Prohibitin promotes apoptosis of promyelocytic leukemia induced by arsenic sulfide

Prohibitin 1 inhibits cell proliferation and induces apoptosis via the p53-mediated mitochondrial pathway in vitro

BACKGROUND

Prohibitin 1 (PHB1) has been identified as an antiproliferative protein that is highly conserved and ubiquitously expressed, and it participates in a variety of essential cellular functions, including apoptosis, cell cycle regulation, proliferation, and survival. Emerging evidence indicates that PHB1 may play an important role in the progression of hepatocellular carcinoma (HCC). However, the role of PHB1 in HCC is controversial.

AIM

To investigate the effects of PHB1 on the proliferation and apoptosis of human HCC cells and the relevant mechanisms in vitro.

METHODS

HCC patients and healthy individuals were enrolled in this study according to the inclusion and exclusion criteria; then, PHB1 levels in the sera and liver tissues of these participates were determined using ELISA, RT-PCR, and immunohistochemistry. Human HepG2 and SMMC-7721 cells were transfected with the pEGFP-PHB1 plasmid and PHB1-specific shRNA (shRNA-PHB1) for 24-72 h. Cell proliferation was analysed with an MTT assay. Cell cycle progression and apoptosis were analysed using flow cytometry (FACS). The mRNA and protein expression levels of the cell cycle-related molecules p21, Cyclin A2, Cyclin E1, and CDK2 and the cell apoptosis-related molecules cytochrome C (Cyt C), p53, Bcl-2, Bax, caspase 3, and caspase 9 were measured by real-time PCR and Western blot, respectively.

RESULTS

Decreased levels of PHB1 were found in the sera and liver tissues of HCC patients compared to those of healthy individuals, and decreased PHB1 was positively correlated with low differentiation, TNM stage III-IV, and alpha-fetoprotein ≥ 400 μg/L. Overexpression of PHB1 significantly inhibited human HCC cell proliferation in a time-dependent manner. FACS revealed that the overexpression of PHB1 arrested HCC cells in the G0/G1 phase of the cell cycle and induced apoptosis. The proportion of cells in the G0/G1 phase was significantly increased and the proportion of cells in the S phase was decreased in HepG2 cells that were transfected with pEGFP-PHB1 compared with untreated control and empty vector-transfected cells. The percentage of apoptotic HepG2 cells that were transfected with pEGFP-PHB1 was 15.41% ± 1.06%, which was significantly greater than that of apoptotic control cells (3.65% ± 0.85%, P < 0.01) and empty vector-transfected cells (4.21% ± 0.52%, P < 0.01). Similar results were obtained with SMMC-7721 cells. Furthermore, the mRNA and protein expression levels of p53, p21, Bax, caspase 3, and caspase 9 were increased while the mRNA and protein expression levels of Cyclin A2, Cyclin E1, CDK2, and Bcl-2 were decreased when PHB1 was overexpressed in human HCC cells. However, when PHB1 was upregulated in human HCC cells, Cyt C expression levels were increased in the cytosol and decreased in the mitochondria, which indicated that Cyt C had been released into the cytosol. Conversely, these effects were reversed when PHB1 was knocked down.

CONCLUSION

PHB1 inhibits human HCC cell viability by arresting the cell cycle and inducing cell apoptosis via activation of the p53-mediated mitochondrial pathway.

Role of Prohibitins in Aging and Therapeutic Potential Against Age-Related Diseases

A decline in mitochondrial function has long been associated with age-related health decline. Several lines of evidence suggest that interventions that stimulate mitochondrial autophagy (mitophagy) can slow aging and prolong healthy lifespan. Prohibitins (PHB1 and PHB2) assemble at the mitochondrial inner membrane and are critical for mitochondrial homeostasis. In addition, prohibitins (PHBs) have diverse roles in cell and organismal biology. Here, we will discuss the role of PHBs in mitophagy, oxidative phosphorylation, cellular senescence, and apoptosis. We will also discuss the role of PHBs in modulating lifespan. In addition, we will review the links between PHBs and diseases of aging. Finally, we will discuss the emerging concept that PHBs may represent an attractive therapeutic target to counteract aging and age-onset disease.

Realgar Nanoparticles Inhibit Migration, Invasion and Metastasis in a Mouse Model of Breast Cancer by Suppressing Matrix Metalloproteinases and Angiogenesis

BACKGROUND

Realgar, a traditional Chinese medicine, has shown antitumor efficacy in several tumor types. We previously showed that realgar nanoparticles (nano-realgar) had significant antileukemia, anti-lung cancer and anti-liver cancer effects. In addition, the anti-tumor effects of nanorealgar were significantly better than those of ordinary realgar.

OBJECTIVE

To explore the inhibitory effects and molecular mechanisms of nano-realgar on the migration, invasion and metastasis of mouse breast cancer cells.

