Adenoviral-mediated delivery of Pseudomonas exotoxin (PE) fused to IL-13 induces regression of intracranial human glioblastoma xenografts in mice

MARIANELA CANDOLFI; WEIDONG XIONG; MARIANA PUNTEL; AKM GHULAM MUHAMMAD; CHUNYAN LIU; KURT M KROEGER; SONALI MONDKAR; RONALD RODRIGUEZ; PEDRO R LOWENSTEIN; MARIA G CASTRO

Seattle, WA, EEUU

Congreso; American Society of Gene Therapy 10 Annual Meeting; 2007

Human Glioblastomas (GBM) overexpress an IL-13 receptor (IL132R) that is absent in the normal brain. Thus, attempts have been made to target toxic molecules to glioma cells by fusing them with IL-13. However, protein preparations have a short half life, requiring frequent administrations. Thus, we constructed an adenoviral vector (Ad) to transfer a chimeric toxin composed by IL-13 and Pseudomonas exotoxin A (IL13-PE) to preclinical GBMs. We constructed Ad-IL4-TRE-IL13-PE that expresses IL-13-PE, and, as a safety feature, it also expresses a mutated form of IL4 that blocks the physiological receptor, i.e., IL13/IL4R. Transgene expression is driven by the bidirectional TRE promoter, which is activated by the transactivator (TetON, expressed within Ad-TetON), in the presence of the inducer doxycyline (Dox). IL4 ands IL13-PE expression was detected using human U251 glioma cells infected with Ad-IL4-TRE-IL13-PE+Ad-TetON, which reduced cell viability 70% in the “ON” state (+Dox). Human glioma cell viability remained unaffected in the “OFF” state, indicating that the expression of the chimeric toxin can be tightly regulated. Transgene expression from Ad-IL4-TRE-IL13-PE was also detected in COS-7 cells. However, COS-7 cells, which do not express the IL13alpha2R, did not undergo cell death in the presence of the therapeutic virus, suggesting that IL13-PE cytotoxicity is specific to glioma cells. We also administered Ad-IL4-TRE-IL13-PE+Ad-TetON in the striatum of nude mice, which were fed chow containing Dox. IL-4 and IL13-PE toxin were readily detected in the mouse brain, with no signs of toxicity. We then administered Ad-IL4-TRE-IL13-PE+Ad-TetON intratumorally into intracranial human U251 GBM xenografts in nude mice. While saline-treated mice (median survival: 45 days) all the animals treated with Ad-IL4-TRE-IL13-PE survived for over 100 days post-tumor implantation. Our results suggest that Ad-mediated intratumoral expression of IL13-PE toxin will lead to effective cytotoxicity of IL-132R expressing-GBM cells without side effects to the surrounding normal brain and warrant further development of this approach for the implementation of a clinical trial for GBM.