The levels of HDAC1 and thioredoxin1 are related to the death of mesothelioma cells by suberoylanilide hydroxamic acid

Mechanism of Drug Resistance to First-Line Chemotherapeutics Mediated by TXNDC17 in Neuroblastomas

BACKGROUND

The prognosis of high-risk neuroblastomas (NB) that are resistant to first-line induction chemotherapy is relatively poor. This study explored the mechanism of resistance to first-line chemotherapeutics mediated by TXNDC17 and its potential solutions in NB.

METHODS

The genetic and clinical data of patients with NB were obtained from the Therapeutically Applicable Research to Generate Effective Treatments dataset. TXNDC17 and BECN1 expressions in NB cells were up- and downregulated by transfection with plasmids and shRNA, respectively. Autophagy-related proteins were detected by western blot. Cell viability was determined using cell proliferation and toxicity experiments. Apoptotic cells were detected using flow cytometry.

RESULTS

Overall, 1076 pediatric and adolescent patients with NB were enrolled in this study. The 10-year overall survival (OS) rates and event-free survival (EFS) rates for the patients with a mutation of BECN1 were 37.4 ± 9.1% and 34.5 ± 8.8%, respectively. For patients with a mutation of TXNDC17, the 10-year OS and EFS were 41.4 ± 5.9% and 24.3 ± 5.1%, respectively, which were significantly lower than those in the unaltered group. The overexpression of BECN1 and TXNDC17 reduced NB sensitivity to cisplatin (DDP), etoposide (VP16), and cyclophosphamide (CTX). Autophagy mediated by BECN1 was regulated by TXNDC17, and this process was involved in the resistance to DDP, VP16, and CTX in NB. Suberoylanilide hydroxamic acid (SAHA) can enhance the sensitivity and apoptosis of NB cells to chemotherapeutics by inhibiting TXNDC17, ultimately decreasing autophagy-mediated chemoresistance.

CONCLUSIONS

Acquired resistance to first-line chemotherapeutics was associated with autophagy mediated by BECN1 and regulated by TXNDC17, which can be reversed by SAHA.

Unraveling Novel Strategies in Mesothelioma Treatments Using a Newly Synthetized Platinum(IV) Compound

Malignant mesothelioma is a rare tumor associated with asbestos exposure. Mesothelioma carcinogenesis is related to enhanced reactive oxygen species (ROS) production and iron overload. Despite the recent advances in biomedical sciences, to date the only available treatments include surgery in a small fraction of patients and platinum-based chemotherapy in combination with pemetrexed. In this view, the purpose of this study was to evaluate the therapeutic potential of the newly synthetized platinum prodrug Pt(IV)Ac-POA compared to cisplatin (CDDP) on human biphasic mesothelioma cell line MSTO-211H using different complementary techniques, such as flow-cytometry, transmission electron microscopy (TEM), and immunocytochemistry. Healthy mesothelial cell lines Met-5A were also employed to assess the cytotoxicity of the above-mentioned compounds. Our in vitro results showed that Pt(IV)Ac-POA significantly interfere with iron metabolisms and more importantly is able to trigger cell death, through different pathways, including ferroptosis, necroptosis, and apoptosis, in neoplastic cells. On the other hand, CDDP triggers mainly apoptotic and necrotic cell death. In conclusion, Pt(IV)Ac-POA may represent a new promising pharmacological agent in the treatment of malignant mesothelioma.

Propyl gallate induces cell death in human pulmonary fibroblast through increasing reactive oxygen species levels and depleting glutathione

Propyl gallate (PG) exhibits an anti-growth effect on various cell types. The present study investigated the impact of PG on the levels of reactive oxygen species (ROS) and glutathione (GSH) in primary human pulmonary fibroblast (HPF) cells. Moreover, the effects of N-acetyl cysteine (NAC, an antioxidant), L-buthionine sulfoximine (BSO, a GSH synthesis inhibitor), and small interfering RNA (siRNAs) against various antioxidant genes on ROS and GSH levels and cell death were examined in PG-treated HPF cells. PG (100-800 μM) increased the levels of total ROS and O2·- at early time points of 30-180 min and 24 h, whereas PG (800-1600 μM) increased GSH-depleted cell number at 24 h and reduced GSH levels at 30-180 min. PG downregulated the activity of superoxide dismutase (SOD) and upregulated the activity of catalase in HPF cells. Treatment with 800 μM PG increased the number of apoptotic cells and cells that lost mitochondrial membrane potential (MMP; ΔΨm). NAC treatment attenuated HPF cell death and MMP (ΔΨm) loss induced by PG, accompanied by a decrease in GSH depletion, whereas BSO exacerbated the cell death and MMP (ΔΨm) loss without altering ROS and GSH depletion levels. Furthermore, siRNA against SOD1, SOD2, or catalase attenuated cell death in PG-treated HPF cells, whereas siRNA against GSH peroxidase enhanced cell death. In conclusion, PG induced cell death in HPF cells by increasing ROS levels and depleting GSH. NAC was found to decrease HPF cell death induced by PG, while BSO enhanced cell death. The findings shed light on how manipulating the antioxidant system influence the cytotoxic effects of PG in HPF cells.

