Breast cancer remains one of the leading causes of death in women and most patients die from the tumormetastasis. Our long-term goal is to understand the molecular mechanisms of metastasis so that noveltherapeutic strategy can be designed. EMT (epithelial to mesenchymal transition) is a determining step for acancer cell to progress from a non-invasive to invasive state. Disruption of intercellular adhesion via loss of E-cadherin, the defining event for EMT, is often correlated with gain of the matrix metalloproteinases (MMP) thatcatalyze proteolytic matrix remodeling important for tumor cell invasion. Such a correlation has been found ininvasive breast cancer. However how EMT is regulated during and contributes to breast cancer metastasis islargely unknown. We previously identified Kr ppel-like transcription factor 8 (KLF8) as a downstream effectorof FAK that plays a crucial role in breast cancer metastasis. Recently, we found that KLF8 is important foroncogenic transformation and overexpressed in invasive human breast cancer, suggesting an uninvestigatedrole for KLF8 in breast cancer metastasis. Our preliminary studies, using inducible and constitutive expressionof KLF8 in MCF-10A cells, suggest that KLF8 is a potent inducer of EMT and invasion by repressing E-cadherin and activating MMP9, MMP2 and MT1-MMP. We also show that KLF8 plays a key role in the loss ofE-cadherin and gain of the MMPs in invasive human breast cancer cells and that aberrant KLF8 elevation istightly correlated with the loss of E-cadherin in patient specimens. Finally, our pilot studies suggest a role forKLF8 in supporting MDA-MB-231 lung metastasis. These results strongly support our hypothesis that KLF8promotes breast cancer metastasis by initiating EMT and invasion through repression of E-cadherin andactivation of the MMPs. We propose three specific aims to test this hypothesis using in semi-in vivo 3D acinusculture and in vivo mouse models and our MCF-10A cells expressing inducible KLF8 and MDA-MB-231 cellsexpressing inducible KLF8 sh RNA.
In Aim 1, we will determine the role of E-cadherin and the MMPs in KLF8-induced EMT and invasion by genetically modifying these proteins.
In Aim 2, we will identify the molecularmechanisms by which E-cadherin, the MMPs and intergrin-FAK signaling interplay to regulate KLF8-inducedEMT and invasion using genetic, biochemical or pharmacological approaches.
In Aim 3, we will determine therole of KLF8 in tumor metastasis using a mouse model of human breast cancer and bioluminescence imaging.We will also evaluate role for other EMT regulators such as Snails, ZEBs and Twist in the regulation ofmetastasis by KLF8. Completion of this project will shed new lights on mechanisms responsible for breastcancer metastasis which may leads to new therapeutic intervention.
Our identification of KLF8 as an inducer of EMT and invasion and a regulator of E-cadherin and MMPs is novel and significant. Results derived from this proposal will shed new lights on mechanisms responsible for breast cancer metastasis which may leads to new therapeutic intervention.
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