[Expression and purification of murine interleukin 18 in Escherichia coli and its antitumor effects]

Total RNA was extracted from murine hepatocytes, and the cDNA of interleukin 18(IL-18) was amplified by RT-PCR. The cDNA was introduced into the expression vector pJW2 and sequenced. Under heat induction, the recombinant murine IL-18(rmIL-18) was expressed in inclusion bodies in E. coli with the yield accounting for 18% of total bacteria proteins. The inclusion bodies were dissolved with 5 mol/L urea, and rmIL-18 was purified using Sephadex G-100 column chromatography. In the presence of 0.5 mg/L Con A, the purified rmIL-18 showed dose-dependent IFN-gamma-inducing activity in murine splenocytes. The purified rmIL-18 exhibited significant antitumor effects in Kunming mice challenged intraperitoneally (i.p.) with H22 hepatocarcinoma when administered 10 micrograms rmIL-18 i.p. on days 1, 4 after challenge, and the mice survived resisted the rechallenged with H22 cells.