Disclosed herein is a method of treating nuclear protein in testis (NUT) midline carcinoma (NMC) in a subject in need thereof, comprising administering an effective amount of a bromodomain inhibitor, wherein the effective amount can be determined according to the expression levels of CD11b, which monitors responsiveness of the NMC to the bromodomain inhibitor. Also disclosed herein is a method of determining a bromodomain inhibitor treatment regimen in a subject suffering from NMC.