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

Investigating the anti-lung cancer properties of Zhuang medicine Cycas revoluta Thunb. leaves targeting ion channels and transporters through a comprehensive strategy

BACKGROUND

Cycas revoluta Thunb., known for its ornamental, economic, and medicinal value, has leaves often discarded as waste. However, in ethnic regions of China, the leaves (CRL) are used in folk medicine for anti-tumor properties, particularly for regulating pathways related to cancer. Recent studies on ion channels and transporters (ICTs) highlight their therapeutic potential against cancer, making it vital to identify CRL's active constituents targeting ICTs in lung cancer.

PURPOSE

This study aims to uncover bioactive substances in CRL and their mechanisms in regulating ICTs for lung cancer treatment using network pharmacology, bioinformatics, molecular docking, molecular dynamics (MD) simulations, in vitro cell assays and HPLC.

METHODS

We analyzed 62 CRL compounds, predicted targets using PubChem and SwissTargetPrediction, identified lung cancer and ICT targets via GeneCards, and visualized overlaps with R software. Interaction networks were constructed using Cytoscape and STRING. Gene expression, GO, and KEGG analyses were performed using R software. TCGA data provided insights into differential, correlation, survival, and immune analyses. Key interactions were validated through molecular docking and MD simulations. Main biflavonoids were quantified using HPLC, and in vitro cell viability assays were conducted for key biflavonoids.

RESULTS

Venn diagram analysis identified 52 intersecting targets and ten active CRL compounds. The PPI network highlighted seven key targets. GO and KEGG analysis showed CRL-targeted ICTs involved in synaptic transmission, GABAergic synapse, and proteoglycans in cancer. Differential expression and correlation analysis revealed significant differences in five core targets in lung cancer tissues. Survival analysis linked EGFR and GABRG2 with overall survival, and immune infiltration analysis associated the core targets with most immune cell types. Molecular docking indicated strong binding of CRL ingredients to core targets. HPLC revealed amentoflavone as the most abundant biflavonoid, followed by hinokiflavone, sciadopitysin, and podocarpusflavone A. MD simulations showed that podocarpusflavone A and amentoflavone had better binding stability with GABRG2, and the cell viability assay also proved that they had better anti-lung cancer potential.

CONCLUSIONS

This study identified potential active components, targets, and pathways of CRL-targeted ICTs for lung cancer treatment, suggesting CRL's utility in drug development and its potential beyond industrial waste.

Prognostic Value and Immune Signatures of Anoikis-related Genes in Breast Cancer

From databases of the Cancer Genome Atlas (TCGA) and GSE42568, transcriptome data of breast cancer patients was obtained. Then, anoikis-related genes (ANRGs) were identified and constructed a risk score system. As a threshold value, the median risk score was used to stratify patients into low-risk and high-risk groups. Kaplan-Meier analysis was then conducted to evaluate the prognostic ability of the risk score system, which was validated using GSE7390. Furthermore, we identified potential enrichment of function and tumor immune infiltration in the model. Finally, the biological functions of a risk gene (EPB41L4B) in breast cancer were investigated through in vitro experiments. We constructed a risk score system via 9 prognosis ANRGs (CXCL2, EPB41L4B, SLC7A5, SFRP1, SDC1, BHLHE41, SPINT1, KRT15, and CD24). The Kaplan-Meier analysis showed that both TCGA-BRCA (training set) and GSE7390 (testing set) patients with high-risk status had significantly worse survival outcomes. In addition, the calibration plots were in good agreement with the prognosis prediction. Breast cancer patients with immunosuppressive microenvironment could be screened using risk groups since risk scores were correlated negatively with ESTIMATE score, tumor-infiltration lymphocytes, immune checkpoints, and chemotactic factors. Furthermore, cellular viability and cell migration of cancerous breast cells were inhibited and apoptosis was promoted by down-regulation of EPB41L4B gene expression. Based on ANRGs, a 9-gene prognostic model could be developed to predict breast cancer prognosis; moreover, patients of the high-risk group were in an immunosuppressed tumor microenvironment.

