB

Open AccessArticle

Roles of the Na⁺/H⁺ Exchanger Isoform 1 and Urokinase in Prostate Cancer Cell Migration and Invasion

by Xiuju Li, Benjamin Buckley, Konstantin Stoletov, Yang Jing, Marie Ranson, John D. Lewis, Mike Kelso and Larry Fliegel

Int. J. Mol. Sci. 2021, 22(24), 13263; https://doi.org/10.3390/ijms222413263 - 9 Dec 2021

Cited by 10 | Viewed by 2831

Abstract

Prostate cancer is a leading cause of cancer-associated deaths in men over 60 years of age. Most patients are killed by tumor metastasis. Recent evidence has implicated a role of the tumor microenvironment and urokinase plasminogen activator (uPA) in cancer cell migration, invasion, [...] Read more.

Prostate cancer is a leading cause of cancer-associated deaths in men over 60 years of age. Most patients are killed by tumor metastasis. Recent evidence has implicated a role of the tumor microenvironment and urokinase plasminogen activator (uPA) in cancer cell migration, invasion, and metastasis. Here, we examine the role of the Na⁺/H⁺ exchanger isoform 1 (NHE1) and uPA in DU 145 prostate cancer cell migration and colony formation. Knockout of NHE1 reduced cell migration. The effects of a series of novel NHE1/uPA hexamethylene-amiloride-based inhibitors with varying efficacy towards NHE1 and uPA were examined on prostate cancer cells. Inhibition of NHE1—alone, or with inhibitors combining NHE1 or uPA inhibition—generally did not prevent prostate cancer cell migration. However, uPA inhibition—but not NHE1 inhibition—prevented anchorage-dependent colony formation. Application of inhibitors at concentrations that only saturate uPA inhibition decreased tumor invasion in vivo. The results suggest that while knockout of NHE1 affects cell migration, these effects are not due to NHE1-dependent proton translocation. Additionally, while neither NHE1 nor uPA activity was critical in cell migration, only uPA activity appeared to be critical in anchorage-dependent colony formation of DU 145 prostate cancer cells and invasion in vivo. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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19 pages, 31762 KiB

Open AccessArticle

Pepsin Promotes Activation of Epidermal Growth Factor Receptor and Downstream Oncogenic Pathways, at Slightly Acidic and Neutral pH, in Exposed Hypopharyngeal Cells

by Panagiotis G. Doukas, Dimitra P. Vageli, Clarence T. Sasaki and Benjamin L. Judson

Int. J. Mol. Sci. 2021, 22(8), 4275; https://doi.org/10.3390/ijms22084275 - 20 Apr 2021

Cited by 19 | Viewed by 3483

Abstract

Pepsin refluxate is considered a risk factor for laryngopharyngeal carcinogenesis. Non-acidic pepsin was previously linked to an inflammatory and tumorigenic effect on laryngopharyngeal cells in vitro. Yet there is no clear evidence of the pepsin-effect on a specific oncogenic pathway and the importance [...] Read more.

Pepsin refluxate is considered a risk factor for laryngopharyngeal carcinogenesis. Non-acidic pepsin was previously linked to an inflammatory and tumorigenic effect on laryngopharyngeal cells in vitro. Yet there is no clear evidence of the pepsin-effect on a specific oncogenic pathway and the importance of pH in this process. We hypothesized that less acidic pepsin triggers the activation of a specific oncogenic factor and related-signalling pathway. To explore the pepsin-effect in vitro, we performed intermittent exposure of 15 min, once per day, for a 5-day period, of human hypopharyngeal primary cells (HCs) to pepsin (1 mg/mL), at a weakly acidic pH of 5.0, a slightly acidic pH of 6.0, and a neutral pH of 7.0. We have documented that the extracellular environment at pH 6.0, and particularly pH 7.0, vs. pH 5.0, promotes the pepsin-effect on HCs, causing increased internalized pepsin and cell viability, a pronounced activation of EGFR accompanied by NF-κB and STAT3 activation, and a significant upregulation of EGFR, AKT1, mTOR, IL1β, TNF-α, RELA(p65), BCL-2, IL6 and STAT3. We herein provide new evidence of the pepsin-effect on oncogenic EGFR activation and its related-signaling pathway at neutral and slightly acidic pH in HCs, opening a window to further explore the prevention and therapeutic approach of laryngopharyngeal reflux disease. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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13 pages, 2481 KiB

