Density-dependent inhibition of 2-deoxy-d-glucose uptake into glioma and neuroblastoma cells in culture

The transport of 2-deoxy-d-glucose (2-DG) into cultured human glioma (138 MG) and mouse neuroblastoma (C1300) cells has been studied in relation to the growth curves of the cells. An initial increase in the uptake of 2-DG into exponentially growing 138 MG cells, could be attributed to the number of days the cells were kept in culture rather than to their increased density. As the 138 MG cells reached confluency after 3 days the 2-DG uptake became density-dependent inhibited. In still denser cultures the cell growth was inhibited. This was accompanied by morphological ‘normalization’ of the cells and increased uptake of 2-DG. Uptake of 2-DG into C1300 cells was density-dependent inhibited throughout the cell growth cycle. As the cell density increased from 15 × 10³ to 130× 10³ cells/cm² the rate of uptake/cell decreased to one-fourth. At the latter cell density the cells entered stationary phase, without any major changes in morphology. The results suggest that spontaneously occurring tumour cells, such as glioma and neuroblastoma cells, can regulate the sugar transport in relation to cell density. This could be due to newly-acquired differentiated properties of the cells or to true contact-inhibitory phenomena.