Metastasis and resistance to chemotherapy account for the majority of causes of treatment failure; thus, we have three aims in this study: 1) to establish clinical relevance of phospho-MARCKS in breast cancer; 2) to characterize the functional roles of phospho-MARCKS in response to chemotherapy in vitro; and 3) to determine whether pharmacological inhibition of MARCKS by the MANS peptide improves paclitaxel efficacy in vivo. Here, MARCKS is linked to breast carcinoma.