Tumor invasion plays an important first step in complex metastatic process. To understand this physiological event, over the past few decades scientists have tried to untilize different animal species to help study the invasive properties of malignant tumors. Serveral alternative measurements, however, have been developed to replace animal experimentation. These in vitro invasion techniques not only provide a valid model but also offer a rapid, smiple and versatile system for cancer metastasis research. Here we reviewed the overall progress of these invasio assays and, based on the current problems, proposed a better, cheaper and more consistent chamber design for the in vitro tumor invasion assay.
