18251
The interaction of CXCR4 with CXCL12 ( SDF - 1 ) plays a critical role in cancer metastasis by facilitating the homing of tumor cells to metastatic sites .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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