HumanC-ERBB-2 proto-oncogene product as a target for bispecific-antibody-directed adoptive tumor immunotherapy

CD98 regulates the phosphorylation of HER2 and a bispecific anti-HER2/CD98 antibody inhibits the growth signal of human breast cancer cells

Human epidermal growth factor receptor (HER) family proteins are currently major targets of therapeutic monoclonal antibodies against various epithelial cancers. However, the resistance of cancer cells to HER family-targeted therapies, which may be caused by cancer heterogeneity and persistent HER phosphorylation, often reduces overall therapeutic effects. We herein showed that a newly discovered molecular complex between CD98 and HER2 affected HER function and cancer cell growth. The immunoprecipitation of the HER2 or HER3 protein from lysates of SKBR3 breast cancer (BrCa) cells revealed the HER2-CD98 or HER3-CD98 complex. The knockdown of CD98 by small interfering RNAs inhibited the phosphorylation of HER2 in SKBR3 cells. A bispecific antibody (BsAb) that recognized the HER2 and CD98 proteins was constructed from a humanized anti-HER2 (SER4) IgG and an anti-CD98 (HBJ127) single chain variable fragment, and this BsAb significantly inhibited the cell growth of SKBR3 cells. Prior to the inhibition of AKT phosphorylation, BsAb inhibited the phosphorylation of HER2, however, significant inhibition of HER2 phosphorylation was not observed in anti-HER2 pertuzumab, trastuzumab, SER4 or anti-CD98 HBJ127 in SKBR3 cells. The dual targeting of HER2 and CD98 has potential as a new therapeutic strategy for BrCa.

Altered binding avidities and improved growth inhibitory effects of novel anti-HER3 mAb against human cancers in the presence of HER1-or HER2-targeted drugs

HER1-and HER2-targeted drugs are effective in cancer therapy, especially against lung, breast and colon malignancies; however, resistance of cancer cells to HER1-and HER2-targeted therapies is becoming a serious problem. The avidity/affinity constant (K_A) and growth inhibitory effect of anti-HER3 rat monoclonal antibodies (mAb, Ab1∼Ab6) in the presence of therapeutic mAb or low-molecular-weight inhibitors against HER family proteins were analyzed by flow cytometry-based Scatchard plots (Splot) and cell proliferation assay. The K_A of Ab3 and Ab6, but not Ab1 or Ab4, split into dual (high and low) modes of K_A, and Ab6 exhibited greater anti-proliferative effects against LS-174T colon cancer cells in the presence of Pertuzumab (anti-HER2 mAb). A high K_A by Ab6 and Ab6-mediated increased growth inhibition were observed against NCI-H1838 lung or BT474 breast cancer cells, respectively, in the presence of Panitumumab (anti-HER1 mAb) or Perutuzumab. A high K_A by Ab6 and Ab6-mediated increased anti-proliferative effects against NCI-H1838 or BT474 were also respectively observed in the presence of Erlotinib (HER1 inhibitor) or Lapatinib (HER1/HER2 inhibitor). In HER1-knockout (KO) NCI-H1838, the reactivity and K_A of Ab4 increased compared with in parent NCI-H1838. In HER1-KO or HER3-KO SW1116 colon cancer cells, dual modes of K_A with Pertuzumab were noted, and the combination Ab6 and Pertuzumab promoted growth inhibition of HER1-KO, but not of parent SW1116.

[Analysis of Target Molecules towards Anti-cancer Therapeutic Antibodies]

