Abstract 2466: RON receptor tyrosine kinase as a targeting moiety for pancreatic cancer stem-like cells by antibody directed immunoliposomes for enhanced cytotoxicity

Pancreatic adenocarcinoma (PAC) is a malignant disease characterized by metastasis and chemo-resistance. Accumulated evidence has suggested that PAC malignancies arise due to functional presence of cancer stem cells that have high potential for self renewal, differentiation, and resistance to cytotoxic agents. Currently, therapeutics targeting PAC stem cells are not available. The study in this project describes a novel strategy and potential therapeutics targeting PAC stem cells for enhanced cytotoxicity. PAC stem like cells (PSLC) were obtained from human L3.6pl pancreatic cancer line under stem cell culture conditions. These cells show a typical sphere-like morphology in suspension and re-differentiate into epithelial appearance when subjected to serum inclusive adherent conditions. PSLC express transcription factor Bmi-1, a unique self-renewal marker, Aldh-1a, a metabolic enzyme expressed in stem-like cells, and cell-surface markers including CD24, CD44, and ESA as evidenced by Western blot and flow cytometry analyses. PSLC also displayed a phenotype characterized as epithelial to mesenchymal transition. Analysis of a panel of receptor tyrosine kinases has revealed that expression of EGFR, VEGFR, and MET was significantly reduced in PSLC. In contrast, RON receptor tyrosine kinase expression was sustained, which provides the molecular basis for antibody-directed approach for targeting PSLC. To achieve this goal, Zt/c9 monoclonal antibody was post-inserted onto doxorubicin liposomes to form anti-RON immunoliposomes (Zt/c9-Dox-IL). In vitro analysis indicated that; a) Zt/c9 was highly effective in inducing receptor internalization, which facilitates intracellular delivery of chemoagents; b) Zt/c9-Dox-IL was effective in killing Panc 0327 and L3.6pl PAC cells. An average of 7 fold decrease in IC50 value was obtained compared to control Dox-IL inserted with mouse IgG (mIgG-Dox-IL); and c) Zt/c9-Dox-IL displayed increased cytotoxicity against PSLC with the IC50 at 8 µM compared to 69 µM for mIgG-Dox-IL. In conclusion, PSLC enriched from L3.6pl cells display a phenotype similar to cancer stem cells with properties of increased self renewal and EMT. RON expression was maintained in PSLC, which was used as the drug delivery moiety for enhanced cytotoxicity. Increased PSLC cytotoxicity by Zt/c9-Dox-IL suggests that antibody-directed RON targeted delivery of cytotoxic agents is a rational approach for targeting PSLC to achieve enhanced cytotoxicity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2466. doi:10.1158/1538-7445.AM2011-2466