Abstract LB-347: Is PDX-1 a new universal molecular target for PDX-1 positive human cancer therapy? In vitro and in vivo evidence

Abstract

Introduction: Pancreatic and duodenal homeobox factor 1 (PDX-1) is a homeodomain-containing transcription factor, expression of which is specifically restricted to the islets and some endocrine cells of the duodenum and gastric antrum in adults. However, recent studies have revealed that over-expression of PDX-1 occurs in many different types of solid human cancer specimens including pancreatic, liver, prostate, ovarian, kidney, gastric, breast, and colon cancers by immunohistochemical analysis. It is not clear whether PDX-1 could serve as a universal therapeutic target for any PDX-1 positive cancer types besides pancreatic cancer. Here we report the anti-cancer effects of PDX-1 by suppressing the expression of PDX-1 with synthetic siRNA and virus-expressed shRNA in different type of PDX-1 positive cancers in vitro and in vivo. Method and Materials: Human cancer cells (3 pancreatic, 4 breast, 2 prostate, 1 ovary, 1 liver, 1 cervical, 1 nasopharyngeal) and 2 non-cancer human cells were employed to determine the expression of hPDX-1 by quantitative real-time RT-PCR and Western Blotting. PDX-1 siRNAs targeting different human PDX-1 sites and negative control siRNA were synthesized by Dharmacon and transfections were performed ont the cell cultures mentioned above. shRNA transfections were mediated by Lentivirus and Adenovirus vectors. Apoptosis assay was carried out using Annexin V labeling kit by FACS. In vivo anti-cancer procedure: Nude mice bearing different human cancers were intra-tumorly administrated PDX-1 shRNA-expressing adenovirus (107 PFU every other 2 days for 2 weeks) and the tumor size was measured at different times and the tumor weight was weighed after another 2 weeks. Results: PDX-1 over-expression in different human cancer cell was revealed by real-time RT-PCR as compared with non-cancer control cells. By using both synthetic PDX-1 siRNA and Lentivirus mediated shRNA, PDX-1 was effectively suppressed as determined by RT-PCR and Western Blot analysis. Significant cell apoptosis was induced consequently as measured with Annexin V-FACS assay in vitro in various types of human cancers, such as pancreas, liver, prostate, ovarian, and breast cancers, but not in non-cancer control cells. After intra-tumor administrated PDX-1 shRNA-expressing adenovirus in human ovarian and prostate cancer xenograft mice in vivo, a significant tumor shrink (97.05% Inhibitory rate, p <0.05) was observed as compared with negative control and blank control. Conclusion: PDX-1 over-expression was found in various types of human cancers at different levels and silencing PDX-1 expression by a RNA interference resulted in cancer cell specific apoptosis thereby indicating the anti-cancer effects of PDX-1 in vitro and in vivo. Our results suggested that PDX-1 might be an effective and universal molecular target for various types of PDX-1 positive human cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-347.