AmotL2 disrupts apical-basal cell polarity and promotes tumour invasion

The cellular localization and oncogenic or tumor suppressive effects of angiomiotin-like protein 2 in tumor and normal cells

Angiomiotin (AMOT) family comprises three members: AMOT, AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). AMOTL2 is widely expressed in endothelial cells, epithelial cells, and various cancer cells. Specifically, AMOTL2 predominantly localizes in the cytoplasm and nucleus in human normal cells, whereas associates with cell-cell junctions and actin cytoskeleton in non-human cells, and locates at cell junctions or within the recycling endosomes in cancer cells. AMOTL2 is implicated in regulation of tube formation, cell polarity, and shape, although the specific impact on tumorigenesis remains to be conclusively determined. It has been shown that AMOTL2 enhances tumor growth and metastasis in pancreatic, breast, and colon cancer, however inhibits cell proliferation and migration in lung, hepatocellular cancer, and glioblastoma. In addition to its role in cell shape and cytoskeletal dynamics through co-localization with F-actin, AMOTL2 modulates the transcription of Yes-associated protein (YAP) by binding to it, thereby affecting its phosphorylation and cellular sequestration. Furthermore, the stability and cellular localization of AMOTL2, influenced by its phosphorylation and ubiquitination mediated by specific proteins, affects its cellular function. Additionally, we observe that AMOTL2 is predominantly downregulated in some tumors, but significantly elevated in colorectal adenocarcinoma (COAD). Moreover, overall analysis, GSEA and ROC curve analysis indicate that AMOTL2 exerts as an oncogenic protein in COAD by modulating Wnt pathway, participating in synthesis of collagen formation, and interacting with extracellular matrix receptor. In addition, AMOTL2 potentially regulates the distribution of immune cells infiltration in COAD. In summary, AMOTL2 probably functions as an oncogene in COAD. Consequently, further in-depth mechanistic research is required to elucidate the precise roles of AMOTL2 in various cancers.

MicroRNA-135b mainly functions as an oncogene during tumor progression

Late diagnosis is considered one of the main reasons of high mortality rate among cancer patients that results in therapeutic failure and tumor relapse. Therefore, it is needed to evaluate the molecular mechanisms associated with tumor progression to introduce efficient markers for the early tumor detection among cancer patients. The remarkable stability of microRNAs (miRNAs) in body fluids makes them potential candidates to use as the non-invasive tumor biomarkers in cancer screening programs. MiR-135b has key roles in prognosis and survival of cancer patients by either stimulating or inhibiting cell proliferation, invasion, and angiogenesis. Therefore, in the present review we assessed the molecular biology of miR-135b during tumor progression to introduce that as a novel tumor marker in cancer patients. It has been reported that miR-135b mainly acts as an oncogene by regulation of transcription factors, signaling pathways, drug response, cellular metabolism, and autophagy. This review paves the way to suggest miR-135b as a tumor marker and therapeutic target in cancer patients following the further clinical trials and animal studies.

Angiomotin family proteins in the Hippo signaling pathway

The Motin family proteins (Motins) are a class of scaffolding proteins consisting of Angiomotin (AMOT), AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). Motins play a pivotal role in angiogenesis, tumorigenesis, and neurogenesis by modulating multiple cellular signaling pathways. Recent findings indicate that Motins are components of the Hippo pathway, a signaling cascade involved in development and cancer. This review discusses how Motins are integrated into the Hippo signaling network, as either upstream regulators or downstream effectors, to modulate cell proliferation and migration. The repression of YAP/TAZ by Motins contributes to growth inhibition, whereas subcellular localization of Motins and their interactions with actin fibers are critical in regulating cell migration. The net effect of Motins on cell proliferation and migration may contribute to their diverse biological functions.

