Anti-idiotype immunization of cancer patients: modulation of the immune response.

Thirty patients with advanced colorectal carcinoma (CRC) were treated with alum-precipitated polyclonal goat anti-idiotypic antibodies (Ab2) to monoclonal anti-CRC antibody CO17-1A (Ab1) in doses between 0.5 and 4 mg per injection. All patients developed anti-anti-idiotypic antibodies (Ab3) with binding specificities on the surfaces of cultured tumor cells similar to the specificity of Ab1. Furthermore, the Ab3 competed with Ab1 for binding to CRC cells. Fractions of Ab3-containing sera obtained after elution of the serum immunoglobulins from CRC cells bound to purified tumor antigen and inhibited binding of Ab2 to Ab1. The Ab3, therefore, may share idiotopes with Ab1. Six patients showed partial clinical remission and seven patients showed arrest of metastases following immunotherapy. Four of the thirteen patients with measurable clinical responses had received Ab2 alone, whereas 9 patients had also received chemotherapy.     

Murine monoclonal anti-idiotope antibody breaks unresponsiveness and induces a specific antibody response to human melanoma-associated proteoglycan antigen in cynomolgus monkeys.

The mouse monoclonal antibody MEM136 (mAb1) is directed against an epitope on human melanoma-associated proteoglycan antigen (MPG). This epitope is also present on various normal human and subhuman tissues. A monoclonal murine anti-idiotope (anti-Id) antibody (mAb2), designated I-Mel-2, was generated against MEM136 and used as a surrogate antigen for the MPG molecule. I-Mel-2 was tested in cynomolgus monkeys (Macaca fascicularis) for its ability to induce anti-MPG humoral responses. All monkeys immunized with Ab2 developed specific anti-anti-idiotype (Ab3) responses that were capable of inhibiting binding of Ab2 to Ab1. Furthermore, I-Mel-2 immune monkey serum contained anti-MPG antibodies (Ab1') that bound to MPG-positive but not to MPG-negative melanoma cell lines. Monkeys immunized with Colo38 melanoma cells (membrane-bound MPG antigen) did not contain anti-MPG antibodies that inhibited the binding of two distinct anti-MPG mAb 125I-labeled MEM136 or 125I-labeled 225.28 to Colo38 cells. The induction of anti-MPG responses in monkeys did not cause any apparent side effects in animals, despite the fact that the MPG antigen is expressed by many normal tissues. The affinity-purified, I-Mel-2 idiotype-specific, Ab3 immunoprecipitated MPG antigen from melanoma cells. Furthermore, the I-Mel-2-induced Ab3 inhibited melanoma cell invasion in an in vitro assay, implying that these antibodies have biological significance.     

Antilymphocyte immunoglobulins stimulate peripheral blood lymphocytes to proliferate and release lymphokines

Five different preparations of antilymphocyte immunoglobulins (ATG) and antithymocyte immunoglobulins (ALG) with good or little clinical response were compared for their hematopoietic and immunological activities. All ATG/ALG lots demonstrated complement-mediated cytotoxicity on peripheral blood mononuclear cells. They had different titers of antibody specificities against lymphocyte cell membrane antigens. Neither clinically effective nor ineffective lots demonstrated any apparent colony stimulating activity on bone marrow mononuclear cells. Purified Natural Killer cells failed to be stimulated by ATG/ALG in liquid culture. ATG/ALG demonstrated potent T-cell stimulating activity comparable to phytohemagglutinin. This stimulation was blocked by anti-IL-2 receptor monoclonal antibodies, and was inhibited dose-dependently by cyclosporin-A. Some clinically ineffective ATG/ALG lots also stimulated T cells to release lymphokines. The differences in these characteristics among ATG/ALG lots provide some clues to guide further efforts to elucidate a key mechanism of therapeutic effectiveness.     

