[The mechanism of resistance to 2', 2'-difluorodeoxycytidine (gemcitabine) in a pancreatic cancer cell line].
OBJECTIVE
To study the mechanism of resistance and its reversal to 2', 2'-difluorodeoxycytidine (gemcitabine) in a pancreatic cancer cell line SW1990.


METHODS
Immunohistochemistry and RT-PCR techniques were used to investigate the mechanism of drug resistance. Salvicine (SAL) was used to reverse the drug resistance in a gemcitabine-resistant pancreatic cancer cell line (SW1990-GEM). RT-PCR, flow cytometry and MTT assay were employed to evaluate the effect of reversing drug resistance by salvicine.


RESULTS
SW1990-GEM cells showed weak expression of P-glycoprotein (P-gp) revealed by immunohistochemistry, while its parental SW1990 cells were negative. Both cell lines did not express multidrug-resistance-related protein (MRP). As compared to the parental SW1990 cells, the mRNA expression of deoxycytidine kinase (dCK) was decreased while that of ribonucleotide reductase (RR) and mdr-1 was increased. With a concentration of 4 nmol/L, at one hr and 24 hr after SAL treatment, there was no change in mdr-1 mRNA expression, and the IC(50) of gemcitabine was 121.36 micromol/L and 121.64 micromol/L, respectively. However, when the concentration of SAL was increased to 30, 60, and 90 nmol/L, there was a dose-dependent down-regulation of mdr-1 mRNA expression in SW1990-GEM cells. The accumulation of rhodamine 123 was concomitantly increased, and the IC(50) of gemcitabine was correspondingly decreased.


CONCLUSIONS
The resistance to gemcitabine of a pancreatic cancer cell line is due to decreased expression of dCK and increased expression of RR and mdr-1. Salvicine, only in toxic concentrations, can reverse the drug resistance by down-regulating mdr-1 gene and P-gp expression.
Yao
Jie
J
Department of Medical Oncology, Cancer Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100021, China.
Feng
Feng-yi
FY
Lin
Chen
C
Zhang
Xue-yan
XY
Fu
Ming
M
Liang
Xiao
X
Yang
Ying
Y
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D045744:Cell Line, Tumor; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis / Q000235:genetics; D009285:Naphthoquinones / Q000494:pharmacology*; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000473:pathology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D000093542:Gemcitabine
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000964:Antimetabolites, Antineoplastic; D003841:Deoxycytidine; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009285:Naphthoquinones; D012333:RNA, Messenger; D000093542:Gemcitabine; C122096:salvicine; C421109:multidrug resistance-associated protein 1