When transgenic mice that expressed high levels of S100A4, but did not show any phenotypic effect, were mated with mice that expressed mice mammary tumor virus (MMTV)-neu transgene and succumbed to stochastic mammary neoplasia, the expression of S100A4 was observed to correlate with the regions of invasion of primary lesions and metastases, suggesting that S100A4 has to couple with an oncogene to cause cancer, and therefore, it shows no effect by itself in transgenic mice [35, 36]. This evidence concerns the gene S100A4 and cancer.