While metadherin was reported to be a surface protein mediating lung metastasis of breast cancer,[23] this protein has usually been reported to localize in other cellular compartments such as nucleus and endoplasmic reticulum.[24] Using an antibody targeting an extracellular region of metadherin, our results indicated the cell surface localization of metadherin (Figure 4d). Here, MTDH is linked to breast cancer.