Organ-specific pancreatic tumor growth properties and tumor immunity.

We established a model of orthotopic injection of a syngeneic pancreatic tumor cell line in C57BL/6 mice and evaluated the effects of organ site on induction of immunity to a tumor-specific antigen, MUC1. Mice were challenged with a syngeneic pancreatic adenocarcinoma cell line that expressed MUC1 (Panc02-MUC1) by orthotopic injection into the pancreas, or by subcutaneous injection. Tumor cells injected into the pancreas grew much faster than those injected subcutaneously. Mice challenged subcutaneously with Panc02-MUC1 rejected tumors or developed slowly growing tumors that were negative for MUC1 expression. In contrast, mice challenged orthotopically into the pancreas developed progressive tumors that were positive for MUC1 expression. Sera from mice that rejected PancO2-MUC1 (tumor-immune mice) showed no detectable IgG1 and IgM titers against the MUC1 tandem-repeat peptide, whereas mice with progressive tumor growth had significant titers of IgG1 and IgM specific for MUC1. This suggests that the humoral immune response was ineffective in mediating tumor rejection. The results show that the growth properties and immunological rejection of pancreatic tumors is affected by the organ site at which the tumor grows.

Passively transferred anti-MUC1 antibodies cause neither autoimmune disorders nor immunity against transplanted tumors in MUC1 transgenic mice.

C57BL/6 mice transgenic for human MUC1 (MUC1.Tg) have been developed to investigate the autoimmune consequences of producing MUC1 tumor immunity in an animal that expresses MUC1 as a self-protein on normal ductal epithelia. Previous work showed that MUC1.Tg mice challenged with MUC1-bearing syngeneic tumors (B16.MUC1) developed progressively growing MUC1-expressing tumors and no detectable MUC1-specific antibody (Ab) response. In contrast, wild-type C57BL/6 (wt) mice developed MUC1-negative tumors at a significantly slower rate and produced approximately 50 microg IgG1 Ab reactive with the MUC1 tandem repeat (TR)/ml of sera. One milliliter of these sera was administered passively to MUC1.Tg or wt mice and the concentration of the MUC1 TR-reactive IgG1 Abs was monitored over time. The results indicate that circulating MUC1-reactive Abs were detectable in MUC1.Tg mice and that significant amounts of these Abs were not absorbed by organs that endogenously express MUC1. No evidence of autoimmune disease, either gross or histological, was observed in the MUC1.Tg recipients of sera suggesting that MUC1, an organ-specific protein expressed primarily by secretory epithelia, is inaccessible to circulating MUC1 -reactive Abs. Additional studies showed that polyclonal sera containing IgG1 Abs reactive with MUC1 TR were unable to provide protection against the growth of syngeneic tumors expressing MUC1 in the MUC1.Tg animal model.

CD4+ lymphocytes provide MUC1-specific tumor immunity in vivo that is undetectable in vitro and is absent in MUC1 transgenic mice.

A C57BL/6 mouse transgenic for human MUC1 (MUC1.Tg) was developed to evaluate MUC1-specific tumor immunity in an animal that expresses MUC1 as a normal self protein. Previous studies showed that MUC1.Tg mice, challenged with syngeneic tumors expressing MUC1 (B16.MUC1), developed progressively growing MUC1-positive tumors, whereas wild-type C57BL/6 (wt) mice developed MUC1-negative tumors at a significantly slower rate. The results of a limiting dilution CTL frequency assay were not informative, in that similar numbers of MUC1-specific CTL precursors (CTL) were detected in MUC1.Tg and wt mice. Tumor immunity in vivo was characterized by an adoptive transfer method to evaluate the degree of MUC1 or non-MUC1 tumor immunity in wt or MUC1.Tg mice. The results revealed that wt mice developed protective tumor immunity mediated by MUC1-specific CD4+ lymphocytes, while MUC1.Tg mice were functionally tolerant to MUC1 in vivo. The potential of adoptive immunotherapy to provide immunity to tumors expressing MUC1 and to produce undesirable autoimmunity in recipient MUC1.Tg mice expressing MUC1 as a self Ag was evaluated. Adoptive transfer of immune cells from wt mice primed in vivo with B16.MUC1 tumor cells into MUC1.Tg recipients resulted in significant increases in the survival of MUC1.Tg recipients compared with unmanipulated control MUC .Tg mice challenged with B16.MUC1 tumor cells. This response was specific for MUC1 since control tumors developed at equivalent rates in recipient or control MUC1.Tg mice. No gross or histologic evidence of autoimmunity was observed in recipient MUC1.Tg mice, indicating that tumor immune responses mediated by MUC1-specific CD4+ lymphocytes spare nontransformed epithelia-expressing MUC1.

