Bcl-X(L) antisense sensitizes human colon cancer cell line to 5-fluorouracil.
Resistance to 5-fluorouracil (5-FU) has been frequently found in the treatment of digestive tract cancer patients. Our previous study suggested that high expression of endogenous Bcl-X(L), might be associated with resistance to 5-FU in colorectal cancer. The aim of this study is to analyze the role of Bcl-X(L) in 5-FU resistance and to explore a new therapeutic strategy using Bcl-X(L) antisense. First, western blot analysis shows that Bcl-X(L) rather than Bcl-2 is overexpressed in primary adenocarcinoma of colon. Second, when Colo320 cells, with undetectable endogenous Bcl-XL expression, were transfected with Bcl-XL gene, they acquired high resistance to 5-FU. Finally, antisense oligodeoxynucleotides (ODNs) that targeted the start codon of Bcl-X(L) mRNA (AS1) prove to be the most effective in DLD1 cells with high endogenous Bcl-X(L) expression. Bcl-X(L) protein expression was decreased in a dose-dependent manner when the cells were treated with AS1 ODNs, while non-sense and sense controls and 5-FU had no effect on Bcl-X(L) protein. 5-FU treatment induced a level of apoptosis 10-fold higher in DLD1 cells than in untreated control cells, while the same dose of 5-FU induced a 55-fold higher level of apoptosis in DLD1 cells treated with Bcl-XL antisense oligodeoxynucleotides (P = 0.0003). Moreover, AS1 ODNs coupled with 5-FU decreased viable colon cancer cells 40% more than did 5-FU alone (P < 0.05). These results suggest that Bcl-X(L) is an important factor for 5-FU resistance and the suppression of Bcl-X(L) expression by the specific antisense ODNs can increase the sensitivity of colon cancer cells to 5-FU.
Nita
M E
ME
Department of Surgical Oncology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan. menitatky@hotmail.com
Ono-Nita
S K
SK
Tsuno
N
N
Tominaga
O
O
Takenoue
T
T
Sunami
E
E
Kitayama
J
J
Nakamura
Y
Y
Nagawa
H
H
D000230:Adenocarcinoma / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D003110:Colonic Neoplasms; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
D000964:Antimetabolites, Antineoplastic; C494811:BCL2L1 protein, human; D020319:Oligodeoxyribonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D005472:Fluorouracil