Ribonuclease Onconase Anti-cancer Research

Cancer, one of the most deadly diseases, is threatening the life of human being. However, we still have no effective way to deal with cancer. Most anticancer drugs now in practice are not satisfied for either serious side-effects or immunogenic conflictions. To find the new specific anticancer agents attracts many scientists.Ribonuclease as an RNA enzyme existing in mammalian cells has the effect of antitumor in vitro and in vivo. It has the advantages of smaller molecular weight and weaker immunogen comparing with traditional drugs. Among the ribonucleases, Onconase which is abundant in oocytes of frog (Rana pipiens) has the most promising potential on serial of tumor cells. Our research is focus on the specificity of Onconase.We synthesized the Onconase gene according with the E.coli coda bias. The gene was cloned into expression vector pET-22b(+) via MscI and Sail. In host BL21 (DE3), the recombined Onconase was expressed in inclusion body, which can be collected and purified easily. We provided an oxidized and reduced condition in which the inclusion body can be refolded correctly. At last, we obtained the recombined Onconase with the similar activity and IC50 on K562 and Hut-78 cell lines as the natural one. To increase the specificity of Onconase, transferrin was conjugated with Onconase using SPDP reagent. Onconase-Tf complex increase IC50 100 times on K562 cells which express transferrin receptor richly. Our results suggested that Onconase could increase its specificity via conjugating with ligands. Our studies also give the way to develop the new antitumor drugs.