A monoclonal antibody cocktail for detection of micrometastatic tumor cells in the bone marrow of breast cancer patients

We investigated whether monoclonal antibodies (MoAbs) reactive against both acidic and basic cytokeratins alone were sufficient to detect minimal numbers of contaminating epithelial tumor cells in the bone marrow of breast cancer patients. Monoclonal anti-cytokeratin antibodies (AE1 and AE3) were used to stain 14 breast carcinomas by the avidin-biotin-peroxidase technique. Nine tumors (64.3%) showed high reactivity and five (35.7%) showed low or moderate reactivity. Nine MoAbs that proved to be unreactive to light density bone marrow cells by immunoalkaline phosphatase histochemistry were screened for reactivity to breast carcinomas having only low or moderate positivity to cytokeratin antibodies. Three of nine MoAbs showed high percentages of positivity and were selected to supplement the anti-cytokeratin antibodies for immunohistochemical detection of minimal marrow disease in breast cancer patients. A MoAb cocktail was prepared, further tested for reactivity to another five breast carcinomas, and compared with cytokeratin staining alone. The cocktail labeled 100% of carcinoma cells in all the examined specimens. To determine the sensitivity of this panel for detecting minimal numbers of contaminating tumor cells in bone marrow, in vitro mixing experiments were performed. T47D breast carcinoma cells were mixed with bone marrow mononuclear cells at ratios from one tumor cell per 10 bone marrow cells up to one tumor cell per 1 x 10(6) marrow cells, and cytospin preparations were subsequently stained with the MoAb cocktail by the immunoalkaline phosphatase method. Our approach could detect one tumor cell in 1 x 10(5) hematopoietic cells.     

Human response against NP-4, a mouse antibody to carcinoembryonic antigen: human anti-idiotype antibodies mimic an epitope on the tumor antigen.

Anti-idiotype antibodies (Ab2) were purified from a cancer patient treated with NP-4, a murine monoclonal antibody to carcinoembryonic antigen (CEA). These Ab2 were specific for NP-4 and inhibited the binding between NP-4 and CEA. BALB/c mice immunized with these human Ab2 produced anti-Ab2 antibodies that were also reactive with the CEA epitope recognized by NP-4. These results indicate that human Ab2 to NP-4 can antigenically mimic the CEA epitope recognized by NP-4.     

Studies of pancreatic cancer utilizing monoclonal antibodies

Since 1985, 150 patients with pancreatic ductal adenocarcinoma have been treated with the monoclonal antibody BW 494 in four different multicentric trials in Germany. The antibody recognizes a human pancreatic cancer associated antigen and mediates an antibody dependent cellular cytotoxicity (ADCC) in vitro, when human mononuclear cells are coincubated as effector cells. In patients with at advanced unresectable pancreatic cancer there where two phase-I-studies finished in 1987 and 1989, respectively, and one uncontrolled phase-II-study finished in 1988. In 1987, we started a controlled randomized trial in patients with resectable (Whipple) pancreatic cancer, which will be finished in 1990. There were no major side effects if the intravenous antibody application was restricted to a 10-d treatment protocol (up to 370 mg given in 10 different dosages). Human anti-mouse-antibodies could be demonstrated in all patients investigated for within 4 wk after immunotherapy. In patients with advanced pancreatic cancer (n = 87), monoclonal antibody treatment did not induce significant response rates. There was stable disease in 1/3 to 1/2 of the patients lasting three months or longer. Therapeutic success may be expected in patients with minor tumor burden.     

Reactivity of monoclonal anti-K 562 antibodies with cells of leukemia- and lymphoma-patients

For further characterization, monoclonal anti-K 562 antibodies (1) were tested against blood or bone marrow cell samples of patients with various leukemias and lymphomas. One antibody, ZIK-C1-A/D9 (also designated Y) reactive in previous tests exclusively with K 562 cells, but not with normal blood cells, exhibited a selective binding to cells of most AML-patients and CML-patients in myeloid blast crisis. Cells of patients with other hematopoietic malignancies were negative, except three single cases (one lymphosarcoma, one AUL and one hairy cell leukemia). Antibody ZIK-C1-B/H5 (short name H) detected an antigenic determinant, preferentially expressed on cells of AML and CML patients, but also on normal granulocytes and some mononuclear cells. Two additional monoclonal anti-K 562 antibodies, ZIK-C1-A/F5 (short name C) and 2B7, yielded specificities shared by a variety of normal and malignant hematopoietic cells.     

