Function Of MUC1 Research Articles

The MUC1–HIF-1α signaling axis regulates pancreatic cancer pathogenesis through polyamine metabolism remodeling

Dysregulation of polyamine metabolism has been implicated in cancer initiation and progression; however, the mechanism of polyamine dysregulation in cancer is not fully understood. In this study, we investigated the role of MUC1, a mucin protein overexpressed in pancreatic cancer, in regulating polyamine metabolism. Utilizing pancreatic cancer patient data, we noted a positive correlation between MUC1 expression and the expression of key polyamine metabolism pathway genes. Functional studies revealed that knockdown of spermidine/spermine N1-acetyltransferase 1 (SAT1), a key enzyme involved in polyamine catabolism, attenuated the oncogenic functions of MUC1, including cell survival and proliferation. We further identified a regulatory axis whereby MUC1 stabilized hypoxia-inducible factor (HIF-1α), leading to increased SAT1 expression, which in turn induced carbon flux into the tricarboxylic acid cycle. MUC1-mediated stabilization of HIF-1α enhanced the promoter occupancy of the latter on SAT1 promoter and corresponding transcriptional activation of SAT1, which could be abrogated by pharmacological inhibition of HIF-1α or CRISPR/Cas9-mediated knockout of HIF1A. MUC1 knockdown caused a significant reduction in the levels of SAT1-generated metabolites, N1-acetylspermidine and N8-acetylspermidine. Given the known role of MUC1 in therapy resistance, we also investigated whether inhibiting SAT1 would enhance the efficacy of FOLFIRINOX chemotherapy. By utilizing organoid and orthotopic pancreatic cancer mouse models, we observed that targeting SAT1 with pentamidine improved the efficacy of FOLFIRINOX, suggesting that the combination may represent a promising therapeutic strategy against pancreatic cancer. This study provides insights into the interplay between MUC1 and polyamine metabolism, offering potential avenues for the development of treatments against pancreatic cancer.

Visualization research on ENT1/NIS dual-function gene therapy to reverse drug resistance mediated by MUC1 in GEM-resistant pancreatic cancer

PurposeTo use bifunctional target genes to increase the intracellular transport of gemcitabine (GEM) to reverse chemotherapy resistance and to simultaneously use reporter gene imaging to localize therapeutic genes. The therapeutic effect was evaluated by [18F]FLT PET/CT to visualize the effect of gene therapy. MethodsA viral gene vector containing the pancreatic cancer-targeting promoter MUC1 for specific transcription of equilibrative nucleoside transporter 1 (ENT1) and NIS (nuclide transport channel) was employed. [125I]NaI uptake tests and [131I]NaI SPECT imaging were performed to verify the function of NIS and the target function of MUC1. The correlation between [18F]FLT uptake and GEM resistance were assessed, and the influence ENT1 and thymidine kinase 1 (TK1) expression on [18F]FLT micro-PET/CT was measured, which provides a theoretical basis for the use of [18F]FLT micro-PET/CT to evaluate the efficacy of gene therapy. ResultsFirst, functions of gene therapy were confirmed: ENT1 reversed the drug resistance of GEM-resistant pancreatic cancer cells by increasing GEM intracellular transport; MUC1 drove NIS target gene expression in pancreatic cancer; and therapeutic genes could be localized using [131I]NaI SPECT reporter gene imaging. Second, the [18F]FLT uptake ratio was affected by drug resistance and GEM treatment. The mechanism underlying this effect was related to ENT1 and TK1. Increased expression of ENT1 inhibited the expression of TK1 after GEM chemotherapy to reduce the uptake of [18F]FLT. Finally, micro-PET/CT indicated that the SUVmax of [18F]FLT could predict survival time. SUVmax exhibited an increasing trend in resistant pancreatic cancer but a trend of inhibition after upregulation of ENT1, which was more significant after GEM treatment. ConclusionsBifunctional targeted genes can localize therapeutic genes through reporter gene imaging, reverse the drug resistance of GEM-resistant pancreatic cancer and be visually evaluated through [18F]FLT micro-PET/CT.

