[Interaction between Toxoplasma GRA7 dense granule protein and the protein from host macrophages].

OBJECTIVE: To identify the protein from host macrophages which interacted with GRA7 dense granule protein of Toxoplasma gondii, and reveal the relationship between protein interaction and infection process. METHODS: The recombinant GRA7 protein with N-terminal GST tag were used as a bait in in vitro GST Pull-down experiment, the proteins of THP-1 monocytic macrophage cell line were captured and identified by LC-MS/MS proteomics method. The in vivo protein interaction was verified by Co-IP experiment The overexpression of the target host protein by pcDNA3.1 (+) vector in THP-1 macrophage was further used to analyze the relationship between protein interaction and infection process. RESULTS: The captured THP-1 cell protein was about Mr 29000, which was identified as human carbonic anhydrase 1 (hCA1). The significant in vivo protein-protein interaction between GRA7 and hCA1 was verified by Co-IP assay. The overexpression of hCA1 gene in THP-1 macrophage induced a higher propagation speed of Tgondii and the formation of the parasitophorous vacuole, but did nmt influence the number of the parasite. CONCLUSION: There is a significant protein interaction between Toxoplasma GRA7 dense granule protein and hCA1 enzyme from host macrophages, which is positively related with the propagation speed of T. gondii.

[Separation and identification of the surface and secreted proteins in Toxoplasma gondii by biotin labeling and proteomics methods].

OBJECTIVE: To separate and identify the surface proteins and secreted proteins of Toxoplasma gondii tachyzoites of RH strain. METHODS: T. gondii tachyzoites were cultured in Vero cells, and purified by filtration and Percoll cell separation solution. The biotin-labeled tachyzoites were lysed, and the surface and secreted proteins were separated by NeutrAvidin agarose beads. After condensation and SDS-PAGE, the protein were collected, digested and identified by LC/MS-MS. RESULTS: A total of 785 T. gondii proteins were identified, 81 (10.3%) of which were originally annotated as the surface or secreted proteins. Among the highly-expressed (PSM>10) 65 proteins, 43 (66%) were originally annotated as surface or secreted proteins, while the others were predicted unknown proteins. CONCLUSION: The surface and secreted proteins of T. gondii are separated by biotin labeling and avidin chromatography, among which some potential new surface or secreted proteins of T. gondii are identified.

Lentivirus-mediated RNA interference targeting the ObR gene in human breast cancer MCF-7 cells in a nude mouse xenograft model.

BACKGROUND: There is a significant association between obesity and breast cancer, which is possibly due to the expression of leptin. Therefore, it is important to clarify the role of leptin/ObR (leptin receptor) signaling during the progression of human breast cancer. METHODS: Nude mice with xenografts of MCF-7 human breast cancer cells were administered recombinant human leptin subcutaneous via injection around the tumor site. Mice in the experimental group were intratumorally injected with ObR-RNAi-lentivirus, while negative control group mice were injected with the same dose of negative-lentivirus. Tumor size was blindly measured every other day, and mRNA and protein expression levels of ObR, estrogen receptor a (ERa), and vascular endothelial growth factor (VEGF) for each group were determined. RESULTS: Knockdown of ObR-treated xenografted nude mice with a high leptin microenvironment was successfully established. Local injection of ObR-RNAi-lentivirus significantly suppressed the established tumor growth in nude mice. ObR level was significantly lower in the experimental group than in the negative control group, while the amounts of ERa and VEGF expression were significantly lower in the leptin group than in the control group (P < 0.01 for all). CONCLUSIONS: Inhibition of leptin/ObR signaling is essential to breast cancer proliferation and possible crosstalk between ObR and ERa, and VEGF, and may lead to novel therapeutic treatments aiming at targeting ObR in breast cancers.

Effects of exogenous human leptin on heat shock protein 70 expression in MCF-7 breast cancer cells and breast carcinoma of nude mice xenograft model.

BACKGROUND: It is important to identify the multiple sites of leptin activity in obese women with breast cancer. In this study, we examined the effect of exogenous human leptin on heat shock protein 70 (HSP70) expression in MCF-7 human breast cancer cells and in a breast carcinoma xenograft model of nude mice. METHODS: We cultured MCF-7 human breast cancer cells and established nude mice bearing xenografts of these cells, and randomly divided them into experimental and control groups. The experimental group was treated with human leptin, while the control group was treated with the same volume of normal saline. A real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed to quantify the mRNA expression of HSP70 in the MCF-7 human breast cancer cells and in tumor tissues. Western blotting analysis was applied to quantify the protein expression of HSP70 in the MCF-7 cells. Immunohistochemical staining was done to assess the positive rate of HSP70 expression in the tumor tissues. RESULTS: Leptin activated HSP70 in a dose-dependent manner in vitro: leptin upregulated significantly the expression of HSP70 at mRNA and protein levels in MCF-7 human breast cancer cells (P < 0.001). There was no significant difference in expression of HSP70 mRNA in the implanted tumors between the leptin-treated group and the control group (P > 0.05). Immunohistochemical staining revealed no significant difference in tumor HSP70 expression between the leptin-treated group and the control group (P > 0.05). CONCLUSIONS: A nude mouse xenograft model can be safely and efficiently treated with human leptin by subcutaneous injections around the tumor. HSP70 may be target of leptin in breast cancer. Leptin can significantly upregulate the expression of HSP70 in a dose-dependent manner in vitro.

c-Jun N-terminal kinase and nuclear factor κB mediate nitric oxide-induced expression of matrix metalloproteinase-13.

