Induction of apoptosis and inhibition of telomerase activity in human bone marrow and HL-60 p53 null cells treated with anti-cancer drugs

Nanocurcumin-Mediated Down-Regulation of Telomerase Via Stimulating TGFβ1 Signaling Pathway in Hepatocellular Carcinoma Cells

BACKGROUND

Curcumin, extracted from turmeric, represents enormous potential to serve as an anticancer agent. Telomerase is viewed as a prominent molecular target of curcumin, and Transforming growth factor-β1 (TGFβ1) has proven to be a major inhibitory signaling pathway for telomerase activity. In the current study, we aimed to explore suppressive effects of nanocurcumin on telomerase expression through TGFβ1 pathway in a hepatocellular carcinoma cell line (Huh7).

METHODS

MTT assay was used to determine the effect of nonocurcumin on viability of Huh7 cells. RT-PCR was used to analyze the gene expression patterns.

RESULTS

MTT assay revealed that nanocurcumin acts in a dose- and time-dependent manner to diminish the cell viability. RT-PCR analysis indicated that nanocurcumin results in augmentation of TGFβ1 72 hours post treatment and leads to the reduction of telomerase expression 48 and 72 hours post exposure. Also, up-regulation of Smad3 and E2F1 and down-regulation of Smad7 confirmed the effect of nanocurcumin on intermediate components of TGFβ1 pathway. Furthermore, transfection of the proximal promoter of telomerase triggered a significant reduction in luciferase activity.

CONCLUSION

The data from the present study lead us to develop a deeper understanding of the mechanisms underlying nanocurcumin-mediated regulation of telomerase expression, thereby presenting a new perspective to the landscape of using nanocurcumin as a cancer-oriented therapeutic agent.

Saponin B, a novel cytostatic compound purified from Anemone taipaiensis, induces apoptosis in a human glioblastoma cell line

Glioblastoma multiforme (GBM) is one of the most common malignant brain tumors. Saponin B, a novel compound isolated from the medicinal plant, Anemone taipaiensis, has been found to have a strong time- and dose-dependent cytostatic effect on human glioma cells and to suppress the growth of U87MG GBM cells. In this study, we investigated whether saponin B induces the apoptosis of glioblastoma cells and examined the underlying mechanism(s) of action of saponin B. Saponin B significantly suppressed U87MG cell proliferation. Flow cytometric analysis of DNA in the U87MG cells confirmed that saponin B blocked the cell cycle at the S phase. Furthermore, treatment of the U87MG cells with saponin B induced chromatin condensation and led to the formation of apoptotic bodies, as observed under a fluorescence microscope, and Annexin V/PI assay further suggested that phosphatidylserine (PS) externalization was apparent at higher drug concentrations. Treatment with saponin B activated the receptor-mediated pathway of apoptosis, as western blot analysis revealed the activation of Fas-l. Saponin B increased the Bax and caspase-3 ratio and decreased the protein expression of Bcl-2. The results from the present study demonstrate that the novel compound, saponin B, effectively induces the apoptosis of GBM cells and inhibits glioma cell growth and survival. Therefore, saponin B may be a potential candidate for the development of novel cancer therapeutics with antitumor activity against gliomas.

Effect of Cx43 gene-modified leukemic bone marrow stromal cells on the regulation of Jurkat cell line in vitro

We recently reported that Cx43 expression and gap junction intercellular communication (GJIC) between acute leukemic bone marrow stromal cells (BMSCs) were deficient, which could recovery after effective chemotherapy. However, the exact role of GJIC in the hematopoietic microenvironment in leukemic cell death and proliferation is not clear. We show here that following transfection with the Cx43 gene, GJIC function was increased between leukemic BMSCs. Furthermore, compared with leukemic cells alone, the proliferation and apoptosis of leukemic cells co-cultured with BMSCs were inhibited, the percentage of G0-phase cells was higher; and expression of p53 increased and bax decreased. However, after co-culturing leukemic cells with Cx43-modified BMSCs, the number of proliferative and spontaneously apoptotic Jurkat cells increased; the percentage of G0-phase cells decreased; the expression of p53 decreased; and bax increased. Compared with Jurkat cells co-cultured with BMSCs and Jurkat cells alone, the sensitivity of leukemic cells co-cultured with Cx43-modified BMSCs to chemotherapeutics increased. Our data suggests that GJIC between leukemia BMSCs is one of the impact factor to the proliferation, apoptosis and drug sensitivity of co-cultured leukemic cells. Up-regulating its function can inhibit the protective effects of leukemic BMSCS and enhance the efficacy of therapies in hematologic malignancies.

Differential regulation of MRN (Mre11-Rad50-Nbs1) complex subunits and telomerase activity in cancer cells

Several lines of evidence suggest that cancer progression is associated with up-regulation or reactivation of telomerase and the underlying mechanism remains an active area of research. The heterotrimeric MRN complex, consisting of Mre11, Rad50 and Nbs1, which is required for the repair of double-strand breaks, plays a key role in telomere length maintenance. In this study, we show significant differences in the levels of expression of MRN complex subunits among various cancer cells and somatic cells. Notably, siRNA-mediated depletion of any of the subunits of MRN complex led to complete ablation of other subunits of the complex. Treatment of leukemia and prostate cancer cells with etoposide lead to increased expression of MRN complex subunits, with concomitant decrease in the levels of telomerase activity, compared to breast cancer cells. These studies raise the possibility of developing anti-cancer drugs targeting MRN complex subunits to sensitize a subset of cancer cells to radio- and/or chemotherapy.