LINC02535/miR-30a-5p/GALNT3 axis contributes to lung adenocarcinoma progression via the NF- κ B signaling pathway

ABSTRACT Long non-coding RNAs (LncRNA) play important roles in multiple types of cancers. We addressed the role of LINC02535 by regulating the miR-30a-5p /GalNAc Transferase 3 (GALNT3) axis to promote the proliferation, migration, and invasion in lung adenocarcinoma (LUAD) cells. The Cancer Genome Atlas (TCGA) database screened differentially expressed lncRNAs. Quantitative real-time PCR analysis (qRT-PCR) confirmed that LINC02535 is highly expressed in LUAD tissues and cells. In vitro experiments showed that LINC02535 promotes the proliferation, migration, and invasion of LUAD cells. A xenograft mouse model was used to show that LINC02535 promotes tumor growth in vivo. RNA immunoprecipitation (RIP) and Dual-luciferase reporter assay results confirmed that LINC02535 targets miR-30a-5p. The Vicia villosa lectin (VVA) pull-down assay indicated that MUC1 is the glycosylation target of GALNT3, and western blot verified that NF-κB is the downstream signaling pathway of MUC1. We found that LINC02535 was increased in LUAD tissues and cells, and LINC02535 was correlated with the poor prognosis of LUAD patients. miR-30a-5p acts as a tumor suppressor in LUAD by targeting GALNT3. We also demonstrated that LINC02535 might function as the sponge of miR-30a-5p to up-regulate GALNT3, and consequently promote the proliferation and metastasis of LUAD. LINC02535 acts as a competing endogenous RNA (ceRNA) to interact with miR-30a-5p, thereby upregulating the expression of GALNT3, enhancing the function of MUC1, and activating the NF-κB signaling pathway, promoting the malignant progression of LUAD cells. Abbreviations: LncRNA:long non-coding RNA; LUAD: lung adenocarcinoma; TCGA: The Cancer Genome Atlas; GALNT3: GalNAc Transferase 3; qRT-PCR: quantitative real-time PCR analysis; RIP: RNA immunoprecipitation; SPF: specific pathogen-free; VVA: Vicia villosa lectin; ceRNA: competing endogenous RNA; MiRNAs: microRNAs; FBS: fetal bovine serum; PBS: Phosphate buffered saline; CCK-8: Cell Counting Kit-8; NSCLC: non-small cell lung cancer; OC: ovarian cancer; HCC: hepatocellular carcinoma.

Advances in MUC1-Mediated Breast Cancer Immunotherapy.

Breast cancer (BRCA) is the leading cause of death from malignant tumors among women. Fortunately, however, immunotherapy has recently become a prospective BRCA treatment with encouraging achievements and mild safety profiles. Since the overexpression and aberrant glycosylation of MUC1 (human mucin) are closely associated with BRCA, it has become an ideal target for BRCA immunotherapies. In this review, the structure and function of MUC1 are briefly introduced, and the main research achievements in different kinds of MUC1-mediated BRCA immunotherapy are highlighted, from the laboratory to the clinic. Afterward, the future directions of MUC1-mediated BRCA immunotherapy are predicted, addressing, for example, urgent issues in regard to how efficient immunotherapeutic strategies can be generated.

MUC1-mediated Macrophage Activation Promotes Colitis-associated Colorectal Cancer via Activating the Interleukin-6/ Signal Transducer and Activator of Transcription 3 Axis.

Background & AimsMUC1 is abnormally expressed in colorectal cancer, including colitis-associated colorectal cancer (CAC), but its role in tumorigenesis is unclear. This study investigated MUC1’s effects in murine models of colitis and CAC and elucidated mechanisms of action.MethodsColitis and CAC were induced in mice by exposure to dextran sodium sulfate or azoxymethane plus dextran sodium sulphate. Clinical parameters, immune cell infiltration, and tumor development were monitored throughout disease progression. Experiments in knockout mice and bone marrow chimeras were combined with an exploration of immune cell abundance and function.ResultsDeficiency of Muc1 suppressed inflammation, inhibited tumor progression, increased abundance of CD8+ T lymphocytes, and reduced abundance of macrophages in colon tumors. Bone marrow chimeras showed promotion of CAC was primarily mediated by Muc1-expressing hematopoietic cells, and that MUC1 promoted a pro-tumoral immunosuppressive macrophage phenotype within tumors. Mechanistic studies revealed that Muc1 deficiency remarkably reduced interleukin-6 levels in the colonic tissues and tumors that was mainly produced by infiltrating macrophages at day 21, 42, and 85. In bone marrow-derived macrophages, MUC1 promoted responsiveness to chemoattractant and promoted activation into a phenotype with high Il6 and Ido1 expression, secreting factors which inhibited CD8+ T cell proliferation. MUC1 potently drives macrophages to produce interleukin-6, which in turn drives a pro-tumorigenic activation of signal transducer and activator of transcription 3 in colon epithelial tumor and stromal cells, ultimately increasing the occurrence and development of CAC.ConclusionsOur findings provide cellular and molecular mechanisms for the pro-tumorigenic functions of MUC1 in the inflamed colon. Therapeutic strategies to inhibit MUC1 signal transduction warrant consideration for the prevention or therapy of CAC.

