Abstract
The efficacy of verapamil and cyclosporine A as modulators of P-glycoprotein, the multidrug resistance (MDR1) gene product, was studied in leukemic blast cells from 56 patients with de novo acute myeloid leukemia (AML) in vitro. Rhodamine123 dye-efflux was measured flow cytometrically as a cellular parameter reflecting P-glycoprotein activity. While dye-efflux was measurable in 3 4 of the cases, the capacity of the P-glycoprotein inhibitors varied substantially among patients. In 23 patients, P-glycoprotein function was completely inhibited by the resistance modulators, whereas in 17 patients neither verapamil nor cyclosporine had any reverting effect on dye-efflux at concentrations even 10-times higher than achievable in vivo. Cells with a drug-sensitive rhodamine123-pump effluxed more efficiently (p=0.0016) and contained significantly higher levels of MDR1 specific RNA transcripts (p=0.0002), as determined by quantitative PCR, than cells exhibiting an efflux process that could not be inhibited. However, flow cytometric evaluation of the staining of gated blast cells with the anti-P-glycoprotein antibody, 4E3.16, revealed no difference in P-glycoprotein expression between modulator-sensitive and -insensitive cases (p=0.86), indicating disproportionate translation of MDRI mRNA. In leukemic cell populations with increased P-glycoprotein function that could be inhibited, significantly more blasts expressed the progenitor cell antigen, CD34 (median 83%), than was the case in leukemias with P-glycoprotein activity that could not be inhibited (median 7%) (p=0.0001). The present study demonstrates that a substantial fraction of AML patients constitutively display a drug-efflux mechanism suggestive of P-glycoprotein activity. However, in many of those patients rhodamine123-efflux from blast cells in vitro was not sensitive to classical P-glycoprotein inhibitors.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 47-52 |
| Number of pages | 6 |
| Journal | Blood Reviews |
| Volume | 9 |
| Issue number | 1 |
| DOIs | |
| State | Published - 1995 |
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ASJC Scopus subject areas
- Hematology
- Oncology
- Cancer Research
Cite this
Modulation of multidrug resistance in de novo adult acute myeloid leukemia : Variable efficacy of reverting agents in vitro. / Paietta, Elisabeth M.; Racevskis, Janis; Ashigbi, J.; Wiernik, P. H.; Andersen, J.; Cassileth, P.
In: Blood Reviews, Vol. 9, No. 1, 1995, p. 47-52.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Modulation of multidrug resistance in de novo adult acute myeloid leukemia
T2 - Variable efficacy of reverting agents in vitro
AU - Paietta, Elisabeth M.
AU - Racevskis, Janis
AU - Ashigbi, J.
AU - Wiernik, P. H.
AU - Andersen, J.
AU - Cassileth, P.
PY - 1995
Y1 - 1995
N2 - The efficacy of verapamil and cyclosporine A as modulators of P-glycoprotein, the multidrug resistance (MDR1) gene product, was studied in leukemic blast cells from 56 patients with de novo acute myeloid leukemia (AML) in vitro. Rhodamine123 dye-efflux was measured flow cytometrically as a cellular parameter reflecting P-glycoprotein activity. While dye-efflux was measurable in 3 4 of the cases, the capacity of the P-glycoprotein inhibitors varied substantially among patients. In 23 patients, P-glycoprotein function was completely inhibited by the resistance modulators, whereas in 17 patients neither verapamil nor cyclosporine had any reverting effect on dye-efflux at concentrations even 10-times higher than achievable in vivo. Cells with a drug-sensitive rhodamine123-pump effluxed more efficiently (p=0.0016) and contained significantly higher levels of MDR1 specific RNA transcripts (p=0.0002), as determined by quantitative PCR, than cells exhibiting an efflux process that could not be inhibited. However, flow cytometric evaluation of the staining of gated blast cells with the anti-P-glycoprotein antibody, 4E3.16, revealed no difference in P-glycoprotein expression between modulator-sensitive and -insensitive cases (p=0.86), indicating disproportionate translation of MDRI mRNA. In leukemic cell populations with increased P-glycoprotein function that could be inhibited, significantly more blasts expressed the progenitor cell antigen, CD34 (median 83%), than was the case in leukemias with P-glycoprotein activity that could not be inhibited (median 7%) (p=0.0001). The present study demonstrates that a substantial fraction of AML patients constitutively display a drug-efflux mechanism suggestive of P-glycoprotein activity. However, in many of those patients rhodamine123-efflux from blast cells in vitro was not sensitive to classical P-glycoprotein inhibitors.
AB - The efficacy of verapamil and cyclosporine A as modulators of P-glycoprotein, the multidrug resistance (MDR1) gene product, was studied in leukemic blast cells from 56 patients with de novo acute myeloid leukemia (AML) in vitro. Rhodamine123 dye-efflux was measured flow cytometrically as a cellular parameter reflecting P-glycoprotein activity. While dye-efflux was measurable in 3 4 of the cases, the capacity of the P-glycoprotein inhibitors varied substantially among patients. In 23 patients, P-glycoprotein function was completely inhibited by the resistance modulators, whereas in 17 patients neither verapamil nor cyclosporine had any reverting effect on dye-efflux at concentrations even 10-times higher than achievable in vivo. Cells with a drug-sensitive rhodamine123-pump effluxed more efficiently (p=0.0016) and contained significantly higher levels of MDR1 specific RNA transcripts (p=0.0002), as determined by quantitative PCR, than cells exhibiting an efflux process that could not be inhibited. However, flow cytometric evaluation of the staining of gated blast cells with the anti-P-glycoprotein antibody, 4E3.16, revealed no difference in P-glycoprotein expression between modulator-sensitive and -insensitive cases (p=0.86), indicating disproportionate translation of MDRI mRNA. In leukemic cell populations with increased P-glycoprotein function that could be inhibited, significantly more blasts expressed the progenitor cell antigen, CD34 (median 83%), than was the case in leukemias with P-glycoprotein activity that could not be inhibited (median 7%) (p=0.0001). The present study demonstrates that a substantial fraction of AML patients constitutively display a drug-efflux mechanism suggestive of P-glycoprotein activity. However, in many of those patients rhodamine123-efflux from blast cells in vitro was not sensitive to classical P-glycoprotein inhibitors.
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U2 - 10.1016/0268-960X(95)90039-X
DO - 10.1016/0268-960X(95)90039-X
M3 - Article
VL - 9
SP - 47
EP - 52
JO - Blood Reviews
JF - Blood Reviews
SN - 0268-960X
IS - 1
ER -