MME and breast cancer: CD10 is a cell surface type 2 metalloprotease that can degrade various signaling peptides.[27, 34] To investigate whether CD10 in CAFs exerts its functions by mediating peptide degradation, high‐performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS) was used to compare peptide profiles in interstitial fluid of breast cancer samples with high or low CD10+ CAF infiltration (Figure 3A).