The Na(+)/HCO3(-) Co-Transporter SLC4A4 Plays a Role in Growth and Migration of Colon and Breast Cancer Cells

Solute carrier family 4 member 4 (SLC4A4) is associated with cell proliferation, migration and immune cell infiltration in colon cancer

BACKGROUND

Solute Carrier Family 4 Member 4 (SLC4A4) is a membrane protein-coding gene for a Na+/HCO3- cotransporter and plays a crucial role in regulating pH, bicarbonate secretion and homeostasis. However, the prognostic and immunological role of SLC4A4 in colon cancer remains unknown.

METHOD

In this study, expression profiles of SLC4A4 were retrieved from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, to which a variety of bioinformatic analyses were performed. Sangerbox, Xiantao, ESTIMATE and TIMER online tools were used to delve into the relationship between SLC4A4 expression and immune cell infiltration. The role of SLC4A4 in the proliferation and migration of colon cancer cells was verified by CCK8, EdU and wound healing assays. The related molecules and pathways that SLC4A4 may affect were validated by bioinformatic prediction and western blotting analysis.

RESULTS

The expression levels of SLC4A4 were significantly lower in colon cancer tissues than in normal tissues and its low expression was positively correlated with poor prognosis. TIMER and ESTIMATE showed that SLC4A4 broadly influenced immune cell infiltration. Experiments in vitro demonstrated that SLC4A4 inhibited partial epithelial-mesenchymal transition (EMT) phenotypes.

CONCLUSIONS

To conclude, our study revealed that SLC4A4 is lowly expressed in colon cancer tissues, and SLC4A4 may inhibit the progression of colon cancer via regulating partial EMT phenotypes and immune cell infiltration, which may provide new perspectives for the development of more precise and personalized immune anti-tumor therapies.

Intracellular pH differentially regulates transcription of metabolic and signaling pathways in normal epithelial cells

Intracellular pH (pHi) dynamics regulate normal cell function, and dysregulated pHi dynamics is an emerging hallmark of cancer (constitutively increased pHi) and neurodegeneration (constitutively decreased pHi). However, the molecular mechanisms by which pHi dynamics regulate cell biology are poorly understood. Here, we discovered that altering pHi in normal human breast epithelial cells triggers global transcriptional changes. We identified 176 genes differentially regulated by pHi, with pHi-dependent genes clustering in signaling and glycolytic pathways. Using various normal epithelial cell models, we showed pH-dependent Notch homolog 1 protein expression, with increased protein abundance at high pHi. This resulted in pH-dependent downstream signaling, with increased Notch homolog 1 signaling at high pHi. We also found that high pHi increased the expression of glycolytic enzymes and regulators of pyruvate fate, including lactate dehydrogenase and pyruvate dehydrogenase kinase. These transcriptional changes were sufficient to alter lactate production, with high pHi shifting these normal epithelial cells toward a glycolytic metabolism and increasing lactate production. Thus, pHi dynamics transcriptionally regulate signaling and metabolic pathways in normal epithelial cells. Our data reveal new molecular regulators of pHi-dependent biology and a role for increased pHi in driving the acquisition of cancer-associated signaling and metabolic changes in normal human epithelial cells.

SLC4A4 is a novel driver of enzalutamide resistance in prostate cancer

The androgen receptor signaling inhibitor (ARSI) enzalutamide (Enz) has shown critical efficacy in the treatment of advanced prostate cancer (PCa). However, the development of drug resistance is a significant factor contributing to mortality in PCa patients. We aimed to explore the key mechanisms of Enz-resistance. Through analysis of GEO databases, we identified SLC4A4 as a novel driver in Enz resistance. Long-term Enz treatment leads to the up-regulation of SLC4A4, which in turn mediates P53 lactylation via the NF-κB/STAT3/SLC4A4 axis, ultimately leading to the development of Enz resistance and progression of PCa. SLC4A4 knockdown overcomes Enz resistance both in vitro and in vivo. Hence, our results suggest that targeting SLC4A4 could be a promising therapeutic strategy for Enz resistance. STATEMENT OF SIGNIFICANCE: SLC4A4 is a novel driver of enzalutamide resistance.

Comparative genome-wide association study on body weight in Chinese native ducks using four models

The Jinling White duck represents a newly developed breed characterized by a rapid growth rate and a superior meat quality, offering significant economic value and research potential; however, the genetic basis underlying their body weight traits remains less understood. Here, we performed whole-genome resequencing for 201 diverse Jinling White male ducks and conducted population genomic analyses, suggesting a rich genetic diversity within the Jinling White duck population. Equipped with our genomic resources, we applied genome-wide association analysis for body weight on birth (BWB), body weight on 1 wk (BW1), body weight on 3 wk (BW3), body weight on 5 wk (BW5) and body weight on 7 wk (BW7) using 4 statistical models. Comparative studies indicated that factored spectrally transformed linear mixed models (FaST-LMM) demonstrated the most superior efficiency, yielding more results with the minimal false positives. We discovered that PUS7, FBXO11, FOXN2, MSH6, and SLC4A4 were associated with BWB. RAG2, and TMEFF2 were candidate genes for BW1, and STARD13, Klotho, ZAR1L are likely candidates for BW3 and BW5. PLXNC1, ATP1A1, CD58, FRYL, OCIAD1, and OCIAD2 were linked to BW7. These findings provide a genetic reference for the selection and breeding of Jinling White ducks, while also deepened our understanding of Growth and development phenotypic in ducks.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

CO2 exposure drives a rapid pH response in live adult Drosophila

CO2 anesthesia is the most common method for immobilizing Drosophila for research purposes. But CO2 exposure has consequences-it can impact fertility, behavior, morphogenesis, and cytoskeletal dynamics. In this respect, Drosophila is an outstanding model for studying the impact of CO2 exposure on tissues. In this study we explored the response of intracellular pH (pHi) to a one-minute CO2 pulse using a genetically encoded, ubiquitously expressed pH sensor, tpHusion, to monitor pHi within a live, intact, whole fly. We compared wild-type flies to flies lacking Imaginal disc growth factors (Idgfs), which are chitinase-like proteins that facilitate developmental processes and the innate immune response. Morphogenetic and cytoskeletal defects in Idgf-null flies are enhanced after CO2 exposure. We found that pHi drops sharply within seconds of the beginning of a CO2 pulse and recovers over several minutes. The initial profile was nearly identical in control and Idgf-null flies but diverged as the pHi returned to normal. This study demonstrates the feasibility of monitoring pH in live adult Drosophila. Studies exploring pH homeostasis are important for understanding human pathologies associated with pH dysregulation.

Targeting Pivotal Hallmarks of Cancer for Enhanced Therapeutic Strategies in Triple-Negative Breast Cancer Treatment-In Vitro, In Vivo and Clinical Trials Literature Review

This literature review provides a comprehensive overview of triple-negative breast cancer (TNBC) and explores innovative targeted therapies focused on specific hallmarks of cancer cells, aiming to revolutionize breast cancer treatment. TNBC, characterized by its lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), presents distinct features, categorizing these invasive breast tumors into various phenotypes delineated by key elements in molecular assays. This article delves into the latest advancements in therapeutic strategies targeting components of the tumor microenvironment and pivotal hallmarks of cancer: deregulating cellular metabolism and the Warburg effect, acidosis and hypoxia, the ability to metastasize and evade the immune system, aiming to enhance treatment efficacy while mitigating systemic toxicity. Insights from in vitro and in vivo studies and clinical trials underscore the promising effectiveness and elucidate the mechanisms of action of these novel therapeutic interventions for TNBC, particularly in cases refractory to conventional treatments. The integration of targeted therapies tailored to the molecular characteristics of TNBC holds significant potential for optimizing clinical outcomes and addressing the pressing need for more effective treatment options for this aggressive subtype of breast cancer.

