Human Tumor Growth Suppression by Apoptosis Induced with Anti‐ErbB‐2 Chimeric Monoclonal Antibody

Abstract

We established an anti-ErbB-2 mouse-human chimeric monoclonal antibody (MoAb), CH401, which was able to kill cancer cells overexpressing the ErbB-2 protein in vitro. The analysis of the killing mechanism indicated that MoAb CH401 might be the first anti-ErbB-2 mouse-human chimeric MoAb which can induce the apoptosis of cancer cells, since morphological changes and DNA fragmentation were recognized in MoAb CH401-treated cells. The ErbB-2 receptor appears to have two opposing functions: acting as a receptor both for a growth factor and for an apoptotic factor. Our results indicate that MoAb CH401 treatment may prove to be very useful for cancer therapy. Key words:ErbB-2 -Apoptosis -G 1 arrest -Chimeric monoclonal antibody -Growth factor receptorThe human erbB-2 gene product, which encodes a growth factor receptor with intrinsic tyrosine kinase activity, is expressed in a variety of adenocarcinomas.1-5) Many anti-ErbB-2 monoclonal antibodies (MoAbs) have been developed.6-8) ErbB-2 protein has the following advantages as a target molecule: [1] it is a receptor-type molecule expressed on the cancer cell surface; [2] the expression level in normal adult human tissues is very low; [3] the shedding level of this antigen as well as the incidence of positivity for circulating ErbB-2 antigen in gastrointestinal malignant diseases is very low. Accordingly, the blocking effect of circulating antigen on the function of anti-ErbB-2 MoAb should be negligible. 9)Overexpression on cancer cells and extracellular accessibility of the ErbB-2 protein enable it to be a potential target, so anti-ErbB-2 MoAbs seem promising for immunotherapy.Four anti-ErbB-2 mouse MoAbs have been established in our laboratory and characterized.9) The epitopes recognized by these MoAbs are in an extracellular domain within amino acids 292-370 of the human c-erbB-2 molecule. In vitro anti-tumor activity by these MoAbs has been measured and one of them has been selected and chimerized. A mouse-human chimeric MoAb, CH401, for ErbB-2 protein was established by a procedure using a heavy chain loss mouse mutant hybridoma and a human immunoglobulin expression vector, as described elsewhere. 9, 10)Here we show that the anti-tumor activity of this MoAb is due to the induction of apoptosis of cancer cells. MATERIALS AND METHODS MoAbsThe anti-ErbB-2 mouse MoAbs E907 and E401, and the mouse-human chimeric MoAb CH401, each of which recognizes an epitope existing within amino acids 292-370 of the extracellular domain of the human ErbB-2 receptor, 9, 10) were used. These antibodies were of the IgG1 subclass. We developed a mouse-human chimeric form (CH401) of mouse MoAb E401.10) The affinities of mouse MoAb E401 and chimeric MoAb CH401 were similar. The specificity of mouse MoAb E401 and that of chimeric MoAb CH401 have also been confirmed to be the same.10) The epitopes recognized by mouse MoAbs E907 and E401 are different.9, 10) The mouse-human chimeric anti-intercellular adhesion molecule-1 (ICAM-1) MoAb chHA58 of class IgG1 was used as a control.

Monoclonal antibodies as effective therapeutic agents for solid tumors

“…31) Apoptotic changes of tumor cells were also observed in vivo after administration of CH401 (Fig. 3) (unpublished data).…”

“…It is also noteworthy that more than 50% of cells were killed irrespective of the HER2 expression level. 31) We then found that the cytolytic action of CH401 was based on programmed cell death. Morphological changes and DNA fragmentation were recognized at least 12 h after treatment of Fig.…”

“…2). 31) In these experiments, cells were incubated with CH401 for 48 h and viable cells were simply determined by trypan blue staining, suggesting that the in vivo anti-tumor effect was at least partly due to CH401 alone. It is also noteworthy that more than 50% of cells were killed irrespective of the HER2 expression level.…”

Prevention of gastrointestinal tumors based on adenomatous polyposis coli gene mutation by dendritic cell vaccine

“…Since the antibody reacted with intact tumor T cells, the target antigen is apparently on the surface, allowing the circulating antibody to react with the antigen. A cytotoxic mAb that binds to ErbB-2, a member of the EGFR family, and induced apoptosis has been reported (41). The antibody produced in the mice inoculated with DC/Ts might be directed against growth factor receptor-related molecules.…”

Enhanced Anti‐tumor Effect of Trastuzumab in Combination with Cisplatin

“…[8][9][10] The anti-HER-2/neu humanized antibody Trastuzumab recognizes a carbohydrate epitope on the extracellular domain of HER-2/ neu and anti-HER-2/neu antibody suppresses in vitro proliferation of several human solid tumor cell lines. [11][12][13] Anti-HER-2/neu antibody action is partially mediated by an antagonistic effect on signal transduction 11,14) and partially by an anti-tumor effect via antibody-dependent (effector) cell-mediated cytotoxicity (ADCC). 15,16) Therefore, it can be speculated that the anti-HER-2/neu antibody Trastuzumab also exerts its antitumor effect through these mechanisms.…”