Abstract P6-03-22: MUC1 oncoprotein confers trastuzumab resistance in HER2-positive breast cancer cells by maintaining cancer stem cell phenotype

Abstract Background: Although trastuzumab has greatly improved the outcome of HER2-positive breast cancer, the emergence of resistance hampers its clinical benefits. Trastuzumab resistance is a multi-factorial consequence predominantly due to the presence of cancer stem-like cells (CSCs). Interestingly, upregulation of the MUC1 gene has been reported to be associated with CSC growth, but its function in regulating CSC proliferation has not been studied in the trastuzumab-resistant (TrR) breast cancer cohort. Purpose: To evaluate the function of MUC1 in regulating cancer stem cell phenotype in TrR HER2-positive breast cancer cohort Methods 20,000 cells of each HER2-positive cell line (BT474R, T47D, HCC1954) were plated in ultralow attachment dishes and cultured in complete Mammocult Media for two weeks. Bright-field images were acquired. For CD44/CD24 staining, cells were incubated with Cy7-conjugated anti-CD44 and CF594-conujugated anti-CD24 per the previously described protocol. Cy7- and CF594-conjugated anti-mouse IgG were used as negative controls. For cell cycle analysis, cells were harvested and fixed with 70% cold ethanol for 24 H, followed by incubation with propidium iodide (PI, 50 μg/ml) and RNase (50 μg/ml) for 30 min, and analyzed by flow cytometry using Flowjo software. To silence MUC1 expression, 1 × 106 cells were transfected using the Neon electroporation system with 5 ng siMUC1 or 5 ng control siRNA vectors. The cells were electroporated for 30 ms at 1100 volts with two pulses. The cells were plated in 6-well plates with the appropriate media, incubated at 37°C for 48 hours and processed for further experiments. Results: Our results show that BT474R, the TrR cell line, forms more mammospheres and has a greater inherent CD44high/CD24low CSC population than BT474, the trastuzumab-sensitive (TrS) cell line, and that MUC1 is significantly upregulated in TrR compare to TrS HER2-positive breast cancer cells. We further demonstrate the significant inhibition of the CSC population upon silencing MUC1 expression by performing both mammosphere formation assay and CD44high/CD24low phenotype characterization and that this regulation is independent of cell cycle arrest or HER2 expression levels. Conclusion: MUC1 oncoprotein confers trastuzumab resistance in HER2-Positive breast cancer cells by maintaining cancer stem cell phenotype, indicating that it could be a potential predictive and targetable biomarker to overcome trastuzumab resistance in HER2-Positive breast cancer patients. Citation Format: Jun Yin, Andrea Sand, Mitchell Piacsek, Chaoyang Sun, Logan S. Friedrich, Richard A. Rovin, Judy A. Tjoe. MUC1 oncoprotein confers trastuzumab resistance in HER2-positive breast cancer cells by maintaining cancer stem cell phenotype [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-03-22.

Modulating MUC1 Function on T Cells

Immunotherapy is a promising approach to treating cancer. Mucin1 (MUC1), an epithelial glycoprotein, is hypo-glycosylated and overexpressed on epithelial cancers. This renders it a promising target for potential immunotherapeutic approaches. However, MUC1 has also been identified on Tcells, which might complicate its potential as a target for immunotherapies.

The Role of the Cell Surface Mucin MUC1 as a Barrier to Infection and Regulator of Inflammation.

The family of cell surface (cs-) mucins are constitutively expressed at the cell surface by nearly all epithelial cells, beneath the gel-mucin layer. All cs-mucin family members have structural features that enable them to act as a releasable decoy barrier to mucosal pathogens, by providing ligands for pathogen binding and the ability to shed the bound extracellular domain. Due to the towering structure of cs-mucins at the surface, binding of mucosal pathogens can also sterically block binding to underlying cellular receptors. The cytoplasmic tail domain of cs-mucins are capable of initiating signal transduction cascades and due to their conservation across species, may play an important biological role in cellular signaling. MUC1 is one of the most extensively studied of the cs-mucin family. With respect to its physiological function in the mucosal environment, MUC1 has been demonstrated to play a dynamic role in protection of the host from infection by a wide variety of pathogens and to regulate inflammatory responses to infection. This review briefly summarizes the current knowledge and new findings regarding the structural features relating to the function of MUC1, its role as a protective barrier against pathogen invasion and mechanisms by which this cs-mucin regulates inflammation.

MUC1 Story: Great Expectations, Disappointments and the Renaissance.

In the course of studying human mucin MUC1, the attitude towards this molecule has been changing time and again. Initially, the list of presumable functions of MUC1 was restricted to protecting and lubricating epithelium. To date, it is assumed to play an important role in cell signaling as well as in all stages of oncogenesis, from malignant cell transformation to tumor dissemination. The story of MUC1 is full of hopes and disappointments. However, the scientific interest to MUC1 has never waned, and the more profoundly it has been investigated, the clearer its hidden potential turned to be disclosed. The therapeutic potential of mucin MUC1 has already been noted by various scientific groups at the early stages of research. Over forty years ago, the first insights into MUC1 functions became a strong ground for considering this molecule as potential target for anticancer therapy. Therefore, this direction of research has always been of particular interest and practical importance. More than 200 papers on MUC1 were published in 2016; the majority of them are dedicated to MUC1-related anticancer diagnostics and therapeutics. Here we review the history of MUC1 studies from the very first attempts to reveal its functions to the ongoing renaissance.

Functional Expression of Mucin1 in Human Duodenal Adenocarcinoma

ObjectiveMucin1 (MUC1), a member of the mucin family, is a glycoprotein which is often expressed in malignant cells. However, the expression and function of MUC1 in human duodenal adenocarcinoma (DAC) has not yet been characterized because of its low frequency. Here, we examined the functional roles of core protein (MUC1-C) in DAC. Materials and methodsUsing a human duodenal cancer cell line, HuTu80, proliferation, migration, invasion, ALDH activity was assessed by cell counting kit–8, scratch wound healing, matrigel invasion, and ALDEFUOR assays, respectively. The function of MUC1 protein was evaluated with knockdown using specific siRNA as well as anti-MUC1-C peptide, GO203. MUC1 expression in human DAC was evaluated immunohistochemically in surgically resected tumors. ResultsThe positive expression of MUC1 in HuTu80 was confirmed by RT-PCR and flow cytometry. In vitro cell growth was inhibited by the addition of 50-100 μM GO203 as well as treatment with siRNA for MUC1-C. Silencing of MUC1-C also significantly reduced migration, invasion, ALDH activity. Local injection of GO-203 (14 mg/kg) significantly suppressed the growth of subcutaneous HuTu80 tumors in nude mice. Immunohistochemically, MUC1 was strongly detected in seven DAC cases, but not in 11 others. The outcome of patients with high MUC1 expression was significantly worse than those without MUC1 expression. ConclusionsThese results suggest that MUC1 is functionally associated with the malignant potential of DAC and could be a novel therapeutic target for this rare tumor.

Abstract 2697: Alterations in the HSP70 interactome are induced by overexpression of MUC1 in pancreatic cancer