1,25(OH)2 D3 inhibits Lewis lung cancer cell migration via NHE1-sensitive metabolic reprograming

High prevalence and metastasis rates are characteristics of lung cancer. Glycolysis provides energy for the development and metastasis of cancer cells. The 1,25-dihydroxy vitamin D3 (1,25(OH)2 D3 ) has been linked to reducing cancer risk and regulates various physiological functions. We hypothesized that 1,25(OH)2 D3 could be associated with the expression and activity of Na+ /H+ exchanger isoform 1 (NHE1) of Lewis lung cancer cells, thus regulating glycolysis as well as migration by actin reorganization. Followed by online public data analysis, Vitamin D3 receptor, the receptor of 1,25(OH)2 D3 has been proved to be abundant in lung cancers. We demonstrated that 1,25(OH)2 D3 treatment suppressed transcript levels, protein levels, and activity of NHE1 in LLC cells. Furthermore, 1,25(OH)2 D3 treatment resets the metabolic balance between glycolysis and OXPHOS, mainly including reducing glycolytic enzymes expression and lactate production. In vivo experiments showed the inhibition effects on tumor growth as well. Therefore, we concluded that 1,25(OH)2 D3 could amend the NHE1 function, which leads to metabolic reprogramming and cytoskeleton reconstruction, finally inhibits the cell migration.

The role of Na+-coupled bicarbonate transporters (NCBT) in health and disease

Cellular and organism survival depends upon the regulation of pH, which is regulated by highly specialized cell membrane transporters, the solute carriers (SLC) (For a comprehensive list of the solute carrier family members, see: https://www.bioparadigms.org/slc/ ). The SLC4 family of bicarbonate (HCO3-) transporters consists of ten members, sorted by their coupling to either sodium (NBCe1, NBCe2, NBCn1, NBCn2, NDCBE), chloride (AE1, AE2, AE3), or borate (BTR1). The ionic coupling of SLC4A9 (AE4) remains controversial. These SLC4 bicarbonate transporters may be controlled by cellular ionic gradients, cellular membrane voltage, and signaling molecules to maintain critical cellular and systemic pH (acid-base) balance. There are profound consequences when blood pH deviates even a small amount outside the normal range (7.35-7.45). Chiefly, Na+-coupled bicarbonate transporters (NCBT) control intracellular pH in nearly every living cell, maintaining the biological pH required for life. Additionally, NCBTs have important roles to regulate cell volume and maintain salt balance as well as absorption and secretion of acid-base equivalents. Due to their varied tissue expression, NCBTs have roles in pathophysiology, which become apparent in physiologic responses when their expression is reduced or genetically deleted. Variations in physiological pH are seen in a wide variety of conditions, from canonically acid-base related conditions to pathologies not necessarily associated with acid-base dysfunction such as cancer, glaucoma, or various neurological diseases. The membranous location of the SLC4 transporters as well as recent advances in discovering their structural biology makes them accessible and attractive as a druggable target in a disease context. The role of sodium-coupled bicarbonate transporters in such a large array of conditions illustrates the potential of treating a wide range of disease states by modifying function of these transporters, whether that be through inhibition or enhancement.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

Trafficking of carbonic anhydrase 12 and bicarbonate transporters by histamine stimulation mediates intracellular acidic scenario in lung cancer cells

Carbonic anhydrase 12 is considered an oncogenic and acidic microenvironmental factor in cancer cells. To verify the role of histamine signalling as an anti-cancer signal, we determined the roles of CA12 and its associated bicarbonate transporters. In this study, histamine stimulation mediated mislocalization of CA12 in lung cancer cells. Histamine receptor activation-mediated CA12 endocytosis and pH were restored by CaMKII inhibition. CA12-associated AE2 expression was enhanced, whereas NBCn1 expression and its activity were reduced by histamine stimulation. Histamine receptor activation-mediated acidification was induced by internalised CA12 and NBCn1 and, at the same time by increased bicarbonate efflux through enhanced AE2 expression. Inhibition of protein trafficking by bafilomycin restored CA12 and AE2 localisation and diminished cellular acidosis. Thus, we verified that histamine stimulation induced an acidic scenario, which revealed trafficking of CA12 and its associated bicarbonate transporters in lung cancer cells and its dysregulated pH modulation may be involved in the histamine signalling-mediated anti-cancer process.

Voltage-gated sodium channels, sodium transport and progression of solid tumours

Sodium (Na+) concentration in solid tumours of different origin is highly dysregulated, and this corresponds to the aberrant expression of Na+ transporters. In particular, the α subunits of voltage gated Na+ channels (VGSCs) raise intracellular Na+ concentration ([Na+]i) in malignant cells, which influences the progression of solid tumours, predominantly driving cancer cells towards a more aggressive and metastatic phenotype. Conversely, re-expression of VGSC β subunits in cancer cells can either enhance tumour progression or promote anti-tumourigenic properties. Metastasis is the leading cause of cancer-related mortality, highlighting an important area of research which urgently requires improved therapeutic interventions. Here, we review the extent to which VGSC subunits are dysregulated in solid tumours, and consider the implications of such dysregulation on solid tumour progression. We discuss current understanding of VGSC-dependent mechanisms underlying increased invasive and metastatic potential of solid tumours, and how the complex relationship between the tumour microenvironment (TME) and VGSC expression may further drive tumour progression, in part due to the interplay of infiltrating immune cells, cancer-associated fibroblasts (CAFs) and insufficient supply of oxygen (hypoxia). Finally, we explore past and present clinical trials that investigate utilising existing VGSC modulators as potential pharmacological options to support adjuvant chemotherapies to prevent cancer recurrence. Such research demonstrates an exciting opportunity to repurpose therapeutics in order to improve the disease-free survival of patients with aggressive solid tumours.

Effects of preoperative bicarbonate and lactate levels on short-term outcomes and prognosis in elderly patients with colorectal cancer

PURPOSE

The aim of this study was to analyze the effect of preoperative bicarbonate and lactate levels (LL) on the short-term outcomes and prognosis in elderly (≥ 65 years) patients with colorectal cancer (CRC).

METHODS

We collected the information of CRC patients from Jan 2011 to Jan 2020 in a single clinical center. According to the results of preoperative blood gas analysis, we divided patients into the higher/lower bicarbonate group and the higher/lower lactate group, and compared their baseline information, surgery-related information, overall survival (OS) and disease-free survival (DFS).

RESULTS

A total of 1473 patients were included in this study. Comparing the clinical data of the higher/lower bicarbonate group and the higher/lower lactate group, the lower group were older (p < 0.01), had higher rates of coronary heart disease (CHD) (p = 0.025), a higher proportion of colon tumors (p < 0.01), larger tumor size (p < 0.01), higher rates of open surgery (p < 0.01), more intraoperative blood loss (p < 0.01), higher overall complications (p < 0.01) and 30-day deaths (p < 0.01). The higher LL patients had more male patients (p < 0.01), higher body mass index (BMI) (p < 0.01) and drinking rates (p = 0.049), higher rates of type 2 diabetes mellitus (T2DM) (p < 0.01) and lower rates of open surgery (p < 0.01). In multivariate analysis, age (p < 0.01), BMI (p = 0.036), T2DM (p = 0.023), and surgical methods (p < 0.01) were independent risk factors of overall complications. The independent risk factors for OS included age (p < 0.01), tumor site (p = 0.014), tumor stage (p < 0.01), tumor size (p = 0.036), LL (p < 0.01), and overall complications (p < 0.01). The independent risk factors of DFS included age (p = 0.012), tumor site (p = 0.019), tumor stage (p < 0.01), LL (p < 0.01), and overall complications (p < 0.01).

CONCLUSION

Preoperative LL significantly affected postoperative OS and DFS of CRC patients, but bicarbonate might not affect the prognosis of CRC patients. Therefore, surgeons should actively focus on and adjust the LL of patients before surgery.

