[Show abstract][Hide abstract] ABSTRACT: Polybrominated diphenyl ethers (PBDEs), commonly used in building materials, electronics, plastics, polyurethane foams, and textiles, are health hazards found in the environment.
In this study we investigated the effects of PBDE-209, a deca-PBDE, on the regulation of growth and apoptosis of breast, ovarian, and cervical cancer cells as well as the underlying protein alterations.
We used MCF-7 and MCF-7/ADR (multidrug-resistant MCF-7) breast cancer cell lines, the HeLa cervical cancer cell line, the OVCAR-3 ovarian cancer cell line, and the normal CHO (Chinese hamster ovary) cell line to assess the effects of PBDE-209 using cell viability, immunofluorescence, and flow cytometric assays. Western blot assays were used to detect changes in protein expression. To assess the effects of PBDE-209 on apoptosis, we used the protein kinase Cα (PKCα) inhibitor Gö 6976, the extracellular signal-regulated kinase (ERK) inhibitor PD98059, and tamoxifen.
Our data indicate that PBDE-209 increased viability and proliferation of the tumor cell lines and in CHO cells in a dose- and time-dependent manner. PBDE-209 also altered cell cycle distribution by inducing the S phase or G2/M phase. Furthermore, PBDE-209 partially suppressed tamoxifen-induced cell apoptosis in the breast cancer cell lines (MCF-7 and MCF-7/ADR) but suppressed Gö 6976- and PD98059-induced apoptosis in all cell lines. At the molecular level, PBDE-209 enhanced PKCα and ERK1/2 phosphorylation in the cell lines.
Our data demonstrate that PBDE-209 is able to promote proliferation of various cancer cells from the female reproductive system and normal ovarian CHO cells. Furthermore, it reduced tamoxifen, PKCα, and ERK inhibition-induced apoptosis. Finally, PBDE-209 up-regulated phosphorylation of PKCα and ERK1/2 proteins in tumor cells and in CHO cells.
Preview · Article · Apr 2012 · Environmental Health Perspectives
[Show abstract][Hide abstract] ABSTRACT: This study was designed to investigate the role of protein kinase C (PKC) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in tamoxifen (TAM)-induced apoptosis and drug resistance in human breast cancer cells. Drug-sensitive, or estrogen receptor (ER)-positive human breast carcinoma cells (MCF-7) and the multi-drug-resistant variant (ER-negative) MCF-7/ADR cells were treated with doses of TAM for various periods of time. Cell viability and apoptosis were assessed using cell counting, DNA fragmentation and flow cytometric analysis. We found that TAM administration caused a significant increase in apoptosis of MCF-7 cells but not MCF-7/ADR cells. Western blot analysis revealed enhanced expression of PKCδ but decreased expression of PKCα in ER-positive MCF-7 cells; while ER-negative MCF-7/ADR cells had decreased levels of PKCδ and increased levels of PKCα. Interestingly, we observed that in MCF-7 cells, TAM stimulated apoptosis by promoting rapid activation of PKCδ, antagonizing downstream signaling of ERK phosphorylation; while in MCF-7/ADR cells, TAM upregulated PKCα, which promoted ERK phosphorylation. These results suggest that PKCδ enhances apoptosis in TAM-treated MCF-7 cells by antagonizing ERK phosphorylation; while the PKCα pathway plays an important role in TAM-induced drug resistance by activating ERK signaling in MCF-7/ADR cells. The combination of TAM with PKCα and ERK inhibitors could promote TAM-induced apoptosis in breast cancer cells.
No preview · Article · Mar 2012 · Oncology Reports
[Show abstract][Hide abstract] ABSTRACT: The multi functionalization of isotactic polypropylenes (iPP) with glycidyl methacrylate (GMA) was carried out by in situ chlorinating graft copolymerization (ISCGC), in which chlorine (Cl2) is used as a radical initiator as well as a radical scavenger. The molecular weight measurement indicates that functionalized
iPP with controlled degradation could be obtained because the unstable radicals that induce iPP degradation could be terminated
quickly by chlorine. Owing to the unique allyl-containing structure of GMA, multi functionalized iPP could be synthesized
under the effect of chlorine, which contained both epoxy groups and C=C double bonds as well as trace amount of chlorine atoms
in the functionalized polymer structure. The structure of both the functionalization polymer and homopolymer formed in this
system were analyzed by FTIR and 1H NMR. The mechanism of grafting reaction, iPP chain degradation, and GMA homopolymer formation scheme in ISCGC were proposed.
