Cyclopamine increases the cytotoxic effects of paclitaxel and radiation but not cisplatin and gemcitabine in Hedgehog expressing pancreatic cancer cells.
BACKGROUND
The hedgehog signaling pathway (Hh) is frequently over expressed in pancreatic adenocarcinomas. We studied the potential cytotoxic interactions between cyclopamine, a Hh pathway inhibitor and paclitaxel, cisplatin, gemcitabine and ionizing radiation (IR).


METHODS
In vitro clonogenic survival analysis was performed with cyclopamine alone or cyclopamine in combination with paclitaxel, gemcitabine, cisplatin and IR in Hh expressing human pancreatic tumor cells and Hh non-expressing colon cancer cells. Relative cytotoxicity was assessed in combination treatment compared with exposure to single agents. Assays of apoptosis (annexin V) were performed in the presence of cyclopamine, chemotherapeutic agents, and IR.


RESULTS
We report that cyclopamine increased the cytotoxic effects of paclitaxel and IR in Hh expressing pancreatic carcinoma cells. These effects were not observed in Hh non-expressing cells. Cyclopamine did not significantly increase killing by cisplatin or gemcitabine in Hh expressing pancreatic cancer cells.


CONCLUSIONS
These data suggest strategies to combine Hh inhibitors with radiotherapy and chemotherapeutic agents, specifically paclitaxel and related compounds in the treatment of pancreatic cancer.
Department of Surgery, University of Chicago, S Maryland Avenue, 5841, Chicago, IL 60637, USA.
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Z
Shafaee
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H
Schmidt
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W
Du
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M
Posner
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R
Weichselbaum
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002945:Cisplatin / Q000494:pharmacology*; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D045325:HCT116 Cells; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology*; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D011839:Radiation, Ionizing; D013997:Time Factors; D014704:Veratrum Alkaloids / Q000494:pharmacology*; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D053823:Hedgehog Proteins; D014704:Veratrum Alkaloids; D003841:Deoxycytidine; D017239:Paclitaxel; D002945:Cisplatin; C000541:cyclopamine; D000093542:Gemcitabine