Targeting the bicarbonate transporter SLC4A4 overcomes immunosuppression and immunotherapy resistance in pancreatic cancer

Solid tumors are generally characterized by an acidic tumor microenvironment (TME) that favors cancer progression, therapy resistance and immune evasion. By single-cell RNA-sequencing analysis in individuals with pancreatic ductal adenocarcinoma (PDAC), we reveal solute carrier family 4 member 4 (SLC4A4) as the most abundant bicarbonate transporter, predominantly expressed by epithelial ductal cells. Functionally, SLC4A4 inhibition in PDAC cancer cells mitigates the acidosis of the TME due to bicarbonate accumulation in the extracellular space and a decrease in lactate production by cancer cells as the result of reduced glycolysis. In PDAC-bearing mice, genetic or pharmacological SLC4A4 targeting improves T cell-mediated immune response and breaches macrophage-mediated immunosuppression, thus inhibiting tumor growth and metastases. In addition, Slc4a4 targeting in combination with immune checkpoint blockade is able to overcome immunotherapy resistance and prolong survival. Overall, our data propose SLC4A4 as a therapeutic target to unleash an antitumor immune response in PDAC.

Single-cell transcriptomics reveals cell type diversity of human prostate

Extensive studies have been performed to describe the phenotypic changes occurring during malignant transformation of the prostate. However, the cell types and associated changes that contribute to the development of prostate diseases and cancer remain elusive, largely due to the heterogeneous composition of prostatic tissues. Here, we conduct a comprehensive evaluation of four human prostate tissues by single-cell RNA sequencing (scRNA-seq) to analyze their cellular compositions. We identify 18 clusters of cell types, each with distinct gene expression profiles and unique features; of these, one cluster of epithelial cells (Ep) is found to be associated with immune function. In addition, we characterize a special cluster of fibroblasts and aberrant signaling changes associated with prostate cancer (PCa). Moreover, we provide insights into the epithelial changes that occur during the cellular senescence and aging. These results expand our understanding of the unique functional associations between the diverse prostatic cell types and the contributions of specific cell clusters to the malignant transformation of prostate tissues and PCa development.

Cell-Type Dependent Regulation of the Electrogenic Na+/HCO3- Cotransporter 1 (NBCe1) by Hypoxia and Acidosis in Glioblastoma

Glioblastoma multiforme (GBM) is the most common and malignant brain tumour. It is characterised by transcriptionally distinct cell populations. In tumour cells, physiological pH gradients between the intracellular and extracellular compartments are reversed, compared to non-cancer cells. Intracellular pH in tumour cells is alkaline, whereas extracellular pH is acidic. Consequently, the function and/or expression of pH regulating transporters might be altered. Here, we investigated protein expression and regulation of the electrogenic sodium/bicarbonate cotransporter 1 (NBCe1) in mesenchymal (MES)-like hypoxia-dependent and -independent cells, as well as in astrocyte-like glioblastoma cells following chemical hypoxia, acidosis and elucidated putative underlying molecular pathways. Immunoblotting, immunocytochemistry, and intracellular pH recording with the H⁺-sensitive dye 2′,7′-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein were applied. The results show NBCe1 protein abundance and active NBCe1 transport. Hypoxia upregulated NBCe1 protein and activity in MES-like hypoxia-dependent GBM cells. This effect was positively correlated with HIF-1α protein levels, was mediated by TGF-β signalling, and was prevented by extracellular acidosis. In MES-like hypoxia-independent GBM cells, acidosis (but not hypoxia) regulated NBCe1 activity in an HIF-1α-independent manner. These results demonstrate a cell-specific adaptation of NBCe1 expression and activity to the microenvironment challenge of hypoxia and acidosis that depends on their transcriptional signature in GBM.

Dual-Mode Tumor Imaging Using Probes That Are Responsive to Hypoxia-Induced Pathological Conditions

Hypoxia in solid tumors is associated with poor prognosis, increased aggressiveness, and strong resistance to therapeutics, making accurate monitoring of hypoxia important. Several imaging modalities have been used to study hypoxia, but each modality has inherent limitations. The use of a second modality can compensate for the limitations and validate the results of any single imaging modality. In this review, we describe dual-mode imaging systems for the detection of hypoxia that have been reported since the start of the 21st century. First, we provide a brief overview of the hallmarks of hypoxia used for imaging and the imaging modalities used to detect hypoxia, including optical imaging, ultrasound imaging, photoacoustic imaging, single-photon emission tomography, X-ray computed tomography, positron emission tomography, Cerenkov radiation energy transfer imaging, magnetic resonance imaging, electron paramagnetic resonance imaging, magnetic particle imaging, and surface-enhanced Raman spectroscopy, and mass spectrometric imaging. These overviews are followed by examples of hypoxia-relevant imaging using a mixture of probes for complementary single-mode imaging techniques. Then, we describe dual-mode molecular switches that are responsive in multiple imaging modalities to at least one hypoxia-induced pathological change. Finally, we offer future perspectives toward dual-mode imaging of hypoxia and hypoxia-induced pathophysiological changes in tumor microenvironments.

Overcoming T cell dysfunction in acidic pH to enhance adoptive T cell transfer immunotherapy

The high metabolic activity and insufficient perfusion of tumors leads to the acidification of the tumor microenvironment (TME) that may inhibit the antitumor T cell activity. We found that pharmacological inhibition of the acid loader chloride/bicarbonate anion exchanger 2 (Ae2), with 4,4’-diisothiocyanatostilbene-2,2’-disulfonicacid (DIDS) enhancedCD4⁺ andCD8⁺ T cell function upon TCR activation in vitro, especially under low pH conditions. In vivo, DIDS administration delayed B16OVA tumor growth in immunocompetent mice as monotherapy or when combined with adoptive T cell transfer of OVA-specificT cells. Notably, genetic Ae2 silencing in OVA-specificT cells improvedCD4⁺/CD8⁺ T cell function in vitro as well as their antitumor activity in vivo. Similarly, genetic modification of OVA-specificT cells to overexpress Hvcn1, a selectiveH⁺ outward current mediator that prevents cell acidification, significantly improved T cell function in vitro, even at low pH conditions. The adoptive transfer of OVA-specificT cells overexpressing Hvcn1 exerted a better antitumor activity in B16OVA tumor-bearingmice. Hvcn1 overexpression also improved the antitumor activity of CAR T cells specific for Glypican 3 (GPC3) in mice bearing PM299L-GPC3tumors. Our results suggest that preventing intracellular acidification by regulating the expression of acidifier ion channels such as Ae2 or alkalinizer channels like Hvcn1 in tumor-specificlymphocytes enhances their antitumor response by making them more resistant to the acidic TME.

SLC4A4 promotes prostate cancer progression in vivo and in vitro via AKT-mediated signalling pathway

Background

Prostate cancer (PCa) is the second leading cause of cancer-related male deaths worldwide. The purpose of this study was to investigate the effects of homo sapiens solute carrier family 4 member 4 (SLC4A4), which encodes the electrogenic Na+/HCO3− cotransporter isoform 1 (NBCe1), in the development and progression of PCa.

Methods

The expression levels of SLC4A4 in PCa and normal prostate tissues were evaluated by immunohistochemistry. The SLC4A4 knockdown cell model was structured by lentiviral infection, and the knockdown efficiency was validated by RT-qPCR and Western blotting. The effects of SLC4A4 knockdown on cell proliferation, apoptosis and cycle, migration, and invasion were detected by Celigo cell counting assay and CCK-8 assay, flow cytometry analysis, wound-healing, and Transwell assay, respectively. Tumor growth in nude mice was surveyed by in vivo imaging and Ki-67 staining. Furthermore, underlying mechanism of SLC4A4 silence induced inhibition of PCa progression was explored by human phospho-kinase array.

Results

Our results revealed that SLC4A4 expression was up-regulated in PCa tissues and human PCa cell lines. High expression of SLC4A4 in tumor specimens was significantly correlated with disease progression. SLC4A4 knockdown inhibited cell proliferation, migration and invasion, while facilitated apoptosis, which was also confirmed in vivo. Moreover, SLC4A4 promoted PCa progression through the AKT-mediated signalling pathway.

