Therapeutic targeting of voltage-gated sodium channel NaV1.7 for cancer metastasis

Abstract

This review focuses on the expression and function of voltage-gated sodium channel subtype Na_V1.7 in various cancers and explores its impact on the metastasis driving cell functions such as proliferation, migration, and invasiveness. An overview of its structural characteristics, drug binding sites, inhibitors and their likely mechanisms of action are presented. Despite the lack of clarity on the precise mechanism by which Na_V1.7 contributes to cancer progression and metastasis; many studies have suggested a connection between Na_V1.7 and proteins involved in multiple signaling pathways such as PKA and EGF/EGFR-ERK1/2. Moreover, the functional activity of Na_V1.7 appears to elevate the expression levels of MACC1 and NHE-1, which are controlled by p38 MAPK activity, HGF/c-MET signaling and c-Jun activity. This cascade potentially enhances the secretion of extracellular matrix proteases, such as MMPs which play critical roles in cell migration and invasion activities. Furthermore, the Na_V1.7 activity may indirectly upregulate Rho GTPases Rac activity, which is critical for cytoskeleton reorganization, cell adhesion, and actin polymerization. The relationship between Na_V1.7 and cancer progression has prompted researchers to investigate the therapeutic potential of targeting Na_V1.7 using inhibitors. The positive outcome of such studies resulted in the discovery of several inhibitors with the ability to reduce cancer cell migration, invasion, and tumor growth underscoring the significance of Na_V1.7 as a promising pharmacological target for attenuating cancer cell proliferation and metastasis. The research findings summarized in this review suggest that the regulation of Na_V1.7 expression and function by small molecules and/or by genetic engineering is a viable approach to discover novel therapeutics for the prevention and treatment of metastasis of cancers with elevated Na_V1.7 expression.

Keywords: Nav1.7; cancer; cell invasion; cell migration; cell viability; metastasis; therapeutic targeting; voltage-gated sodium channel.

FIGURE 1

General structure of voltage-gated sodium channel. (A) The structure of VGSC consists of an α subunit with four homologous Domain (DI-DIV) and one or two β auxiliary subunits. (B) TTX-sensitive and TTX-resistant voltage-gated sodium channels. (C) Construction of the α subunit. Each Domain of the α-subunit consists of six transmembrane segments. S1-S4 are a part of the voltage sensing domain and S5-S6 are a part of the pore forming domain (PD). (D) Pore forming domain is divided into five regions i) an extracellular loop (ECL); ii) a selectivity filter (SF); iii) a central cavity (CV) which contains fenestration sites (F); iv) an intracellular activation gate (G); and v) the region beneath the intracellular gate (BIG). Structure figures were prepared in PyMol 2.4.2 from the PDB 8thh (Wu et al., 2023)

FIGURE 2

Na_V1.7 binding sites for different inhibitors. (A) Most inhibitors occupy the CV region of the central pore of the channel. The CV site inhibitors, HDA (orange stick, PDB 8j4f), VXT (hot pink stick, PDB 8i5y), RLZ (beige stick, PDB 8thg), and VPC (purple stick, PDB 8i5x). (B) Peptide toxin, m3-HwTx-IV (pink surface) bound at VSDII, PDB 7k48. (C) Sodium channel blockers, TTX (pale cyan stick, PDB 6j8j) and STX (brown stick, PDB 6j8h) block the selectivity filter. (D) Na_V1.7 selective inhibitors PF05089771 (magenta stick, PDB 8i5g) and GX-936 (cyan stick, PDB 5ek0) bind at VSDIV. (E) BPV (light pink stick, PDB 8i5b) and CBZ (blue stick, PDB 8s9c) are located at the BIG site. LCM (gray sticks, PDB 8s9b) and LTG (green sticks, PDB 8thh) is a dual-inhibitor binding to both CV region and BIG site. This figure was prepared in PyMol 2.4.2.

FIGURE 3

Structures of compounds used in the studies of Na_V1.7 in cancers.

FIGURE 4

Na_V1.7 activity is proposed to influence the cancer cell functions such as cell growth, survival, proliferation, and motilities through multiple pathways. i) Intracellular influx of Ca²⁺ ions through the reverse mode of NCX (3:1, Na⁺: Ca²⁺ (Malcolm et al., 2023)). Na_V1.7 activity increases the intracellular concentration of Na⁺, which promotes Ca²⁺ influx through NCX reverse mode, thus initiating PKA formation through the activated AC. PKA induces actin polymerization by phosphorylation of CIP4, a crucial factor coordinated with an actin polymerization. ii) EGF/EGFR and HGF/c-MET pathway. EGF/EGFR induces the upregulation of Na_V1.7 expression and enhances the metastasis driving cell functions through ERK1/2 signaling. Evidence showed that ERK1/2 is a downstream target of EGF/EGFR and HGF/c-MET pathway. It could facilitate migration and invasion by regulating the activity of MMPs, iii) Phosphorylation of p38. Na_V1.7 activity reduces the phosphorylation of p38, which increases the binding of NF-κB p65 to the MACC1 promoter region resulting in an increase of MACC1 expression. The activation of ERK1/2 via HGF/c-MET pathway could also modulate the NF-κB signaling. iv) NHE-1 expression. The expression of NHE-1 depends upon the expression of MACC1, for which c-MET is the transcriptional target. The c-MET binding to HGF activates the interaction of c-Jun with the promoter region of SLC9A1 to initiate the synthesis of NHE-1. v) Intracellular Na⁺ ion concentration. An Increase in the intracellular concentration of Na⁺ triggers H⁺ efflux through NHE-1 (1:1, Na⁺:H⁺ (Liskova et al., 2019)) leading to an increase in the acidity of ECM environment enhancing MMPs secretion and ECM degradation. NHE-1 activation may also have resulted from the contribution of Warburg effect associated with MACC1. vi) Rho GTPases activity. The regulation of Na_V1.7 could indirectly increase the Rho GTPases activity. Na_V1.7 activity causes membrane depolarization and induces Ca²⁺ ion entry through the activation of Cavs and/or reverse-mode NCX, subsequently increase the expression of RhoA and Rac1 to facilitate cell motility by activating Cofilin-1 and Fascin, which are crucial for actin polymerization. Na_V1.7 activity may enhance Src kinase activity, promoting actin polymerization, cytoskeleton reorganization, and invadopodia formation. Both EGF/EGFR and the activation of HGF/c-MET can activate Src kinases. Src-mediated cancer cell invasion and migration occur through the activation of Rac1. Figure created with BioRender.com.