The circadian gene ARNTL2 promotes nasopharyngeal carcinoma invasiveness and metastasis through suppressing AMOTL2-LATS-YAP pathway

Metastasis is the major culprit of treatment failure in nasopharyngeal carcinoma (NPC). Aryl hydrocarbon receptor nuclear translocator like 2 (ARNTL2), a core circadian gene, plays a crucial role in the development of various tumors. Nevertheless, the biological role and mechanism of ARNTL2 are not fully elucidated in NPC. In this study, ARNTL2 expression was significantly upregulated in NPC tissues and cells. Overexpression of ARNTL2 facilitated NPC cell migration and invasion abilities, while inhibition of ARNTL2 in similarly treated cells blunted migration and invasion abilities in vitro. Consistently, in vivo xenograft tumor models revealed that ARNTL2 silencing reduced nude mice inguinal lymph node and lung metastases, as well as tumor growth. Mechanistically, ARNTL2 negatively regulated the transcription expression of AMOTL2 by directly binding to the AMOTL2 promoter, thus reducing the recruitment and stabilization of AMOTL2 to LATS1/2 kinases, which strengthened YAP nuclear translocation by suppressing LATS-dependent YAP phosphorylation. Inhibition of AMOTL2 counteracted the effects of ARNTL2 knockdown on NPC cell migration and invasion abilities. These findings suggest that ARNTL2 may be a promising therapeutic target to combat NPC metastasis and further supports the crucial roles of circadian genes in cancer development.

Role of angiomotin family members in human diseases (Review)

Angiomotin (Amot) family members, including Amot, Amot-like protein 1 (Amotl1) and Amot-like protein 2 (Amotl2), have been found to interact with angiostatins. In addition, Amot family members are involved in various physiological and pathological functions such as embryonic development, angiogenesis and tumorigenesis. Some studies have also demonstrated its regulation in signaling pathways such as the Hippo signaling pathway, AMPK signaling pathway and mTOR signaling pathways. Amot family members play an important role in neural stem cell differentiation, dendritic formation and synaptic maturation. In addition, an increasing number of studies have focused on their function in promoting and/or suppressing cancer, but the underlying mechanisms remain to be elucidated. The present review integrated relevant studies on upstream regulation and downstream signals of Amot family members, as well as the latest progress in physiological and pathological functions and clinical applications, hoping to offer important ideas for further research.

A phenotypic screening approach to target p60AmotL2-expressing invasive cancer cells

BACKGROUND

Tumor cells have the ability to invade and form small clusters that protrude into adjacent tissues, a phenomenon that is frequently observed at the periphery of a tumor as it expands into healthy tissues. The presence of these clusters is linked to poor prognosis and has proven challenging to treat using conventional therapies. We previously reported that p60AmotL2 expression is localized to invasive colon and breast cancer cells. In vitro, p60AmotL2 promotes epithelial cell invasion by negatively impacting E-cadherin/AmotL2-related mechanotransduction.

METHODS

Using epithelial cells transfected with inducible p60AmotL2, we employed a phenotypic drug screening approach to find compounds that specifically target invasive cells. The phenotypic screen was performed by treating cells for 72 h with a library of compounds with known antitumor activities in a dose-dependent manner. After assessing cell viability using CellTiter-Glo, drug sensitivity scores for each compound were calculated. Candidate hit compounds with a higher drug sensitivity score for p60AmotL2-expressing cells were then validated on lung and colon cell models, both in 2D and in 3D, and on colon cancer patient-derived organoids. Nascent RNA sequencing was performed after BET inhibition to analyse BET-dependent pathways in p60AmotL2-expressing cells.

RESULTS

We identified 60 compounds that selectively targeted p60AmotL2-expressing cells. Intriguingly, these compounds were classified into two major categories: Epidermal Growth Factor Receptor (EGFR) inhibitors and Bromodomain and Extra-Terminal motif (BET) inhibitors. The latter consistently demonstrated antitumor activity in human cancer cell models, as well as in organoids derived from colon cancer patients. BET inhibition led to a shift towards the upregulation of pro-apoptotic pathways specifically in p60AmotL2-expressing cells.