Conclusion

The results of this study indicated that SLC4A4 overexpression was closely associated with the progression of PCa; SLC4A4 knockdown suppressed PCa development in vitro and in vivo. SLC4A4 acts as a tumor promotor in PCa by regulating key components of the AKT pathway and may therefore act as a potential therapeutic target for PCa treatment.

Targeting hypoxia regulated sodium driven bicarbonate transporters reduces triple negative breast cancer metastasis

Regions of low oxygen (hypoxia) are found in >50% of breast tumours, most frequently in the more aggressive triple negative breast cancer subtype (TNBC). Metastasis is the cause of 90% of breast cancer patient deaths. Regions of tumour hypoxia tend to be more acidic and both hypoxia and acidosis increase tumour metastasis. In line with this the metastatic process is dependent on pH regulatory mechanisms. We and others have previously identified increased hypoxic expression of Na+ driven bicarbonate transporters (NDBTs) as a major mechanism of tumour pH regulation. Hypoxia induced the expression of NDBTs in TNBC, most frequently SLC4A4 and SLC4A5. NDBT inhibition (S0859) and shRNA knockdown suppressed migration (40% reduction) and invasion (70% reduction) in vitro. Tumour xenograft metastasis in vivo was significantly reduced by NDBT knockdown. To investigate the mechanism by which NDBTs support metastasis, we investigated their role in regulation of phospho-signalling, epithelial-to-mesenchymal transition (EMT) and metabolism. NDBT knockdown resulted in an attenuation in hypoxic phospho-signalling activation; most notably LYN (Y397) reduced by 75%, and LCK (Y394) by 72%. The metastatic process is associated with EMT. We showed that NDBT knockdown inhibited EMT, modulating the expression of key EMT transcription factors and ablating the expression of vimentin whilst increasing the expression of E-cadherin. NDBT knockdown also altered metabolic activity reducing overall ATP and extracellular lactate levels. These results demonstrate that targeting hypoxia-induced NDBT can be used as an approach to modulate phospho-signalling, EMT, and metabolic activity and reduce tumour migration, invasion, and metastasis in vivo.

Contribution of the Mitochondrial Carbonic Anhydrase (MoCA1) to Conidiogenesis and Pathogenesis in Magnaporthe oryzae

The interconversion of CO₂ and HCO₃⁻ catalyzed by carbonic anhydrases (CAs) is a fundamental biochemical process in organisms. During mammalian–pathogen interaction, both host and pathogen CAs play vital roles in resistance and pathogenesis; during planta–pathogen interaction, however, plant CAs function in host resistance but whether pathogen CAs are involved in pathogenesis is unknown. Here, we biologically characterized the Magnaporthe oryzae CA (MoCA1). Through detecting the DsRED-tagged proteins, we observed the fusion MoCA1 in the mitochondria of M. oryzae. Together with the measurement of CA activity, we confirmed that MoCA1 is a mitochondrial zinc-binding CA. MoCA1 expression, upregulated with H₂O₂ or NaHCO₃ treatment, also showed a drastic upregulation during conidiogenesis and pathogenesis. When MoCA1 was deleted, the mutant ΔMoCA1 was defective in conidiophore development and pathogenicity. 3,3′-Diaminobenzidine (DAB) staining indicated that more H₂O₂ accumulated in ΔMoCA1; accordingly, ATPase genes were downregulated and ATP content decreased in ΔMoCA1. Summarily, our data proved the involvement of the mitochondrial MoCA1 in conidiogenesis and pathogenesis in the rice blast fungus. Considering the previously reported HCO₃⁻ transporter MoAE4, we propose that MoCA1 in cooperation with MoAE4 constitutes a HCO₃⁻ homeostasis-mediated disease pathway, in which MoCA1 and MoAE4 can be a drug target for disease control.

Multifaceted Interplay between Hormones, Growth Factors and Hypoxia in the Tumor Microenvironment

Hormones and growth factors (GFs) are signaling molecules implicated in the regulation of a variety of cellular processes. They play important roles in both healthy and tumor cells, where they function by binding to specific receptors on target cells and activating downstream signaling cascades. The stages of tumor progression are influenced by hormones and GF signaling. Hypoxia, a hallmark of cancer progression, contributes to tumor plasticity and heterogeneity. Most solid tumors contain a hypoxic core due to rapid cellular proliferation that outgrows the blood supply. In these circumstances, hypoxia-inducible factors (HIFs) play a central role in the adaptation of tumor cells to their new environment, dramatically reshaping their transcriptional profile. HIF signaling is modulated by a variety of factors including hormones and GFs, which activate signaling pathways that enhance tumor growth and metastatic potential and impair responses to therapy. In this review, we summarize the role of hormones and GFs during cancer onset and progression with a particular focus on hypoxia and the interplay with HIF proteins. We also discuss how hypoxia influences the efficacy of cancer immunotherapy, considering that a hypoxic environment may act as a determinant of the immune-excluded phenotype and a major hindrance to the success of adoptive cell therapies.

Energy Metabolism and Intracellular pH Alteration in Neural Spheroids Carrying Down Syndrome

Brain diseases including Down syndrome (DS/TS21) are known to be characterized by changes in cellular metabolism. To adequately assess such metabolic changes during pathological processes and to test drugs, methods are needed that allow monitoring of these changes in real time with minimally invasive effects. Thus, the aim of our work was to study the metabolic status and intracellular pH of spheroids carrying DS using fluorescence microscopy and FLIM. For metabolic analysis we measured the fluorescence intensities, fluorescence lifetimes and the contributions of the free and bound forms of NAD(P)H. For intracellular pH assay we measured the fluorescence intensities of SypHer-2 and BCECF. Data were processed with SPCImage and Fiji-ImageJ. We demonstrated the predominance of glycolysis in TS21 spheroids compared with normal karyotype (NK) spheroids. Assessment of the intracellular pH indicated a more alkaline intracellular pH in the TS21 spheroids compared to NK spheroids. Using fluorescence imaging, we performed a comprehensive comparative analysis of the metabolism and intracellular pH of TS21 spheroids and showed that fluorescence microscopy and FLIM make it possible to study living cells in 3D models in real time with minimally invasive effects.

Electrogenic sodium bicarbonate cotransporter NBCe1 regulates pancreatic β cell function in type 2 diabetes

Pancreatic β cell failure in type 2 diabetes mellitus (T2DM) is attributed to perturbations of the β cell's transcriptional landscape resulting in impaired glucose-stimulated insulin secretion. Recent studies identified SLC4A4 (a gene encoding an electrogenic Na+-coupled HCO3- cotransporter and intracellular pH regulator, NBCe1) as one of the misexpressed genes in β cells of patients with T2DM. Thus, in the current study, we set out to test the hypothesis that misexpression of SLC4A4/NBCe1 in T2DM β cells contributes to β cell dysfunction and impaired glucose homeostasis. To address this hypothesis, we first confirmed induction of SLC4A4/NBCe1 expression in β cells of patients with T2DM and demonstrated that its expression was associated with loss of β cell transcriptional identity, intracellular alkalinization, and β cell dysfunction. In addition, we generated a β cell-selective Slc4a4/NBCe1-KO mouse model and found that these mice were protected from diet-induced metabolic stress and β cell dysfunction. Importantly, improved glucose tolerance and enhanced β cell function in Slc4a4/NBCe1-deficient mice were due to augmented mitochondrial function and increased expression of genes regulating β cell identity and function. These results suggest that increased β cell expression of SLC4A4/NBCe1 in T2DM plays a contributory role in promotion of β cell failure and should be considered as a potential therapeutic target.

