Taking the observations together, we successfully constructed a simple, efficient and complete model to study the influence of maspin localization on breast cancer cell growth, which can be used for further studies using transient transfection.Usefulness of this model was confirmed during our attempts to select cancer cell lines expressing nuclear maspin (maspin-NLS-EGFP), which failed completely and always within 2-3 weeks of selection. This evidence concerns the gene SERPINB5 and breast cancer.