ALCAM regulates motility, invasiveness, and adherens junction formation in uveal melanoma cells

Inhibition of miR-214 expression by small molecules alleviates head and neck cancer metastasis by targeting ALCAM/TFAP2 signaling

Predominantly, head and neck cancer (HNC) is considered a regional disease and develops in the nasal cavity, oral cavity, tongue, pharynx, and larynx. In the advanced stage, the HNC spread into distant organs. By the time head and neck cancer diagnosed, the estimated metastasis is occurred in 10-40% cases. The most important vital organs affected by distant metastasis are the lungs, bones, and liver. Despite several advancements in chemotherapies, no significant changes are observed as 5-year survival rate remains the same. Therefore, it is crucial to decipher molecular mechanisms contributing to the metastatic dissemination of head and neck cancer. Here, we tested a novel ALCAM/TFAP2 signaling by targeting multidisciplinary miR-214 expression in head and cancer cells. Our results revealed that HNC cell lines (CAL27, SCC-9, SCC-4, and SCC-25) exhibit higher expression of miR-214 compared with normal human bronchial epithelial (NHBE) cells. Higher expression of miR-214 drives the invasive potential of these cell lines. Down-regulation of miR-214 in CAL27 and SCC-9 cells either using an anti-miR-214 inhibitor (50nM) or a small molecule of green tea (EGCG) inhibited cell invasion. Treating CAL27 and SCC-9 cells with EGCG also reduces ALCAM expression, a key activated leukocyte cell adhesion molecule, potentially blocking mesenchymal phenotype. Dietary administration of EGCG significantly inhibits distant metastasis of SCC-9 cells into the lungs, liver, and kidneys. Our results also demonstrate that the reduction of miR-214 expression influences in vitro cell movement and extravasation, as evident by reduced CD31 expression, a neovascularization marker. Together, these studies suggest that identifying bioactive molecules that can inhibit distant metastasis regulated by the miRNAs may provide potent interventional approaches and a better understanding of the complex functions of miRNAs and their therapeutic targets for clinical application.

Prognostic and Functional Analysis of NPY6R in Uveal Melanoma Using Bioinformatics

Neuropeptides can mediate tumor cell proliferation and differentiation through autocrine, paracrine, neurosecretory, and endocrine mechanisms. This study investigated the expression and prognostic significance of neuropeptide Y receptor Y6 (NPY6R) in uveal melanoma (UVM) and preliminarily investigated the biological function of NPY6R in UVM. NPY6R was poorly expressed in most tumors and was associated with better prognosis in UVM. Among the clinicopathological features of UVM, NPY6R expression was lower in male patients. The area under the curve (AUC) value of NPY6R for the diagnosis of UVM was 0.676 (95% CI: 0.556–0.795). A nomogram including four clinical predictors was constructed. NPY6R expression was significantly associated with features of the UVM immune microenvironment. ESTIMATE and CIBERSORT algorithms were used to calculate the fraction of immune cells and the percentage of infiltration in each patient, respectively. NPY6R expression-related gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analyses were performed. GO and KEGG enrichment analyses revealed that NPY6R-related genes are mainly enriched in pathways and functions related to visual light perception. Gene set enrichment analysis suggested that NPY6R is associated with tumor progression in UVM. NPY6R is involved in the tumor progression of UVM and has a good predictive value as a prognostic marker of UVM.

miRNA-148b and its role in various cancers

miRNA-148b belongs to the family miR-148/-152, with significant differences in nonseed sequences, which can target diverse mRNA molecules. Reportedly, it may undergo deregulation in lung and ovarian cancers and downregulation in gastric, pancreatic and colon cancers. However, there is a need for further studies to better characterize its mechanism of action and in different types of cancer. In this review, we focus on the aberrant expression of miR-148b in different cancer types and highlight its main target genes and signaling pathways, as well as its pathophysiologic role and relevance to tumorigenesis in several types of cancer.

The Clinical and Theranostic Values of Activated Leukocyte Cell Adhesion Molecule (ALCAM)/CD166 in Human Solid Cancers

Simple Summary

ALCAM (activated leukocyte cell adhesion molecule) is an important regulator in human cancers, particularly solid tumours. Its expression in cancer tissues has prognostic values depending on cancer types and is also linked to distant metastases. A truncated form, soluble form of ALCAM (sALCAM) in circulation has been suggested to be a prognostic indicator and a potential therapeutic tool. This article summarises recent findings and progress in ALCAM and its involvement in cancer, with a primary focus on its clinical connections and therapeutic values.

Abstract

Activated leukocyte cell adhesion molecule (ALCAM), also known as CD166, is a cell adhesion protein that is found in multiple cell types. ALCAM has multiple and diverse roles in various physiological and pathological conditions, including inflammation and cancer. There has been compelling evidence of ALCAM’s prognostic value in solid cancers, indicating that it is a potential therapeutic target. The present article overviews the recent findings and progress in ALCAM and its involvement in cancer, with a primary focus on its clinical connections in cancer and therapeutic values.

Multifaceted effects of soluble human CD6 in experimental cancer models

Background

CD6 is a lymphocyte surface co-receptor physically associated with the T-cell receptor (TCR)/CD3 complex at the center of the immunological synapse. There, CD6 assists in cell-to-cell contact stabilization and modulation of activation/differentiation events through interaction with CD166/ALCAM (activated leukocyte cell adhesion molecule), its main reported ligand. While accumulating evidence is attracting new interest on targeting CD6 for therapeutic purposes in autoimmune disorders, little is known on its potential in cancer. In an attempt to elucidate the in vivo relevance of blocking CD6-mediated interactions in health and disease, we explored the consequences of expressing high circulating levels of a soluble form CD6 (sCD6) as a decoy receptor.

Methods

High sCD6 serum levels were achieved by using transgenic C57BL/6 mice expressing human sCD6 under the control of lymphoid-specific transcriptional elements (shCD6LckEμTg) or wild type either transduced with hepatotropic adeno-associated virus coding for mouse sCD6 or undergoing repeated infusions of recombinant human sCD6 protein. Characterization of sCD6-induced changes was performed by ex vivo flow cytometry and functional analyses of mouse lymphoid organ cells. The in vivo relevance of those changes was explored by challenging mice with subcutaneous or metastatic tumors induced by syngeneic cancer cells of different lineage origins.

Results

Through a combination of in vitro and in vivo studies, we show that circulating sCD6 expression induces defective regulatory T cell (Treg) generation and function, decreased CD166/ALCAM-mediated tumor cell proliferation/migration and impaired galectin-induced T-cell apoptosis, supporting the fact that sCD6 modulates antitumor lymphocyte effector function and tumorigenesis. Accordingly, sCD6 expression in vivo resulted in delayed subcutaneous tumor growth and/or reduced metastasis on challenge of mice with syngeneic cancer cells.

Conclusions

Evidence is provided for the disruption of CD6 receptor–ligand interactions as a feasible immunomodulatory approach in cancer.

Biological characteristics of endometriotic mesenchymal stem cells isolated from ectopic lesions of patients with endometriosis

BACKGROUND

Research into the pathogenesis of endometriosis (EMs) would substantially promote its effective treatment and early diagnosis. However, the aetiology of EMs is poorly understood and controversial despite the progress in EMs research in the last several decades. Currently, accumulating evidence has shed light on the importance of endometrial stem cells (EnSCs) residing in the basal layer of endometrium in the establishment and progression of endometriotic lesions. Therefore, we aimed to identify the differences between EnSCs isolated from the ectopic lesions of EMs patients (EnSC-EM-EC) and EnSCs isolated from eutopic endometrium of control group (EnSC-Control). We further performed preliminary exploration of the potential signalling pathways involved in the above abnormalities.

METHODS

EnSC-EM-EC (n = 12) and EnSC-Control (n = 13) were successfully isolated. Then, the proliferative capacity, migratory capacity and angiogenic potential of EnSCs were evaluated by conventional MTT assay, flow cytometry, wound healing assay, transwell assay, tube formation assay and chick embryo chorioallantoic membrane assay respectively. The expression of 11 angiogenesis-associated biological factors and 11 cytokines secreted by EnSCs and 17 adhesion molecules expressed on EnSCs were determined by protein array assays respectively. Differentially expressed genes (DEGs) between EnSC-EM-EC and EnSC-Control were analysed by RNA-sequence.

RESULTS

EnSC-EM-EC exhibited unique biological characteristics, including prolonged mitosis, enhanced migratory capacity and enhanced angiogenic potential. Greater amounts of angiogenic factors (especially VEGF and PDGF) were secreted by EnSC-EM-EC than by EnSC-Control; however, the distinct profiles of cytokines secreted by EnSC-EM-EC and adhesion molecules expressed by EnSC-EM-EC require further investigation. A total of 523 DEGs between EnSC-EM-EC and EnSC-Control were identified and analysed using the KEGG and Gene Ontology databases.

