Drug resistance mechanisms in chronic lymphocytic leukemia.
Peripheral blood samples from 18 patients with chronic lymphocytic leukemias (CLL) who were either untreated but who were later sensitive to chlorambucil (CLL S) or resistant to a combination containing doxorubicin, vincristine, cyclophosphamide and prednisone (CLL R) were studied for glutathione system, P-glycoprotein, PCNA and topoisomerase II expression. P-glycoprotein expression detected by an immunocytochemical technique using MRK 16 antibody was present at the same level in CLL S and CLL R. The percentage of cells positive for P-gp was below 5% in all samples tested. Topoisomerase IIalpha level was quantified by Western blot analysis. None of the 18 CLL samples had detectable topoisomerase IIalpha protein. In addition, 12 CLL were tested for PCNA staining and no samples had more than 1% of positive cells at immunocytochemical detection indicating that CLL cells were not engaged in the cell cycle. Some differences were found between CLL S and CLL R in the glutathione system. Glutathione concentration (GSH) and GST activity was the same in CLL S and CLL R. The glutathione-S-transferase (GST) isoenzyme profile was different in the two CLL groups. The mean GST-pi and GST-alpha quantitation were twice as high as in CLL R compared to CLL S, but this difference did not reach statistical significance because of large variations between CLL samples. A significant correlation was observed between GST-pi expression and GST activity using CDNB as the substrate. GST-mu was detected in only one of seven CLL before therapy and in six of 11 resistant to chemotherapy. No correlation was found between P-glycoprotein expression, GST activity and the different GST isoenzymes studied. These results suggest that the glutathione system could play a role in the resistance of anticancer agents in chronic lymphocytic leukemia. The role of the other drug resistance mechanisms (P-glycoprotein and topoisomerase IIalpha) seems to be of limited importance.
Ribrag
V
V
Service de Médecine C, Institut Gustave-Roussy, Villejuif, France.
Massade
L
L
Faussat
A M
AM
Dreyfus
F
F
Bayle
C
C
Gouyette
A
A
Marie
J P
JP
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000097:blood; D000951:Antigens, Neoplasm; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002699:Chlorambucil / Q000627:therapeutic use; D003520:Cyclophosphamide / Q000008:administration & dosage; D004250:DNA Topoisomerases, Type II / Q000097:blood; D004268:DNA-Binding Proteins; D004317:Doxorubicin / Q000008:administration & dosage; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D005978:Glutathione / Q000097:blood; D005982:Glutathione Transferase / Q000097:blood; D018922:HL-60 Cells / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000097:blood; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000188:drug therapy* / Q000201:enzymology; D011241:Prednisone / Q000008:administration & dosage; D018809:Proliferating Cell Nuclear Antigen / Q000097:blood; D014750:Vincristine / Q000008:administration & dosage
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000951:Antigens, Neoplasm; D018906:Antineoplastic Agents, Alkylating; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D018809:Proliferating Cell Nuclear Antigen; D002699:Chlorambucil; D014750:Vincristine; D004317:Doxorubicin; D003520:Cyclophosphamide; D005982:Glutathione Transferase; D004250:DNA Topoisomerases, Type II; D005978:Glutathione; D011241:Prednisone