Tumour-derived and host-derived nitric oxide differentially regulate breast carcinoma metastasis to the lungs

Abstract

To study the role of nitric oxide (NO) in lung metastasis of breast carcinoma, we isolated two cell clones (H and J) from the parental EMT-6 murine breast carcinoma cell line, based on their differential NO production. In vitro, EMT-6 J cells, but not EMT-6H cells, constitutively expressed inducible NO synthase (NOS II) and secreted high levels of NO. IL-1beta increased NO production in both clones, and TNF-alpha had a synergistic effect on IL-1beta-induced NO production, but NO production by EMT-6 J cells was always higher than by EMT-6H cells. Proliferation, survival and adhesion to lung-derived endothelial cells of both clones were similar and were not affected by NO. In vivo, both clones similarly located in the lungs of syngeneic mice 48 h after injection. However, EMT-6H cells were significantly more tumorigenic than EMT-6 J cells as assessed at later time points. Injection of EMT-6 J cells and simultaneous treatment of mice with aminoguanidine (AG), a NOS II inhibitor, significantly increased tumour formation. Injection of EMT-6H and EMT-6 J cells into NOS II-deficient mice resulted in a significant survival increase as compared with wild-type animals. Simultaneous administration of AG increased the death rate of NOS II-deficient mice injected with EMT-6 J cells. These results demonstrate that: (i) NO does not influence the early stages of tumour metastasis to the lungs and (ii) NOS II expression in tumour cells reduces, while NOS II expression in host cells enhances, tumour nodule development. In conclusion, the cellular origin and the local NO production are critical in the metastatic process.

Effect of Plasma Phospholipid Transfer Protein Deficiency on Lethal Endotoxemia in Mice

“…Cytotoxicity-The toxicity of the supernatants from wild type or PLTP Ϫ/Ϫ splenocytes treated with the high LPS dose was assessed by determining their impact on the ability of EMT-6J cells to adhere to plastic according to the general procedure previously described (47,48). Results were expressed as a percentage of adherent cells, 100% adhesion corresponding to the control value obtained in the absence of LPS.…”

IL-22-Mediated Tumor Growth Reduction Correlates with Inhibition of ERK1/2 and AKT Phosphorylation and Induction of Cell Cycle Arrest in the G2-M Phase

“…Mammary adenocarcinoma EMT6 cells are a widely used model to study different aspects of growth control in cancer (21)(22)(23)(24)(25). A broad variety of chemical compounds (23), growth factor inhibitors, and other biomolecules, including cytokines either alone or in combination with endocrine modulation (22), have been studied using in vitro and in vivo settings in this model.…”

TLR4/IFNγ pathways induce tumor regression via NOS II-dependent NO and ROS production in murine breast cancer models

“…Previously, along with Ridder et al, we reported that this cytokine could be produced by immune cells when they were activated by OM-174. 22,34 Nunez et al 33 evoked such a scenario. They demonstrated that a TLR-activated melanoma produces IFNb, which contributes positively to the antitumor immune response.…”

“…Murine mammary EMT-6H cells were obtained after cloning of the EMT-6 cell line 34 and the mammary NT2 cancer cell line was purchased from the ATCC. Balb/c mice, Fvb mice, IFNg, TLR4, and NOS II knockout mice were purchased from Charles River Laboratory International.…”