Induction of Hsp70 in tumor cells treated with inhibitors of the Hsp90 activity: A predictive marker and promising target for radiosensitization
Fig 5
The data of Western blotting and MTT assay demonstrating the enhanced radiosensitization of 17AAG-treated HeLa cells by preventing the Hsp70 induction with triptolide or quercetin.
The presented blots (A) demonstrate that both inhibitors of the Hsp induction completely abrogated up-regulation of inducible Hsp70 in response to the 17AAG treatment. (The values of Hsp70/Actin band ratio are presented along the lower sides of blots and reflect the relative amount of Hsp70 in cell samples. Of note, such co-treatments with the Hsp70 induction inhibitors did not decrease the basal level of constitutively expressed Hsp70 in target cells). The presented curves (B) show that in contrast to the action of 17AAG alone, the two-inhibitor combinations prevented the post-radiation recovery of proliferative activity in the drug-treated cells. Very similar results were obtained with 50–200 nM geldanamycin or 30–100 nM radicicol, or 50–200 nM NVP-AUY922 instead of 17AAG and with 100–200 μM KNK437, or 5–20 μM NZ28 instead of quercetin and triptolide (not shown). MTT assay also revealed the enhanced radiosensitization of MCF-7, KTC-1, PC-3, Myc-CaP and HT 1080 cancer cells pretreated with combination of the Hsp90 activity inhibitors and inhibitors of the Hsp70 induction (not shown). The presented data express mean ± SEM of 5 independent experiments. *—significant difference from the respective unmarked values, p<0.05; **—significant difference from the respective unmarked or marked with * values, p<0.05.