To derive a highly metastatic cell line, lung metastases were macro-dissected from the lungs of NT2.5 mammary tumor-bearing NeuN mice, dissociated to single-cell suspensions, and intravenously injected into non-tumor-bearing NeuN mice, after which lung metastases could be harvested again and the process repeated. This evidence concerns the gene RBFOX3 and neoplasm.