CONCLUSIONS

BET inhibitors specifically target p60AmotL2-expressing invasive cancer cells, likely by exploiting differences in chromatin accessibility, leading to cell death. Additionally, our findings support the use of this phenotypic strategy to discover novel compounds that can exploit vulnerabilities and specifically target invasive cancer cells.

Deciphering the Role of p60AmotL2 in Epithelial Extrusion and Cell Detachment

Preserving an accurate cell count is crucial for maintaining homeostasis. Apical extrusion, a process in which redundant cells are eliminated by neighboring cells, plays a key role in this regard. Recent studies have revealed that apical extrusion can also be triggered in cells transformed by oncogenes, suggesting it may be a mechanism through which tumor cells escape their microenvironment. In previous work, we demonstrated that p60AmotL2 modulates the E-cadherin function by inhibiting its connection to radial actin filaments. This isoform of AmotL2 is expressed in invasive breast and colon tumors and promotes invasion in vitro and in vivo. Transcriptionally regulated by c-Fos, p60AmotL2 is induced by local stress signals such as severe hypoxia. In this study, we investigated the normal role of p60AmotL2 in epithelial tissues. We found that this isoform is predominantly expressed in the gut, where cells experience rapid turnover. Through time-lapse imaging, we present evidence that cells expressing p60AmotL2 are extruded by their normal neighboring cells. Based on these findings, we hypothesize that tumor cells exploit this pathway to detach from normal epithelia and invade surrounding tissues.

Modulation of E-Cadherin Function through the AmotL2 Isoforms Promotes Ameboid Cell Invasion

The spread of tumor cells and the formation of distant metastasis remain the main causes of mortality in cancer patients. However, the mechanisms governing the release of cells from micro-environmental constraints remain unclear. E-cadherin negatively controls the invasion of epithelial cells by maintaining cell-cell contacts. Furthermore, the inactivation of E-cadherin triggers invasion in vitro. However, the role of E-cadherin is complex, as metastasizing cells maintain E-cadherin expression, which appears to have a positive role in the survival of tumor cells. In this report, we present a novel mechanism delineating how E-cadherin function is modulated to promote invasion. We have previously shown that E-cadherin is associated with p100AmotL2, which is required for radial actin formation and the transmission of mechanical force. Here, we present evidence that p60AmotL2, which is expressed in invading tumor cells, binds to the p100AmotL2 isoform and uncouples the mechanical constraint of radial actin filaments. We show for the first time that the coupling of E-cadherin to the actin cytoskeleton via p100AmotL2 is directly connected to the nuclear membrane. The expression of p60AmotL2 inactivates this connection and alters the properties of the nuclear lamina, potentiating the invasion of cells into micropores of the extracellular matrix. In summary, we propose that the balance of the two AmotL2 isoforms is important in the modulation of E-cadherin function and that an imbalance of this axis promotes ameboid cell invasion.

The role of Motin family proteins in tumorigenesis-an update

The Motin protein family consists of three members: AMOT (p80 and p130 isoforms), AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). The family members play an important role in processes such as cell proliferation, migration, angiogenesis, tight junction formation, and cell polarity. These functions are mediated through the involvement of the Motins in the regulation of different signal transduction pathways, including those regulated by small G-proteins and the Hippo-YAP pathway. One of the more characterized aspects of Motin family function is their role in regulating signaling through the Hippo-YAP pathway, and while some studies suggest a YAP-inhibitory function other studies indicate the Motins are required for YAP activity. This duality is also reflected in previous reports, often contradictory, that suggest the Motin proteins can function as oncogenes or tumor suppressors in tumorigenesis. In this review we summarize recent findings and integrate that with the existing work describing the multifunctional role of the Motins in different cancers. The emerging picture suggests that the Motin protein function is cell-type and context dependent and that further investigation in relevant cell types and whole organism models is required for the elucidation of the function of this protein family.