CONCLUSIONS

Our results not only improve the understanding of EMs but also contribute to the development of EnSC-EM-EC as a tool for EMs drug discovery. These cells could be of great help in exploiting promising therapeutic targets and new biomarkers for EMs treatment and prognosis.

CD166high Uveal Melanoma Cells Represent a Subpopulation With Enhanced Migratory Capacity

Purpose

Cancer stem cells (CSCs) are a subpopulation of cells with the capacity to drive tumor growth. While there is evidence of the existence of CSCs in uveal melanoma (UM), there is no consensus on their defining markers. In this study, we examined putative CSC markers in UM cell lines, primary UM (PUM), and normal choroidal melanocytes (NCM).

Methods

Nonadherent sphere assays were used to assess the tumorigenic potential of 15 PUMs, 8 high (M3) and 7 low (D3) metastatic risk. Flow cytometry was used to compare the expression of CSC markers between 10 PUMs and 4 NCMs, as well as in 8 UM cell lines grown under adherent and nonadherent conditions. Based on the data generated and from TCGA analyses, CD166 was investigated in detail, including its effect on cell migration using a tumor transendothelial migration assay.

Results

M3 PUM had a greater melanosphere-forming efficiency than D3 PUM. CD166 and Nestin expression was upregulated in PUM compared to NCM by flow cytometry. UM cell lines resistant to anoikis had increased levels of CD271, Nestin, and CD166 compared with adherent cells. TCGA analysis showed that patients with higher CD166 expression had a poorer prognosis: this was supported by a Mel270 CD166high subpopulation that had enhanced migratory capabilities compared with CD166low cells. IHC showed that CD166 is expressed in the cytoplasm and cell membrane of PUM cells.

Conclusions

UM contain a population of cells with characteristics of CSCs. In particular, CD166high UM cells appear to represent a subpopulation with enhanced migratory capacity.

Decreased ALCAM expression and promoter hypermethylation is associated with preeclampsia

Preeclampsia (PE) is a major obstetrical complication that results in maternal and fetal morbidity and mortality. Aberrant epigenetic modifications are widely involved in the pathogenesis of PE. Previously, the activated leukocyte cell adhesion molecule (ALCAM) was reported to be required for blastocyst implantation but has not been described in the context of pathological pregnancy. This study explored the expression of ALCAM and its methylation levels in the placentas and peripheral venous blood of patients with PE from a Chinese Han population. The mRNA and protein expression levels of ALCAM were downregulated in the PE placentas compared with the control placentas (P < 0.05). The methylation rate of the ALCAM gene promoter was considerably elevated in the placentas (P = 0.003, odds ratio (OR) = 0.264, 95% confidence interval (95% CI) [0.108-0.647], cases n = 47, controls n = 53) and peripheral blood (P = 0.007, OR = 0.455, 95% CI [0.256-0.806], cases n = 100, controls n = 100) of the PE patients compared with those of the normotensive women, suggesting a negative relationship between ALCAM methylation and gene transcription. Moreover, the transcriptional expression of ALCAM was dramatically increased by demethylating treatment in trophoblastic cells. ALCAM is expected to be involved in the pathogenesis of PE through methylation regulation.

Syntenin: PDZ Protein Regulating Signaling Pathways and Cellular Functions

Syntenin is an adaptor-like molecule that has two adjacent tandem postsynaptic density protein 95/Discs large protein/Zonula occludens 1 (PDZ) domains. The PDZ domains of syntenin recognize multiple peptide motifs with low to moderate affinity. Many reports have indicated interactions between syntenin and a plethora of proteins. Through interactions with various proteins, syntenin regulates the architecture of the cell membrane. As a result, increases in syntenin levels induce the metastasis of tumor cells, protrusion along the neurite in neuronal cells, and exosome biogenesis in various cell types. Here, we review the updated data that support various roles for syntenin in the regulation of neuronal synapses, tumor cell invasion, and exosome control.

Maternal high-fat diet exposure during gestation, lactation, or gestation and lactation differentially affects intestinal morphology and proteome of neonatal mice

Offspring nutrition depends on the mother during gestation and lactation; thus, maternal nutrition and metabolism can affect their development. We hypothesized that maternal exposure to high-fat (HF) diet affects neonate's gastrointestinal tract development. Our objective was to determine the effect of maternal HF diet during gestation and lactation on neonate's duodenum histomorphology and proteome. Female mice were fed either a control (C, 10% kcal fat) or an HF (60% kcal fat) diet for 4 weeks and bred. On postnatal day 2, half the pups were cross-fostered to dams fed on different diet, creating 4 treatments: C-C, C-HF, HF-C, and HF-HF, indicating maternal diet during gestation-lactation, respectively. On postnatal day 12, pups' duodenum was excised and prepared for histology and liquid chromatography-tandem mass spectrometry analysis of proteome. Villi were significantly longer in HF-HF pups, and crypt cell proliferation rate was not different among treatments. Between C-C and HF-HF, HF-C, or C-HF, 812, 601, or 894 proteins were differentially expressed (Tukey adjusted P < .05), respectively. Functional analysis clustered proteins upregulated in HF-HF vs C-C in fat digestion and absorption, extracellular matrix, cell adhesion, immune response, oxidation-reduction processes, phagocytosis, and transport categories. Proteins downregulated were classified as RNA splicing, translation, protein folding, endocytosis, and transport. There was evidence for a carryover effect of exposure to HF diet during gestation to the postnatal period. Alterations in proteome relative to HF exposure potentially reflect long-term changes in the functioning of the duodenum.

VE-cadherin RGD motifs promote metastasis and constitute a potential therapeutic target in melanoma and breast cancers

We have investigated the role of vascular-endothelial (VE)-cadherin in melanoma and breast cancer metastasis. We found that VE-cadherin is expressed in highly aggressive melanoma and breast cancer cell lines. Remarkably, inactivation of VE-cadherin triggered a significant loss of malignant traits (proliferation, adhesion, invasion and transendothelial migration) in melanoma and breast cancer cells. These effects, except transendothelial migration, were induced by the VE-cadherin RGD motifs. Co-immunoprecipitation experiments demonstrated an interaction between VE-cadherin and α2β1 integrin, with the RGD motifs found to directly affect β1 integrin activation. VE-cadherin-mediated integrin signaling occurred through specific activation of SRC, ERK and JNK, including AKT in melanoma. Knocking down VE-cadherin suppressed lung colonization capacity of melanoma or breast cancer cells inoculated in mice, while pre-incubation with VE-cadherin RGD peptides promoted lung metastasis for both cancer types. Finally, an in silico study revealed the association of high VE-cadherin expression with poor survival in a subset of melanoma patients and breast cancer patients showing low CD34 expression. These findings support a general role for VE-cadherin and other RGD cadherins as critical regulators of lung and liver metastasis in multiple solid tumours. These results pave the way for cadherin-specific RGD targeted therapies to control disseminated metastasis in multiple cancers.

Shed urinary ALCAM is an independent prognostic biomarker of three-year overall survival after cystectomy in patients with bladder cancer

Proteins involved in tumor cell migration can potentially serve as markers of invasive disease. Activated Leukocyte Cell Adhesion Molecule (ALCAM) promotes adhesion, while shedding of its extracellular domain is associated with migration. We hypothesized that shed ALCAM in biofluids could be predictive of progressive disease. ALCAM expression in tumor (n = 198) and shedding in biofluids (n = 120) were measured in two separate VUMC bladder cancer cystectomy cohorts by immunofluorescence and enzyme-linked immunosorbent assay, respectively. The primary outcome measure was accuracy of predicting 3-year overall survival (OS) with shed ALCAM compared to standard clinical indicators alone, assessed by multivariable Cox regression and concordance-indices. Validation was performed by internal bootstrap, a cohort from a second institution (n = 64), and treatment of missing data with multiple-imputation. While ALCAM mRNA expression was unchanged, histological detection of ALCAM decreased with increasing stage (P = 0.004). Importantly, urine ALCAM was elevated 17.0-fold (P < 0.0001) above non-cancer controls, correlated positively with tumor stage (P = 0.018), was an independent predictor of OS after adjusting for age, tumor stage, lymph-node status, and hematuria (HR, 1.46; 95% CI, 1.03–2.06; P = 0.002), and improved prediction of OS by 3.3% (concordance-index, 78.5% vs. 75.2%). Urine ALCAM remained an independent predictor of OS after accounting for treatment with Bacillus Calmette-Guerin, carcinoma in situ, lymph-node dissection, lymphovascular invasion, urine creatinine, and adjuvant chemotherapy (HR, 1.10; 95% CI, 1.02–1.19; P = 0.011). In conclusion, shed ALCAM may be a novel prognostic biomarker in bladder cancer, although prospective validation studies are warranted. These findings demonstrate that markers reporting on cell motility can act as prognostic indicators.

