Expression of AE1/p16 promoted degradation of AE2 in gastric cancer cells

Potential Theranostic Roles of SLC4 Molecules in Human Diseases

The solute carrier family 4 (SLC4) is an important protein responsible for the transport of various ions across the cell membrane and mediating diverse physiological functions, such as the ion transporting function, protein-to-protein interactions, and molecular transduction. The deficiencies in SLC4 molecules may cause multisystem disease involving, particularly, the respiratory system, digestive, urinary, endocrine, hematopoietic, and central nervous systems. Currently, there are no effective strategies to treat these diseases. SLC4 proteins are also found to contribute to tumorigenesis and development, and some of them are regarded as therapeutic targets in quite a few clinical trials. This indicates that SLC4 proteins have potential clinical prospects. In view of their functional characteristics, there is a critical need to review the specific functions of bicarbonate transporters, their related diseases, and the involved pathological mechanisms. We summarize the diseases caused by the mutations in SLC4 family genes and briefly introduce the clinical manifestations of these diseases as well as the current treatment strategies. Additionally, we illustrate their roles in terms of the physiology and pathogenesis that has been currently researched, which might be the future therapeutic and diagnostic targets of diseases and a new direction for drug research and development.

Acid-adapted cancer cells alkalinize their cytoplasm by degrading the acid-loading membrane transporter anion exchanger 2, SLC4A2

Acidic environments reduce the intracellular pH (pHi) of most cells to levels that are sub-optimal for growth and cellular functions. Yet, cancers maintain an alkaline cytoplasm despite low extracellular pH (pHe). Raised pHi is thought to be beneficial for tumor progression and invasiveness. However, the transport mechanisms underpinning this adaptation have not been studied systematically. Here, we characterize the pHe-pHi relationship in 66 colorectal cancer cell lines and identify the acid-loading anion exchanger 2 (AE2, SLC4A2) as a regulator of resting pHi. Cells adapt to chronic extracellular acidosis by degrading AE2 protein, which raises pHi and reduces acid sensitivity of growth. Acidity inhibits mTOR signaling, which stimulates lysosomal function and AE2 degradation, a process reversed by bafilomycin A1. We identify AE2 degradation as a mechanism for maintaining a conducive pHi in tumors. As an adaptive mechanism, inhibiting lysosomal degradation of AE2 is a potential therapeutic target.

Pathophysiological role of ion channels and transporters in gastrointestinal mucosal diseases

The incidence of gastrointestinal (GI) mucosal diseases, including various types of gastritis, ulcers, inflammatory bowel disease and GI cancer, is increasing. Therefore, it is necessary to identify new therapeutic targets. Ion channels/transporters are located on cell membranes, and tight junctions (TJs) affect acid–base balance, the mucus layer, permeability, the microbiota and mucosal blood flow, which are essential for maintaining GI mucosal integrity. As ion channel/transporter dysfunction results in various GI mucosal diseases, this review focuses on understanding the contribution of ion channels/transporters to protecting the GI mucosal barrier and the relationship between GI mucosal disease and ion channels/transporters, including Cl⁻/HCO₃⁻ exchangers, Cl⁻ channels, aquaporins, Na⁺/H⁺ exchangers, and K⁺ channels. Here, we provide novel prospects for the treatment of GI mucosal diseases.

CAR-T Cell Therapy-An Overview of Targets in Gastric Cancer

Gastric cancer (GC) is one of the most commonly diagnosed malignancies and, unfortunately, still has a high mortality rate. Recent research points to CAR-T immunotherapy as a promising treatment for this disease. Using genetically engineered T cells designed to target a previously selected antigen, researchers are able to harness the natural anti-tumor activity of T cells. For therapy to be successful, however, it is essential to choose antigens that are present on tumor cells but not on healthy cells. In this review, we present an overview of the most important targets for CAR-T therapy in the context of GC, including their biologic function and therapeutic application. A number of clinical studies point to the following as important markers in GC: human epidermal growth factor receptor 2, carcinoembryonic antigen, mucin 1, epithelial cell adhesion molecule, claudin 18.2, mesothelin, natural-killer receptor group 2 member D, and folate receptor 1. Although these markers have been met with some success, the search for new and improved targets continues. Key among these novel biomarkers are the B7H6 ligand, actin-related protein 2/3 (ARP 2/3), neuropilin-1 (NRP-1), desmocollin 2 (DSC2), anion exchanger 1 (AF1), and cancer-related antigens CA-72-4 and CA-19-9.

Anion exchanger 2 suppresses cellular movement and has prognostic significance in esophageal squamous cell carcinoma

Background

Recent studies have reported essential roles for various intracellular pH regulators in epithelial carcinogenesis and tumor progression. The aims of the present study were to investigate the role of anion exchanger 2 (AE2) in the regulation of tumor progression-related genes and the prognostic value of its expression in esophageal squamous cell carcinoma (ESCC).

Results

AE2 was strongly expressed in KYSE170 and TE13 cells. The depletion of AE2 in these cells increased cell migration and inhibited the induction of apoptosis. The results of the microarray analysis revealed that various matrix metalloproteinase (MMP) signaling pathway-related genes, such as MMP1, MMP12, and TIMP4, were up- or down-regulated in AE2-depleted KYSE170 cells. Immunohistochemical staining showed that AE2 was primarily located in the cell membranes or cytoplasm of carcinoma cells, and its expression pattern at the invasive front of the tumor was related to the pT category. Prognostic analyses revealed that the low-grade expression of AE2 at the invasive front was associated with shorter postoperative survival.

Conclusions

The results of the present study suggest that reductions in AE2 in ESCC enhance cellular movement by activating MMP signaling pathways and are related to a poor prognosis in patients with ESCC.