Increased V-ATPase activity can lead to chemo-resistance in oral squamous cell carcinoma via autophagy induction: new insights

Oral squamous cell carcinoma (OSCC) is a cancer type with a high rate of recurrence and a poor prognosis. Tumor chemo-resistance remains an issue for OSCC patients despite the availability of multimodal therapy options, which causes an increase in tumor invasiveness. Vacuolar ATPase (V-ATPase), appears to be one of the most significant molecules implicated in MDR in tumors like OSCC. It is primarily responsible for controlling the acidity in the solid tumors' microenvironment, which interferes with the absorption of chemotherapeutic medications. However, the exact cellular and molecular mechanisms V-ATPase plays in OSCC chemo-resistance have not been understood. Uncovering these mechanisms can contribute to combating OSCC chemo-resistance and poor prognosis. Hence, in this review, we suggest that one of these underlying mechanisms is autophagy induced by V-ATPase which can potentially contribute to OSCC chemo-resistance. Finally, specialized autophagy and V-ATPase inhibitors may be beneficial as an approach to reduce drug resistance to anticancer therapies in addition to serving as coadjuvants in antitumor treatments. Also, V-ATPase could be a prognostic factor for OSCC patients. However, in the future, more investigations are required to demonstrate these suggestions and hypotheses.

Strengthening the basics: acids and bases influence vascular structure and function, tissue perfusion, blood pressure, and human cardiovascular disease

Acids and their conjugate bases accumulate in or dissipate from the interstitial space when tissue perfusion does not match the metabolic demand. Extracellular acidosis dilates most arterial beds, but associated acid-base disturbances-e.g., intracellular acidification and decreases in HCO3- concentration-can also elicit pro-contractile influences that diminish vasodilation and even dominate in some vascular beds to cause vasoconstriction. The ensemble activities of the acid-base-sensitive reactions in vascular smooth muscle and endothelial cells optimize vascular resistance for blood pressure control and direct the perfusion towards active tissue. In this review, we describe the mechanisms of intracellular pH regulation in the vascular wall and discuss how vascular smooth muscle and endothelial cells sense acid-base disturbances. We further deliberate on the functional effects of local acid-base disturbances and their integrated cardiovascular consequences under physiological and pathophysiological conditions. Finally, we address how mutations and polymorphisms in the molecular machinery that regulates pH locally and senses acid-base disturbances in the vascular wall can result in cardiovascular disease. Based on the emerging molecular insight, we propose that targeting local pH-dependent effectors-rather than systemic acid-base disturbances-has therapeutic potential to interfere with the progression and reduce the severity of cardiovascular disease.

Multiple Regulatory Signals and Components in the Modulation of Bicarbonate Transporters

Bicarbonate transporters are responsible for the appropriate flux of bicarbonate across the plasma membrane to perform various fundamental cellular functions. The functions of bicarbonate transporters, including pH regulation, cell migration, and inflammation, are highlighted in various cellular systems, encompassing their participation in both physiological and pathological processes. In this review, we focused on recently identified modulatory signaling components that regulate the expression and activity of bicarbonate transporters. Moreover, we addressed recent advances in our understanding of cooperative systems of bicarbonate transporters and channelopathies. This current review aims to provide a new, in-depth understanding of numerous human diseases associated with the dysfunction of bicarbonate transporters.

A simple yet multifaceted 90 years old, evergreen enzyme: Carbonic anhydrase, its inhibition and activation

Advances in the carbonic anhydrase (CA, EC 4.2.1.1) research over the last three decades are presented, with an emphasis on the deciphering of the activation mechanism, the development of isoform-selective inhibitors/ activators by the tail approach and their applications in the management of obesity, hypoxic tumors, neurological conditions, and as antiinfectives.

Carbonic anhydrases reduce the acidity of the tumor microenvironment, promote immune infiltration, decelerate tumor growth, and improve survival in ErbB2/HER2-enriched breast cancer

BACKGROUND

Carbonic anhydrases catalyze CO₂/HCO₃^- buffer reactions with implications for effective H⁺ mobility, pH dynamics, and cellular acid-base sensing. Yet, the integrated consequences of carbonic anhydrases for cancer and stromal cell functions, their interactions, and patient prognosis are not yet clear.

