MUC1-positive Tumor Cells Research Articles

MUC1 Specific Immune Responses Enhanced by Coadministration of Liposomal DDA/MPLA and Lipoglycopeptide.

Mucin 1 (MUC1), a well-known tumor-associated antigen and attractive target for tumor immunotherapy, is overexpressed in most human epithelial adenomas with aberrant glycosylation. However, its low immunogenicity impedes the development of MUC1-targeted antitumor vaccines. In this study, we investigated three liposomal adjuvant systems containing toll-like receptor 4 (TLR4) agonist monophosphoryl lipid A (MPLA) and auxiliary lipids of different charges: cationic lipid dimethyldioctadecylammonium (DDA), neutral lipid distearoylglycerophosphocholine (DSPC) or anionic lipid dioleoylphosphatidylglycerol (DOPG), respectively. ELISA assay evidenced that the positively charged DDA/MPLA liposomes are potent immune activators, which induced remarkable levels of anti-MUC1 antibodies and exhibited robust Th1-biased immune responses. Importantly, the antibodies induced by DDA/MPLA liposomes efficiently recognized and killed MUC1-positive tumor cells through complement-mediated cytotoxicity. In addition, antibody titers in mice immunized with P2-MUC1 vaccine were significantly higher than those from mice immunized with P1-MUC1 or MUC1 vaccine, which indicated that the lipid conjugated on MUC1 antigen also played important role for immunomodulation. This study suggested that the liposomal DDA/MPLA with lipid-MUC1 is a promising antitumor vaccine, which can be used for the immunotherapy of various epithelial carcinomas represented by breast cancer.

Mesoporous silica@chitosan@gold nanoparticles as “on/off” optical biosensor and pH-sensitive theranostic platform against cancer

A cancer nanotheranostic system was fabricated based on mesoporous silica@chitosan@gold (MCM@CS@Au) nanosystem targeted by aptamer toward the MUC-1 positive tumor cells. Subsequently, curcumin as an efficient herbal anticancer drug was first encapsulated into chitosan-triphosphate nanoparticles and then the resulted nanoparticle was loaded into the nanosystem (MCM@CS@Au-Apt). The nanosystem successful fabrication was approved at each synthesis step through FTIR, XRD, BET, DLS, FE-SEM, HRTEM, and fluorescence spectroscopy. Besides, the interaction between aptamer and curcumin was evaluated using full atomistic molecular dynamics simulations. The mechanism of curcumin release was likewise investigated through different kinetic models. Afterwards, the potential of the designed nanosystem in targeted imaging, and drug delivery was evaluated using fluorescence microscopy and flow cytometry. It was found that the energy transfer between the base pairs in the hairpin of double strands of DNA aptamer acts as a quencher for MCM@CS@Au fluorescence culminating in an “on/off” optical biosensor. On the other hand, the presence of pH-sensitive chitosan nanoparticles creates smart nanosystem to deliver more curcumin into the desired cells. Indeed, when the aptamer specifically binds to the MUC-1 receptor, its double strands separate under the low pH condition, leading to the drug release and the recovery of the fluorescence (“On” state). Based on the toxicity results, this nanosystem had more toxicity toward the MUC-1-positive tumor cells than MUC-1-negative cells, representing its selective targeting. Therefore, this nanosystem could be introduced as a smart anticancer nanotheranostic system for tracing particular biomarkers (MUC-1), non-invasive fluorescence imaging, and targeted curcumin delivery.

An efficient and safe MUC1-dendritic cell-derived exosome conjugate vaccine elicits potent cellular and humoral immunity and tumor inhibition in vivo

