Spontaneous and radiation-induced apoptosis in colorectal carcinoma cells with different intrinsic radiosensitivities: survivin as a radioresistance factor.
BACKGROUND
Spontaneous apoptosis has been shown to predict tumor response to radiochemotherapy in rectal cancer in vivo. It remains to be elucidated, however, which genetic profile determines whether a tumor is more or less prone to apoptosis. Recently, a novel member of the inhibitor of apoptosis protein family, designated survivin, was identified. We investigated the impact of survivin expression on tumor cell apoptosis in three colorectal cell lines of different intrinsic radiosensitivities.


METHODS
Survivin protein expression was measured by Western blot analysis, and survivin mRNA expression by quantitative TaqMan reverse transcription polymerase chain reaction, both in untreated cell and after irradiation with 2 and 8 Gy. The expression profile was then correlated to spontaneous and radiation-induced apoptosis (Tunel-Assay, DAPI-staining) in three colorectal cell lines of low (SW 480), intermediate (HCT-15), and high radiosensitivity (SW 48), as determined by the colony-forming assay.


RESULTS
In vitro analysis revealed higher spontaneous and higher radiation-induced apoptosis rates in the radiosensitive line (SW 48), as compared with the more resistant line (SW 480). In Western blot analysis and in TaqMan analysis, SW 480 was characterized by a higher spontaneous expression and a pronounced induction of survivin 48 h after irradiation, whereas survivin expression was low when untreated and not increased after irradiation in the most radiosensitive line SW 48. HCT-15 was intermediate, both with respect to the level of survivin mRNA and protein expression.


CONCLUSIONS
The inverse correlation of survivin-expression with spontaneous and radiation-induced apoptosis suggests that survivin is an important inhibitor of apoptosis in colorectal cancer cell lines. Analysis of survivin mRNA or protein expression may therefore provide predictive information on radio- and chemoresistance of individual colorectal tumors.
Rödel
Claus
C
Department of Radiation Oncology, University of Erlangen, Erlangen, Germany. claus.roedel@strahlen.med.uni-erlangen.de
Haas
Joachim
J
Groth
Anke
A
Grabenbauer
Gerhard G
GG
Sauer
Rolf
R
Rödel
Franz
F
D000230:Adenocarcinoma / Q000473:pathology*; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D015179:Colorectal Neoplasms / Q000473:pathology*; D004307:Dose-Response Relationship, Radiation; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D011836:Radiation Tolerance; D000077022:Survivin; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D014410:Tumor Stem Cell Assay
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D000077022:Survivin