A method of identifying a subject having cancer who is likely to be responsive to a treatment compound, comprising administering a treatment compound to a subject having cancer； obtaining a sample from the subject； determining the ratio of a first biomarker level to a second biomarker level in the sample from the subject, wherein at least one of the biomarkers is a CRBN-associated protein； and diagnosing the subject as being likely to be responsive to the treatment compound if the ratio of the biomarker levels in the sample of the subject changes as compared to a reference ratio of the biomarker levels.