Antitumor vaccines are a promising strategy for preventing or treating cancers by eliciting antitumor immune responses and inducing protective immunity against specific antigens expressed on tumor cells. Vaccine formulations that enhance the humoral and cellular immune responses of vaccine candidates would be highly beneficial but are still limited. Here we developed an antitumor vaccine candidate by conjugating a MUC1 glycopeptide antigen to dendritic cell-derived exosomes (Dex). In vivo, the MUC1-Dex construct induced high MUC1-specific IgG antibody titers with strong binding affinities for MUC1-positive tumor cells and promoted cytokine secretion. Moreover, CD8+ T cells from immunized mice exhibited strong cytotoxicity against MUC1-positive tumor cells. Importantly, in both preventative and therapeutic tumor-bearing mouse models, the construct inhibited tumor growth and prolonged survival. Collectively, these results demonstrate that Dex is a promising vaccine carrier that can be used as adjuvant to enhance the immunological efficacy of tumor vaccines. Statement of significance•We prepared an efficient and biosafe antitumor vaccine candidate by conjugating Dex with MUC1 glycopeptide using a two-step biorthogonal crosslinking strategy.•MUC1-Dex enhanced the expression of costimulatory molecules CD80 and CD86 on DCs to promote their maturation whilst simultaneously upregulating MHC I and MHC II expression to increase antigen presentation by DCs.•MUC1-Dex conjugates stimulated the production of MUC1-specific IgG antibodies in vivo, and the antibodies bound strongly to MUC1-expressing tumor cells.•The constructed vaccines induced a strong antibody response and antigen specific CTLs to kill the tumor and delayed tumor development in a therapeutic and prophylactic tumor bearing mouse model.

Mucin-1 Protein Is a Prognostic Marker for Pancreatic Ductal Adenocarcinoma: Results From the CONKO-001 Study.

BackgroundThe Mucin-family protein, MUC1, impacts on carcinogenesis and tumor invasion. We evaluated the impact of MUC1 expression on outcome in a cohort of 158 patients with resected pancreatic ductal adenocarcinomas (PDAC) in the CONKO-001 study (adjuvant gemcitabine [gem] vs. observation [obs]).MethodsThe percentage of MUC1-positive tumor cells by immunohistochemistry (IHC) and the staining intensity were evaluated by two observers blinded to outcome. The numeric values of both parameters were multiplied, resulting in an immunoreactivity score (IRS) ranging from 0 to 12. The level of MUC1 expression was defined as follows: IRS 0–4 (low) vs IRS >4 (high). Outcomes in terms of disease-free (DFS) and overall survival (OS) were evaluated by Kaplan–Meier method, log-rank tests and Cox regressions.ResultsIn total, tumors of 158 study patients were eligible for immunohistochemistry of MUC1. High cytoplasmic MUC1 expression was associated with impaired DFS and OS in the overall study population (hazard ratio (HR) for DFS: 0.49, 95% CI 0.31 to 0.78, p = .003; HR for OS: 0.46, 95% CI 0.29 to 0.73, p = .001). In the study arms, prognostic effects of MUC1 were also evident in the observation group (HR for DFS: 0.55; 95% CI 0.29 to 1.04, p = .062; HR for OS: 0.34, 95% CI 0.17 to 0.67, p = .001) and trending in the gem group (HR for DFS: 0.48, 95% CI 0.24 to 0.95, p = .041; HR for OS: 0.56, 95% CI 0.28 to1.11, p = .093).ConclusionOur data suggest that MUC1 expression is a powerful prognostic marker in patients with PDAC after curatively intended resection.

Aptamer-guided DNA tetrahedrons as a photo-responsive drug delivery system for Mucin 1-expressing breast cancer cells

Photosensitizers are crucial for photodynamic therapy. However, conventional photosensitizers have poor selectivity, and their targeted delivery by nanocarriers has become a major research focus. The aim of this study was to construct a targeted delivery system for new photosensitizers using aptamer-guided DNA tetrahedra. Mucin 1 protein is overexpressed in some cancer cells. The sequence of a Mucin 1 aptamer (MUC1) was linked to a DNA tetrahedron to form MUC1 aptamer-modified tetrahedral nanostructures (MUC1-TDNs) for the selective targeting of MUC1-positive tumor cells. The photosensitizer, TMPyP4, was loaded into MUC1-TDNs owing to the high affinity of TMPyP4 for DNA; consequently, a targeted photosensitizer delivery system (MUC1-TDNs-TMPyP4, MTT) was obtained. This system allowed for the selective delivery of TMPyP4 to MUC1-positive cancer cells. Moreover, MTT promoted the production of reactive oxygen species as well as cytotoxicity in MUC1-positive cells, while less killing effect were observed in MUC1-negative cells. We designed a MUC1-targeted delivery system of photosensitizers based on DNA tetrahedron, thus providing a new approach for the targeted release of photosensitizers.