Heterogeneity of Islet Cells during Embryogenesis and Differentiation

Diabetes is caused by insufficient insulin secretion due to β-cell dysfunction and/or β-cell loss. Therefore, the restoration of functional β-cells by the induction of β-cell differentiation from embryonic stem (ES) and induced-pluripotent stem (iPS) cells, or from somatic non-β-cells, may be a promising curative therapy. To establish an efficient and feasible method for generating functional insulin-producing cells, comprehensive knowledge of pancreas development and β-cell differentiation, including the mechanisms driving cell fate decisions and endocrine cell maturation is crucial. Recent advances in single-cell RNA sequencing (scRNA-seq) technologies have opened a new era in pancreas development and diabetes research, leading to clarification of the detailed transcriptomes of individual insulin-producing cells. Such extensive high-resolution data enables the inference of developmental trajectories during cell transitions and gene regulatory networks. Additionally, advancements in stem cell research have not only enabled their immediate clinical application, but also has made it possible to observe the genetic dynamics of human cell development and maturation in a dish. In this review, we provide an overview of the heterogeneity of islet cells during embryogenesis and differentiation as demonstrated by scRNA-seq studies on the developing and adult pancreata, with implications for the future application of regenerative medicine for diabetes.

RNA-seq and ATAC-seq analysis of CD163+ macrophage-induced progestin-insensitive endometrial cancer cells

BACKGROUND

Progestins are used as fertility-sparing regimens for young patients with stage 1A endometrioid endometrial cancer (EEC) and atypical endometrial hyperplasia (AEH). CD163⁺ macrophages promote estrogen-dependent EEC development, but whether they induce progestin insensitivity remains unclear. This study aimed to investigate the possible effects of CD163⁺ macrophages on progestin response in AEH/EEC patients.

METHODS

The number of infiltrating CD163⁺ macrophages in progestin-insensitive and -sensitive endometrial lesions was compared. The effects of CD163⁺ macrophages on progestin responses and progesterone receptor (PR) expression in EC cells were evaluated in vitro. ATAC-seq and RNA-seq were combined to identify molecular/biological changes induced by CD163⁺ macrophages in progestin-insensitive EC cells.

RESULTS

Increased CD163⁺ macrophage infiltration was significantly associated with progestin insensitivity and longer treatment durations in AEH/EEC patients. Additionally, the number of CD163⁺ macrophages was negatively correlated with PR expression in AEH/EEC tissues. Furthermore, the CD163⁺ macrophage-mediated microenvironment and secreted cytokines downregulated PR expression and impaired the response of EC cells to medroxyprogesterone acetate (MPA). RNA-seq analysis demonstrated that CD163⁺ macrophages antagonized PR signaling by blocking or even reversing MPA-regulated differential gene expression. Based on RNA-seq and ATAC-seq analyses, extracellular matrix (ECM) signaling and ECM-related transcription factors, FOXF2, POU1F1, and RUNX1were identified to potentially be involved in CD163⁺ macrophage-induced progestin insensitivity in endometrial cancer patients.

CONCLUSIONS

We identified CD163⁺ macrophages as an important mediator of progestin desensitization and an unfavorable factor for the efficacy of fertility-preserving treatment in AEH/EEC patients.

