Mice with Spontaneous Pancreatic Cancer Naturally Develop MUC-1-Specific CTLs That Eradicate Tumors When Adoptively Transferred

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.

Characterization of the MUC1.Tg/MIN transgenic mouse as a model for studying antigen-specific immunotherapy of adenomas

“…To evaluate MUC1 expression, tumors and normal tissues were fixed in methacarn (60% methanol, 30% chloroform, 10% glacial acetic acid), paraffin embedded, and sectioned for immunohistochemical analysis as previously described [16,17]. In a separate experiment, following enumeration of the adenomas, the intestinal segments were formalin fixed and individual tumors were excised from each segment and placed in cassettes with sponges to maintain orientation.…”

“…Splenocytes were isolated from vaccinated mice and incubated in 6 well plates at a density of 1×10 6 cells/mL with the MUC1 TR peptides and the hepatitis B virus core antigen pan helper peptide, each at 20 ng/mL for 48 h as previously described [16]. The supernatants were harvested and analyzed for the presence of IFN-γ by ELISA (Pierce Endogen, Rockford IL).…”

“…Although MUC1 is a self protein, immune responses against MUC1, as manifested by the presence of antibodies and CTL, have been reported in some patients with breast, ovarian and colon cancer [14]. Furthermore, studies of MUC1-expressing transgenic mice have demonstrated the presence of MUC1-specific CTLs that can kill MUC1-expressing tumor cells in vitro and suppress tumor growth in vivo [16][17][18][19]. Taken together, these observations suggest that mobilization of an immune response against MUC1 could potentially be useful in treating adenomas without associated toxicity and could result in the acquisition of long-term immunity.…”

MUC1-specific immune therapy generates a strong anti-tumor response in a MUC1-tolerant colon cancer model

“…MUC1 (CD227) is a membrane-tethered mucin glycoprotein expressed on the apical surfaces of normal glandular epithelia and it is over expressed and aberrantly glycosylated in >70% of human colon cancer [1][2][3]. Recent description of MUC1 as a target for cytotoxic T lymphocytes (CTLs) has raised interest in using this protein as a target for immunotherapy [4][5][6][7][8][9][10][11][12][13][14]. Several preclinical and clinical trials targeting the tumor-associated MUC1 antigen have elicited strong anti-tumor CTLs [1,2,12,[14][15][16][17][18][19][20][21][22][23][24].…”

Cancer Vaccine

“…However, it is not known if the use of dendritic cells or mixed APCs for the active immunotherapy of cancer has an advantage over more conventional vaccine approaches, which are simpler and much less expensive. We usually propose WT1, MUC1, CEA, CA125, HER-2/neu, and PSA as cancer antigens for DC based therapy according to the patient's primary lesion and elevated tumor marker (Sugiyama, 2005;Mukherjee et al, 2000;Nair et al, 1999;Larbcurrentet et al, 2007). It has been reported that WT1 and MUC1 is antigens with high immunogenicity and their-targeted immunotherapy have confirmed its safety and clinical efficacy, although there is few description concerning cancer vaccine adapting WT1 and MUC1 simultaneously to cancer antigen (Ramanathan et al, 2005).…”