Effects of combined siRNA-TR and -TERT on telomerase activity and growth of bladder transitional cell cancer BIU-87 cells

The effects of combined RNA interference (RNAi) of human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) genes on telomerase activity in a bladder cancer cell line (BIU-87 cells) were investigated by using gene chip technology in vitro with an attempt to evaluate the role of RNAi in the gene therapy of bladder transitional cell cancer (BTCC). Three TR-specific double-stranded small interfering RNAs (siRNAs) and three TERT-specific double-stranded siRNAs were designed to target different regions of TR and TERT mRNA. The phTR-siRNA, phTERT-siRNA, and the combination of both plasmids phTR+phTERT-siRNA were transfected into BIU-87 cells. The expression of hTR and hTERT mRNA was detected by quantitative fluorescent reverse transcription-polymerase chain reaction, and a telomeric repeat amplification protocol was applied to detect telomerase activity. Growth inhibition of BIU-87 cells was measured by MTT assay. Gene chip analysis was performed to evaluate the effects of the combined RNAi of hTR+hTERT genes on telomerase activity and growth of BIU-87 cells in vitro. The results showed that the expression of hTERT and hTR mRNA was inhibited by pRNAT-hTERT-III, pRNAT-hTR-III, and pRNAT-hTR-III+hTERT-III in BIU-87 cells. The inhibition efficiency of pRNAT-hTERT-III, pRNAT-hTR-III, pRNAT-hTERT-III+pRNAT-hTR-III was 67% for TERT mRNA, 41% for TR mRNA, 57% for TR mRNA and 70% for TERT mRNA in BIU-87 cells respectively. The growth of BIU-87 cells was inhibited and telomerase activity was considerably decreased, especially in the cells treated with combined RNAi-hTR and -hTERT. Gene chip analysis revealed that 21 genes were down-regulated (ATM, BAX, BCL2, BCL2L1, BIRC5, CD44, CTNNB1, E2F1, JUN, MCAM, MTA1, MYC, NFKB1, NFKBIA, NME4, PNN, PNN, SERPINE1, THBS1, TNFRSF1A, and UCC1). The results indicated that hTR-siRNA and hTERT-siRNA, especially their combination, siRNA hTR+hTERT, specifically and effectively suppressed the expression of both hTR and hTERT mRNA and telomerase activity. Molecular biological mechanism by which combined siRNA-TR and -TERT inhibited telomerase activity and growth of BIU-87 cells in vitro may involve the down-regulation of the 21 genes.

Chemoprevention by Pyrimethamine

The goal of the current research was to investigate the chemopreventive potency of an antimalaria drug, pyrimethamine, in in vitro conditions. The fibrosarcoma (WEHI-164) cell line was used for evaluating cytotoxicity, matrix metalloproteinase 2 (MMP-2) activity, and apoptosis. Pyrimethamine and methotrexate were used at concentrations of 0-8 microg/ml in triplicate and 2-fold dilutions. MMP-2 activity was assessed using zymoanalysis method. For assessment of apoptosis, the terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method was used. Cytotoxicity analysis of pyrimethamine showed a greater tolerability than methotrexate at concentrations of 1-8 microg/ml. The dose-dependent inhibitory effect of pyrimethamine on MMP-2 activity was significantly less than that of methotrexate at concentrations of 1-8 microg/ml. Moreover, the rate of apoptosis for pyrimethamine-treated cells at different doses (0.1, 1, and 10 microg/ml) was 3.30%, 9.42%, and 11.32%, respectively. Our data suggest that pyrimethamine enables suppression of MMP-2 activity and induces apoptosis that could be assumed for chemoprevention therapy.

Mechanisms by which Astragalus membranaceus injection regulates hematopoiesis in myelosuppressed mice

The aim of this study was to investigate the mechanism underlying the effects of Astragalus membranaceus injection (AMI) on myelopoiesis in myelosuppressed mice. At 72 h after cyclophosphamide injection (250 mg/kg), the mice were administered AMI (500 mg/kg) intraperitoneally for 6 consecutive days or an equivalent volume of saline as a control. Murine colony-forming unit-fibroblast (CFU-F) formation, production of IL-6 and GM-CSF by bone marrow stromal cells (BMSC), and bcl-2 protein and mRNA expression in BMSC were measured by CFU-F assay, ELISA, immunohistochemistry and in situ hybridization. The results indicated that AMI improved the hematopoietic microenvironment by enhancing the BMSC survival and proliferation of CFU-F, production of IL-6 as well as GM-CSF by BMSC and bcl-2 protein and mRNA expression in BMSC, which promoted myelopoiesis. The data may provide a mechanistic basis for applying this ancient Chinese herb to promote hematopoiesis as an efficacious adjuvant therapy against myelosuppression induced by anti-cancer therapy.

