Increase of beta(III)- and beta(IVa)-tubulin isotopes in human prostate carcinoma cells as a result of estramustine resistance.
Estramustine (EM), an antimicrotubule agent, is effective against hormone-refractory prostate cancer when used in combination with vinblastine or paclitaxel. To understand the effect of EM on beta-tubulin, a cellular target for this class of drugs, human prostate carcinoma cells (DU-145) were made resistant to EM, and two cell lines were selected at 12- (EM-12) and 15-microMolar (EM-15) concentrations of the drug. These cell lines exhibited 8- to 9-fold resistance to EM and 2- to 4-fold cross-resistance to paclitaxel. Immunofluorescent staining of the cells with beta-tubulin isotype-specific antibodies showed an approximately 6-fold increase in the beta(III)-tubulin levels and moderate increase in overall beta-tubulin levels in EM-resistant cells when compared to DU-145 cells. This increase of beta(III) isotype was confirmed by Western analysis. A reverse transcriptase-PCR assay was also employed using beta-tubulin isotype-specific primers to quantify beta-tubulin isotype RNA. A 4-fold increase in beta(III) and a 3-fold increase in beta(IV alpha) transcript were seen in both EM-resistant cell lines. These results indicate that overexpression of specific beta-tubulin isotypes may play a role in the cellular defense against EM and other antimicrotubule agents.
Ranganathan
S
S
Department of Medicine, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Dexter
D W
DW
Benetatos
C A
CA
Chapman
A E
AE
Tew
K D
KD
Hudes
G R
GR
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D004351:Drug Resistance; D004961:Estramustine / Q000494:pharmacology*; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011471:Prostatic Neoplasms / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D014404:Tubulin / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D017931:DNA Primers; D012333:RNA, Messenger; D014404:Tubulin; D004961:Estramustine