Abstract
Gliomas are fast growing and highly invasive brain tumors, characterized by tumor microenvironment acidification that drives glioma cell growth and migration. Channels containing Acid-sensing Ion Channel 1a subunit (ASIC1a) mediate amiloride-sensitive cation influx in late stage glioma cells, but not in normal astrocytes. Thus, selective targeting of ASIC1a can be a perspective strategy for glioma treatment. Here, ASIC1a expression in U251 MG and A172 glioma cells, but not in normal astrocytes, was demonstrated. Recombinant analog of mambalgin-2 from black mamba Dendroaspis polylepis inhibited amiloride-sensitive currents at ASIC1a both in Xenopus laevis oocytes and in U251 MG cells, while its mutants with impaired activity towards this channel did not. Mambalgin-2 inhibited U251 MG and A172 glioma cells growth with EC50 in the nanomolar range without affecting the proliferation of normal astrocytes. Notably, mambalgin-2 mutants did not affect glioma cell proliferation, pointing on ASIC1a as the main molecular target of mambalgin-2 in U251 MG and A172 cells. Mambalgin-2 induced a cell cycle arrest, inhibited Cyclin D1 and cyclin-dependent kinases (CDK) phosphorylation and caused apoptosis in U251 MG and A172 cells. Moreover, mambalgin-2 inhibited the growth of low-passage primary cells from a patient with glioblastoma. Altogether, our data point to mambalgin-2 as a useful hit for the development of new drugs for glioma treatment.
Highlights
Gliomas are the most common brain tumors that originate from glial cells and are characterized by fast growth and high invasiveness
We demonstrated the functional expression of the mambalgin-2 inhibits these channels and growth of U251 MG and A172 glioma cells with EC50 in amiloride-sensitive Acid-sensing Ion Channel 1a subunit (ASIC1a) channels in glioma U251 MG cells, and showed that mambalgin-2 inhibits nanomolar range, but not of normal astrocytes
Our data suggest that mambalgin-2 inhibits the growth of glioma cells by an interaction with ASIC1a in the desensitized state, and the magnitude of the toxin’s antiproliferative effect correlates with a pH value of the cell environment (Figure 4a,e)
Summary
Gliomas are the most common brain tumors that originate from glial cells and are characterized by fast growth and high invasiveness. The ability of gliomas to proliferate in a dense environment of brain. Cancers 2020, 12, 1837 tissue is ensured by enhanced aerobic glycolysis and significant acidification of the tumor milieu [1]. 5.8 to 7.1, while median pH of normal patient brain tissue is about 7.1 [2,3]. Low pH of extracellular environment may lead to subsequent intracellular acidification, which drives tumor cell proliferation, metastasis and helps to escape anti-tumor immunity [4]. Tumor cells possess several pH-sensitive ion channels for the regulation of intracellular ion balance and support proliferation and cellular motility. ASICs are members of the degenerin/epithelial Na+ channel (DEG/ENaC) family activated by extracellular acidification [5,6]. ASICs are expressed in the nervous system and are involved in a wide range of physiological processes, including pain perception, synaptic plasticity, and memory, and are considered as potential therapeutic targets for the treatment of pain, and neurological and psychiatric diseases [5,7]
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