Ebselen Inhibits the Growth of Lung Cancer Cells via Cell Cycle Arrest and Cell Death Accompanied by Glutathione Depletion

Ebselen is a glutathione (GSH) peroxidase (GPx) mimic originally developed to reduce reactive oxygen species (ROS). However, little is known about its cytotoxicological effects on lung cells. Therefore, this study aimed to investigate the effects of Ebselen on the cell growth and cell death of A549 lung cancer cells, Calu-6 lung cancer cells, and primary normal human pulmonary fibroblast (HPF) cells in relation to redox status. The results showed that Ebselen inhibited the growth of A549, Calu-6, and HPF cells with IC50 values of approximately 12.5 μM, 10 μM, and 20 μM, respectively, at 24 h. After exposure to 15 μM Ebselen, the proportions of annexin V-positive cells were approximately 25%, 65%, and 10% in A549, Calu-6, and HPF cells, respectively. In addition, Ebselen induced arrest at the S phase of the cell cycle in A549 cells and induced G2/M phase arrest in Calu-6 cells. Treatment with Ebselen induced mitochondrial membrane potential (MMP; ΔΨm) loss in A549 and Calu-6 cells. Z-VAD, a pan-caspase inhibitor, did not decrease the number of annexin V-positive cells in Ebselen-treated A549 and Calu-6 cells. Intracellular ROS levels were not significantly changed in the Ebselen-treated cancer cells at 24 h, but GSH depletion was efficiently induced in these cells. Z-VAD did not affect ROS levels or GSH depletion in Ebselen-treated A549 or Ebselen-treated Calu-6 cells. In conclusion, Ebselen inhibited the growth of lung cancer and normal fibroblast cells and induced cell cycle arrest and cell death in lung cancer cells with GSH depletion.

Recent Progress in Histone Deacetylase Inhibitors as Anticancer Agents

Histone Deacetylase (HDAC) inhibitors are a relatively new class of anti-cancer agents that play important roles in epigenetic or non-epigenetic regulation, inducing death, apoptosis, and cell cycle arrest in cancer cells. Recently, their use has been clinically validated in cancer patients resulting in the approval by the FDA of four HDAC inhibitors, vorinostat, romidepsin, belinostat and panobinostat, used for the treatment of cutaneous/peripheral T-cell lymphoma and multiple myeloma. Many more HDAC inhibitors are at different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. Also, clinical trials of several HDAC inhibitors for use as anti-cancer drugs (alone or in combination with other anti-cancer therapeutics) are ongoing. In the intensifying efforts to discover new, hopefully, more therapeutically efficacious HDAC inhibitors, molecular modelingbased rational drug design has played an important role. In this review, we summarize four major structural classes of HDAC inhibitors (hydroxamic acid derivatives, aminobenzamide, cyclic peptide and short-chain fatty acids) that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

A Succinate Ether Derivative of Tocotrienol Enhances Dickkopf-1 Gene Expression through Epigenetic Alterations in Malignant Mesothelioma Cells

BACKGROUND

Wnt signaling plays an essential role in tumor cell growth, including the development of malignant mesothelioma (MM). Epigenetic silencing of negative Wnt regulators leading to constitutive Wnt signaling has been observed in various cancers and warrants further attention. We have reported that a succinate ether derivative of α-tocotrienol (T3E) has potent cytotoxic effects in MM cells. Thus, in this study, we investigated whether the anti-MM effect of T3E could be mediated via the epigenetic alteration of the Wnt antagonist gene, Dickkopf-1 (DKK1).

METHODS

WST-1 and cell analyzers were employed to analyze the effects of T3E on cell viability and apoptosis of human MM cell lines (H2452, H28). Real-time PCR and Western blot were performed to evaluate the expression at mRNA and protein levels. Methylation status and epigenetic modifications of DKK1's promoter regions after T3E treatment in MM cells were studied using methylation-specific PCR and Chromatin immunoprecipitation. Small interfering RNA-mediated knockdown -(siRNA), and specific inhibitors, were used to validate DKK1 as a target of T3E.

RESULTS

T3E markedly impaired MM cell viability, increased the expression of phosphorylated-JNK and DKK1 and suppressed cyclin D, a downstream target gene of Wnt signaling. Knockdown of DKK1 expression by siRNA or a specific JNK inhibitor confirmed the contribution of DKK1 and JNK to T3E-induced cytotoxicity in MM cells. On the other hand, cytoskeleton-associated protein 4 (CKAP4) expression, which promotes cell proliferation as a Wnt-independent DKK1 receptor was inhibited by T3E. Silencing CKAP4 by -siRNA did not appear to directly affect MM cell viability, thereby indicating that expression of both DKK1 and CKAP4 is required. Furthermore, T3E-mediated inhibition of both DNA methyltransferases (DNMT1, 3A, and 3B) and histone deacetylases (HDAC1, 2, 3, and 8) in MM cells leads to increased DKK1 expression, thereby promoting tumor growth inhibition. MM cells treated with Zebularine (a DNMT inhibitor) and sodium butyrate (an HDAC inhibitor) exhibited cytotoxic effects, which may explain the inhibitory action of T3E on MM cells. In addition, an enhanced expression of DKK1 in MM cells following T3E treatment is positively correlated with the methylation status of its promoter; T3E decreased DNA methylation and increased histone acetylation. Moreover, T3E specifically increased histone H3 lysine 4 (H3K4) methylation activity, whereas no effects were observed on histone H3K9 and H3K27.

CONCLUSIONS

Targeting the epigenetic induction of DKK1 may lead to effective treatment of MM, and T3E has great potential to induce anti-MM activity.