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What is Which of these genes promote epithelial-mesenchymal transition and are important metastatic genes in epithelial tumors? and explain in detail?
Metasis oncogenes are SNAIL and TWIST, which encode transcription factors whose primary function is to promote epithelial-to-mesenchymal transition (EMT). 
In EMT, carcinoma cells downregulate certain epithelial markers (e.g., E-cadherin) and upregulate certain mesenchymal markers  (e.g.,  vimentin, smooth muscle actin).
EMT has been documented mainly in breast carcinoma.

Reference-Robbins BASIC PATHOLOGY 10th edition pg-223