The MUC1 Cytoplasmic Tail and Tandem Repeat Domains Contribute to Mammary Oncogenesis in FVB Mice

Background: Though the importance of the transmembrane mucin MUC1 in mammary oncogenesis has long been recognized, the relative contributions of the cytoplasmic tail and tandem repeat domains are poorly understood.Methods: To address this, mouse models of mammary carcinogenesis were created expressing full-length, cytoplasmic tail-deleted, or tandem repeat-deleted MUC1 constructs.Results: Overexpression of full-length MUC1 resulted in tumor formation in young mice (12 months); however, loss of either the cytoplasmic tail or the tandem repeat domain abrogated this oncogenic capacity. Aged mice in all strains developed late-onset mammary tumors similar to those previously described for the FVB background.Conclusions: This study is the fi rst spontaneous cancer model to address the relative importance of the cytoplasmic tail and tandem repeat domains to MUC1-driven mammary oncogenesis, and suggests that both of these domains are essential for tumor formation

Muc1 enhances the β-catenin protective pathway during ischemia-reperfusion injury

The hypoxia-inducible factor (HIF)-1 and β-catenin protective pathways represent the two most significant cellular responses that are activated in response to acute kidney injury. We previously reported that murine mucin (Muc)1 protects kidney function and morphology in a mouse model of ischemia-reperfusion injury (IRI) by stabilizing HIF-1α, enhancing HIF-1 downstream signaling, and thereby preventing metabolic stress (Pastor-Soler et al. Muc1 is protective during kidney ischemia-reperfusion injury. Am J Physiol Renal Physiol 308: F1452-F1462, 2015). We asked if Muc1 regulates the β-catenin protective pathway during IRI as 1) β-catenin nuclear targeting is MUC1 dependent in cultured human cells, 2) β-catenin is found in coimmunoprecipitates with human MUC1 in extracts of both cultured cells and tissues, and 3) MUC1 prevents β-catenin phosphorylation by glycogen synthase kinase (GSK)3β and thereby β-catenin degradation. Using the same mouse model of IRI, we found that levels of active GSK3β were significantly lower in kidneys of control mice compared with Muc1 knockout (KO) mice. Consequently, β-catenin was significantly upregulated at 24 and 72 h of recovery and appeared in the nuclear fraction at 72 h in control mouse kidneys. Both β-catenin induction and nuclear targeting were absent in Muc1 KO mice. We also found downstream induction of β-catenin prosurvival factors (activated Akt, survivin, transcription factor T cell factor 4 (TCF4), and its downstream target cyclin D1) and repression of proapoptotic factors (p53, active Bax, and cleaved caspase-3) in control mouse kidneys that were absent or aberrant in kidneys of Muc1 KO mice. Altogether, the data clearly indicate that Muc1 protection during acute kidney injury proceeds by enhancing both the HIF-1 and β-catenin protective pathways

MUC1 Vaccines, Comprised of Glycosylated or Non-Glycosylated Peptides or Tumor-Derived MUC1, Can Circumvent Immunoediting to Control Tumor Growth in MUC1 Transgenic Mice

It remains challenging to produce decisive vaccines against MUC1, a tumor-associated antigen widely expressed by pancreas, breast and other tumors. Employing clinically relevant mouse models, we ruled out such causes as irreversible T-cell tolerance, inadequate avidity, and failure of T-cells to recognize aberrantly glycosylated tumor MUC1. Instead, every tested MUC1 preparation, even non-glycosylated synthetic 9mer peptides, induced interferon gamma-producing CD4(+) and CD8(+) T-cells that recognized glycosylated variants including tumor-associated MUC1. Vaccination with synthetic peptides conferred protection as long as vaccination was repeated post tumor challenge. Failure to revaccinate post challenge was associated with down-regulated tumor MUC1 and MHC molecules. Surprisingly, direct admixture of MUC1-expressing tumor with MUC1-hyperimmune T-cells could not prevent tumor outgrowth or MUC1 immunoediting, whereas ex vivo activation of the hyperimmune T-cells prior to tumor admixture rendered them curative. Therefore, surrogate T-cell preactivation outside the tumor bed, either in culture or by repetitive vaccination, can overcome tumor escape

Muc1 is protective during kidney ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) due to hypotension is a common cause of human acute kidney injury (AKI). Hypoxia-inducible transcription factors (HIFs) orchestrate a protective response in renal endothelial and epithelial cells in AKI models. As human mucin 1 (MUC1) is induced by hypoxia and enhances HIF-1 activity in cultured epithelial cells, we asked whether mouse mucin 1 (Muc1) regulates HIF-1 activity in kidney tissue during IRI. Whereas Muc1 was localized on the apical surface of the thick ascending limb, distal convoluted tubule, and collecting duct in the kidneys of sham-treated mice, Muc1 appeared in the cytoplasm and nucleus of all tubular epithelia during IRI. Muc1 was induced during IRI, and Muc1 transcripts and protein were also present in recovering proximal tubule cells. Kidney damage was worse and recovery was blocked during IRI in Muc1 knockout mice compared with congenic control mice. Muc1 knockout mice had reduced levels of HIF-1α, reduced or aberrant induction of HIF-1 target genes involved in the shift of glucose metabolism to glycolysis, and prolonged activation of AMP-activated protein kinase, indicating metabolic stress. Muc1 clearly plays a significant role in enhancing the HIF protective pathway during ischemic insult and recovery in kidney epithelia, providing a new target for developing therapies to treat AKI. Moreover, our data support a role specifically for HIF-1 in epithelial protection of the kidney during IRI as Muc1 is present only in tubule epithelial cells

Diagram of MUC1 Domains and Peptides Chosen for Study.

<p>The domains of MUC1 are shown on left side of the diagram with the sequences studied listed below the domains and the peptide name on the right side. Immunizing peptides and serines (S) and threonines (T) that are <i>O</i>-glycosylated with N-Acetylgalactosamine (Tn) are shaded.</p

Lysate Sensitized T-Cells from MUC1.Tg Mice Conferred Protection in Adoptive Transfer Experiments (Winn Assay).

<p><b>(A)</b> The sorted spleen-derived effector T-cells from MUC1.Tg mice immunized with rotating tumor cell lysates were co-injected with B16.MUC1 tumor cells (T-cell to tumor cell ratio of 10:1) either directly or after stimulation <i>in vitro</i> with DCs pulsed with B16.MUC1 tumor cell lysates. T-cells from non-immunized MUC1.Tg mice were co-injected with B16.MUC1 tumor cells as controls. The mice that received T-cells after <i>in vitro</i> sensitization showed complete protection from tumor growth, (p<0.001). <b>(B)</b> The B16.MUC1 tumors resistant to T-cells from immunized MUC1.Tg mice showed low MUC1 expression vs non-immunized mice (p = 0.02). <b>(C)</b> Corresponding histograms of MUC1 expression are shown. Experiment was repeated two times, n = 4 mice/group.</p