anti-MUC1 Antibody Research Articles

Abstract LB127: A first-in-class bispecific ADC targeting FORL1 and MUC1 exhibits promising anti-tumor activity in a FOLR1low xenograft model

Abstract Folate receptor alpha (FOLR1) is specifically overexpressed in malignant tumors of epithelial origin, including ovarian, lung and breast cancers. While antibody-drug conjugate (ADC) therapies targeting FOLR1 have shown promise in clinical trials, there is still a large proportion of patients, particularly those with low FOLR1 expression, who do not respond, indicating new therapeutic strategies are needed. MUC1 is another tumor-associated antigen that is likewise overexpressed in epithelial ovarian cancer, breast cancer, and NSCLC, among other cancers; analysis of ovarian PDX tumors by immunohistochemistry (IHC) suggests that FOLR1 and MUC1 are both highly expressed in this cancer type. We therefore hypothesized that dual targeting of FOLR1 and MUC1 could provide therapeutic benefit in ovarian cancer as well as a broad range of tumors. We generated a FOLR1 x MUC1 bispecific antibody (bsAb) from anti-FOLR1 and anti-MUC1 monoclonal antibodies that were produced using RenLite® fully human common light chain mice. These parental monoclonal antibodies recognize both human and cynomolgus monkey antigens. Anti-FOLR1 antibodies were highly specific for FOLR1, as they did not recognize other FOLR family members. The anti-MUC1 antibody was previously confirmed to target MUC1-C, the juxtamembrane domain of MUC1, ensuring tumor cell recognition regardless of MUC1 cleavage. Assessment of the novel FORL1 x MUC1 bsAb indicates binding to several ovarian, breast and NSCLC cell lines, and shows enhanced internalization in MDA-MB-468 and T47D cell lines when compared to parental antibodies. Subsequently, the FORL1 x MUC1 bsAb was conjugated to vcMMAE with a DAR of 4, to generate a bispecific ADC, BCG023. BCG023 exhibited superior tumor growth inhibition compared to benchmark ADCs conjugated with the same payload and DAR in a low FOLR1-expressing NSCLC PDX model. These data suggest that targeting FOLR1 and MUC1 with a bispecific ADC is a promising therapeutic strategy for the treatment of ovarian and other tumors. Citation Format: Yifu Zhang, Chengzhang Shang, Chaoshe Guo, Yi Yang. A first-in-class bispecific ADC targeting FORL1 and MUC1 exhibits promising anti-tumor activity in a FOLR1low xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB127.

Abstract 1883: A MUC1 antibody-conjugated with a tubulysin B analog, DXC005, demonstrates excellent synergistic effect in combination with gemcitabine for treatment of pancreatic tumors

Abstract Pancreatic cancer is a malignant tumor with high incidence and mortality. It is difficult to diagnose and detect in the early stage, with low surgical resection rate and high recurrence and metastasis rate after surgery. At present, the clinical therapeutic strategy is extremely limited. The first-line Standard of Care (SOC) for unresectable pancreatic cancer is chemotherapy. The preferred regimen includes gemcitabine combined with albumin paclitaxel or FOLFIRINOX (5-FU+Oxaliplatin+Irinotecan). Due to the limited long-term benefits and toxic side effects of chemotherapy, targeted therapy combined with chemotherapy has become a new therapeutic strategy. MUC1 is a highly glycosylated transmembrane mucin located on the lumen surface of epithelial cells. It can protect cells from extreme factors and plays an important role in tumor cell metabolism, apoptosis, epithelial-mesenchymal transition (EMT) and metastasis. Previous studies have confirmed that MUC1 is highly expressed in a variety of tumors, including pancreatic cancer, and is closely related to poor prognosis. DXC005 is a novel MUC1-targeting antibody-drug conjugate (ADC), generated by conjugating a Tubulysin B analogue to a recombinant humanized anti-Muc1 monoclonal antibody. DXC005 is the first MUC1-ADC IND in China, and is currently in phase I clinical trials. Preclinical studies have confirmed the efficacy of DXC005 monotherapy (2.5 mg/kg, 5 mg/kg, 10 mg/kg in one administration) in the HuPrime ® pancreatic cancer PDX model (PA1194). The tumor growth inhibition (TGI) was 42.53 %, 70.77 %, and 95.58 %, respectively. We want to further clarify whether DXC005 combined with chemotherapeutic drug Gemcitabine can ensure or even improve the efficacy while reducing the dosage of Gemcitabine. In PA1194 xenograft model, DXC005 (3 mg/kg or 6 mg/kg) in combination with Gemcitabine (10 mg/kg) showed significant anti-tumor efficacy with 58.77% and 93.17% TGIs, respectively. In contrast, the treatment with 10 mg/kg of Gemcitabine alone exhibited much less TGI. Furthermore, complete response (CR) was observed in some animals after treatment with DXC005 (6 mg/kg) plus Gemcitabine (10 mg/kg). All groups of treatment are tolerated well, no abnormal animal behavior and body weight loss were observed in the study. The above results concluded that DXC005 combined with Gemcitabine can achieve synergistic effect even with reduced dose of Gemcitabine, which will serve as a support for synergistic application in clinical studies. Citation Format: Xiaobo Cai, Min Cao, Huihui Guo, Qingliang Yang, Yongxiang Chen, Xiangfei Kong, Yong Du, Zhicang Ye, Zhixiang Guo, Lingli Zhang, Lu Bai, Junxiang Jia, Yunxia Zheng, Wei Zheng, Jun Zheng, Wenjun Li, Yuanyuan Huang, Zhongliang Fan, Binbin Chen, Yanlei Yang, Meng Dai, Robert Y. Zhao. A MUC1 antibody-conjugated with a tubulysin B analog, DXC005, demonstrates excellent synergistic effect in combination with gemcitabine for treatment of pancreatic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1883.