Open AccessArticle

Screening of 5- and 6-Substituted Amiloride Libraries Identifies Dual-uPA/NHE1 Active and Single Target-Selective Inhibitors

by Benjamin J. Buckley, Ashna Kumar, Ashraf Aboelela, Richard S. Bujaroski, Xiuju Li, Hiwa Majed, Larry Fliegel, Marie Ranson and Michael J. Kelso

Int. J. Mol. Sci. 2021, 22(6), 2999; https://doi.org/10.3390/ijms22062999 - 15 Mar 2021

Cited by 16 | Viewed by 2996

Abstract

The K⁺-sparing diuretic amiloride shows off-target anti-cancer effects in multiple rodent models. These effects arise from the inhibition of two distinct cancer targets: the trypsin-like serine protease urokinase-type plasminogen activator (uPA), a cell-surface mediator of matrix degradation and tumor cell invasiveness, [...] Read more.

The K⁺-sparing diuretic amiloride shows off-target anti-cancer effects in multiple rodent models. These effects arise from the inhibition of two distinct cancer targets: the trypsin-like serine protease urokinase-type plasminogen activator (uPA), a cell-surface mediator of matrix degradation and tumor cell invasiveness, and the sodium-hydrogen exchanger isoform-1 (NHE1), a central regulator of transmembrane pH that supports carcinogenic progression. In this study, we co-screened our library of 5- and 6-substituted amilorides against these two targets, aiming to identify single-target selective and dual-targeting inhibitors for use as complementary pharmacological probes. Closely related analogs substituted at the 6-position with pyrimidines were identified as dual-targeting (pyrimidine 24 uPA IC₅₀ = 175 nM, NHE1 IC₅₀ = 266 nM, uPA selectivity ratio = 1.5) and uPA-selective (methoxypyrimidine 26 uPA IC₅₀ = 86 nM, NHE1 IC₅₀ = 12,290 nM, uPA selectivity ratio = 143) inhibitors, while high NHE1 potency and selectivity was seen with 5-morpholino (29 NHE1 IC₅₀ = 129 nM, uPA IC₅₀ = 10,949 nM; NHE1 selectivity ratio = 85) and 5-(1,4-oxazepine) (30 NHE1 IC₅₀ = 85 nM, uPA IC₅₀ = 5715 nM; NHE1 selectivity ratio = 67) analogs. Together, these amilorides comprise a new toolkit of chemotype-matched, non-cytotoxic probes for dissecting the pharmacological effects of selective uPA and NHE1 inhibition versus dual-uPA/NHE1 inhibition. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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13 pages, 3958 KiB

Open AccessArticle

Integrin-Linked Kinase Links Integrin Activation to Invadopodia Function and Invasion via the p(T567)-Ezrin/NHERF1/NHE1 Pathway

by Maria Raffaella Greco, Loredana Moro, Stefania Forciniti, Khalid Alfarouk, Stefania Cannone, Rosa Angela Cardone and Stephan Joel Reshkin

Int. J. Mol. Sci. 2021, 22(4), 2162; https://doi.org/10.3390/ijms22042162 - 22 Feb 2021

Cited by 12 | Viewed by 2652

Abstract

Tumor cell invasion depends largely on degradation of the extracellular matrix (ECM) by protease-rich structures called invadopodia, whose formation and activity requires the convergence of signaling pathways engaged in cell adhesion, actin assembly, membrane regulation and ECM proteolysis. It is known that β1-integrin [...] Read more.

