Acquired resistance of pancreatic cancer cells towards 5-Fluorouracil and gemcitabine is associated with altered expression of apoptosis-regulating genes.
OBJECTIVE
Resistance to chemotherapy is a major cause of treatment failure and poor prognosis in pancreatic cancer. Inasmuch as most effects of chemotherapeutic agents are mediated via the activation of apoptosis, the cytotoxic effects of gemcitabine and 5-fluorouracil (FU) in correlation with apoptosis-regulating genes in pancreatic cancer cell lines were analyzed.


METHODS
The cytotoxic effects of 5-FU and gemcitabine in AsPC-1, Capan-1, Mia-PaCa-2 and T3M4 pancreatic cancer cell lines were assessed by growth assays, and mRNA expression levels of pro-apoptotic and anti-apoptotic genes of the Bcl-2 family were analyzed by RNAse protection assays.


RESULTS
Pancreatic cancer cells displayed a wide range of responses towards 5-FU (IC(50) 0.22-4.63 microM) and gemcitabine (11.51-42.2 nM). After repeated treatment with 5-FU, the IC(50) values in Capan-1 and T3M4 cells increased 2.1- and 1.8-fold, respectively, compared to their parental cells. Following recurrent treatment with gemcitabine, the IC(50) values in Capan-1 cells increased significantly (1.5-fold, p < 0.01). RNase protection assay showed a negative correlation between bcl-x(L) and mcl-1 mRNA expression levels and the sensitivity to 5-FU and gemcitabine after 5-FU and gemcitabine treatment. The bax/bcl-2 ratio maintained relatively stable following 5-FU/gemcitabine treatment and reflected the chemotherapeutic sensitivity of these cell lines.


CONCLUSIONS
These findings reveal that pancreatic cancer cell lines are generally resistant to 5-FU and are more sensitive towards gemcitabine. The bax/bcl-2 ratio is predictive of chemotherapy sensitivity, whereas bcl-x(L) and mcl-1 mRNA levels following repeated exposure to 5-FU or gemcitabine are associated with resistance to these drugs. These findings suggest that the activation of anti-apoptotic genes after repeated drug exposure contributes to chemoresistance of pancreatic cancer cells and that blockage of anti-apoptotic genes might enhance chemosensitivity in pancreatic cancer.
Shi
Xin
X
Department of Visceral and Transplantation Surgery, Inselspital, University of Bern, Switzerland.
Liu
Shengli
S
Kleeff
Jörg
J
Friess
Helmut
H
Büchler
Markus W
MW
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000235:genetics*; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D011379:Prognosis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012235:Rhodamines / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D051020:bcl-X Protein; D000093542:Gemcitabine
C494811:BCL2L1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012235:Rhodamines; D051020:bcl-X Protein; D003841:Deoxycytidine; C022027:lissamine rhodamine B; D012259:Ribonuclease, Pancreatic; D005472:Fluorouracil; D000093542:Gemcitabine