scholarly journals The MYND Motif Is Required for Repression of Basal Transcription from the Multidrug Resistance 1 Promoter by the t(8;21) Fusion Protein

1998 ◽  
Vol 18 (6) ◽  
pp. 3604-3611 ◽  
Author(s):  
Bart Lutterbach ◽  
Daxi Sun ◽  
John Schuetz ◽  
Scott W. Hiebert
Keyword(s):  
Transcription Factor ◽  
Multidrug Resistance ◽  
Acute Leukemia ◽  
Transcriptional Repression ◽  
Chromosomal Translocations ◽  
Heptad Repeat ◽  
Chemotherapeutic Drugs ◽  
Basal Transcription ◽  
Mdr 1 ◽  
Transcription Factor Complex

ABSTRACTChromosomal translocations in acute leukemia that affect the AML-1/CBFβ transcription factor complex create dominant inhibitory proteins. However, the mechanisms by which these proteins act remain obscure. Here we demonstrate that the multidrug resistance 1 (MDR-1) promoter is a target for AML/ETO transcriptional repression. This repression is of basal, not activated, expression from the MDR-1 promoter and thus represents a new mechanism for AML/ETO function. We have defined two domains in AML/ETO that are required for repression of basal transcription from the MDR-1 promoter: a hydrophobic heptad repeat (HHR) motif and a conserved zinc finger (ZnF) domain termed the MYND domain. The HHR mediates formation of AML/ETO homodimers and AML/ETO-ETO heterodimers. Single serine substitutions at conserved cysteine residues within the predicted ZnFs also abrogate transcriptional repression. Finally, we observe that AML/ETO can also inhibit Ets-1 activation of the MDR-1 promoter, indicating that AML/ETO can disrupt both basal and Ets-1-dependent transcription. The fortuitous inhibition of MDR-1 expression in t(8;21)-containing leukemias may contribute to the favorable response of these patients to chemotherapeutic drugs.

scholarly journals Are altered pHi and membrane potential in hu MDR 1 transfectants sufficient to cause MDR protein-mediated multidrug resistance?

1996 ◽  
Vol 108 (4) ◽  
pp. 295-313 ◽  
Author(s):  
M M Hoffman ◽  
L Y Wei ◽  
P D Roepe
Keyword(s):  
Drug Resistance ◽  
Multidrug Resistance ◽  
Cell Lines ◽  
Electrical Potential ◽  
Chinese Hamster ◽  
Membrane Depolarization ◽  
Chemotherapeutic Drugs ◽  
Protein Overexpression ◽  
Membrane Electrical Potential ◽  
Mdr 1

Multidrug resistance (MDR) mediated by overexpression of the MDR protein (P-glycoprotein) has been associated with intracellular alkalinization, membrane depolarization, and other cellular alterations. However, virtually all MDR cell lines studied in detail have been created via protocols that involve growth on chemotherapeutic drugs, which can alter cells in many ways. Thus it is not clear which phenotypic alterations are explicitly due to MDR protein overexpression alone. To more precisely define the MDR phenotype mediated by hu MDR 1 protein, we co-transfected hu MDR 1 cDNA and a neomycin resistance marker into LR73 Chinese hamster ovary fibroblasts and selected stable G418 (geneticin) resistant transfectants. Several clones expressing different levels of hu MDR 1 protein were isolated. Unlike previous work with hu MDR 1 transfectants, the clones were not further selected with, or maintained on, chemotherapeutic drugs. These clones were analyzed for chemotherapeutic drug resistance, intracellular pH (pHi), membrane electrical potential (Vm), and stability of MDR 1 protein overexpression. LR73/hu MDR 1 clones exhibit elevated pHi and are depolarized, consistent with previous work with LR73/mu MDR 1 transfectants (Luz, J.G. L.Y. Wei, S. Basu, and P.D. Roepe. 1994. Biochemistry. 33:7239-7249). The extent of these perturbations is related to the level of hu MDR 1 protein that is expressed. Cytotoxicity experiments with untransfected LR73 cells with elevated pHi due to manipulating percent CO2 show that the pHi perturbations in the MDR 1 clones can account for much of the measured drug resistance. Membrane depolarization in the absence of MDR protein expression is also found to confer mild drug resistance, and we find that the pHi and Vm changes can conceivably account for the altered drug accumulation measured for representative clones. These data indicate that the MDR phenotype unequivocally mediated by MDR 1 protein overexpression alone can be fully explained by the perturbations in Vm and pHi that accompany this overexpression. In addition, MDR mediated by MDR protein overexpression alone differs significantly from that observed for MDR cell lines expressing similar levels of MDR protein but also exposed to chemotherapeutic drugs.

