Novel functional anti-HER3 monoclonal antibodies with potent anti-cancer effects on various human epithelial cancers

Resistance of progressive cancers against chemotherapy is a serious clinical problem. In this context, human epidermal growth factor receptor 3 (HER3) can play important roles in drug resistance to HER1- and HER2- targeted therapies. Since clinical testing of anti-HER3 monoclonal antibodies (mAbs) such as patritumab could not show remarkable effect compared with existing drugs, we generated novel mAbs against anti-HER3. Novel rat mAbs reacted with HEK293 cells expressing HER3, but not with cells expressing HER1, HER2 or HER4. Specificity of mAbs was substantiated by the loss of mAb binding with knockdown by siRNA and knockout of CRISPR/Cas9-based genome-editing. Analyses of CDR sequence and germline segment have revealed that seven mAbs are classified to four groups, and the binding of patritumab was inhibited by one of seven mAbs. Seven mAbs have shown reactivity with various human epithelial cancer cells, strong internalization activity of cell-surface HER3, and inhibition of NRG1 binding, NRG1-dependent HER3 phosphorylation and cell growth. Anti-HER3 mAbs were also reactive with in vivo tumor tissues and cancer tissue-originated spheroid. Ab4 inhibited in vivo tumor growth of human colon cancer cells in nude mice. Present mAbs may be superior to existing anti-HER3 mAbs and support existing anti-cancer therapeutic mAbs

Anti-Tumor Effect against Human Cancer Xenografts by a Fully Human Monoclonal Antibody to a Variant 8-Epitope of CD44R1 Expressed on Cancer Stem Cells

BACKGROUND: CD44 is a major cellular receptor for hyaluronic acids. The stem structure of CD44 encoded by ten normal exons can be enlarged by ten variant exons (v1-v10) by alternative splicing. We have succeeded in preparing MV5 fully human IgM and its class-switched GV5 IgG monoclonal antibody (mAb) recognizing the extracellular domain of a CD44R1 isoform that contains the inserted region coded by variant (v8, v9 and v10) exons and is expressed on the surface of various human epithelial cancer cells. METHODS AND PRINCIPAL FINDINGS: We demonstrated the growth inhibition of human cancer xenografts by a GV5 IgG mAb reshaped from an MV5 IgM. The epitope recognized by MV5 and GV5 was identified to a v8-coding region by the analysis of mAb binding to various recombinant CD44 proteins by enzyme-linked immunosorbent assay. GV5 showed preferential reactivity against various malignant human cells versus normal human cells assessed by flow cytometry and immunohistological analysis. When ME180 human uterine cervix carcinoma cells were subcutaneously inoculated to athymic mice with GV5, significant inhibition of tumor formation was observed. Furthermore, intraperitoneal injections of GV5markedly inhibited the growth of visible established tumors from HSC-3 human larynx carcinoma cells that had been subcutaneously transplanted one week before the first treatment with GV5. From in vitro experiments, antibody-dependent cellular cytotoxicity and internalization of CD44R1 seemed to be possible mechanisms for in vivo anti-tumor activity by GV5. CONCLUSIONS: CD44R1 is an excellent molecular target for mAb therapy of cancer, possibly superior to molecules targeted by existing therapeutic mAb, such as Trastuzumab and Cetuximab recognizing human epidermal growth factor receptor family

Imaging the L-type amino acid transporter-1 (LAT1) with Zr-89 immunoPET.

The L-type amino acid transporter-1 (LAT1, SLC7A5) is upregulated in a wide range of human cancers, positively correlated with the biological aggressiveness of tumors, and a promising target for both imaging and therapy. Radiolabeled amino acids such as O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) that are transport substrates for system L amino acid transporters including LAT1 have met limited success for oncologic imaging outside of the brain, and thus new strategies are needed for imaging LAT1 in systemic cancers. Here, we describe the development and biological evaluation of a novel zirconium-89 labeled antibody, [(89)Zr]DFO-Ab2, targeting the extracellular domain of LAT1 in a preclinical model of colorectal cancer. This tracer demonstrated specificity for LAT1 in vitro and in vivo with excellent tumor imaging properties in mice with xenograft tumors. PET imaging studies showed high tumor uptake, with optimal tumor-to-non target contrast achieved at 7 days post administration. Biodistribution studies demonstrated tumor uptake of 10.5 ± 1.8 percent injected dose per gram (%ID/g) at 7 days with a tumor to muscle ratio of 13 to 1. In contrast, the peak tumor uptake of the radiolabeled amino acid [(18)F]FET was 4.4 ± 0.5 %ID/g at 30 min after injection with a tumor to muscle ratio of 1.4 to 1. Blocking studies with unlabeled anti-LAT1 antibody demonstrated a 55% reduction of [(89)Zr]DFO-Ab2 accumulation in the tumor at 7 days. These results are the first report of direct PET imaging of LAT1 and demonstrate the potential of immunoPET agents for imaging specific amino acid transporters