SLC34A2 Up-regulation And SLC4A4 Down-regulation Correlates With Invasion, Metastasis, And The MAPK Signaling Pathway In Papillary Thyroid Carcinomas

Papillary thyroid carcinoma (PTC) is one of the fastest growing endocrine system malignant carcinomas detected over the past decade. Unfortunately, more than 25% of PTC patients are characterized by their aggressiveness and subsequent metastasis; these characteristics usually indicate poor prognosis. Recently, increasing evidence has suggested that solute carrier (SLC) transporters may play a pivotal role in the initiation, invasion and metastasis of human carcinoma. However, the expression and clinicopathological significance of SLC transporters in patients with PTC remains undetermined. In this study, we aimed to elucidate how the differential expression of SLC transporters affects clinicopathological features, as well as determine the possible regulatory signaling pathways involved. Three differentially expressed SLC transporters were screened from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) database using a bioinformatics approach. The results indicated that high SLC34A2 and low SLC4A4 protein expression exhibited a higher percentage of capsular invasion and extra-thyroid metastasis in patients. Logistic regression analysis showed that high SLC34A2 expression in tumors was identified as an independent risk factor for capsular invasion [odds ratio (OR)=11.400, 95% confidence interval (CI)=1.733-74.995, P=0.011] and extra-thyroid metastasis (OR=4.920, 95%CI=1.234-19.623, P=0.024), while low SLC4A4 expression in tumors was only identified as independent risk factors for extra-thyroid metastasis (OR=8.568, 95%CI =1.186-61.906, P=0.033). Specifically, for tumors with capsular invasion and extra-thyroid metastasis, the protein expression staining of SLC34A2 was markedly enhanced in the cytoplasm of follicular epithelial cells, contrastingly, SLC4A4 expression was notably weakened in the cytomembrane and nucleus. Intriguingly, both high SLC34A2 and low SLC4A4 protein expression were significantly linked to a high urinary iodine concentration in patients with PTC. Mechanistically, compared with adjacent normal thyroids, p-ERK was significantly up-regulated by 17.8% in the invading tumor; p-ERK, p-JNK, and p-P38 were markedly up-regulated by 29.2%, 67.1%, and 38.9% for metastatic tumors, respectively. Importantly, SLC4A4 negatively correlated with p-JNK (r=-0.696, P= 0.004) and p-P38 (r=-0.534, P=0.049). In conclusion, we suggest that up-regulated SLC34A2 (mainly in the cytoplasm) and down-regulated SLC4A4 (mainly in the cytomembrane and nucleus), which might be attributed to excess iodine intake, were closely linked to extra-thyroid metastasis in PTCs. Furthermore, this effect of SLC4A4 may be through the activation of JNK/P38 MAPK signaling pathway. Future in vivo and in vitro gain- or loss-of-function experiments are needed to verify these findings and further elucidate the deeper molecular mechanisms.

Ion Channels, Transporters, and Sensors Interact with the Acidic Tumor Microenvironment to Modify Cancer Progression

Solid tumors, including breast carcinomas, are heterogeneous but typically characterized by elevated cellular turnover and metabolism, diffusion limitations based on the complex tumor architecture, and abnormal intra- and extracellular ion compositions particularly as regards acid-base equivalents. Carcinogenesis-related alterations in expression and function of ion channels and transporters, cellular energy levels, and organellar H⁺ sequestration further modify the acid-base composition within tumors and influence cancer cell functions, including cell proliferation, migration, and survival. Cancer cells defend their cytosolic pH and HCO₃^- concentrations better than normal cells when challenged with the marked deviations in extracellular H⁺, HCO₃^-, and lactate concentrations typical of the tumor microenvironment. Ionic gradients determine the driving forces for ion transporters and channels and influence the membrane potential. Cancer and stromal cells also sense abnormal ion concentrations via intra- and extracellular receptors that modify cancer progression and prognosis. With emphasis on breast cancer, the current review first addresses the altered ion composition and the changes in expression and functional activity of ion channels and transporters in solid cancer tissue. It then discusses how ion channels, transporters, and cellular sensors under influence of the acidic tumor microenvironment shape cancer development and progression and affect the potential of cancer therapies.

Extracellular vesicles derived from cancer-associated fibroblast carries miR-224-5p targeting SLC4A4 to promote the proliferation, invasion and migration of colorectal cancer cells

More and more studies indicated that extracellular vesicles (EVs) carrying miRNAs have been potential biomarkers of various cancers including colorectal cancer (CRC). This study aims to explore the function of miR-224-5p carried by EVs derived from cancer-associated fibroblasts (CAFs) in CRC. Here, we found that miR-224-5p was highly expressed while SLC4A4 was lowly expressed in CRC cells. Moreover, dual-luciferase reporter gene assay testified that miR-224-5p targeted SLC4A4. The expression of miR-224-5p in CAFs-derived EVs was found to be elevated. It was also testified that CAFs-derived EVs could transfer miR-224-5p into CRC cells. miR-224-5p in CAFs-derived EVs facilitated the proliferation, migration, invasion and anti-apoptosis of CRC cells. Overexpressing miR-224-5p increased the proliferative, migratory and invasive abilities of CRC cells and inhibit CRC cell apoptosis, while overexpressing SLC4A4 caused the opposite result. Research in vitro and in vivo further indicated that miR-224-5p promoted CRC cell progression via binding to its downstream target gene SLC4A4. Rescue assay also demonstrated that overexpressing miR-224-5p reversed the inhibitory effect of overexpressed SLC4A4 on cancer cell growth. In addition, in vivo assay identified that high level of miR-224-5p promoted the growth of cancer cells in mice in vivo. In conclusion, we explored the effect of miR-224-5p in CRC, which helps for further exploration of new methods for CRC targeted therapy.

Sodium bicarbonate transporter NBCe1 regulates proliferation and viability of human prostate cancer cells LNCaP and PC3

Studies on cultured cancer cells or cell lines have revealed multiple acid extrusion mechanisms and their involvement in cancer cell growth and progression. In the present study, the role of the sodium bicarbonate transporters (NBCs) in prostate cancer cell proliferation and viability was examined. qPCR revealed heterogeneous expression of five NBC isoforms in human prostate cancer cell lines LNCaP, PC3, 22RV1, C4-2, DU145, and the prostate cell line RWPE-1. In fluorescence pH measurement of LNCaP cells, which predominantly express NBCe1, Na⁺ and HCO₃^–-mediated acid extrusion was identified by bath ion replacement and sensitivity to the NBC inhibitor S0859. NBCe1 knockdown using siRNA oligonucleotides decreased the number of viable cells, and pharmacological inhibition with S0859 (50 µM) resulted in a similar decrease. NBCe1 knockdown and inhibition also increased cell death, but this effect was small and slow. In PC3 cells, which express all NBC isoforms, NBCe1 knockdown decreased viable cell number and increased cell death. The effects of NBCe1 knockdown were comparable to those by S0859, indicating that NBCe1 among NBCs primarily contributes to PC3 cell proliferation and viability. S0859 inhibition also decreased the formation of cell spheres in 3D cultures. Immunohistochemistry of human prostate cancer tissue microarrays revealed NBCe1 localization to the glandular epithelial cells in prostate tissue and robust expression in acinar and duct adenocarcinoma. In conclusion, our study demonstrates that NBCe1 regulates acid extrusion in prostate cancer cells and inhibiting or abolishing this transporter decreases cancer cell proliferation.

Malignant Evaluation and Clinical Prognostic Values of M6A RNA Methylation Regulators in Prostate Cancer

Objective: M6A RNA modification is closely associated with tumor genesis and progression of several malignancies; however, its role in prostate cancer (PCa) remains poorly understood.

Materials and methods: Expression data and corresponding clinicopathologic information were available freely from the Cancer Genome Atlas (TCGA) dataset. We compared the expression level of m6A RNA methylation regulators in PCa with different clinicopathologic characteristics and identified subgroups based on their expressions with consensus clustering. To build the signature and assess its prognostic value, several methods were used for the analysis, including univariate Cox regression analysis, Least Absolute Shrinkage and Selection Operator (LASSO) regression analysis, time-dependent receiver operating curve (ROC), and Kaplan-Meier (KM) survival analysis.

Results: Most of the m6A RNA methylation regulators were differentially expressed not only between normal and tumor tissue but also among PCa stratified by different clinicopathologic characteristics. There were obvious differences between two clusters, cluster 1 and 2, regarding clinicopathologic features, and the recurrence-free survival (RFS) in cluster 2 was significantly worse than cluster 1. We developed an eleven-gene signature which exhibited a high prognostic value and was able to independently predict RFS. Moreover, a nomogram which integrated clinical information and the gene signature was capable of distinguishing high-risk recurrent patients.