A Combination of Species Identification and STR Profiling Identifies Cross-contaminated Cells from 482 Human Tumor Cell Lines

Human tumor cell lines are extremely important tools for cancer research, but a significant percentage is cross-contaminated with other cells. Short tandem repeat (STR) profiling is the prevailing standard for authenticating cell lines that originate from human tissues. Based on the analysis of 482 different human tumor cell lines used in China by STR, up to 96 cell lines were misidentified. More importantly, the study has found that STR profiling alone is insufficient to exclude inter-species cross-contamination of human cell lines. Among the 386 cell lines which had a correct STR profile, 3 of them were inter-species cross-contaminated. Careful microscopic examination may be helpful in some cases to detect changes in morphology but additional testing is needed. Additionally, species verification by PCR could easily identify the contaminants, even with a low percentage of contaminating cells. Combining STR profiling with species identification by PCR, more than 20.5% (99/482) of tumor cell lines were revealed as having been incorrectly identified, including intra-species (14.5%), inter-species (4.4%) cross-contamination and contaminating cell lines (1.7%). Therefore, quality control of cell lines is a systemic issue. Each cell line should undergo a full QA (Quality Assurance) assessment before it is used for research.

Stromal Expression of Activated Leukocyte Cell Adhesion Molecule Promotes Lung Tumor Growth and Metastasis

Activated leukocyte cell adhesion molecule (ALCAM) is expressed on various cell types, including leukocytes, endothelial cells, and certain tumor cells. Although ALCAM expression on tumor cells has been linked to tumor invasion and metastatic spread, the contribution of ALCAM expressed in cells forming the tumor stroma to cancer progression has not been investigated. In this study, ALCAM-deficient (ALCAM^-/-) mice were used to evaluate the role of ALCAM in lung tumor growth and metastasis. ALCAM^-/- mice displayed an altered blood vascular network in the lung and the diaphragm, indicative of an angiogenetic defect. The absence of ALCAM expression in cells forming the stromal tumor microenvironment profoundly affected lung tumor growth in three different i.v. metastasis models. In the case of Lewis lung carcinoma (LLC), an additional defect in tumor cell homing to the lungs and a resulting reduction in the number of lung tumor nodules were observed. Similarly, when LLC cells were implanted subcutaneously for the study of spontaneous tumor cell metastasis, the rate of LLC metastasis to the lungs was profoundly reduced in ALCAM^-/- mice. Taken together, our work demonstrates for the first time the in vivo contribution of ALCAM to angiogenesis and reveals a novel role of stromally expressed ALCAM in supporting tumor growth and metastatic spread.

Extracellular protonation modulates cell-cell interaction mechanics and tissue invasion in human melanoma cells

Detachment of cells from the primary tumour precedes metastatic progression by facilitating cell release into the tissue. Solid tumours exhibit altered pH homeostasis with extracellular acidification. In human melanoma, the Na⁺/H⁺ exchanger NHE1 is an important modifier of the tumour nanoenvironment. Here we tested the modulation of cell-cell-adhesion by extracellular pH and NHE1. MV3 tumour spheroids embedded in a collagen matrix unravelled the efficacy of cell-cell contact loosening and 3D emigration into an environment mimicking physiological confinement. Adhesive interaction strength between individual MV3 cells was quantified using atomic force microscopy and validated by multicellular aggregation assays. Extracellular acidification from pH_e7.4 to 6.4 decreases cell migration and invasion but increases single cell detachment from the spheroids. Acidification and NHE1 overexpression both reduce cell-cell adhesion strength, indicated by reduced maximum pulling forces and adhesion energies. Multicellular aggregation and spheroid formation are strongly impaired under acidification or NHE1 overexpression. We show a clear dependence of melanoma cell-cell adhesion on pH_e and NHE1 as a modulator. These effects are opposite to cell-matrix interactions that are strengthened by protons extruded via NHE1. We conclude that these opposite effects of NHE1 act synergistically during the metastatic cascade.

