A new cancer-associated antigen defined by a monoclonal antibody against a synthetic carbohydrate chain

Carbohydrate antigens can be designed by referring to previously defined carbohydrate structures. We have generated a novel monoclonal antibody (MAb) (Flα-75) against an artificially designed antigen (Flα), using organic-synthetic chemistry methods and hybridoma technology. Flα (GalβI → 4GlcNAcβI → 6GalNAαI → Ser/Thr) belongs to core type 6 of O-linked glycans, which has not been previously reported in human cancers. To produce antibodies against Flα, a glycolipid was synthesized which carries the carbohydrate portion of Flα on a ceramide foundation (GalβI → 4GlcNAcβI → 6GalNAcαI → Cer). The MAbs we obtained (Flα-75, Flα-87) specifically recognized Flα and had only a very weak or no cross-reactivity with other glycolipids similar to Flα. We investigated the expression of Fin in human tissues, including 110 gastric cancers, 73 colon cancers and 42 pancreatic cancers. Flα was found in human cancerous tissues but not in normal adult tissues. The rate of positive staining with Flα-75 was 80.0% for gastric cancer, 52.4% for pancreatic cancer and 38.4% for colon cancer. Flα-75 also reacted with the tissues neighboring gastric and pancreatic tumors but not intensely. Among fetal tissues, Flα-75 reacted with the pyloric glands of the stomach, the centro-acinar cells of the pancreas, the convoluted tubules of the kidney and the terminal bronchioles of the lung.     

A novel gastric-cancer-associated mucin antigen defined by a monoclonal antibody A3D4

De-glycosylation of mucins may expose new tumor-associated core protein epitopes. In this study, to attempt to develop useful markers for gastric cancers, we have purified and de-glycosylated gastric mucin and tried to establish monoclonal antibodies (MAbs). A MAb designated A3D4 among established MAbs was shown to react with gastric cancer with high frequency, but not with normal gastric epithelium. Among normal digestive organs, only the colon and gall bladder were positive for MAb A3D4. The incidence of positivity in gastric cancer was 75% for intestinal-type adenocarcinoma (n = 28), 40% for solid-type adenocarcinoma (n = 5) and 33% for signet/scirrhous-type adenocarcinoma (n = 15). Interestingly, adenoma and intestinal metaplasia (IM) with chronic gastritis or peptic ulcer were negative for MAb A3D4, whereas 8 out of 13 cases (62%) of IM with gastric cancer was positive. Western-blot analysis using the lysate from normal colon tissues revealed a high-molecular-weight (>300-kDa) smear-like band. Immunohistochemical analysis indicated that the reactivity of MAb A3D4 was clearly increased when tissue sections were pre-treated with periodic acid or O-glycanase, while it was decreased by pre-treatment with trypsin or protease V8. There was no reactivity with the synthetic peptide encompassing the tandem-repeat sequence of MUC2 or MUC3. These data suggest that MAb A3D4 detects a novel gastric-cancer-associated mucin antigen whose epitope may be peptide in nature. Int. J. Cancer 73:795–801, 1997. © 1997 Wiley-Liss, Inc.     

Development and characterization of a mouse monoclonal antibody against antimicrobial peptide tachyplesin I

Monoclonal antibodies against tachyplesin I (TP I) were developed to study its mechanisms of activity, a kind of cationic antimicrobial peptides (AMPs), in vivo or in vitro, and to purify TP I from expression products. The synthesized TP I was chemically conjugated with the carrier protein BSA and then injected into BALB/c mice. Positive hybridomas were screened by indirect enzyme-linked immunosorbent assay (ELISA) using TP I and subcloned three times with limiting dilution. Five MAbs effective in detecting the native TP I (named 2D8, 3B8, 5H2, 6B12, and 8F5) were obtained. Isotyping of all obtained MAbs indicated that MAbs 2D8, 3B8, 5H2, and 8F5 belong to IgG1, and MAb 6B12 belongs to IgG2a. Specificity assay showed that MAb 8F5 had almost the same level of specificity to natural TP I, recombinant TP I, and synthesized TP I and TP II, but did not cross-react with control peptides. These results suggest that the synthetic AMP conjugates can elicit antibodies against native AMPs and can be used to detect antimicrobial peptides.     