Antibody dependent cell-mediated cytotoxicity using hepatocellular carcinoma reactive monoclonal antibody

We have established monoclonal antibodies from mice immunized with the human hepatocellular carcinoma cell line, hu-H2. One of the antibodies, designated 523(KY-3), was reactive with this hepatocellular carcinoma cell line as well as with the human pancreatic cancer cell line, MIA. Another monoclonal antibody, 512(KY-2), only reacted with the hepato-cellular carcinoma cell lines. Neither antibody reacted with the colon cancer cell line CW3. Pretreatment of peripheral blood mononuclear cells with 523 resulted in enhancement of their natural cytotoxicity to hu-H2 (9.0 vs 18.4% in subject 1, 3.5 vs 14.7% in subject 2, and 14.2 vs 31.0% in subject 3). In contrast, such antibody mediated enhanced natural cytotoxicity was not found by pretreatment of the same peripheral blood mononuclear cell with 512. With the similarity in reactivity of 523, this antibody dependent enhancement was found in natural cytotoxicity to hu-H2 and MIA but not to CW3. Based on the facts that 523 did not have a direct cytopathic effect on these tumours and that this 523-mediated enhanced natural cytotoxicity was inhibited by anti-FcgammaRIII antibody, we concluded that the 523-mediated enhanced cytotoxicity reflects its activity to induce antibody dependent cytotoxic cells. Thus, these results demonstrate that several distinct tumour-specific antigens exist in hepatocellular carcinoma (HCC) and that one of them represents a potentially useful target for immunotherapy of human hepatocellular carcinoma.     

Lymphokine-activated killer cells targeted by monoclonal antibodies to the disialogangliosides GD2 and GD3 specifically lyse human tumor cells of neuroectodermal origin.

Monoclonal antibodies 14.18 (IgG3) and 11C64 (IgG3) directed against disialogangliosides GD2 and GD3, respectively, when used in conjunction with human peripheral blood mononuclear cells (PBMCs) stimulated with human recombinant interleukin (rIL-2) lyse both human melanoma and neuroblastoma cells by antibody-dependent cellular cytotoxicity. Such monoclonal antibody-"armed" effector cells are specifically directed to targets expressing the given disialoganglioside without detectable cross-reactivity. In addition, antibody-dependent cellular cytotoxicity as well as the natural killing ability of human PBMCs is augmented by a brief coincubation with rIL-2. PBMCs augmented by rIL-2 and armed with monoclonal antibodies significantly suppressed tumor growth in the xenotransplant nude mouse model. Our results suggest that once a threshold level of activation of PBMCs is achieved, additional rIL-2 (over three orders of magnitude of concentration) does not significantly enhance cytolytic augmentation. Furthermore, anti-GD3 monoclonal antibody 11C64 together with rIL-2-stimulated PBMCs from melanoma patients with widely differing tumor burdens effectively lyse melanoma tumor targets in antibody-dependent cellular cytotoxicity. Our results also suggest that GD2 and GD3 represent distinct and relevant immunotherapeutic target structures on melanoma whereas GD2 does the same for neuroblastoma tumors. Our data suggest that targeting of activated human effector cells may provide a new and effective cancer immunotherapy protocol.     

Immune responses in advanced colorectal cancer following repeated intradermal vaccination with the anti-CEA murine monoclonal antibody, PR1A3: results of a phase I study

Background and aims The aim was to determine the toxicity, clinical and immune responses to the murine monoclonal anti-carcinoembryonic antigen (CEA) antibody, PR1A3, in patients with advanced colorectal cancer.Materials and methods Fifteen patients with advanced colorectal cancer received either 0.5-, 1.0- or 5.0-mg doses of PR1A3 mixed with 10% w/v Alum adjuvant (Superfos Biosector, Denmark) intradermally at 4-week intervals for 3 months. Patient serum was assessed for anti-idiotypic (Ab2), anti-anti-idiotypic (Ab3) and human anti-mouse antibody (HAMA) reactivity. Peripheral blood mononuclear cell (PBMC) proliferation with phytohaemagglutinin (PHA), CEA and PR1A3, stimulated IL-2, IL-4 and IFN- levels and PR1A3-stimulated IL-2 receptor expression during immunotherapy were determined. Comparisons were made with 16 age-matched controls without malignant disease.Results Hyperimmune sera from 12 of the 15 patients showed Ab2 reactivity with no detectable Ab3 responses. Strong HAMA reactivity was recorded in 7 of the 15 cases with no adverse clinical effect. Delayed-type hypersensitivity (DTH) responses developed in 12 of the 15 patients. Pre-treatment PBMC proliferation with PHA was subnormal in each patient compared with controls, becoming normal (or supranormal) in all patients during immunisation (P<0.001). PBMC proliferation with CEA and PR1A3 increased during immunotherapy (P<0.001) along with stimulated production of IL-2, IFN- and IL-2 receptor expression. Progressive disease was observed in 14 of the 15 patients with minimal toxicity.Conclusion PR1A3 generated limited idiotypic responses but robust DTH reactivity in most patients. In vitro PBMC proliferation with mitogens and recall antigens is greatly increased during the course of immunisation, with a shift in stimulated cytokine profile.     