ALCAM is a Novel Cytoplasmic Membrane Protein in TNF-α Stimulated Invasive Cholangiocarcinoma Cells

BACKGROUND

Cholangiocarcinoma (CCA), or bile duct cancer, is incurable with a high mortality rate due to a lack of effective early diagnosis and treatment. Identifying cytoplasmic membrane proteins of invasive CCA that facilitate cancer progression would contribute toward the development of novel tumor markers and effective chemotherapy.

MATERIALS AND METHODS

An invasive CCA cell line (KKU-100) was stimulated using TNF-α and then biotinylated and purified for mass spectrometry analysis. Novel proteins expressed were selected and their mRNAs expression levels were determined by real-time RT-PCR. In addition, the expression of ALCAM was selected for further observation by Western blot analysis, immunofluorescent imaging, and antibody neutralization assay.

RESULTS

After comparing the proteomics profile of TNF-α induced invasive with non-treated control cells, over-expression of seven novel proteins was observed in the cytoplasmic membrane of TNF-α stimulated CCA cells. Among these, ALCAM is a novel candidate which showed significant higher mRNA- and protein levels. Immunofluorescent assay also supported that ALCAM was expressed on the cell membrane of the cancer, with increasing intensity associated with TNF-α.

CONCLUSIONS

This study indicated that ALCAM may be a novel protein candidate expressed on cytoplasmic membranes of invasive CCA cells that could be used as a biomarker for development of diagnosis, prognosis, and drug or antibody-based targeted therapies in the future.

Macrophage-tumor cell fusions from peripheral blood of melanoma patients

Background

While the morbidity and mortality from cancer are largely attributable to its metastatic dissemination, the integral features of the cascade are not well understood. The widely accepted hypothesis is that the primary tumor microenvironment induces the epithelial-to-mesenchymal transition in cancer cells, facilitating their escape into the bloodstream, possibly accompanied by cancer stem cells. An alternative theory for metastasis involves fusion of macrophages with tumor cells (MTFs). Here we culture and characterize apparent MTFs from blood of melanoma patients.

Methods

We isolated enriched CTC populations from peripheral blood samples from melanoma patients, and cultured them. We interrogated these cultured cells for characteristic BRAF mutations, and used confocal microscopy for immunophenotyping, motility, DNA content and chromatin texture analyses, and then conducted xenograft studies using nude mice.

Findings

Morphologically, the cultured MTFs were generally large with many pseudopod extensions and lamellipodia. Ultrastructurally, the cultured MTFs appeared to be macrophages. They were rich in mitochondria and lysosomes, as well as apparent melanosomes. The cultured MTF populations were all heterogeneous with regard to DNA content, containing aneuploid and/or high-ploidy cells, and they typically showed large sheets (and/or clumps) of cytoplasmic chromatin. This cytoplasmic DNA was found within heterogeneously-sized autophagic vacuoles, which prominently contained chromatin and micronuclei. Cultured MTFs uniformly expressed pan-macrophage markers (CD14, CD68) and macrophage markers indicative of M2 polarization (CD163, CD204, CD206). They also expressed melanocyte-specific markers (ALCAM, MLANA), epithelial biomarkers (KRT, EpCAM), as well as the pro-carcinogenic cytokine MIF along with functionally related stem cell markers (CXCR4, CD44). MTF cultures from individual patients (5 of 8) contained melanoma-specific BRAF activating mutations. Chromatin texture analysis of deconvoluted images showed condensed DNA (DAPI-intense) regions similar to focal regions described in stem cell fusions. MTFs were readily apparent in vivo in all human melanomas examined, often exhibiting even higher DNA content than the cultured MTFs. When cultured MTFs were transplanted subcutaneously in nude mice, they disseminated and produced metastatic lesions at distant sites.

Conclusions and Hypothesis

Apparent MTFs are present in peripheral blood of patients with cutaneous melanomas, and they possess the ability to form metastatic lesions when transplanted into mice. We hypothesize that these MTFs arise at the periphery of primary tumors in vivo, that they readily enter the bloodstream and invade distant tissues, secreting cytokines (such as MIF) to prepare “niches” for colonization by metastasis initiating cells.

The acquisition of novel N-glycosylation sites in conserved proteins during human evolution

Background

N-linked protein glycosylation plays an important role in various biological processes, including protein folding and trafficking, and cell adhesion and signaling. The acquisition of a novel N-glycosylation site may have significant effect on protein structure and function, and therefore, on the phenotype.