Abstract Heat Shock Protein 70 (HSP70) is an evolutionarily well-conserved molecular chaperone involved in several cellular processes such as folding of proteins, modulating protein-protein interactions and transport of proteins across membranes. HSP70 works synergistically with a series of chaperones, co-chaperones, adaptors, and folding enzymes known as the HSP70 “interactome”. Previous work has demonstrated that HSP70 interactome changes can be promoted by overexpression of oncoproteins. An important “client” of HSP70 is the oncoprotein MUC1. MUC1 is overexpressed and promotes drug resistance in pancreatic cancer. We applied quantitative affinity-purification mass spectrometry (AP-MS) to characterize the HSP70 interactome differences between PC3/NEO and PC3/MUC1 cell lines. 439 HSP70-interacting proteins were identified and quantified via LC-MS/MS. Interestingly while 53% of HSP70 interactions remained constant upon MUC1 overexpression, 29% significantly increased and 18% decreased. Many of the altered proteins were key co-chaperones that regulate and maintain HSP70 activity. High levels of MUC1 promoted HSP70 association with 15 co-chaperones (HSPA5, DNAJB1, STIP1, TXNDC5, HSPB1, CCT2, TCP1, P4HB, CCT6A, CCT8, PDIA3 and HSP90B). Conversely, MUC1 overexpression triggered the loss of HSP70 interaction with only 2 co-chaperones (PPIB and DNAJA2). We are currently validating these altered interactions using an array of biochemical techniques. Our hope is that by understanding these HSP70 interactome changes, we may be able to uncover novel ways to inhibit MUC1 function in pancreatic cancer. Citation Format: . Nitika, Donald J. Wolfgeher, Pinku Mukherjee, Andrew W. Truman. Alterations in the HSP70 interactome are induced by overexpression of MUC1 in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2697.

Abstract 3140: MUC1 expression as a prognosis marker and a new therapeutic target in patient with duodenal adenocarcinoma

Abstract Background: Mucin1 (MUC1) is a glycoprotein as a member of the mucin family. The expression has been associated with poor prognosis in patients with several types of cancer. Duodenal cancer is rare, therefore details are not known including carcinogenesis and clinical treatment. We verify the association of MUC1 expression and prognosis in patient with duodenal adenocarcinoma. We also assess the function of MUC1 in vitro. Materials and Methods: Between 1989 and 2014, eighteen patients of duodenal adenocarcinoma with surgery at Jichi Medical University Hospital were included in this study. MUC1 expression was evaluated immunohistochemically with anti-MUC1 antibody to examine the association of MUC1 expression and prognosis clinicopathologically. A human-derived duodenal cancer cell line, HuTu-80, is used for the experiments of invasiveness and proliferation in vitro. The invasive capacity was evaluated by transfection of siRNA into HuTu80 with matrigel invasion assay. Viability assay with the anti-MUC1 peptide GO201 was assessed to determine whether MUC1 associate with cell growth of duodenal adenocarcinoma. Results: Seven cases were MUC1 positive and 11 were MUC1 negative immunohistochemically. TMN staging was not associated with MUC1 expression. Kaplan-Meir analysis showed a poor prognosis with MUC1 positive patients in cumulative overall survivals (MUC1 positive : MUC1 negative, 18M : 52M; HR:20.6, 95%CI 3.247-130.7,p=0.002). Lymph node metastasis of MUC1 positive patients (71.4%) was significantly higher than MUC1 negative patients (9%) (p = 0.01). In vitro experiment, the expression of MUC1 was confirmed by RT-PCR and flowcytometry. Knockdown experiment with transduction of siRNAs to HuTu80 decreased the expression of the MUC1 gene. Transduction of siRNAs significantly reduced invasive capacity (47.02±21.65%, 95%CI 3.046-102.9, p= 0.04). Growth of HuTu80 cells was inhibited by GO201 (5 μM : 95%CI 0.109-0.3565, 10μM :95%CI 0.024-0.389 p<0.0001). Conclusions: MUC1 expression is a predictive marker for poor prognosis in patients with duodenal adenocarcinoma. Functional Interference of MUC1 core protein reduces cell growth and invasiveness. Taken together, MUC1 is associated with malignant potential and a novel target for the treatment. Citation Format: Satomi Shiba, Atsushi Miki, Hideyuki Ohzawa, Takumi Teratani, Yasunaru Sakuma, Joji Kitayama, Alan Kawarai Lefor, Naohiro Sata. MUC1 expression as a prognosis marker and a new therapeutic target in patient with duodenal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3140. doi:10.1158/1538-7445.AM2017-3140

Co-expression of HER3 and MUC1 is associated with a favourable prognosis in patients with bladder cancer

To investigate the functional impact of the interaction of MUC1 with the epidermal growth factor receptors HER3 and HER4 in patients with bladder cancer. Using reverse transcription quantitative polymerase chain reaction, we examined MUC1 expression in 82 bladder cancer biopsies previously examined for the expression of HER3. Patients expressing high MUC1 had a favourable survival when the expression of HER3 was also high compared with when the expression of HER3 was low (P = 0.004). When MUC1 expression was low, HER3 co-expression did not influence the prognostic value of MUC1 (P = 0.488). MUC1 expression had no correlation with survival, tumour stage or grade, or to the prognostic value of HER4. A high MUC1 expression was associated with a favourable prognosis in patients with bladder cancer when the expression of HER3 was also high. This suggests an involvement of HER3 in MUC1 function in bladder cancer.

