Studies on the Gemcitabine Resistance of Pancreatic Cancer

다국어 초록 (Multilingual Abstract)

Resistance to gemcitabine is a major obstacle in the treatment of advanced pancreatic cancer. Although efforts to overcome gemcitabine resistance have been underway, the outcomes have not been satisfactory. To enhance therapeutic efficacy, understanding of biochemical mechanisms of gemcitabine resistance is prerequisite. Gemcitabine resistant cells may alter the dependency on several key kinases to facilitate cell proliferation and survival. Thus, searching the bypass of biochemical pathways in gemcitabine resistant cells may be achieved by the comparison of sensitivities on protein kinase inhibitors (PKIs) between parental and gemcitabine resistant cells. Comparison of cell viability of parental and gemcitabine resistant cell on 84 PKIs revealed that 16 PKIs exhibited high scores (EC50 ratio >1.4) and 18 PKIs showed low scores (EC50 ratio <0.6). These results suggest that PI3K/AKT/mTOR, DNAPK, and AMPK pathway might be potential target for the enhancement of gemcitabine treatment. According to previous finding that blocking transforming growth factor-β (TGFß) signal enhances the efficacy of gemcitabine in pancreatic cancer cells, the combinational effects of TGFß receptor I (TßRI) inhibitors, SB431542 and SB525334 with gemcitabine were determined. Combination with TβRI inhibitors significantly augmented the cytotoxicity of gemcitabine in both parental and gemcitabine resistant pancreatic cancer cells. SB525334 significantly increased apoptotic cell death in gemcitabine-resistant cells. Treatment of SB525334 also reduced AKT signal pathway, which plays crucial role in gemcitabine resistance. Migration assay also revealed that blocking TβRI reduces cell migration. Therefore, chemotherapeutic approaches using SB525334 might also enhance the treatment benefit of the gemcitabine-containing regimens in the treatment of pancreatic cancer patients.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• Ⅱ. Material and Methods 3
• 1.Cell culture and reagents 3
• 2.Generation of gemcitabine resistant cells 3
• 3.Cell viability and drug combination 3
• 4.Western blotting 4
• 5.Caspase 3/7 assay 5
• 6.Transfection of siRNA 5
• 7.Cell migration assay 5
• Ⅲ. Results 7
• 1.Exploration of protein kinase inhibitor to identify signaling pathways, which is indispensible to gemcitabine resistance 7
• 2.Transforming growth factor beta receptor I inhibitor sensitizes drug resistant pancreatic cancer cells to gemcitabine 8
• Ⅳ. Discussion 21
• References 24
• Abstract in Korean 28