CXCR4-Targeted Necrosis-Inducing Peptidomimetic for Treating Breast Cancer

Triple-negative breast cancer is an aggressive subtype with a high recurrence rate, potential for metastasis, and a poor prognosis. The chemokine receptor, CXCR4, is a promising molecular target in breast cancer therapy. Here, we have developed a CXCR4-targeted antitumor peptidomimetic (named CTCE-KLAK), which is a fusion of the CXCR4 receptor antagonist CTCE-9908 and the D-form of proapoptotic peptide (KLAKLAK)₂, for the treatment of breast cancer. First, we investigated the in vitro antitumor activity of CTCE-KLAK against various breast cancer cells and noncancerous mammary epithelial cells. CTCE-KLAK showed cell-selective cytotoxicity and induced rapid necrotic cell death in breast cancer cells but not in normal cells. In contrast, unconjugated peptides such as the carboxylate analogues of CTCE-9908 and _D(KLAKLAK)₂ were not cytotoxic to these cells. The tumor selectivity of CTCE-KLAK for cytotoxic activity depends on its internalization into tumor cells. There was no cleavage of caspase-3, caspase-7, or PARP1 in CTCE-KLAK-treated cells. In addition, cell death by CTCE-KLAK was not prevented by z-VAD-fmk, a pan-caspase inhibitor that inhibits cisplatin-induced cell death. These data indicate that the CTCE-KLAK conjugate is a cell-selective inducer of necrosis. Furthermore, we evaluated the in vivo antitumor activity of CTCE-KLAK in the 4T1 mouse metastatic breast cancer model. Intravenous administration of CTCE-KLAK significantly inhibited tumor growth and lung metastasis. Together, these findings suggest that the necrosis-inducing peptidomimetic CTCE-KLAK is a promising CXCR4-targeted agent for treating triple-negative breast cancer.