Results

We analyzed the human glycoproteome data set (2,534 N-glycosylation sites in 1,027 proteins) and identified 112 novel N-glycosylation sites in 91 proteins that arose in the human lineage since the last common ancestor of Euarchonta (primates and treeshrews). Three of them, Asn-196 in adipocyte plasma membrane-associated protein (APMAP), Asn-91 in cluster of differentiation 166 (CD166/ALCAM), and Asn-76 in thyroglobulin, are human-specific. Molecular evolutionary analysis suggested that these sites were under positive selection during human evolution. Notably, the Asn-76 of thyroglobulin might be involved in the increased production of thyroid hormones in humans, especially thyroxine (T4), because the removal of the glycan moiety from this site was reported to result in a significant decrease in T4 production.

Conclusions

We propose that the novel N-glycosylation sites described in this study may be useful candidates for functional analyses to identify innovative genetic modifications for beneficial phenotypes acquired in the human lineage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0468-5) contains supplementary material, which is available to authorized users.

Overexpression of activated leukocute cell adhesion molecule in gastric cancer is associated with advanced stages and poor prognosis and miR-9 deregulation

Activated leukocyte cell adhesion molecule (ALCAM) has been identified as a novel potential molecular marker of human tumors. The present study aimed to assess ALCAM as a prognostic marker for gastric cancer (GC), and to explore the mRNA deregulation underlying the abnormal expression of ALCAM. The mRNA and protein expression of ALCAM in GC and adjacent non‑tumor tissues from 66 patients with GC were analyzed. The association between miR‑9 and ALCAM mRNA expression was determined by quantitative polymerase chain reaction. Serum soluble ALCAM (sALCAM) was analyzed by ELISA in 72 patients with GC, 82 patients with gastric precancerous lesions and 73 controls. ALCAM and sALCAM levels were associated with certain clinicopathological variables, including overall survival. Compared with the non‑tumor tissues, the expression of ALCAM mRNA in the GC tissues was significantly upregulated (P=0.013). The expression of miR‑9 was reduced and inversely correlated with ALCAM mRNA levels in GC tissues and cell lines. The ALCAM mRNA level was reduced following ectopic overexpression of miR‑9 in SGC‑7901 human gastric cancer cells. The rates of membranous and cytoplasmic expression of ALCAM in GC tissues were 59.1 and 48.48%, respectively, and the serum sALCAM levels were significantly elevated in patients with GC. Elevated ALCAM mRNA, membranous ALCAM expression in GC tissues and high sALCAM levels are associated with advanced tumor stage, lymphatic invasion and shorter overall survival duration. The results of the current study indicated that membranous ALCAM expression and high serum sALCAM levels are independent prognostic markers of poor survival for patients with GC, and that the overexpression of ALCAM may be due to the downregulation of miR‑9.

The Wnt/JNK signaling target gene alcam is required for embryonic kidney development

Proper development of nephrons is essential for kidney function. β-Catenin-independent Wnt signaling through Fzd8, Inversin, Daam1, RhoA and Myosin is required for nephric tubule morphogenesis. Here, we provide a novel mechanism through which non-canonical Wnt signaling contributes to tubular development. Using Xenopus laevis as a model system, we found that the cell-adhesion molecule Alcam is required for proper nephrogenesis and functions downstream of Fzd3 during embryonic kidney development. We found alcam expression to be independent of Fzd8 or Inversin, but to be transcriptionally regulated by the β-Catenin-independent Wnt/JNK pathway involving ATF2 and Pax2 in a direct manner. These novel findings indicate that several branches of Wnt signaling are independently required for proximal tubule development. Moreover, our data indicate that regulation of morphogenesis by non-canonical Wnt ligands also involves direct transcriptional responses in addition to the effects on a post-translational level.