Abstract A014: Phase I clinical trial with PD-1/MUC1 CAR-pNK92 immunotherapy

Abstract Mucin1 (MUC1) proteins represent a family of high molecular weight trans-membrane glycoproteins that protect epithelial cells and mediate signal transduction by communication with extracellular stimuli. On the other hand, MUC1 has been observed to be overexpressed and glycosylated in adenocarcinoma, making it an ideal molecular target for cancer treatment. MUC1 based antibody and specific chimeric antigen receptors (CARs) modified T/NK cells exhibit strong antibody-dependent or direct-cell cytotoxicity to MUC1 positive tumor cells. However, treatment failure with MUC1-targeted therapy was usually caused by tumor microenvironment (TME)-driven immune suppression. PD-L1 has been identified as a negative checkpoint molecule that promotes immune evasion of tumor cells. The interaction of PD-1 and PD-L1 inhibits the function of tumor-infiltrating lymphocytes (TILs) or infused T/NK cells while activating the negative immune-regulatory cells in TME, such as regulatory T-cells and MDSCs. To overcome these barriers, we engineered clinically applicable NK-92 cells by lentiviral gene transfer to express chimeric antigen receptors comprising an anti-MUC1 scFv antibody fusion protein with CD28-CD137 as a signaling moiety and truncated PD-1 peptide. NK92 cells expressing anti-MUC1 CAR specifically and efficiently lysed MUC1 positive tumor cells in vitro and in vivo. The safety of NK-92 cell administration has been demonstrated by numerous phase I clinical trials. In our study, 13 patients with different kinds of tumors (lung cancer, pancreatic cancer, colon cancer and ovarian cancer) with positive PD-L1 and MUC-1 expression were enrolled. CAR-NK cells were infused (1×109 cells/time) into these patients. Of 13 patients, 3 patients were withdrawn, 9 patients (69.2%) showed stable disease and 1 patient showed progressive disease. The cytokine level and hematologic changes were monitored to evaluate the safety. Severe cytokine storm and/or bone marrow suppression were not observed. From this phase I clinical trial we found that CAR-NK therapy has a broad prospect of application as a new cellular immunotherapy due to its stable clinical efficacy, mild side effects and ease of preparation. Citation Format: Qiao Li, Yi Wang, Ming Lin, Leiming Xia, Yangyi Bao, Xiang Sun, Lin Yang. Phase I clinical trial with PD-1/MUC1 CAR-pNK92 immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A014.

Novel Bispecific Aptamer Enhances Immune Cytotoxicity Against MUC1-Positive Tumor Cells by MUC1-CD16 Dual Targeting.

A promising strategy in cancer immunotherapy is the employment of a bispecific agent that can bind with both tumor markers and immunocytes for recruitment of lymphocytes to tumor sites and enhancement of anticancer immune reactions. Mucin1 (MUC1) is a tumor marker overexpressed in almost all adenocarcinomas, making it a potentially important therapeutic target. CD16 is expressed in several types of immunocytes, including NK cells, γδ-T cells, monocytes, and macrophages. In this study, we constructed the first bispecific aptamer (BBiApt) targeting both MUC1 and CD16. This aptamer consisted of two MUC1 aptamers and two CD16 aptamers linked together by three 60 nt DNA spacers. Compared with monovalent MUC1 or CD16 aptamers, BBiApt showed more potent avidity to both MUC1-positive tumor cells and CD16-positive immunocytes. Competition experiments indicated that BBiApt and monovalent aptamers bound to the same sites on the target cells. Moreover, BBiApt recruited more CD16-positive immunocytes around MUC1-positive tumor cells and enhanced the immune cytotoxicity against the tumor cells in vitro. The results suggest that, apart from bispecific antibodies, bispecific aptamers may also potentially serve as a novel strategy for targeted enhancement of antitumor immune reactions against MUC1-expressing malignancies.

Single domain based bispecific antibody, Muc1-Bi-1, and its humanized form, Muc1-Bi-2, induce potent cancer cell killing in muc1 positive tumor cells.

Muc1 is one of the most studied tumor antigens. However, antibodies or antibody-toxin conjugates against Muc1 have not shown significant efficacy for tumors with Muc1 overexpression. In this study, we employed bispecific antibody approach to target Muc1 positive tumor cells. A novel bispecific antibody, Muc1-Bi-1, was constructed by linking single domain antibodies, anti-Muc1-VHH and anti-CD16-VHH. Muc1-Bi-2, the humanized form of Muc1-Bi-1, was also constructed by grafting. Both Muc1-Bi bispecific antibodies can be efficiently expressed and purified from bacteria. In vitro, the Muc1-Bi bispecific antibodies can recruit Natural Killer (NK) cells to drive potent and specific cell killing of Muc1-overexpressing tumor cells. In xenograft model, the Muc1-Bi bispecific antibodies can suppress tumor growth in the presence of human peripheral blood mononuclear cells (PBMC). These data suggested that the single domain based Muc1-Bi may provide a valid strategy for targeting tumors with Muc1 overexpression.

