Identifying inhibitors of epithelial-mesenchymal transition by connectivity map-based systems approach

Acquisition of mesenchymal phenotype by epithelial cells by means of epithelial-mesenchymal transition (EMT) is considered as an early event in the multistep process of tumor metastasis. Therefore, inhibition of EMT might be a rational strategy to prevent metastasis.

Using the global gene expression profile from a cell culture model of transforming growth factor-β (TGF-β)-induced EMT, we identified potential EMT inhibitors. We used a publicly available database (www.broad.mit.edu/cmap) comprising gene expression profiles obtained from multiple different cell lines in response to various drugs to derive negative correlations to EMT gene expression profile using Connectivity Map, a pattern matching tool.

Experimental validation of the identified compounds showed rapamycin as a novel inhibitor of TGF-β signaling along with 17-AAG, a known modulator of TGF-β pathway. Both of these compounds completely blocked EMT and the associated migratory and invasive phenotype. The other identified compound, LY294002, demonstrated a selective inhibition of mesenchymal markers, cell migration and invasion, without affecting the loss of E-cadherin expression or Smad phosphorylation.

Our data reveal that rapamycin is a novel modulator of TGF-β signaling, and along with 17-AAG and LY294002, could be used as therapeutic agent for inhibiting EMT. This study demonstrates the potential of a systems approach in identifying novel modulators of a complex biological process.