Non-canonical endogenous expression of voltage-gated sodium channel NaV1.7 subtype by the TE671 rhabdomyosarcoma cell line

Abstract

The human TE671 cell line was originally used as a model of medulloblastoma but has since been reassigned as rhabdomyosarcoma. Despite the characterised endogenous expression of voltage‐sensitive sodium currents in these cells, the specific voltage‐gated sodium channel (VGSC) subtype underlying these currents remains unknown. To profile the VGSC subtype in undifferentiated TE671 cells, endpoint and quantitative reverse transcription–PCR (qRT‐PCR), western blot and whole‐cell patch clamp electrophysiology were performed. qRT‐PCR profiling revealed that expression of the SCN9A gene was ∼215‐fold greater than the SCN4A gene and over 400‐fold greater than any of the other VGSC genes, while western blot confirmed that the dominant SCN9A RNA was translated to a protein with a molecular mass of ∼250 kDa. Elicited sodium currents had a mean amplitude of 2.6 ± 0.7 nA with activation and fast inactivation V₅₀ values of −31.9 ± 1.1 and −69.6 ± 1.0 mV, respectively. The currents were completely and reversibly blocked by tetrodotoxin at concentrations greater than 100 nm (IC₅₀ = 22.3 nm). They were also very susceptible to the Na_V1.7 specific blockers Huwentoxin‐IV and Protoxin‐II with IC₅₀ values of 14.6 nm and 0.8 nm, respectively, characteristic of those previously determined for Na_V1.7. Combined, the results revealed the non‐canonical and highly dominant expression of Na_V1.7 in the human TE671 rhabdomyosarcoma cell line. We show that the TE671 cell line is an easy to maintain and cost‐effective model for the study of Na_V1.7, a major target for the development of analgesic drugs and more generally for the study of pain.

Key points

Undifferentiated TE671 cells produce a voltage‐sensitive sodium current when depolarised.

The voltage‐gated sodium channel isoform expressed in undifferentiated TE671 cells was previously unknown.

Through qRT‐PCR, western blot and toxin pharmacology, it is shown that undifferentiated TE671 cells dominantly (>99.5%) express the Na_V1.7 isoform that is strongly associated with pain.

The TE671 cell line is, therefore, a very easy to maintain and cost‐effective model to study Na_V1.7‐targeting drugs.

Osthole induces apoptosis, suppresses cell-cycle progression and proliferation of cancer cells

BACKGROUND

The aim of the present study was to determine the effects of osthole on cell proliferation and viability, cell-cycle progression and induction of apoptosis in human laryngeal cancer RK33 and human medulloblastoma TE671 cell lines.

MATERIALS AND METHODS

Cell viability was measured by means of the MTT method and cell proliferation by the 5-bromo-2-deoxyuridine (BrdU) incorporation assay. Cell-cycle progression was determined by flow cytometry, and induction of apoptosis by release of oligonucleosomes to the cytosol. The gene expression was estimated by a quantitative polymerase chain reaction (qPCR) method. High-performance counter-current chromatography (HPCCC) was applied for isolation of osthole from fruits of Mutellina purpurea.

RESULTS

Osthole decreased proliferation and cell viability of cancer cells in a dose-dependent manner. The tested compound induced apoptosis, increased the cell numbers in G1 and decreased cell number in S/G2 phases of the cell cycle, differentially regulating CDKN1A and TP53 gene expression depending on cancer cell type.

CONCLUSION

Osthole could be considered as a potential compound for cancer therapy and chemoprevention.