Characterization of a clonal human colon adenocarcinoma line intrinsically resistant to doxorubicin.
Intrinsic low-level resistance to anti-cancer drugs is a major problem in the treatment of gastrointestinal malignancies. To address the problem presented by intrinsically resistant tumours, we have isolated two monoclonal lines from LoVo human colon adenocarcinoma cells: LoVo/C7, which is intrinsically resistant to doxorubicin (DOX); and LoVo/C5, which shows the same resistance index for DOX as the mixed parental cell population. For comparison, we have included in the study a LoVo-resistant line selected by continuous exposure to DOX and expressing a typical multidrug resistant (MDR) phenotype. In these cell lines we have studied the expression and/or activity of a number of proteins, including P-glycoprotein 170 (P-gp), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), glutathione (GSH)-dependent enzymes and protein kinase C (PKC) isoforms, which have been implicated in anti-cancer drug resistance. Intracellular DOX distribution has been assessed by confocal microscopy. The results of the present study indicate that resistance in LoVo/C7 cells cannot be attributed to alterations in P-gp, LRP or GSH/GSH-dependent enzyme levels. Increased expression of MRP, accompanied by alterations in the subcellular distribution of DOX, has been observed in LoVo/C7 cells; changes in PKC isoform pattern have been detected in both intrinsically and pharmacologically resistant cells.
Dolfini
E
E
Department of Biology and Genetics for Health Sciences, University of Milano, Milan, Italy.
Dasdia
T
T
Arancia
G
G
Molinari
A
A
Calcabrini
A
A
Scheper
R J
RJ
Flens
M J
MJ
Gariboldi
M B
MB
Monti
E
E
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000230:Adenocarcinoma / Q000378:metabolism*; D002999:Clone Cells; D003110:Colonic Neoplasms / Q000378:metabolism*; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005978:Glutathione / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein
D018528:ATP-Binding Cassette Transporters; D004317:Doxorubicin; D005978:Glutathione; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D011493:Protein Kinase C; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein