MUC1 Is Expressed by Human Skin Fibroblasts and Plays a Role in Cell Adhesion and Migration

A magnetic DNAzyme walker for both in-situ imaging and sensitive detection of MUC1 on living cells

Mucin 1 (MUC1) is a transmembrane glycoprotein commonly expressed in epithelial cells with stable levels and polarized distribution. Their expression levels and spatial distribution abnormally altered during oncogenesis and play tumor-promoting roles synergistically. We herein propose a magnetic DNAzyme walker (MDW) for both in-situ imaging and sensitive detection of MUC1. This MDW was constructed by modifying specially designed track strands (TSs) and walking strands (WSs) on a streptavidin magnetic bead (SA-MB). The TSs contained cleavage sites for DNAzymes and were labeled with Cy3 at free ends. The WSs contained DNAzyme sequences and were firstly blocked by hybridizing with Cy5-labeled aptamers of MUC1. The DNAzymes were unlocked upon aptamers binding to MUC1 on cells. MDWs were then transferred to a buffer suitable for DNAzyme action, where the unlocked DNAzymes cleaved multiple TSs, releasing amplified Cy3-fragments, which were separated from the uncleaved ones by magnetic separation. In-situ imaging of MUC1 were achieved by the fluorescence of Cy5 on aptamers bound to MUC1. Sensitive detection of MUC1 were achieved by the amplified fluorescence of released Cy3. In-situ imaging and walker operation for detection were triggered by the same targets at the same time, ensuring the signals are real-time correlative. Moreover, MDWs' operation was separated from cells, reducing interference between imaging and detection. The proposed MDW offers a potential approach for comprehensive analysis of MUC1 in early diagnosis and progression assessment of tumor.

Facile, rapid and efficient isolation of circulating tumor cells using aptamer-targeted magnetic nanoparticles integrated with a microfluidic device

Facile and sensitive detection and isolation of circulating tumor cells (CTCs) was achieved using the aptamer-targeted magnetic nanoparticles (Apt-MNPs) in conjugation with a microfluidic device. Apt-MNPs were developed by the covalent attachment of anti-MUC1 aptamer to the silica-coated magnetic nanoparticles via the glutaraldehyde linkers. Apt-MNPs displayed high stability and functionality after 6 months of storage at 4 °C. The specific microfluidic device consisting of mixing, sorting and separation modules was fabricated through conventional photo- and soft-lithography by using polydimethylsiloxane. The capture efficiency of Apt-MNPs was first studied in vitro on MCF-7 and MDA-MB-231 cancer cell lines in the bulk and microfluidic platforms. The cell capture yields of more than 91% were obtained at the optimum condition after 60 minutes of exposure to 50 μg mL-1 Apt-MNPs with 10 to 106 cancer cells in different media. CTCs were also isolated efficiently from the blood samples of breast cancer patients and successfully propagated in vitro. The isolated CTCs were further characterized using immunofluorescence staining. The overall results indicated the high potential of the present method for the detection and capture of CTCs.

The mucin protein MUCL1 regulates melanogenesis and melanoma genes in a manner dependent on threonine content

Background

The regulation of melanogenesis has been investigated as a long‐held aim for pharmaceutical manipulations with denotations for malignancy of melanoma. Mucins have a protective function in epithelial organs; however, in the most outer organ, the skin, the role of mucins has not been studied enough.

Objectives

Our initial hypothesis developed from the identification of correlations between pigmentation and expressions of skin mucins, particularly those existing in skin tissue. We aimed to investigate the action of mucins in human melanocytic cells.

Materials and methods

The expression of mucin proteins in human skin was investigated using microarray data from the Human Protein Atlas consortium (HPA) and the Genotype‐Tissue Expression consortium (GTEx) database. Mucin expression was measured at RNA and protein levels in melanoma cells. The findings were further validated and confirmed by analysis of independent experiments.

Results

We found that the several mucin proteins showed expression in human skin cells and among these, mucin‐like protein 1 (MUCL1) showed the highest expression and also clear negative correlation with melanogenesis in epidermal melanocytes. We confirmed the correlations between melanogenesis and MUCL1 by revealing negative correlations in melanocytes with different melanin production, resulting from increased composition of threonine, mucin‐conforming amino acid, and increased autophagy‐related forkhead‐box O signalling. Furthermore, threonine itself affects melanogenesis and metastatic activity in melanoma cells.