Sequential administration of a MVA-based MUC1 cancer vaccine and the TLR9 ligand Litenimod (Li28) improves local immune defense against tumors

TG4010 is an immunotherapeutic vaccine based on Modified Vaccinia virus Ankara (MVA) encoding the human tumor-associated antigen MUC1 and human IL-2. In combination with first-line standard of care chemotherapy in advanced metastatic non-small-cell lung cancer (NSCLC), repeated subcutaneous injection of TG4010 improved progression-free survival in phase 2b clinical trials. In preclinical tumor models, MVATG9931, the research version of TG4010, conferred antigen-specific responses against the weak antigen human MUC1. The combination of a suboptimal dose of MVATG9931 and the type B TLR9 ligand Litenimod (Li28) markedly increased survival in a subcutaneous RMA-MUC1 tumor model compared to the treatment with MVATG9931 or Li28 alone. The requirements for this protection were (i) de novo synthesis of MUC1, (ii) Li28 delivered several hours after MVATG9931 at the same site, (iii) at least two vaccination cycles, and (iv) implantation of MUC1-positive tumor cells in the vicinity to the vaccination site. Subcutaneously injected MVATG9931 allowed transient local gene expression and induced the local accumulation of MCP-1, RANTES, M-CSF, IL-15/IL-15R and IP-10. After repeated injection, CD4+ and CD8+ T lymphocytes, B lymphocytes, NK cells, pDCs, neutrophils, and macrophages accumulated around the injection site, local RANTES levels remained high. Delayed injection of Li28 into this environment, led to further accumulation of macrophages, the secretion of IL-18 and IL-1 beta, and an increase of the percentage of activated CD69+ NK cell. Combination treatment augmented the number of activated CD86+ DCs in the draining lymph nodes and increased the percentage of KLRG1+ CD127−CD8+ T cells at the injection site. In vivo depletion of macrophages around the injection site by Clodronate liposomes reduced local IL-18 levels and diminished survival rates significantly. Thus, sequential administration of MVATG9931 and Li28 improves local innate and adaptive immune defense against tumors, arguing for intratumoral delivery of this peculiar sequential combination therapy.

A Novel Approach of Targeted Immunotherapy against Adenocarcinoma Cells with Nanoparticles Modified by CD16 and MUC1 Aptamers

Mucin 1 (MUC1) is a potentially important target of cancer therapy, being a glycoprotein that is overexpressed on cell surface of many types of adenocarcinomas, including breast, ovarian, colon, lung, and prostatic cancers. Several MUC1‐targeted drug delivery systems have been developed and reported, but mobilizing natural killer cells (NK) to fight against MUC1‐positive tumor has not been attempted. In this study, we introduced a novel amphipathic nanoparticle (NP) for enhancing the NK cytotoxicity to MUC1‐positive cancer cells. The amphipathic NP had CD16 and MUC1 aptamers on its surface and was designed to bind with both the CD16‐positive NK cells and the MUC1‐positive tumor cells and pull the two types of cells close to each other. The fabricated amphipathic NP had an average size of 574 nm. The aptamers’ conjugation with the NP was confirmed by DNA hybridization experiments. Dark‐field microscopy revealed that the amphipathic NP could recruit more NK cells to the vicinity of MUC1‐positive cancer cells. Additionally, the amphipathic NP significantly enhanced the NK cytotoxicity to MUC1‐positive cancer cells (p < 0.01), but not that to the MUC1‐negative control cells. The results suggest that NK cells may potentially be mobilized to selectively fight against MUC1‐positive cancer cells.