Suppression of YAP safeguards human naïve pluripotency

Propagation of human naïve pluripotent stem cells (nPSCs) relies on the inhibition of MEK/ERK signalling. However, MEK/ERK inhibition also promotes differentiation into trophectoderm (TE). Therefore, robust self-renewal requires suppression of TE fate. Tankyrase inhibition using XAV939 has been shown to stabilise human nPSCs and is implicated in TE suppression. Here, we dissect the mechanism of this effect. Tankyrase inhibition is known to block canonical Wnt/β-catenin signalling. However, we show that nPSCs depleted of β-catenin remain dependent on XAV939. Rather than inhibiting Wnt, we found that XAV939 prevents TE induction by reducing activation of YAP, a co-factor of TE-inducing TEAD transcription factors. Tankyrase inhibition stabilises angiomotin, which limits nuclear accumulation of YAP. Upon deletion of angiomotin-family members AMOT and AMOTL2, nuclear YAP increases and XAV939 fails to prevent TE induction. Expression of constitutively active YAP similarly precipitates TE differentiation. Conversely, nPSCs lacking YAP1 or its paralog TAZ (WWTR1) resist TE differentiation and self-renewal efficiently without XAV939. These findings explain the distinct requirement for tankyrase inhibition in human but not in mouse nPSCs and highlight the pivotal role of YAP activity in human naïve pluripotency and TE differentiation. This article has an associated 'The people behind the papers' interview.

NrCAM secreted by endometrial stromal cells enhances the progestin sensitivity of endometrial cancer cells through epigenetic modulation of PRB

Progestin is one of the main hormone treatment regimens for early-stage estrogen receptor- and progesterone receptor (PR)-positive endometrial cancer (EC). However, the response rate of EC to progestins is unsatisfactory. Investigating the mechanisms related to progestin treatment could help improve treatment efficacy. Studies have demonstrated that normal endometrial stromal cells (ESCs) increase the inhibitory effect of progestin on EC cell proliferation via paracrine signaling, but the mechanisms involved remain unclear. In this study, we found that ESCs had different morphological features between progestin-sensitive and -insensitive EC tissues. ESCs presented typical decidualization changes in progestin-sensitive cases, while they remained slim in progestin-insensitive EC lesions, indicating no response. Furthermore, ESCs enhanced the inhibitory effect of medroxyprogesterone acetate (MPA) on EC cell proliferation by secreting neuron cell adhesion molecule (NrCAM). MPA treatment enhanced NrCAM secretion by ESCs. EC xenografts in BALB/C nude mice demonstrated that MPA combined with NrCAM had an increased tumor inhibitory effect compared with MPA or NrCAM alone. Mechanistically, MPA upregulated NrCAM expression in ESCs through PR. Specifically, NrCAM increased PR expression in EC cells through TET1-induced hydroxymethylation of the PRB gene promoter region. These findings indicate that NrCAM or NrCAM combined with progestins could be a new EC treatment.

AmotL2, IQGAP1, and FKBP51 Scaffold Proteins in Glioblastoma Stem Cell Niches

Glioma stem cells (GSCs) live in a continuous process of stemness reprogramming to achieve specific cell commitment within the so-called GSC niches, specifically located in periarteriolar regions. In this review, we analyze the expression levels, cellular and subcellular location, and role of three scaffold proteins (IQGAP1, FKBP51, and AmotL2) in GSC niches. Scaffold proteins contribute to cell differentiation, migration, and angiogenesis in glioblastoma. It could be of diagnostic interest for establishing stages, for therapeutic targets, and for improving glioblastoma prognosis, which is still at the experimental level.

Cadherin‐3 is a novel oncogenic biomarker with prognostic value in glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The prognosis of patients is very poor, with a median overall survival of ~ 15 months after diagnosis. Cadherin‐3 (also known as P‐cadherin), a cell–cell adhesion molecule encoded by the CDH3 gene, is deregulated in several cancer types, but its relevance in GBM is unknown. In this study, we investigated the functional roles, the associated molecular signatures, and the prognostic value of CDH3/P‐cadherin in this highly malignant brain tumor. CDH3/P‐cadherin mRNA and protein levels were evaluated in human glioma samples. Knockdown and overexpression models of P‐cadherin in GBM were used to evaluate its functional role in vitro and in vivo. CDH3‐associated gene signatures were identified by enrichment analyses and correlations. The impact of CDH3 in the survival of GBM patients was assessed in independent cohorts using both univariable and multivariable models. We found that P‐cadherin protein is expressed in a subset of gliomas, with an increased percentage of positive samples in grade IV tumors. Concordantly, CDH3 mRNA levels in glioma samples from The Cancer Genome Atlas (TCGA) database are increased in high‐grade gliomas. P‐cadherin displays oncogenic functions in multiple knockdown and overexpression GBM cell models by affecting cell viability, cell cycle, cell invasion, migration, and neurosphere formation capacity. Genes that were positively correlated with CDH3 are enriched for oncogenic pathways commonly activated in GBM. In vivo, GBM cells expressing high levels of P‐cadherin generate larger subcutaneous tumors and cause shorter survival of mice in an orthotopic intracranial model. Concomitantly, high CDH3 expression is predictive of shorter overall survival of GBM patients in independent cohorts. Together, our results show that CDH3/P‐cadherin expression is associated with aggressiveness features of GBM and poor patient prognosis, suggesting that it may be a novel therapeutic target for this deadly brain tumor.

