Diagnosis and treatment of cancer

Method of treating cancer in a subject:

• comprising administering an effective amount of an antigen binding protein to the subject,
• wherein the subject has been diagnosed as eligible for treatment with the antigen binding protein targeting a surface antigen expressed on the cancer cells when the measured expression level of Ras associated binding (RAB) protein 5 (RAB5), in the subject's cancer cell sample is decreased as compared to a dichotomizing threshold;
• wherein the expression level of RAB5 in cancer cells in a cell sample obtained from the subject has been measured, wherein said measuring has been performed by an in vitro assay, and the expression level has been compared to the dichotomizing threshold;
• wherein the antigen binding protein is an antigen-binding protein that does not comprise a drug or toxin, wherein the antigen binding protein is an antibody, or an antigen-binding fragment thereof, that binds to the cell surface antigen;
• wherein the surface antigen is a surface antigen internalized by a pathway for endocytosis, wherein said pathway comprises RAB5;
• and
• wherein the surface antigen is selected from the group consisting of human epidermal growth factor receptor (HER)1, HER2, HER3, cluster of differentiation (CD)3, CD19, CD22, CD25 (IL-2Rα), CD30, CD33, CD74, CD79, CEA (CEACAM5 (Carcinoembryonic Antigen Related Cell Adhesion Molecule 5)), FRα (Folate Receptor alpha), epithelial cellular adhesion molecule (EpCAM) (CD326) and Mesothelin (MSLN).