A new apoptosis inhibitor, CIAPIN1 (cytokine-induced apoptosis inhibitor 1), mediates multidrug resistance in leukemia cells by regulating MDR-1, Bcl-2, and Bax

2007 ◽  
Vol 85 (6) ◽  
pp. 741-750 ◽  
Author(s):  
Xiaohua Li ◽  
Liu Hong ◽  
Yunping Zhao ◽  
Haifeng Jin ◽  
Rui Fan ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Cell Line ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Leukemia Cells ◽  
Luciferase Reporter ◽  
Chemotherapeutic Drugs ◽  
Induced Apoptosis ◽  
Apoptosis Inhibitor ◽  
Mdr 1

We investigated the role of cytokine-induced apoptosis inhibitor 1 (CIAPIN1), a newly identified apoptosis inhibitor, in leukemia cell multidrug resistance (MDR) and its possible underlying mechanisms. CIAPIN1 was found to be overexpressed at the mRNA and protein levels in the vincristine-induced multidrug-resistant leukemia cell line HL-60/VCR, compared with HL-60, its parental cell line. In this study, we transfected HL-60 with a eukaryotic expression vector of CIAPIN1. In vitro drug sensitivity assays suggested that HL-60-CIAPIN1 cells conferred resistance to both P-glycoprotein (P-gp)-related and -unrelated drugs. Blocking CIAPIN1 expression in HL-60/VCR cells by CIAPIN1-specific small interfering RNA increased the cells' sensitivity to various chemotherapeutic drugs. Flow cytometry results suggested that CIAPIN1 expression could suppress adriamycin-induced apoptosis, accompanied by a decreased accumulation and increased release of adriamycin. Semiquantitative RT–PCR, Western blot analysis, and luciferase reporter assays suggested that CIAPIN1 could significantly upregulate the expression of MDR-1 and Bcl-2, the transcription of the MDR-1 gene, as well as downregulate the expression of Bax. Additionally, the inhibition of CIAPIN1 expression by RNA interference or P-gp inhibitor could partially reverse CIAPIN1-mediated MDR. Taken together, our findings suggest that downregulating CIAPIN1 could sensitize leukemia cells to chemotherapeutic drugs by downregulating MDR-1 and Bcl-2 and by upregulating Bax, yet not altering either glutathione-S-transferase activity or intracellular glutathione content in leukemia cells. Further study of CIAPIN1's function may reveal more of the mechanisms of leukemia MDR and result in the development of strategies to treat leukemia.

Multidrug resistance in chronic lymphocytic leukemia

2008 ◽  
Vol 149 (4) ◽  
pp. 161-167 ◽  
Author(s):  
Tamás Szendrei ◽  
Tamás Magyarlaki ◽  
Gábor Kovács ◽  
Ágnes Nagy ◽  
Árpád Szomor ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Chronic Lymphocytic Leukemia ◽  
Real Time ◽  
Real Time Pcr ◽  
Lymphocytic Leukemia ◽  
Light Cycler ◽  
Mdr 1

Az utóbbi években krónikus lymphoid leukaemiában új prognosztikai faktorok vizsgálata került a figyelem középpontjába. A citogenetikai eltérések, az immunglobulin-nehézlánc génmutációs státusza, a CD38- és ZAP70-expresszió mind a közelmúltban megismert prognosztikus faktorok, de kevés az adat a multidrog-rezisztencia jelentőségéről. Célok: A tanulmány célja genetikai, expressziós és funkcionális szinten jellemezni 82 krónikus lymphoid leukaemiában szenvedő beteg multidrog-rezisztenciájának sajátosságait, és vizsgálni azok összefüggését a betegek túlélésével és a kezelésre adott válasszal. Módszerek: a szerzők 66 betegnél vizsgálták az MDR-1 gén ben – Light Cycler Real Time PCR segítségével meghatározott – „Single Nucleotid Polymorphism” sajátosságot, amely irodalmi adatok szerint a P-glikoprotein expresszióját befolyásolja. Összesen 82 betegnél áramlási citometria során anti-P-glikoprotein monoklonális antitest segítségével a P-glikoprotein- expresszió t, az ún. calcein-verapamil teszttel pedig a multidrog-rezisztencia funkcióját vizsgálták. A kezelésre adott választ 35 betegnél vizsgálták, a statisztikai elemzésnél Fischer-tesztet alkalmazva. A túlélési analízist a teljes beteganyagon elvégezték ( n = 82, Log-rank-teszt). Eredmények: Az irodalmi adatokkal ellentétben a szerzők nem találtak korrelációt a vizsgált három multidrogrezisztencia-teszt között. A kezelésre adott választ vizsgálva 35 kezelt betegből 13 nonrespondernek, 22 pedig respondernek bizonyult. A P-glikoprotein-pozitív fenotípusú esetek ( n = 9) 89%-ban klinikailag nonrespondernek bizonyultak (9 P-glikoprotein-pozitív krónikus lymphoid leukaemiás beteg közül 8 nonresponder volt), a P-glikoprotein-negatív esetek ( n = 26) pedig 80%-ban jó terápiás választ mutattak (26 P-glikoprotein-negatív beteg közül 21 responder) ( p < 0,001). Az átlagos várható túlélésben is jelentős, bár nem szignifikáns ( p = 0,106) különbséget észleltek (84 vs 203 hónap). Következtetések: A vizsgált három laboratóriumi paraméter közül a P-glikoprotein sejtfelszíni jelenléte a leginkább releváns adat krónikus lymphoid leukaemiában a kemorezisztencia előjelzésére és a túléléssel kapcsolatban is prognosztikai faktorként értékelhető.

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