Sialyl-Lewis x and Sialyl-Lewis a are associated with MUC1 in human endometrium

Endometrial epithelial cells express MUC1 with increased abundance in the secretory phase of the menstrual cycle, when embryo implantation occurs. MUC1 is associated with the apical surface of epithelial cells and is also secreted, being detectable in uterine fluid at elevated levels in the implantation phase. However, its physiological role is uncertain; it may either inhibit intercellular adhesion by steric hindrance or carry carbohydrate recognition structures capable of mediating cell-cell interaction. Here we show that endometrial epithelium expresses both Sialyl-Lewis x (SLe^x) and Sialyl-Lewis a (SLe^a), with a distribution and pattern of menstrual cycle regulation similar to that of MUC1. Using Western blotting and double determinant ELISA of uterine flushings, we demonstrate that SLe^x is associated with MUC1 core protein. The endometrial carcinoma cell lines HEC1A and HEC1B are shown to express MUC1 in a mosaic pattern, while three other cell lines express much lower amounts. HEC1A expresses both SLe^x and SLe^a while HEC1B expresses SLe^a only. Immunoprecipitation has been used to demonstrate that SLe^a is associated with MUC1 in HEC1B cells, and both SLe^x and SLe^a are associated with MUC1 in HEC1A cells.     

MUC1 is a substrate for γ‐secretase

Understanding the underlying mechanisms by which a normal cell avoids the oncogenic potential of MUC1 signaling requires further definition of the pathways by which the MUC1 cytoplasmic tail is processed in both normal and tumor‐derived cells. In the present study we describe the processing pathway initiated by TACE/ADAM17 cleavage of MUC1. Utilizing the human uterine epithelial cell line, HES, derived from normal endometrium, we show that endogenous full length MUC1 undergoes regulated intramembranous proteolysis mediated by presenillin‐dependent γ‐secretase. Cytokine‐stimulated HES cells exposed to γ‐secretase inhibitors accumulated a membrane‐associated 15 kDa fragment of the MUC1 C‐terminal subunit (CTF15). Inhibitors of TACE/ADAM17‐mediated shedding inhibited accumulation of MUC1‐CTF15 and MUC1 ectodomain release to a similar extent consistent with MUC1‐CTF15 being a product of TACE/ADAM17 action. Reduction of catalytically active γ‐secretase complex by nicastrin siRNA treatment also resulted in CTF15 accumulation. Furthermore, mature nicastrin, the substrate receptor for γ‐secretase, co‐immunoprecipitated with CTF15 in the presence of γ‐secretase inhibitors indicating the formation of CTF15: nicastrin complexes. MUC1‐CTF15 accumulation in response to γ‐secretase inhibition was demonstrated in both normal and tumor‐derived cells from humans and mice indicating that this processing pathway exists in many cell contexts. We did not detect products of MUC1 cleavage by γ‐secretase in the presence of various proteasomal inhibitors indicating that subsequent degradation is either non‐proteasomal or extremely efficient. We suggest that this efficient pathway attenuates potential signaling mediated by cytoplasmic tail fragments. J. Cell. Biochem. 108: 802–815, 2009. © 2009 Wiley‐Liss, Inc.     

The expression of human FUT1 in HT-29/M3 colon cancer cells instructs the glycosylation of MUC1 and MUC5AC apomucins

Recently, we have reported that in normal gastric epithelium, the expression of gastric apomucins MUC5AC and MUC6 is associated with the specific expression of type 1 and type 2 Lewis antigens, and FUT2 and FUT1 fucosyltransferases, respectively. Until now, there are no data demonstrating the direct implication of specific glycosyltransferases in the specific patterns of apomucin glycosylation.HT29/M3 colon cancer cell line express MUC1, MUC5AC, type 1 Lewis antigens and FUT2 but not type 2 structures and FUT1, as it occurs in the epithelial cells of the gastric superficial epithelium. These cells were transfected with the cDNA of human FUT1, the -1,2-fucosyltransferase responsible for the synthesis of type 2 Lewis antigens, to assess the implication of FUT1 in the glycosylation of MUC1 and MUC5AC.The M3-FUT1 clones obtained express high levels of type 2 Lewis antigens: H type 2 and Ley antigens. Immunoprecipitation of MUC1 and MUC5AC apomucins gives the direct evidence that FUT1 catalyses the addition of -1,2-fucose to these apomucins, supporting the hypothesis that the pattern of apomucin glycosylation is not only instructed by the mucin primary sequence but also by the set of glycosyltransferases expressed in each specific cell type.     