AMOTL2 restrains transforming growth factor-β1-induced proliferation and extracellular matrix deposition of airway smooth muscle cells via the down-regulation of YAP1 activation

Angiomotin-like 2 (AMOTL2) is a key modulator of signaling transduction and participates in the regulation of various cellular progresses under diverse physiological and pathological conditions. However, whether AMOTL2 participates in asthma pathogenesis has not been fully studied. In the present work, we studied the possible role and mechanism of AMOTL2 in regulating transforming growth factor-β1 (TGF-β1)-induced proliferation and extracellular matrix (ECM) deposition of airway smooth muscle (ASM) cells. Our results showed marked reductions in the abundance of AMOTL2 in TGF-β1-stimulated ASM cells. Cellular functional investigations confirmed that the up-regulation of AMOTL2 dramatically decreased the proliferation and ECM deposition induced by TGF-β1 in ASM cells. In contrast, the depletion of AMOTL2 exacerbated TGF-β1-induced ASM cell proliferation and ECM deposition. Further research revealed that the overexpression of AMOTL2 restrained the activation of Yes-associated protein 1 (YAP1) in TGF-β1-stimulated ASM cells. Moreover, the reactivation of YAP1 markedly reversed AMOTL2-mediated suppression of TGF-β1-induced ASM cell proliferation and ECM deposition. Together, these findings suggest that AMOTL2 restrains TGF-β1-induced proliferation and ECM deposition of ASM cells by down-regulating YAP1 activation.

AMOTL2 mono-ubiquitination by WWP1 promotes contact inhibition by facilitating LATS activation

This work reveals a novel function of WWP1 E3 ligase in the mono-ubiquitination of AMOTL2, which enables the binding and activation of LATS kinases upon contact inhibition.

Contact inhibition is a key cellular phenomenon that prevents cells from hyper-proliferating upon reaching confluence. Although not fully characterized, a critical driver of this process is the Hippo signaling pathway, whose downstream effector yes-associated protein plays pivotal roles in cell growth and differentiation. Here, we provide evidence that the E3 ligase WWP1 (WW-domain containing protein 1) mono-ubiquitinates AMOTL2 (angiomotin-like 2) at K347 and K408. Mono-ubiquitinated AMOTL2, in turn, interacts with the kinase LATS2, which facilitates recruitment of the upstream Hippo pathway component SAV1 and ultimately promotes yes-associated protein phosphorylation and subsequent cytoplasmic sequestration and/or degradation. Furthermore, contact inhibition induced by high cell density promoted the localization and stabilization of WWP1 at cell junctions, where it interacted with Crumbs polarity proteins. Notably, the Crumbs complex was functionally important for AMOTL2 mono-ubiquitination and LATS activation under high cell density conditions. These findings delineate a functionally important molecular mechanism in which AMOTL2 mono-ubiquitination by WWP1 at cell junctions and LATS activation are tightly coupled to upstream cell density cues.

