Suppressing Effect of Na+/Ca2+ Exchanger (NCX) Inhibitors on the Growth of Melanoma Cells.

Zikai Liu,Mingke Song,Xiaoli Ma,Qing Cheng

doi:10.3390/ijms23020901

Zikai Liu, Mingke Song + Show 2 more

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https://doi.org/10.3390/ijms23020901

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Abstract

The role of calcium ion (Ca2+) signaling in tumorigenicity has received increasing attention in melanoma research. Previous Ca2+ signaling studies focused on Ca2+ entry routes, but rarely explored the role of Ca2+ extrusion. Functioning of the Na+/Ca2+ exchanger (NCX) on the plasma membrane is the major way of Ca2+ extrusion, but very few associations between NCX and melanoma have been reported. Here, we explored whether pharmacological modulation of the NCX could suppress melanoma and promise new therapeutic strategies. Methods included cell viability assay, Ca2+ imaging, immunoblotting, and cell death analysis. The NCX inhibitors SN-6 and YM-244769 were used to selectively block reverse operation of the NCX. Bepridil, KB-R7943, and CB-DMB blocked either reverse or forward NCX operation. We found that blocking the reverse NCX with SN-6 or YM-244769 (5–100 μM) did not affect melanoma cells or increase cytosolic Ca2+. Bepridil, KB-R7943, and CB-DMB all significantly suppressed melanoma cells with IC50 values of 3–20 μM. Bepridil and KB-R7943 elevated intracellular Ca2+ level of melanoma. Bepridil-induced melanoma cell death came from cell cycle arrest and enhanced apoptosis, which were all attenuated by the Ca2+ chelator BAPTA-AM. As compared with melanoma, normal melanocytes had lower NCX1 expression and were less sensitive to the cytotoxicity of bepridil. In conclusion, blockade of the forward but not the reverse NCX leads to Ca2+-related cell death in melanoma and the NCX is a potential drug target for cancer therapy.

Highlights

Melanoma, one of the most common skin malignancies, accounts for 1–3% of all malignant tumors [1,2]
We found that A2058, A375 and C8161 melanoma cells were markedly inhibited (43–88% reduction in viability) by 24-h incubation with bepridil; while HEML and HSF cells were much less affected by bepridil (11–18% reduction) (Figure 6A)
Little is known about the role of Na+/Ca2+ exchanger (NCX) in melanoma cells; it is of strong interest to study possible involvement of the NCX and analyze its therapeutic potential in melanoma [38,39]

Summary

Introduction

One of the most common skin malignancies, accounts for 1–3% of all malignant tumors [1,2]. Human melanoma cells express voltage-gated Ca2+ channels (VGCCs) from the families of the Cav, Cav, and Cav (T-type) [14]. The Cav isoforms was reported to promote progression of melanoma cell cycle and blockade of T-type channels increased apoptosis in malignant melanoma [14,15]. The transient receptor potential melastatin (TRPM) channels such as TPRM8, TPRM2, and TPRM7 favor tumor progression through overexpression and hyperfunction in melanoma [18]. Previous melanoma Ca2+ signaling studies focused on Ca2+ entry and its molecular machinery, but rarely explored the role of Ca2+ extrusion mechanisms in tumor growth

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