Reverse-engineering the anti-MUC1 antibody 139H2 by mass spectrometry-based de novo sequencing.

Mucin 1 (MUC1) is a transmembrane mucin expressed at the apical surface of epithelial cells at mucosal surfaces. MUC1 has a barrier function against bacterial invasion and is well known for its aberrant expression and glycosylation in adenocarcinomas. The MUC1 extracellular domain contains a variable number of tandem repeats (VNTR) of 20 amino acids, which are heavily O-linked glycosylated. Monoclonal antibodies against the MUC1 VNTR are powerful research tools with applications in the diagnosis and treatment of MUC1-expressing cancers. Here, we report direct mass spectrometry-based sequencing of anti-MUC1 hybridoma-derived 139H2 IgG, enabling reverse-engineering of the functional recombinant monoclonal antibody. The crystal structure of the 139H2 Fab fragment in complex with the MUC1 epitope was solved, revealing the molecular basis of 139H2 binding specificity to MUC1 and its tolerance to O-glycosylation of the VNTR. The available sequence of 139H2 will allow further development of MUC1-related diagnostic, targeting, and treatment strategies.

Solution NMR Analysis of O-Glycopeptide-Antibody Interaction.

O-Linked glycans potentially play a functional role in cellular recognition events. Recent structural analyses suggest that O-glycosylation can be a specific signal for a lectin receptor which recognizes both the O-glycan and the adjacent polypeptide region. Further, certain antibodies specifically bind to the O-glycosylated peptide. There is growing interest in the mechanism by which O-glycans on proteins are specifically recognized by lectins and antibodies. The recognition system may be common to many O-glycosylated proteins; however, there is limited 3D structural information on the dual recognition of glycan and protein. This chapter describes a solution NMR analysis of the interaction between MUC1 O-glycopeptide and anti-MUC1 antibody MY.1E12.

Molecular Dynamics Simulation and Docking of MUC1 O-Glycopeptide.

Advances in computer performance and computational simulations allow increasing sophistication in applications in biological systems. Molecular dynamics (MD) simulations are especially suitable for studying conformation, dynamics, and interaction of flexible biomolecules such as free glycans and glycopeptides. Computer simulations are best performed when the scope and limitations in performance have been thoroughly assessed. Proper outputs are obtained only under suitable parameter settings, and results need to be properly validated. In this chapter, we will introduce an example of molecular dynamics simulations of MUC1 O-glycopeptide and its docking to anti-MUC1 antibody Fv fragment.