Tolerance and immunity to MUC1 in a human MUC1 transgenic murine model.

The human epithelial mucin, MUC1, is a large transmembrane glycoprotein that is expressed on most simple epithelia. It is overexpressed and aberrantly glycosylated on many human epithelial tumors, including more than 90% of human breast cancers. MUC1 is of interest as an immunotherapy target because patients with breast, ovarian, and pancreatic cancers have T lymphocytes in their tumor-draining lymph nodes that can be induced to recognize and lyse MUC1-expressing tumor cells. We have produced a transgenic mouse model that expresses the human MUC1 molecule on an inbred C57Bl/6 background to investigate the effect of endogenous expression of MUC1 on the ability of mice to generate antitumor immunity to MUC1-expressing tumors. Transgenic mice expressed the human transgene in a pattern and level consistent with that observed in humans. Transgenic mice were tolerant to stimulation by MUC1 as evidenced by the ability of MUC1-expressing tumor cells to grow in these mice, whereas MUC1-expressing cells were eliminated from wild-type mice. Moreover, transgenic mice immunized with MUC1 peptides failed to exhibit immunoglobulin class switching to the IgG subtypes. These data suggest that endogenous expression of MUC1 protein by MUC1 transgenic mice induces T-cell tolerance to stimulation by MUC1. The transgenic mice will provide a useful model to investigate the mechanisms that regulate immunological tolerance to tumor antigens and will facilitate the investigation of anti-MUC1 immunotherapy formulations.

Molecular adjuvant effects of a conformationally biased agonist of human C5a anaphylatoxin.

A conformationally biased decapeptide agonist of human C5a anaphylatoxin (YSFKPMPLaR) was used as a molecular adjuvant in stimulating Ab responses against peptide epitopes derived from human MUC1 glycoprotein and the human mu and kappa opioid receptors. C57BL6 mice were immunized with the MUC1 epitope (YKQGGFLGL); the C5a agonist (YSFKPMPLaR); YSFKPMPLaR and YKQGGFLGL together, but unconjugated; a C5a-active, MUC1 epitope construct (YKQGGFLGLYSFKPMPLaR); and a C5a-inactive, reversed moiety construct (YSFKPMPLaRYKQGGFLGL). High Ab titers specific for the MUC1 epitope were observed only in mice immunized with the C5a-active epitope construct. Similar results were obtained in BALB/c mice immunized with the C5a-active, MUC1 epitope construct. Abs from the sera of the C57BL6 mice were predominately of the IgG2a, IgG2b, and IgM isotypes and were reactive against human recombinant MUC1 and MUC1 expressed by the Panc-1 M1F.15 pancreatic cell line. When compared with the corresponding KLH-epitope conjugates in C57BL6 mice, the epitope-C5a agonist constructs produced titers of specific IgG Abs of isotypes distinct from those generated by the keyhole limpet hemocyanin-epitope conjugates. Rabbits immunized with a mu opioid receptor epitope-C5a agonist construct (GDLSDPCGNRTNLGGRDSLYSFKPMPLaR) or a kappa opioid receptor epitope-C5a agonist construct (FPGWAEPDSNGSEDAQLYSFKPMPLaR) generated high titer, epitope-specific Ab responses. Ab titers generated in response to the opioid epitope-C5a agonist constructs were comparable to those generated by the opioid KLH-epitope conjugates. The results of this study are discussed in terms of possible mechanisms by which the conformationally biased C5a agonist serves as a molecular adjuvant.

Epidermoid cyst of the floor of the mouth.

The characteristics and incidence of dermoid cysts of the floor of the mouth are reviewed. The epidermoid cyst in the sublingual (genioglossal) position is unique because of its size and the advanced age of presentation. The use of preoperative lateral xerography was beneficial in determining the extent of the lesion and in visualizing the partial obstruction of the upper airway. An intraoral surgical technique was used to treat the cyst.