The Expression Of HSP70 And HSP90 MRNA And Their Significance In Patients With Acute Leukemia

Objective: Heat shock proteins (HSPs) are ubiquitous andhighly conserved proteins in the cell. Under normal conditions,HSPs are expressed constitutively at a low level, while theirexpression can be induced to increase remarkably in response toa wide variety of physiological and environmental insults. Theseproteins play an essential role in cell growth, development anddifferentiation, gene transcription, protein synthesis, folding,transport and degradation, and so on. HSP70 and HSP90 areprimary induciable proteins and abundantly expressed in cancercells, where they may participate in oncogenesis, progression,prognosis, and limit the efficacy of cancer therapy. In this study,we intend to investigate the expression of HSP70 and HSP90 inleukemia cells and their correlation with FAB subtypes, WBCcount and prognosis so as to improve the strategy for thetreatment of leukemia.Methods: Semi-quantitative reverse transcriptionpolymerase chain reaction (RT-PCR) was applied to detectthe mRNA expression of HSP70, HSP90 and mdr-1 inmarrow mononuclear cells from 84 patients with acuteleukemia including 50 de novo cases, 28 cases in completeremission and 6 cases in relapse , and 15 healthy volunteers(normal controls, NC). In addition, the leukemia cell linesK562 and HL-60 were also tested as positive control. Thepossible correlation between HSP70/HSP90 mRNA and FABsubtypes, the leukemia cells count in peripheral blood, andprognosis was evaluated. It was found that there was anover-expression of HSP70 and HSP90 mRNA in K562 andHL-60 cell lines, used as positive controls.Results1 In untreated acute leukemia samples including AML and ALL,the level of HSP70 mRNA (the positive rate 100%, the meanlevel 0.711±0.432) was significantly higher than that in normalcontrols (the positive rate 100% and the mean level 0.210±0.142)(p<0.05). The HSP70 mRNA expression level in AML (themean level 0.696±0.322) and ALL (mean 0.785±0.485) wereboth significantly higher than in NC(P<0.05), but there was nosignificant difference between AML and ALL(P > 0.05). AS forHSP90, its mRNA expression in newly diagnosed AL group (thepositive rate 100%, the mean level 0.519±0.334) was alsosignificantly higher than that in normal control (positive rate:100%,mean level: 0.185±0.065)(P<0.05). There were nosignificant difference in its expression between AML (meanlevel: 0.501±0.214) and ALL group (mean level: 0.615±0.326),P> 0.05, though they were both higher than in NC, P<0.05.2 The expression level of HSP70 mRNA (positive rate 100%,mean level 0.324±0.210) and HSP90 mRNA( positive rate100%, mean level 0.232±0.106) in complete remission groupwere both higher than those in NCs, respectively, although theywere not statistically significant(P>0.05). The level in remissiongroup was lower than in untreated AL group(P<0.05).3 The level of HSP70 mRNA in relapsed group was1.098±0.315, and significantly higher than both in untreatedgroup and NC(P<0.05, P<0.01, respectively). The HSP90mRNA level in relapsed group(the mean level 0.853±0.280) wasalso significantly higher than NC's(P < 0.01). There wasdifference between relapse group and untreated group in boththe levels of HSP90 mRNA and HSP70 mRNA(P<0.05).4 The high HSP70 and HSP90 mRNA expression weredetected in two leukemia cell lines tested, with HSP70 mRNAlevel 0.769 and HSP90 mRNA 0.621 in K562 cell line, andHSP70's level 0.657 and HSP90's 0.516 in HL60 cell line,respectively.5 In untreated AL group, the expression level of HSP70 andHSP90 mRNA were unequal among different subtypes and thelower level was detected in M3 and higher level in M5, but therewas no statistical difference (P > 0.05).6 According to blast cell count in peripheral blood, theuntreated AL patients were divided into hyper-blast (≥10×10~9/L) and hypoblast group(<10×10~9/L). The HSP70 mRNAlevel in hyperblast group(0.757±0.507) was higher than that inhypoblast group(0.463±0.381)(P<0.05) and so was the HSP90mRNA levels (mean 0.683±0.466 and 0.409±0.342, respectively)(P<0.05).7 In order to analyse the relationship of HSP and multi-drugresistance, the mdr-1 mRNA level was assayed and the untreatedAL patients were divided into mdr-1+ and mdr-1-group. Themean level of mdr-1mRNA was 0.545±0.260 in untreated group,0.819±0.420 in relapse group, and 0.211±0.09 in remissiongroup. HSP70 mRNA expression level in mdr-1+ group (themean level 0.860±0.210) was higher than in mdr-1-group(themean level 0.506±0.230)(P<0.05) and so was HSP90 (meanlevel 0.659±0.280 and 0.410±0.160, respectively)(P<0.05).8 The untreated AL patients were divided intocomplete-remission group and refractory group according to thechemotherapy response for standard protocol. HSP70mRNAlevel of remission group (mean level: 0.475±0.360) was lowerthan in refractory one (mean level: 0.748±0.457) (P<0.05).HSP90 mRNA level in complete-remission group (mean level:0.406±0.282) was also lower than in refractory group(meanlevel: 0.675±0.401) (P<0.05).9 In untreated group and relapse group, there was a positivecorrelation between HSP70mRNA and mdr-1mRNA ( r=0.60,P<0.05). A positive correlation was also observed betweenHSP90 mRNA and mdr-1mRNA( r=0.58,P<0.05), betweenHSP70 mRNA and HSP90 mRNA (r=0.673 , p< 0.0001).Conclusions1 HSP70 and HSP90 were extensively expressed both in normalindividuals and AL patients. The expression level was higher in...