title: Survivin as a radioresistance factor, and prognostic and therapeutic target for radiotherapy in rectal cancer.
abstract: Apoptosis levels have been shown to predict tumor response to preoperative radiochemotherapy in rectal cancer. Recently, the prominent role of survivin, a structurally unique member of the inhibitor of apoptosis protein family, has been shown in colorectal cancer tumorigenesis and prognosis. In this study, we investigated whether survivin plays a direct role in mediating radiation resistance. We used short interfering RNA molecules to decrease survivin in radioresistant SW480 and intermediately radioresistant HCT-15 colorectal cancer cells. This resulted in a significant decrease of survivin mRNA and protein expression with a maximum at 24 to 48 hours after transfection. If irradiated during this sensitive period, an increased percentage of apoptotic cells and an increased caspase 3/7 activity in parallel with a decreased cell viability and a reduced clonogenic survival was shown. These effects were more pronounced in the radioresistant SW480 cell line with a radiation-induced cytotoxicity enhancement factor at 10% and 50% survival of 1.8 to 2.2 for SW480 and 1.5 to 1.7 for HCT-15, respectively. Furthermore, transfection with survivin short interfering RNA increased levels of G2-M arrest and levels of DNA double-strand breaks in irradiated cells. These observations indicate that cell cycle and DNA repair mechanisms may be associated with apoptosis induction in tumor cells that are otherwise resistant to killing by radiation. In a translational study of 59 patients with rectal cancer treated with a combination of radiotherapy and chemotherapy, increased survivin expression was inversely related to the levels of apoptosis, and was also associated with a significantly higher risk of a local tumor recurrence.
authors.affiliation: Department of Radiation Oncology, Institutes of Clinical Immunology, and Pathology, University of Erlangen-Nuremberg, Erlangen, Germany. franz.roedel@strahlen.med.uni-erlangen.de
authors.forename: Franz
authors.initials: F
authors.lastname: Rödel
authors.forename: Jörg
authors.initials: J
authors.lastname: Hoffmann
authors.forename: Luitpold
authors.initials: L
authors.lastname: Distel
authors.forename: Martin
authors.initials: M
authors.lastname: Herrmann
authors.forename: Timmo
authors.initials: T
authors.lastname: Noisternig
authors.forename: Thomas
authors.initials: T
authors.lastname: Papadopoulos
authors.forename: Rolf
authors.initials: R
authors.lastname: Sauer
authors.forename: Claus
authors.initials: C
authors.lastname: Rödel
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000528:radiation effects; D048708:Cell Growth Processes / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D015536:Down-Regulation; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009363:Neoplasm Proteins; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000502:physiology; D000077022:Survivin; D014162:Transfection
chemical_list: C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077022:Survivin; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases