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Potent killing of HBV-related hepatocellular carcinoma by a chimeric protein of anti-HBsAg single-chain antibody and truncated Bid

Yan, Bo, Ouyang, Qing, Zhao, Zhining, Cao, Feng, Wang, Tao, Jia, Xiaofei, Meng, Yanling, Jiang, Shuai, Liu, Jiayun, Chen, Rui, Jia, Lintao, Zhang, Rui, Wen, Weihong, Jin, Boquan, Chen, Siyi, Zhao, Jing, Yang, Angang
Biomaterials 2013 v.34 no.20 pp. 4880-4889
Hepatitis B virus, antibodies, anticarcinogenic activity, apoptosis, chimerism, growth retardation, hemagglutinins, hepatitis B antigens, hepatoma, humans, image analysis, influenza, inhibitory concentration 50, surface antigens, therapeutics
Targeted therapy is needed for hepatitis B virus (HBV)-mediated hepatocellular carcinoma (HCC) which shows overexpression of HBV surface antigen (HBsAg). We previously developed scFv15, a human single-chain antibody against HBsAg. Here we tested the strategic feasibility of scFv15-mediated delivery of apoptotic effectors for HBsAg-targeted HCC therapy and application of HA2 motif of influenza hemagglutinin to enhance endosome escape and antitumor effect. A class of HBsAg-targeted immunoproapoptotic molecule was generated by sequentially fusing scFv15, the furin-cleavable motif from diphtheria toxin (Fdt), HA2 and a truncated apoptotic protein Bid (tBid). The resulting scFv15-Fdt-HA2-tBid was prokaryotically expressed and functionally characterized for HBsAg-binding capacity, endosome escape activity and antitumor effect as compared with scFv15-Fdt-tBid. Both scFv15-Fdt-HA2-tBid and scFv15-Fdt-tBid retained affinity and specificity for HBsAg, and bound and selectively killed HBsAg-positive HCC cells via apoptosis. Notably, the IC₅₀ of scFv15-Fdt-HA2-tBid in HBsAg-positive PLC/PRF/5 cells was 10 times lower than that of scFv15-Fdt-tBid. In vivo imaging of antitumor activity demonstrated 95% growth inhibition of orthotopic HCC by scFv15-Fdt-HA2-tBid compared with 75% suppression by scFv15-Fdt-tBid. This study represents an extended application of the immunoproapoptotic strategy in the treatment of HBsAg-positive HCC and shows significant potential of HA2 as a functional enhancer for endosome-encapsulated antibody-conjugates.