Conclusions

We identified a significant association between MUCL1 and threonine with melanogenesis and metastasis‐related genes in melanoma cells. Our results define a novel mechanism of mucin regulation, suggesting diagnostic and preventive roles of MUCL1 in cutaneous melanoma.

Whatis already known about this topic?

Despite considerable advances in radioactive therapeutics or chemotherapeutic approaches for the treatment of abnormal melanogenesis, there are still many caveats to delivery, effectiveness and safety, thus leaving a necessity for more immediate pharmaceutical targets.

Mucins have protective and chemical barrier functions in epithelial organs; however, in the skin, mucin has scarce expression and is known only as a diagnostic aid in skin disorders such as mucinosis.

Whatdoes this study add?

We provide detailed analysis demonstrating the potential of mucin‐like protein 1 (MUCL1), which showed negative correlations in melanocytes with different melanin production, resulting from increased composition of threonine and increased autophagy‐related forkhead‐box O signalling in epidermal melanocytes and melanoma cells.

We established that through an alternative pathway for MUCL1 biosynthesis, threonine supplementation recovers MUCL1 levels in melanoma. Changes, brought on by the essential amino acid threonine, resulted in substantial modulations in melanogenesis and reduced metastasis‐related genes.

Whatis the translational message?

This study demonstrates for the first time that the mucin protein of skin cells is compounded by distorted mucin homeostasis, with major effects on melanogenesis and metastasis‐related genes in melanoma.

We anticipate that these novel findings will be of keen interest to the community of scientists and medical practitioners examining skin dysfunction.

Linked Comment: C. Casalou and D.J. Tobin. Br J Dermatol 2022; 186:388–389.

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Differential gene expression identifies KRT7 and MUC1 as potential metastasis-specific targets in sarcoma

BACKGROUND

Despite numerous discoveries regarding the molecular genesis and progression of primary cancers, the biology of metastasis remains poorly understood. Compared to very large numbers of circulating tumor cells that are now known to accompany nearly all cancers, a relatively limited number of lesions actually develop in most patients with metastases. We hypothesized that phenotypic changes driven by differential gene expression in a finite subpopulation of tumor cells render those cells capable of metastasis and sought to identify key pathways through analysis of gene expression in primary and metastatic lesions from the same patients.

METHODS

We compared whole-genome expression in 4 matched samples of primary and metastatic sarcoma, then evaluated candidate genes with differential expression via quantitative PCR in 30 additional matched sets, tumor tissue immunostaining, siRNA loss-of-function in a sarcoma cell migration assay, and clinical correlation with overall and disease-free survival after metastasectomy.

RESULTS

Comparison of microarray signals identified differential expression of cell adhesion genes, including upregulation of KRT7 and MUC1 in metastases; KRT7 and MUC1 upregulation was confirmed in 22 (73%) and 20 (67%) matched sets of metastatic/primary tumors, respectively. Silencing of KRT7 and MUC1 via targeted siRNAs suppressed sarcoma cell migration in vitro, and a significant correlation (two-sided) was observed between both KRT7 and MUC1 expression in metastases and overall patient survival.

CONCLUSION

KRT7 and MUC1 may play a significant role in enabling sarcoma metastasis, and they may therefore be important prognostic biomarkers as well as potential targets for therapeutic prevention of metastasis.

Immunolocalization of MUC1 in chronic plaque psoriasis

Psoriasis is a chronic skin inflammatory disease with immunological, hyperproliferative and angiogenic dysfunction. MUC1 is a molecular sensor and signal transductor that responds to external stimuli generating cellular responses, which include cell proliferation, growth, differentiation, migration, invasion, survival and secretion of growth factors, and cytokines. The current study aimed at evaluation of the possible role of MUC1 in the pathogenesis of psoriasis through its immunohistochemical localization in involved and uninvolved psoriatic skin compared to normal skin in addition of correlating MUC1 expression with the clinical and pathological parameters of psoriasis. The current study investigated 30 patients with psoriasis and 10 controls. MUC1 was expressed in epidermis in 30% of normal skin compared to 20% of uninvolved epidermis and 63.3% of involved epidermis of psoriatic skin. MUC1 was seen staining endothelial cells of capillaries and inflammatory cells in dermis in 10% of normal skin, 0% of uninvolved psoriasis, and 83.3% of involved psoriasis. Dermal expression of MUC1 in psoriasis was associated with mild to moderate degrees of epidermal acanthosis (p = .027). Intense MUC1 expression by psoriatic epidermis was associated with short disease duration (p = .044). The upregulation of MUC1 in involved psoriatic lesion compared to uninvolved and normal skin may suggest MUC1 role in pathogenesis of psoriasis especially early stages. MUC1 may be responsible for less severity of psoriasis in old aged patients.

