Enhancement of Recombinant Human Tissue Plasminogen Activator Expression in CHO Cells using Matrix Attachment Region Containing Vectors in Combination with Promoter Activation Strategy

Development of high producing mammalian cell lines is a major bottleneck in manufacturing of recombinant therapeutic proteins. This study examines the effect of using the matrix attachment region from the human interferon beta gene in combination with promoter activation strategy with E1A 13S protein on human tissue plasminogen activator (t-PA) expression in Chinese hamster ovary (CHO) cells. The matrix attachment region was cloned in 3΄ and 5΄ flanking sides of the t-PA expression cassette in pTPA vector to generate pMTPA. After transfection of the cells with pTPA and pMTPA vectors، stable cell pools were developed and the t-PA expression level determined for each stable cell line. In the next step، E1A 13S expression plasmid was transfected to stable cell pools and t-PA titers were measured after 72 hours. Integration of pTPA and pMTPA vectors in the CHO genome was confirmed by PCR analysis on genomic DNA of stable cell pools. Analysis of the t-PA expression level showed a three-fold enhancement in pMTPA transfected cells compared to pTPA-containing cells. t-PA expression was further enhanced up to 1771 U/ml by transient expression of E1A 13S in pMTPA stable cell pools. These results have shown that incorporation of matrix attachment region in an expression vector in combination with promoter activation can effectively enhance recombinant protein expression levels in CHO cells.