Possible correlation of apical localization of MUC1 glycoprotein with luminal A-like status of breast cancer

Adjuvant chemotherapy has played a major role in the treatment of hormone receptor-positive breast cancer for many years. To better determine which patient subsets need adjuvant chemotherapy, various gene expression analyses have been developed, but cost-effective tools to identify such patients remain elusive. In the present report, we retrospectively investigated immunohistochemical expression and subcellular localization of MUC1 in primary tumors and examined their relationship to tumor malignancy, chemotherapy effect and patient outcomes. We retrospectively examined three patient cohorts with hormone receptor-positive/human epidermal growth factor receptor 2-negative invasive breast cancer: 51 patients who underwent 21-gene expression analysis (multi-gene assay-cohort), 96 patients who received neoadjuvant chemotherapy (neoadjuvant chemotherapy-cohort), and 609 patients whose tumor tissue was used in tissue-microarrays (tissue-microarray-cohort). The immunohistochemical staining pattern of the anti-MUC1 monoclonal antibody, Ma695, was examined in cancer tissues, and subcellular localization was determined as apical, cytoplasmic or negative. In the multi-gene assay-cohort, tumors with apical patterns had the lowest recurrence scores, reflecting lower tumor malignancy, and were significantly lower than MUC1-negative tumors (P = 0.038). In the neoadjuvant chemotherapy-cohort, there was no correlation between MUC1 staining patterns and effects of chemotherapy. Finally, in the tissue-microarray-cohort, we found that patients with apical MUC1 staining patterns had significantly longer disease-free-survival and overall survival than other patterns (P = 0.020 and 0.039, respectively). Our data suggest that an apical MUC1 staining pattern indicates luminal A-likeness. Assessment of the subcellular localization of MUC1 glycoprotein may be useful for identifying patients who can avoid adjuvant chemotherapy.

Prevention of Inflammation-Driven Colon Carcinogenesis in Human MUC1 Transgenic Mice by Vaccination with MUC1 DNA and Dendritic Cells

The preventive efficacy of MUC1-specific DNA immunization on inflammation-driven colon carcinogenesis in human MUC1 transgenic (MUC1.Tg) mice was investigated. Mice were vaccinated with MUC1 DNA mixed with autologous bone-marrow-derived dendritic cells (BMDCs), and then colonic tumors were induced by azoxymethane (AOM) injection and oral administration of dextran sulfate sodium (DSS). Two types of tumors, squamous metaplasia and tubular adenoma, were observed. Both expressed high levels of MUC1 as indicated by the binding of anti-MUC1 antibodies with different specificities, whereas MUC1 expression was not detected in normal colonic mucosa. When mice were immunized with MUC1 DNA + BMDCs, tumor incidence, tumor number, and tumor size were significantly reduced. In contrast, vaccination with MUC1 DNA alone or BMDCs alone was ineffective in reducing tumor burden. Inflammation caused by DSS was not suppressed by the MUC1 DNA + BMDCs vaccination. Furthermore, MUC1 protein expression levels, as judged by anti-MUC1 antibody binding in tumors grown after vaccination, did not significantly differ from the control. In conclusion, an inflammation-driven carcinogenesis model was established in MUC1.Tg mice, closely resembling human colon carcinogenesis. In this model, vaccination with MUC1 DNA + BMDCs was effective in overriding MUC1 tolerance and reducing the tumor burden by a mechanism not affecting the level of colonic inflammation.

Structural and molecular insight into antibody recognition of dynamic neoepitopes in membrane tethered MUC1 of pancreatic cancer cells and secreted exosomes.

Pancreatic cancer is highly metastatic and has poor prognosis, mainly due to delayed detection, often after metastasis has occurred. A novel method to enable early detection and disease intervention is strongly needed. Here we unveil for the first time that pancreatic cancer cells (PANC-1) and secreted exosomes express MUC1 bearing cancer-relevant dynamic epitopes recognized specifically by an anti-MUC1 antibody (SN-131), which binds specifically core 1 but not core 2 type O-glycans found in normal cells. Comprehensive assessment of the essential epitope for SN-131 indicates that PANC-1 cells produce dominantly MUC1 with aberrant O-glycoforms such as Tn, T, and sialyl T (ST) antigens. Importantly, SN-131 showed the highest affinity with MUC1 bearing ST antigen at the immunodominant DTR motif (KD = 1.58 nM) independent of the glycosylation states of other Ser/Thr residues in the MUC1 tandem repeats. The X-ray structure revealed that SN-131 interacts directly with Neu5Ac and root GalNAc of the ST antigen in addition to the proximal peptide region. Our results demonstrate that targeting O-glycosylated "dynamic neoepitopes" found in the membrane-tethered MUC1 is a promising therapeutic strategy for improving the treatment outcome of patients with pancreatic cancer.

Preliminary Development and Testing of C595 Radioimmunoconjugates for Targeting MUC1 Cancer Epitopes in Pancreatic Ductal Adenocarcinoma.

