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Xenograft models, and in particular the mouse xenograft model, where human cancer cells are transplanted into immunocompromised mice, have been used extensively in cancer studies. Although these models have contributed enormously to our understanding of cancer biology, the zebrafish xenograft model offers several advantages over the mouse model. Zebrafish embryos can be easily cultured in large quantities, are small and easy to handle, making it possible to use a high number of embryos for each experimental condition. Young embryos lack an efficient immune system. Therefore the injected cancer cells are not rejected, and the formation of primary tumors and micrometastases is rapid. Transparency of the embryos enables imaging of primary tumors and metastases in an intact and living embryo. Here we describe a method where GFP expressing tumor cells are injected into pericardial space of zebrafish embryos. At four days post-injection, the embryos are imaged and the formation of primary tumor and distant micrometastases are analyzed.

Practical laboratory activities have become more common in primary and secondary education with the current curriculum. In lower secondary school, laboratory work in chemistry and physics has been used even longer. The central issues of laboratory work becoming more common are how the activities are organized, safety of the laboratory work, and evaluation. Laboratory work has been taken into account in evaluation in many different ways, for example, a written assignment has been complemented with a practical assignment. The evaluation method provides those who can practically and manually demonstrate activeness and skill with the possibility to succeed.