Heterogeneous response to the growth factors [EGF, PDGF (bb), TGF‐α, bFGF, IL‐2] on glioma spheroid growth, migration and invasion

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Abstract
The effects of 5 different growth factors [EGF, PDGF(bb), TGF-α, bFGF and IL-2] were studied on tumour spheroids obtained from 5 different human glioma cell lines (U-251MG, D-263MG, D-37MG, D-54MG, GaMG). The expression of EGF and PDGF receptors as well as the endogenous production of TGF-α and PDGF Were studied by Northern blot analyses. After growth-factor-exposure, tumour spheroid volume growth, and directional cell migration from the spheroids were studied. In addition, tumour-cell invasion was studied In vitro, where foetal rat-brain aggregates were used as a target for the tumour cells. In all the assays a common stimulator for most of the cell lines was EGF. The other growth factors had a more heterogeneous stimulatory effect. Tumour-cell invasion, cell growth and cell migration are biological properties which are not necessarily related to each other. This may explain why the tumours often responded differently to the growth factors in the various assay systems. Two of the cell lines studied were non-invasive (U-25IMG, D-263MG). It is shown that these were stimulated both in the directional migration assay and in the spheroid-volume-growth assay. However, their non-invasive behaviour was not influenced by the growth factors studied.