Mucin 1 is a transmembrane glycoprotein which overexpresses cancer-specific epitopes (MUC1-CE) on pancreatic ductal adenocarcinoma (PDAC) cells. As PDAC is a low survival and highly aggressive malignancy, developing radioimmunoconjugates capable of targeting MUC1-CE could lead to improvements in PDAC outcomes. The aim of this study was to develop and perform preliminary testing of diagnostic and therapeutic radioimmunoconjugates for PDAC using an anti-MUC1 antibody, C595. Firstly, p-SCN-Bn-DOTA was conjugated to the C595 antibody to form a DOTA-C595 immunoconjugate. The stability and binding affinity of the DOTA-C595 conjugate was evaluated using mass spectrometry and ELISA. DOTA-C595 was radiolabelled to Copper-64, Lutetium-177, Gallium-68 and Technetium-99m to form novel radioimmunoconjugates. Cell binding assays were performed in PANC-1 (strong MUC1-CE expression) and AsPC-1 (weak MUC1-CE expression) cell lines using 64Cu-DOTA-C595 and 177Lu-DOTA-C595. An optimal molar ratio of 4:1 DOTA groups per C595 molecule was obtained from the conjugation process. DOTA-C595 labelled to Copper-64, Lutetium-177, and Technetium-99m with high efficiency, although the Gallium-68 labelling was low. 177Lu-DOTA-C595 demonstrated high cellular binding to the PANC-1 cell lines which was significantly greater than AsPC-1 binding at concentrations exceeding 100 nM (p < 0.05). 64Cu-DOTA-C595 showed similar binding to the PANC-1 and AsPC-1 cells with no significant differences observed between cell lines (p > 0.05). The high cellular binding of 177Lu-DOTA-C595 to MUC1-CE positive cell lines suggests promise as a therapeutic radioimmunoconjugate against PDAC while further work is required to harness the potential of 64Cu-DOTA-C595 as a diagnostic radioimmunoconjugate.

Tumour-associated Mucin1 correlates with the procoagulant properties of cancer cells of epithelial origin

BackgroundCancer-associated thrombosis (CAT) is caused, at least in part, by procoagulant factors produced by the tumour itself. Although MUC1 is an established biomarker for the diagnosis, immunotherapy, and prognosis of cancer, it is unclear whether it contributes to the procoagulant phenotype of cancer cells. MethodsMUC1 knockdown breast cancer MCF-7 cells were used to investigate the influence of overexpression of MUC1 on procoagulant parameters. In addition, the effect of treating normal human epithelial cells with extracellular vesicles from several human breast and pancreatic cancer cell lines, which overexpress MUC1, was determined. The impact of a pharmacological anti-MUC1 antibody on cancer cells was also analysed. ResultsThe level of a range of procoagulant proteins was observed to correlate with the MUC1 level of human breast and pancreatic cancer cell lines. MUC1 downregulation in MCF-7 cells led to a reduction in the procoagulant parameters particularly thrombin activity. The levels of selected tumorigenic markers, procoagulant proteins and miRNAs associated with tumorigenicity and thromboembolism were also modulated by treatment of normal cells with tumour cell derived extracellular vesicles in correlation with that of the extracellular vesicles donor cells. Moreover, the procoagulant properties were also reduced by an anti-MUC1 antibody in these cancer cells. ConclusionsA range of procoagulant proteins found in human breast and pancreatic cancer cells were shown to exhibit a positive correlation with the level of MUC1 and thereby potentially contribute to the pathogenesis of CAT. The reduction of the procoagulant activity by MUC1 antibody could be an additional beneficial effect of its therapeutic efficacy. These findings also suggest that the level of tumour associated MUC1 could be of use as a risk factor for CAT.

Comparative study on the antitumor effects of gemcitabine polybutylcyanoacrylate nanoparticles coupled with anti-human MUC1 and CA199 monoclonal antibodies on pancreatic cancer in vitro and in vivo

