Tinder, Teresa L.

Abstract Cyclooxygenase-2 (COX-2) inhibitors are rapidly emerging as a new generation of therapeutic drug in combination with chemotherapy or radiation therapy for the treatment of cancer. The mechanisms underlying its antitumor effects are not fully understood and more thorough preclinical trials are needed to determine if COX-2 inhibition represents a useful approach for prevention and/or treatment of breast cancer. The purpose of this study was to evaluate the growth inhibitory mechanism of a highly selective COX-2 inhibitor, celecoxib, in an in vivo oncogenic mouse model of spontaneous breast cancer that resembles human disease. The oncogenic mice carry the polyoma middle T antigen driven by the mouse mammary tumor virus promoter and develop primary adenocarcinomas of the breast. Results show that oral administration of celecoxib caused significant reduction in mammary tumor burden associated with increased tumor cell apoptosis and decreased proliferation in vivo. In vivo apoptosis correlated with significant decrease in activation of protein kinase B/Akt, a cell survival signaling kinase, with increased expression of the proapoptotic protein Bax and decreased expression of the antiapoptotic protein Bcl-2. In addition, celecoxib treatment reduced levels of proangiogenic factor (vascular endothelial growth factor), suggesting a role of celecoxib in suppression of angiogenesis in this model. Results from these preclinical studies will form the basis for assessing the feasibility of celecoxib therapy alone or in combination with conventional therapies for treatment and/or prevention of breast cancer.

Abstract We report that administration of celecoxib, a specific cyclooxygenase-2 (COX-2) inhibitor, in combination with a dendritic cell-based cancer vaccine significantly augments vaccine efficacy in reducing primary tumor burden, preventing metastasis, and increasing survival. This combination treatment was tested in MMTV-PyV MT mice that develop spontaneous mammary gland tumors with metastasis to the lungs and bone marrow. Improved vaccine potency was associated with an increase in tumor-specific CTLs. Enhanced CTL activity was attributed to a significant decrease in levels of tumor-associated IDO, a negative regulator of T cell activity. We present data suggesting that inhibiting COX-2 activity in vivo regulates IDO expression within the tumor microenvironment; this is further corroborated in the MDA-MB-231 human breast cancer cell line. Thus, a novel mechanism of COX-2-induced immunosuppression via regulation of IDO has emerged that may have implications in designing future cancer vaccines.

Abstract MUC1, a membrane tethered mucin glycoprotein, is overexpressed and aberrantly glycosylated in >80% of human ductal pancreatic adenocarcinoma. However, the role of MUC1 in pancreatic cancer has been elusive, partly due to the lack of an appropriate model. We report the characterization of a novel mouse model that expresses human MUC1 as a self molecule (PDA.MUC1 mice). Pancreatic tumors arise in an appropriate MUC1-tolerant background within an immune-competent host. Significant enhancement in the development of pancreatic intraepithelial preneoplastic lesions and progression to adenocarcinoma is observed in PDA.MUC1 mice, possibly due to increased proliferation. Tumors from PDA.MUC1 mice express higher levels of cyclooxygenase-2 and IDO compared with PDA mice lacking MUC1, especially during early stages of tumor development. The increased proinflammatory milieu correlates with an increased percentage of regulatory T cells and myeloid suppressor cells in the pancreatic tumor and tumor draining lymph nodes. Data shows that during pancreatic cancer progression, MUC1-mediated mechanisms enhance the onset and progression of the disease, which in turn regulate the immune responses. Thus, the mouse model is ideally suited for testing novel chemopreventive and therapeutic strategies against pancreatic cancer.

Abstract With a 5-year survival rate of <5%, pancreatic cancer is one of the most rapidly fatal malignancies. Current protocols for the treatment of pancreas cancer are not as effective as we desire. In this study, we show that a novel Mucin-1 (MUC1)-based vaccine in combination with a cyclooxygenase-2 inhibitor (celecoxib), and low-dose chemotherapy (gemcitabine) was effective in preventing the progression of preneoplastic intraepithelial lesions to invasive pancreatic ductal adenocarcinomas. The study was conducted in an appropriate triple transgenic model of spontaneous pancreatic cancer induced by the KRASG12D mutation and that expresses human MUC1 as a self molecule. The combination treatment elicited robust antitumor cellular and humoral immune responses and was associated with increased apoptosis in the tumor. The mechanism for the increased immune response was attributed to the down-regulation of circulating prostaglandin E2 and indoleamine 2, 3,-dioxygenase enzymatic activity, as well as decreased levels of T regulatory and myeloid suppressor cells within the tumor microenvironment. The preclinical data provide the rationale to design clinical trials with a combination of MUC1-based vaccine, celecoxib, and gemcitabine for the treatment of pancreatic cancer.

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

Abstract MUC1 is overexpressed and aberrantly glycosylated in more than 60% of pancreatic ductal adenocarcinomas. The functional role of MUC1 in pancreatic cancer has yet to be fully elucidated due to a dearth of appropriate models. In this study, we have generated mouse models that spontaneously develop pancreatic ductal adenocarcinoma (KC), which are either Muc1-null (KCKO) or express human MUC1 (KCM). We show that KCKO mice have significantly slower tumor progression and rates of secondary metastasis, compared with both KC and KCM. Cell lines derived from KCKO tumors have significantly less tumorigenic capacity compared with cells from KCM tumors. Therefore, mice with KCKO tumors had a significant survival benefit compared with mice with KCM tumors. In vitro, KCKO cells have reduced proliferation and invasion and failed to respond to epidermal growth factor, platelet-derived growth factor, or matrix metalloproteinase 9. Further, significantly less KCKO cells entered the G2–M phase of the cell cycle compared with the KCM cells. Proteomics and Western blotting analysis revealed a complete loss of cdc-25c expression, phosphorylation of mitogen-activated protein kinase (MAPK), as well as a significant decrease in nestin and tubulin-α2 chain expression in KCKO cells. Treatment with a MEK1/2 inhibitor, U0126, abrogated the enhanced proliferation of the KCM cells but had minimal effect on KCKO cells, suggesting that MUC1 is necessary for MAPK activity and oncogenic signaling. This is the first study to utilize a Muc1-null PDA mouse to fully elucidate the oncogenic role of MUC1, both in vivo and in vitro. Cancer Res; 71(13); 4432–42. ©2011 AACR.

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.