Gendler, Sandra

Abstract MUC1 is a heterodimeric transmembrane glycoprotein that is overexpressed and aberrantly glycosylated in ductal adenocarcinomas. Differential phosphorylation of the MUC1 cytoplasmic tail (MUC1CT) has been associated with signaling events that influence the proliferation and metastasis of cancer cells. We identified a novel tyrosine phosphorylation site (HGRYVPP) in the MUC1CT by mass spectrometric analysis of MUC1 from human pancreatic adenocarcinoma cell lines. Analyses in vitro and in vivo showed that platelet-derived growth factor receptor β (PDGFRβ) catalyzed phosphorylation of this site and of tyrosine in the RDTYHPM site. Stimulation of S2-013.MUC1F cells with PDGF-BB increased nuclear colocalization of MUC1CT and β-catenin. PDGF-BB stimulation had no significant effect on cell proliferation rate; however, it enhanced invasion in vitro through Matrigel and in vivo tumor growth and metastases. Invasive properties of the cells were significantly altered on expression of phosphorylation-abrogating or phosphorylation-mimicking mutations at these sites. We propose that interactions of MUC1 and PDGFRβ induce signal transduction events that influence the metastatic properties of pancreatic adenocarcinoma. [Cancer Res 2007;67(11):5201–10]

Abstract Much of the ability of the MUC1 oncoprotein to foster tumorigenesis and tumor progression likely originates from the interaction of its cytoplasmic tail with proteins involved in oncogenic signaling. Many of these interactions are regulated by phosphorylation, as the cytoplasmic tail contains seven highly conserved tyrosines and several serine/threonine phosphorylation sites. We have developed a cell line–based model system to study the effects of tyrosine phosphorylation on MUC1 signaling, with particular emphasis on its effects on gene transcription. COS-7 cells, which lack endogenous MUC1, were stably infected with wild-type MUC1 or a MUC1 construct lacking all seven tyrosines (MUC1 Y0) and analyzed for effects on transcription mediated by the extracellular signal-regulated kinase 1/2 (ERK1/2) and nuclear factor-κB (NF-κB) pathways. COS.MUC1 Y0 cells showed heightened active ERK1/2 with increased activator protein-1 (AP-1) and signal transducer and activator of transcription 3 (STAT3) transcriptional activity; there was also a simultaneous decrease in NF-κB transcriptional activity and nuclear localization. These changes altered the phenotype of COS.MUC1 Y0 cells, as this line displayed increased invasion and enhanced [3H]thymidine incorporation. Analysis of the three lines also showed significant differences in their cell cycle profile and bromodeoxyuridine incorporation when the cells were serum starved. These data support the growing evidence that MUC1 is involved in transcriptional regulation and link MUC1 for the first time to the NF-κB pathway. (Mol Cancer Res 2006;4(7):489–97)

Abstract In this review, we summarize work over the past 15 years on mucin gene expression and regulation in the lung, as well as how mucin gene expression is altered in chronic lung diseases. This field owes a great debt to Carol Basbaum for her pioneering work in dissecting signaling pathways regulating mucin gene expression and for her tremendous energy in promoting the importance of understanding the basic pathogenic mechanisms that drive mucus overproduction in cystic fibrosis, chronic obstructive pulmonary disease, and asthma.

Abstract Purpose: Expression of the sodium iodide symporter (NIS) in the thyroid gland provides for effective imaging and treatment of thyroid cancer using radiolabeled iodide. Transfer of NIS into other tumors would expand the utility of this treatment to tumors of nonthyroid origin. MUC1 is a transmembrane glycoprotein that is overexpressed in many tumor types, including breast, pancreatic, and ovarian. The aim of this study was to create a construct containing NIS under the control of the MUC1 promoter to target expression specifically to MUC1-positive breast cancer cells. Experimental Design: A replication-deficient adenoviral construct was created containing the MUC1 promoter followed by the human NIS gene. Iodide uptake assays, Western blot, and immunohistochemistry were used to confirm NIS expression and function. Breast cancer xenografts in mice were infected with Ad5/MUC1/NIS and then imaged and treated using radioiodide. Results: A 58-fold increase in iodide uptake was observed in infected MUC1-positive T47D cells with no significant increase observed in MUC1-negative MDA-MB-231 cells or in cells infected with the control virus. The in vivo study yielded clear images of Ad/MUC1/NIS-infected tumor xenografts using 123I. Administration of a therapeutic dose of 131I resulted in an 83% reduction in tumor volume, whereas control tumors continued to increase in size (P < 0.01). Conclusions: These results show that the MUC1 promoter is capable of directing efficient and selective expression of the NIS gene in MUC1-positive breast tumor cells. This could potentially have applications for both imaging and therapy in a range of MUC1-positive tumor types.