Conclusion: These methylation regulators are correlated to clinicopathologic characteristics in PCa and a prognostic model using m6A methylation-related genes is constructed and of high predictive value for recurrence after RP.

ETV4 plays a role on the primary events during the adenoma-adenocarcinoma progression in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide; it is the fourth leading cause of death in the world and the third in Brazil. Mutations in the APC, DCC, KRAS and TP53 genes have been associated with the progression of sporadic CRC, occurring at defined pathological stages of the tumor progression and consequently modulating several genes in the corresponding signaling pathways. Therefore, the identification of gene signatures that occur at each stage during the CRC progression is critical and can present an impact on the diagnosis and prognosis of the patient. In this study, our main goal was to determine these signatures, by evaluating the gene expression of paired colorectal adenoma and adenocarcinoma samples to identify novel genetic markers in association to the adenoma-adenocarcinoma stage transition.

METHODS

Ten paired adenoma and adenocarcinoma colorectal samples were subjected to microarray gene expression analysis. In addition, mutations in APC, KRAS and TP53 genes were investigated by DNA sequencing in paired samples of adenoma, adenocarcinoma, normal tissue, and peripheral blood from ten patients.

RESULTS

Gene expression analysis revealed a signature of 689 differentially expressed genes (DEG) (fold-change> 2, p< 0.05), between the adenoma and adenocarcinoma paired samples analyzed. Gene pathway analysis using the 689 DEG identified important cancer pathways such as remodeling of the extracellular matrix and epithelial-mesenchymal transition. Among these DEG, the ETV4 stood out as one of the most expressed in the adenocarcinoma samples, further confirmed in the adenocarcinoma set of samples from the TCGA database. Subsequent in vitro siRNA assays against ETV4 resulted in the decrease of cell proliferation, colony formation and cell migration in the HT29 and SW480 colorectal cell lines. DNA sequencing analysis revealed KRAS and TP53 gene pathogenic mutations, exclusively in the adenocarcinomas samples.

CONCLUSION

Our study identified a set of genes with high potential to be used as biomarkers in CRC, with a special emphasis on the ETV4 gene, which demonstrated involvement in proliferation and migration.

The Role of pHi in Intestinal Epithelial Proliferation-Transport Mechanisms, Regulatory Pathways, and Consequences

During the maturation of intestinal epithelial cells along the crypt/surface axis, a multitude of acid/base transporters are differentially expressed in their apical and basolateral membranes, enabling processes of electrolyte, macromolecule, nutrient, acid/base and fluid secretion, and absorption. An intracellular pH (pHi)-gradient is generated along the epithelial crypt/surface axis, either as a consequence of the sum of the ion transport activities or as a distinctly regulated entity. While the role of pHi on proliferation, migration, and tumorigenesis has been explored in cancer cells for some time, emerging evidence suggests an important role of the pHi in the intestinal stem cells (ISCs) proliferative rate under physiological conditions. The present review highlights the current state of knowledge about the potential regulatory role of pHi on intestinal proliferation and differentiation.

The targeted inhibition of prostate cancer by iron-based nanoparticles based on bioinformatics

Prostate cancer is an epithelial malignant tumor of the prostate, and it is one of the malignant tumors with a high incidence of urogenital system in men. The local treatment of prostate cancer is mainly radical resection and radical radiotherapy, but they are not applicable to advanced prostate cancer. Systemic therapy mainly includes targeted therapy and immunotherapy which could cause many complications, and will affect the prognosis and quality of life of patients. It is urgent to find new treatments for prostate cancer. Bioinformatics offers hope for us to find reliable therapeutic targets. Bioinformatics can use the tumor informations in database and analyze them to screen out the best differentially expressed genes. Using the selected differentially expressed genes as targets, a gene interference plasmid was designed, and the constructed plasmid was used for targeted gene therapy. There are some problems about gene therapy that need to be solved, such as how to transfer genes to target cells is also an important challenge. Due to their large molecular weight and hydrophilic nature, they cannot enter cells through passive diffusion mechanisms. Here we synthesized a DNA carrier used surface modified iron based nanoparticles, and used it to load plasmid including ShRNA which can inhibit the expression of oncogene SLC4A4 selected by bioinformatics’ method. After that we use this iron based nanoparticles/plasmid DNA nanocomposite to treat prostate cancer cells in vitro and in vivo. The target gene SLC4A4 we had selected using bioinformatics had a strong effect on the proliferation of prostate cells; Our nanocomposite could inhibit the expression of SLC4A4 effectively, it had strong inhibitory effects on prostate cancer cells both in vivo and in vitro, and can be used as a potential method for prostate cancer treatment.

Targeting the pH Paradigm at the Bedside: A Practical Approach

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.

Integration and Comparison of Transcriptomic and Proteomic Data for Meningioma

Meningioma are the most frequent primary intracranial tumour. Management of aggressive meningioma is complex, and development of effective biomarkers or pharmacological interventions is hampered by an incomplete knowledge of molecular landscape. Here, we present an integrated analysis of two complementary omics studies to investigate alterations in the "transcriptome-proteome" profile of high-grade (III) compared to low-grade (I) meningiomas. We identified 3598 common transcripts/proteins and revealed concordant up- and downregulation in grade III vs. grade I meningiomas. Concordantly upregulated genes included FABP7, a fatty acid binding protein and the monoamine oxidase MAOB, the latter of which we validated at the protein level and established an association with Food and Drug Administration (FDA)-approved drugs. Notably, we derived a plasma signature of 21 discordantly expressed genes showing positive changes in protein but negative in transcript levels of high-grade meningiomas, including the validated genes CST3, LAMP2, PACS1 and HTRA1, suggesting the acquisition of these proteins by tumour from plasma. Aggressive meningiomas were enriched in processes such as oxidative phosphorylation and RNA metabolism, whilst concordantly downregulated genes were related to reduced cellular adhesion. Overall, our study provides the first transcriptome-proteome characterisation of meningioma, identifying several novel and previously described transcripts/proteins with potential grade III biomarker and therapeutic significance.

The roles of carbonic anhydrases IX and XII in cancer cell adhesion, migration, invasion and metastasis

The main function of carbonic anhydrases (CAs) in cancer cells is the pH regulation through a conversion of H₂ O and CO₂ to H⁺ and HCO₃ ^- . However, the data of in vitro and in vivo studies have demonstrated that transmembrane isoforms of CA IX and CA XII are involved in various steps of cancer cell migration, invasion and metastasis. According to literature, inhibition of these CAs can affect the expression of multiple proteins. Some scientific groups have reported the possible interactions between CA IX and E-cadherin-catenin system, CA IX and integrins, CA IX, CA XII and ion transporters, which all are highly involved in cell-to-cell adhesion, the formation of membrane protrusions and focal adhesions. Nevertheless, CA IX and CA XII have a high impact on tumour growth and metastases formation. The data discussed in this review are quite recent. It highly support the role of CA IX and CA XII in various cancer metastasis processes through their interactions to other invasion proteins. Nevertheless, all findings show the great potential of these CAs in the context of research and application in clinical use.

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Protective Role of IRBIT on Sodium Bicarbonate Cotransporter-n1 for Migratory Cancer Cells

IP₃ receptor-binding protein released with IP₃ (IRBIT) interacts with various ion channels and transporters. An electroneutral type of sodium bicarbonate cotransporter, NBCn1, participates in cell migration, and its enhanced expression is related to cancer metastasis. The effect of IRBIT on NBCn1 and its relation to cancer cell migration remain obscure. We therefore aimed to determine the effect of IRBIT on NBCn1 and the regulation of cancer cell migration due to IRBIT-induced alterations in NBCn1 activity. Overexpression of IRBIT enhanced cancer cell migration and NBC activity. Knockdown of IRBIT or NBCn1 and treatment with an NBC-specific inhibitor, S0859, attenuated cell migration. Stimulation with oncogenic epidermal growth factor enhanced the expression of NBCn1 and migration of cancer cells by recruiting IRBIT. The recruited IRBIT stably maintained the expression of the NBCn1 transporter machinery in the plasma membrane. Combined inhibition of IRBIT and NBCn1 dramatically inhibited the migration of cancer cells. Combined modulation of IRBIT and NBCn1 offers an effective strategy for attenuating cancer metastasis.