Radioimaging of human glioma xenografts with 123I labeled monoclonal antibody G-22 against glioma-associated antigen

Summary Monoclonal antibody (MCA) G-22 is directed against a human glioma-associated surface antigen. Its availability for the radioimmunodetection of human glioma was analyzed by utilizing the xenografts in athymic mice. Nude mice with subcutaneous grafts of U251-MG or U251-SP glioma received intravenous administration of ¹²³I or ¹³¹I labeled F(ab)2 fragment or whole immunoglobulin. Results of radioimaging revealed that ¹²³I-labeled antibody was better than the ¹³¹I-labeled. It was also noted that administration of ¹²³I-labeled F(ab)2 fragment of G-22 MCA enabled the imaging of human glioma xenografts weighing 80–650 mg after 48 hours. When biodistribution of ¹²³I MCA was compared between G-22 and control antibodies, the percentages of dose/g in tumors were 5.228–1.799 at 30 hours and 4.112–1.132 at 48 hours with G-22 and they were 4.164–1.248 and 0.314–0.142 with control. The tumor/blood ratio until 72 hours after injection was constantly above 1 with G-22 and less than 1 with control antibody. These results indicate the potential usefulness of G-22 MCA for the radioimmunodetection of human gliomas.     

A novel monoclonal antibody against canine monocytes/macrophages

The production and partial characterization of a monoclonal antibody, the IgG1 IH1, which recognizes an antigen distributed in canine monocytes/macrophages, is reported here. The distribution and apparent molecular weight of the antigen recognized by the IH1 MAb was determined in peripheral blood leukocytes, peripheral blood monocyte-derived macrophages and tissue sections of spleen, liver and skin, using Western blotting, immunocytochemistry, immunohistochemistry and flow cytometry. The IH1 MAb-recognized antigen was detected in Western blotting under non-reducing conditions spread out as a large band covering the position corresponding to the migration of molecules with molecular weights from 55 to 73 kDa. The IH1 MAb labeled blood monocytes, tissue macrophages in lymph nodes, and in the mantle zone of the spleen, and Kupffer cells in the liver. It did not react with human cells. In flow cytometric analysis, the IH1 MAb reacted with a subpopulation of monocytes. The MAb described herein may become a valuable tool for diagnosis and research on canine diseases.     

Negatively charged AuNP modified with monoclonal antibody against novel tumor antigen FAT1 for tumor targeting

Background

Herein, we demonstrated the use of a newly generated anti FAT1 antibody (clone mAB198.3) for intracellular delivery of anionic gold NPs, to form active targeting Au nanoparticles with high payload characteristics.

Methods

In vitro characterizations were determined by DLS, confocal microscopy, TEM, western blot, MALDI-TOF MS/MS analysis, MTT, ICP-MS and flow cytometry analysis. In vivo targeting efficacy was investigated by in vivo bio-imaging study and ICP-MS.

Results

The specificity of the FAT1 recognition in colon cancer was confirmed by pre-adsorbing mAb198.3, adsorption dramatically abolished the antibody reactivity on colon cancer, thus confirming the binding specificity. The DLS size distribution profile of the AuCOOH, AuCOOH(Cy5)_ mAb198.3, AuCOOH(Cy5)_isotype has showed that the modified gold nanoparticles are well dispersed in water, PBS buffer and cell culture medium with 10 % FBS. By TEM measurement, the size of Au nanoparticles with spherical morphology is about 10–20 nm. AuCOOH_198.3 NPs were stable in an acidic environment, as well as in PBS buffer, cell culture media and media with 10 % serum. MTT results revealed that Au nanoparticles have well biocompatibility. TEM results indicated that conjugation of mAb198.3 on Au nanoparticles can be an effective delivery vehicle for negatively charged gold nanoparticles and increased its intracellular transport. It was also demonstrated by confocal microscopy that AuCOOH(Cy5)_mAb198.3 could attach to the cell membrane in very short time, then gradually delivered into cells. After 4 h incubation, almost all AuCOOH(Cy5)_mAb198.3 have been uptaken into or surrounding the cytoplasm and nucleus. In vivo results showed that only about 20 % of AuCOOH accumulated in tumor site due to EPR effect, while nearly 90 % of AuCOOH_mAb198.3 was found in tumor, providing sufficient evidence for receptor-specific targeting by mAb198.3.

