Elsevier

Brain Research

Volume 744, Issue 2, January 1997, Pages 199-206
Brain Research

Suramin disrupts insulin-like growth factor-II (IGF-II) mediated autocrine growth in human SH-SY5Y neuroblastoma cells

https://doi.org/10.1016/S0006-8993(96)01078-5Get rights and content

Abstract

Suramin, traditionally used in the treatment of trypanosomiasis, is under investigation in the treatment of cancer. One side effect that limits its use is the onset of a sensorimotor polyneuropathy. In order to investigate the mechanism by which suramin induces polyneuropathy, we examined its effects on SH-SY5Y human neuroblastoma cells, an in vitro model of neuronal growth and differentiation. Addition of 50–400 μg/ml suramin to SH-SY5Y cells grown in 0.6% CS inhibited [3H]thymidine ([3H]TdR) incorporation and cell growth. Upon removal of suramin, [3H]TdR incorporation increased, demonstrating that levels of suramin used were cytostatic and not cytotoxic. Analysis of suramin-treated SH-SY5Y cells by flow cytometry revealed growth arrest in the G1/G0 phase of the cell cycle. IGF-II-induced SH-SY5Y growth is mediated by the type I IGF receptor (IGF-IR). Therefore, we examined its effect on IGF-IR tyrosine phosphorylation. Suramin prevented IGF-II-stimulated IGF-IR tyrosine phosphorylation. These results indicate that in SH-SY5Y cells, suramin acts as a cytostatic agent and can block IGF-II-dependent cell growth by preventing IGF-IR activation. Thus, suramin toxicity in the peripheral nervous system may be due, in part, to preventing IGFs and other growth factors from activating their receptors.

Introduction

Suramin, a polysulfonated naphthylurea, was initially used in the treatment of trypanosomiasis and onchocerciasis [62]. Suramin inhibits the activity of reverse transcriptase [12,48] and DNA polymerase [26,48], as well as interrupting cell cycle progression [2,18] and the actions of several growth factors [2,3,8,15,29,61]. The cellular effects of suramin have lead to its clinical use in the treatment of HIV infection [5,62] as well as several cancers including prostate [27], thymoma [31] gliosarcoma [46] and renal cell carcinoma [45].

A consistent consequence of suramin treatment has been the development of mild to severe polyneuropathy [5,6,9,32,56]. The mechanism underlying suramin neuro-toxicity is not clear; however, several lines of evidence suggest suramin-coupled neuropathy could be due to blunted or altered neurotrophism. Suramin blocks the actions of growth factors that are essential to the maintenance of the peripheral nervous system including nerve growth factor (NGF) [55], fibroblast growth factor (FGF) [2,4,58] and insulin-like growth factors I and II (IGF-I, IGF-II) [15,17,30,[50], [51], [52]].

The SH-SY5Y human neuroblastoma cell line provides a well-characterized model system to study the neurotoxic effects of suramin [35,36,57]. These cells ultrastructurally resemble developing sympathetic neurons [49], extend neu-rites [16], express functional cholinergic receptors [19] and voltage gated Na+ K+and Ca++ channels [19,25,54]. In preliminary studies, we have characterized SH-SY5Y growth in the absence of suramin. SH-SY5Y cells express both the type I and II IGF receptors [38] and secrete active IGF-II [36], which promotes autocrine growth via the type I IGF receptor [37,41]. Neuronal growth is associated with increased IGF-II mRNA and protein; growth arrest is paralleled by decreased IGF-II mRNA and protein [36,41]. Actual neuronal differentiation is characterized by altered c-myc and increased GAP-43 gene expression [35,57].

In the current study, we examine the effects of suramin on the growth of SH-SY5Y cells. We have found that suramin prevents IGF-II from activating the type I IGF receptor (IGF-IR). This interruption leads to an inhibition of SH-SY5Y growth, DNA synthesis and cell cycle progression. A similar disruption of growth factor support may be one mechanism by which suramin exerts its neurotoxic effects.

Section snippets

Materials

Cell culture supplies were purchased from Gibco BRC (Gaithersburg, MD). [3H]thymidine (6.7 Ci/mmol) was from NEN Dupont (Boston, MA). IGF-I was a gift from Dr. Elaine Alexander (Cephalon, West Chester, PA). IGF-II was purchased from Bachem (Torrance, CA). Unless indicated, all other chemicals were purchased from Sigma Chemical Co. (St. Louis, MO). Suramin was generously made available by Warner-Lambert, Parke-Davis (AnnArbor MI).

Cell culture

SH-SY5Y human neuroblastoma cells were kindly provided by Dr.

Inhibition of SH-SY5Y cell growth by suramin

To investigate some of the mechanisms of suramin neurotoxicity, we examined suramin's effects on SH-SY5Y human neuroblastoma cells, a well characterized in vitro model of neuronal growth and differentiation [35,36,57]. When grown in the presence of 0.6% CS, SH-SY5Y cells form confluent monolayers and extend long and complex neurites (Fig. 1A). Addition of suramin at doses of 200 and 400 μg/ml causes the cells to aggregate (Fig. 1B). We next determined the effect of suramin on the proliferation

Discussion

There are several potential etiologies that underlie the toxic polyneuropathy produced by suramin. For example, the observed neuropathy could be due to disruption of microtubule arrays resulting in decreased axonal transport; decreased neurotransmitter synthesis, disruption of membrane potential or loss of Schwann cell support. Each of these examples of nervous system dysfunction can be attributed to loss of growth factor support to neurons and/or glia. In the current study, we found suramin

Acknowledgements

The authors wish to thank Ann E. Randolph for technical assistance and James L. Beals for photographic and digital imaging assistance. Suramin was a generously made available by Warner Lambert-Parke Davis, Ann Arbor, MI. This work was supported by NIH Grants R29 NS32843 (E.L.F.) and NINDS T32 NS07222 (M.B.).

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