Upregulated expression of BCL-2 in multiple myeloma cells induced by exposure to doxorubicin, etoposide, and hydrogen peroxide.
Enhanced expression of the antiapoptotic gene BCL-2 may participate in chemoresistance. To ascertain if multiple myeloma cells surviving exposure to chemotherapy alter their BCL-2 expression, we treated the myeloma cell lines 8226, IM-9, and U266 as well as a primary myeloma cell culture with various injurious agents. Doxorubicin, etoposide, and hydrogen peroxide consistently induced a concentration- and time-dependent upregulation of BCL-2 expression in all myeloma target cell types assayed by flow cytometry and Western blot analysis. In contrast, serum starvation, dexamethasone, and anti-fas antibodies had no effect on expression. Enhanced expression of BCL-2 was relatively selective as treatments had no effect on expression of Ig light chains, BCL-X, or actin. An reverse transcriptase-polymerase chain reaction assay showed increased levels of BCL-2 RNA in 8226 cells as early as 4 hours after treatment with doxorubicin at a time when cell recoveries were not decreased. Thus, doxorubicin stimulates BCL-2 expression in individual 8226 cells rather than simply allowing a selected survival of high BCL-2-expressing cells in culture. Doxorubicin-treated 8226 cells with upregulated BCL-2 expression were relatively resistant to a second exposure of doxorubicin. In addition, BCL-2-transfected IM-9 cells, with enhanced expression of BCL-2 which was comparable to that achieved by initial exposure to doxorubicin, were resistant to doxorubicin and etoposide cytotoxicity. These data suggest that exposure to chemotherapeutic agents may enhance BCL-2 expression in surviving myeloma cells and contribute to acquired chemoresistance.
Tu
Y
Y
VA Wadsworth-UCLA Medical Center, CA 16042, USA.
Xu
F H
FH
Liu
J
J
Vescio
R
R
Berenson
J
J
Fady
C
C
Lichtenstein
A
A
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001483:Base Sequence; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005047:Etoposide / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D014407:Tumor Cells, Cultured / Q000187:drug effects; D019014:fas Receptor / Q000502:physiology
D000970:Antineoplastic Agents; D016895:Culture Media, Serum-Free; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor; D005047:Etoposide; D003907:Dexamethasone; D004317:Doxorubicin; D006861:Hydrogen Peroxide