METHODS

Wound-healing migration assays and Transwell invasion assays were carried out to determine the effects of nano-realgar on breast cancer cell (4T1) migration and invasion. The expression levels of matrix metalloproteinase (MMP)-2 and -9 were measured by Western blot. A murine breast cancer metastasis model was established, administered nano-realgar for 32 days and monitored for tumor growth and metastasis by an in vivo optical imaging system. Finally, living imaging and hematoxylin and eosin (HE) staining were used to measure the morphology and pathology of lung and liver cancer cell metastases, respectively. Angiogenesis was assessed by CD34 immunohistochemistry.

RESULTS

Nano-realgar significantly inhibited the migration and invasion of breast cancer 4T1 cells and the expression of MMP-2 and -9. Meanwhile, nano-realgar effectively suppressed the abilities of tumor growth, metastasis and angiogenesis in the murine breast cancer metastasis model in a time- and dosedependent manner.

CONCLUSION

Nano-realgar significantly inhibited migration and invasion of mouse breast cancer cells in vitro as well as pulmonary and hepatic metastasis in vivo, which may be closely correlated with the downexpression of MMP-2 and -9 and suppression of tumor neovascularization.

As4S4 Exhibits Good Killing Effect on Multiple Myeloma Cells Via Repressing SOCS1 Methylation-Mediated JAK2/STAT3 Signaling Pathway

Objective:

This study aimed to investigate the effect of tetra-arsenic tetra-sulfide on treating multiple myeloma and its potential regulation on suppressor of cytokine signaling 1 methylation-mediated Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway.

Methods:

Tetra-arsenic tetra-sulfide with different concentrations were used to treat U266 cells, and cell viability was measured at 12, 24, and 48 hours with 0 μM tetra-arsenic tetra-sulfide treatment as control by Cell Counting Kit-8 assay. Suppressor of cytokine signaling 1 methylation and expression were determined by methylation-specific polymerase chain reaction, quantitative polymerase chain reaction, and Western blot, respectively, in U266 cells and normal plasma cells and in U266 cells treated by tetra-arsenic tetra-sulfide. Then, rescue experiments were performed by transfecting suppressor of cytokine signaling 1 small interfering RNA into tetra-arsenic tetra-sulfide-treated U266 cells. Besides, phosphor–Janus kinase 2, Janus kinase 2, phospho–signal transducer and activator of transcription 3, and signal transducer and activator of transcription 3 expressions were determined by Western blot.

Results:

Tetra-arsenic tetra-sulfide inhibited U266 cell viability efficiently in a dose- and time-dependent manner. Suppressor of cytokine signaling 1 methylation was higher while suppressor of cytokine signaling 1 expression was lower in U266 cells compared to normal plasma cells; when treated by tetra-arsenic tetra-sulfide, suppressor of cytokine signaling 1 methylation was decreased while suppressor of cytokine signaling 1 expression was increased in U266 cells, along with the reduced phospho–Janus kinase 2 and phospho–signal transducer and activator of transcription 3 expressions. Then, suppressor of cytokine signaling 1 small interfering RNA enhanced the cell viability and phospho–Janus kinase 2 as well as phospho–signal transducer and activator of transcription 3 expressions in both tetra-arsenic tetra-sulfide treatment-free and tetra-arsenic tetra-sulfide-treated U266 cells.

Conclusion:

Tetra-arsenic tetra-sulfide exhibits good killing effect on multiple myeloma cells via repressing suppressor of cytokine signaling 1 methylation and downstream Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway, which might serve as a potential treatment option for multiple myeloma.

TAF-Iβ deficiency inhibits proliferation and promotes apoptosis by rescuing PP2A and inhibiting the AKT/GSK-3β pathway in leukemic cells

Template-activating factor Iβ (TAF-Iβ) has been associated with numerous pathophysiological processes and has been reported as an oncogene responsible for the regulation of important signaling pathways in various types of solid tumor; however, few studies have investigated the role of TAF-Iβ in leukemia. The present study reported the upregulated expression of TAF-Iβ in 36 patients with acute leukemia and six leukemic cell lines. In addition, TAF-Iβ-knockdown (KD) cells were generated via RNA interference. TAF-Iβ KD not only inhibited the proliferation of leukemia cells but also induced apoptosis. Furthermore, it was revealed that the mechanism underlying these effects may be associated with the upregulation of protein phosphatase type 2A and inhibition of the protein kinase B/glycogen synthase kinase-3β signaling pathway. Collectively, the findings demonstrated that TAF-Iβ serves an important role in various types of leukemia and may be considered as a potential therapeutic target for the treatment of leukemia.

Anti-liver cancer effect and the mechanism of arsenic sulfide in vitro and in vivo

PURPOSE

This study aimed at investigating the anti-tumor effect of arsenic sulfide (As₂S₂) against liver cancer both in vivo and in vitro and to elucidate its underlying mechanisms.

