LIM kinase inhibition reduces breast cancer growth and invasiveness but systemic inhibition does not reduce metastasis in mice
Metastasis is the major cause of morbidity and mortality in cancer patients. An understanding of the genes that regulate metastasis and development of therapies to target these genes is needed urgently. Since members of the LIM kinase (LIMK) family are key regulators of the actin cytoskeleton and are involved in cell motility and invasion, LIMK is considered to be a good therapeutic target for metastatic disease. Here we investigated the consequences of LIMK inhibition on growth and metastasis of human and mouse mammary tumors. LIMK activity was reduced in tumor cells by expression of dominant-negative LIMK1, by RNA interference or with a selective LIMK inhibitor. The extent of phosphorylation of the LIMK substrate, cofilin, of proliferation and invasion in 2D and 3D culture and of tumor growth and metastasis in mice were assessed. Inhibition of LIMK activity efficiently reduced the pro-invasive properties of tumor cells in vitro. Tumors expressing dominant-negative LIMK1 grew more slowly and were less metastatic in mice. However, systemic administration of a LIMK inhibitor did not reduce either primary tumor growth or spontaneous metastasis. Surprisingly, metastasis to the liver was increased after administration of the inhibitor. These data raise a concern about the use of systemic LIMK inhibitors for the treatment of metastatic breast cancer.
KeywordsLIM kinase inhibitors Breast cancer Metastasis Actin cytoskeleton Therapy
Actin depolymerizing factor
Small interfering RNA
We thank Christina Restall for technical assistance and advice, Dr Bala Murthy for advice on FACS analysis, Dr. Roger Tsien for provision of the cherry fluorescent protein vector, Alison Gregg and Julia Morizzi for analysis of BMS3 levels in mice, Dr. Siddhartha Deb for pathology advice and Dr. Duncan Campbell for assistance with the statistical analysis. This work was supported by grants from the NIH (R21CA098229) and from the NHMRC of Australia, Fellowship support from NHMRC (OB) and from NBCF (Australia) (RLA). The authors acknowledge financial support from the Cancer Therapeutics CRC, established and supported under the Australian Government’s Cooperative Research Centre Program.
Conflict of interest
No potential conflicts of interest were disclosed.