Background and Study AimsThis study was designed to compare the antitumor effects of anti-human MUC1 monoclonal antibody with those of anti-human CA199 monoclonal antibody coupled with drug-loaded polybutylcyanoacrylate nanoparticles on human pancreatic cancer cell lines and pancreatic cancer-bearing model animals and to screen more efficient targeting molecules. Patients and MethodsGemcitabine-loaded nanospheres were prepared by emulsion polymerization (GEM-PBCA-NP), and then, anti-MUC1 monoclonal antibody was coupled with GEM-PBCA-NP (MUC1-GEM-PBCA-NP), and anti-human CA199 monoclonal antibody was coupled with GEM-PBCA-NP (CA199-GEM-PBCA-NP), using the chemical crosslinking method. The cell-killing rates were detected using MTT assay. The changes in the tumor cell cycle and apoptosis after treatment were detected using flow cytometry. Then, the subcutaneous planting method was adopted to establish an animal model of pancreatic cancer: two nanometer microspheres were injected into the body of nude mice via the tail vein; the tumor suppression effect was detected after treatment; then, the groups were compared. ResultsIn vitro, the cell-killing rate of each experimental group was significantly different from that of the control group (P < 05). The MUC1-GEM-PBCA-NP group had a significantly higher cell-killing rate than the other groups (P < 05). The apoptosis rate of the MUC1-GEM-PBCA-NP treatment group was significantly higher than that of other groups (P < 05). In vivo, the tumor inhibition rate of the MUC1-GEM-PBCA-NP treatment group was 72.69% ± 4.29%, which was significantly higher than those of other groups (P < 0.05). The tumor inhibition rate of the CA199-GEM-PBCA-NP treatment group was 56.58% ± 5.11%, which was significantly higher than those of other control groups (P < 0.05). At the end of treatment, the average tumor mass of the MUC1-GEM-PBCA-NP treatment group was 433.55 ± 12.49 mg, which was significantly lower than those of other groups (P < 0.05). ConclusionCompared with CA199-GEM-PBCA-NP, MUC1-GEM-PBCA-NP is more effective in vitro and in vivo. MUC1 could be a target molecule in treating pancreatic cancer.

O-Glycan-Dependent Interaction between MUC1 Glycopeptide and MY.1E12 Antibody by NMR, Molecular Dynamics and Docking Simulations.

Anti-mucin1 (MUC1) antibodies have been widely used for breast cancer diagnosis and treatment. This is based on the fact that MUC1 undergoes aberrant glycosylation upon cancer progression, and anti-MUC1 antibodies differentiate changes in glycan structure. MY.1E12 is a promising anti-MUC1 antibody with a distinct specificity toward MUC1 modified with an immature O-glycan (NeuAcα(2-3)Galβ(1-3)GalNAc) on a specific Thr. However, the structural basis for the interaction between MY.1E12 and MUC1 remains unclear. The aim of this study is to elucidate the mode of interaction between MY.1E12 and MUC1 O-glycopeptide by NMR, molecular dynamics (MD) and docking simulations. NMR titration using MUC1 O-glycopeptides suggests that the epitope is located within the O-linked glycan and near the O-glycosylation site. MD simulations of MUC1 glycopeptide showed that the O-glycosylation significantly limits the flexibility of the peptide backbone and side chain of the O-glycosylated Thr. Docking simulations using modeled MY.1E12 Fv and MUC1 O-glycopeptide, suggest that VH mainly contributes to the recognition of the MUC1 peptide portion while VL mainly binds to the O-glycan part. The VH/VL-shared recognition mode of this antibody may be used as a template for the rational design and development of anti-glycopeptide antibodies.

P16. BREAST IMPLANTS AND BREAST CANCER IMMUNOSURVEILLANCE: AN UPDATED AND LONGITUDINAL ANALYSIS OF ANTIBODY RESPONSES TO BREAST CANCER ANTIGEN POST IMPLANT PLACEMENT

PURPOSE: We previously demonstrated women with breast implants have higher antibody responses to select breast cancer proteins compared to women with no implant exposure. Here, we present antibody response data on a larger cohort of women and with a longer follow-up period. METHODS: Sera was collected from 34 patients prior to and one-month after breast augmentation surgery, as well as six months after surgery in 10 patients. Antibody responses to breast cancer proteins were tested via ELISA assay. Pre- and post-implant responses were compared with paired t-test using Graphpad Prism v9.1.2. RESULTS: Average age was 31.6 years (SD 8.2 years) and average BMI 24.1 (SD 5.1). Twenty-nine patients (85.3%) received silicone and all received smooth implants. At one month post-implant placement, anti-MUC1 antibody levels were significantly increased (n=34, mean difference 0.065, p= 0.0002). At six-months post-implant placement, antibody response was significantly increased for MUC-1 (n=9, mean difference 0.051, p=0.015), ER (n=9, mean difference 0.124, p=0.0015), BRCA2 (n=10, mean difference 0.076, p=0.045), HER-2 (n=10, mean difference 0.154, p=0.031), and BRCA1 (n=9, mean difference 0.225, p=0.015). There was no difference in post-implant (one-month and six-month) antibody responses to tetanus, CEA, MMP11, and HER-3. Confirmatory studies show elevated presence of B cells in peri-implant breast tissue compared to implant naïve breast tissue. CONCLUSION: Women with cosmetic breast implants have elevated antibody responses to common breast cancer proteins as early as one month post implant placement, and sustained at six months. Further studies will elucidate the immunologic mechanism for this potential cancer surveillance role.