Dual‐targeting therapy against HER3/MET in human colorectal cancers

Abstract Background Colorectal cancer (CRC) is the most common malignancy in the world, and novel molecular targeted therapies for CRC have been vigorously pursued. We searched for novel combination therapies based on the expression patterns of membrane proteins in CRC cell lines. Results A positive correlation was observed between the expression of human pidermal growth factor receptor (HER) 3 and mesenchymal‐to‐epithelial transition factor (MET) on the cell surface of CRC cell lines. The brief stimulation of HER3/MET‐high SW1116 CRC cells with both neuregulin‐1 (NRG1) and hepatocyte growth factor enhanced ERK phosphorylation and cell proliferation more than each stimulation alone. In addition, a prolonged NRG1 stimulation resulted in the tyrosine phosphorylation of MET. In this context, the Forkhead Box protein M1 (FOXM1)‐regulated tyrosine phosphorylation of MET by NRG1 was demonstrated, suggesting the existence of a signaling pathway mediated by FOXM1 upon the NRG1 stimulation. Since the co‐expression of HER3 and MET was also demonstrated in in vivo CRC tissues by immunohistochemistry, we investigated whether the co‐inhibition of HER3 and MET could be an effective therapy for CRC. We established HER3‐and/or MET‐KO SW1116 cell lines, and HER3/MET‐double KO resulted in the inhibition of in vitro cell proliferation and in vivo tumor growth in nude mice by SW1116 cells. Furthermore, the combination of patritumab, an anti‐HER3 fully human mAb, and PHA665752, a MET inhibitor, markedly inhibited in vitro cell proliferation, 3D‐colony formation, and in vivo tumor growth in nude mice by SW1116 cells Conclusion The dual targeting of HER3/MET has potential as CRC therapy

An illustration of the transmembrane L-type amino acid transporter-1 (LAT1) which forms a functional heterodimer with the 4Fhc heavy chain glycoprotein and is responsible for the transport of amino acids with large neutral side chains through an exchange mechanism.

<p>An illustration of the transmembrane L-type amino acid transporter-1 (LAT1) which forms a functional heterodimer with the 4Fhc heavy chain glycoprotein and is responsible for the transport of amino acids with large neutral side chains through an exchange mechanism.</p

<i>In</i><i>vitro</i> experiments in LAT-1 expressing HCT-116 cell line.

<p>(<b>A</b>) Receptor saturation using varying concentrations of the radiolabeled antibody, [⁸⁹Zr]DFO-Ab2. (<b>B</b>) Immunoreactivity assay plot of the (total/bound) activity <i>versus</i> (1/[normalized cell concentration]) of [⁸⁹Zr]DFO-Ab2, immunoreactive fraction determined by extrapolation to infinite antigen excess (1/y-intercept). (C) Surface bound and internalized cellular accumulation of the radioimmunoconjugate over time (up to 24 h). </p

Tumor-to-organ ratios of the immunoPET tracer, [⁸⁹Zr]DFO-Ab2 without (blue) and with blocking doses (green) of unlabeled Ab2 at 7 days post injection with comparison to the ¹⁸F-labeled amino acid, [¹⁸F]FET, at 30 minutes after intravenous administration.

<p>Tumor-to-organ ratios of the immunoPET tracer, [⁸⁹Zr]DFO-Ab2 without (blue) and with blocking doses (green) of unlabeled Ab2 at 7 days post injection with comparison to the ¹⁸F-labeled amino acid, [¹⁸F]FET, at 30 minutes after intravenous administration.</p