Target molecules of existing anti-cancer therapeutic monoclonal antibodies (mAbs) are divided into 1) receptor-type tyrosine kinases, such as human epidermal growth factor receptor (HER) family, 2) differentiation antigens, such as CD20 (Rituxan target), 3) angiogenesis-related molecules, and 4) immune checkpoint molecules (PD-1, etc.). We have recently reported a novel therapy targeting lymphangiogenesis, but not angiogenesis, using an anti-LYVE-1 (lymphatic vessel endothelial hyaluronan receptor 1) mAb. At present, many transporters are not considered to be target molecules for the cancer therapy; however, our study strongly suggested that the inhibition of cancer metabolism by mAbs against amino acid transporters will play a significant role in future cancer therapies. Most anti-cancer therapeutic mAbs bind cell-surface molecules on viable cancer cells: therefore, it is necessary to produce mAbs recognizing epitopes on the extracellular domains of native and non-denatured proteins. We concluded that viable cancer cells or cells transfected with cDNA encoding target proteins are suitable immunogens for the production of anti-cancer therapeutic mAbs. We introduce our efforts to develop seeds for therapeutic mAbs using whole cancer cells and transfectants as the immunogen. As many target candidates in the future are multi-pass membrane proteins, such as 12-pass amino acid transporter proteins belonging to the solute carrier (SLC) family, and their possible immunogenic extracellular regions are small, the production of specific mAbs is highly difficult. In this review, we summarize the successful preparation and characterization of mAbs recognizing the extracellular domain of oncoproteins, including transporters.

Anti-tumor effects of mAb against L-type amino acid transporter 1 (LAT1) bound to human and monkey LAT1 with dual avidity modes

l‐Type amino acid transporter 1 (LAT1) disulfide linked to CD98 heavy chain (hc) is highly expressed in most cancer cells, but weakly expressed in normal cells. In the present study, we developed novel anti‐LAT1 mAbs and showed internalization activity, inhibitory effects of amino acid uptake and cell growth and antibody‐dependent cellular cytotoxicity, as well as in vivo antitumor effects in athymic mice. Furthermore, we examined the reactivity of mAbs with LAT1 of Macaca fascicularis to evaluate possible side‐effects of antihuman LAT1 mAbs in clinical trials. Antihuman LAT1 mAbs reacted with ACHN human and MK.P3 macaca kidney‐derived cells, and this reactivity was significantly decreased by siRNAs against LAT1. Macaca LAT1 cDNA was cloned from MK.P3, and only two amino acid differences between human and macaca LAT1 were seen. RH7777 rat hepatoma and HEK293 human embryonic kidney cells expressing macaca LAT1 were established as stable transfectants, and antihuman LAT1 mAbs were equivalently reactive against transfectants expressing human or macaca LAT1. Dual (high and low) avidity modes were detected in transfectants expressing macaca LAT1, MK.P3, ACHN and HCT116 human colon cancer cells, and K_A values were increased by anti‐CD98hc mAb, suggesting anti‐LAT1 mAbs detect an epitope on LAT1‐CD98hc complexes on the cell surface. Based on these results, LAT1 may be a promising anticancer target and Macaca fascicularis can be used in preclinical studies with antihuman LAT1 mAbs.

Towards therapeutic antibodies to membrane oncoproteins by a robust strategy using rats immunized with transfectants expressing target molecules fused to green fluorescent protein

Cell-surface molecules containing growth factor receptors, adhesion molecules and transporter proteins are often over-expressed in various cancer cells, and could be regarded as suitable targets for therapeutic monoclonal antibodies (mAb). Anti-cancer therapeutic mAb are claimed to bind these cell-surface molecules on viable cancer cells: therefore, it is necessary to produce mAb recognizing epitopes on the extracellular domains of native but not denatured proteins. We have experienced difficulty in obtaining mAb bound to viable cancer cells using synthetic peptides or recombinant proteins produced in bacteria as immunogens, although these immunogens are relatively easy to prepare. In this context, we have concluded that viable cancer cells or cells transfected with cDNA encoding target proteins are suitable immunogens for the production of anti-cancer therapeutic mAb. Furthermore, we selected rats as the immunized animals, because of their excellent capacity to generate diverse antibodies. Because many target candidates are multi-pass (type IV) membrane proteins, such as 7-pass G protein-coupled receptors and 12-pass transporter proteins belonging to the solute carrier family, and their possible immunogenic extracellular regions are very small, production of specific mAb was extremely difficult. In this review, we summarize the successful preparation and characterization of rat mAb immunized against the extracellular domain of type I, type II and type IV membrane oncoproteins fused to green fluorescent protein as an approach using reverse genetics, and also introduce the discovery of cell-death-inducing antibodies as an approach using forward genetics and a strategy to produce reshaped antibodies using mimotope peptides as the immunogen.

