Background: The presence of cancer stem cells in chemotherapy-resistant pancreatic cancer has not been demonstrated. In the present study, we aimed to identify and to characterize putative cancer stem cells (CSC) within different human pancreatic cancer cell lines as well as within 5-Fluorouracil-resistant pancreatic cancer cell lines established in our laboratory. Methods: Pancreatic CSC were identified and characterized by flow cytometry, using Hoechst 33342 dye staining. CSC from 5-FU-resistant cell lines were isolated by high-speed flow cell sorting (MoFlo) and the CSC self-renewal pathways were further analyzed by RT-PCR and Western blotting. Isolated CSC within 5-FU-resistant cell lines were exposed to the cancer stem cell targeted therapeutics (RAD001, Cyclopamine) and stained for Propidium iodide and BrdU. Furthermore, isolated CSC as well as non-tumorigenic cancer cells within 5-FU-resistant cell lines were orthotopically xenografted in nude mice and the efficacy of stem-cell-targeted therapy in combination with 5-FU was investigated. Results: Flow cytometry analysis revealed a significantly high amount of CSC in all chemotherapy-resistant cell lines. Combined 5-Fluorouracil IC50 and cancer stem cell targeted therapy resulted in the reduction of tumor cell proliferation independently on 5-FU-chemoresistance status, as detected by Propidium iodide and BrdU staining. In vivo the combination of 5-FU with cancer stem cell targeted therapeutics RAD001 or Cyclopamine significantly decreased the tumorigenic potential of CSC derived from 5-FU-resistant cell lines and dramatically reduced primary pancreatic tumor volume and weight. Conclusions: Our results demonstrate for the first time that chemotherapy-resistant cancer cells contain the increased CSC population (as compared to their parental sensitive cells) that is highly resistant to standard chemotherapy but not towards CSC-targeted therapy in vitro and in vivo. The further characterization of such cells might therefore lead to the development of new molecular and pharmaceutical therapeutics and better anti-cancer strategies.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 1071.

100th AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

American Association for Cancer Research
2009