Müller glia: Stem cells for generation and regeneration of retinal neurons in teleost fish

Adult zebrafish generate new neurons in the brain and retina throughout life. Growth-related neurogenesis allows a vigorous regenerative response to damage, and fish can regenerate retinal neurons, including photoreceptors, and restore functional vision following photic, chemical, or mechanical destruction of the retina. Müller glial cells in fish function as radial-glial-like neural stem cells. During adult growth, Müller glial nuclei undergo sporadic, asymmetric, self-renewing mitotic divisions in the inner nuclear layer to generate a rod progenitor that migrates along the radial fiber of the Müller glia into the outer nuclear layer, proliferates, and differentiates exclusively into rod photoreceptors. When retinal neurons are destroyed, Müller glia in the immediate vicinity of the damage partially and transiently dedifferentiate, re-express retinal progenitor and stem cell markers, re-enter the cell cycle, undergo interkinetic nuclear migration (characteristic of neuroepithelial cells), and divide once in an asymmetric, self-renewing division to generate a retinal progenitor. This daughter cell proliferates rapidly to form a compact neurogenic cluster surrounding the Müller glia; these multipotent retinal progenitors then migrate along the radial fiber to the appropriate lamina to replace missing retinal neurons. Some aspects of the injury-response in fish Müller glia resemble gliosis as observed in mammals, and mammalian Müller glia exhibit some neurogenic properties, indicative of a latent ability to regenerate retinal neurons. Understanding the specific properties of fish Müller glia that facilitate their robust capacity to generate retinal neurons will inform and inspire new clinical approaches for treating blindness and visual loss with regenerative medicine.

A self-renewing division of zebrafish Müller glial cells generates neuronal progenitors that require N-cadherin to regenerate retinal neurons

Müller glia function as retinal stem cells in adult zebrafish. In response to loss of retinal neurons, Müller glia partially dedifferentiate, re-express neuroepithelial markers and re-enter the cell cycle. We show that the immunoglobulin superfamily adhesion molecule Alcama is a novel marker of multipotent retinal stem cells, including injury-induced Müller glia, and that each Müller glial cell divides asymmetrically only once to produce an Alcama-negative, proliferating retinal progenitor. The initial mitotic division of Müller glia involves interkinetic nuclear migration, but mitosis of retinal progenitors occurs in situ. Rapidly dividing retinal progenitors form neurogenic clusters tightly associated with Alcama/N-cadherin-labeled Müller glial radial processes. Genetic suppression of N-cadherin function interferes with basal migration of retinal progenitors and subsequent regeneration of HuC/D(+) inner retinal neurons.

Dynamics and regulation of epithelial adherens junctions: recent discoveries and controversies

Adherens junctions (AJs) are evolutionarily conserved plasma-membrane structures that mediate cell-cell adhesions in multicellular organisms. They are organized by several types of adhesive integral membrane proteins, most notably cadherins and nectins that are clustered and stabilized by a number of cytoplasmic scaffolds. AJs are key regulators of tissue architecture and dynamics via control of cell proliferation, polarity, shape, motility, and survival. They are absolutely critical for normal tissue morphogenesis and their disruption results in pathological abnormalities in different tissues. Although the field of adherens-junction research dramatically progressed in recent years, a number of important questions remain controversial and poorly understood. This review outlines basic principles that regulate organization of AJs in mammalian epithelia and discusses recent advances and standing controversies in the field. A special attention is paid to the regulation of AJs by vesicle trafficking and the intracellular cytoskeleton as well as roles and mechanisms of adherens-junction disruption during tumor progression and tissue inflammation.

miR-214 coordinates melanoma progression by upregulating ALCAM through TFAP2 and miR-148b downmodulation

Malignant melanoma is one of the most aggressive human cancers, but the mechanisms governing its metastatic dissemination are not fully understood. Upregulation of miR-214 and ALCAM and the loss of TFAP2 expression have been implicated in this process, with TFAP2 a direct target of miR-214. Here, we link miR-214 and ALCAM as well as identify a core role for miR-214 in organizing melanoma metastasis. miR-214 upregulated ALCAM, acting transcriptionally through TFAP2 and also posttranscriptionally through miR-148b (itself controlled by TFAP2), both negative regulators of ALCAM. We also identified several miR-214-mediated prometastatic functions directly promoted by ALCAM. Silencing ALCAM in miR-214-overexpressing melanoma cells reduced cell migration and invasion without affecting growth or anoikis in vitro, and it also impaired extravasation and metastasis formation in vivo. Conversely, cell migration and extravasation was reduced in miR-214-overexpressing cells by upregulation of either miR-148b or TFAP2. These findings were consistent with patterns of expression of miR-214, ALCAM, and miR-148b in human melanoma specimens. Overall, our results define a pathway involving miR-214, miR-148b, TFAP2, and ALCAM that is critical for establishing distant metastases in melanoma.