Citations

Abstract Dendritic cells (DC) are potent APCs. In this study, murine bone marrow-derived DC were transfected with RNA encoding the MUC1 Ag that is aberrantly overexpressed in human breast and other carcinomas. The MUC1 RNA-transfected DC exhibited cell surface expression of MUC1 and costimulatory molecules. After injection at the base of the tail, the transfected DC were detectable in inguinal lymph nodes by dual immunochemical staining. Vaccination of wild-type mice with MUC1 RNA-transfected DC induced anti-MUC1 immune responses against MUC1-positive MC38/MUC1, but not MUC1-negative, tumor cells. Mice immunized with the transfected DC were protected against challenge with MC38/MUC1 tumor cells. Furthermore, mice with established MC38/MUC1 tumors were eliminated after receiving the vaccination. CTLs isolated from mice immunized with the transfected DC exhibited specific cytolytic activity against MC38/MUC1 tumor cells. In contrast to these findings, there was little if any anti-MUC1 immunity induced with the transfected DC in MUC1 transgenic (MUC1.Tg) mice. However, coadministration of the transfected DC and IL-12 reversed the unresponsiveness to MUC1 Ag in MUC1.Tg mice and induced MUC1-specific immune responses. These findings demonstrate that vaccination of DC transfected with MUC1 RNA and IL-12 reverses tolerance to MUC1 and induces immunity against MUC1-positive tumors.

Abstract Genetically modified mice with spontaneous development of mammary carcinoma provide a powerful tool to study the efficacy of tumor vaccines, since they mimic breast cancer development in humans. We used a transgenic murine model expressing polyomavirus middle T oncogene and mucin 1 tumor-associated Ag to determine the preventive effect of a dendritic/tumor fusion cell vaccine. The MMT (a transgenic murine model) mice developed mammary carcinoma between the ages of 65–108 days with 100% penetrance. No spontaneous CTL were detected. However, prophylactic vaccination of MMT mice with dendritic/tumor fusion cells induced polyclonal CTL activity against spontaneous mammary carcinoma cells and rendered 57–61% of the mice free of the disease at the end of experiment (180 days). Furthermore, the level of CTL activity was maintained with multiple vaccinations. The antitumor immunity induced by vaccination with dendritic/tumor fusion cells reacted differently to injected tumor cells and autochthonous tumor. Whereas the injected tumor cells were rejected, the autochthonous tumor evaded the attack and was allowed to grow. Collectively these results indicate that prophylactic vaccination with dendritic/tumor fusion cells confers sufficient antitumor immunity to counter the tumorigenesis of potent oncogenic products. The findings in the present study are highly relevant to cancers in humans.

Abstract MUC1 (MUC1 in human and Muc1 in nonhumans) is a membrane-tethered mucin that interacts with Pseudomonas aeruginosa (PA) through flagellin. In this study, we compared PA pulmonary clearance and proinflammatory responses by Muc1−/− mice with Muc1+/+ littermates following intranasal instillation of PA or flagellin. Compared with Muc1+/+ mice, Muc1−/− mice showed increased PA clearance, greater airway recruitment of neutrophils, higher levels of TNF-α and KC in bronchoalveolar lavage fluid, higher levels of TNF-α in media of flagellin-stimulated alveolar macrophages, and higher levels of KC in media of tracheal epithelial cells. Knockdown of MUC1 enhanced flagellin-induced IL-8 production by primary human bronchial epithelial cells. Expression of MUC1 in HEK293T cells attenuated TLR5-dependent IL-8 release in response to flagellin, which was completely ablated when its cytoplasmic tail was deleted. We conclude that MUC1/Muc1 suppresses pulmonary innate immunity and speculate its anti-inflammatory activity may play an important modulatory role during microbial infection.

Abstract Pancreatic cancer is a highly aggressive, treatment refractory cancer and is the fourth leading cause of death in the United States. In humans, 90% of pancreatic adenocarcinomas overexpress altered forms of a tumor-specific Ag, mucin 1 (MUC1; an epithelial mucin glycoprotein), which is a potential target for immunotherapy. We have established a clinically relevant animal model for pancreatic cancer by developing a double transgenic mouse model (called MET) that expresses human MUC1 as self molecule and develops spontaneous tumors of the pancreas. These mice exhibit acinar cell dysplasia at birth, which progresses to microadenomas and acinar cell carcinomas. The tumors express large amounts of underglycosylated MUC1 similar to humans. Tumor-bearing MET mice develop low affinity MUC1-specific CTLs that have no effect on the spontaneously occurring pancreatic tumors in vivo. However, adoptive transfer of these CTLs was able to completely eradicate MUC1-expressing injectable tumors in MUC1 transgenic mice, and these mice developed long-term immunity. These CTLs were MHC class I restricted and recognized peptide epitopes in the immunodominant tandem repeat region of MUC1. The MET mice appropriately mimic the human condition and are an excellent model with which to elucidate the native immune responses that develop during tumor progression and to develop effective antitumor vaccine strategies.

