Ras/ERK signaling pathway mediates activation of the p21WAF1 gene promoter in vascular smooth muscle cells by platelet-derived growth factor

Tylophorine reduces protein biosynthesis and rapidly decreases cyclin D1, inhibiting vascular smooth muscle cell proliferation in vitro and in organ culture

BACKGROUND

Tylophorine (TYL) is an alkaloid with antiproliferative action in cancer cells. Vascular smooth muscle cell (VSMC) proliferation and neointima formation contribute to restenosis after percutaneous coronary interventions.

HYPOTHESIS/PURPOSE

Our goal was to examine the potential of TYL to inhibit VSMC proliferation and migration, and to dissect underlying signaling pathways.

STUDY DESIGN AND METHODS

TYL was administered to platelet-derived growth factor (PDGF-BB)-stimulated, serum-stimulated, quiescent and unsynchronized VSMC of rat and human origin. BrdU incorporation and resazurin conversion were used to assess cell proliferation. Cell cycle progression was analyzed by flow cytometry of propidium iodide-stained nuclei. Expression profiles of proteins and mRNAs were determined using western blot analysis and RT-qPCR. The Click-iT OPP Alexa Fluor 488 assay was used to monitor protein biosynthesis.

RESULTS

TYL inhibited PDGF-BB-induced proliferation of rat aortic VSMCs by arresting cells in G1 phase of the cell cycle with an IC₅₀ of 0.13 µmol/l. The lack of retinoblastoma protein phosphorylation and cyclin D1 downregulation corroborated a G1 arrest. Inhibition of proliferation and cyclin D1 downregulation were species- and stimulus-independent. TYL also decreased levels of p21 and p27 proteins, although at later time points than observed for cyclin D1. Co-treatment of VSMC with TYL and MG132 or cycloheximide (CHX) excluded proteasome activation by TYL as the mechanism of action. Comparable time-dependent downregulation of cyclin D1, p21 and p27 in TYL- or CHX-treated cells, together with decreased protein synthesis observed in the Click-iT assay, suggests that TYL is a protein synthesis inhibitor. Besides proliferation, TYL also suppressed migration of PDGF-activated VSMC. In a human saphenous vein organ culture model for graft disease, TYL potently inhibited intimal hyperplasia.

CONCLUSION

This unique activity profile renders TYL an interesting lead for the treatment of vasculo-proliferative disorders, such as restenosis.

Retinoic acid-induced survival effects in SH-SY5Y neuroblastoma cells

Neuroblastoma is a malignant childhood cancer arising from the embryonic sympathoadrenal lineage of the neural crest. Retinoic acid (RA) is included in the multimodal therapy of patients with high-risk neuroblastoma to eliminate minimal residual disease. However, the formation of RA-resistant cells substantially lowers 5-year overall survival rates. To examine mechanisms that lead to treatment failure, we chose human SH-SY5Y cells, which are known to tolerate incubation with RA by activating the survival kinases Akt and extracellular signal-regulated kinase 1/2. Characterization of downstream pathways showed that both kinases increased the phosphorylation of the ubiquitin ligase mouse double minute homolog 2 (Mdm2) and thereby enhanced p53 degradation. When p53 signaling was sustained by blocking complex formation with Mdm2 or enhancing c-Jun N-terminal kinase (JNK) activation, cell viability was significantly reduced. In addition, Akt-mediated phosphorylation of the cell-cycle regulator p21 stimulated complex formation with caspase-3, which also contributed to cell protection. Thus, treatment with RA augmented survival signaling and attenuated basal apoptotic pathways in SH-SY5Y cells, which increased cell viability.