The thermal properties of the functionalized polymer are also discussed.
Keywordspolypropylene (PP)–functionalization of polymers–graft copolymers–glycidyl methacrylate–structure
No preview · Article · Sep 2011 · Macromolecular Research
[Show abstract][Hide abstract] ABSTRACT: Acrylic acid (AA) was grafted firstly onto high density polyethylene (HDPE) by in-situ chlorinating graft copolymerization (ISCGC), so a graft copolymer composed of chlorinated polyethylene (CPE) as backbone and poly (acrylic acid) (PAA) as branched chains was synthesized. And subsequently the preparation of its carboxylated ionmers was studied. This work was focused on discussing the reaction process for grafting AA onto HDPE by ISCGC and the preparing of carboxylated ionmers of CPE. In this paper, the structure of graft copolymer and the ionomer were characterized mainly by FT-IR, gel permeation chromatography (GPC) and graft degree (GD). The influence factors which related to the main and side reactions, including the monomer concentration, chlorine contents of the product, and reaction temperature were investigated. Additionally, effects of these factors on reaction process controlling were described. The aim of above is to investigate how CPE-cg-PAA and its sodium-salt ionomer were prepared.
[Show abstract][Hide abstract] ABSTRACT: Acrylic acid (AA) was grafted onto high density polyethylene (HDPE) by in-situ chlorination graft copolymerization (ISCGC), yielding a graft copolymer composed of chlorinated polyethylene (CPE) as backbone and poly (acrylic acid) (PAA) as branch chains. The reaction process and the preparation of its carboxylated ionomers were studied. The structure of the graft copolymer and the ionomer were characterized by FT-IR, gel permeation chromatography (GPC) and degree of grafting (GD). The influence of factors related to the main and side reactions, including the monomer concentration, chlorine contents of the product, and reaction temperature were investigated. Additionally, the effects of these factors on the reaction are described. The aim of the research was to investigate how CPE-cg-PAA and its sodium-salt ionomer could be prepared and their relative effect on thermal and mechanical properties.
No preview · Article · Jan 2011 · Journal of Macromolecular Science Part B
[Show abstract][Hide abstract] ABSTRACT: The development of multidrug resistance (MDR) in breast cancer patients is a serious therapeutic problem. The role of signal transduction in the development of MDR has drawn intensive attention recently. In this study, the role of c-Jun N-terminal kinase (JNK) pathway in MDR, specifically regulated by PKCα, was investigated in MCF-7/ADR cells. MTT, DNA ladder and flow cytometry were used to detect cell growth inhibition or apoptosis while Western blot was used to detect the activation of proteins. Compared with MCF-7 cells, the cell growth inhibition and apoptosis induced by tamoxifen (TAM) could not be detected in MCF-7/ADR cells, but the expression of PKCα in MCF-7/ADR cells was higher. And, Western blot results showed that JNK was activated by TAM in MCF-7 cells while not in MCF-7/ADR cells, even at very high doses. In addition, sp600125, the inhibitor of JNK, decreased the percentage of apoptosis induced by TAM in MCF-7 cells. These data showed that PKCα and JNK were key regulators in the apoptosis of MCF-7/ADR cells. Furthermore, PKCα being the upstream of JNK in inhibiting apoptosis was suggested by using Go6976, the specific PKCα inhibitor, in the presence or absence of sp600125. This study highlighted an important signaling pathway involved in MDR regulated by PKCα in MCF-7/ADR breast cancer cells and implied that JNK might be an important downstream target of PKCα in this cellular context.
No preview · Article · Nov 2010 · Experimental and toxicologic pathology: official journal of the Gesellschaft fur Toxikologische Pathologie
[Show abstract][Hide abstract] ABSTRACT: Data have shown that tamoxifen (TAM) can be used to treat not only breast cancer with positive estrogen receptor (ER), but also negative ER including human glioma. However, the molecular mechanism of this drug against different kinds of cancers remains to be elucidated. In this study, we provided the evidence that PKCalpha-ERK1/2 signaling pathway plays a negative role in TAM-induced C6 cell apoptosis, and a combined utilization of TAM with inhibitors of PKCalpha or ERK1/2 could enhance the effectiveness of TAM on inhibiting tumor growth.
No preview · Article · Jul 2009 · Cancer Investigation