HER2-targeted gene transfer

Selective transfer of genes to specific cells remains a barrier to successful utilization of somatic gene therapy. We hypothesized that the human epidermal growth factor receptor-2 (HER2, also called ErbB2), a membrane tyrosine kinase highly expressed in many epithelial tumors, could be an immunological target for gene transfer. To test this hypothesis in vitro, we non-covalently linked a luciferase expression vector (pRSVLuc) to a humanized HER2 antibody (rhuMAbHER2) covalently modified with poly-L-lysine bridges (PL). This complex (PL-rhuMAbHER2) was tested for its ability to direct gene transfer to HER2 expressing cells in vitro using NIH3T3 (HER2 nonexpressing) and NIH3T3.HER2 (HER2 expressing) cell lines as a model system. Twenty-four hours after exposing NIH3T3.HER2 cells to the PL-rhuMAbHER2-pRSVLuc complexes and 100 microM chloroquine, luciferase expression was 180-fold higher than that obtained from a conjugate made with an isotype-matched antibody against an irrelevant target. Exposing the HER2-expressing adenocarcinoma cell lines BT474 and SKBR3 to the HER2-targeted complexes also resulted in successful gene transfer and expression. Gene transfer was specific for the HER2 receptor, because preincubation of HER2-expressing cells with unconjugated rhuMAbHER2 decreased complex-mediated luciferase expression by 95%. These studies suggest that HER2 may be an appropriate target for selective gene transfer and that PL-rhuMAbHER2-DNA complexes may be a useful vehicle for directing gene transfer to cells that express HER2.

Type I receptor tyrosine kinases as targets for therapy in breast cancer

Breast carcinomas express high levels of type I tyrosine kinase receptors and their ligands. For these reason therapies directed at these receptors have the potential to be useful anticancer agents. A series of monoclonal antibodies (MAbs)3 directed against the EGF receptor and the closely related erbB2/HER2/neu receptor are currently under evaluation. These MAbs have shown promising preclinical activity and "chimeric" and "humanized" MAbs have been produced in order to obviate the problem of host immune reactions. These antibodies are currently being tested in clinical trials either alone or in combination with chemotherapeutic agents. Clinical activity with anti-HER2/neu MAbs has been documented in patients with advanced breast cancer. In addition, compounds that inhibit receptor tyrosine kinases have shown significant preclinical activity and are potential candidates for clinical testing.

Engineering high affinity humanized anti-p185HER2/anti-CD3 bispecific F(ab')2 for efficient lysis of p185HER2 overexpressing tumor cells

We previously constructed a humanized anti-p185HER2/anti-CD3 bispecific antibody variant, BsF(ab')2 v1 which retargets the cytotoxic activity of human T cells in vitro against human breast tumor cells which overexpress the p185HER2 product of the HER2/neu (c-erbB-2) protooncogene. Subsequently we identified an improved anti-CD3 variant, v9, which binds to T cells with approx. 100-fold higher affinity than the original variant, v1. Here we demonstrate that BsF(ab')2 v9 is more potent than BsF(ab')2 v1 in stimulating the proliferation of both resting peripheral blood lymphocytes (PBL) and IL-2-activated, long-term cultured T lymphocytes (ATL). In addition, at low concentrations (0.01-1 ng/ml) BsF(ab')2 v9 is much more efficient than BsF(ab')2 v1 in directing lysis of p185HER2-overexpressing tumor cells by IL-2 activated PBL. In contrast, at higher concentration BsF(ab')2 v9 and BsF(ab')2 v1 have similar potency in retargeted cytotoxicity. At BsF(ab')2 v9 concentrations of > or = 1 ng/ml the susceptibility of p185HER2-expressing tumor cells to lysis is apparently independent of the level of p185HER2 expression. At lower concentrations of BsF(ab')2 v9 and/or lower ratios of effector to target cells the extent of lysis is reduced, in some cases improving the selectivity of lysis of high p185HER2 expressors over low expressors. Thus selection of a high affinity anti-CD3 arm is likely important in the design of BsF(ab')2 for retargeting the cytotoxicity of T cells to tumors. The dose of BsF(ab')2 v9 in any future clinical evaluation will require optimization to maximize anti-tumor efficacy whilst minimizing potential toxicity against normal tissue expressing p185HER2.

