Anticancer and bioactivity effect of the AraA-IL13 fusion protein on the glioblastoma cell line.

Background and purpose: Glioblastoma (GBM) is an aggressive and malignant brain cancer with the highest mortality and low survival rates. To discover a more specific and efficient treatment for GBM, we synthesized and examined the cytotoxic effect of arazyme-interleukin-13 (Ara-IL13) fusion protein on GBM cells.

Experimental approach: At first, the araA-IL13 chimeric gene in the pET28a (+) vector was designed and synthesized. After transformation into Escherichia coli BL21 (DE3), the chimeric gene was verified by colony polymerase chain reaction. Expression optimization and purification of the AraA-IL13 fusion protein was performed and subsequently evaluated by 10% SDS-PAGE. The protein was purified and concentrated using the Amicon^® Ultra- 15 centrifugal filter unit. The presence of AraA-IL13 was investigated by the western blotting technique. The enzyme was evaluated for proteolytic activity after purification on skim milk agar. The cytotoxic effect of the AraA-IL13 fusion protein was evaluated by MTT assay on U251 and T98G cell lines in vitro.

Findings/results: The chimeric protein had no proteolytic activity on skim milk agar despite high expression. Furthermore, no cytotoxic effect of this fusion protein (up to 400 μg/mL) was observed on the U251 and T98G cell lines.

Conclusion and implications: The lack of proteolytic activity and cytotoxic effect of AraA-IL13 may be due to the disruption of the three-dimensional structure of the protein or the large structure of the arazyme coupled with the ligand and the lack of proper folding of the arazyme to make the active site of the enzyme inaccessible.