Iron depletion results in Src kinase inhibition with associated cell cycle arrest in neuroblastoma cells.

Gamini Siriwardana,Paul A Seligman

doi:10.14814/phy2.12341

Abstract

Iron is required for cellular proliferation. Recently, using systematic time studies of neuroblastoma cell growth, we better defined the G1 arrest caused by iron chelation to a point in mid-G1, where cyclin E protein is present, but the cyclin E/CDK2 complex kinase activity is inhibited. In this study, we again used the neuroblastoma SKNSH cells lines to pinpoint the mechanism responsible for this G1 block. Initial studies showed in the presence of DFO, these cells have high levels of p27 and after reversal of iron chelation p27 is degraded allowing for CDK2 kinase activity. The initial activation of CDK2 kinase allows cells to exit G1 and enter S phase. Furthermore, we found that inhibition of p27 degradation by DFO is directly associated with inhibition of Src kinase activity measured by lack of phosphorylation of Src at the 416 residue. Activation of Src kinase occurs very early after reversal from the DFO G1 block and is temporally associated with initiation of cellular proliferation associated with entry into S phase. For the first time therefore we show that iron chelation inhibits Src kinase activity and this activity is a requirement for cellular proliferation.

Highlights

Iron is required for cellular proliferation, rapidly growing cells including cancer cells (Robbins and Pederson 1970; Rudland et al 1977; Kontoghiorghes et al 1986; Le and Richardson 2002)
After SKNSH cells are released from the G1 block caused by iron chelation (DFO treatment), there is significantly increased phosphorylation of CDK2 starting at about 15 min after reversal, this increase continues for about 1–2 h and levels off or decreases at 2–4 h (Fig. 1A and data not shown)
The activation of CDK2 allows for synthesis of specific proteins for cells to proceed through G1/S phase and enter S phase

Summary

Introduction

Iron is required for cellular proliferation, rapidly growing cells including cancer cells (Robbins and Pederson 1970; Rudland et al 1977; Kontoghiorghes et al 1986; Le and Richardson 2002). A chelator that has been considered the “gold standard” for treatment of iron overload, new iron chelators are more practical (i.e., oral absorption) but have improved iron chelation efficacy, and are lipophilic potentially affecting other biologic processes. These agents may well have more potential for cancer treatment including in combination with chemotherapy (Yu et al 2012; Lui et al 2013; Potuckova et al 2014)

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Results

Conclusion