Antitumor effects of cecropin B-LHRH' on drug-resistant ovarian and endometrial cancer cells.

BACKGROUND: Luteinizing hormone-releasing hormone receptor (LHRHr) represents a promising therapeutic target for treating sex hormone-dependent tumors. We coupled cecropin B, an antimicrobial peptide, to LHRH', a form of LHRH modified at carboxyl-terminal residues 4-10, which binds to LHRHr without interfering with luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. This study aimed to assess the antitumor effects of cecropin B-LHRH' (CB-LHRH') in drug-resistant ovarian and endometrial cancers.

METHODS: To evaluate the antitumor effects of CB-LHRH', three drug resistant ovarian cancer cell lines (SKOV-3, ES-2, NIH:OVCAR-3) and an endometrial cancer cell line (HEC-1A) were treated with CB-LHRH'. Cell morphology changes were assessed using inverted and electron microscopes. In addition, cell growth and cell cytotoxicity were measured by MTT assay and LDH release, respectively. In addition, hemolysis was measured. Furthermore, radioligand receptor binding, hypersensitization and minimal inhibitory concentrations (against Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa, and Acinetobacter baumannii) were determined. Finally, the impact on tumor growth in BALB/c-nu mice was assessed in an ES-2 xenograft model.

RESULTS: CB-LHRH' bound LHRHr with high-affinity (dissociation constant, Kd = 0.252 ± 0.061 nM). Interestingly, CB-LHRH' significantly inhibited the cell viability of SKOV-3, ES-2, NIH:OVCAR-3 and HEC-1A, but not that of normal eukaryotic cells. CB-LHRH' was active against bacteria at micromolar concentrations, and caused no hypersensitivity in guinea pigs. Furthermore, CB-LHRH' inhibited tumor growth with a 23.8 and 20.4 % reduction in tumor weight at 50 and 25 mg/kg.d, respectively.

CONCLUSIONS: CB-LHRH' is a candidate for targeted chemotherapy against ovarian and endometrial cancers.