Relationship between uterine expression of matrix metalloproteinases and their inhibitors and endometrial receptivity

In order to investigate the relationship between the endometrial receptivity and matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1,-3 (TIMP-1,-3) in the endometrium, we used early pregnant mice as the animal model and studied the expression of MMP-2, TIMP-1,-3 in the endometrium in relation to the number of implantation sites after RU486 treatment. The results indicated that RU486 could significantly inhibit embryo implantation and change the expression of MMP-2 and TIMP-1,-3 in a dose-dependent pattern. When the mice were treated with 12 mg/kg RU486, there were a few embryos implanted as compared with the control. The expression of matrix metalloproteinase MMP-2 was low during the period of "implantation window", while the tissue inhibitor of metalloproteinase in the endometrial cells was high, suggesting that the activity of the proteolytic enzyme was strictly controlled by its inhibitors. After RU486 treatment, the generation of TIMP-1,3 was decreased while the MMP-2 was significantly increased, indicating that the normal balance between the activators and their inhibitors in the tissue was broken and the extracellular matrix was excessively degraded, subsequently the embryo implantation was inhibited. Therefore, it is suggested that the anti-implantation effect of RU486 may be mediated by MMPs and their inhibitors TIMPs.     

MUC1蛋白的结构、功能及应用

MUC1粘蛋白是一种大分子量的糖蛋白,主要存在于乳腺、胰腺、卵巢等上皮性组织和器官中。它在癌变上皮细胞表面高度异常表达,结构发生相应改变,从而成为免疫应答的靶点,并在乳腺癌的发展、转移、预后及免疫治疗中起到重要作用。     

Relationship between uterine expression of matrix metalloproteinases and their inhibitors and endometrial receptivity

In order to investigate the relationship between the endometrial receptivity and matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 ,-3 (TIMP-1,-3) in the en-dometrium, we used early pregnant mice as the animal model and studied the expression of MMP-2, TIMP-1 ,-3 in the endometrium in relation to the number of implantation sites after RU486 treatment. The results indicated that RU486 could significantly inhibit embryo implantation and change the expression of MMP-2 and TIMP-1,-3 in a dose-dependent pattern. When the mice were treated with 12 mg/kg RU486, there were a few embryos implanted as compared with the control. The expression of matrix metalloproteinase MMP-2 was low during the period of "implantation window", while the tissue inhibitor of metalloproteinase in the endometrial cells was high, suggesting that the activity of the proteolytic enzyme was strictly controlled by its inhibitors. After RU486 treatment, the generation of TIMP-1,3 was decreased while the MMP-2 wa     

Differential expression of MUC1 on transfected cell lines influences its recognition by MUC1 specific T cells

In adenocarcinomas of the breast and pancreas, underglycosylation of the glycoprotein MUC1, also expressed by normal breast and pancreatic ductal epithelial cells, results in new protein epitopes to which the immune system mounts a cytotoxic T cell response. This cytotoxic immune response is directed primarily against epitopes on the tandem repeat domain of MUC1, and is unconventional in that it is major histocompatibility complex (MHC)-unrestricted. It is therefore necessary to investigate the molecular basis of this immune response in order to enhance and optimize it for immune therapy purposes. In the present study, we characterize new MUC1 transfected human lymphoblastoid cell lines C1R and T2, and a pig kidney epithelial line LLC-PK₁, that express MUC1 with either two repeats (MUC1–2R) or 22 repeats (MUC1–22R), and use them as stimulators and targets for cytotoxic T cells (CTL)in vitro. We show that MUC1–2R is processed and glycosylated similarly to MUC1–22R. In contrast to MUC1–22R, MUC1–2R is not recognized by CTL on T2 and C1R cells known for no or low MHC class I expression. It is however recognized when expressed at high density on xenogeneic LLC-PK₁ cells. We propose that in MHC-unrestricted recognition, a large number of MUC1 epitopes is necessary to effectively engage the T cell receptor, and that in the presence of a low number of epitopes, engagement of the CD8 co-receptor by MHC class I molecules may be required for completing the signal through the T cell receptor.     

