SAHA induces apoptosis in hepatoma cells and synergistically interacts with the proteasome inhibitor Bortezomib

Abstract

Histone deacetylase (HDAC) inhibitors represent a promising group of anticancer agents. This paper shows that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) stimulated at 5-10 microM apoptosis in human hepatoma HepG2 and Huh6 cells, but was ineffective in primary human hepatocytes (PHH). In HepG2 cells SAHA induced the extrinsic apoptotic pathway, increasing the expression of both FasL and FasL receptor and causing the activation of caspase-8. Moreover, SAHA enhanced the level of Bim proteins, stimulated alternative splicing of the Bcl-X transcript with the expression of the proapoptotic Bcl-Xs isoform, induced degradation of Bid into the apoptotic factor t-Bid and dephosphorylation and inactivation of the anti-apoptotic factor Akt. Consequently, SAHA caused loss of mitochondrial transmembrane potential, release of cytochrome c from mitochondria, activation of caspase-3 and degradation of PARP. Interestingly, a combination of suboptimal doses of SAHA (1 microM) and bortezomib (5-10 nM), a potent inhibitor of 26S proteasome, synergistically induced apoptosis in both HepG2 and Huh6 cells, but was ineffective in PHH. Combined treatment increased with synergistic effects the expression levels of c-Jun, phospho-c-Jun and FasL and the production of Bcl-Xs. These effects were accompanied by activation of Bid, caspase-8 and 3. In conclusion, SAHA stimulated apoptosis in hepatoma cells and exerted a synergistic apoptotic effect when combined with bortezomib. In contrast, these treatments were quite ineffective in inducing apoptosis in PHH. Thus, our results suggest the potential application of the SAHA/bortezomib combination in clinical trials for liver cancer.

Histone deacetylase inhibitors induce FPGS mRNA expression and intracellular accumulation of long-chain methotrexate polyglutamates in childhood acute lymphoblastic leukemia: implications for combination therapy

“…10,14 The ability of cells to accumulate higher intracellular concentrations of MTX-PGs correlates with their in vitro and in vivo sensitivity to MTX. 14 This is consistent with the higher IC 50 for MTX in CCRF-CEM (T-ALL) as compared with in NALM6 and other Bp-ALL cells in our study and other reports. 14 The data presented here, demonstrate that upregulation of FPGS mRNA expression by SAHA results in a net pharmacological increase of 30% in intracellular of long-chain MTX-PGs accumulation in ALL cell lines as compared with that in untreated control.…”

“…[39][40][41] Consequently, SAHA is currently being evaluated in several phase-II studies of patients with hematologic and solid-tumor malignancies. 42 SAHA also has shown synergism in hematological malignancies when combined with a wide variety of agents such as the Src kinase-family inhibitor dasatinib; 43 the heat-shock protein 90 antagonist 17-allylamino-17-demethoxygeldanamycin; 44 the cyclin-dependent kinase inhibitor flavopiridol; 45 the nuclear factor-kB inhibitor Bay 11-7082; 46 the Bcr/Abl TK inhibitors imatinib and MK-0457; 47,48 the MEK1/2 inhibitor PD184352; 49 the proteasome inhibitor bortezomib 50,51 and DNA topoisomerase-II inhibitors, 52 among others.…”

“…In addition, concomitant decrease in the expression of the enzymes DHFR and TS inhibited by MTX-PGs, should enhance the synergism of the combination HDACI plus MTX in ALL cells. To test this hypothesis, CCRF-CEM (T-ALL), NALM6 (Bp-ALL), REH (Bp-ALL expressing TEL/AML1) and SupB15 (Bp-ALL expressing Bcr/Abl) cells were treated sequentially with MTX (4 h) and SAHA (24 h) at EC 50 concentrations, and apoptotic cell death was assessed by Annexin-V binding to phosphatidylserine exposed on the surface of apoptotic cells after 48 h. These cell lines were chosen as representative of ALL phenotypes with distinct MTX sensitivities and metabolic profiles, including the TEL/AML1-positive REH cell line known to accumulate low levels of MTX-PGs 35,36 and the highly chemotherapy-resistant, Bcr/Abl-positive SUPB15 cells. 35 …”

SAHA/TRAIL combination induces detachment and anoikis of MDA-MB231 and MCF-7 breast cancer cells

“…Distribution of cells throughout the cell cycle phases was ascertained by flow cytometric analysis using a Beckman Coulter Epics XL cytometer as previously reported [19]. In addition, apoptotic cells were detected by flow cytometry using the annexin V-FITC Apoptosis Detection Kit I (BD Biosciences Pharmingen; San Diego, CA), according to the manufacturer's instructions.…”

“…HDAC inhibitors are a new class of anticancer drugs, which have shown significant antiproliferative activity against a spectrum of hematological and solid tumors [18,19]. Our previous studies demonstrated the ability of suberoylanilide hydroxamic acid (SAHA), an inhibitor of HDAC, to sensitize human hepatocarcinoma cells to TRAIL-induced apoptosis by enhancing the expression of DR5 and decreasing the level of the anti-apoptotic factor c-FLIP [20].…”