Expression of the humanized anti-HER2/neu monoclonal antibody trastuzumab in transgenic tobacco plants

BBreast cancer is the most common cancer among women, annually more than half a million women were diagnosed with breast cancer. Trastuzumab (Herceptin®) is a recombinant DNA-derived humanized monoclonal antibody used in the treatment of metastatic breast cancer. A course of treatment, however, is very expensive and a full one-year course of treatment for a single patient costs more than 2000,000,000 IRR. In this study, the feasibility of trastuzumab production in tobacco plants (N. tabacum) using A. tumefaciens-mediated stable transformation was investigated. Leaf explants of tobacco cv. Gewone groene were inoculated with Agrobacterium tumefaciens harbouring the binary vectors pBIN19-NTopTras-LC and pBIN19-NTopTras-HC containing the genes encoding heavy and light chains (HC and LC respectively) of trastuzumab. Southern blot analysis demonstrated the integration of 1-3 copies of the transgenes into the tobacco genome. The expression of transgenes at RNA transcription level was revealed by semi-quantitative RT-PCR. Protein accumulation in plants was detected by western blot analysis and antibody content were ca. 0.1% of total soluble protein in transgenic plants. Immunoblot analysis of crude plant extracts revealed that trastuzumab accumulates within plants, mostly in the fully assembled tetrameric)H2L2 (form. T1 progeny analysis confirmed stable inheritance and co-segregation of the introduced transgenes as a single dominant Mendelian locus. The results of the present study indicate that plants can be used as an alternative platform for the cost-effective production of high value pharmaceutical proteins. This study for the first time represented the first crucial step towards the development of a plant-derived trastuzumab in our country.