Objective The aim of this studywas to investigate the mRNA expression levels of human leukocyte antigen Class Ⅰat different progressive stages of human oral squamous cell carcinomas.Methods The expression of mRNA of human leukocyte antigen-B/C was detected in 23 primary tumors, 10 metastatic focuses and 11 histological normal oral epithelia using in situ hybrid- ization method with a digoxigenin-labeled DNA probe. The probe was human leukocyte antigen-B/C locus specific.Results The hybridization signals were present in the cytoplasm of either normal epithelia or tumor cells. The integrated optical density values of the hybridization signalswere detectedwith the aid of an image analysis system. The results showed that the average integrated optical density values of the primary tumors were statistically lower than the normal oral epithelia (P
