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Molecular machineries of pH dysregulation in tumor microenvironment: potential targets for cancer therapy.

ABSTRACT: Introduction: Cancer is an intricate disorder/dysfunction of cells that can be defined as a genetic heterogeneity in human disease. Therefore, it is characterized by several adaptive complex hallmarks. Among them, the pH dysregulation appears as a symbol of aberrant functions within the tumor microenvironment (TME). In comparison with normal tissues, in the solid tumors, we face with an irregular acidification and alkalinization of the extracellular and intracellular fluids. Methods: In this study, we comprehensively discussed the most recent reports on the hallmarks of solid tumors to provide deep insights upon the molecular machineries involved in the pH dysregulation of solid tumors and their impacts on the initiation and progression of cancer. Results: The dysregulation of pH in solid tumors is fundamentally related to the Warburg effect and hypoxia, leading to expression of a number of molecular machineries, including: NHE1, H+ pump V-ATPase, CA-9, CA-12, MCT-1, GLUT-1. Activation of proton exchangers and transporters (PETs) gives rise to formation of TME. This condition favors the cancer cells to evade from the anoikis and apoptosis, granting them aggressive and metastasis phenotype, as well as resistance to chemotherapy and radiation therapy. This review aimed to discuss the key molecular changes of tumor cells in terms of bio-energetics and cancer metabolism in relation with pH dysregulation. During this phenomenon, the intra- and extracellular metabolites are altered and/or disrupted. Such molecular alterations provide molecular hallmarks for direct targeting of the PETs by potent relevant inhibitors in combination with conventional cancer therapies as ultimate therapy against solid tumors. Conclusion: Taken all, along with other treatment strategies, targeting the key molecular machineries related to intra- and extracellular metabolisms within the TME is proposed as a novel strategy to inhibit or block PETs that are involved in the pH dysregulation of solid tumors.

SUBMITTER: Asgharzadeh MR

PROVIDER: S-EPMC5524986 | biostudies-other | 2017

REPOSITORIES: biostudies-other

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Molecular machineries of pH dysregulation in tumor microenvironment: potential targets for cancer therapy.

Asgharzadeh Mohammad Reza MR Barar Jaleh J Pourseif Mohammad M MM Eskandani Morteza M Jafari Niya Mojtaba M Mashayekhi Mohammad Reza MR Omidi Yadollah Y

BioImpacts : BI 20170607 2

Introduction: Cancer is an intricate disorder/dysfunction of cells that can be defined as a genetic heterogeneity in human disease. Therefore, it is characterized by several adaptive complex hallmarks. Among them, the pH dysregulation appears as a symbol of aberrant functions within the tumor microenvironment (TME). In comparison with normal tissues, in the solid tumors, we face with an irregular acidification and alkalinization of the extracellular and intracellular fluids. ...[more]

PMID: 28752076

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Project description:PurposeTo establish magnetic resonance (MR)-based molecular imaging paradigms for the noninvasive monitoring of extracellular pH (pHe) as a functional surrogate biomarker for metabolic changes induced by locoregional therapy of liver cancer.Experimental designThirty-two VX2 tumor-bearing New Zealand white rabbits underwent longitudinal imaging on clinical 3T-MRI and CT scanners before and up to 2 weeks after complete conventional transarterial chemoembolization (cTACE) using ethiodized oil (lipiodol) and doxorubicin. MR-spectroscopic imaging (MRSI) was employed for pHe mapping. Multiparametric MRI and CT were performed to quantify tumor enhancement, diffusion, and lipiodol coverage of the tumor posttherapy. In addition, incomplete cTACE with reduced chemoembolic doses was applied to mimic undertreatment and exploit pHe mapping to detect viable tumor residuals. Imaging findings were correlated with histopathologic markers indicative of metabolic state (HIF-1α, GLUT-1, and LAMP-2) and viability (proliferating cell nuclear antigen and terminal deoxynucleotidyl-transferase dUTP nick-end labeling).ResultsUntreated VX2 tumors demonstrated a significantly lower pHe (6.80 ± 0.09) than liver parenchyma (7.19 ± 0.03, P < 0.001). Upregulation of HIF-1α, GLUT-1, and LAMP-2 confirmed a hyperglycolytic tumor phenotype and acidosis. A gradual tumor pHe increase toward normalization similar to parenchyma was revealed within 2 weeks after complete cTACE, which correlated with decreasing detectability of metabolic markers. In contrast, pHe mapping after incomplete cTACE indicated both acidic viable residuals and increased tumor pHe of treated regions. Multimodal imaging revealed durable tumor devascularization immediately after complete cTACE, gradually increasing necrosis, and sustained lipiodol coverage of the tumor.ConclusionsMRSI-based pHe mapping can serve as a longitudinal monitoring tool for viable tumors. As most liver tumors are hyperglycolytic creating microenvironmental acidosis, therapy-induced normalization of tumor pHe may be used as a functional biomarker for positive therapeutic outcome.

Project description:Simple Summary Cholangiocarcinoma (CCA) is a chemotherapy-resistant cancer. Reportedly, combination chemotherapy that includes immune checkpoint inhibitors (ICIs) showed superior effects compared to conventional chemotherapy for the treatment of advanced CCA. Although the efficacy of ICIs is considered to be affected by the tumor immune microenvironment (TME), the genetic/epigenetic background associated with TME in CCA is unknown. Here, we find that downregulations of genes involved in antigen presentation are associated with a “non-inflamed” tumor; the downregulations are inversely correlated with their DNA methylation levels. All tumors in the “inflamed” group exhibited an upregulation/low-methylation pattern. In contrast, the majority of CCAs in the non-inflamed group represent a downregulation/high-methylation pattern in antigen-presenting machineries. In addition, unique gene mutations of CCA that should induce DNA methylation events, like those in IDH1/2, are exclusively observed in CCAs carrying a non-inflamed tumor phenotype. These results may prove to be a clue to develop novel biomarkers and combination therapies for the treatment of CCA using ICIs. Abstract Cholangiocarcinoma (CCA) is a refractory cancer; a majority of CCAs represents a non-inflamed tumor phenotype that should be resistant to treatment, including immune checkpoint inhibitors (ICIs). In this study, we aimed to understand the molecular characteristics associated with non-inflamed CCAs. The genetic/epigenetic status of 36 CCAs was obtained from the Cancer Genome Atlas (PanCancerAtlas). CCAs were classified based on immune class using hierarchical clustering analysis of gene expressions related to tumor-infiltrating lymphocytes. The associations between immune class and genetic/epigenetic events were analyzed. We found that the tumors with alterations in FGFR2 and IDH1/2 had a “non-inflamed” tumor phenotype. A significant association was observed between the non-inflamed group and the downregulation of genes involved in antigen presentation (p = 0.0015). The expression of antigen-presenting machineries was inversely correlated with their DNA methylation levels, where 33.3% of tumors had an upregulation/low-methylation pattern, and 66.7% of tumors had a downregulation/high-methylation pattern. All tumors in the “inflamed” group exhibited an upregulation/low-methylation pattern. In contrast, 24 of 30 tumors in the non-inflamed group represent the downregulation/high-methylation pattern (p = 0.0005). Methylation with downregulation of antigen-presenting machineries is associated with the “non-inflamed” tumor phenotype of CCAs. This evidence provides important insights for developing new strategies for treating CCA.

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Molecular machineries of pH dysregulation in tumor microenvironment: potential targets for cancer therapy.

Publications

Molecular machineries of pH dysregulation in tumor microenvironment: potential targets for cancer therapy.

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