Intracellular pH Regulates Cancer and Stem Cell Behaviors: A Protein Dynamics Perspective

The International Society of Cancer Metabolism (ISCaM) meeting on Cancer Metabolic Rewiring, held in Braga Portugal in October 2019, provided an outstanding forum for investigators to present current findings and views, and discuss ideas and future directions on fundamental biology as well as clinical translations. The first session on Cancer pH Dynamics was preceded by the opening keynote presentation from our group entitled Intracellular pH Regulation of Protein Dynamics: From Cancer to Stem Cell Behaviors. In this review we introduce a brief background on intracellular pH (pHi) dynamics, including how it is regulated as well as functional consequences, summarize key findings included in our presentation, and conclude with perspectives on how understanding the role of pHi dynamics in stem cells can be relevant for understanding how pHi dynamics enables cancer progression.

Role of pH Regulatory Proteins and Dysregulation of pH in Prostate Cancer

Prostate cancer is the fourth most commonly diagnosed cancer, and although it is often a slow-growing malignancy, it is the second leading cause of cancer-associated deaths in men and the first in Europe and North America. In many forms of cancer, when the disease is a solid tumor confined to one organ, it is often readily treated. However, when the cancer becomes an invasive metastatic carcinoma, it is more often fatal. It is therefore of great interest to identify mechanisms that contribute to the invasion of cells to identify possible targets for therapy. During prostate cancer progression, the epithelial cells undergo epithelial-mesenchymal transition that is characterized by morphological changes, a loss of cell-cell adhesion, and invasiveness. Dysregulation of pH has emerged as a hallmark of cancer with a reversed pH gradient and with a constitutively increased intracellular pH that is elevated above the extracellular pH. This phenomenon has been referred to as "a perfect storm" for cancer progression. Acid-extruding ion transporters include the Na⁺/H⁺ exchanger NHE1 (SLC9A1), the Na⁺HCO₃^- cotransporter NBCn1 (SLC4A7), anion exchangers, vacuolar-type adenosine triphosphatases, and the lactate-H⁺ cotransporters of the monocarboxylate family (MCT1 and MCT4 (SLC16A1 and 3)). Additionally, carbonic anhydrases contribute to acid transport. Of these, several have been shown to be upregulated in different human cancers including the NBCn1, MCTs, and NHE1. Here the role and contribution of acid-extruding transporters in prostate cancer growth and metastasis were examined. These proteins make significant contributions to prostate cancer progression.

Pathological role of ion channels and transporters in the development and progression of triple-negative breast cancer

Breast cancer is a common malignancy in women. Among breast cancer types, triple-negative breast cancer (TNBC) tends to affect younger women, is prone to axillary lymph node, lung, and bone metastases; and has a high recurrence rate. Due to a lack of classic biomarkers, the currently available treatments are surgery and chemotherapy; no targeted standard treatment options are available. Therefore, it is urgent to find a novel and effective therapeutic target. As alteration of ion channels and transporters in normal mammary cells may affect cell growth, resulting in the development and progression of TNBC, ion channels and transporters may be promising new therapeutic targets for TNBC. This review summarizes ion channels and transporters related to TNBC and may provide new tumor biomarkers and help in the development of novel targeted therapies.

Membrane Transporters and Channels in Melanoma

Recent research has revealed that ion channels and transporters can be important players in tumor development, progression, and therapy resistance in melanoma. For example, members of the ABC family were shown to support cancer stemness-like features in melanoma cells, while several members of the TRP channel family were reported to act as tumor suppressors.Also, many transporter proteins support tumor cell viability and thus suppress apoptosis induction by anticancer therapy. Due to the high number of ion channels and transporters and the resulting high complexity of the field, progress in understanding is often focused on single molecules and is in total rather slow. In this review, we aim at giving an overview about a broad subset of ion transporters, also illustrating some aspects of the field, which have not been addressed in detail in melanoma. In context with the other chapters in this special issue on "Transportome Malfunctions in the Cancer Spectrum," a comparison between melanoma and these tumors will be possible.

Physiological and pathophysiological role of ion channels and transporters in the colorectum and colorectal cancer

The incidence of colorectal cancer has increased annually, and the pathogenesis of this disease requires further investigation. In normal colorectal tissues, ion channels and transporters maintain the water‐electrolyte balance and acid/base homeostasis. However, dysfunction of these ion channels and transporters leads to the development and progression of colorectal cancer. Therefore, this review focuses on the progress in understanding the roles of ion channels and transporters in the colorectum and in colorectal cancer, including aquaporins (AQPs), Cl⁻ channels, Cl⁻/HCO3‐ exchangers, Na⁺/HCO3‐ transporters and Na⁺/H⁺ exchangers. The goal of this review is to promote the identification of new targets for the treatment and prognosis of colorectal cancer.

TGFβ Signaling Increases Net Acid Extrusion, Proliferation and Invasion in Panc-1 Pancreatic Cancer Cells: SMAD4 Dependence and Link to Merlin/NF2 Signaling

Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer-related death, with a 5-year survival of <10% and severely limited treatment options. PDAC hallmarks include profound metabolic acid production and aggressive local proliferation and invasiveness. This phenotype is supported by upregulated net acid extrusion and epithelial-to-mesenchymal transition (EMT), the latter typically induced by aberrant transforming growth factor-β (TGFβ) signaling. It is, however, unknown whether TGFβ-induced EMT and upregulation of acid extrusion are causally related. Here, we show that mRNA and protein expression of the net acid extruding transporters Na⁺/H⁺ exchanger 1 (NHE1, SLC9A1) and Na⁺, HCO3- cotransporter 1 (NBCn1, SLC4A7) are increased in a panel of human PDAC cell lines compared to immortalized human pancreatic ductal epithelial (HPDE) cells. Treatment of Panc-1 cells (which express SMAD4, required for canonical TGFβ signaling) with TGFβ-1 for 48 h elicited classical EMT with down- and upregulation of epithelial and mesenchymal markers, respectively, in a manner inhibited by SMAD4 knockdown. Accordingly, less pronounced EMT was induced in BxPC-3 cells, which do not express SMAD4. TGFβ-1 treatment elicited a SMAD4-dependent increase in NHE1 expression, and a smaller, SMAD4-independent increase in NBCn1 in Panc-1 cells. Consistent with this, TGFβ-1 treatment led to elevated intracellular pH and increased net acid extrusion capacity in Panc-1 cells, but not in BxPC-3 cells, in an NHE1-dependent manner. Proliferation was increased in Panc-1 cells and decreased in BxPC-3 cells, upon TGFβ-1 treatment, and this, as well as EMT per se, was unaffected by NHE1- or NBCn1 inhibition. TGFβ-1-induced EMT was associated with a 4-fold increase in Panc-1 cell invasiveness, which further increased ~10-fold upon knockdown of the tumor suppressor Merlin (Neurofibromatosis type 2). Knockdown of NHE1 or NBCn1 abolished Merlin-induced invasiveness, but not that induced by TGFβ-1 alone. In conclusion, NHE1 and NBCn1 expression and NHE-dependent acid extrusion are upregulated during TGFβ-1-induced EMT of Panc-1 cells. NHE1 upregulation is SMAD4-dependent, and SMAD4-deficient BxPC-3 cells show no change in pH_i regulation. NHE1 and NBCn1 are not required for EMT per se or EMT-associated proliferation changes, but are essential for the potentiation of invasiveness induced by Merlin knockdown.