Curcumin potentiates antitumor activity of cisplatin in bladder cancer cell lines via ROS-mediated activation of ERK1/2

Resistance of bladder cancer to cisplatin is a major obstacle to successful treatment. In the current study, we investigated the apoptotic effects of curcumin and cisplatin co-treatment in 253J-Bv(p53 wild-type) and T24(p53 mutant) bladder cancer. We found that curcumin and cisplatin co-treatment primarily targets reactive oxygen species(ROS) and extracellular regulated kinase(ERK) signaling during the apoptosis induction in bladder cancer. The apoptosis rate in 253J-Bv and T24 cells co-treated with curcumin and cisplatin was increased compared to that in cells exposed to single-agent treatment conditions. Also, caspase-3 activation and ROS production were observed in both cells treated with curcumin and cisplatin, together with upregulation of p-MEK and p-ERK1/2 signaling. NAC(ROS scavenger) and U0126(ERK inhibitor) inhibited apoptosis induced by curcumin and cisplatin. In addition, when 253J-Bv cells were co-treated with curcumin and cisplatin, p53 and p21 expression levels were markedly increased when compared to controls. Unlike 253J-Bv cells, T24 cells were co-treated with curcumin and cisplatin revealed an induction of apoptosis through decreased p-signal transducer and activator of transcription 3(STAT3) expression. Moreover, pretreatment with U0126 suppressed curcumin and cisplatin-induced upregulation of p53, p21, and p-STAT3 and downregulation of survival proteins in both cells. In conclusion, co-treatment with curcumin and cisplatin synergistically induced apoptosis through ROS-mediated activation of ERK1/2 in bladder cancer.

H2S-releasing nanoemulsions: a new formulation to inhibit tumor cells proliferation and improve tissue repair

The improvement of solubility and/or dissolution rate of poorly soluble natural compounds is an ideal strategy to make them optimal candidates as new potential drugs. Accordingly, the allyl sulfur compounds and omega-3 fatty acids are natural hydrophobic compounds that exhibit two important combined properties: cardiovascular protection and antitumor activity. Here, we have synthesized and characterized a novel formulation of diallyl disulfide (DADS) and α-linolenic acid (ALA) as protein-nanoemulsions (BAD-NEs), using ultrasounds. BAD-NEs are stable over time at room temperature and show antioxidant and radical scavenging property. These NEs are also optimal H2S slow-release donors and show a significant anti-proliferative effect on different human cancer cell lines: MCF-7 breast cancer and HuT 78 T-cell lymphoma cells. BAD-NEs are able to regulate the ERK1/2 pathway, inducing apoptosis and cell cycle arrest at the G0/G1 phase. We have also investigated their effect on cell proliferation of human adult stem/progenitor cells. Interestingly, BAD-NEs are able to improve the Lin- Sca1+ human cardiac progenitor cells (hCPC) proliferation. This stem cell growth stimulation is combined with the expression and activation of proteins involved in tissue-repair, such as P-AKT, α-sma and connexin 43. Altogether, our results suggest that these antioxidant nanoemulsions might have potential application in selective cancer therapy and for promoting the muscle tissue repair.

ERK inhibition enhances TSA-induced gastric cancer cell apoptosis via NF-κB-dependent and Notch-independent mechanism

AIMS

To analyze the combined impact of the histone deacetylase inhibitor (HDACI) Trichostatin A (TSA) and the extracellular-signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 on gastric cancer (GC) cell line SGC7901 growth.

MAIN METHODS

SGC7901 cells were treated with TSA, PD98059 or with a TSA-PD98059 combination. Effects of drug treatment on tumor cell proliferation, apoptosis, cell cycle progression, and cell signaling pathways were investigated by MTS assay, flow cytometry, Western blotting, chromatin immunoprecipitation (ChIP) assay, electrophoretic mobility shift assay (EMSA), and luciferase reporter assay, respectively.

KEY FINDINGS

PD98059 enhanced TSA-induced cell growth arrest, apoptosis and activation of p21(WAF1/CIP1), but reversed TSA-induced activation of ERK1/2 and nuclear factor-κB (NF-κB). TSA alone up-regulated Notch1 and Hes1, and down-regulated Notch2, but PD98059 did not affect the trends of Notch1 and Notch2 induced by TSA. Particularly, PD98059 did potentiate the ability of TSA to down-regulate phospho-histone H3 protein, but increased levels of the acetylated forms of histone H3 bound to the p21(WAF1/CIP1) promoter, leading to enhanced expression of p21(WAF1/CIP1) in SGC7901 cells.

