Abstract
We have investigated the capability of differentiation of Ewing's sarcoma (ES) towards a neuronal direction through the establishment of four extraosseous ES cell lines and by in vitro stimulation with dibutyryladenosine cyclic monophosphate (db-cAMP) of eight ES lines. All except one of the lines expressed the molecule defined by 5C11, the antibody specifically reactive with ES. Two ES lines expressed a 200 kilodalton (kD) neurofilament protein (NFP) although their original tumours were negative for NFP. Elongation of cytoplasmic processes and increased NFP expression were observed after db-cAMP treatment of these lines and microtubules in the cytoplasmic processes were ultrastructurally demonstrated. Six lines were NFP negative, but three lines changed their morphology after induction of 200 kD NFP expression by db-cAMP treatment. The other three showed no definitive differentiation after db-cAMP treatment. Chromosomal analysis of the new ES lines showed the typical t(11;22) in one line and a +der(22) in two lines. No correlation was observed between the chromosomal abnormality and the differentiation capability. We conclude that ES is a heterogeneous group of tumours with respect to capability of differentiation into the neuronal lineage, but it is clearly distinguished from peripheral primitive neuroectodermal tumours by its 5C11 reactivity.