Scanning electron microscopic observations on the interaction between normal neuronal and tumour cells in monolayer...

Interaction of embryonic chick cerebral cells with the astrocytoma (C6) and neuroblastoma (N2a) cells were examined by SEM. When astrocytoma cells were added to the glial monolayer cell substratum the glial substratum was loosened and astrocytoma cells grew into the gaps of the loosened glial substratum. It is believed that the penetrating property of the astrocytoma cells may be related to the invasiveness of the tumour cells. When neuroblastoma (N2a) cells were added to normal glial substratum, no invasion of the glial substratum was observed. Instead, for the first 2 days the tumour cells rested on the glial substratum and sent out numerous fine filopodia (0.1-0.2 micrometers) closely adhered to the surface of the glial cells. On the third day, the groups of glial cells underneath the neuroblastoma cells, which have been covered by filopodia of the tumour cells were rounded and became retracted from the glial substratum. These morphologically altered cells showed features of the tumour cells. It is therefore speculated that neuroblastoma cells have the ability of changing (transforming?) the glial cells probably through their filopodia. When neuroblastoma cells were added to the astrocytoma substratum, there was an initial reaction on both cell types in which lamellipodia were extremely developed. This initial reaction subsided about 24 hours later and the neuroblastoma cells became more flattened, and grew on the astrocytoma substratum. In this case no rounding up of astrocytoma cells was observed. Normal neuronal cells when added to astrocytoma substratum, showed well differentiated neuronal characteristics. This indicates that neuronal differentiation can be maintained by a tumour substratum.