SIGNIFICANCE

PD98059 synergistically potentiates TSA-induced GC growth arrest and apoptosis by manipulating NF-κB and p21(WAF1/CIP1) independent of Notch. Therefore, concomitant administration of HDACIs and ERK1/2 inhibitors may be a promising treatment strategy for individuals with GC.

Role of Cell Division Autoantigen 1 (CDA1) in Cell Proliferation and Fibrosis

Cell Division Autoantigen 1 (CDA1) was discovered following screening a human expression library with serum from a patient with Discoid Lupus Erythematosus. CDA1, encoded by TSPYL2 on the X chromosome, shares anti-proliferative, pro‑fibrotic properties with TGF-β. It inhibits cell growth through p53, pERK1/2, p21‑mediated pathways, is implicated in tumorigenesis, the DNA damage response. Its pro-fibrotic property is mediated through cross-talk with TGF-β that results in upregulation of extracellular matrix proteins. The latter properties have identified a key role for CDA1 in diabetes associated atherosclerosis. These dual properties place CDA1 as an attractive molecular target for treating tumors, vascular fibrosis including atherosclerosis, other vascular disorders associated with enhanced TGF-β action, tissue scarring.

Modulation of expression and cellular distribution of p21 by macrophage migration inhibitory factor

Background

The pleiotropic protein MIF, (macrophage migration inhibitory factor), has been demonstrated to modulate several key proteins governing cell cycle control and is considered to contribute to cell growth and differentiation. In this study we investigated the effect of MIF on the expression and cellular distribution of the CDK inhibitor p21.

Methods

The effect of endogenous MIF on p21 expression and distribution was examined by comparing murine dermal fibroblasts derived from wt and MIF -/- mice. The effect of MIF on cell growth and apoptotic rates was compared using ³H-Thymidine incorporation assays and annexin V/PI assays respectively. Total p21 protein levels were compared using flow cytometry and western blotting. p21 mRNA was assessed by RT-PCR. Intracellular p21 staining was performed to assess cellular distribution of total protein. To further confirm observations siRNA was used to knockdown MIF protein in wt cells. Cell cycle analysis was performed using PI incorporation assays.

Results

MIF-/- murine dermal fibroblasts exhibited reduced proliferative responses and were more susceptible to apoptosis. This was associated with reduced p21 expression and nuclear distribution. Treatment with recombinant MIF protein was demonstrated to reduce both basal and induced apoptosis and increase nuclear p21 expression. Reduced nuclear p21 expression was also observed in MIF siRNA treated wt cells.

Conclusion

The results demonstrate that in the absence of MIF p21 expression and nuclear distribution is reduced which is associated with a reduction in cell growth and increased apoptosis. MIF may therefore play a role in maintaining homeostatic control of p21.

Regulation of p21Waf1 expression and TNFalpha biosynthesis by glutathione modulators in PMA induced-THP1 differentiation: involvement of JNK and ERK pathways

Oxidative modifications of proteins are fundamental biochemical events that regulate cellular signaling, protein expression, and function. The redox status is balanced by reductants in which GSH plays a major role. This study investigated whether or not p21Waf1 expression and TNFalpha biosynthesis in macrophage differentiation/activation were regulated by GSH modulators and whether or not the JNK and ERK pathway were involved. We observed an increase of p21Waf1 expression and TNFalpha biosynthesis in the THP1 monocyte/macrophage cell line treated with PMA. Treatment of THP1 cultures with NAC prior to adding PMA abrogates the expression of p21Waf1 mRNA and decreases the level of TNFalpha whereas GSH depletion by BSO enhances the levels of TNFalpha with minor effects on p21Waf1 expression. To assess whether or not ERK and JNK were involved in the redox mechanism of p21Waf1 and TNFalpha, we used pharmacological inhibitors for JNK and ERK. Both PD98095 and dicoumarol were capable of blocking TNFalpha production but had only a small effect on p21Waf1 expression. We next observed that activation of JNK was significantly inhibited in cells pretreated with NAC with no effect on ERK. Taken together, our findings suggest that the modulation of GSH regulate the magnitude the cell response to PMA in which JNK and ERK have a particular role in redox signaling.

