Molecular targeting of drug delivery systems to ovarian cancer by BH3 and LHRH peptides

Novel targeted proapoptotic anticancer drug delivery systems were developed and evaluated. Poly(ethyleneglycol) (PEG) conjugates were used as carriers. Camptothecin (CPT) was used as an anticancer agent–apoptosis inductor. Two types of molecular targets were investigated: (1) an extracellular membrane receptor specific to ovarian cancer and (2) intracellular controlling mechanisms of apoptosis. Synthetic peptides similar to luteinizing hormone-releasing hormone (LHRH) and BCL-2 homology 3 (BH3) peptide were used as a targeting moiety and a suppressor of cellular antiapoptotic defense, respectively. Three different conjugates (CPT–PEG, CPT–PEG–BH3 and CPT–PEG–LHRH) were synthesized and examined in A2780 human ovarian cancer cells. Cytotoxicity, expression of genes encoding BCL-2, BCL-XL, SMAC, APAF-1 proteins and caspases 3 and 9, the activity of caspases 3 and 9 and apoptosis induction were studied. Taken together the results indicate much higher cytotoxicity and apoptosis-inducing activity of PEG–CPT conjugates when compared to free CPT. Moreover, the effects of targeted CPT–PEG–BH3 and CPT–PEG–LHRH conjugates were more pronounced than the non-targeted PEG–CPT conjugate. The results confirmed the feasibility of this new two-tier molecular targeting strategy for enhancing the efficacy of cancer chemotherapy.