Heat Shock Protein 90 Inhibitors AUY922, BIIB021 and SNX5422 Induce Bim-mediated Death of Thyroid Carcinoma Cells

BACKGROUND/AIM

Heat shock protein 90 (HSP90) controls maturation of oncogenic client proteins of cancer cells, and thus we studied the effect of HSP 90 inhibitors on cell survival and survival-related mediators in thyroid carcinoma cells.

MATERIALS AND METHODS

Human TPC-1 and SW1736 thyroid carcinoma cells were utilized. Cell viability, cytotoxic activity and apoptosis were estimated using CCK-8 assay, cytotoxicity assay and FACS analysis, respectively.

RESULTS

AUY922, BIIB021 and SNX5422 decreased cell viability, and increased cytotoxic activity and the proportion of apoptotic cells. The protein levels of cleaved PARP, cleaved caspase-3, Bax and Bim were elevated, and Bcl2 protein levels were reduced. Knockdown of Bax did not change cell viability, cytotoxic activity, the proportion of apoptotic cells and cleaved caspase-3 protein levels. Meanwhile, knockdown of Bim enhanced cell viability, and diminished cytotoxic activity, the proportion of apoptotic cells and cleaved caspase-3 protein levels. AUY922, BIIB021 and SNX5422 increased the protein levels of phospho-AMPK, and decreased those of phospho-ERK1/2, and total and phospho-AKT.

CONCLUSION

AUY922, BIIB021 and SNX5422 induce cytotoxicity by modulating Bim and ERK1/2, AKT and AMPK signaling in thyroid carcinoma cells.

Synergistic cytotoxicity of BIIB021 with triptolide through suppression of PI3K/Akt/mTOR and NF-κB signal pathways in thyroid carcinoma cells

The effec.t of BIIB021, a novel heat shock protein 90 (hsp90) inhibitor, on survival of thyroid carcinoma cells has not been evaluated. In this study, the impact of BIIB021 alone or in combination with the histone acetyltransferase inhibitor triptolide on survival of thyroid carcinoma cells was identified. In 8505C and TPC-1 thyroid carcinoma cells, BIIB021 caused cell death in conjunction with alterations in expression of hsp90 client proteins. Cotreatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, decreased cell viability, and increased the percentage of dead cells and cytotoxic activity. All of the combination index values were lower than 1.0, suggesting synergistic activity of BIIB021 with triptolide in induction of cytotoxicity. In treatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, the protein levels of total and phospho-p53, and cleaved caspase-3 were elevated, while those of total Akt, phospho-mTOR, phospho-4EBP1, phospho-S6K, phospho-NF-κB, survivin, X-linked inhibitor of apoptosis protein (xIAP), cellular inhibitor of apoptosis protein (cIAP) and acetyl. histone H4 were reduced. These results suggest that BIIB021 has a cytotoxic activity accompanied by regulation of hsp90 client proteins in thyroid carcinoma cells. Moreover, the synergism between BIIB021 and triptolide in induction of cytotoxicity is associated with the inhibition of PI3K/Akt/mTOR and NF-κB signal pathways, the underexpression of survivin and the activation of DNA damage response in thyroid carcinoma cells.

BIIB021, a synthetic Hsp90 inhibitor, induces mutant ataxin-1 degradation through the activation of heat shock factor 1

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disease caused by the expansion of a polyglutamine (polyQ) tract in ataxin-1 (ATXN1). The pathological hallmarks of SCA1 are the loss of cerebellar Purkinje cells and neurons in the brainstem and the presence of nuclear aggregates containing the polyQ-expanded ATXN1 protein. Heat shock protein 90 (Hsp90) inhibitors have been shown to reduce polyQ-induced toxicity. This study was designed to examine the therapeutic effects of BIIB021, a purine-scaffold Hsp90 inhibitor, on the protein homeostasis of polyQ-expanded mutant ATXN1 in a cell culture model of SCA1. Our results demonstrated that BIIB021 activated heat shock factor 1 (HSF1) and suppressed the abnormal accumulation of ATXN1 and its toxicity. The pharmacological degradation of mutant ATXN1 via activated HSF1 was dependent on both the proteasome and autophagy systems. These findings indicate that HSF1 is a key molecule in the regulation of the protein homeostasis of the polyQ-expanded mutant ATXN1 and that Hsp90 has potential as a novel therapeutic target in patients with SCA1.

The heat shock protein 90 inhibitor BIIB021 suppresses the growth of T and natural killer cell lymphomas

Epstein-Barr virus (EBV), which infects not only B cells but also T and natural killer (NK) cells, is associated with a variety of lymphoid malignancies. Because EBV-associated T and NK cell lymphomas are refractory and resistant to conventional chemotherapy, there is a continuing need for new effective therapies. EBV-encoded “latent membrane protein 1” (LMP1) is a major oncogene that activates nuclear factor kappa B (NF-κB), c-Jun N-terminal kinase (JNK), and phosphatidylinositol 3-kinase signaling pathways, thus promoting cell growth and inhibiting apoptosis. Recently, we screened a library of small-molecule inhibitors and isolated heat shock protein 90 (Hsp90) inhibitors as candidate suppressors of LMP1 expression. In this study, we evaluated the effects of BIIB021, a synthetic Hsp90 inhibitor, against EBV-positive and -negative T and NK lymphoma cell lines. BIIB021 decreased the expression of LMP1 and its downstream signaling proteins, NF-κB, JNK, and Akt, in EBV-positive cell lines. Treatment with BIIB021 suppressed proliferation in multiple cell lines, although there was no difference between the EBV-positive and -negative lines. BIIB021 also induced apoptosis and arrested the cell cycle at G1 or G2. Further, it down-regulated the protein levels of CDK1, CDK2, and cyclin D3. Finally, we evaluated the in vivo effects of the drug; BIIB021 inhibited the growth of EBV-positive NK cell lymphomas in a murine xenograft model. These results suggest that BIIB021 has suppressive effects against T and NK lymphoma cells through the induction of apoptosis or a cell cycle arrest. Moreover, BIIB021 might help to suppress EBV-positive T or NK cell lymphomas via the down-regulation of LMP1 expression.

BIIB021, an Hsp90 inhibitor, effectively kills a myelodysplastic syndrome cell line via the activation of caspases and inhibition of PI3K/Akt and NF-κB pathway proteins

The novel orally available inhibitor of the molecular chaperone heat shock protein 90 (Hsp90), BIIB021, induces the apoptosis of various types of tumor cell in vitro and in vivo. However, the effects and mechanisms of this agent on myelodysplastic syndrome (MDS) cell lines remain unknown. The aim of this study was to investigate the effects of BIIB021 on SKM-1 cells (a MDS cell line) and examine its mechanisms of action. The results showed that BIIB021 inhibited the growth of SKM-1 cells effectively in vitro. The treatment of SKM-1 cells with BIIB021 resulted in the inhibition of cell growth through G0/G1-phase cell cycle arrest and induced apoptosis by activating caspase-3, -8 and -9. Furthermore, this study also demonstrated that the mechanisms of apoptosis in SKM-1 cells were associated with the suppression of the phosphatidylinositide 3-kinase/Akt and nuclear factor-κB signaling pathways. Therefore, the findings indicate a novel approach for the treatment of high-risk MDS.