Forced Expression of Heat Shock Protein 27 (Hsp27) Reverses P-Glycoprotein (ABCB1)-mediated Drug Efflux and MDR1 Gene Expression in Adriamycin-resistant Human Breast Cancer Cells

Abstract

Mutant p53 accumulation has been shown to induce the multidrug resistance gene (MDR1) and ATP binding cassette (ABC)-based drug efflux in human breast cancer cells. In the present work, we have found that transcriptional activation of the oxidative stress-responsive heat shock factor 1 (HSF-1) and expression of heat shock proteins, including Hsp27, which is normally known to augment proteasomal p53 degradation, are inhibited in Adriamycin (doxorubicin)-resistant MCF-7 cells (MCF-7/adr). Such an endogenous inhibition of HSF-1 and Hsp27 in turn results in p53 mutation with gain of function in its transcriptional activity and accumulation in MCF-7/adr. Also, lack of HSF-1 enhances nuclear factor B (NF-B) DNA binding activity together with mutant p53 and induces MDR1 gene and P-glycoprotein (P-gp, ABCB1), resulting in a multidrug-resistant phenotype. Ectopic expression of Hsp27, however, significantly depleted both mutant p53 and NF-B (p65), reversed the drug resistance by inhibiting MDR1/P-gp expression in MCF-7/ adr cells, and induced cell death by increased G 2 /M population and apoptosis. We conclude from these results that HSF-1 inhibition and depletion of Hsp27 is a trigger, at least in part, for the accumulation of transcriptionally active mutant p53, which can either directly or NF-B-dependently induce an MDR1/P-gp phenotype in MCF-7 cells. Upon Hsp27 overexpression, this pathway is abrogated, and the acquired multidrug resistance is significantly abolished so that MCF-7/adr cells are sensitized to Dox. Thus, clinical alteration in Hsp27 or NF-B level will be a potential approach to circumvent drug resistance in breast cancer.Development of a multidrug-resistant phenotype is a major obstacle to the successful treatment of breast cancer (1, 2). There are two major pathways by which cancer cells acquire drug resistance, drug efflux and direct suppression of apoptosis. Drug efflux is due to increased plasma membrane accumulation of various ATP-binding cassette (ABC) 2 transporters, including ABCB1, also known as P-glycoprotein (P-gp), which extrude the internalized drugs from the cancer cells (3-5). Various approaches have been reported to overcome the drug efflux, including pharmacological inhibition of ABCs and modulation of endogenous regulators of MDR1 (6). Drug resistance is also acquired via direct suppression of apoptotic pathways due to accumulation of mutant p53 (mutp53) with "gain of function" (7, 8) and increased expression of antiapoptotic proteins, such as BCl-2 (4). In addition to abrogating the proapoptotic function of wild type p53 (wtp53), these p53 missense mutations have been shown to have unusual gain of function properties both in vitro and in vivo (9 -11). Recent studies have established a link between these two pathways of drug resistance (12).Mutant p53 has been found to be the prominent common mediator of both pathways (11). Wild type p53 is generally known to repress the expression of the MDR1 gene, which codes for the ABC protein P-gp through interaction with basal transcription facto...

Heat shock proteins and heat shock factor 1 in carcinogenesis and tumor development: an update

“…Another link between MDR and HSPs has been reported in doxorubicin-resistant MCF-7 cells (Kanagasabai et al 2011). In these cells the transcriptional activation HSF1 and expression of HSPs (including Hsp27 which is normally known to augment proteasomal p53 degradation) are inhibited, resulting in the accumulation of transcriptionally active mutant p53.…”

Grape Seed Procyanidin Reversal of P-glycoprotein Associated Multi-Drug Resistance via Down-regulation of NF-κB and MAPK/ERK Mediated YB-1 Activity in A2780/T Cells

“…Molecularly, the P-gp/MDR1 expression is mediated by nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) [10], [11], [12], cylooxygenases-2 [13], CYP3A4 [14], the mitogen-activated protein kinase (MAPK) pathway [15], [16], [17], and phosphoinositide 3-kinase (PI3K) [10], [18]. Among these, NF-κB and MAPK/ERK pathway are the most important factors in terms of their molecular mechanisms for inducing MDR.…”

Imatinib Reverses Doxorubicin Resistance by Affecting Activation of STAT3-Dependent NF-κB and HSP27/p38/AKT Pathways and by Inhibiting ABCB1

“…Numerous transporters have been implicated in chemoresistance; however, ABCB1 (MDR-1, P-gp), ABCC1 (MRP1), and ABCG2 (BCRP) have been most extensively studied [7]. Activation of a variety of pathways including FOXO3a, PI3K/Akt, NF-κB, and extracellular signal-regulated kinase (ERK), as well as HSP27 depletion have been implicated in ABC transporter upregulation [8]–[10].…”