Determination of type I transglutaminase in differentiating normal and neoplastic human keratinocytes by an in situ radioimmunoassay.

The presence of type I transglutaminase was determined in the neoplastic human keratinocyte line SqCC/Y1 and in normal human epidermal keratinocytes (NHEK) by an in situ radioimmunoassay which corresponded directly with the measurement of type I transglutaminase enzymatic activity. Dexamethasone induced differentiation of SqCC/Y1 cells caused a marked increase in transglutaminase immunoreactivity and enzymatic activity over non-steroid treated cells in a concentration-related and a time-related fashion. Retinoic acid suppressed the dexamethasone induced increase in type I transglutaminase immunoreactivity in differentiating SqCC/Y1 cells. The type I transglutaminase radioimmunoassay should be useful in studies focusing on the regulation of transglutaminase activity in normal and neoplastic keratinocytes, and for rapidly screening agents for their effects on squamous cell differentiation.