KV11.1 Potassium Channel and the Na+/H+ Antiporter NHE1 Modulate Adhesion-Dependent Intracellular pH in Colorectal Cancer Cells

Abstract

Increasing evidence indicates that ion channels and transporters cooperate in regulating different aspects of tumor pathophysiology. In cancer cells, H + /HCO 3 transporters usually invert the transmembrane pH gradient typically observed in non-neoplastic cells, which is thought to contribute to cancer malignancy. To what extent the pH-regulating transporters are functionally linked to K + channels, which are central regulators of cell membrane potential (V m ), is unclear. We thus investigated in colorectal cancer cells the implication of the pH-regulating transporters and K V 11.1 (also known as hERG1) in the pH modifications stimulated by integrin-dependent cell adhesion. Colorectal cancer cell lines (HCT 116 and HT 29) were seeded onto b1 integrin-dependent substrates, collagen I and fibronectin. This led to a transient cytoplasmic alkalinization, which peaked at 90 min of incubation, lasted approximately 180 min, and was inhibited by antibodies blocking the b1 integrin. The effect was sensitive to amiloride (10 µM) and cariporide (5 µM), suggesting that it was mainly caused by the activity of the Na + /H + antiporter NHE1. Blocking K V 11.1 with E4031 shows that channel activity contributed to modulate the b1 integrindependent pH i increase. Interestingly, both NHE1 and K V 11.1 modulated the colorectal cancer cell motility triggered by b1 integrin-dependent adhesion. Finally, the b1 integrin subunit, K V 11.1 and NHE1 co-immunoprecipitated in colorectal cancer cells seeded onto Collagen I, suggesting the formation of a macromolecular complex following integrinmediated adhesion. We conclude that the interaction between K V 11.1, NHE1, and b1 integrin contributes to regulate colorectal cancer intracellular pH in relation to the tumor microenvironment, suggesting novel pharmacological targets to counteract pro-invasive and, hence, pro-metastatic behavior in colorectal cancer.

Harnessing the hERG1/β1 Integrin Complex via a Novel Bispecific Single-chain Antibody: An Effective Strategy against Solid Cancers

“…Spheroid growth was monitored taking photos every 24 hours using a Nikon Eclipse TE300 microscope, and analyzing their volume using Spheroid Sizer software (MathLab Inc). Lateral motility was assessed by a monolayer wound assay as described in (18), adding the scDb either at the IC 50 concentration determined for each cell line, or at 50 or 100 g/ml.…”

“…This does not occur in the heart, where hERG1 is bound to classical accessory subunits, such as the potassium voltage-gated channel subfamily E regulatory subunit 1 KCNE1 (14). In cancer cells, the hERG1/1 integrin complex is triggered by integrin-mediated adhesion to proteins of the extracellular matrix (12,13,18) which leads to the activation of intracellular signaling pathways, mainly centered on PI3K and Akt (19). These signaling pathways in turn control cancer cell survival, proliferation and migration, and promote tumor progression and metastatic spread (20).…”

Advances in research on the regulatory mechanism of NHE1 in tumors (Review)

“…In colorectal cancer cells, β1 integrin-mediated adhesion to ECM proteins, such as collagen type I and adhesin, triggers an early and transient pHi alkalinization, from 6.7 to 7.2. The effect is caused by NHE1 activation and is modulated by the activity of the voltage-dependent K + channel KV11.1 (87). With respect to antitumor therapy, cisplatin is considered as a broad-spectrum antitumor drug.…”

Emerging role of cellular senescence in the pathogenesis of oral submucous fibrosis and its malignant transformation

“…In normal cells, intracellular pH (pHi) is slightly acidic, while extracellular pH (pHe) is alkaline. The alkalization of pHi and acidification of pHe in cancer is referred to as pH gradient reversal 42,44,49,50 . The acidification pHe has been shown to increase angiogenesis, immunosuppression, chemoresistance, radioresistance, chromosomal instability, and disruption of cell junctions 42 .…”

“…The magnitude of pH gradient reversal in epithelial cancer cells can be enhanced through Collagen‐I/Fibronectin/Integrin‐β1/Human Ether‐àgo‐go‐related Gene‐1 (hERG‐1)/NHE1 pathway 44 . Since the senescence of stromal fibroblasts produces increased amounts of collagen and fibronectin, it will further promote epithelial malignancy through this pathway.…”