METHODS

We combine (a) bioinformatic analyses of human proteomic data and bulk and single-cell transcriptomic data coupled to clinicopathologic and prognostic information; (b) ex vivo experimental studies of gene expression in breast tissue based on quantitative reverse transcription and polymerase chain reactions, intracellular and extracellular pH recordings based on fluorescence confocal microscopy, and immunohistochemical protein identification in human and murine breast cancer biopsies; and (c) in vivo tumor size measurements, pH-sensitive microelectrode recordings, and microdialysis-based metabolite analyses in mice with experimentally induced breast carcinomas.

RESULTS

Carbonic anhydrases-particularly the extracellular isoforms CA4, CA6, CA9, CA12, and CA14-undergo potent expression changes during human and murine breast carcinogenesis. In patients with basal-like/triple-negative breast cancer, elevated expression of the extracellular carbonic anhydrases negatively predicts survival, whereas, surprisingly, the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer. Carbonic anhydrase inhibition attenuates cellular net acid extrusion and extracellular H⁺ elimination from diffusion-restricted to peripheral and well-perfused regions of human and murine breast cancer tissue. Supplied in vivo, the carbonic anhydrase inhibitor acetazolamide acidifies the microenvironment of ErbB2-induced murine breast carcinomas, limits tumor immune infiltration (CD3⁺ T cells, CD19⁺ B cells, F4/80⁺ macrophages), lowers inflammatory cytokine (Il1a, Il1b, Il6) and transcription factor (Nfkb1) expression, and accelerates tumor growth. Supporting the immunomodulatory influences of carbonic anhydrases, patient survival benefits associated with high extracellular carbonic anhydrase expression in HER2-enriched breast carcinomas depend on the tumor inflammatory profile. Acetazolamide lowers lactate levels in breast tissue and blood without influencing breast tumor perfusion, suggesting that carbonic anhydrase inhibition lowers fermentative glycolysis.

CONCLUSIONS

We conclude that carbonic anhydrases (a) elevate pH in breast carcinomas by accelerating net H⁺ elimination from cancer cells and across the interstitial space and (b) raise immune infiltration and inflammation in ErbB2/HER2-driven breast carcinomas, restricting tumor growth and improving patient survival.

Mesoporous nanodrug delivery system: a powerful tool for a new paradigm of remodeling of the tumor microenvironment

Tumor microenvironment (TME) plays an important role in tumor progression, metastasis and therapy resistance. Remodeling the TME has recently been deemed an attractive tumor therapeutic strategy. Due to its complexity and heterogeneity, remodeling the TME still faces great challenges. With the great advantage of drug loading ability, tumor accumulation, multifactor controllability, and persistent guest molecule release ability, mesoporous nanodrug delivery systems (MNDDSs) have been widely used as effective antitumor drug delivery tools as well as remolding TME. This review summarizes the components and characteristics of the TME, as well as the crosstalk between the TME and cancer cells and focuses on the important role of drug delivery strategies based on MNDDSs in targeted remodeling TME metabolic and synergistic anticancer therapy.

Loss of RPTPγ primes breast tissue for acid extrusion, promotes malignant transformation and results in early tumour recurrence and shortened survival

BACKGROUND

While cellular metabolism and acidic waste handling accelerate during breast carcinogenesis, temporal patterns of acid-base regulation and underlying molecular mechanisms responding to the tumour microenvironment remain unclear.

METHODS

We explore data from human cohorts and experimentally investigate transgenic mice to evaluate the putative extracellular HCO₃^--sensor Receptor Protein Tyrosine Phosphatase (RPTP)γ during breast carcinogenesis.

