DBTRG.05MG

High Levels of TGF-α Conferred the Increased Resistance to TMZ in GBM Cells

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor often treated with Temozolomide (TMZ). Yang's team investigated the mechanisms of TMZ resistance in GBM cells, focusing on secretory substances and receptor-activated signaling pathways.

They assessed the correlation between TGF-α expression and TMZ sensitivity in human GBM cell lines. Quantitative analysis of DAPI-stained apoptotic nuclei (Fig. 1A) showed that the TMZ sensitivity, from the lowest to the highest, is DBTRG-05MG, U-87 MG and M059K. There are significant differences between any two of the three cell lines. Western blot showed that the levels of cleaved PARP and caspase-3, the more active the TMZ is, the higher the level, were the lowest in DBTRG-05MG cells, the middle in U-87 MG cells, and the highest in M059K cells (Fig. 1B). qPCR and Western blot demonstrated that the expression of TGF-α was positively correlated with TMZ resistance (Fig. 1C-D).

Yang's team then determined whether neutralizing TGF-α with an anti-human TGF-α antibody could alter TMZ sensitivity. Treatment with TGF-α antibody increased the sensitivity of DBTRG-05MG cells to TMZ (Fig. 1E). Knockdown of TGF-α in DBTRG-05MG cells with shTGF-α lentivirus resulted in a decrease in TGF-α expression (Fig. 1F) and slightly increased TMZ sensitivity (Fig. 1G). LDH release assay showed that silencing TGF-α further enhanced TMZ-induced cytotoxicity in DBTRG-05MG cells (Fig. 1H). Western blot analysis showed that TGF-α-knockdown DBTRG-05MG cells, after TMZ treatment, increased the expression of cleaved caspase-3 and cleaved PARP (Fig. 1). In the reverse experiment, we overexpressed TGF-α in M059K cells, which expressed lower TGF-α and were more sensitive to TMZ. Overexpression of TGF-α increased the TMZ resistance in M059K cells (Fig. 1J and K). They also established a TMZ-resistant DBTRG-05MG subline (DBTRG-05MGR) to investigate the relationship between TGF-α levels and TMZ resistance. DBTRG-05MGR cells were more resistant to TMZ and had higher TGF-α expression and secretion compared to DBTRG-05MG cells (Fig. 1L-N). These results indicate that TGF-α levels are positively related to TMZ resistance in GBM cells.