Abstract Purpose: MUC1 is a tumor-associated antigen that is aberrantly expressed in cancer and inflammatory bowel disease (IBD). Even though immune cells express low MUC1 levels, their modulations of MUC1 are important in tumor progression. Consistent with previous clinical data that show increased myeloid-derived suppressor cells (MDSCs) in IBD, we now show that downregulation of MUC1 on hematopoietic cells increases MDSCs in IBD, similar to our data in tumor-bearing mice. We hypothesize that MDSC expansion in IBD is critical for tumor progression. Experimental Design: To mechanistically confirm the linkage between Muc1 downregulation and MDSC expansion, we generated chimeric mice that did not express Muc1 in the hematopoietic compartment (KO→WT). These mice were used in two models of colitis and colitis-associated cancer (CAC) and their responses were compared with wild-type (WT) chimeras (WT→WT). Results: KO→WT mice show increased levels of MDSCs during colitis and increased protumorigenic signaling in the colon during CAC, resulting in larger colon tumors. RNA and protein analysis show increased upregulation of metalloproteinases, collagenases, defensins, complements, growth factors, cytokines, and chemokines in KO→WT mice as compared with WT→WT mice. Antibody-mediated depletion of MDSCs in mice during colitis reduced colon tumor formation during CAC. Conclusion: Development of CAC is a serious complication of colitis and our data highlight MDSCs as a targetable link between inflammation and cancer. In addition, the lack of MUC1 expression on MDSCs can be a novel marker for MDSCs, given that MDSCs are still not well characterized in human cancers. Clin Cancer Res; 19(18); 5039–52. ©2013 AACR.

Abstract A previous lectin binding study demonstrated the presence of high molecular-mass mucin-like glycoproteins (HMGP) on the surface of hamster tracheal surface epithelial (HTSE) secretory cells (Proc. Natl. Acad. Sci. USA 1987;84:9304). In the present study, we intended to isolate and characterize these HMGP from the plasma membrane of the primary HTSE cells and then to determine whether or not these membrane HMGP are Muc-1 mucins, a type of mucins originally discovered on the surface of some carcinomas. A subcellular fraction enriched with the plasma membrane was obtained using a sucrose density gradient centrifugation. This fraction contained high molecular-mass glycoconjugates which were excluded from Sepharose CL-4B gel. Biochemical characterization of these glycoconjugates revealed the following characteristics: (1) susceptibility to both pronase and mild alkaline treatments, but totally resistant to proteoglycan-digesting enzymes; (2) partitioning in the detergent phase of Triton X-114 and resistance to digestion by phosphatidylinositol phospholipase C or D; (3) a buoyant density of 1.5 g/ml based on CsCl density gradient centrifugation; (4) polydispersity in terms of both size and charge density; and (5) lack of immunoreactivity with an anti-Muc-1 mucin antibody. We conclude that the plasma membrane of HTSE cells at confluence contains HMGP, which seem to be the integral membrane proteins but different from Muc-1 mucins, and that these membrane HMGP appear to share some similarities with secreted mucins in terms of size and charge.

Abstract MUC1 is over expressed and aberrantly glycosolated in >60% of pancreatic ductal adenocarcinomas. Over expression of MUC1 in pancreatic cancer is known, however the functional role has yet to be fully elucidated due to a dearth of appropriate models. In the present study, we have generated mouse models that spontaneously develop pancreatic ductal adenocarcinoma (KC), which are either Muc1 null (KCKO) or express human MUC1 as a self antigen (KCM). We show that PDA mice lacking Muc1 have significantly slower tumor progression, with tumor weight reaching up to a third of the KCM tumor and half of KC tumor. One out of 10 KCKO mice developed secondary metastasis versus 6 out of 10 and 3 out of 10 KCM and KC respectively. Cell lines derived from KCKO tumors have significantly lower tumorigenic capacity compared to cells derived from KCM tumors. Therefore, mice with KCKO tumors had a significant survival benefit compared to mice bearing the KCM tumors. In vitro, the KCKO cells have reduced proliferation and invasion compared to KCM cells and failed to respond to exogenous epidermal growth factor (EGF), platelet-derived growth factor (PDGF), or matrix metalloproteinase-9 (MMP9) stimuli. Further, significantly fewer KCKO cells entered the G2M phase of the cell cycle compared to the KCM cells, consequently more KCKO cells were observed at the S-phase of the cell cycle. Proteomics and western blotting analysis revealed a complete loss of cdc-25c expression, phosphorylation of MAPK, as well as a significant decrease in Nestin and Tubulin α-2 chain expression in KCKO cells. Treatment of the KCM cells with a MEK1/2 inhibitor, U0126, completely abrogated the enhanced proliferation of the KCM cells but had minimal effect on KCKO cells, strongly suggesting that MUC1 is necessary for MAPK activity and downstream oncogenic signaling. This is the first study to utilize a Muc1-null PDA mouse in order to fully elucidate the oncogenic role of MUC1, both in vivo and in vitro. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1070. doi:10.1158/1538-7445.AM2011-1070