抗人膀胱癌抗独特型抗体的制备和鉴定

目的：制备抗人膀胱癌抗独特型抗体（Ab2)并进行体外实验和鉴定，探讨通过免疫效应治疗或预防膀胱癌术后复发的可能性。方法：提取膀胱癌抗原（Ag)，应用膀胱癌抗原通过杂交瘤技术制备抗人膀胱癌单克隆抗体（Ab1)，Ab1经胃蛋白酶水解制备Ab1的F（ab‘)2片优，以F（ab‘）2片段免疫新西兰白兔，其血清经凝胶纯化后获抗人膀胱癌抗独特型抗体（Ab2），采用ELISA等方法进行鉴别。结果：Ab2与Ab1呈阳性反应，与BALB／C小鼠γ球蛋白呈阴极反应；Ab2与Ag竞争结合Ab1；Ab2与Ag的结合。结论：Ab1是针对膀胱移行细胞癌的单克隆抗体，Ab2是具有膀胱癌抗原的抗独特型抗体。     

Potential role of anti-idiotype antibodies in active tumor immunotherapy

The tumor-specified cellular and humoral immunity induced by anti-idiotype antibodies (Ab2s) 2F10 and 3A4 has been studied. Ab2s were made against a monoclonal anti-L1210/GZL lymphoma, 11C1. They were screened for their ability to block 11C1 binding to tumor, induce tumor-specific DTH and CTL responses, and induce an anti-tumor humoral response. Two Ab2s, 2F10 and 3A4, which were found to have similar fine specificity and to induce similar cellular and humoral responses, were compared for their ability to elicit tumor-protective immunity. Interestingly, only preimmunization with the 2F10 Ab2 protected animals from live tumor challenge. The possible causes for this discriminatory biological effect induced by otherwise similar Ab2s are discussed.     

Specificities of antibodies to human growth hormone (hGH) in patients treated with hGH: longitudinal study and comparison with the specificities of animal antisera

The specificities of human and animal antibodies (Abs) against human GH (hGH) were analyzed using competition experiments with five monoclonal antibodies to hGH (MAbs). The results indicate that 1) the Abs produced by patients receiving long term hGH therapy as well as Abs of goat, rabbit, and mouse origin recognized the various hGH epitopes defined by the MAbs; 2) the proportion of each Ab population, with a given specificity, differed markedly in different patients and also with time in the same patient; 3) the titer of certain Ab populations was very low in some patients, and 4) polyclonal mouse Abs and some human Abs enhanced the binding of [125I] hGH to insolubilized MAbs.     

Removal of neuroblastoma cells from bone marrow by a direct monoclonal antibody rosetting technique

A one-step direct monoclonal antibody rosetting technique is described for removal of neuroblastoma cells from bone marrow. Two monoclonal antibodies (MoAbs) (BW 575, BW 625) were directly coupled to ox red blood cells by use of CrCl3. The IgG1 antibody BW 575 detects a 95-kD neuroblastoma cell-associated glycoprotein and the IgG3 antibody BW 625 recognizes the ganglioside GD 2. After coupling MoAbs to the erythrocytes, specific strong and stable rosettes were formed with neuroblastoma cells and effectively separated from mononuclear cells using density gradient centrifugation. A total of 1.5% IMR5 neuroblastoma cells were reliably removed from mononuclear cells beyond the limit of detection (less than 0.01%) as judged by tetanus toxin labeling. No impairment of stem cell growth (CFU-GM, BFU-E, CFU-GEMM, CFU-M) was observed. Recovery rate of mononuclear cells ranged between 35 and 69%. A red blood cell/nucleated cell ratio more than 50:1 resulted in increased loss of mononuclear cells and a ratio less than 30:1 in incomplete neuroblastoma cell removal. Using indirect rosettes the purging efficacy was lower and the mononuclear cell loss higher. We conclude that the direct monoclonal antibody rosetting technique may be a technically simple and effective alternative purging method for neuroblastoma patients, which is applicable even in cases demonstrating weak expression of one antigen.     

