Hsp90 inhibitor BIIB021 enhances triptolide-induced apoptosis of human T-cell acute lymphoblastic leukemia cells in vitro mainly by disrupting p53-MDM2 balance

Abstract

Aim: To investigate the effects of BIIB021, an inhibitor of heat shock protein 90 (Hsp90) alone or in combination with triptolide (TPL) on T-cell acute lymphoblastic leukemia (T-ALL) and the mechanisms of action. Methods: Human T-ALL cells line Molt-4 was examined. The cell viability was measured using MTT assay. Apoptotic cells were studied with Hoechst 33258 staining. Cell apoptosis and cell cycle were analyzed using flow cytometry with Annexin V/PI staining and PI staining, respectively. The levels of multiple proteins, including Akt, p65, CDK4/6, p18, Bcl-2 family proteins, MDM2, and p53, were examined with Western blotting. The level of MDM2 mRNA was determined using RT-PCR. Results: Treatment of Molt-4 cells with BIIB021 (50-800 nmol/L) inhibited the cell growth in a dose-dependent manner (the IC 50 value was 384.6 and 301.8 nmol/L, respectively, at 48 and 72 h). BIIB021 dose-dependently induced G 0 /G 1 phase arrest, followed by apoptosis of Molt-4 cells. Furthermore, BIIB021 increased the expression of p18, decreased the expression of CDK4/6, and activated the caspase pathway in Molt-4 cells. Moreover, BIIB021 (50-400 nmol/L) dose-dependently decreased the phospho-MDM2 and total MDM2 protein levels, but slightly increased the phospho-p53 and total p53 protein levels, whereas TPL (5-40 nmol/L) dosedependently enhanced p53 activation without affecting MDM2 levels. Co-treatment with BIIB021 and TPL showed synergic inhibition on Molt-4 cell growth. The co-treatment disrupted p53-MDM2 balance, thus markedly enhanced p53 activation. In addition, the co-treatment increased the expression of Bak and Bim, followed by increased activation of caspase-9. Conclusion: The combination of BIIB021 and TPL may provide a novel strategy for treating T-ALL by overcoming multiple mechanisms of apoptosis resistance.

Combined PI3K/Akt and Hsp90 targeting synergistically suppresses essential functions of alloreactive T cells and increases Tregs

“…In addition, aberrantly up-regulated Hsp90, promoting tumor cell survival and growth, has been described in human hematologic malignancies. such as MM [35], chronic lymphocytic leukemia [22], acute lymphoid leukemia [36], acute myeloid leukemia [37], and diffuse large B cell lymphoma [38]-altogether, malignancies that are subject to ASCT. This implicates that pharmacological Hsp90 inhibition could serve as a bridging concept to suppress residual tumor growth temporally upon ASCT until the GvL reaction has been fully developed.…”

BIIB021: A novel inhibitor to heat shock protein 90–addicted oncology

“…Similar to other HSP90 inhibitors, BIIB021 is also reported to block the constitutive NF-κB activity in cancers 32 and induce apoptosis by disrupting the p53-MDM2 balance in leukemia. 31 Moreover, He et al 43 proved for the first time that BIIB021 could also induce autophagic response as evidenced by the formation of autophagosome in chronic myeloid leukemia (CML), which is related to the Akt-mTOR-Ulk1 signaling pathway. Besides, this chemical compound was also reported to sensitize esophageal squamous cell carcinoma and head and neck squamous cell carcinoma to radiation.…”

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

“…In malignant cells, BIIB021 and triptolide, as a single drug, modulate PI3K/Akt and NF-kB signal pathways, and thereby have cytotoxic activities [15][16][17][18][19][20][21][22]. Meanwhile, BIIB021 causes cell death by regulating mTOR-Ulk1 signal pathway in chronic myeloid leukemia cells [23].…”

“…With regard to thyroid cancer, it was shown that triptolide induced cytotoxicity via downregulation of NF-kB in ATC cells [16][17][18]. Although the combined effect of BIIB021 with triptolide was explored in acute lymphoblastic leukemia cells [19], the impact of BIIB021 in combination with triptolide on survival of thyroid carcinoma cells has not been identified.…”