Conclusion

According to in vitro and in vivo research results, the intracellular uptake of negatively charged AuCOOH_mAB198.3 particles is enhanced to a greater extent. Thus, AuCOOH_mAb198.3 holds significant potential to improve the treatment of cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0214-x) contains supplementary material, which is available to authorized users.     

Prognostic significance of HLA class I expression in osteosarcoma defined by anti-pan HLA class I monoclonal antibody, EMR8-5

With the goal of establishing efficacious peptide-based immunotherapy for patients with bone and soft tissue sarcomas, we previously identified the cytotoxic T lymphocyte-defined osteosarcoma antigenic gene Papillomavirus binding factor. The present study was designed to determine the status of HLA class I expression in osteosarcoma and other bone and soft tissue sarcomas. Seventy-four formalin-fixed paraffin-embedded specimens of various bone and soft tissue sarcomas, including 33 osteosarcomas, were stained with the anti-HLA class I monoclonal antibody EMR8-5, which we recently generated. The expression of HLA class I was lost or downregulated in 46 of these specimens (62%). With respect to osteosarcoma, loss or downregulation of HLA class I expression was seen in 13 (52%) of 25 primary tumors and seven (88%) of eight metastatic tumors. In six of 11 HLA class I-negative osteosarcoma specimens, the expression of beta-2 microglobulin was also lost. Subsequently the prognostic significance of HLA class I expression was analyzed in 21 patients with osteosarcoma who had completed multidrug neoadjuvant chemotherapy and undergone adequate surgery. Patients with osteosarcoma highly expressing HLA class I showed significantly better overall and event-free survival than those with HLA class I-negative osteosarcoma. In contrast, such prognostic significance of HLA class I expression was not found in 15 patients with malignant fibrous histiocytoma of soft tissue. These findings suggest that the class I-restricted cytotoxic T lymphocyte pathway plays a major role in immune surveillance of patients with osteosarcoma.     

A novel monoclonal antibody against squamous cell carcinoma.

The monoclonal antibody, INS-2, was raised against rat fibroblasts transformed by open reading frames E6 and E7 of human papillomavirus (HPV) DNA. In immunoperoxidase testing of frozen sections, the INS-2 antibody was reactive with all squamous cell carcinomas of the uterine cervix and esophagus tested. In contrast, no antibody binding was detected with adenocarcinomas of various origins. Similarly, normal tissues, lymphoid cells and erythrocytes from multiple donors were negative, except that binding localized at basal cells in normal squamous epithelium was observed. Interestingly, strong staining was observed in dysplastic cells of cervical intraepithelial neoplasia and at the growing edge of squamous cell carcinomas. The antigen for the INS-2 antibody is a non-sialyl glycoprotein with Mw. 40,000 and appears to be a squamous cell-specific cell differentiation marker, although it is not related to HPV-DNA-derived protein.     

Human leukocyte antigen class I gene mutations in cervical cancer.

BACKGROUND: Various mechanisms contribute to the loss of human leukocyte antigen (HLA) class I expression that is frequently observed in cancers. Although some single allele losses have been ascribed to mutations in HLA class I genes, direct evidence for this phenomenon in vivo is still lacking. Thus, we investigated whether HLA class I gene mutations could account for the loss of allele-specific expression in cervical carcinomas. METHODS: We used polymerase chain reaction-based techniques, including sequencing, oligonucleotide hybridization, and microsatellite analysis, to identify HLA class I gene defects in two tumor-derived cell lines and to confirm the presence of these defects in the original tumors. RESULTS: In one tumor, in exon 2 of the HLA-B15 gene, a four-nucleotide insertion resulted in a stop codon in exon 3. In the other tumor, in two duplicated copies of the HLA-A24 gene, single-point mutations resulted in stop codons in exons 2 and 5. CONCLUSIONS: To our knowledge, this is the first report of HLA class I gene mutations identified in primary tumors that lead to loss of allelic expression in tumor cells. Such tumor-specific mutations may permit the cell to escape HLA class I-restricted cytotoxic T-cell responses.     

