Clonogenicity of human leukemic cells protected from cell-lethal agents by heat shock protein 70

Abstract

Pretreatment of human leukemia THP-1 cells with heat shock protein Hsp70 (Hsp70) protected them from the cell-lethal effects of the topoisomerase II inhibitor, lucanthone and from ionizing radiation. Cell viability was scored in clonogenic assays of single cells grown in liquid medium containing 0.5% methyl cellulose. Colonies were observed and rapidly scored after staining with the tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide. The frequency of abasic sites in the deoxyribonucleic acid (DNA) of THP-1 cells was reduced when these cells were treated with Hsp70. Hsp70 is presumed to have protected the cells by promoting repair of cell DNA, in agreement with previous studies that showed that Hsp70 enhanced base excision repair by purified enzymes. The shoulders of radiation dose-response curves were enhanced by pretreatment of cells with Hsp70 and, importantly, were reduced when cells were transfected with ribonucleic acid designed to silence Hsp70. Hsp70 influenced repair of sublethal damage after radiation.

Heat shock protein 70 (Hsp70)-stimulated deoxycytidine deaminases from a human lymphoma cell but not the activation-induced cytidine deaminase (AID) from Ramos 6.4 human Burkitt's lymphoma cells

“…All these enzyme activities are stimulated by Hsp70. As expected, UDG and HAP1 activities were depressed in THP1 leukemic cells 24 h after transfection with an siRNA designed to inhibit Hsp70 (Bases 2005(Bases , 2006. Rohde et al showed that Hsp70 and its mRNA were depressed in such siRNA-transfected cells but only after a 36 h lag (Rohde et al 2006 and personal communication).…”

“…Transfection A 5 nm of RNA (siRNA or scrambled RNA) was transfected in 6×10 7 cells as recommended by the manufacturer (Bases 2005(Bases , 2006.…”

“…Accumulating evidence indicates that enzymes of DNA base excision repair are stimulated by Hsp70 (Bases 2005(Bases , 2006Kenny et al 2001;Mendez et al 2003a, b). Cell DNA, which is a substrate for cytidine deaminase, contains uridine after deamination of cytidine (Bransteitter et al 2003).…”

Over-expressed heat shock protein 70 protects cells against DNA damage caused by ultraviolet C in a dose-dependent manner

“…Ciavarra et al (1994) reported that nuclear type I topoisomerase complexes with Hsc70 might limit heat-induced protein damage, accelerate restoration of protein function in an ATPindependent reaction, or both. Some studies showed that Hsp70 can improve base excision repair by interacting with human apurinic/apyrimidinic endonuclease and by stimulating single-strand gap-filling by DNA polymerase beta (Mendez et al 2000(Mendez et al , 2003Kenny et al 2001;Bases 2005). In a previous study, we found a significantly negative correlation between Hsp70 levels and the level of DNA damage as measured by the comet assay in workers exposed to coke oven emissions (Xiao et al 2002).…”

Treating cancer stem cells and cancer metastasis using glucose-coated gold nanoparticles

“…The image is formed due to the interaction of electrons when they pass through the nanoparticles. The clonogenicity of THP-1 cells has been reported, 44 and cell surface markers like CD44 expressed in THP-1 have also been studied. 45 THP-1 is one of the common cell types used for modeling cancer stem cells.…”