Here we examine the use of glycopeptides containing tumour‐associated carbohydrate antigens (TACA) as potential preventive vaccines for carcinomas. Our recent results suggest that CD8+ T cells (CTL) are capable of recognizing TACA in a conventional class I MHC‐restricted fashion. The Thomsen–Friedenreich antigen (TF), a disaccharide, and Tn, its immediate precursor, are TACA largely expressed in carcinomas. TF and Tn can be successfully used as Th‐independent vaccines when conjugated to designer peptides with optimal binding affinity for class I MHC molecules. TF‐ and Tn‐specific CTL generated using this strategy are capable of recognizing TACA‐expressing tumours in vitro, suggesting that glycopeptides are as effectively presented by class I MHC molecules as non‐glycosylated peptides. Because the exact sequences of endogenously synthesized glycopeptides are unknown, the TACA‐specific T cell repertoire elicited by carbohydrate‐based vaccines is assumed to be degenerate. Here we report that mice genetically manipulated to develop TACA‐expressing mammary tumours are not tolerant to glycopeptide vaccination. Moreover, we tested the immunogenicity of designer glycopeptides capable of binding multiple HLA alleles as a novel approach for the development of vaccines potentially useful for vaccination of a large fraction of the general population. Our results have suggested that CTL derived from normal donors respond with high efficiency to glycopeptides in vitro, opening a new avenue for the design of prospective vaccines for cancer prevention.

ABSTRACT Inefficient adenoviral vector (AdV)-mediated gene transfer to the ciliated respiratory epithelium has hindered gene transfer strategies for the treatment of cystic fibrosis lung disease. In part, the inefficiency is due to an absence of the coxsackie B and adenovirus type 2 and 5 receptor (CAR) from the apical membranes of polarized epithelia. In this study, using an in vitro model of human ciliated airway epithelium, we show that providing a glycosylphosphatidylinositol (GPI)-linked AdV receptor (GPI-CAR) at the apical surface did not significantly improve AdV gene transfer efficiency because the lumenal surface glycocalyx limited the access of AdV to apical GPI-CAR. The highly glycosylated tethered mucins were considered to be significant glycocalyx components that restricted AdV access because proteolytic digestion and inhibitors of O-linked glycosylation enhanced AdV gene transfer. To determine whether these in vitro observations are relevant to the in vivo situation, we generated transgenic mice expressing GPI-CAR at the surface of the airway epithelium, crossbred these mice with mice that were genetically devoid of tethered mucin type 1 (Muc1), and tested the efficiency of gene transfer to murine airways expressing apical GPI-human CAR (GPI-hCAR) in the presence and absence of Muc1. We determined that AdV gene transfer to the murine airway epithelium was inefficient even in GPI-hCAR transgenic mice but that the gene transfer efficiency improved in the absence of Muc1. However, the inability to achieve a high gene transfer efficiency, even in mice with a deletion of Muc1, suggested that other glycocalyx components, possibly other tethered mucin types, also provide a significant barrier to AdV interacting with the airway lumenal surface.

AbstractMUC1 (CD227) is a large transmembrane epithelial mucin glycoprotein, which is aberrantly overexpressed in most adenocarcinomas and is a target for immune therapy for epithelial tumors. Recently, MUC1 has beendetected in a variety of hematopoietic cell malignancies including T and B cell lymphomas and myelomas; however, its function in these cells is not clearly defined. Using the Jurkat T cell lymphoma cell line and normal human T cells, we demonstrate that MUC1 is not only expressed in these cells but is also phosphorylated upon T cell receptor (TCR) ligation and associates with the Src-related T cell tyrosine kinase, p56lck. Upon TCR-mediated activation of Jurkat cells, MUC1 is found in the low-density membrane fractions, where linker of T cell activation is contained. Abrogation of MUC1 expression in Jurkat cells by MUC1-specific small interfering RNA resulted in defects in TCR-mediated downstream signaling events associated with T cell activation. These include reduction in Ca2+ influx and extracellular signal-regulated kinase 1/2 phosphorylation, leading to a decrease in CD69 expression, proliferation, and interleukin-2 production. These results suggest a regulatory role of MUC1 in modulating proximal signal transduction events through its interaction with proteins of the activation complex.

Tumors express embryonic carbohydrate antigens called tumor-associated carbohydrate antigens (TACA). TACA-containing glycopeptides are appealing cytotoxic T cell (CTL)-based vaccines to prevent or treat cancer because the same sugar moieties are expressed in a variety of tumors, rendering a vaccination strategy applicable in a large population. Here we demonstrate that by using glycopeptides with high affinity for the major histocompatibility complex and glycosylated in a position corresponding to a critical T cell receptor (TcR) contact, it is possible to induce anti-TACA CTL in vivo. In the current study we show that designer glycopeptides containing the Thomsen-Freidenreich (TF) antigen (β-Gal-[1→3]-α-GalNAc-O-serine) are immunogenic in vivo and generate TF-specific CTL capable of recognizing a variety of tumor cells in vitro including a MUC1-expressing tumor. The fine specificity of the TF-specific CTL repertoire indicates that the TcR recognize the glycosylated amino acid residue together with TF in a conventional major histocompatibility complex class I–restricted fashion. These results have high potential for immunotherapy against a broad range of tumors.