A novel neutralizing monoclonal antibody against cell-binding polypeptide of ricin

One strain of neutralizing monoclonal antibody (MAb) against cell-binding polypeptide of ricin, named 3E1, was generated efficiently. The antibody recognized the linearity epitope of RTB located in a toxin structure domain characterized by Western blotting. The safe period of mice for intraperitoneal injection of 100 microg of antibody was 20 min after intraperitoneal injection of 2 microg of Ricin (10 times LD50). The neutralizing MAb we obtained could be developed into an immunotherapeutic agent to counteract the use of ricin as a terrorist or biological warfare weapon. It might be useful, as well, for antibody-based prophylaxis.     

肿瘤相关抗原OVA66单克隆抗体的制备和鉴定

目的：制备和鉴定人卵巢癌cDNA文库筛选到的肿瘤相关抗原OVA66的单克隆抗体,为研究其生物学功能提供手段。方法：采用基因重组方法构建pET32bOVA66重组表达质粒,经大肠杆菌诱导表达OVA66融合蛋白,利用NiTED亲和层析技术分离纯化HisOVA66融合蛋白;采用经典的杂交瘤技术制备OVA66单克隆抗体;ELISA和Western blotting鉴定单克隆抗体的生物学和免疫学特性,并对OVA66单克隆抗体在细胞免疫荧光法、流式细胞术和免疫组化等方法中进行了初步应用。结果：成功构建重组表达载体pET32bOVA66,并诱导表达和纯化OVA66融合蛋白。制备获得两株小鼠OVA66单克隆抗体杂交廇细胞株5F4和4G9。两株细胞分泌的抗体亚类均为IgG1,轻链为κ型,亲和力常数Ka分别为2.96×1010和0.4×1010L/mol,初步表位分析结果显示两者针对不同的抗原表位;两株抗体均可以采用细胞免疫荧光和流式细胞术检测OVA66的表达,5F4还可通过免疫组织化学检测肿瘤组织中OVA66的表达。结论：成功制备两株特异性的小鼠OVA66单克隆抗体杂交瘤细胞株,为进一步研究OVA66的生物学特性和临床应用奠定了基础。     

Production of monoclonal antibody alpha Pro3 recognizing a human prostatic carcinoma antigen

The monoclonal antibody alpha Pro3 recognizes an antigen concentrated in human primary prostatic carcinoma tissue removed surgically. Although the antigen was detectable in extracts of human normal and malignant nonprostatic tissue, as well as in benign prostate tissue, quantitative absorption analysis revealed a substantially greater quantity of the antigen in malignant prostate tissue. The antigen recognized by alpha Pro3 in primary prostatic carcinoma has an apparent nonreduced molecular weight of 175,000 and an apparent subunit molecular weight of 54,000. This antigen, p54, appears to be present on the surface of cultured prostatic tumor cells of the PC-3 cell line, but its location in vivo has not been defined. Successful competition between alpha Pro3 and prostatic carcinoma patient serum immunoglobulin for a Mr 54,000 antigen (reduced molecular weight) present in prostatic carcinoma tissue extract suggests that p54 may play a significant role in the immunobiology of prostatic carcinoma. alpha Pro3 has potential as a sensitive probe for an antigen relevant to human tumor biology.     

A monoclonal antibody, CSTO-1, against a stomach adenocarcinoma-associated antigen

A monoclonal antibody, CSTO-1, has been produced against a stomach adenocarcinoma-associated antigen. The antibody is cytotoxic to stomach, colon, and lung adenocarcinoma lines but is completely noncytotoxic to normal blood elements and leukemic cell lines. The monoclonal antibody reacts with tumor cell membranes in enzyme-linked immunosorbent assay and is negative to cell membranes from various normal tissues. By immunoperoxidase testing, the antibody reacts with 18 of 22 stomach adenocarcinomas, 11 of 16 colon adenocarcinomas, 3 of 4 squamous cell carcinomas of the lung, and 1 of 4 lung adenocarcinomas. In addition, the antibody reacts with the superficial epithelium of normal tissues such as colon, stomach, esophagus, acinar cells and duct epithelium of the pancreas, bronchial epithelium of the lung, and sweat duct epithelium of the skin. Thus, the CSTO-1 antibody reacts to an antigen present in normal superficial epithelia, as well as on various tumors. It is of potential use in detecting these antigens on tumor sections and eventually may be used in immunotherapy.     