Abstract 2901: Cell surface-associated anti-MUC1-derived signal peptide antibodies: implications for cancer diagnostics and therapy

Abstract The MUC1 tumor associated antigen is highly expressed on a range of tumors. Its broad distribution on primary tumors and metastases renders it an attractive target for immunotherapy. After synthesis MUC1 is cleaved, yielding a large soluble extracellular alpha subunit containing the tandem repeats array (TRA) domain specifically bound, via non-covalent interaction, to a smaller beta subunit containing the transmembrane and cytoplasmic domains. Thus far, inconclusive efficacy has been reported for anti-MUC1 antibodies directed against the soluble alpha subunit. Targeting the cell bound beta subunit, may bypass limitations posed by circulating TRA domains. MUC1's signal peptide (SP) domain promiscuously binds multiple MHC class II and Class I alleles, which upon vaccination, generated robust T-cell immunity against MUC1-positive tumors. This is a first demonstration of non-MHC associated, MUC1 specific, cell surfaces presence for MUC1 SP domain. Polyclonal and monoclonal antibodies generated against MUC1 SP domain specifically bind a large variety of MUC1-positive human solid and hematological tumor cell lines; MUC1-positive bone marrow derived plasma cells obtained from multiple myeloma (MM)-patients, but not MUC1 negative tumors cells, and normal naive primary blood and epithelial cells. Membranal MUC1 SP appears mainly as an independent entity but also co localized with the full MUC1 molecule. MUC1-SP specific binding in BM-derived plasma cells can assist in selecting patients to be treated with anti-MUC1 SP therapeutic vaccine, ImMucin. A therapeutic potential of the anti-MUC1 SP antibodies was suggested by their ability to support of complement-mediated lysis of MUC1-positive tumor cells but not MUC1 negative tumor cells and normal naive primary epithelial cells. Moreover in preliminary studies, anti-MUC1 SP antibodies delayed tumor growth of murine DA-3 cells transfected with human MUC1. These findings suggest a novel cell surface presence of MUC1 SP domain, a potential therapeutic benefit for anti-MUC1 SP antibodies in MUC1-positive tumors and a selection tool for MM patients to be treated with the anti-MUC1 SP vaccine, ImMucin. Note: This abstract was not presented at the meeting. Citation Format: Riva Kovjazin, Galit Horn, Nechama I. Smorodinsky, Michael Y. Shapira, Lior Carmon. Cell surface-associated anti-MUC1-derived signal peptide antibodies: implications for cancer diagnostics and therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2901. doi:10.1158/1538-7445.AM2014-2901

Cell Surface-Associated Anti-MUC1-Derived Signal Peptide Antibodies: Implications for Cancer Diagnostics and Therapy

The MUC1 tumor associated antigen is highly expressed on a range of tumors. Its broad distribution on primary tumors and metastases renders it an attractive target for immunotherapy. After synthesis MUC1 is cleaved, yielding a large soluble extracellular alpha subunit containing the tandem repeats array (TRA) domain specifically bound, via non-covalent interaction, to a smaller beta subunit containing the transmembrane and cytoplasmic domains. Thus far, inconclusive efficacy has been reported for anti-MUC1 antibodies directed against the soluble alpha subunit. Targeting the cell bound beta subunit, may bypass limitations posed by circulating TRA domains. MUC1’s signal peptide (SP) domain promiscuously binds multiple MHC class II and Class I alleles, which upon vaccination, generated robust T-cell immunity against MUC1-positive tumors. This is a first demonstration of non-MHC associated, MUC1 specific, cell surfaces presence for MUC1 SP domain. Polyclonal and monoclonal antibodies generated against MUC1 SP domain specifically bind a large variety of MUC1-positive human solid and haematological tumor cell lines; MUC1-positive bone marrow derived plasma cells obtained from multiple myeloma (MM)-patients, but not MUC1 negative tumors cells, and normal naive primary blood and epithelial cells. Membranal MUC1 SP appears mainly as an independent entity but also co-localized with the full MUC1 molecule. MUC1-SP specific binding in BM-derived plasma cells can assist in selecting patients to be treated with anti-MUC1 SP therapeutic vaccine, ImMucin. A therapeutic potential of the anti-MUC1 SP antibodies was suggested by their ability to support of complement-mediated lysis of MUC1-positive tumor cells but not MUC1 negative tumor cells and normal naive primary epithelial cells. These findings suggest a novel cell surface presence of MUC1 SP domain, a potential therapeutic benefit for anti-MUC1 SP antibodies in MUC1-positive tumors and a selection tool for MM patients to be treated with the anti-MUC1 SP vaccine, ImMucin.

