Inhibition of primary and metastatic tumors in mice by E-selectin-targeted polymer-drug conjugates.

There is currently no effective means to prevent or control metastatic dissemination of cancer cells. E-selectin, an adhesion molecule expressed exclusively on inflamed and angiogenic blood vessels, plays an important role in several rate-limiting steps of cancer metastasis. In this study, we assessed the in vivo antitumor efficacy of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers conjugated to an E-selectin binding peptide (Esbp, DITWDQLWDLMK) and equipped with the chemotherapeutic drug doxorubicin (P-(Esbp)-DOX) or with the proapoptotic peptide D(KLAKLAK)2 (P-(Esbp)-KLAK). Following a single intravenous injection, P-(Esbp)-DOX reduced tumor growth rate and prolonged the survival of mice bearing primary Lewis lung carcinoma (3LL) tumors significantly more than treatment with a non-targeted copolymer (P-DOX) or with free DOX. In an experimental B16-F10 lung metastasis model, a single intravenous dose of P-(Esbp)-DOX or P-(Esbp)-KLAK prolonged mice survival time significantly more than the non-targeted copolymers or the free drugs, and the percentage of complete tumor regression increased with increasing doses and with dosing frequency. In addition, mice pretreated with an E-selectin-targeted "drug-free" copolymer (P-(Esbp)-FITC) exhibited significantly fewer B16-F10 tumor foci in the lungs as compared with non-treated mice, demonstrating the anti-metastatic properties of the copolymer and its ability to control cancer spread through E-selectin-mediated interactions. Biodistribution analysis further confirmed the preferential accumulation of the E-selectin-targeted near-infrared fluorescently-labeled copolymer P-(Esbp)-IR783 in B16-F10 lung metastases. Taken together, this study demonstrates, for the first time, that the E-selectin targeted copolymer-drug conjugates can inhibit primary tumor growth and prevent metastases in vivo.