Small-cell lung cancer (human): potentiation of endocytic membrane activity by voltage-gated Na(+) channel expression in vitro

The possible functional role of voltage-gated Na+ channel (VGSC) expression in controlling endocytic membrane activity in human small-cell lung cancer (SCLC) cell lines (H69, H209, H510) was studied using uptake of horseradish peroxidase (HRP). The normal human airway epithelial (16HBE14o) cell line was used in a comparative approach. Uptake of HRP was vesicular, strongly temperature-sensitive and suppressed by cytoskeletal poisons (cytochalasin D and colchicine), consistent with endocytosis. Compared with the normal cells, HRP uptake into SCLC cells was kinetically more efficient, resulting in more than four-fold higher uptake under optimized conditions. Importantly, HRP uptake into SCLC cells was inhibited significantly by the specific VGSC blocker tetrodotoxin, as well as lidocaine and phenytoin. These effects were dose-dependent. None of these drugs had any effect on the uptake into the 16HBE14o cells. Uptake of HRP into SCLC cells was reduced by ∼66% in Na+-free medium and was partially (∼30%) dependent on extracellular Ca2+. The possibility that the endocytic activity in the H510 SCLC cells involved an endogenous cholinergic system was investigated by testing the effects of carbachol (a cholinergic receptor agonist) and eserine (an inhibitor of acetylcholinesterase). Both drugs inhibited HRP uptake, thereby suggesting that basal cholinergic activity occurred. It is concluded that VGSC upregulation could enhance metastatic cell behavior in SCLC by enhancing endocytic membrane activity

An acetylcholinesterase-derived peptide inhibits endocytic membrane activity in a human metastatic breast cancer cell line

Acetylcholinesterase (AChE) is well established as having non-cholinergic functions and is also expressed in breast tumours where its function(s) is not known. Recently, a candidate peptide sequence towards the C-terminal of the AChE molecule has been identified, as the salient site remote from normal catalysis in neurons, and possibly other cells. The main aim of this study was to explore the possibility that ‘AChE-peptide’ might also affect human breast cancer cells. Uptake of the non-cytotoxic tracer horseradish peroxidase (HRP) was used as an index of endocytosis, a key component of the metastatic cascade, representing exocytosis/secretory membrane activity and/or plasma membrane protein turnover. AChE-peptide had no affect on the weakly metastatic MCF-7 human breast cancer cell line. By contrast, application of AChE-peptide to the strongly metastatic MDA-MB-231 cells resulted in a dose-dependent inhibition of HRP uptake; treatment with a scrambled variant of the peptide of comparable amino acid length was ineffective. The action of AChE-peptide was suppressed by lowering the extracellular Ca2+ concentration and co-applying a selective antagonist of α7, but not α4/β2, nicotinic receptor. The results suggest that AChE-peptide has a novel, selective bioactivity on breast cancer cells and can potentiate metastatic cell behaviour

Principles of microelectrode techniques

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The expression and functional characterization of sigma (sigma) 1 receptors in breast cancer cell lines

Sigma (σ) receptors have been implicated in cancer. However, to date there is little molecular data demonstrating the role of σ1 receptors in cancer. Expression of σ1 receptors in various human cancer cell lines in comparison to non-cancerous cell lines was investigated, using real time RT-PCR and by western blotting with a σ1 receptor specific antibody. Our results indicate that cancer cells express higher levels of σ1 receptors than corresponding non-cancerous cells. Localization of the σ1 receptor was investigated in MDA-MB-231 cells by immunocytochemistry and confocal microscopy, expression was visualized predominantly at the cell periphery. We have tested the effect of σ1 and σ2 drugs and a σ1 receptor silencing construct on various aspects of the metastatic process on two breast cell lines of different metastatic potential and a normal breast cell line. Both σ1 and σ2 drugs and the σ1 receptor silencing construct had effects on proliferation and adhesion for breast cancer cell lines, compared to a non-cancerous breast cell line. This data suggests σ1 receptor plays a role in proliferation and adhesion of breast cancer cells. Therefore, it is likely to be a potential target for the diagnosis and therapy of breast cancer