Identification of tumor associated single-chain Fv by panning and screening antibody phage library using tumor cells

AIM：To study the feasibillity of panning and screening phage-displaying recombinant single-chain variable fragment (ScFv)of anti-tumor monoclonal antibodies for fixed whole cells as the carriers of mAb -binding antigens.METHODS:The recombinant phage displaying libraries for anti-colorectal tumor mAb MC3Ab,MC5Ab and anti-gastric tumormAb mGD1was constructed.Panning and screening were carried out by means of modified fixation of colorectal and gastric tumor cells expressed the mAb-binding antigens.Concordance of binding specificity to tumor cells between phage clones and parent antibodies was analyzed.The phage of positive clones was identified with competitive ELISA,and infected by E.coliHB2151to express soluble ScFv.RESULTS:The ratio of positive clones to MC3-ScF-MC5-ScFv and MGD1-ScFv were 60%,24%and30%,mC3-ScFvandMGD1-ScFvwere60%,24%and 30%.MC3-ScFvhadMr32000confirmed by western blot.The specificity to antigen had no difference between 4positive recombinant phage antibodies and MC3Ab.CONCLUSION:The modified process of fixing whole tumor cells is efficient,convenient and feasible to pan and screen the phage-displaying ScFv of anti-tumor monoclonal antibodies.     

Anti-idiotypic antibody Ab2/3H6 mimics the epitope of the neutralizing anti-HIV-1 monoclonal antibody 2F5

Anti-idiotypic antibodies directed against potentially neutralizing anti-HIV-1 antibodies may mimic epitopes on gp41 otherwise cryptic to the immune system. This study reports the generation of murine monoclonal antibody Ab2/3H6 blocking the binding of human Ab1 2F5 to the synthetic epitope and to gp160 in an enzyme-linked immunosorbent competition assay. Ab2/2H6 diminished the neutralizing potency of 2F5 in an in-vitro neutralization assay. Ab2/3H6 Fab fragments were capable of inducing neutralizing immune and 2F5-specific responses in B6D2F1 mice applying a simple prime-boost regimen of immunization.     

CD4(+) T cell recognition of MHC class II-restricted epitopes from NY-ESO-1 presented by a prevalent HLA DP4 allele: association with NY-ESO-1 antibody production

NY-ESO-1 is a tumor-specific shared antigen with distinctive immunogenicity. Both CD8(+) T cells and class-switched Ab responses have been detected from patients with cancer. In this study, a CD4(+) T cell line was generated from peripheral blood mononuclear cells of a melanoma patient and was shown to recognize NY-ESO-1 peptides presented by HLA-DP4, a dominant MHC class II allele expressed in 43--70% of Caucasians. The ESO p157--170 peptide containing the core region of DP4-restricted T cell epitope was present in a number of tumor cell lines tested and found to be recognized by both CD4(+) T cells as well as HLA-A2-restricted CD8(+) T cells. Thus, the ESO p157--170 epitope represents a potential candidate for cancer vaccines aimed at generating both CD4(+) and CD8(+) T cell responses. More importantly, 16 of 17 melanoma patients who developed Ab against NY-ESO-1 were found to be HLA-DP4-positive. CD4(+) T cells specific for the NY-ESO-1 epitopes were generated from 5 of 6 melanoma patients with NY-ESO-1 Ab. In contrast, no specific DP4-restricted T cells were generated from two patients without detectable NY-ESO-1 Ab. These results suggested that NY-ESO-1-specific DP4-restricted CD4(+) T cells were closely associated with NY-ESO-1 Ab observed in melanoma patients and might play an important role in providing help for activating B cells for NY-ESO-1-specific Ab production.     

Idiotypic regulation of the immune system by the induction of antibodies against anti-idiotypic antibodies.

