Michelle L. VanLith

Bio: Michelle L. VanLith is an academic researcher from University of Nebraska Medical Center. The author has contributed to research in topics: Immune system & T cell. The author has an hindex of 7, co-authored 8 publications receiving 606 citations. Previous affiliations of Michelle L. VanLith include Eppley Institute for Research in Cancer and Allied Diseases.

Tolerance and Immunity to MUC1 in a Human MUC1 Transgenic Murine Model

Abstract: 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 C57B1/6 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.

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

Abstract: 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.

The human homologue of the RNA polymerase II-associated factor 1 (hPaf1), localized on the 19q13 amplicon, is associated with tumorigenesis.

Abstract: The 19q13 amplicon in pancreatic cancer cells contains a novel pancreatic differentiation 2 (PD2) gene (accession number AJ401156), which was identified by differential screening analysis. PD2 is the human homologue of the RNA polymerase II-associated factor 1 (hPaf1). In yeast, Paf1 is part of the transcription machinery, acting as a docking protein in between the complexes Rad6-Bre1, COMPASS-Dot1p, and the phosphorylated carboxyl terminal domain of the RNA polymerase II. As such, Paf1 is directly involved in transcription elongation via histone H2B ubiquitination and histone H3 methylation. The PD2 sequence is highly conserved from Drosophila to humans with up to 98% identity between rodent and human, suggesting the functional importance of PD2/hPaf1 to maintain cellular homeostasis. PD2 is a modular protein composed of RNA recognition motif, DEAD-boxes, an aspartic/serine (DS)-domain, a regulator of the chromosome condensation domain and myc-type helix–loop–helix domains. Our results further showed that PD2 is a nuclear 80 kDa protein, which interacts with RNA polymerase II. In addition, we have demonstrated that the overexpression of PD2 in the NIH 3T3 cells result in enhanced growth rates in vitro and tumor formation in vivo. Altogether, this paper presents strong evidence that the overexpression of PD2/hPaf1 is involved in cancer development.

CD4+ Lymphocytes Provide MUC1-Specific Tumor Immunity In Vivo That Is Undetectable In Vitro and Is Absent in MUC1 Transgenic Mice

Abstract: 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.

Tumor-specific immunity in MUC1.Tg mice induced by immunization with peptide vaccines from the cytoplasmic tail of CD227 (MUC1)

Abstract: Purpose: CD227 (MUC1), a membrane-associated glycoprotein expressed by many types of ductal epithelia, including pancreas, breast, lung, and gastrointestinal tract, is overexpressed and aberrantly glycosylated by malignant cells. We sought to define epitopes on MUC1 recognized by the different cell-mediated immune responses by an in vivo assay. Epitopes identified by this assay were evaluated for efficacy to protect mice transgenic for human MUC1 (MUC1.Tg) against MUC1-expressing tumor growth. Methods: We investigated contributions of the tandem repeat (TR) and the cytoplasmic tail (CT) of MUC1 to the MUC1-specific immunological rejection of tumor cells. MUC1 cDNA constructs, in which the TR region was deleted or the CT was truncated, were transfected into two different murine tumor cell lines (B16 and Panc02), which were used to challenge mice and evaluate immunological rejection of the tumors. We used tumor rejection in vivo to define epitopes on the TR and CT of MUC1 recognized by T cell–mediated immune responses in a preclinical murine model. Results: Our findings demonstrated that the TR and a portion of the MUC1 CT contributed to CD4+ T cell rejection of MUC1-expressing B16 tumor cells, but not rejection of MUC1-expressing Panc02 tumor cells. A separate epitope in the CT of MUC1 was necessary for CD8+ T cell rejection of Panc02 tumor cells. Based on these studies, we sought to evaluate the efficacy of immunizing mice transgenic for (and immunologically tolerant to) human MUC1 with peptides derived from the amino acid sequence of the CT of MUC1. Results showed that survival can be significantly prolonged in vaccinated MUC1.Tg mice challenged with MUC1-expressing tumor cells, without induction of autoimmune responses. Conclusions: These studies demonstrated that MUC1 peptides may be utilized as an effective anticancer immunotherapeutic, and confirmed the importance of immunogenic epitopes outside of the TR.

Structure and Function of the Cell Surface (Tethered) Mucins

Abstract: Cell surface mucins are large transmembrane glycoproteins involved in diverse functions ranging from shielding the airway epithelium against pathogenic infection to regulating cellular signaling and transcription. Although hampered by the relatively recent characterization of cell surface mucins and the difficulties inherent in working with molecules of their size, numerous studies have placed the tethered mucins in the thick of normal and diseased lung physiology. This review focuses on the three best-characterized cell surface mucins expressed in the respiratory tract: MUC1, MUC4, and MUC16.

MUC1, the renaissance molecule.

Abstract: MUC1 is a large, heavily glycosylated mucin expressed on the apical surfaces of most simple, secretory epithelia including the mammary gland, gastrointestinal, respiratory, urinary and reproductive tracts. Although MUC1 was thought to be an epithelial-specific protein, it is now known to be expressed on a variety of hematopoietic cells as well. Mucins function in protection and lubrication of epithelial surfaces. Transmembrane mucins, which contain cytoplasmic tail domains, appear to have additional functions through their abilities to interact with many proteins involved in signal transduction and cell adhesion. The goal of this review is to highlight recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry.

A peptide encoded by circular form of LINC-PINT suppresses oncogenic transcriptional elongation in glioblastoma

Abstract: Circular RNAs (circRNAs) are a large class of transcripts in the mammalian genome. Although the translation of circRNAs was reported, additional coding circRNAs and the functions of their translated products remain elusive. Here, we demonstrate that an endogenous circRNA generated from a long noncoding RNA encodes regulatory peptides. Through ribosome nascent-chain complex-bound RNA sequencing (RNC-seq), we discover several peptides potentially encoded by circRNAs. We identify an 87-amino-acid peptide encoded by the circular form of the long intergenic non-protein-coding RNA p53-induced transcript (LINC-PINT) that suppresses glioblastoma cell proliferation in vitro and in vivo. This peptide directly interacts with polymerase associated factor complex (PAF1c) and inhibits the transcriptional elongation of multiple oncogenes. The expression of this peptide and its corresponding circRNA are decreased in glioblastoma compared with the levels in normal tissues. Our results establish the existence of peptides encoded by circRNAs and demonstrate their potential functions in glioblastoma tumorigenesis.