The nucleolus, responsible for ribosome biogenesis, acts as a key center for detecting and responding to cellular stress. Additionally, growing evidence suggests that ribosome biogenesis may play a significant role in promoting metastasis. A proteomic screen of nucleolar protein content between metastatic and non-metastatic breast cancers found that metastatic breast cancer cell lines have a unique nucleolar proteome signature as compared to non-metastatic breast cancer cell lines.