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Haleh Shahidipour, Sarah E Coupland, Diana Moss, Bertil E Damato, Helen Kalirai, ; Chick embryo model systems to study uveal melanoma metastasis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5075.
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© ARVO (1962-2015); The Authors (2016-present)
Almost fifty percent of patients with uveal melanoma (UM) will develop fatal metastatic disease, which occurs predominantly in the liver. Despite significant improvements in the treatment of the ocular tumour, patient mortality has not improved and most metastatic lesions remain untreatable. Little is known about the mechanisms by which UM cells metastasise to and colonise the liver. We have developed a chick embryo model of spontaneous and direct metastasis allowing for the processes of UM tumour development, intravasation, extravasation and dissemination to be studied.
At embryonic day 3, a small window was made in the shell and GFP labelled Omm1 UM cells were either: 1) inoculated onto the lowered chorioallantoic membrane (CAM) - spontaneous metastasis model; or 2) injected directly into the circulation of the chick embryo - direct metastasis model. At embryonic day 7, tumour nodules that had formed on the CAM were excised, fixed in 10% neutral buffered formalin and embedded for immunohistochemical analyses. Internal organs were examined for the presence of UM cells in both model systems under a fluorescence microscope, prior to fixation and embedding. All experiments were repeated at least three times.
Omm1 UM cells formed tumour nodules within the CAM, at embryonic day 14, which were associated with an overlying network of chick embryo blood vessels. Immunohistochemical analyses of cross sections of the tumour nodules demonstrated the presence of MelanA positive cells surrounded by chick embryo CAM, internal blood vessels and a high Ki67 staining index. Omm1 cells were not observed in any internal organs in the spontaneous metastasis model after seven days. Following direct injection of Omm1 cells into the chick embryo circulation, tumour cell deposits were observed microscopically in the eye, liver and kidneys after seven days. Immunohistochemistry showed numerous micro- and macro- metastatic liver deposits which stained positively for MelanA and demonstrated a low Ki67 growth fraction.
Chick embryo metastasis model systems can be used to provide important information on the specific behavioural patterns of UM cells during individual stages of metastatic dissemination. Future studies will utilise these systems to study the functional mechanisms of individual metastasis-related genes.
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