Malignant rhabdoid tumor shows a unique neural differentiation as distinct from neuroblastoma.

Malignant rhabdoid tumors (MRT) show a multiphenotypic diversity, including a neural phenotype. To elucidate the difference in neural characteristics between MRT and neuroblastoma, we examined the expression of synapsin I, neuron-restrictive silencer factor (NRSF), neurofilament medium-size (NF-M) and chromogranin A (CGA) in five MRT cell lines (TM87-16, STM91-01, TTC549, TTC642 and YAM-RTK1) and five neuroblastoma cell lines under differentiation-induction with 12-O-tetradecanoylphorbol-13-acetate (TPA). Our results showed TM87-16 and TTC642 cells, expressed synapsin I and NF-M before TPA induction, had a neural phenotype. After differentiation-induction, only TM87-16 cells expressed CGA. Among all neuroblastoma cells, expression of NF-M and CGA was stable at a high level throughout TPA-induced differentiation. In TM87-16 and TTC642 MRT cells, synapsin I mRNA promptly increased after TPA differentiation, with the peak level at 6 h, and thereafter, synapsin I mRNA rapidly decreased in a time-dependent manner. The decreased expression of synapsin I correlated with an increased expression of NRSF during differentiation-induction. In contrast, in some neuroblastoma cells, a significant up-regulation of synapsin I was observed concurrently with a down-regulation of NRSF. The inverse relationship between NRSF and synapsin I expression in TM87-16 and TTC642 MRT cells was opposite to that of neuroblastoma cells. Our results showed that the neural characteristics of these MRT cells are fairly distinct from those of neuroblastoma cells. These MRT cells appeared to have only limited capability for neural differentiation, and were still in an extremely early stage of neural differentiation.