Novel MUC1 Aptamer Selectively Delivers Cytotoxic Agent to Cancer Cells In Vitro

Chemotherapy is a primary treatment for cancer, but its efficacy is often limited by the adverse effects of cytotoxic agents. Targeted drug delivery may reduce the non-specific toxicity of chemotherapy by selectively directing anticancer drugs to tumor cells. MUC1 protein is an attractive target for tumor-specific drug delivery owning to its overexpression in most adenocarcinomas. In this study, a novel MUC1 aptamer is exploited as the targeting ligand for carrying doxorubicin (Dox) to cancer cells. We developed an 86-base DNA aptamer (MA3) that bound to a peptide epitope of MUC1 with a K d of 38.3 nM and minimal cross reactivity to albumin. Using A549 lung cancer and MCF-7 breast cancer cells as MUC1-expressing models, MA3 was found to preferentially bind to MUC1-positive but not MUC1-negative cells. An aptamer-doxorubicin complex (Apt-Dox) was formulated by intercalating doxorubicin into the DNA structure of MA3. Apt-Dox was found capable of carrying doxorubicin into MUC1-positive tumor cells, while significantly reducing the drug intake by MUC1-negative cells. Moreover, Apt-Dox retained the efficacy of doxorubicin against MUC1-positive tumor cells, but lowered the toxicity to MUC1-negative cells (P<0.01). The results suggest that the MUC1 aptamer may have potential utility as a targeting ligand for selective delivery of cytotoxic agent to MUC1-expressing tumors.

Targeted Immuotherapy of Muc1 Positive Carcinomas with Genetically Engineered Human T Cells.

Mucin1 (Muc1), a tumor-associated antigen, is overexpressed in many adenocarcinomas including breast, pancreas, ovary, prostate, colon, and in multiple myeloma. Therefore, tumor associated Muc1 is an attractive target for immunotherapy. Several types of immunotherapeutic approaches targeting Muc1 are currently being tested in preclinical and clinical settings. A major limitation of vaccination strategies involving tumor antigens is the lack of induction of sufficient number of antigen-specific effector T cells systemically to achieve objective clinical response. In an effort to redirect activated T cells towards tumor cells, we constructed lentiviral vectors expressing chimeric receptors consisting of a novel single chain variable domain (scFv) of a monoclonal antibody against Muc1 combined with various cytoplasmic signaling domains such as CD3 Zeta, CD28 and OX40. Human peripheral blood T cells were lentivirally transduced with chimeric immune receptors in order to redirect them towards Muc1 positive tumor cells. A sufficiently high level of transduction (>80) was achieved without any positive selection. Transduced T cells were stimulated and expanded over a period of 10–15 days in the presence of IL-2. Gene-modified T cells efficiently recognized Muc1 expressing tumor target cells in an MHC-independent manner as demonstrated by antigen-specific tumor cell cytolysis. Furthermore, transduced T cells showed antigen-specific proliferation and secreted interferon gamma upon ligation with Muc1 on tumor cells. These results indicate that generation of large numbers of antigen specific T cells for clinical application is possible through the use of this chimeric immune receptor gene transfer strategy. This approach might be an attractive strategy in a minimal residual disease setting complementing traditional therapies based on surgery, radiation and/or chemotherapy. Therefore, present study suggests a promising new strategy for cancer immunotherapy using gene-modified T cells. [Display omitted]

Reversal of tolerance to human MUC1 antigen in MUC1 transgenic mice immunized with fusions of dendritic and carcinoma cells.

Immunological unresponsiveness established by the elimination or anergy of self-reactive lymphocyte clones is of importance to immunization against tumor-associated antigens. In this study, we have investigated induction of immunity against the human MUC1 carcinoma-associated antigen in MUC1 transgenic mice unresponsive to MUC1 antigen. Immunization of adult MUC1 transgenic mice with irradiated MUC1-positive tumor cells was unsuccessful in reversing unresponsiveness to MUC1. By contrast, fusions of dendritic cells with MUC1-positive tumor cells induced cellular and humoral immunity against MUC1. Immunization with the dendritic cell fusions that express MUC1 resulted in the rejection of established metastases and no apparent autoimmunity against normal tissues. These findings demonstrate that unresponsiveness to the MUC1 tumor-associated antigen is reversible by immunization with heterokaryons of dendritic cells and MUC1-positive carcinoma cells.