Simultaneous Delivery of an Antisense Oligonucleotide and a Chemotherapeutic Agent by a Her2-Targeted Liposomal System

Treatment of cancer by chemotherapy almost invariably is limited by their toxicity to normal cells and tissues. A binary system, such as chemotherapeutic agents combining with antisense agents, can selectively destroy malignant cells by combining two modalities, each of which individually has minimal toxicity, to produce a highly lethal effect on tumor cells. In the meantime, the efficacy of chemotherapy of is sometimes limited by the development of resistance in cancer cells during treatment. For example, in breast cancer, this resistance is associated with the overexpression of Bcl-2 protein that activates antiapoptotic cellular defense. Antisense deoxyribonucleotides (As-ODNs) are a promising new class of agents for the treatment of cancers. G3139, a phosphorothioate ODN that suppresses the expression of the Bcl-2 oncogene, has shown significant efficacy when administered in combination with the fludarabine, doxorubicin, and G-CSF regimen to patients with leukemia and solid tumors such breast cancer in recent clinical trials. The amplification of HER2/neu gene and overexpression of HER2 protein have been observed in a number of tumors, especially in breast cancer and ovarian cancers, and have been known to remain stable in all tumor stages. The combination of overexpression of HER2 receptors in specific tumors and low expression of HER2 receptors in normal tissues provides a suitable therapeutic window for therapeutic agents targeting HER2, thereby minimizing damage to normal cells. In this project, a complex liposomal drug delivery system included the following components: (1) a nanoscale carrier—PEGylated liposomes; (2) a suppressor of apoptosis pathway—antisense oligonucleotide (As-ODN) targeted to Bcl-2; (3) an anticancer drug doxorubicin; and (4) a targeting moiety—herceptin (HER2 monoclonal antibody) coated on the surface of the liposomes which can lead liposomes to HER2-overexpressing cells will be constructed. We hypothesize that, by delivering the antisense agent and chemotherapeutic agent simultaneously through a HER2-targeted liposomal system, the efficacy of cancer treatment can be greatly enhanced due to the synergistic effect of doxorubicin (apoptosis inducer) and Bcl-2 As-ODN (apoptosis pathway suppressor). Selective targeting of breast cancer cells via the HER2 receptor should provide additional enhancement in the efficacy and therapeutic index of this treatment. This is a 3 year project and the Specific Aims are: Year 1 (Aim1) Aim 1.1. To design and evaluate strategies for optimizing incorporation an antisense agent (a Bcl-2 As-ODN) and a chemotherapeutic agent (doxorubicin) into HER2-targeted liposomes Aim 1.2. To evaluate in vitro properties of novel formulations of Bcl-2 As-ODN and doxorubicin based on HER2-targeted liposomes Year 2 (Aim2) Aim 2.1. To evaluate the release of Bcl-2 As-ODN and doxorubicin from liposomes and their intracellular localization. Aim 2.2. To mathematically model the intracellular trafficking of Bcl-2 As-ODN and doxorubicin from HER2-targeted liposomes. Year 3 (Aim3) Aim 3.1. To evaluate the in vitro cell growth inhibition and/or cytocidal effects following treatment with HER2-targeted or non-targeted liposomes containing Bcl-2 As-ODNs and doxorubicin in HER2-related cell lines. Aim 3.2. To evaluate the apoptosis effect of HER2-targeted liposomes containing Bcl-2 As-ODNs and chemotherapeutic agents in HER2-related cell lines