MUC1: A novel metabolic master regulator

MUC1, a type I transmembrane protein, is significantly overexpressed and aberrantly glycosylated in tumors of epithelial origin. By virtue of its aberrant signaling due to loss of apical–basal polarity in cancer, MUC1 regulates the metabolite flux at multiple levels. Serving as a transcriptional co-activator, MUC1 directly regulates expression of metabolic genes. By regulating receptor tyrosine kinase signaling, MUC1 facilitates production of biosynthetic intermediates required for cell growth. Also, via direct interactions, MUC1 modulates the activity/stability of enzymes and transcription factors that directly regulate metabolic functions. Additionally, by modulation of autophagy, levels of reactive oxygen species, and metabolite flux, MUC1 facilitates cancer cell survival under hypoxic and nutrient-deprived conditions. This article provides a comprehensive review of recent literature on novel metabolic functions of MUC1.

Functional polymorphism rs4072037 in MUC1 gene contributes to the susceptibility to gastric cancer: evidence from pooled 6,580 cases and 10,324 controls

Genome-wide association studies have reported a promising association of rs4072037 with gastric cancer (GC). This variant was associated with altered physiological function of MUC1 possibly by modulating promoter activity and alternative splicing of MUC1. However, the association results were inconclusive and estimate of the effect of this variant was not well evaluated. A meta-analysis by systematically reviewing relevant reports may facilitate to address these concerns. Association studies involving MUC1 rs4072037 polymorphism and GC risk were identified up to June 30, 2012. Odds ratio (OR) and 95 % confidence interval (CI) in additive model were estimated or extracted from each study. The pooled effect size was quantitatively synthesized using meta-analysis. Heterogeneity between studies was measured by the Q test and I (2) statistic, and publication bias was evaluated by a funnel plot and the Egger's test. A total of 10 independent case-control studies including 6,580 GC cases and 10,324 controls were included in this meta-analysis. Eight of the ten studies were Asian ethnicity and two European. The G allele of MUC1 rs4072037 was significantly associated with a decreased risk of GC (OR = 0.72, 95 % CI 0.68-0.77; P = 7.82 × 10(-25)), as compared with A allele. Stratification for different ethnicity, tumor localization or type showed similar results. These findings represent important evidence for association of MUC1 rs4072037 variant with GC risk, and also provide a relatively reliable estimate of effect size. MUC1 is a strong candidate as a susceptibility gene of GC.

Anticancer Property of Bromelain With Therapeutic Potential in Malignant Peritoneal Mesothelioma

Bromelain is a mixture of proteolytic enzymes that is capable of hydrolyzing glycosidic linkages in glycoprotein. Glycoprotein's are ubiquitously distributed throughout the body and serve a variety of physiologic functions. Faulty glycosylation of proteins may lead to cancer. Antitumor properties of bromelain have been demonstrated in both, in vitro and in vivo studies, along with scanty anecdotal human studies. Various mechanistic pathways have been proposed to explain the anticancer properties of bromelain. However, proteolysis by bromelain has been suggested as a main pathway by some researchers. MUC1 is a glycoprotein that provides tumor cells with invasive, metastatic, and chemo-resistant properties. To date, there is no study that examines the effect of bromelain on MUC1. However, the viability of MUC1 expressing pancreatic and breast cancer cells are adversely affected by bromelain. Further, the efficacy of cisplatin and 5-FU are enhanced by adjuvant treatment with bromelain, indicating that the barrier function of MUC1 may be affected. Other studies have also indicated that there is a greater accumulation of 5-FU in the cell compartment on treatment with 5-FU and bromelain. Malignant peritoneal mesothelioma (MPM) expresses MUC1 and initial studies have shown that the viability of MPM cells is adversely affected by exposure to bromelain. Further, bromelain in combination with either 5-FU or cisplatin, the efficacy of the chemotherapeutic drug is enhanced. Hence, current evidence indicates that bromelain may have the potential of being developed into an effective anticancer agent for MPM.

