NGF and glioblastoma: The tumor-promoting effect of DHEA may be caused by activation of non-genomic pro-survival signal transduction.39 DHEA increases the secretion of BDNF and NGF, both of which promotes proliferation of astrocytes.49 DHEA activates both PI3K/Akt and Src/Erk1/2 pathways that are highly activated in cancer development.39, 50, 51 In our study, DHEA induces TMZ resistance in GBM.