Abstract Introduction: Pancreatic cancer is the fourth leading cause of cancer-related death in United States. Most human pancreatic cancers overexpress MUC1, which is associated with high metastasis and poor prognosis of the disease. We have recently shown that MUC1 initiates the process of epithelial to mesenchymal transition (EMT) and promotes metastasis in pancreatic cancer cells via signaling through the seven tyrosines present in its cytoplasmic tail (CT) motif. When the 7 tyrosines were mutated to phenylalanine, EMT was completely abrogated. Since TGF-β has been extensively studied as a mediator of EMT and invasion in pancreatic cancer, we hypothesized that MUC1 may be inducing its effect through regulating TGF-β production and signaling. We also aimed at identifying the specific tyrosine residue(s) responsible for MUC1 induced EMT. Method: We made the following plasmids containing a) full length MUC1 (MUC1), b) all 7 tyrosine residues of MUC1 CT were mutated to Phenylalanine (Y0), c) Y6 (Tyrosine 6 present, the rest replaced by Phenylalanine), d) Y7 (Tyrosine 7 present, the rest replaced by Phenylalanine), e) Y2,5 (Tyrosine 2 and 5 present, the rest replaced by Phenylalanine), f) Y3,6,7 (Tyrosine3, 6 and 7 present, the rest replaced by Phenylalanine) and g) empty vector (Neo). These plasmids were stably expressed in human pancreatic cancer cell lines, BxPC3 and Su86.86 that express low levels of endogenous MUC1. We first assessed the levels of functional TGF-β secreted by BxPC3 Neo, MUC1 and Y0 cells as well as the levels of TGF-βI and II receptors. We then treated these cells with exogenous human recombinant TGF-β and assessed both, the process of EMT and the capacity to invade through growth-reduced matrigel. Results: We found that BxPC3.MUC1 cells produced strikingly larger amounts of TGF-β compared to BxPC3 Neo and Y0 cells. We also found that MUC1-expressing cells became more invasive in response to exogenous TGF-β while the Y0 cells did not respond to exogenous TGF-β although the receptor levels were similar in all three cell lines. However, none of the mutants of MUC1 CT could rescue the function of full length MUC1, in the context of induction of EMT. Conclusion: 1) We believe that TGF-β mediated EMT and TGF-β signal propagation requires the tyrosine residue of MUC1, which is evident from the data that mutating the tyrosine residues in MUC1CT abrogates TGF-β mediated EMT in these cells. 2) Induction of EMT by MUC1 is a complex process, which involves a particular combination of tyrosine residues of MUC1. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2910. doi:10.1158/1538-7445.AM2011-2910

The mucin MUC1 is typically aberrantly glycosylated by epithelial cancer cells manifested by truncated O -linked saccharides. The resultant glycopeptide epitopes can bind cell surface major histocompatibility complex (MHC) molecules and are susceptible to recognition by cytotoxic T lymphocytes (CTLs), whereas aberrantly glycosylated MUC1 protein on the tumor cell surface can be bound by antibodies to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Efforts to elicit CTLs and IgG antibodies against cancer-expressed MUC1 have not been successful when nonglycosylated MUC1 sequences were used for vaccination, probably due to conformational dissimilarities. Immunizations with densely glycosylated MUC1 peptides have also been ineffective due to impaired susceptibility to antigen processing. Given the challenges to immuno-target tumor-associated MUC1, we have identified the minimum requirements to consistently induce CTLs and ADCC-mediating antibodies specific for the tumor form of MUC1 resulting in a therapeutic response in a mouse model of mammary cancer. The vaccine is composed of the immunoadjuvant Pam 3 CysSK 4 , a peptide T helper epitope and an aberrantly glycosylated MUC1 peptide. Covalent linkage of the three components was essential for maximum efficacy. The vaccine produced CTLs, which recognized both glycosylated and nonglycosylated peptides, whereas a similar nonglycosylated vaccine gave CTLs which recognized only nonglycosylated peptide. Antibodies elicited by the glycosylated tripartite vaccine were significantly more lytic compared with the unglycosylated control. As a result, immunization with the glycosylated tripartite vaccine was superior in tumor prevention. Besides its own aptness as a clinical target, these studies of MUC1 are likely predictive of a covalent linking strategy applicable to many additional tumor-associated antigens.