Antiproliferative autoantigen CDA1 transcriptionally up-regulates p21(Waf1/Cip1) by activating p53 and MEK/ERK1/2 MAPK pathways

We previously reported that overexpression of cell division autoantigen 1 (CDA1) in HeLa cells arrests cell growth and inhibits DNA synthesis at S-phase. Here we show that CDA1-induced arrest of cell growth is accompanied by increases in protein and mRNA levels of the cyclin-dependent kinase (Cdk) inhibitor protein, p21(Waf1/Cip1) (p21). Both p21 induction and cell growth arrest are reversed when CDA1 expression is inhibited. CDA1 also increases p53 protein, but not its mRNA, in a time- and dose-dependent manner. MDM2, a ubiquitin ligase regulating p53 degradation, is inactivated by CDA1, suggesting that p53 protein accumulation is due to decreased protein degradation. Knockdown of p53, using siRNA targeting two sites of p53 mRNA, abrogates transcriptional induction of p21 by CDA1. Deletion of the p53 responsive element in the distal region of p21 promoter attenuates promoter activity in response to CDA1. DNA damage caused by camptothecin treatment increases mRNA and protein levels of CDA1, accompanied by induction of p53. The DNA damage-induced p53 induction is markedly attenuated by CDA1 knockdown. CDA1 induces phosphorylation of ERK1/2(p44/42), an activity blocked by PD98059 and U0126, inhibitors of the upstream kinase MEK1/2. The MEK inhibitors also block induction of p21 mRNA and abrogate p21 promoter activity stimulated by CDA1. Cell cycle kinases, Cdk1, -2, -4, and -6 are inhibited by CDA1 overexpression. We conclude that CDA1 induces p53- and MEK/ERK1/2 MAPK-dependent expression of p21 by acting through the p53 responsive element in the p21 promoter and that this contributes to its antiproliferative activity.

Regulation of Smooth Muscle Cell Proliferation by β-Catenin/T-Cell Factor Signaling Involves Modulation of Cyclin D1 and p21 Expression

We previously observed that stimulation of vascular smooth muscle cell (VSMC) proliferation with growth factors is associated with dismantling of cadherin junctions and nuclear translocation of β-catenin. In this study we demonstrate directly that growth factors stimulate β-catenin/T-cell factor (TCF) signaling in primary VSMCs. To determine whether β-catenin/TCF signaling regulates VSMC proliferation via modulation of the β-catenin/TCF responsive cell cycle genes, cyclin D1 and p21, we inhibited β-catenin/TCF signaling by adenoviral-mediated over-expression of N-Cadherin, ICAT (an endogenous inhibitor of β-catenin/TCF signaling), or a dominant negative (dn) mutant of TCF-4. N-cadherin, ICAT or dnTCF-4 over-expression significantly reduced proliferation of isolated human VSMCs by approximately 55%, 80%, and 45% respectively. Similar effects were observed in human saphenous vein medial segments where proliferation was reduced by approximately 55%. Transfection of dnTCF-4 in the ISS10 human VSMC line significantly lowered TCF and cyclin D1 reporter activity but significantly elevated p21 reporter activity, indicating regulation of these genes by β-catenin/TCF signaling. In support of this, over-expression of N-cadherin, ICAT or dnTCF-4 in isolated human VSMCs significantly lowered levels of cyclin D1 mRNA and protein levels. In contrast, over-expression of N-Cadherin, ICAT or dnTCF4 significantly elevated p21 mRNA and protein levels. In summary, we have demonstrated that increasing N-cadherin and inhibiting β-catenin/TCF signaling reduces VSMC proliferation, decreases the expression of cyclin D1 and increases levels of the cell cycle inhibitor, p21. We therefore suggest that the N-cadherin and β-catenin/TCF signaling pathway is a key modulator of VSMC proliferation via regulation of these 2 β-catenin/TCF responsive genes.