Tumor-associated antigen defined by a monoclonal antibody against neuraminidase-treated human cancer cells

A monoclonal antibody, MH-A6, was produced by immunization with a human gastric cancer cell line, MKN 74, treated with neuraminidase. The antigen defined by the monoclonal antibody was detected on various tumor tissues and a limited number of normal tissues in immunoperoxidase assay, and the expression of MH-A6 antigen was not influenced by neuraminidase treatment except for some cases of tumor tissues. Interestingly, neuraminidase treatment enhanced binding of the antibody on some adenocarcinomas, but diminished binding of the antibody on squamous cell carcinomas. Both treatment of the immunizing tissues with trypsin and periodic acid diminished binding of the antibody. In isolation of MH-A6 antigen from MKN 74 cells by the monoclonal antibody coupled-affinity column, the epitope exists on molecules with molecular weights of 30,000 and 72,000, and with an acidic pH range in two-dimensional electrophoresis. CEA and CA 19-9 activities were not detected in purified MH-A6 antigen by solid-phase radioimmunoassay, and the reactivity of the MH-A6 antibody with CEA and CA 19-9 was not detected in enzyme-linked immunosorbent assay. Hemagglutination observed between erythrocytes (Lewisa, Lewisb, or NE-treated) and anti-Lewisa, anti-Lewisb sera, or anti-T-agglutinin (peanut lectin), respectively, was not inhibited by MH-A6 antigen. The results suggest that MH-A6 antigen is a tumor-associated antigen, probably glycoprotein, and different from CEA, CA 19-9, Lewisa, Lewisb, and Thomsen-Friedreich (T) antigen.     

The novel monoclonal antibody MH8-4 inhibiting cell motility recognizes integrin alpha 3: inverse of its expression withmetastases in colon cancer

The molecular basis of cell motility is obviously highly complex and is considered to be controlled by a number of molecular systems including cell adhesion molecules, their receptors, cytoskeletal components, a junctional unit connecting cytoskeletal components and membrane receptors, and various peptide growth factors. The possible involvement of proteins at the cell surface in controlling cell motility has been systematically investigated. Previously, we have addressed this question using functional monoclonal antibodies (MAbs), which inhibit cell motility as probes. In order to further identify cell surface molecules involved in metastasis of gastrointestinal tumors, the present study utilized an approach based on the selection of a colon cancer cell line RPMI4788, which showed high motility out of a large number of human gastrointestinal tumor cell lines. MAb MH8-4 was established after immunization of mice with RPMI4788 and selected on the basis of inhibition of RPMI4788 cell migration in a transwell penetration assay. MH8-4 inhibited the phagokinetic tract motility of various cancer cell lines. A cDNA cloning revealed that MH8-4 recognized a specific protein structure, integrin alpha 3. In order to determine whether these experimental results are of relevance with respect to actual human gastrointestinal tumors, we investigated integrin alpha 3 expression in 40 colon cancers with distant metastases. Our immunohistochemical study showed that in almost 27.5% of the cases, the metastatic tumors had lower integrin alpha 3 levels than their corresponding primary tumors. Moreover, there were no primary tumors with lower integrin alpha 3 expression than their corresponding metastatic tumors. Our data suggest that low integrin alpha 3 expression may be associated with the metastatic potential of certain colon cancers.     

Enhancement of colorectal tumor targeting using a novel biparatopic monoclonal antibody against carcinoembryonic antigen in experimental radioimmunoguided surgery.