Biotechnological and gene therapeutic strategies in cancer treatment

New anti-cancer agents are being developed which incorporate cancer-cell-specific recognition functions and are thus able to distinguish between normal and tumor cells. Recognition is dependent on the enhanced expression of antigenic determinants on the surface of tumor cells. The ErbB-2 receptor (ErbB-2R) is overproduced in a high percentage of adenocarcinomas arising in the breast, ovary, lung and stomach, when compared to normal cells. The tumor-enriched expression and extracellular accessibility make this receptor a suitable target for directed tumor therapy. A gene expressing the single-chain antibody molecule (scFv), specific for the extracellular domain of the ErbB-2R, was constructed by joining cDNAs encoding the light- and heavy-chain variable domains of the monoclonal antibody (mAb) FRP5. This scFv-encoding gene has been used as a targeting domain for two effectors: (i) A recombinant immunotoxin-encoding gene was constructed by adding sequences encoding a modified Pseudomonas aeroginosa exotoxin A (ETA) to the scFv-encoding DNA. (ii) Cytotoxic T-lymphocytes (CTL) with specificity for ErbB-2R-producing tumor cells were generated by retroviral transfer of a chimeric gene which encodes the scFv(FRP5), a hinge region and the zeta-chain of the T-cell receptor (TCR) complex. The bacterially produced recombinant immunotoxin scFv(FRP5)-ETA binds specifically to the ErbB-2R and displays both in vitro and in vivo cytotoxic effects selective for tumor cells producing high levels of the ErbB-2R. Target cells expressing the ErbB-2R gene were lysed in vitro with high specificity by the scFv::hinge::zeta-expressing T-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-12 augments the generation of autologous tumor-reactive CD8+ cytotoxic T lymphocytes from tumor-infiltrating lymphocytes

Human tumor-infiltrating lymphocytes (TIL) were obtained from breast cancer, renal cancer or neuroblastoma to investigate the generation of autologous tumor-reactive CD8+ cytotoxic T lymphocytes (CTL). When TIL were cultured with interleukin (IL)-2 (100 U/ml), the growth of TIL peaked around 8-10 days after the initiation of culture. In contrast, the proliferation of TIL cultured with IL-2 plus IL-12 peaked around 4-5 days after culture and tumor cells rapidly disappeared from the culture. To determine the generation of autologous tumor-reactive CD8+ CTL, TIL-derived CD8+ T cells were separated by FACStar. Both IL-2-activated and IL-2 plus IL-12-activated TIL-CD8+ T cells showed the same level of lymphokine-activated killer activity against a variety of tumor cells. However, TIL-CD8+ T cells activated with IL-2 plus IL-12 revealed greatly augmented cytotoxicity against autologous tumor cells compared with that induced by IL-2 alone. The autologous tumor cell-killing activity of TIL-CD8+ CTL was significantly inhibited by the addition of F(ab)2 anti-CD3 monoclonal antibody, indicating that these CTL recognize autologous tumor antigen through T cell receptor. These results imply that IL-12 is a novel cytokine which facilitates the generation of autologous tumor-reactive CD8+ CTL from TIL.