Tumor cell invasion depends largely on degradation of the extracellular matrix (ECM) by protease-rich structures called invadopodia, whose formation and activity requires the convergence of signaling pathways engaged in cell adhesion, actin assembly, membrane regulation and ECM proteolysis. It is known that β1-integrin stimulates invadopodia function through an invadopodial p(T567)-ezrin/NHERF1/NHE1 signal complex that regulates NHE1-driven invadopodia proteolytic activity and invasion. However, the link between β1-integrin and this signaling complex is unknown. In this study, in metastatic breast (MDA-MB-231) and prostate (PC-3) cancer cells, we report that integrin-linked kinase (ILK) integrates β1-integrin with this signaling complex to regulate invadopodia activity and invasion. Proximity ligation assay experiments demonstrate that, in invadopodia, ILK associates with β1-integrin, NHE1 and the scaffold proteins p(T567)-ezrin and NHERF1. Activation of β1-integrin increased both invasion and invadopodia activity, which were specifically blocked by inhibition of either NHE1 or ILK. We conclude that ILK integrates β1-integrin with the ECM proteolytic/invasion signal module to induce NHE1-driven invadopodial ECM proteolysis and cell invasion. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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Review

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17 pages, 1167 KiB

Open AccessReview

Proton Transport in Cancer Cells: The Role of Carbonic Anhydrases

by Holger M. Becker and Joachim W. Deitmer

Int. J. Mol. Sci. 2021, 22(6), 3171; https://doi.org/10.3390/ijms22063171 - 20 Mar 2021

Cited by 21 | Viewed by 5248

Abstract

Intra- and extracellular pH regulation is a pivotal function of all cells and tissues. Net outward transport of H⁺ is a prerequisite for normal physiological function, since a number of intracellular processes, such as metabolism and energy supply, produce acid. In tumor [...] Read more.

Intra- and extracellular pH regulation is a pivotal function of all cells and tissues. Net outward transport of H⁺ is a prerequisite for normal physiological function, since a number of intracellular processes, such as metabolism and energy supply, produce acid. In tumor tissues, distorted pH regulation results in extracellular acidification and the formation of a hostile environment in which cancer cells can outcompete healthy local host cells. Cancer cells employ a variety of H⁺/HCO₃⁻-coupled transporters in combination with intra- and extracellular carbonic anhydrase (CA) isoforms, to alter intra- and extracellular pH to values that promote tumor progression. Many of the transporters could closely associate to CAs, to form a protein complex coined “transport metabolon”. While transport metabolons built with HCO₃⁻-coupled transporters require CA catalytic activity, transport metabolons with monocarboxylate transporters (MCTs) operate independently from CA catalytic function. In this article, we assess some of the processes and functions of CAs for tumor pH regulation and discuss the role of intra- and extracellular pH regulation for cancer pathogenesis and therapeutic intervention. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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14 pages, 1076 KiB

Open AccessReview

Lactic Acid and an Acidic Tumor Microenvironment suppress Anticancer Immunity

by Joy X. Wang, Stephen Y.C. Choi, Xiaojia Niu, Ning Kang, Hui Xue, James Killam and Yuzhuo Wang

Int. J. Mol. Sci. 2020, 21(21), 8363; https://doi.org/10.3390/ijms21218363 - 7 Nov 2020

Cited by 210 | Viewed by 11637

Abstract

Immune evasion and altered metabolism, where glucose utilization is diverted to increased lactic acid production, are two fundamental hallmarks of cancer. Although lactic acid has long been considered a waste product of this alteration, it is now well accepted that increased lactic acid [...] Read more.

