Stem Cells, Vol 12, 339-347, Copyright © 1994 by AlphaMed Press
Overexpression and characterization of recombinant human fusion protein IL-6/IL-2 (CH925)
C Zhao, P Tang, J Wang, N Mao, F Jiang, X Li, X Liu, M Zhang, Y Ren and D Du
Department of Experimental Hematology, Institute of Basic Medical Sciences, Beijing, China.
An expression vector encoding the human recombinant fusion protein
interleukin 6/interleukin 2 (IL-6/IL-2) was constructed. When a flexible
linker had been synthesized and ligated with the IL-2 gene fragment by
polymerase chain reaction (PCR) amplification, the IL-6 gene fragment was
unidirectionally inserted into the upstream of the linker-IL-2 sequence.
The molecule of the IL-6-linker-IL-2 fusion gene named E. coli DH5
alpha/pfIL-6/2 was cloned and identified by DNA sequencing. The expressed
protein named as CH925 showed a strong band on SDS-PAGE and amounted to 32%
of total cell protein, and its estimated molecular weight was about 37 kDa.
The fusion protein purified by gel filtration and reversed-phase HPLC
showed as almost homogeneous. CH925 possesses both IL-2 and IL-6 activities
when assayed by CTLL2- and 7TD1-dependent cell lines, respectively. The
specific activity of IL-2 was 2.1 x 10(6) U/mg while that of IL-6 was 2.3 x
10(8) U/mg. Our studies exhibited that CH925 exerted a significant
augmentative effect on the growth of erythroid colony forming units
(CFU-E), and synergized with erythropoietin (EPO) and/or IL-3 in a dose-
dependent way. Our experimental results also showed CH925 at a low dose
causing active lymphokine-activated killer (LAK) cell proliferation more
vigorous than IL-2 and/or IL-6 (p < 0.001). CH925 is a novel fusion
protein, being neither IL-6 nor IL-2, more potent than IL-2 and/or IL-6 and
causing non-IL-2 and non-IL-6 functions of strong EPO- like and mild
IL-3-like effects on erythroid progenitor cell growth. There is a potential
for efficacious clinical application of CH925.
