Heat shock protein 70 antisense oligonucleotide inhibits cell growth and induces apoptosis in human gastric cancer cell line SGC-7901

AIM: Heat shock protein (HSP)70 is over-expressed in human gastric cancer and plays an important role in the progression of this cancer. We investigated the effects of antisense HSP70 oligomer on human gastric cancer cell line SGC-7901, and its potential role in gene therapy for this cancer.METHODS: Human gastric cancer cell line SGC-7901 was treated in vitro with various concentrations of antisense HSP70 oligonucleotides at different intervals. Growth inhibition was determined as percentage by trypan blue dye exclusion test. Extracted DNA was electrophoresed on agarose gel, and distribution of cell cycle and kinetics of apoptosis induction were analyzed by propidium iodide DNA incorporation using flow cytometry, which was also used to detect the effects of antisense oligomer pretreatment on the subsequent apoptosis induced by heat shock in SGC-7901 cells. Proteins were extracted for simultaneous measurement of HSP70 expression level by SDS-PAGE Western blotting.RESULTS: The number of viable cells decreased in a doseand time-dependent manner, and ladder-like patterns of DNA fragments were observed in SGC-7901 cells treated with antisense HSP70 oligomers at a concentration of 10 μmol/L for 48 h or 8 μmol/L for 72 h, which were consistent with inter-nucleosomal DNA fragmentation. Flow cytometric analysis showed a dose- and time-dependent increase in apoptotic rate by HSP70 antisense oligomers. This response was accompanied with a decrease in the percentage of cells in the G1 and S phases of the cell cycle, suggesting inhibition of cell proliferation. In addition, flow cytometry also showed that pretreatment of SGC-7901 cells with HSP70 antisense oligomers enhanced the subsequent apoptosis induced by heat shock treatment. Western blotting demonstrated that HSP70 antisense oligomers inhibited HSP70 expression, which preceded apoptosis, and HSP70 was undetectable at the concentration of 10 μmol/L for 48 h or 8 μmol/L for 72 h.CONCLUSION: Antisense HSP70 oligomers can abrogate HSP70 expression in SGC-7901 cells, which may in turn induce apoptosis and inhibit cell proliferation, conversely suggesting that HSP70 is required for the proliferation and survival of human gastric cancer cells under normal conditions.

Abrogation of heat-shock protein (HSP)70 expression induced cell growth inhibition and apoptosis in human androgen-independent prostate cancer cell line PC-3m

Aim: To investigate the effect of abrogating heat shock protein (HSP) 70 expression by antisense HSP70 oligonucleotides treatment on human androgen-independent prostate cancer cell line PC-3m growth. Methods: PC-3m cells were treated with 0-16 μmol/L antisense HSP70 oligomers for 0-100 hr. Cell growth inhibition was analyzed using a trypan blue dye exclusion test. Apoptotic cells were detected and confirmed by flow cytometric analysis and DNA fragmentation analysis. The protein expression of HSP70 and bcl-2 affected by antisense HSP70 oligomers were determined using Western blot. Results: Antisense HSP70 oligomer induced apoptosis and then inhibited proliferation of PC-3m cells in a dose- and time-dependent manner. Ladder-like patterns of DNA fragments were observed in PC-3m cells treated with 10 μmol/L antisense HSP70 oligomer for 48 hr or 8 μmol/L for 72 hr on agarose gel electrophoresis. Antisense HSP70 oligomer pretreatment enhanced the subsequent induction of apoptosis by heat shock in PC-3m cells. In addition, undetectable HSP70 expression was observed at a concentration of 10 μmol/L antisense HSP70 oligomer treatment for 48 hr or 8 μmol/L for 72 hr in Western blot, which was paralleled by decreased expression levels of anti-apoptotic protein bcl-2. Conclusion: HSP70 antisense oligomer treatment abrogates the expression of HSP70, which may disrupt HSP70-bcl-2-interactions and further down-regulate bcl-2 expression, in turn inducing apoptosis and inhibiting cell growth in PC-3m cells.