Antitumor activity and toxicity of anti-HER2 immunoRNase scFv 4D5-dibarnase in mice bearing human breast cancer xenografts

Abstract

Ribonucleases (RNases) are a non-mutagenic alternative to harmful DNA-damaging anticancer drugs. Targeting of RNases with antibodies to surface antigens that are selectively expressed on tumor cells endows specificity to the cytotoxic actions of RNases. Barnase, a ribonuclease from Bacillus amyloliquefaciens, is a promising candidate for targeted delivery to cancer cells because of its insusceptibility to the ubiquitous cytoplasmic ribonuclease inhibitor, and its high stability and catalytic activity. Here, we characterized in vitro and in vivo an immunoRNase, scFv 4D5-dibarnase, which consists of two barnase molecules that are fused serially to the single-chain variable fragment (scFv) of humanized 4D5 antibody. The latter is directed against the extracellular domain of human epidermal growth factor receptor 2 (HER2), a cancer marker that is overexpressed in many human carcinomas. The scFv 4D5-dibarnase exerted a specific cytotoxic effect on HER2-overexpressing SKBR-3 and BT-474 human breast carcinoma cells (IC(50) = 4.1 and 2.4 nM, respectively) via induction of apoptosis. Ten doses of 0.7 mg/kg scFv 4D5-dibarnase to BALB/c nude mice that bore SKBR-3 human breast cancer xenografts resulted in a 76% reduction in tumor growth. A single injection of scFv 4D5-dibarnase at a total course dose of 7 mg/kg did not cause severe side effects in BALB/c nude or BDF1 mice. The cytotoxicity and selectivity of scFv 4D5-dibarnase merit consideration of this immunoRNase as a potent anticancer agent.

Improved biological activity of a single chain antibody fragment against human epidermal growth factor receptor 2 (HER2) expressed in the periplasm of Escherichia coli

“…As a result, anti-HER2his-scFv was specifically cytotoxic to SK-OV-3 cells, but not to MDA-MB-468 cells. Similar results were reported for the cytotoxicity of the scFv 4D5-dibarnase, which was selectively cytotoxic to HER2-overexpressing BT-474 cells but did not markedly affect the viability of the low-HER2-expressing MCF7 cells [48]. One of the proposed mechanisms for HER2-directed therapy is downregulation of HER2-signaling pathways to result in apoptosis.…”

RNase MC2: a new Momordica charantia ribonuclease that induces apoptosis in breast cancer cells associated with activation of MAPKs and induction of caspase pathways

“…Engineered onconase, a linkage with an anti-Trop-2 antibody, exhibited potent cytotoxicity against diverse epithelial cancer cells, including breast tumor cells [30]. scFv 4D5-dibarnase, an engineered barnase product, manifested good selective toxicity to human breast cancer cells in vitro and in vivo, but no detailed molecular mechanism was revealed [31]. For RNase MC2, the differential activation of MAPKs and induction of both extrinsic and intrinsic caspase pathways contributed to its apoptosis-inducing activity (Figs 5, 6).…”

Genetically Encoded Immunophotosensitizer 4D5scFv-miniSOG is a Highly Selective Agent for Targeted Photokilling of Tumor Cells in Vitro

“…In general, HER2/neu, overexpressed on the surface of many cancer cells, is an important target for cancer therapy 10, 11. The first to demonstrate this in animals were Drebin and co-workers 12, who proved that monoclonal antibody specific to the extracellular domain of HER2/neu protein possesses a significant anti-tumor effect.…”