Methods

In human ESCC cell lines, knockdown experiments were conducted using AE2 siRNA, and the effects on cellular movement and survival were analyzed. The gene expression profiles of cells were examined using a microarray analysis. An immunohistochemical analysis was performed on 61 primary tumor samples obtained from ESCC patients who underwent esophagectomy.

Restoration of secreted frizzled-related protein 1 suppresses growth and increases cisplatin sensitivity in laryngeal carcinoma cells by downregulating NHE1

It has been documented that secreted frizzled-related protein 1 (SFRP1) is epigenetically silenced in laryngeal carcinoma. However, the function of SFRP1 in laryngeal carcinoma remains elusive. In this study, we performed gain-of-function studies to determine the roles of SFRP1 in laryngeal carcinoma growth, tumorigenesis, and cisplatin resistance. Laryngeal carcinoma cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC) and examined for SFRP1 expression. The effects of overexpression of SFRP1 on cell proliferation, colony formation, apoptosis, tumorigenesis, and cisplatin sensitivity were assessed. It was found that 5-aza-dC exposure significantly induced the expression of SFRP1 in both Hep-2 and SNU899 laryngeal carcinoma cells. Ectopic expression of SFRP1 significantly decreased cell proliferation and colony formation in vitro and retarded xenograft tumor growth in vivo. SFRP1-overexpressing Hep-2 cells displayed a higher percentage of apoptosis and enhancement of caspase-3 cleavage, which was coupled with loss of Δψm and increased release of cytochrome c from the mitochondria to the cytosol. Moreover, SFRP1 overexpression sensitized laryngeal carcinoma cells to cisplatin and decreased intracellular pH values. Mechanistically, SFRP1 inhibited the expression of Na+/H+ exchanger 1 (NHE1) and overexpression of NHE1 reversed the suppressive activity of SFRP1 on laryngeal carcinoma cells. In conclusion, we demonstrate that SFRP1 induces mitochondrial apoptosis and increases cisplatin sensitivity in laryngeal carcinoma cells via downregulation of NHE1. Delivery of SFRP1 may offer therapeutic benefits in the treatment of laryngeal carcinoma.

Gastrin Enhances Autophagy and Promotes Gastric Carcinoma Proliferation via Inducing AMPKα

Gastric cancer (GC) is one of the most frequent epithelial malignancies worldwide. The gastrointestinal (GI) peptide gastrin is an important regulator of the secretion and release of gastric acid from stomach parietal cells, and it also plays a vital role in the development and progression of GC. The aim of the current study was to investigate the role and underlying mechanism of gastrin and autophagy in regulating GC tumorigenesis. Gastrin-17 amide (G-17) was applied in the GC cell lines SGC7901 and MGC-803. The results showed that G-17 maintained the high viability of SGC7901 and MGC-803. The expression of autophagy marker proteins LC3II and Beclin1 was significantly increased, while the autophagy substrate p62 was obviously decreased in the gastrin group compared with the control group. Moreover, G-17 strengthened the expressions of AMPKα, Ras, Raf, MEK, and ERK1/2. Additionally, administration of AMPKα siRNA counteracted the effect of gastrin in SGC7901 cells. Finally, in an in vivo study of the tumor growth and survival rate of rats, the levels of AMPKα/Ras/Raf/MEK/ERK were significantly increased in the gastrin group and decreased following AMPKα shRNA injection. In conclusion, these findings indicate that gastrin plays a tumorigenic role by promoting autophagy in GC and may provide a novel therapeutic target for GC treatment.

Value of pH regulators in the diagnosis, prognosis and treatment of cancer

Altered metabolism, associated with acidification of the extracellular milieu, is one of the major features of cancer. As pH regulation is crucial for the maintenance of all biological functions, cancer cells rely on the activity of lactate exporters and proton transporters to regulate their intracellular pH. The major players in cancer pH regulation are proton pump ATPases, sodium-proton exchangers (NHEs), monocarboxylate transporters (MCTs), carbonic anhydrases (CAs) and anion exchangers (AEs), which have been shown to be upregulated in several human malignancies. Thanks to the activity of the proton pumps and transporters, tumours acidify their microenvironment, becoming more aggressive and resistant to therapy. Thus, targeting tumour pH may contribute to more effective anticancer strategies for controlling tumour progression and therapeutic resistance. In the present study, we review the role of the main pH regulators expressed in human cancer cells, including their diagnostic and prognostic value, as well as their usefulness as therapeutic targets.

PCAF acts as a gastric cancer suppressor through a novel PCAF-p16-CDK4 axis

Gastric cancer (GC) is a leading cause of cancer-related death worldwide and the pathogenesis of GC remains largely unknown. Here, we demonstrate a novel mechanism by which P300/CBP associating factor (PCAF) acts as a tumor suppressor in GC cells. We showed that both PCAF mRNA and protein were downregulated in GC cells, and that this downregulation correlated with poor survival. Meanwhile, the interaction between human anion exchanger 1 (AE1) and p16 is a key event in GC development. We found that PCAF inhibited GC growth by interacting with AE1 and p16 to promote ubiquitin-mediated degradation of AE1 and p16 upregulation and translocation into the nucleus. Binding of nuclear p16 to CDK4 prevented the CDK4-Cyclin D1 interaction to inhibit GC proliferation. Furthermore, reduced PCAF levels in GC cells were associated with intracellular alkalinization and decreased immunity. Together these results suggest that PCAF acts as a GC suppressor through a novel PCAF-p16-CDK4 axis. The downregulation of PCAF expression in GC cells that follows intracellular alkalinization and decreased immune response, indicates that GC therapies should focus on restoring PCAF levels.