Alum Adjuvant and Built-in TLR7 Agonist Synergistically Enhance Anti-MUC1 Immune Responses for Cancer Vaccine.

The tumor-associated antigen mucin 1 (MUC1) is an attractive target of antitumor vaccine, but its weak immunogenicity is a big challenge for the development of vaccine. In order to enhance immune responses against MUC1, herein, we conjugated small molecular toll-like receptor 7 agonist (TLR7a) to carrier protein BSA via MUC1 glycopeptide to form a three-component conjugate (BSA-MUC1-TLR7a). Furthermore, we combined the three-component conjugate with Alum adjuvant to explore their synergistic effects. The immunological studies indicated that Alum adjuvant and built-in TLR7a synergistically enhanced anti-MUC1 antibody responses and showed Th1-biased immune responses. Meanwhile, antibodies elicited by the vaccine candidate effectively recognized tumor cells and induced complement-dependent cytotoxicity. In addition, Alum adjuvant and built-in TLR7a synergistically enhanced MUC1 glycopeptide-specific memory CD8+ T-cell immune responses. More importantly, the vaccine with the binary adjuvant can significantly inhibit tumor growth and prolong the survival time of mice in the tumor challenge experiment. This novel vaccine construct provides an effective strategy to develop antitumor vaccines.

Anti-cancer effects of pyrazole-platinum(II) complexes combined with anti-MUC1 monoclonal antibody versus monotherapy in DLD-1 and HT-29 colon cancer cells

The membrane-bound MUC1 mucin is overexpressed and aberrantly glycosylated in many epithelium origin cancers. One of the promising strategies in cancer therapy is combining monoclonal antibodies against cancer related antigens, like MUC1, with chemotherapeutics. In the study we evaluated the potency of cisplatin (cisPt), two pyrazole-platinum(II) complexes PtPz4, PtPz6, and anti-MUC1 mAb applied as monotherapy, as well as the chemotherapeutics administrated with antibody, towards apoptotic response and cancer-related carbohydrate antigens (TACAs) in DLD-1 and HT-29 colon cancer cells. To assess the impact of the tested compounds on the examined factors flow cytometry, RT-PCR, Western blotting and ELISA were utilized. The combined therapy was more potent than monotherapy towards Bcl-2, Bid, caspases and TACAs of both cell lines. Combined therapy applied in DLD-1 cells induced apoptosis, was more effective than monotherapy in relation to p53, Bcl-xL, Bax, and Bim. In HT-29 cells, anti-MUC1 administrated with the drugs was more potent than monotherapy towards Bad. The proposed anti-MUC1/cisPt and pyrazole-platinum(II) complexes PtPz4, PtPz6 combined therapy may be promising anti-colon cancer therapy.

Mucin 1 as a Molecular Target of a Novel Diisoquinoline Derivative Combined with Anti-MUC1 Antibody in AGS Gastric Cancer Cells

Background: The aim of the study was to examine the molecular mechanism of the anticancer action of a monoclonal antibody against MUC1 and a diisoquinoline derivative (OM-86II) in human gastric cancer cells. Methods: The cell viability was measured by the MTT assay. The disruption of mitochondrial membrane potential and activity of caspase-8 and caspase-9 was performed by flow cytometry. Fluorescent microscopy was used to confirm the proapoptotic effect of compounds. LC3A, LC3B and Beclin-1 concentrations were analyzed to check the influence of the compounds on induction of autophagy. ELISA assessments were performed to measure the concentration of mTOR, sICAM1, MMP-2, MMP-9 and pro-apoptotic Bax. Results: The anti-MUC1 antibody with the diisoquinoline derivative (OM-86II) significantly reduced gastric cancer cells’ viability. This was accompanied by an increase in caspase-8 and caspase-9 activity as well as high concentrations of pro-apoptotic Bax. We also proved that the anti-MUC1 antibody with OM-86II decreased the concentrations of MMP-9, sICAM1 and mTOR in gastric cancer cells. After 48 h of incubation with such a combination, we observed higher levels of the crucial component of autophagosomes (LC3) and Beclin-1. Conclusions: Our study proved that the anti-MUC1 antibody sensitizes human gastric cancer cells to the novel diisoquinoline derivative (OM-86II) via induction of apoptosis and autophagy, and inhibition of selected proteins such as mTOR, sICAM1 and MMP-9.