RESULTS

RPTPγ expression declines during human breast carcinogenesis and particularly in high-malignancy grade breast cancer. Low RPTPγ expression associates with poor prognosis in women with Luminal A or Basal-like breast cancer. RPTPγ knockout in mice favours premalignant changes in macroscopically normal breast tissue, accelerates primary breast cancer development, promotes malignant breast cancer histopathologies, and shortens recurrence-free survival. In RPTPγ knockout mice, expression of Na⁺,HCO₃^--cotransporter NBCn1-a breast cancer susceptibility protein-is upregulated in normal breast tissue but, contrary to wild-type mice, shows no further increase during breast carcinogenesis. Associated augmentation of Na⁺,HCO₃^--cotransport in normal breast tissue from RPTPγ knockout mice elevates steady-state intracellular pH, which has known pro-proliferative effects.

CONCLUSIONS

Loss of RPTPγ accelerates cellular net acid extrusion and elevates NBCn1 expression in breast tissue. As these effects precede neoplastic manifestations in histopathology, we propose that RPTPγ-dependent enhancement of Na⁺,HCO₃^--cotransport primes breast tissue for cancer development.

Amplified Ca2+ dynamics and accelerated cell proliferation in breast cancer tissue during purinergic stimulation

Intracellular Ca²⁺ dynamics shape malignant behaviors of cancer cells. Whereas previous studies focused on cultured cancer cells, we here used breast organoids and colonic crypts freshly isolated from human and murine surgical biopsies. We performed fluorescence microscopy to evaluate intracellular Ca²⁺ concentrations in breast and colon cancer tissue with preferential focus on intracellular Ca²⁺ release in response to purinergic and cholinergic stimuli. Inhibition of the sarco‐/endoplasmic reticulum Ca²⁺ ATPase with cyclopiazonic acid elicited larger Ca²⁺ responses in breast cancer tissue, but not in colon cancer tissue, relative to respective normal tissue. The resting intracellular Ca²⁺ concentration was elevated, and ATP, UTP and acetylcholine induced strongly augmented intracellular Ca²⁺ responses in breast cancer tissue compared with normal breast tissue. In contrast, resting intracellular Ca²⁺ levels and acetylcholine‐induced increases in intracellular Ca²⁺ concentrations were unaffected and ATP‐ and UTP‐induced Ca²⁺ responses were smaller in colon cancer tissue compared with normal colon tissue. In accordance with the amplified Ca²⁺ responses, ATP and UTP substantially increased proliferative activity—evaluated by bromodeoxyuridine incorporation—in breast cancer tissue, whereas the effect was minimal in normal breast tissue. ATP caused cell death—identified with ethidium homodimer‐1 staining—in breast cancer tissue only at concentrations above the expected pathophysiological range. We conclude that intracellular Ca²⁺ responses are amplified in breast cancer tissue, but not in colon cancer tissue, and that nucleotide signaling stimulates breast cancer cell proliferation within the extracellular concentration range typical for solid cancer tissue.

Inhibition of NHE-1 Increases Smoke-Induced Proliferative Activity of Barrett's Esophageal Cell Line

Several clinical studies indicate that smoking predisposes its consumers to esophageal inflammatory and malignant diseases, but the cellular mechanism is not clear. Ion transporters protect esophageal epithelial cells by maintaining intracellular pH at normal levels. In this study, we hypothesized that smoking affects the function of ion transporters, thus playing a role in the development of smoking-induced esophageal diseases. Esophageal cell lines were treated with cigarettesmoke extract (CSE), and the viability and proliferation of the cells, as well as the activity, mRNA and protein expression of the Na+/H+ exchanger-1 (NHE-1), were studied. NHE-1 expression was also investigated in human samples. For chronic treatment, guinea pigs were exposed to tobacco smoke, and NHE-1 activity was measured. Silencing of NHE-1 was performed by using specific siRNA. CSE treatment increased the activity and protein expression of NHE-1 in the metaplastic cells and decreased the rate of proliferation in a NHE-1-dependent manner. In contrast, CSE increased the proliferation of dysplastic cells independently of NHE-1. In the normal cells, the expression and activity of NHE-1 decreased due to in vitro and in vivo smoke exposure. Smoking enhances the function of NHE-1 in Barrett's esophagus, and this is presumably a compensatory mechanism against this toxic agent.