MUC1: The First Respiratory Mucin with an Anti-Inflammatory Function

MUC1 is a membrane-bound mucin expressed on the apical surfaces of most mucosal epithelial cells. In normal lung epithelia, MUC1 is a binding site for Pseudomonas aeruginosa, an opportunistic human pathogen of great clinical importance. It has now been established that MUC1 also serves an anti-inflammatory role in the airways that is initiated late in the course of a bacterial infection and is mediated through inhibition of Toll-like receptor (TLR) signaling. MUC1 expression was initially shown to interfere with TLR5 signaling in response to P. aeruginosa flagellin, but has since been extended to other TLRs. These new findings point to an immunomodulatory role for MUC1 during P. aeruginosa lung infection, particularly during the resolution phase of inflammation. This review briefly summarizes the recent characterization of MUC1’s anti-inflammatory properties in both the respiratory tract and extrapulmonary tissues.

Muc1 knockout potentiates murine lung carcinogenesis involving an epiregulin-mediated EGFR activation feedback loop

Mucin 1 (MUC1) is a tumor antigen that is aberrantly overexpressed in various cancers, including lung cancer. Our previous in vitro studies showed that MUC1 facilitates carcinogen-induced EGFR activation and transformation in human lung bronchial epithelial cells (HBECs), which along with other reports suggests an oncogenic property for MUC1 in lung cancer. However, direct evidence for the role of MUC1 in lung carcinogenesis is lacking. In this study, we used the 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced A/J mouse lung tumor model to investigate the effect of whole-body Muc1 knockout (KO) on carcinogen-induced lung carcinogenesis. Surprisingly, lung tumor multiplicity was significantly increased in Muc1 KO compared to wild-type (WT) mice. The EGFR/AKT pathway was unexpectedly activated, and expression of the EGFR ligand epiregulin (EREG) was increased in the lung tissues of the Muc1 KO compared to the WT mice. EREG stimulated proliferation and protected against cigarette smoke extract (CSE)-induced cytotoxicity in in vitro cultured human bronchial epithelial cells. Additionally, we determined that MUC1 was expressed in human fibroblast cell lines where it suppressed CSE-induced EREG production. Further, suppression of MUC1 cellular activity with GO-201 enhanced EREG production in lung cancer cells, which in turn protected cancer cells from GO-201-induced cell death. Moreover, an inverse association between MUC1 and EREG was detected in human lung cancer, and EREG expression was inversely associated with patient survival. Together, these results support a promiscuous role of MUC1 in lung cancer development that may be related to cell-type specific functions of MUC1 in the tumor microenvironment, and MUC1 deficiency in fibroblasts and malignant cells results in increased EREG production that activates the EGFR pathway for lung carcinogenesis.

Origin of anti-tumor activity of the cysteine-containing GO peptides and further optimization of their cytotoxic properties

Antitumor GO peptides have been designed as dimerization inhibitors of prominent oncoprotein mucin 1. In this study we demonstrate that activity of GO peptides is independent of the level of cellular expression of mucin 1. Furthermore, these peptides prove to be broadly cytotoxic, causing cell death also in normal cells such as dermal fibroblasts and endometrial mesenchymal stem cells. To explore molecular mechanism of their cytotoxicity, we have designed and tested a number of new peptide sequences containing the key CxC or CxxC motifs. Of note, these sequences bear no similarity to mucin 1 except that they also contain a pair of proximal cysteines. Several of the new peptides turned out to be significantly more potent than their GO prototypes. The results suggest that cytotoxicity of these peptides stems from their (moderate) activity as disulfide oxidoreductases. It is expected that such peptides, which we have termed DO peptides, are involved in disulfide-dithiol exchange reaction, resulting in formation of adventitious disulfide bridges in cell proteins. In turn, this leads to a partial loss of protein function and rapid onset of apoptosis. We anticipate that coupling DO sequences with tumor-homing transduction domains can create a potentially valuable new class of tumoricidal peptides.