Abstract Increased glucose uptake and glycolysis are main metabolic characteristics of malignant cells. The glucose transporter-1 (GLUT-1), GLUT-3 and recently GLUT-12 have been shown in breast cancer cells in which estrogen play a critical role on its regulation and also associated with poor prognosis. However. the stage-specific GLUT regulation during the process of mammary carcinogenesis is unclear. In the present study we are aiming to study the GLUT expression pattern in an in vitro-in vivo model of estrogen induced carcinogenesis in which the human breast epithelial cell line MCF-10F is considered the normal counterpart E2 the transformed, C5 the invasive and T4 the tumorigenic stage. The gene expression of GLUTs was correlated with the ductulogenic pattern in a collagen matrix and the invasive properties using the Boyden chamber The RT-PCR data showed that the GLUT1 expression was downregulated in MCF10F after the treatment with 17β-estradiol (E2) and in the invasive cell type (C5), but not in the tumor cells (T4), which had no changes compared to MCF10F. C5 and T4 cells showed the highest rate of GLUT-3 expression. These cells were also found to be associated with loss of ductulogenesis, solid mass formation and higher invasion capacity. Whereas, GLUT-12 is downregulated in invasive and tumorigenic cells. We conclude that the estrogen-induced malignant transformation is associated with remarkably GLUT-3 expression, GLUT-1 re-expression at further stages, as well as GLUT-12 downregulation for transformed MCF-10F cells. (This work was supported by grant R21 ES015894from the NIEHS) Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5152.