Tumour-related expression of a translation-elongation factor-like protein.

We have identified a tumour-related 43 kd cytoplasmic protein (LC/p43) using a monoclonal antibody against the total proteins of human hepatoma cell line PLC/PRF/5. LC/p43 is preferentially expressed in a variety of tumours of human and animal origin, whereas no expression was detected in several normal adult tissues tested. LC/p43 expression was induced in rodent fibroblasts upon transfection with several viral oncogenes. Expression in non-transformed peripheral blood lymphocytes could be induced by treatment with phytohaemagglutinin (PHA) and subsequent culture with interleukin II, whereas retinoic acid treatment of transformed cells caused a drastic reduction of the antigen in the cells. Sequence analysis of three tryptic peptides of LC/p43 revealed 50-70% homology to different domains of the eukaryotic and prokaryotic translation-elongation factors EF1-alpha and EF-Tu, respectively.