Abstract 3045: Investigating the influence of glycosylation using cellular models of neuroblastoma

Abstract Background: Neuroblastoma is a common childhood malignancy with approximately 800 new cases diagnosed each year in the United States. Treatment of neuroblastoma directly depends on patient risk categories and includes combinations of surgery, radiation therapy, chemotherapy, stem cell therapy, immunotherapy, and retinoid therapy. Various characteristics of cancer in general and some specific to neuroblastoma cell lines contribute to a difficulty in delivering clinically relevant concentrations of therapeutic agents to neuroblastoma masses. Amplification of the MYCN gene in certain neuroblastoma cell lines correlates with increased cellular surface glycosylation levels as well as a worse prognosis for patients. Overexpression of the MUC1 gene is also associated with increased glycosylation, specifically type-O, in various cancers, but the role of MUC1 in neuroblastoma has not been thoroughly defined. The objective of this study was to evaluate the influence of type-O glycosylation on therapeutic uptake in different neuroblastoma cell lines. Methods: The neuroblastoma cell line SK-N-DZ, a MYCN-amplified line, was compared to SK-N-SH, a non-MYCN-amplified line (negative control) and BT-20, a highly glycosylated breast cancer cell line (positive control). Benzyl-α-GalNAc, an O-glycosylation inhibitor, was introduced to each cell line. To determine glycosylation levels in the respective cell lines, fluorescence assays were performed using CD227 (anti-MUC1) antibody. In vitro cytotoxicity assays were performed to determine maximum non-toxic concentrations of the glycosylation inhibitor (benzyl-α-GalNAc) and antibody (CD227) and to subsequently evaluate the functional role of glycosylation using cellular models of neuroblastoma. Results: The maximum non-toxic concentrations per 10,000 cells for each neuroblastoma cell line was 0.05 mg/ml of benzyl-α-GalNAc, and 6 µl of CD227 stock preparation. Preliminary results from fluorescence detection studies showed an increase in CD227-FITC antibody uptake by the MYCN-amplified neuroblastoma cells (SK-N-DZ) following exposure to the O-glycosylation inhibitor (benzyl-α-GalNAc). Cellular uptake of CD227-FITC by non-MYCN-amplified cell line (SK-N-SH) was less by comparison. Conclusion: Preliminary findings suggest that O-glycosylation is a barrier capable of limiting cellular uptake of agents in MYCN-amplified neuroblastoma cell lines. Ongoing studies are focused on investigating the influence of glycosylation inhibition on cytotoxicity of FDA-approved therapeutic agents. Citation Format: Meghan Cook, Alma Garcia, Katie Konieczny, Meghan Ferguson, Robert Campbell. Investigating the influence of glycosylation using cellular models of neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3045.

Defucosylation of Tumor-Specific Humanized Anti-MUC1 Monoclonal Antibody Enhances NK Cell-Mediated Anti-Tumor Cell Cytotoxicity.

Simple SummaryAntibodies with their high specificity to antigens have been widely used in cancer immunotherapy. Natural killer (NK) cells are a group of innate immune cells which have strong cytotoxicity against cancerous cells, virus infected cells, or transformed cells. NK cells express abundant Fc receptors that can bind tumor-specific antibodies, thus allowing them to precisely redirect and eliminate cancer cells. In this study, we demonstrated that NK cells cytotoxicity toward MUC1-positive hematologic and solid tumor can be further enhanced by a humanized 5E5 anti-MUC1 antibody. Furthermore, Fc defucosylation of the antibodies further boosted the kill capacity of NK cells. We believe that our humanized anti-MUC1 antibody is a promising therapeutic candidate for clinical cancer treatment.Antibodies are commonly used in cancer immunotherapy because of their high specificity for tumor-associated antigens. The binding of antibodies can have direct effects on tumor cells but also engages natural killer (NK) cells via their Fc receptor. Mucin 1 (MUC1) is a highly glycosylated protein expressed in normal epithelial cells, while the under-glycosylated MUC1 epitope (MUC1-Tn/STn) is only expressed on malignant cells, making it an interesting diagnostic and therapeutic target. Several anti-MUC1 antibodies have been tested for therapeutic applications in solid tumors thus far without clinical success. Herein, we describe the generation of fully humanized antibodies based on the murine 5E5 antibody, targeting the tumor-specific MUC1-Tn/STn epitope. We confirmed that these antibodies specifically recognize tumor-associated MUC1 epitopes and can activate human NK cells in vitro. Defucosylation of these newly developed anti-MUC1 antibodies further enhanced antigen-dependent cellular cytotoxicity (ADCC) mediated by NK cells. We show that endocytosis inhibitors augment the availability of MUC1-Tn/STn epitopes on tumor cells but do not further enhance ADCC in NK cells. Collectively, this study describes novel fully humanized anti-MUC1 antibodies that, especially after defucosylation, are promising therapeutic candidates for cellular immunotherapy.