The purpose of this study was to investigate the mechanism of expression of matrix metalloproteinase-13 (MMP-13) induced by nitric oxide (NO). Human chondrocytes (HCs) were stimulated with a NO donor (MAHMA-NONOate), then mitogen-activated protein kinases' (MAPKs) and nuclear factor κB' (NF-κB) activations and MMP-13' expression were assayed by Western blot analysis. Additionally, the intracellular signalling of NO was investigated using the inhibitors of MAPKs and NF-κB. NO-induced MMP-13 expression was not suppressed by extracellular signal-regulated kinase (ERK) inhibitor (PD98059) or inhibitors of p38 kinase (SB203580), but was inhibited by a c-jun terminal kinase (JNK) inhibitor (SP600125) and inhibitors of NF-κB (SN-50). Additionally, SP600125 treatment reduced NF-κB activation, but SN-50 treatment did not significantly affect JNK activation. These results suggest that NO induces MMP-13 expression by JNK and NF-κB activation in HCs.

Clinical significance of PHPT1 protein expression in lung cancer.

BACKGROUND: In our previous studies, we found the expression of 14-kD phosphohistidine phosphatase (PHPT1) was associated with lung cancer cells migration and invasion, and PHPT1 mRNA expression level in lung cancer tissues clinically correlated with lymph node metastasis. In the present study, we aimed to further investigate the expression of PHPT1 protein in lung cancer. METHODS: Expression of PHPT1 protein in tissue samples from 146 lung cancers and 30 normal tissues adjacent to lung cancers was assessed using immunohistochemical method. Fisher's exact test was used to analyze expression patterns of PHPT1 protein in these tissue types. Meanwhile, we studied the correlation between expression of PHPT1 protein and clinicopathological features in lung cancer. RESULTS: Significantly higher expression levels of PHPT1 protein were found in lung cancer samples (53.42%) than in normal tissues adjacent to lung cancer (23.33%) (P = 0.003). Fisher's exact test showed that lung cancer stage positively correlated with expression of PHPT1 protein (P = 0.02), and lung cancer samples with lymph node metastasis showed higher PHPT1 protein expression (P = 0.016) than the samples without lymph node metastasis. CONCLUSIONS: The results of this study agree with findings from our previous study of PHPT1 mRNA expression in lung cancer tissues, and strongly suggest that PHPT1 protein is closely associated with the carcinogenesis and metastasis of lung cancer. Thus, therapy targeting PHPT1 (inhibition or silencing) could be potentially benefited for lung cancer patients.

Regulation of estrogen receptors alpha and beta in human breast carcinoma by exogenous leptin in nude mouse xenograft model.

BACKGROUND: It is essential to clarify the interactions of hormones during the progression of human breast cancer. This study examined the effects of exogenous human leptin on estrogen receptor (ER) alpha and beta in human breast tumor tissue in a nude mouse xenograft model. METHODS: We created nude mice xenografts of MCF-7 human breast cancer cells, and randomly divided them into an experimental group and a control group. The mice in experimental group were injected subcutaneously around tumors with human leptin, while the control group were injected with the same dose of normal saline. A real-time RT-PCR assay was developed to quantify the mRNA of ERalpha, beta in the tumor tissues. Western blotting analyses were used to assess the relative quantities of the ERalpha, beta proteins. RESULTS: Leptin-treated xenografted nude mice were successfully established. The amount of ERalpha mRNA was significantly higher in the leptin group than in the control group (P < 0.01), while the amount of ERbeta mRNA was significantly lower in the leptin group than in the control group (P < 0.01). Western blotting analyses revealed that the ERalpha protein level was significantly higher in the leptin group than in the control group (P < 0.01), while the ERbeta protein level was significantly lower in the leptin group than in the control group (P < 0.01). CONCLUSIONS: Nude mouse xenograft model can be safely and serviceably treated with human leptin by subcutaneous injections around tumor. ERalpha, beta were both targets of leptin in breast cancer. Leptin can up-regulate the expression of ERalpha and down-regulate the expression of the ERbeta in human breast tumor.

Membrane type-1 metalloproteinase mediates nitric oxide-induced activation of matrix metalloproteinase-13.

This article investigates the mechanism of activation of matrix metalloproteinase-13 induced by nitric oxide. SW1353 cells were stimulated with S-nitroso-N-acetyl-D,L-penicillamine, expressions and activities of metalloproteinase-13, and membrane type-1 metalloproteinase were assayed, and a proteolytic activation of recombinant human metalloproteinase-13 was measured in the presence of recombinant human membrane type-1 metalloproteinase. Nitric oxide increased expressions of both matrix metalloproteinases and stimulated the proteolytic processing of metalloproteinase-13 from the pro-enzyme to the final active form. Recombinant human membrane type-1 metalloproteinase was able to process recombinant human metalloproteinase-13 to fully active enzyme. S-nitroso-N-acetyl-D,L-penicillamine had no effect on recombinant human metalloproteinase-13 activity. Nitric oxide scavenger (OxyHb) strongly attenuated nitric oxide-induced proteolytic activation of metalloproteinase-13. Furthermore, tissue inhibitor of metalloproteinase-2 markedly reduced the activation of metalloproteinase-13 in response to nitric oxide. These studies identify membrane type-1 metalloproteinase as a target for nitric oxide, which may be critical for the nitric oxide-induced activation of metalloproteinase-13.