Tumor-associated glycoantigen, sialyl Lewis(a) as a target for bispecific antibody-directed adoptive tumor immunotherapy

The KM231 mAb recognizing sialyl Lewis(a) (sLe(a)) epitope of glycoprotein or glycolipid expressed on various human cancers was used to prepare bispecific antibody (BSAb) containing anti-CD3 x anti-sLe(a) mAb. The effect of anti-CD3 x anti-sLe(a) BSAb on the induction of cytotoxicity by activated T cells was investigated. The activated CD3+ T cells expressing CD8 or CD4 were induced from human peripheral blood mononuclear cells by culture with recombinant IL-2 plus immobilized anti-CD3 mAb. The activated CD8+ and CD4+ T cells showed marginal cytotoxicity against tumor cells by themselves. However, addition of anti-CD3 x anti-sLe(a) BSAb resulted in a great augmentation of their cytotoxicity against gastrointestinal tumor cells. The BSAb also triggered IL-2 production of CD4+ helper/killer T cells during lysis of tumor cells. Moreover, the BSAb was demonstrated to have a potent in vivo antitumor activity against human colon cancer implanted in nude mice by combination with CD4+ helper/killer cells. These results demonstrated that sLe(a) antigen might be a good target molecule for BSAb-directed adoptive tumor immunotherapy.

Receptor blockade with monoclonal antibodies as anti-cancer therapy

Human tumors express high levels of growth factors and their receptors, and many types of malignant cells appear to exhibit autocrine- or paracrine-stimulated growth. Therefore, antireceptor directed therapies have the potential of being useful anti-cancer agents. A series of murine monoclonal antibodies (MAbs) directed against human growth factor receptors and their corresponding growth factors have been produced. MAbs against the receptors for epidermal growth factor, Her2/Neu, transferrin, insulin-like growth factor, interleukin, (IL)-2 and IL-1 are currently being evaluated. MAbs directed against epidermal growth factor, transforming growth factor-alpha, bombesin, IL-2, and IL-6 also are under study. These MAbs have shown promising preclinical activity, and some of them are being tested in clinical trials. So far, anti-tumor responses have been observed with anti-IL-2 receptor, anti-bombesin and anti-IL-6 MAbs. Further research is focusing in the production of "chimeric" and "humanized" MAbs, in order to obviate the problem of host immune reactions.

Expression of tumor-associated glycoantigen, sialyl Lewis(a), in human head and neck squamous cell carcinoma and its application to tumor immunotherapy

The glycoantigen sialyl Lewis(a) (sLe(a)) is widely expressed on a variety of gastrointestinal tumor cells. Here, we immunohistochemically demonstrated the expression of sLe(a) antigen in 54% (7 out of 13) of human head and neck squamous cell carcinoma (H-NSCC) samples. Frequent expression of sLe(a antigen was also demonstrated on a variety of H-NSCC cell lines using flow cytometry. Both CD4+ and CD8+ T cells, which were activated with immobilized OKT3 monoclonal antibody plus interleukin-2, showed augmented cytotoxicity against sLe(a)-positive H-NSCC, including autologous tumor cells, on targeting with anti-CD3 x anti-sLe(a) bispecific antibody, suggesting that sLe(a) antigen is a good target molecule for bispecific antibody-dependent adoptive tumor immunotherapy of human head and neck cancer.

Molecular biology of breast cancer

BACKGROUND

A gene responsible for an inherited predisposition to breast and ovarian cancer has been localized to the long arm of chromosome 17 and termed BRCA1. As well as being closely linked to breast/ovarian cancer cases, this gene may be involved in up to 45% of site-specific breast cancers. The identification and cloning of the BRCA1 gene is imminent, and will facilitate the screening and counselling of families at risk of breast cancer, and in the longer term may open up new therapeutic possibilities. The tumour suppressor gene TP53 is mutated in 25%-40% of cases of sporadic breast cancer, and is associated with an aggressive tumour phenotype and poor prognosis in both node-positive and node-negative cases. The pattern of mutations in this tumour suppressor gene shows a higher than expected frequency of G to T transversions, mostly restricted to the highly conserved domain in exons 5 to 8. In many, but not all cases, point mutation of one allele is accompanied by deletion of the remaining normal allele at chromosome 17p13. Abnormalities of TP53 appear to be relatively early events in tumorigenesis, being present in ductal carcinoma in situ lesions. The retinoblastoma gene RB1 shows a variety of abnormalities in about 20% of breast cancers, and there may be an association with TP53 mutations. Other abnormalities which occur with a particularly high incidence in breast cancer include allele loss at chromosome 1p/1q, 3p, 6q, 11p, 16q and 18q. The ERBB2 oncogene encodes a transmembrane receptor tyrosine kinase whose ligand has recently been claimed to be the heregulin family in man.(ABSTRACT TRUNCATED AT 250 WORDS)