METHODS

Cell viability of the human hepatocellular carcinoma cell lines SMMC-7721, BEL-7402, HepG2 were measured by CCK-8 assay. The effects of As₂S₂ on cell proliferation and apoptosis of SMMC-7721 cells were investigated using Calcein-AM and PI staining, Hoechst 33258 staining, crystal violet staining, and JC-1 staining. Cell cycle and Annexin V/PI assay were analyzed via flow cytometry. The expression of apoptosis-related proteins, phosphorylation of PI3K and AKT were detected by Western blotting. H22-bearing mice model was established to evaluate the anti-tumor effect of As₂S₂ in vivo. HE staining, PCNA was observed via immunohistochemistry, and TUNEL assay was used to assess the anti-proliferation and pro-apoptotic effects of As₂S₂.

RESULTS

As₂S₂ significantly inhibited the growth of human hepatoma cells SMMC-7721, BEL-7402 and HepG2. As₂S₂ inhibited cell proliferation effectively by inducing G0/G1 cell cycle arrest in SMMC-7721 cells. As₂S₂ could increase Bax/Bcl-2 ratio, decrease mitochondrial membrane potential, promote the release of cytochrome c, increase the levels of cleaved caspase-3 and PARP, indicating that As₂S₂ induced apoptosis in SMMC-7721 cells via mitochondrial-mediated apoptosis pathway. Further research showed that As₂S₂ inhibited the PI3K/AKT signaling pathway leading to apoptotic cell death. In addition, As₂S₂ significantly inhibited tumor growth in H22-bearing mice and induced apoptosis by deactivating PI3K/AKT pathway, which was consistent with the in vitro results.

CONCLUSION

These findings suggested that As₂S₂ could induce apoptosis of liver cancer cells in vitro and in vivo, which was related to PI3K/AKT-mediated mitochondrial pathway and may provide a novel promising therapeutic agent for liver cancer treatment.

Proteomics analysis demonstrating rosmarinic acid suppresses cell growth by blocking the glycolytic pathway in human HepG2 cells

Rosmarinic acid (RA), isolated from herbal balm mint plants, has demonstrated potent anti-tumor properties against liver cancer. However, the precise underlying mechanisms remain unclear. This study aimed to investigate the molecular mechanisms of RA in HepG2 cells. RA anti-tumor activity was assessed using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, and Hoechst 33258 staining. Apoptosis and the cell cycle distribution were evaluated by flow cytometry. A proteomics approach was used to identify differentially expressed proteins following RA treatment in HepG2 cells, and quantitative reverse transcription-quantitative polymerase chain reaction was used to validate the results. Bioinformatics analysis was also implemented to further understand the identified proteins, and western blotting was used to analyze the associated proteins. Our results suggested that RA treatment significantly inhibits the viability of HepG2 cells. The MTT and LDH assays indicated dose-dependent decreases in cell proliferation following RA treatment. Hoechst 33258 staining and flow cytometry analysis showed that RA exhibits an apoptosis-inducing effect and induces cell cycle arrest in G1. The proteomics analysis successfully identified 16 differentially expressed proteins. Bioinformatics analysis indicated that the identified proteins participated in several biological processes and exhibited various molecular functions, mainly related to inactivation of the glycolytic pathway. Further western blotting analysis showed that RA could downregulate the expression of glucose transporter-1 and hexokinase-2, leading to the suppression of glucose consumption and generation of lactate and ATP. Taken together, our study found that RA exhibits significant cytotoxic effects by inhibiting cell proliferation and inducing apoptosis and cell cycle arrest, possibly by blocking the glycolytic pathway in human HepG2 cells.

Significance of elevated Prohibitin 1 levels in Multiple Sclerosis patients lymphocytes towards the assessment of subclinical disease activity and its role in the central nervous system pathology of disease

Multiple Sclerosis (MS) is an autoimmune-neurodegenerative disorder managed therapeutically by modulating lymphocytes activity which has potential in disease management. Prohibitin 1(PHB) that controls the reactive oxygen species (ROS) and present on the activated lymphocytes have significance in the therapy of MS as esters of fumaric acid that regulates ROS is in phase II/III clinical trials. Thus, we evaluated the expression levels of PHB1 in experimental autoimmune encephalomyelitis (EAE), the animal model of MS and on MS patient's lymphocytes. PHB levels in brain tissue of EAE animals were determined by immunoblotting and on blood lymphocytes from MS relapse, Remission, Optic Neuritis, Neurological controls and Healthy volunteers by FACS using anti-PHB and anti-CD45 antibodies. We observed significant elevation of PHB in EAE brains (91.0 ± 17.59%) vs controls (29.8 ± 12.9%) (p = 0.01) and on lymphocytes of MS patients in acute (73.5 ± 11.20%) or relapsing (69.3 ± 17.33%) phase compared to remission (45.9 ± 8.08%) [p = 0.034 acute vs remission; p = 0.004 relapse vs remission]. Up regulation of PHB in relapsing vs remission MS patients imply the potential use of PHB to clinically evaluate subclinical disease status towards prognosis of an oncoming relapse. Elevated PHB levels in EAE brains signify the role of PHB in regulating ROS and implies PHB's role in oxidative stress.