Glioblastoma multiforme cells communicate with each other through extracellular vesicles during temozolomide treatment

Glioblastoma multiforme (GBM) is a major challenge in oncology due to its aggressive nature and limited treatment options. This is exacerbated by emerging resistance mechanisms to conventional therapies such as temozolomide (TMZ). The critical role of GBM cell-derived extracellular vesicles (EVs) in shaping the tumor microenvironment and influencing treatment response has been highlighted in recent publications. In this study, we investigated whether and to what extent EVs derived from GBM in response to TMZ treatment may influence each other. The proteomic analysis of EVs isolated from different GBM cell lines, revealed that TMZ treatment induced a significant increase of specific proteins in U373MG and U87MG, those involved in cell motility, migration, invasiveness, and cell death. Thus, we tested the influence of isolated EVs in the presence and absence of TMZ in promoting or reducing the rate of migration and induction of cell death. Indeed, when GBM cells were incubated with EVs isolated from TMZ-treated GBM cells the migratory rate was unchanged, while changes in cell death markers were detected by Western blot analysis. Surprisingly, when EVs from GBM cells, i.e. U87MG, less responsive to TMZ treatment, were co-incubated with U251MG, more responsive to TMZ treatment, a decrease of the sensitivity in terms of cell death induction and migratory rate was observed. Therefore, this work puts a new piece of knowledge on the mechanisms orchestrating pro-survival or pro-death signalling cascades initiated by EV cargo, highlighting a more complex crosstalk in the tumor microenvironment.