Metabotropic glutamate receptor 4-mediated 5-Fluorouracil resistance in a human colon cancer cell line.
OBJECTIVE
5-Fluorouracil (5-FU) has been the mainstay treatment for colorectal cancer for the past few decades. However, as with other cancers, development of 5-FU resistance has been a major obstacle in colorectal cancer chemotherapy. The purpose of this study was to gain further understanding of the mechanisms underlying 5-FU resistance in colorectal cancer cells.


METHODS
A 5-FU-resistant cell line was established from the human colon cancer cell line SNU-769A. Protein extracts from these two cell lines (parent and resistant) were analyzed using comparative proteomics to identify differentially expressed proteins.


RESULTS
5-FU-resistant human colon cancer cells were found to overexpress metabotropic glutamate receptor 4 (mGluR4). Other experiments showed cellular resistance to 5-FU (i.e., cell survival) was altered by the mGluR4 agonist l-2-amino-4-phosphonobutyric acid (L-AP 4), and by the mGluR4 antagonist (S)-amino-2-methyl-4-phosphonobutanoic acid (MAP 4), in that L-AP 4 increased 5-FU resistance in SNU-769A cells, whereas MAP 4 ablated 5-FU resistance in 5-FU-resistant cells. However, there was no significant effect of L-AP 4 or MAP 4 on basal cAMP and thymidylate synthase levels. Interestingly, 5-FU down-regulated mGluR4 expression, and MAP 4 suppressed proliferation in both cell lines.


CONCLUSIONS
We here report mGluR4 expression in human colon cancer cell line, which provides further evidence for extra-central nervous system expression of glutamate receptors. Overexpression of mGluR4 may tentatively be responsible for 5-FU resistance and, although activation by agonist promotes cell survival in the presence of 5-FU, decreased mGluR4 expression or inactivation by antagonist contributes to cell death.
Yoo
Byong Chul
BC
Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea.
Jeon
Eunkyung
E
Hong
Sung-Hye
SH
Shin
Young-Kyoung
YK
Chang
Hee Jin
HJ
Park
Jae-Gahb
JG
D000596:Amino Acids / Q000494:pharmacology; D000613:Aminobutyrates / Q000494:pharmacology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D016923:Cell Death; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D002945:Cisplatin / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000188:drug therapy*; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D015180:Electrophoresis, Gel, Two-Dimensional; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D008024:Ligands; D063065:Organophosphonates / Q000494:pharmacology; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism / Q000502:physiology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors
D000596:Amino Acids; D000613:Aminobutyrates; D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D018690:Excitatory Amino Acid Agonists; D008024:Ligands; D063065:Organophosphonates; D018094:Receptors, Metabotropic Glutamate; D013778:Tetrazolium Salts; D013844:Thiazoles; D000242:Cyclic AMP; C022616:thiazolyl blue; C012729:2-amino-4-phosphonobutyric acid; D002945:Cisplatin; D005472:Fluorouracil; C108823:metabotropic glutamate receptor 4