The surface dominant antigen MUC1 is required for colorectal cancer stem cell vaccine to exert anti-tumor efficacy

Colorectal cancer (CRC), initiated and maintained by colorectal cancer stem cells (CCSCs), ranks the third most common cancers and has drawn wide attentions worldwide. Therefore, targeting clearance of CCSCs has become an important strategy of CRC immunotherapy. Mucin1 (MUC1) is a tumor-associated cell surface antigen of CRC, but its role in CCSC vaccine remains unclear. In the study, we demonstrated that MUC1 may be a dominant antigen to exert antitumor immunity in CCSC vaccine. First, CCSCs were enriched from CT26 cell line via a serum-free sphere formation approach, and were identified by detecting expression of CD133, ALDH, and ALCAM. Then, the isolated CCSCs were frozen for 30 min and thawed for 30 min to prepare the cell lysate. The specific anti-MUC1 antibody was added to the cell lysate to neutralize the dominant antigen MUC1. Finally, mice were subcutaneously immunized with the cell lysate, followed by a challenge with CT26 cells at one week after final vaccination. Attractively, CCSC vaccine significantly activated the NK cells, T cells, and B cells, resulting in inhibiting the tumor growth via a target killing of CCSCs as evidenced by a decrease of CD133+cells in tumor compared to CCSC vaccine with specific anti-MUC1 antibody. In addition, CCSC vaccine reduced expression of inflammatory factors in vaccinated mice. As expected, neutralizing antibody against MUC1 significantly impaired the antitumor efficacy of CCSC vaccine. Overall, CCSC vaccine could serve as a potent vaccine for CRC immunotherapy. The surface dominant antigen MUC1 may play a key role in regulating immunogenicity of CCSCs.

In vivo anti-MUC1+ tumor activity and sequences of high-affinity anti-MUC1-SEA antibodies.

Cleavage of the MUC1 glycoprotein yields two subunits, an extracellular alpha-subunit bound to a smaller transmembrane beta-subunit. Monoclonal antibodies (mAbs) directed against the MUC1 alpha-beta junction comprising the SEA domain, a stable cell-surface moiety, were generated. Sequencing of all seven anti-SEA domain mAbs showed that they clustered into four groups and sequences of all groups are presented here. mAb DMB5F3 with picomolar affinity for the MUC1 SEA target was selected for further evaluation. Immunohistochemical staining of a series of malignancies with DMB5F3 including lung, prostate, breast, colon, and pancreatic carcinomas revealed qualitative and qualitative differences between MUC1 expression on normal versus malignant cells: DMB5F3 strongly stained malignant cells in a near-circumferential pattern, whereas MUC1 in normal pancreatic and breast tissue showed only weak apical positivity of ductal/acinar cells. Humanized chimeric DMB5F3 linked to ZZ-PE38 (ZZ IgG-binding protein fused to Pseudomonas exotoxin) induced vigorous cytotoxicity of MUC1+ malignant cells in vitro. The intensity of cell killing correlated with the level of MUC1 expression by the target cell, suggesting a MUC1 expression threshold for cell killing. MUC1+ Colo357 pancreatic cancer cells xenotransplanted into nude and SCID mice models were treated with the chDMB5F3:ZZ-PE38 immunocomplex. In both transplant models, chDMB5F3:ZZ-PE38 exhibited significant in vivo anti-tumor activity, suppressing up to 90% of tumor volume in the SCID model compared with concomitant controls. The efficacy of chDMB5F3:ZZ-PE38 immunotoxin in mediating tumor killing both in vitro and in vivo strongly suggests a clinical role for anti-MUC1 SEA antibody in the treatment of MUC1-expressing malignancies.