Synergistic effect of oxymatrine and angiogenesis inhibitor NM-3 on modulating apoptosis in human gastric cancer cells

AIM: To investigate the synergistic effect of oxymatrine (OM) and angiogenesis inhibitor NM-3 on modulating apoptosis in human gastric cancer cell lines SGC-7901, MKN-45, MKN-74.

METHODS: Human gastric cancer lines SGC-7901, MKN-45, MKN-74 were treated with OM in the absence and presence of NM-3. The inhibitory rates were detected by MTT assay. Synergistic effect of OM and NM-3 on the growth of survivin, bcl-2, bax and p53 in SGC-7901 cells were examined by semiquantitative RT-PCR and Western blotting, and their growth inhibitory effects were also observed on SGC-7901 tumor xenograft in nude mice.

RESULTS: OM combined with NM-3 exhibited a synergistic inhibitory effect on the growth of SGC-7901, MKN-45 and MKN-74 cells in a time-dependent manner. Twenty-four hours after treatment with OM, NM-3 alone and their combination, mRNA expression of survivin and bcl-2 in SGC-7901 cells decreased, p53 mRNA expression increased. OM (4 g/L) combined with NM-3 significantly increased the expression of p53 mRNA and decreased the expression of survivin and bcl-2 compared with either agent alone (193% ± 34% vs 129% ± 12%; 44% ± 18% vs 92% ± 18%; 36 ± 17% vs 93% ± 23%, P < 0.05). Western blotting showed that the synergistic effect of OM and NM-3 on protein translation of survivin, bcl-2 and p53 was in accordance with their mRNAs. Furthermore, OM/NM-3 combination obviously exhibited antitumor growth effect in xenografted human gastric cancer cells SGC-7901 compared with either agent alone.

CONCLUSION: OM combined with NM-3 has synergistic inhibitory effects on human gastric cancer cells in vitro and can suppress the growth of xenografted human gastric cancer cells SGC-7901 in vivo.

Asterosaponin 1, a cytostatic compound from the starfish Culcita novaeguineae, functions by inducing apoptosis in human glioblastoma U87MG cells

Malignant glioblastoma is one of the most common malignant tumors in the neurological system. Asterosaponin 1, a new cytostatic agent from the starfish Culcita novaeguineae appear to exhibit various biological activities, including antitumor effect, but the function and mechanism of this new agent on glioblastoma cells has not previously been determined. In the present study, we investigated the proliferation change of human glioblastoma U87MG cells exposed to different concentrations (2.5-20.0 microg/ml) of asterosaponin 1 for a certain time. The results showed that asterosaponin 1 significantly suppressed U87MG cell proliferation in a time- and dose-dependent manner (IC50 =4.3 microg/ml). Flow cytometric analysis of DNA in U87MG cells showed that asterosaponin 1 induces the prominent appearance of a sub-G1 peak in the cell cycle suggestive of apoptosis identical with the result of annexin V/PI assay. Furthermore, U87MG cells treatment with asterosaponin 1 resulted in nuclear condensation with apoptotic bodies observed by both fluorescence and electron microscopy. Agarose gel electrophoresis of DNA from asterosaponin 1-treated cells revealed a typical "ladder" consistent with apoptotic DNA fragmentation. Western-blot staining showed asterosaponin 1 decreased the expression of Bcl-2 protein and increased the expression of Bax protein. The novel findings suggest that the cytostatic actions of asterosaponin 1 toward U87MG cells result from the induction of cell apoptosis. Overall, our data demonstrate that asterosaponin 1 is fully equipped for an efficient apoptotic killing of glioblastoma cells and suggest that this mechanism may play a critical role in anti-tumor chemotherapy.

Effects of oxymatrine on proliferation and apoptosis in human hepatoma cells

Oxymatrine, a natural quinolizidine alkaloid, has been known having cytotoxic and chemopreventive effects on various cancer cells. To investigate the possible mechanism of oxymatrine's role on cancer cells, in the present study, we examined further the effects of oxymatrine on the growth, proliferation, apoptosis and expression of bcl-2 and p53 gene in human hepatoma SMMC-7721 cells in vitro. Our results show that oxymatrine notably inhibits the growth and proliferation of SMMC-7721 cells and it present a dose-dependence and time-dependence manner within definite reacting dose and time. Oxymatrine block SMMC-7721 cells in G2/M and S phase; prevent cells entering into G0/G1 phase. It results in an obvious accumulation of G2/M and S phase cells while decrease of G0/G1 phase cells. Oxymatrine induce apoptosis of SMMC-7721 cells and apoptotic rate amount to about 60% after treatment with 1.0 mg/ml oxymatrine for 48 h. We also find that oxymatrine down-regulate expression of bcl-2 gene while up-regulate expression of p53 gene. These results demonstrate that oxymatrine inhibit the proliferation and induce apoptosis of human hepatoma SMMC-7721 cells, and suggest that this effect was mediated probably by a significant cell cycle blockage in G2/M and S phase, down-regulation of bcl-2 and up-regulation of p53.