Calcitonin administration improves endometrial receptivity via regulation of LIF,Muc-1 and microRNA Let-7a in mice

Calcitonin (CT) is one of the factors affecting the embryo implantation, but its effects on the implantation window have not been fully investigated. The current study investigated the effects of CT on the endometrium receptivity by morphological study and evaluation of leukemia inhibitory factor (LIF), mucin 1 (Muc-1), and microRNA (miRNA) Let-7a in the ovarian stimulation and the normal ovarian cycle. Then the mechanism of the CT effects through the mammalian target of rapamycin (mTOR) signaling pathway was studied by using PP242. A total of 64 BALB/c mice were divided into the normal ovarian cycle and ovarian stimulation groups. Each group consisted of four subgroups: control, calcitonin, PP242, and calcitonin+PP242. CT and PP242 were injected on the fourth of pregnancy into the mice and 24 hr later all the mice were killed. The uterine tissue samples were used for morphological analysis, and endometrial cells were mechanically isolated for evaluation of gene and protein expression. The results showed that ovarian stimulation induced mTOR phosphorylation as well as increased expression of the Let-7a miRNA. In addition, CT injection increased the expression of LIF and miRNA Let-7a in ovarian stimulation similar to that in normal ovarian cycles. However, injection of PP242 reduced expression of miRNA Let-7a and increased Muc-1 expression in ovarian stimulation group. In conclusion, the administration of CT improved endometrial receptivity in mice. This phenomenon occurred by upregulation of LIF, miRNA Let-7a and downregulation of Muc-1 via mTOR signaling pathway.     

High expression of MUC20 drives tumorigenesis and predicts poor survival in endometrial cancer

Mucins (MUCs) have been reported to play a critical role in the tumorigenesis of different cancers. This study was performed to explore the effect of MUC20 in endometrial cancer (EC). A total of 541 patients with EC were examined from The Cancer Genome Atlas. The relationship between MUC20 expression and clinical characteristics was analyzed with the Wilcoxon signed-rank test and logistic regression. The Kaplan-Meier method and the Cox regression model was performed to evaluate the prognosis. Gene set enrichment analysis (GSEA) was conducted. MUC20 high expression was associated with age, histology, positive peritoneal cytology, advanced stage, and lymph node metastasis (P < 0.05). Kaplan-Meier survival showed that patients with MUC20 high expression had a poorer prognosis than those with MUC20 low expression. Furthermore, multivariate analysis showed that MUC20 high expression was an independent prognostic factor for worse overall survival (hazard ratio = 1.93, 95% confidence interval = 1.00-3.74). Moreover, interferon α/γ response, cell-cell adhesion, O-glycan processing, and reactive oxygen species (ROS) pathway were associated with MUC20 high expression. MUC20 high expression may be a potential prognostic molecular factor of poor survival. The interferon α/γ response, cell-cell adhesion, O-glycan processing, and ROS pathway may be the key processes regulated by MUC20 in EC.     

胃癌组织中的MUC1和VEGF表达及其意义

目的:检测胃癌组织中VEGF和MUC1的表达情况,研究二者与胃癌生物学行为之间的关系。方法:应用免疫组织化学SP法检测VEGF和MUC1在胃癌组织和癌旁组织中的表达情况。结果:胃癌组织中VEGF的阳性表达明显高于癌旁组织,两者之间差异存在统计学意义(P0.05),VEGF在胃癌组织中的表达与胃癌浸润深度、有无远处转移、有无淋巴结转移、TNM分期有关,之间差异存在统计学意义(P0.05);胃癌组织中MUC1的阳性表达明显高于癌旁组织,两者之间差异存在统计学意义(P0.05),MUC1在胃癌组织中的表达与分化程度、TNM分期、淋巴结转移、远处转移有关,差异有统计学意义(P0.05);胃癌患者组织VEGF与MUC1的表达水平呈正相关(r=0.210,P0.05)。结论:VEGF和MUC1在胃癌发生、发展和转移过程中起重要作用,可能成为检测胃癌的重要肿瘤标志物。     

