Temozolomide‐modulated glioma proteome: Role of interleukin‐1 receptor‐associated kinase‐4 ( IRAK 4) in chemosensitivity

The current treatment for glioblastoma includes temozolomide ( TMZ ) chemotherapy, yet the mechanism of action of TMZ is not thoroughly understood. Here, we investigated the TMZ ‐induced changes in the proteome of the glioma‐derived cell line ( U 251) by 2 D DIGE . We found 95 protein spots to be significantly altered in their expression after TMZ treatment. MS identified four upregulated spots: aspartyl t RNA synthetase glutathione synthetase, interleukin‐1 receptor‐associated kinase‐4 ( IRAK 4), and breast carcinoma amplified sequence‐1 and one downregulated spot: optineurin. TMZ ‐induced regulation of these five genes was validated by RT ‐q PCR and W estern blot analysis. RNA i‐mediated knockdown of IRAK 4, an important mediator of T oll‐like receptors signaling and chemoresistance, rendered the glioma cells resistant to TMZ . High levels of IRAK 4 induced upon TMZ treatment resulted in IRAK 1 downregulation and inhibition of NF k B pathway. Endogenous IRAK 4 protein, but not transcript levels in glioma cell lines, correlated with TMZ sensitivity. Thus, we have identified several TMZ ‐modulated proteins and discovered an important novel role for IRAK 4 in determining TMZ sensitivity of glioma cells through its ability to inhibit T oll‐like receptor signaling and NF k B pathway.