Targeting of T lymphocytes against EGF-receptor+ tumor cells by bispecific monoclonal antibodies: requirement of CD3 molecule cross-linking for T-cell activation

Targeting of T lymphocytes against epidermal growth-factor-receptor (EGF-R)+ tumor cells was achieved by constructing a hybrid hybridoma which secretes an anti-EGF-R/anti-CD3 bispecific monoclonal antibody (biMAb) of hybrid isotype (IgG1/IgG2a). Purification of biMAb molecules from parental anti-EGF-R and anti-CD3 MAbs was performed by protein-A chromatography. The purified biMAb was able to trigger the lysis of EGF-R+ tumor cell lines (A431, IGROV-1, MDA-468 and U-87) and of NIH-3T3 transfectants expressing human EGF-R by cytolytic T lymphocytes, but it was ineffective in the case of EGF-R-negative tumor targets. Normal EGF-R+ cells (keratinocytes and endometrial cells) were also susceptible to biMAb-targeted cytolysis. However, the amount of biMAb required to induce half-maximal cytolysis of tumor cells over-expressing the EGF-R molecule (A431) was considerably lower than that required to induce lysis of EGF-R+ tumor or normal cells which express EGF-R at considerably lower density. The ability of such biMAbs to deliver activation signals to T cells was evaluated by Ca++ mobilization and lymphokine production experiments. The soluble anti-EGF-R/anti-CD3 biMAb failed to induce intracellular Ca++ increases, which occurred only after cross-linking induced by an anti-mouse IgG antibody. Secretion of lymphokines (IFN-gamma, TNF-alpha and GM-CSF) was induced by contact of the biMAb-coated effector cells with the relevant tumor target, whereas the soluble biMAb was virtually ineffective. In addition, biMAb-coated effector cells retained the ability to recognize and to lyse EGF-R+ tumor cells for a prolonged period of time. Our data indicate that activation of effector cells targeted by biMAbs can only occur at the tumor site, where cross-linking of surface CD3 molecules is induced by contact with the tumor cells.

Local antitumour treatment in carcinoma patients with bispecific-monoclonal-antibody-redirected T cells

In a pilot clinical study carcinoma patients with malignant ascites or pleural exudates have been treated locally with autologous lymphocytes activated ex vivo and redirected towards tumour cells with bispecific monoclonal antibodies. BIS-1, the bispecific monoclonal antibody used in this study, combines specificity against a tumour-associated antigen, AMOC-31, present on carcinomas, with a specificity against the CD3 complex on T lymphocytes. Patients selected for treatment had malignant pleural or peritoneal effusions. Treatment consisted of isolating autologous peripheral blood lymphocytes, ex vivo activation, incubation with bispecific monoclonal antibodies and injection at the effusion site of these BIS-1-redirected lymphocytes. To evaluate the effects of the bispecific monoclonal antibody, five patients received treatments with activated lymphocytes without bispecific antibodies. Effusion samples taken before and at various times after treatment were analysed by immunocytology and for the presence of the soluble factors carcinoembryonic antigen (CEA), interleukin-6 (IL-6), tumour necrosis factor (TNF), C-reactive protein and soluble CD8. In this way both immune activation and anti-tumour activity could be monitored. Conjugate formation between tumour cells and activated lymphocytes was seen as soon as 4 h after injection of BIS-1-redirected activated lymphocytes, followed by a disappearance or reduction of tumour cells after 24-48 h. In parallel with this, the soluble tumour marker CEA decreased in the effusion fluid following injection with the BIS-1-redirected lymphocytes. Furthermore, a steep increase in local granulocyte numbers was observed in the effusion fluid, which reached a maximum 24-48 h after the start of the treatment. Also levels of IL-6 and TNF were greatly elevated. The data suggest that the treatment induces both antitumour activity and a strong local inflammatory reaction. This is accompanied by no or only minor local and systemic toxicity, i.e. mild fever, which disappeared as the local inflammatory reaction diminished 48-72 h after treatment.