N-Glycosylation of the MUC1 mucin in epithelial cells and secretions

The MUC1 mucin is an important tumor-associated antigen that shows extensive glycosylation in vivo. The O-glycosylation of this molecule, which has been well characterized in many cell types and tissues, is important in conferring the unusual biochemical and biophysical properties on a mucin. N-Glycosylation is crucial to the folding, sorting, membrane trafficking, and secretion of many proteins. Here, we evaluated the N-glycosylation of MUC1 derived from two sources: endogenous MUC1 isolated from human milk and a recombinant epitope-tagged MUC1F overexpressed in Caco2 colon carcinoma cells. N-Glycans on purified MUC1F/MUC1 were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), gas chromatography-mass spectrometry (GC-MS), and CAD-ESI-MS/MS. The spectra indicate that MUC1F N-glycans have compositions consistent with high-mannose structures (Hex(5-9)HexNAc(2)) and complex/hybrid-type glycans (NeuAc(0-3)Fuc(0-3)Hex(3-8)HexNAc(3-7)). Many of the N-glycan structures are identical on MUC1F and native MUC1; however, a marked difference is seen between the N-glycans on membrane-bound and secreted forms of the native molecule.     

MUC1粘蛋白的分离纯化及其抗体的制备

经高速离心从正常人乳中获得人乳汁颗粒膜(HMFGM),产量约0．4g／L。经进一步破碎、脱脂及sepharose CL-4B柱纯化,获得含MUC1粘蛋白的组分,并经SDS—PAGE、Western—blot及ELISA鉴定后,免疫家兔制备多抗。结果表明,进一步凝胶过滤获得MUC1粘蛋白,行SDS—PAGE后经希夫试剂和考马斯亮蓝染色呈单一条带,表观相对分子质量大干205000。Western—blot及ELISA结果表明可与MUC1特异性抗体结合。制备获得的多抗经ELISA测定效价为1：64000～1：128000。表明建立了MUC1粘蛋白的纯化方法,获得的MUC1粘蛋白及其抗体可进一步用于MUC1检测及其功能的研究。     

In vivo glycosylation of MUC1 in airway epithelial cells

The O-glycans that decorate mucin glycoproteins contribute to the biophysical and biochemical properties of these molecules and hence their function as a barrier and lubricant on epithelial surfaces. Alterations in mucin O-glycosylation in certain diseases may contribute to pathology. It is known that both the host cell type and the amino acid sequence of the mucin tandem repeat contribute to the O-glycosylation of a mucin molecule. We expressed an epitope-tagged MUC1 mucin cDNA construct in the airway cell line 16HBE14o- and the colon carcinoma cell line Caco2 and used Fast Atom Bombardment Mass Spectrometry to evaluate the contribution of the host cell to differences in O-glycosylation of a single mucin. Many of the glycans detected on the MUC1 mucin were common to both cell types, as would be predicted from biosynthetic constraints. However, MUC1 synthesized in the airway cell line showed comparatively low levels of sialylation but carried a range of oligo-N-acetyllactosamine structures that were not seen in the colon carcinoma cell line.     

A low-level expression of human MUC1 mucin enhances lethality of murine tumor cells

We report here the development of a mouse mammary adenocarcinoma cell line containing full-length human MUC1 cDNA that can be more lethal than the parental cell line. The metastatic murine mammary adenocarcinoma cell line 410.4 was transfected with cDNA coding for a 42-tandem-repeat version of human MUC1. Two cell lines were selected, one for stable, high expression in vitro of cell-surface MUC1 (GZHi) and one for stable, low expression in vitro of cell-surface MUC1 (GZLo). Following subcutaneous challenge of CB6F1 mice with various doses of tumor cells, GZHi tumors showed loss of MUC1 expression; negligible amounts of serum MUC1 mucin were detected and the mice survived longer than mice challenged with GZLo or wild-type (410.4) tumor cells. Mice challenged with GZLo tumor cells had shorter survival times than mice challenged with either GZHi or 410.4 tumor cells. GZLo-challenged mice that showed rapidly increasing serum MUC1 mucin levels several weeks prior to death had a shorter survival than mice without detectable rising MUC1 serum levels. Surprisingly, SCID-BEIGE mice challenged with GZLo cells also survived for a shorter time than those challenged with either GZHi or 410.4 cells. This suggests that MUC1 mucin may also enhance the aggressiveness of GZLo tumors by non-immune mechanisms. Received: 30 November 1999 / Accepted: 13 March 2000     

Interaction of SOCS3 with NonO attenuates IL-1beta-dependent MUC8 gene expression

