7043
In an effort to isolate genes with down - regulated expression at the mRNA level during oncogenic transformation of human mammary epithelial cells ( MECs ) , we performed subtractive hybridization between normal MEC strain 76N and its radiation - transformed tumorigenic derivative 76R - 30 .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
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