MUC1 regulates nuclear localization and function of the epidermal growth factor receptor

Alteration of protein trafficking and localization is associated with several diseases, including cystic fibrosis, breast cancer, colorectal cancer, leukemia and diabetes. Specifically, aberrant nuclear localization of the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, is a poor prognostic indicator in several epithelial carcinomas. It is now appreciated that in addition to signaling from the plasma membrane, EGFR also trafficks to the nucleus, and can directly bind the promoter regions of genes encoding cyclin D1 (CCND1) and B-Myb (MYBL2). We have previously established that loss of MUC1 in an EGFR-dependent transgenic mouse model of breast cancer correlates with the loss of cyclin D1 expression. Here, we provide evidence for a novel regulatory function of MUC1 in the trafficking and nuclear activity of EGFR. We found that MUC1 and EGFR interact in the nucleus of breast cancer cells, which promotes the accumulation of chromatin-bound EGFR. Additionally, the presence of MUC1 results in significant colocalization of EGFR and phosphorylated RNA polymerase II, indicating that MUC1 influences the association of EGFR with transcriptionally active promoter regions. Importantly, we found that the loss of MUC1 expression resulted in a decrease in the interaction between EGFR and the CCND1 promoter, which translated to a significant decrease in cyclin D1 protein expression. This data offers insights into a novel regulatory mechanism of EGFR nuclear function and could have important implications for evaluating nuclear localization in cancer.

Abstract 270: Modulation of EGFR localization and transcriptional activity

Abstract The triple negative (ER-, PR-, Her2-) or basal-like breast cancers are the most difficult forms of breast cancer to treat, because the cancer is often chemoresistant and highly metastatic. As these cancers progress from early to late stage the 5-year survival rate drops dramatically. Many proteins are responsible for this progression, including MUC1 and the Epidermal Growth Factor Receptor (EGFR). MUC1 is a heavily O-glycosylated transmembrane protein that is over expressed in 90% of all breast and ovarian cancers. In normal cells, MUC1 is only found on the apical surface of epithelium, but in cancer, MUC1 is found to be mislocalized. As a result, MUC1 plays a role in promoting tumorigenesis and metastases, by interacting with other oncogenes such as EGFR. EGFR is overexpressed in about 60% of the most aggressive form of breast cancer (triple negative). In an EGFR-dependent mouse model of breast cancer, the loss of Muc1 directly correlates to the loss of cyclin D1. Additionally, blocking MUC1 and EGFR interactions significantly inhibited tumor progression in a xenograft and s spontaneous mouse model of breast cancer. Recently, a novel trafficking pathway of EGFR has been discovered, which was described as EGFR trafficking to the nuclear compartment. Following entry into the nucleus EGFR can act in an oncogenic manner by aberrantly activating transcription of genes such as, cyclin D1 and v-myb. In this study we discovered a novel regulator function of MUC1 in EGFR trafficking and transcriptional activity. We found that MUC1 expression in basal-like breast cancer promotes the accumulation of nuclear EGFR and mediates EGFR's interaction with chromatin. Additionally, we determined that EGFR's interaction with the cyclin D1 promoter and upregulation of the cyclin D1 protein was MUC1-dependent. The main focus of anti-EGFR therapeutics have been its tyrosine kinase activity, however this study reveals that EGFR's subcellular localization should also be considered in the development of future cancer therapeutics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 270.

Frequent Expression of MUC1, a Membrane-Associated Mucin, in Adult T-Cell Leukemia Cells.

