A 5? Sequence of Human HMGB2 Gene for Transcriptional Targeting of Glioblastoma

Achievement of specific tumor cell targeting remains a challenge for glioma gene therapy. We report here the identification and characterization of a 5’ sequence of human HMGB2 gene for transcriptional targeting to glioblastoma. We performed microarray analysis and found HMGB2 as one of the genes that had a low level of expression in normal human astrocytes, but was significantly up-regulated in glioblastoma cells. Real-time PCR quantification revealed increase in HMBG2 expression level in glioblastoma tissues and cells between 11 to 79 fold over that in normal human brain tissue. With progressive truncation of a 5’-upstream sequence of the HMGB2 gene, we identified a 500-bp fragment that displayed a high transcriptional activity in glioblastoma cells, but a low activity in normal brain cells. Using the sequence to drive the expression of the herpes simplex virus thymidine kinase gene in the context of a baculoviral vector, glioblastoma cells died in the presence of ganciclovir, whereas normal human astrocytes and neurons were not affected. We further confirmed that after intra-tumor injection, the baculoviral vector effectively suppressed the growth of human glioblastoma cells in a mouse xenograft model. Our results suggest that the 5’-upstream sequence of the HMGB2 gene can be used as an efficient, tumor-selective promoter in targeted vectors for glioblastoma gene therapy. U251 cells (n=3) genes level expression were compared to that of normal astrocytes (n=3) to find overexpressed genes in glioblastoma. Highly expressed genes were compared to those found in the litterature. This was selected to clone promoters of highly expressed genes in glioblastomas