In order to identify novel and specific targets upregulated on the surface of rhabdomyosarcoma (RMS) cells by mass spectrometry (MS), we initially compared two methods for isolation of membrane/surface proteins: the first based on biotin labeling of cell surface proteins with the cleavable EZ-Link-Sulfo-NHS-SS-biotin, followed by isolation with a NeutrAvidin agarose column, and reducing elution with dithiothreitol (DTT); the second based on differential centrifugations and washes at high pH and high salts concentration [52]. Here, PROS1 is linked to rhabdomyosarcoma.