Anticarbohydrate antibodies (Ab1) were isolated from a rabbit hyperimmunized with Micrococcus lysodeikticus and injected into allotype-matched rabbits in order to obtain specific anti-iodiotypic antibodies (Ab2). Ab2 was isolated by means of a Sepharose column coupled to the anticarbohydrate antibodies and was injected into two allotype-matched rabbits. These latter rabbits produced specific anti-anti-idiotypic antibodies (Ab3) probably sharing idiotypic specificities with Ab1. However, these Ab3 did not react with the antigenic carbohydrate moiety of bacteria. The two rabbits that had produced Ab3 were then immunized with M. lysodeikticus and synthesized anticarbohydrate antibodies (Ab1') bearing idiotypic specificities similar to those of Ab1. The immune repertoire which is effectively expressed in one individual depends not only on the antigenic stimulation but also on the previous idiotypic history of the individual. These data support the concept that the immune system is a functional idiotypic network.     

Micrometastatic cancer cells in bone marrow: in vitro detection with anti-cytokeratin and in vivo labeling with anti-17-1A monoclonal antibodies.

The detection of early micrometastasis or disseminated single tumor cells poses a problem for conventional diagnosis procedures. Using a panel of monoclonal antibodies against cytokeratin and the 17-1A epithelial antigen we identified immunocytochemically tumor cells in bone marrow of patients with breast cancer (n = 155) and colorectal cancer (n = 57) at the time of surgery of the primary tumor. Monoclonal antibody CK2, recognizing the human cytokeratin component 18 in simple epithelia, appeared to be the most suitable reagent because of its negative reaction with bone marrow samples of the noncarcinoma patients (n = 75). Its specificity was further demonstrated in a double-marker staining procedure using an anti-leukocyte common antigen monoclonal antibody (T200) as counterstain. A comparative analysis showed that immunocytology was clearly superior to conventional cytology (n = 212) and histology (n = 39). In 9.5-20.5% of patients without distant metastasis, tumor cells could be detected in bone marrow. We found a significant correlation between tumor cells in bone marrow and conventional risk factors, such as distant metastasis or lymph node involvement. In a first approach toward immunotherapy we demonstrated in 3 patients that infused monoclonal antibody 17-1A can label single tumor cells in bone marrow in vivo. We then used this approach to follow up 7 patients undergoing 17-1A therapy in an adjuvant clinical trial.     

Improved method increases sensitivity for circulating hepatocellular carcinoma cells

AIM:To improve an asialoglycoprotein receptor(ASGPR)-based enrichment method for detection of circulating tumor cells(CTCs)of hepatocellular carcinoma(HCC).METHODS:Peripheral blood samples were collected from healthy subjects,patients with HCC or various other cancers,and patients with hepatic lesions or hepatitis.CTCs were enriched from whole blood by extracting CD45-expressing leukocytes with monoclonal antibody coated-beads following density gradient centrifugation.The remaining cells were cytocentrifuged on polylysine-coated slides.Isolated cells were treated by triple immunofluorescence staining with CD45antibody and a combination of antibodies against ASGPR and carbamoyl phosphate synthetase 1(CPS1),used as liver-specific markers,and costained with DAPI.The cell slide was imaged and stained tumor cells that met preset criteria were counted.Recovery,sensitivity and specificity of the detection methods were determined and compared by spiking experiments with various types of cultured human tumor cell lines.Expression of ASGPR and CPS1 in cultured tumor cells and tumor tissue specimens was analyzed by flow cytometry and triple immunofluorescence staining,respectively.RESULTS:CD45 depletion of leukocytes resulted in a significantly greater recovery of multiple amounts of spiked HCC cells than the ASGPR+selection(P s<0.05).The expression rates of either ASGPR or CPS1were different in various liver cancer cell lines,ranging between 18%and 99%for ASGPR and between 9%and 98%for CPS1.In both human HCC tissues and liver cancer cell lines,there were a few HCC cells that did not stain positive for ASGPR or CPS1.The mixture of monoclonal antibodies against ASGPR and CPS1identified more HCC cells than either antibody alone.However,these antibodies did not detect any tumor cells in blood samples spiked with the human breastcancer cell line MCF-7 and the human renal cancer cell line A498.ASGPR+or/and CPS1+CTCs were detected in 29/32(91%)patients with HCC,but not in patients with any other kind of cancer or any of the other test subjects.Furthermore,the improved method detected a higher CTC count in all patients examined than did the previous method(P=0.001),and consistently achieved 12%-21%higher sensitivity of CTC detection in all seven HCC patients with more than 40 CTCs.CONCLUSION:Negative depletion enrichment combined with identification using a mixture of antibodies against ASGPR and CPS1 improves sensitivity and specificity for detecting circulating HCC cells.