Immune evasion and altered metabolism, where glucose utilization is diverted to increased lactic acid production, are two fundamental hallmarks of cancer. Although lactic acid has long been considered a waste product of this alteration, it is now well accepted that increased lactic acid production and the resultant acidification of the tumor microenvironment (TME) promotes multiple critical oncogenic processes including angiogenesis, tissue invasion/metastasis, and drug resistance. We and others have hypothesized that excess lactic acid in the TME is responsible for suppressing anticancer immunity. Recent studies support this hypothesis and provide mechanistic evidence explaining how lactic acid and the acidic TME impede immune cell functions. In this review, we consider lactic acid’s role as a critical immunoregulatory molecule involved in suppressing immune effector cell proliferation and inducing immune cell de-differentiation. This results in the inhibition of antitumor immune responses and the activation of potent, negative regulators of innate and adaptive immune cells. We also consider the role of an acidic TME in suppressing anticancer immunity. Finally, we provide insights to help translate this new knowledge into impactful anticancer immune therapies. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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38 pages, 1204 KiB

Open AccessReview

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

by Salvador Harguindey, Khalid Alfarouk, Julián Polo Orozco, Stefano Fais and Jesús Devesa

Int. J. Mol. Sci. 2020, 21(20), 7475; https://doi.org/10.3390/ijms21207475 - 10 Oct 2020

Cited by 5 | Viewed by 4781

Abstract

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H [...] Read more.

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H⁺) dynamics of cancer, allows for the understanding and integration of the many dualisms, confusions, and paradoxes of the disease. The new H⁺-related, wide-ranging model can embrace, from a unique perspective, the many aspects of the disease and, at the same time, therapeutically interfere with most, if not all, of the hallmarks of cancer known to date. The pH-related armamentarium available for the treatment of BC reviewed here may be beneficial for all types and stages of the disease. In this vein, we have attempted a megasynthesis of traditional and new knowledge in the different areas of breast cancer research and treatment based upon the wide-ranging approach afforded by the hydrogen ion dynamics of cancer. The concerted utilization of the pH-related drugs that are available nowadays for the treatment of breast cancer is advanced. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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Other

Jump to: Research, Review

36 pages, 4413 KiB

Open AccessCase Report

Targeting the pH Paradigm at the Bedside: A Practical Approach

by Tomas Koltai

Int. J. Mol. Sci. 2020, 21(23), 9221; https://doi.org/10.3390/ijms21239221 - 3 Dec 2020

Cited by 14 | Viewed by 3484

Abstract

The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but [...] Read more.

The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but rather an essential process in the physiopathology of accelerated proliferation and invasion. From the over-simplification of increased lactate production as the cause of the paradigm, as initially proposed, basic science researchers have arrived at highly complex and far-reaching knowledge, that substantially modified that initial belief. These new developments show that the paradigm entails a different regulation of membrane transporters, electrolyte exchangers, cellular and membrane enzymes, water trafficking, specialized membrane structures, transcription factors, and metabolic changes that go far beyond fermentative glycolysis. This complex world of dysregulations is still shuttered behind the walls of experimental laboratories and has not yet reached bedside medicine. However, there are many known pharmaceuticals and nutraceuticals that are capable of targeting the pH paradigm. Most of these products are well known, have low toxicity, and are also inexpensive. They need to be repurposed, and this would entail shorter clinical studies and enormous cost savings if we compare them with the time and expense required for the development of a new molecule. Will targeting the pH paradigm solve the “cancer problem”? Absolutely not. However, reversing the pH inversion would strongly enhance standard treatments, rendering them more efficient, and in some cases permitting lower doses of toxic drugs. This article’s goal is to describe how to reverse the pH gradient inversion with existing drugs and nutraceuticals that can easily be used in bedside medicine, without adding toxicity to established treatments. It also aims at increasing awareness among practicing physicians that targeting the pH paradigm would be able to improve the results of standard therapies. Some clinical cases will be presented as well, showing how the pH gradient inversion can be treated at the bedside in a simple manner with repurposed drugs. Full article

(This article belongs to the Special Issue Role of Dysregulation of pH in Cancer)

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