Alpha-fetoprotein gene expression in human lymphoblastoid cells and in PHA-stimulated normal T-lymphocytes

Alpha-fetoprotein (AFP) is mainly synthesized by the fetal liver, the yolk sac and, to a much lower extent, by a few non-hepatic fetal tissues (i.e. kidney, pancreas, lung). This property is considered to be lost in mature quiescent cells of the adult. In the present we have studied the expression of AFP mRNA sequences in phytohemagglutinin (PHA)-stimulated normal human T-lymphocytes and in several human lymphoma cell lines. The amount of mRNA transcripts detected in quiescent T-lymphocytes by dot and Northern blot analysis was very low. It increased rapidly after PHA-activation, reached a maximum at 72 hours (six fold the level observed for quiescent T-lymphocytes) and decreased thereafter. The lymphoma cell lines Daudi, Raji, Rh6 et CEM, all expressed elevated levels of AFP mRNA. The transcripts had the size expected for human AFP, suggesting that they were functional and probably translated into protein. The possible role of AFP synthesis in lymphocyte blastogenesis and in lymphoma growth is discussed in relation with the strong binding affinity of this protein for polyunsaturated fatty acids.