Doxorubicin Promotes Migration and Invasion of Breast Cancer Cells through the Upregulation of the RhoA/MLC Pathway

Cancer cells develop acquired resistance induced by chemotherapeutic drugs. In this study, we investigated the effects of brief treatment with cytotoxic drugs on the phenotype of breast cancer cells. Breast cancer cells MCF7 and BT-474 were briefly treated with paclitaxel or doxorubicin. Clonogenic, migration, and invasion assays were performed on the treated cells. Western blot analysis and RhoA activity assay were also performed. Breast cancer cells when briefly treated with paclitaxel or doxorubicin showed reduced clonogenic ability. Doxorubicin, but not paclitaxel, augmented cell migration and invasion. The invasion-promoting effects of doxorubicin were lost when the two drugs were sequentially used in combination. Myosin light chain (MLC) 2 phosphorylation and RhoA activity were upregulated by doxorubicin and downregulated by paclitaxel. Pretreatment with RhoA inhibitors abolished the migration- and invasion-promoting effects of doxorubicin. Doxorubicin activates the RhoA/MLC pathway and enhances breast cancer cell migration and invasion. Therefore, this pathway might be explored as a therapeutic target to suppress anthracycline-enhanced tumor progression.