Involvement of calcium in the differential induction of heat shock protein 70 by heat shock protein 90 inhibitors, geldanamycin and radicicol, in human non-small cell lung cancer H460 cells

Abstract

Both geldanamycin (GA) and radicicol (RA) are HSP90 binding agents that possess antitumour activities. Although the in vitro data indicated that the inhibitory constant of RA is much bigger than that of GA, the in vivo data on drug efficacy might reveal different results. We have recently shown that treatment with GA induces a heat-shock response and that calcium mobilization may be involved in the process. By using induction of HSP70 as the endpoint assay, we found changes in upstream signaling mediators, including HSF1 and calcium mobilization, as well as possible involvement of protein kinase in human non-small cell lung cancer H460 cells treated with GA and RA. Our results demonstrated that calcium mobilization, a calcium dependent and H7-sensitive protein kinase, along with HSF1 activation by phosphorylation, are all involved in the HSP70 induction process triggered by the drugs. However, only GA, but not RA, can provoke a rapid calcium mobilization and thereby result in an instant induction of HSP70. Furthermore, the rapid calcium influx, followed by instant HSP induction, could be achieved in GA- or RA-treated cells placed in a medium containing excessive calcium while the response was completely abolished in cells depleted of calcium. Taken together, our findings suggest that differential calcium signaling may account for the differential induction of HSP and the action of GA and RA.

TNF-α Mediates Eosinophil Cationic Protein-induced Apoptosis in BEAS-2B Cells

“…Metabolic labeling of nascent proteins was conducted as described [69]. At the end of various treatment periods, the cells were washed with PBS twice, and replaced with RPMI medium containing [ 35 S]methionine (20 μCi/ml) for 2 h. After removal of the medium, the cells were washed with PBS twice and lysed with 2× sample buffer.…”

Anti-malaria drug blocks proteotoxic stress response: Anti-cancer implications

“…In mammalian cells, HSR is largely mediated by activation of the transcription factor HSF1. HSF1 normally resides in the cytoplasm in an inactive form bound to hsp90 2–6. Under conditions of proteotoxic stress, HSF1 becomes activated and translocates to the nucleus where it stimulates expression of a set of heat shock response genes including those encoding inducible chaperones such as hsp70 and hsp27 7–9.…”

Concerted actions of multiple transcription elements confer differential transactivation of HSP90 isoforms in geldanamycin‐treated 9L rat gliosarcoma cells

“…Upon activation, HSF1 undergoes a multi-step process that involves conversion from a monomer to a trimeric nuclear protein complex, followed by binding to the HSEs of the heat-shock genes, thus triggering their transactivation [Pirkkala et al, 2001]. Most recently, we have also demonstrated that treatment of human nonsmall-cell lung cancer H460 cells with GA leads to phosphorylation-activation of HSF1, which in turn stimulates HSP70-1/2 [Shu et al, 2005;Chang et al, 2006a]. In the present study, the results of supershift assays also indicate that HSF1 is the transcription factor that is activated in the GA-induced transactivation of the hsp90 genes in rat 9L cells.…”