At the protein level, we have shown that in the MCF10-system of genetically related cell lines of differing degrees of malignancy, Smad4 levels were higher in non-malignant MCF10A cells than in the increasingly malignant cell lines MCF10At1k.cl2, MCF10CA1h, and MCF10CA1a, indicating that decreased Smad4 protein expression might accompany tumor progression from early stages on in-situ and in-vivo. This evidence concerns the gene SMAD4 and neoplasm.