Abstract 1922Poster Board I-945Adult T-cell Leukemia (ATL), an aggressive neoplasm etiologically associated with human T-cell lymphotropic virus type-1 (HTLV-1), is resistant to anti-cancer therapies. ATL is sub-classified into 4 clinical subtypes of acute, chronic, smoldering and lymphoma and is known to have the diversity in clinico-pathological features. Mucins are high molecular weight glycoprotein expressed at the luminal surface of a variety of reproductive tract epithelia. MUC1 represents a type I transmembrane glycoprotein and often becomes highly overexpressed in epithelial cancer cells and a limited types of hematological malignant cells such as myeloma cells. Since ATL cells frequently show multi-organ invasions, we analyzed the expression profiles and the functions of MUC1 on ATL cells.We first analyzed mRNA expression of MUC1 by quantitative RT-PCR in various hematological cell lines: 8 ATL-related, 2 T-cell leukemia, 5 B-cell lineage, and 3 myeloid leukemia. All of ATL-related cell lines had quite high levels of MUC1 mRNA (4-20 folds) compare to the other cell lines. In primary ATL cells, acute-type (n=52) and chronic-type (n=12) ATL cases had significantly higher levels of MUC1 mRNA (p<0.01) compared with PBMC's from healthy donors (n=10). Flowcytometric analysis and western blotting confirmed that ATL-related cell lines and primary ATL cells had high levels of MUC1 protein.Clinical observations in solid tumor have demonstrated that high levels of MUC1 expression are indicative of a more aggressive stage in tumor progression and poor survival. Hence, although the anti-adhesive property of MUC1 has not been clearly elucidated, it have long been implicated that MUC1 on the whole cell membrane destabilize cell-cell adhesion and permit cancer cells to migrate and metastasize. The effect of MUC1 on tumor growth also has not been clearly demonstrated. We assessed prognosis between high MUC1 mRNA expression cases (n=8) and low cases (n=8) of acute-type ATL. Despite the tendency that high MUC1 mRNA expression cases had poor prognosis, there was no significant difference (p=0.33).Of note, many of ATL-related cell lines proliferate showing auto-aggregation. Among them, we focused on KK1 and KOB cells with high levels of MUC1 expression and performed knockdown experiment of MUC1 by siRNA. After 96 hours incubation, cell growth of si-MUC1 cells was repressed in comparison with si-control cells and growth inhibition in KK1 and KOB cells were approximately 30% and 25%, respectively. Next, we investigated the pattern of aggregation in KK1 and KOB cells. Interestingly, si-MUC1 cells significantly reduced aggregation after 72hours incubation in comparison with si-control cells. In the KK1 cells, si-MUC1 cells significantly reduced aggregation and the percentages of the non-aggregated cells became from 18% in si-control cells to 56%, suggesting that MUC1 expression is a key molecule for cell aggregation. Similar effects were also observed in KOB cells.We previously found that ATL cells are resistant to TRAIL though they had death-receptors and we further investigated whether MUC1 contribute to the inhibition of apoptosis. After treatment with TRAIL for 24 hours, Annexin-V positive cells of si-control cells were about 20% which increased in si-MUC1 cells to 42% in the KK1 cells. Similar effects were also observed in KOB cells. In addition, when we used a more potent apoptosis inducer MG132, si-MUC1 cells also increased the percentage of annexin-V posistive cells in KK1 and KOB cells.Consequently, we found for the first time that ATL cells had unusually high levels of MUC1 as leukemia cells both in mRNA and protein level. si-MUC1 experiments unexpectedly revealed that, in addition to cell proliferation, MUC1 contributes to the cell aggregation in a certain types of ATL cells. Furthermore, we demonstrated that MUC1 play a role in the resistance of apoptosis in ATL cells. These findings may contribute to discover unknown function of MUC1 in leukemia cells. Disclosures:No relevant conflicts of interest to declare.

Risk of gastric cancer is associated with the MUC1 568 A/G polymorphism

Identifying the genetic variants that alter MUC1 protein expression may further our understanding of the risk for development of gastric cancer (GC). We used PCR-SSPs to identify the genotype of MUC1 A/G polymorphism at its 568 site of exon 2 and immunohistochemistry to detect MUC1 protein expression in GC patients and non-cancer subjects and analyzed the association between this polymorphism and MUC1 protein expression. We found that the frequency of AA genotype was significantly high in the GC patients and the risk for GC in AA genotype carriers increased 1.81-fold. Moreover, we found a significant underexpression of MUC1 protein in GC as compared to non-cancer subjects, which was negatively correlated to AA genotype of MUC1 (r=-0.1790, P=0.004). Furthermore, this study provides a possible mechanistic insight that the MUC1 A/G polymorphism at its 568 site disrupts the physiological functions of MUC1 which is important to the physiological protection of gastric mucosa. Thus we have provided evidence that may identify the MUC1 A/G polymorphism at 568 site, as a potential genetic factor which leads to an increase in susceptibility for GC through alteration of MUC1 gene and MUC1 expression in the population that carry the A allele.