Biparatopic CEA, carcinoembryonic antigen (MAb) was newly designed and tested as to whether it enhanced the accuracy of tumor detection by reducing non-specific binding in experimental radioimmunoguided surgery. Biparatopic MAb was prepared by using cross-linking of reduced Fab' fragments from PR1A3 and T84.66. Fifty-nine tumors from 2 human colorectal carcinoma cell lines with high (KM-12c) and low (Clone A) carcinoembryonic antigen (CEA) expression were successfully implanted subcutaneously on the backs of 42 nude mice. Tumors were localized using 125I-labeled MAbs: IgG, F(ab')(2) and Fab' of PR1A3, and biparatopic MAb of PR1A3 and T84.66. Radioactivity counted on a portable radioisotope detector correlated well with that counted on a gamma counter (p < 0.001). Accumulations of radioactivity in control mice without tumorigenesis were the greatest in PR1A3 IgG-pretreated mice and the least in biparatopic MAb-pretreated mice. Tumors of 2 cell lines did not differ in the distribution of radiolabeled MAbs. Localization indices of the tumor in various organs revealed 1.3 to 4.1 in PR1A3 IgG-pretreated mice, 2.4 to 6.6 in fragment MAbs of PR1A3-pretreated mice and 2 to 4.6 in biparatopic MAb-pretreated mice. Silver grains and immune staining were predominantly distributed in tumor cells of all types of MAb-pretreated mice. Sensitivity and specificity of tumor localization by radioimmunoguided surgery (RIGS) were the highest in the biparatopic MAb-pretreated mice (90.9% and 94.5%, respectively) and the least in the PR1A3 IgG-pretreated mice (50% and 72%). The biparatopic MAb using 2 anti-CEA MAbs against different epitopes achieved a great affinity and avidity with accurate localization of colorectal carcinoma in experimental radioimmunoguided surgery.     

Immunoselective pressure and human leukocyte antigen class I antigen machinery defects in microsatellite unstable colorectal cancers

In colorectal cancer, the immune response is particularly pronounced against tumors displaying the high microsatellite instability (MSI-H) phenotype. MSI-H tumors accumulate mutations affecting microsatellites located within protein encoding regions (coding microsatellites, cMS), which lead to translational shifts of the respective reading frames. Consequently, novel tumor-specific frameshift-derived neopeptides (FSP) are generated and presented by MSI-H tumor cells, thus eliciting effective cytotoxic immune responses. To analyze whether the immunoselective pressure was reflected by the phenotype of MSI-H colorectal cancer cells, we compared here the expression of antigen processing machinery (APM) components and human leukocyte antigen (HLA) class I antigen subunits in 20 MSI-H and 20 microsatellite-stable (MSS) colorectal cancer using a panel of newly developed APM component-specific monoclonal antibodies. In addition, we did a systematic analysis of mutations at cMS located within APM genes and beta2-microglobulin (beta2m). Total HLA class I antigen loss was observed in 12 (60.0%) of the 20 MSI-H lesions compared with only 6 (30.0%) of the 20 MSS colorectal cancer lesions. Moreover, total loss of membraneous HLA-A staining was significantly more frequent in MSI-H colorectal cancer (P = 0.0024). Mutations at cMS of beta2m and genes encoding APM components (TAP1 and TAP2) were detected in at least 7 (35.0%) of 20 MSI-H colorectal cancers but in none of the MSS colorectal cancers (P = 0.0002). These data show that defects of HLA class I antigen processing and presentation seem to be significantly more frequent in MSI-H than in MSS colorectal cancer, suggesting that in MSI-H colorectal cancer the immunoselective pressure leads to the outgrowth of cells with defects of antigen presentation.     

Human leukocyte antigen class I antigen expression is an independent prognostic factor in ovarian cancer.