C-erbB-2 oncoprotein immunostaining in serous effusions

The product of c-erbB-2 gene is detected in a proportion of carcinomas from various sites and is generally associated with a high degree of malignancy. A series of 58 effusions containing malignant cells and 16 cytologically negative serous effusions was assessed by immunocytochemical methods for c-erbB-2 expression using the monoclonal antibody NCL-B11, which recognizes the internal domain of the c-erbB-2 oncoprotein. Both alcohol-fixed smears and cell blocks from formalin-fixed specimens were used. A crisp, clear cut membrane-associated positive staining was evident in 51% (30/58) malignant effusions and was restricted to metastatic adenocarcinomas. Breast and ovarian cancers showed the highest incidence of positivity. Mesotheliomas as well as non-neoplastic effusions were consistently negative. Paraffin blocks from formalin-fixed cells displayed a weak immunoreactivity when compared with their alcohol-fixed counterparts. The study shows that the c-erbB-2 oncoprotein can be easily identified in standard cytological smears: it can be of assistance in differentiating adenocarcinomas from mesotheliomas, and in selected cases it can provide a further prognostic indicator, replacing tissue immunohistochemistry.

Specific targeting of in vitro-activated human antitumour effector cells using anti-CD3 x anti-c-erbB-2 bispecific antibody

Bispecific antibody (BSAb) consisting of anti-CD3 plus anti-c-erbB-2 Fab fragments for the application to adoptive tumour immunotherapy was prepared. This bifunctional hetero-F(ab')2 antibody reacted with both human CD3+ T cells and c-erbB-2 positive human tumour cells. Human CD8+ T cells activated with immobilized anti-CD3 plus interleukin 2 showed marginal cytotoxicity against tumour cells. However, addition of the prepared BSAb into the culture resulted in a marked augmentation of the cytotoxicity by the activated CD8+ T cells in a dose-dependent manner. The enhanced cytotoxicity of CD8+ T cells in the presence of BSAb was specific for c-erbB-2 positive tumour cells. Moreover, it was demonstrated that anti-CD3 x anti-c-erbB-2 BSAb was also effective for the specific targeting of various kinds of in vitro-activated antitumour effector cells such as lymphokine-activated killer cells, CD4+ helper/killer cells, gamma delta T cells and activated tumour-infiltrating CD8+ T cells. These results indicated that BSAb consisted of anti-CD3 and anti-c-erbB-2 will become a useful tool for the adoptive tumour immunotherapy of human cancer expressing c-erbB-2 oncogene products.

Monoclonal antibodies in the detection and therapy of micrometastatic epithelial cancers

The initial promise of monoclonal antibodies as major therapeutic agents in human epithelial cancer has not been realized. Inaccessibility of cells in solid tumors due to factors such as the nature of the vascular endothelia and high pressure in the tumor are primarily responsible for the failure of antibody therapy. Although new strategies employing recombinant antibodies and immunoglobulins designed to actively engage the immune system may prove beneficial, micrometastatic tumor cells (at the stage of minimal residual disease) are likely to be the only suitable targets for antibody therapy. The diagnostic approaches to identify and characterize these cells and their use for prognosis and monitoring adjuvant immunotherapy is discussed.

In vitro anti-tumor activity of anti-c-erbB-2 x anti-CD3 epsilon bifunctional monoclonal antibody

With the aim of developing an effective cancer immunotherapy for common epithelial cancer, a new class of bifunctional antibody (BFA) was developed; one arm of this BFA recognized c-erbB-2 gene product, and the other arm recognized CD3 epsilon, a T-cell specific surface antigen. Application of this BFA with human peripheral blood lymphocytes exhibited specific anti-tumor activity in vitro on a breast tumor cell line, ZR-75-1, which expressed abundant c-erbB-2 gene product on its cell surface. These results indicate that BFA recognizing an oncogene product on cell surface is a potential new agent for cancer immunotherapy.