Inhibitory effect of the adenovirus type 5 E1A protein expressed in the yeast system

Adenovirus 5 type E1A as a tumor suppressor gene can inhibit tumor growth and enhance the sensitivity of chemotherapy and radiotherapy. E1A have the ability to integrate into the host genome, resulting in long-time expres-sion that induces Rb gene inactivation and animal cells im-mortalization. This prompted us to select the E1A protein for treatment of cancer in order to overcome the limitations of E1A gene therapy. Thus, we firstly constructed E1A eu-caryotic expression vector (pPIC9/E1A), transformated the pichia pastoris yeast cells (GS115) and screened the high-expressing recombinant strains. The positive yeast strains were cultured in the shake flask, and induced for 3 d. The crude E1A protein was purified using two steps of col-umn chromatography on HiTrap Q and HiTrap SP. The pu-rified E1A protein was identified by SDS-PAGE and Western blot. E1A protein was mostly located at cellular nuclear when Chariot delivered E1A protein into cells. The analysis in vitro indicated that the E1A protein arrested LN686 cell cycle at G2/M phase, and significantly inhibited the growth of LN686 tumor cells. The current studies firstly provided an experimental basis to further develop E1A protein for tumor treatment.