The intracellular negatively regulatory mechanism which affects IL-1β-induced MUC8 gene expression remains unclear. We found that SOCS3 overexpression suppressed IL-1β-induced MUC8 gene expression in NCI-H292 cells, whereas silencing of SOCS3 restored IL-1β-induced MUC8 gene expression. Sequentially activated ERK1/2, RSK1, and CREB by IL-1β were not affected by SOCS3, indicating that SOCS3 has an independent mechanism of action. Using immunoprecipitaion and nano LC mass analysis, we found that SOCS3 bound NonO (non-POU-domain containing, octamer-binding domain protein) in the absence of IL-1β, whereas IL-1β treatment dissociated the direct binding of SOCS3 and NonO. A dominant-negative SOCS3 mutant (Y204F/Y221F) did not bind to NonO. Interestingly, SOCS3 overexpression dramatically suppressed MUC8 gene expression in cells transfected with wild-type or siRNA of NonO. Moreover, silencing of SOCS3 dramatically increased NonO-mediated MUC8 gene expression caused by IL-1β compared to NonO overexpression alone, suggesting that SOCS3 acts as a suppressor by regulating the action of NonO.     

Changes in calcium levels in the endometrium throughout pregnancy and the role of calcium on endometrial gene expression at the time of conceptus implantation in pigs

Calcium plays an essential role in regulating many cellular functions, including proliferation, differentiation, and apoptosis. In spite of its importance in the establishment and maintenance of pregnancy, changes in calcium levels at the maternal–conceptus interface during pregnancy and its action on endometrial gene expression are not well understood. Thus, we examined changes in calcium levels in the endometrium during pregnancy, calcium deposition at the maternal–conceptus interface during pregnancy, and the role of calcium on the expression of endometrial genes related to conceptus implantation during early pregnancy in pigs. The amounts of endometrial calcium increased during mid‐ to late pregnancy, and calcium deposition was mainly localized to endometrial and chorionic epithelial cells at the maternal–conceptus interface during pregnancy and conceptus tissues during early pregnancy. The amounts of total recoverable calcium in uterine flushings were greater on Day 12 of pregnancy than Day 12 of the estrous cycle, and estrogen increased absorption of calcium ions by endometrial tissues. Increasing endometrial calcium levels by treatment with A23187, a calcium ionophore, decreased the expression of the estrogen‐responsive endometrial genes AKR1B1, ESR1, FGF7, IL1RAP, LPAR3, S100G, SPP1, and STC1 and increased the expression of genes related to prostaglandin synthesis and transport, namely PTGES, PTGS2, and SLCO5A1. These data suggest that calcium ions at the maternal–conceptus interface play a critical role in the establishment and maintenance of pregnancy in pigs by regulating the expression of endometrial genes involved in conceptus implantation, as well as the attachment of endometrial epithelial and conceptus trophectoderm/chorionic epithelial cells during pregnancy.     

Antibodies reactive with the protein core of MUC1 mucin are present in ovarian cancer patients and healthy women

 Antibodies reactive with peptide epitopes on the core protein of MUC1 epithelial mucin have been demonstrated in some patients with adenocarcinomas. Because these epitopes can be exposed on MUC1 in the serum of healthy women, we measured concentrations of MUC1-reactive antibodies in the serum of healthy pregnant and non-pregnant women, and in patients with benign and malignant ovarian tumours. Antibodies were measured in an enzyme-linked immunosorbent assay utilising a synthetic peptide corresponding to a 105-amino-acid segment of the MUC1 tandem repeat region (5.25 repeats). MUC1-reactive antibodies were always of an IgM isotype and concentrations were highest in young healthy women and declined progressively with age (P = 0.0006) concomitantly with increasing serum MUC1 levels (P = 0.003). Regardless of age, antibody levels were lower in cancer patients than in healthy women (P<0.0001), but MUC1 levels were much higher in cancer patients (P<0.0001). Although high antibody levels were associated with greater survival in ovarian cancer (P = 0.015), multivariate regression analysis showed that this was not a significant independent prognostic indicator after consideration of the International Federation of Gynaecology and Obstetrics (FIGO) stage, histological type, serum MUC1 levels and age. Serial measurement of MUC1 and MUC1 antibodies during treatment in 18 patients with ovarian cancer and throughout pregnancy in 10 women showed a negative correlation between alterations in MUC1 and MUC1 antibodies. These results show that MUC1-peptide-reactive antibodies are present in the serum of healthy women and women with cancer and that they probably form immune complexes with MUC1, but provide no evidence for an augmentation of the humoral immune response to MUC1 in ovarian cancer Received: 8 January 1998 / Accepted: 26 February 1998