gms | German Medical Science

Objective: The transcription factor Twist-1 and the interacting protein Akirin-2 are supposed to have a modulatory function in apoptotic pathways of tumors. We hypothesize that their deregulation in human gliomas might be one possible reason for the resistance of these tumors to chemotherapeutic drugs.

Method: We examined the expression of Akirin-2 and Twist-1 in solid/cultured human glioblastomas by qPCR, Western Blot and double-immunofluorescence stainings. We analyzed the temozolomide-induced regulation of both proteins by qPCR and immunocytochemistry. After generating siRNA knock-down variants, we determined altered cCaspase 3/7 activity, and cleavage of Caspase 3, 7 and PARP by Western Blot and double-immunofluorescence stainings including the ImageStream Mark II technology.

Results: Both molecules were clearly detectable in solid and cultured human glioblastomas on mRNA and protein levels. They were expressed in GFAP-positive tumor regions as well as in tumor endothelial cells and infiltrating macrophages / microglia. Expression of both molecules was highly induced after temozolomide treatment, sometimes combined with a shift of nuclear to cytosolic localization. After siRNA knock-down of Akirin-2 (with/without temozolomide treatment), higher activity of cCaspase 3/7 was observed, and higher amounts of cleaved Caspases 3, 7 and PARP were found. Immunofluorescence and ImageStream Mark II technology identified siAkirin-2 treated cells as main sources. For Twist-1 similar results were obtained with the exception that the combination of temozolomide treatment and siTwist-1 knockdown resulted in different Twist-1 cell populations with individual apoptotic responses.

Conclusions: Our results provide a basic insight into the Twist-1 and Akirin-2-mediated chemotherapeutic resistance of human gliomas.