Provided herein are methods for treating cancer in a patient who has been determined to have positive expression of CD200 receptor (CD200R1) and one or more biomarkers (i.e., ICOS, TIGIT, TNFRSF9, HAVCR2, PDCD1, FCGR2A, FCGR1A, CD163, and/or CD14) by administering to the patient a CD200 inhibitor. Also provided are methods for monitoring responsiveness of a patient having cancer to treatment with a CD200 inhibitor, the method comprising: determining expression levels of CD200R1 and one or more biomarkers (i.e., ICOS, TIGIT, TNFRSF9, HAVCR2, PDCD1, FCGR2A, FCGR1A, CD163, and/or CD14) in a biological sample from the patient, wherein increased expression levels of CD200R1 and the one or more biomarkers, as compared to expression levels in a biological sample of the same type obtained from the subject prior to treatment with the CD200 inhibitor, indicates that the subject is responsive to treatment with the CD200 inhibitor.
