1. ¹Children's Cancer Institute Australia for Medical Research, Randwick, New South Wales, Australia
2. ²University of New South Wales, Sydney, New South Wales, Australia
3. ³St Vincent's Institute of Medical Research, Melbourne, Victoria, Australia
4. ⁴Department of Medicine, St Vincent's Hospital, Melbourne, Victoria, Australia

Correspondence: Dr M Kavallaris, Pharmacoproteomics Program, Children's Cancer Institute Australia for Medical Research, PO Box 81, Randwick, New South Wales 2031, Australia. E-mail: m.kavallaris@ccia.unsw.edu.au

Received 8 February 2009; Revised 18 September 2009; Accepted 23 September 2009; Published online 2 November 2009.

Abstract

LIM-kinase 2 (LIMK2) belongs to the LIMK family of proteins, which comprises LIMK1 and LIMK2. Both proteins regulate actin polymerization through phosphorylation and inactivation of the actin depolymerizing factor cofilin. In this study, we show that the level of LIMK2 protein is increased in neuroblastoma, BE(2)-C cells, selected for resistance to microtubule-destabilizing agents, vincristine and colchicine. However, the level of phosphorylated LIMK1 and LIMK2 was similar in the resistant and parental BE(2)-C cells. In contrast, the level of phospho-cofilin was greatly increased in the drug-resistant cells. Downregulation of LIMK2 expression increases sensitivity of neuroblastoma SH–EP cells to vincristine and vinblastine but not to microtubule-stabilizing agents, while it's overexpression increased its resistance to vincristine. Its vincristine-induced mitotic arrest was moderately inhibited in the LIMK2 knockdown cells, suggesting that the increased drug sensitivity is through an alternative mechanism other then mitotic arrest and apoptosis. Moreover, downregulation of LIMK2 expression induces formation of abnormal mitotic spindles, an effect enhanced in the presence of microtubule-destabilizing agents. LIMK2 is important for normal mitotic spindle formation and altered LIMK2 expression mediates sensitivity to microtubule destabilizing agents. These findings suggest that inhibition of LIMK2 activity may be used for the treatment of tumors resistant to microtubule-destabilizing drugs.