PURPOSE: Despite improvements in cancer treatment, the prognosis of ovarian cancer remains low and imperfectly predicted by traditional pathologic criteria. Biomarkers that predict prognosis independently of such criteria shed light on important molecular variations, aiding in the development and targeting of novel therapies. Previous work has shown human leukocyte antigen (HLA) class I antigen expression to be independently predictive of prognosis in colorectal and breast cancer. We investigated the prognostic potential of HLA class I antigen expression by studying a large series of ovarian cancers. EXPERIMENTAL DESIGN: A tissue microarray of 339 ovarian cancer cases linked to prospectively recorded clinicopathologic and follow-up data was constructed. This was stained following a standard immunohistochemical protocol for HLA class I heavy chain (HC-10) and beta(2)-microglobulin (beta(2)-m). HLA class I antigen expression was compared with clinicopathologic factors and overall disease-specific survival using the Pearson chi(2) test, Kaplan-Meier curves, and the log-rank test. Cox regression was used to test for the independence and magnitude of effects. RESULTS: There were no univariate correlations between HLA class I antigen expression and clinicopathologic factors. Deviation from an HC-10(+)/beta(2)-m(+) phenotype correlated with reduced survival in univariate analysis (log-rank, 5.69; P = 0.017); a retained HC-10(+)/beta(2)-m(+) phenotype predicted improved prognosis independently of age, stage, level of cytoreduction, and chemotherapy usage on multivariate analysis (hazard ratio, 0.587; 95% confidence interval, 0.442-0.781; P < 0.001). CONCLUSIONS: HLA class I antigen expression is an independent prognostic marker in ovarian cancer, its loss correlating with a poor prognostic outcome.     

Generation of a recombinant mouse-human chimaeric monoclonal antibody directed against human carcinoembryonic antigen

A procedure was devised for the identification and specific cloning of functionally rearranged variable region immunoglobulin (Ig) gene segments from genomic DNA of a murine hybridoma cell line which produces a high-affinity monoclonal antibody (MAb) directed against human carcinoembryonic antigen (CEA). The cloned, functionally-rearranged murine Ig H-chain and L-chain variable region gene segments were incorporated into plasmid vectors capable of directing the expression of a chimaeric mouse-human antibody molecule with human (gamma 4, kappa) constant region sequences. Expression plasmids were transfected into a mouse myeloma cell line by electroporation and transfectomas secreting functional chimaeric antibody selected. Chimaeric antibody generated by transfectomas was analysed and shown to compete effectively with its murine counterpart for binding to the CEA epitope, and to have an equivalent antigen-binding affinity. This anti-CEA recombinant antibody should find application in in vivo diagnosis by immunoscintigraphy of human colonic carcinoma, and possibly also in therapy of the disease, overcoming some of the difficulties associated with the repeated use of non-human immunoglobulins in human patients.     

Tumour antigen targeted monoclonal antibodies incorporating a novel multimerisation domain significantly enhance antibody dependent cellular cytotoxicity against colon cancer

Tumour antigen targeted antibodies (mAbs) can induce natural killer (NK) cells to kill tumours through antibody dependent cellular cytotoxicity (ADCC) upon engagement of NK cell expressed FcγRIIIa. FcγRIIIa polymorphisms partially dictate the potency of the ADCC response. The high affinity FcγRIIIa-158-valine (V) polymorphism is associated with more potent ADCC response than the low affinity FcγRIIIa-158-phenylalanine (F) polymorphism. Because approximately 45% of patients are homozygous for the FcγRIIIa-158-F polymorphism (FF genotype), their ability to mount ADCC is impaired. We investigated whether a novel mAb capable of binding multiple antigen specific targets and engaging multiple low affinity FcγRIIIa receptors could further enhance ADCC against colon cancer in vitro. Specifically, we generated a novel anti-epidermal growth factor receptor (EGFR) antibody (termed a stradobody?) consisting of an unmodified Fab sequence and two Immunoglobulin G, subclass 1 (IgG1) Fc domains separated by an isoleucine zipper domain and the 12 amino-acid IgG2 hinge. The stradobody? framework induced multimerisation and was associated with increased binding to the EGFR and FcγRIIIa. From a functional perspective, when compared to an unmodified anti-EGFR mAb with a sequence identical to cetuximab (a commercially available anti-EGFR mAb), stradobodies? significantly enhanced ADCC. These effects were observed using both KRAS wild type HT29 and KRAS mutant SW480 colon cancer cells as targets, and by NK cells obtained from healthy donors and a cohort of patients with colon cancer. These data suggest that high avidity cross-linking of multiple tumour surface antigens and multiple NK cell associated FcγRIIIa molecules can enhance ADCC and partially overcome impaired ADCC by FF genotype individuals in vitro.