Geldanamycin induces mitotic catastrophe and subsequent apoptosis in human glioma cells

Abstract

Geldanamycin (GA) binds to heat shock protein 90 (Hsp90) and interferes with its function which is to protect various cellular proteins involved in signaling, growth control, and survival from ubiquitination and subsequent degradation by the proteasome. Recently, we demonstrated that GA inhibited migration of glioma cells in vitro associated with downregulation of hypoxia-inducible factor (HIF-1 alpha) and phosphorylation of focal adhesion kinase (FAK) (Zagzag et al., 2003, J Cell Physiol 196:394-402). Here, we have investigated the mechanisms through which GA treatment of the T98G glioma cell line induces apoptosis. We found that GA treatment induced cell death in a caspase-dependent manner through activation of caspase-3 and PARP cleavage together with release of cytochrome c and apoptosis inducing factor (AIF) from the mitochondria. Use of synchronized T98G cells showed that GA treatment of glioma cells during S-phase enhanced cytotoxicity followed by M-phase arrest, resulting in mitotic catastrophe. In addition, apoptosis was associated with the downregulation of the survival protein, phosphorylated Akt (pAkt), an important signaling protein in the PI3K pathway, that is overexpressed in many cancers including gliomas. Given that many glioma tumors show deregulation of the PI3K signaling pathway, either through loss of the tumor suppressor protein PTEN or overexpression of the growth factor EGFR, the ability to identify different subsets of patients using simple immunohistochemistry for the presence of absence of pAkt could enable selection of the appropriate kinase inhibitor, such as GA, for drug therapy. Based on our data presented here, GA or its analogs may have potential in the treatment of glioma.

Inhibition of Hsp90 function by ansamycins causes downregulation of cdc2 and cdc25c and G2/M arrest in glioblastoma cell lines

“…This G 2 /M arrest was sustained in synchronized U87 cells (Figure 1e). It has been shown that GA can induce mitotic catastrophe and apoptosis in T98 cells (Nomura et al, 2004). We have confirmed these data but we were able to observe accumulation of mitotic cells only in A172 and T98 cells (data not shown).…”

Arsenite-induced mitotic death involves stress response and is independent of tubulin polymerization

“…However, HSP90 inhibitors causing disruption or protein defects at the centrosome may be an additional mechanism causing HSP90 inhibitor-induced mitotic arrest and cell death. Similar to arsenite, the HSP90 inhibitor geldanamycin causes cell death through mitotic catastrophe in human glioma cells (Nomura et al, 2004). We also found that the HSP90 inhibitor 17-DMAG produced a mitotic arrest and induction of abnormal centrosome number ( Figure 7A and B).…”

Analysis of hypoxia‐inducible factor‐1α accumulation and cell cycle in geldanamycin‐treated human cervical carcinoma cells by laser scanning cytometry

“…Beyond a drug concentration of 100 nM, cell death seems solely dependent on the number of cells entering mitosis at a certain time. Recent findings by Nomura et al (32) suggest a phase-specific effect on glioma cells with S-phase cells being most sensitive, which points toward similar mechanisms as observed in our experiments. However, LSC provides no exact measure for cell death, since floating and dead cells might be washed away during the slide preparation.…”

“…human cervical carcinoma cells could be sensitized to radiation (37) and human breast cancer cells could be sensitized to Taxol (38). Cell cycle arrest either in G 1 -or G 2 =M-phase has been observed upon inhibition of Hsp90 and was suspected to depend on the presence or absence of the Rb gene product (32,36,39). The exact mechanism by which geldanamycin compromises the cell cycle is still a matter of controversy, and de Carcer recently reported results that suggest a major role of Hsp90 in controlling the metaphase-anaphase transition of HeLa cells through Polo-like kinase1 (31).…”

“…Recent studies on HeLa cells (31) and glioma cells (32) showed that certain cell lines depend on Hsp90 for ordered progress through mitosis and that the inhibition of the heat shock protein in these cells leads to G 2 -and/or M-phase arrest with subsequent cell death by mitotic catastrophe. The observed increase of cell numbers in the premitotic fraction after treatment with geldanamycin raised the possibility that SiHa and ME180 cells could respond to the treatment in a similar way.…”