The Interplay of Dysregulated pH and Electrolyte Imbalance in Cancer

Cancer cells and tissues have an aberrant regulation of hydrogen ion dynamics driven by a combination of poor vascular perfusion, regional hypoxia, and increased the flux of carbons through fermentative glycolysis. This leads to extracellular acidosis and intracellular alkalinization. Dysregulated pH dynamics influence cancer cell biology, from cell transformation and tumorigenesis to proliferation, local growth, invasion, and metastasis. Moreover, this dysregulated intracellular pH (pHi) drives a metabolic shift to increased aerobic glycolysis and reduced mitochondrial oxidative phosphorylation, referred to as the Warburg effect, or Warburg metabolism, which is a selective feature of cancer. This metabolic reprogramming confers a thermodynamic advantage on cancer cells and tissues by protecting them against oxidative stress, enhancing their resistance to hypoxia, and allowing a rapid conversion of nutrients into biomass to enable cell proliferation. Indeed, most cancers have increased glucose uptake and lactic acid production. Furthermore, cancer cells have very dysregulated electrolyte balances, and in the interaction of the pH dynamics with electrolyte, dynamics is less well known. In this review, we highlight the interconnected roles of dysregulated pH dynamics and electrolytes imbalance in cancer initiation, progression, adaptation, and in determining the programming and reprogramming of tumor cell metabolism.

MiR-223-3p promotes cell proliferation and metastasis by downregulating SLC4A4 in clear cell renal cell carcinoma

MicroRNAs (miRNAs) are known to affect the occurrence and progression of cancer. We therefore evaluated the involvement of miR-223-3p in renal cell cancer. MiR-223-3p was highly expressed in clear cell renal cell cancer tissues. Clear cell renal cell cancer patients with higher miR-223-3p expression had higher tumor stages and grades and poorer prognoses. In renal cancer cells, overexpression of miR-223-3p enhanced cell proliferation and metastasis, while inhibition of miR-223-3p reduced the malignant capacity of the cells. MiR-223-3p was found to bind directly to solute carrier family 4, member 4 (SLC4A4) mRNA, thereby reducing SLC4A4 mRNA and protein expression. SLC4A4 overexpression restrained cell proliferation and metastasis by suppressing Kirsten rat sarcoma viral oncogene (KRAS) expression in renal cancer cells. SLC4A4 expression correlated negatively with miR-223-3p expression in patient samples. Given that miR-223-3p suppressed the SLC4A4/KRAS axis, miR-223-3p gene therapy could be an effective treatment for renal cancer.

Application of weighted gene co‑expression network analysis to explore the potential diagnostic biomarkers for colorectal cancer

Colorectal cancer (CRC) is one of the most common malignant diseases in the world. Although mechanistic studies have been conducted on the pathogenesis of CRC, the molecular mechanism of CRC tumorigenesis remains unclear. In the present study, the weighted gene co-expression network analysis was performed for the Gene Expression Omnibus (GEO) dataset GSE87211, in order to analyze the key modules involved in the pathogenesis of CRC. Next, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed on the key module genes to analyze the functional pathways involved. The hub genes were screened using the Cytoscape platform and verified by a second GEO dataset, GSE21510. Finally, 10 hub genes were identified in 2 key modules (the green and brown modules) as the genes most significantly associated with the tumorigenesis of CRC. The 5 hub genes from the green module included collagen type I α1 chain, collagen type XII α1 chain, collagen triple helix repeat containing 1, inhibin subunit βa (INHBA) and chromobox 2 (CBX2), while the 5 hub genes from the brown module included bestrophin 2 (BEST2), carbonic anhydrase 2, glucagon, solute carrier family 4 member 4 and gliomedin. The 2 key modules with the 10 hub genes identified may regulate the occurrence and development of CRC through the extracellular matrix pathway, PI3K-Akt and chemokine signaling pathways, thus providing a reference for understanding the complex mechanism of tumorigenesis in CRC. Of note, few studies have reported the pathogenesis of CRC with the 3 identified hub genes, INHBA, CBX2 and BEST2. Further investigation of the molecular mechanism of these genes in CRC is recommended.

Down-regulated Solute Carrier Family 4 Member 4 Predicts Poor Progression in Colorectal Cancer

Aim: To identify potential key candidate genes, whose expression and clinical significance was further assessed in colorectal cancer (CRC).

Methods: Three original microarray datasets (GSE41328, GSE22598, and GSE23878) from NCBI-GEO were used to analyze differentially expressed genes (DEGs) in CRC. Online database analyses through Oncomine and GEIPA were performed to evaluate SLC4A4 expression and explore the prognostic merit of SLC4A4 expression, which was further confirmed by analyses from QPCR based cDNA array and IHC based tissue microarray (TMA). STRING website was used to explore the interaction between SLC4A4 with other DEGs based on the protein-protein interaction (PPI) networks.

Results: Analysis of three original microarray datasets from GEO identified 82 shared, differentially expressed genes (28 upregulated and 54 down-regulated) in CRC tissues. Online analyses from Oncomine and GEIPA revealed lower SLC4A4 mRNA expression in CRC tissues compared to adjacent normal tissues, which were further confirmed by QPCR based cDNA array and IHC based TMA analyses on both mRNA and protein levels. Survival analyses through GEIPA and from TMA demonstrated that low SLC4A4 expression is correlated with worse overall survival among patients with CRC. Survival analysis from Kaplan-meier plotter demonstrated that low SLC4A4 expression is significantly associated with poor progression (including relapse-free survival, overall survival, distant metastasis-free survival, post-progression survival) of patients with breast cancer, lung cancer, gastric cancer, and ovarian cancer. PPI analysis found that SLC4A4 is highly correlated with various genes, including SLC9A3, SLC26A6, ENSG00000214921, SLC26A4, SLC9A3R1, and SLC9A1.

Conclusion: The mRNA and protein levels of SLC4A4 were decreased in CRC tissues, and low expression of SLC4A4 significantly correlated with shorter survival of CRC patients and poorer progression of patients with breast cancer, lung cancer, gastric cancer and ovarian cancer, suggesting potential role of SLC4A4 on tumor suppression and prognostic prediction in multiple malignancies including CRC.

An overview of carbonic anhydrases and membrane channels of synoviocytes in inflamed joints

The highly aggressive fibroblast-like synoviocytes (FLSs) are inflammatory mediators involved in synovial joint destruction. Membrane channels and transporters are essential components of the cell migration apparatus and are involved in various cellular functions. Although evidence is emerging that cell migration is a physiological/pathological process, the mechanism of highly dynamic synoviocytes linked to the membrane channels and carbonic anhydrases (CAs) in inflamed joints is only partially understood. In this review, topics covered will give a brief overview of CAs and the membrane channels of synoviocytes. We have also systematically focused on the role of FLS channels and transporters under various conditions, including rheumatoid arthritis (RA), to understand the pathophysiology of the migration of synoviocytes as inflammatory mediators in joints.

The Fundamental Role of Bicarbonate Transporters and Associated Carbonic Anhydrase Enzymes in Maintaining Ion and pH Homeostasis in Non-Secretory Organs

The bicarbonate ion has a fundamental role in vital systems. Impaired bicarbonate transport leads to various diseases, including immune disorders, cystic fibrosis, tumorigenesis, kidney diseases, brain dysfunction, tooth fracture, ischemic reperfusion injury, hypertension, impaired reproductive system, and systemic acidosis. Carbonic anhydrases are involved in the mechanism of bicarbonate movement and consist of complex of bicarbonate transport systems including bicarbonate transporters. This review focused on the convergent regulation of ion homeostasis through various ion transporters including bicarbonate transporters, their regulatory enzymes, such as carbonic anhydrases, pH regulatory role, and the expression pattern of ion transporters in non-secretory systems throughout the body. Understanding the correlation between these systems will be helpful in order to obtain new insights and design potential therapeutic strategies for the treatment of pH-related disorders. In this review, we have discussed the broad prospects and challenges that remain in elucidation of bicarbonate-transport-related biological and developmental systems.