Investigation of apoptotic and autophagic effects of trabectedin on human glioblastoma cell lines

Glioblastoma is the most common brain tumor in adults. Features of the tumor such as invasiveness, localization, natural resistance against chemo/radiotherapy and blood brain barrier prevent the response to standard treatment options and lead to poor prognosis. Therefore, new treatment options are urgently needed. Today, there are only 4 marine-derived drugs approved for clinical cancer treatment. Probably the most promising one among them, Trabectedin, is currently in use for treatment of ovarian and sarcoma tumors. The aim of this study was to investigate Trabectedin-induced cell death mechanisms in glioblastoma cell cultures. DNA fragmentation, caspase 3/7 activity, TMRE/Hoechst and Annexin V/7-AAD staining, caspase 8/9 inhibitors and expression levels of key proteins in both intrinsic and extrinsic apoptotic pathways were investigated to show apoptosis. To investigate autophagy, MDC staining, LC3-I to II conversion and expression levels of SQSTM1/p62 and Beclin-1 proteins were measured. The role of p53 family proteins in Trabectedin-induced cell death was investigated by using siRNAs and specific inhibitors. The effect of Trabectedin on Bcl-2/Beclin-1 dimerization, which is one of the important crosstalks between apoptosis and autophagy, was measured by using co-immunoprecipitation. Trabectedin induced both intrinsic and extrinsic apoptosis in T98G cell cultures. Moreover, it was found that apoptotic effect of Trabectedin is mediated by p63. On the other hand, in U-87 MG cell line, Trabectedin induced autophagy and this induction was found to be mediated by p53. In conclusion, this preliminary study indicates that Trabectedin might be a good candidate for the treatment of GBM. Further studies are needed to evaluate apoptotic and autophagic effects of Trabectedin on in vivo GBM models.