Key Role for CRB2 in the Maintenance of Apicobasal Polarity in Retinal Pigment Epithelial Cells

Apicobasal polarity is essential for epithelial cell function, yet the roles of different proteins in its completion is not fully understood. Here, we have studied the role of the polarity protein, CRB2, in human retinal pigment epithelial (RPE) cells during polarization in vitro, and in mature murine RPE cells in vivo. After establishing a simplified protocol for the culture of human fetal RPE cells, we studied the temporal sequence of the expression and localization of polarity and cell junction proteins during polarization in these epithelial cells. We found that CRB2 plays a key role in tight junction maintenance as well as in cell cycle arrest. In addition, our studies in vivo show that the knockdown of CRB2 in the RPE affects to the distribution of different apical polarity proteins and results in perturbed retinal homeostasis, manifested by the invasion of activated microglial cells into the subretinal space. Together our results demonstrate that CRB2 is a key protein for the development and maintenance of a polarized epithelium.

Endocrine Pancreas Development and Dysfunction Through the Lens of Single-Cell RNA-Sequencing

A chronic inability to maintain blood glucose homeostasis leads to diabetes, which can damage multiple organs. The pancreatic islets regulate blood glucose levels through the coordinated action of islet cell-secreted hormones, with the insulin released by β-cells playing a crucial role in this process. Diabetes is caused by insufficient insulin secretion due to β-cell loss, or a pancreatic dysfunction. The restoration of a functional β-cell mass might, therefore, offer a cure. To this end, major efforts are underway to generate human β-cells de novo, in vitro, or in vivo. The efficient generation of functional β-cells requires a comprehensive knowledge of pancreas development, including the mechanisms driving cell fate decisions or endocrine cell maturation. Rapid progress in single-cell RNA sequencing (scRNA-Seq) technologies has brought a new dimension to pancreas development research. These methods can capture the transcriptomes of thousands of individual cells, including rare cell types, subtypes, and transient states. With such massive datasets, it is possible to infer the developmental trajectories of cell transitions and gene regulatory pathways. Here, we summarize recent advances in our understanding of endocrine pancreas development and function from scRNA-Seq studies on developing and adult pancreas and human endocrine differentiation models. We also discuss recent scRNA-Seq findings for the pathological pancreas in diabetes, and their implications for better treatment.

MAGI1 inhibits the AMOTL2/p38 stress pathway and prevents luminal breast tumorigenesis

Alterations to cell polarization or to intercellular junctions are often associated with epithelial cancer progression, including breast cancers (BCa). We show here that the loss of the junctional scaffold protein MAGI1 is associated with bad prognosis in luminal BCa, and promotes tumorigenesis. E-cadherin and the actin binding scaffold AMOTL2 accumulate in MAGI1 deficient cells which are subjected to increased stiffness. These alterations are associated with low YAP activity, the terminal Hippo-pathway effector, but with an elevated ROCK and p38 Stress Activated Protein Kinase activities. Blocking ROCK prevented p38 activation, suggesting that MAGI1 limits p38 activity in part through releasing actin strength. Importantly, the increased tumorigenicity of MAGI1 deficient cells is rescued in the absence of AMOTL2 or after inhibition of p38, demonstrating that MAGI1 acts as a tumor-suppressor in luminal BCa by inhibiting an AMOTL2/p38 stress pathway.

Identification of PDZ Interactions by Affinity Purification and Mass Spectrometry Analysis

Identification of protein networks becomes indispensable for determining the function of a given protein of interest. Some proteins harbor a PDZ binding motif (PDZBM) located at the carboxy-terminus end. This motif is necessary to recruit PDZ domain proteins which are involved in signaling, trafficking, and maintenance of cell architecture. In the present chapter, we present two complementary approaches (immunopurification and peptide-based purification procedures) followed by mass spectrometry analysis to identify PDZ domain proteins associated to a given protein of interest. As proof of example, we focus our attention on TANC1 which is a scaffold protein harboring a PDZBM at its carboxy-terminus. Using these two approaches, we identified several PDZ domain containing proteins. Some of them were found with both approaches, and some were specifically identified using peptide-based purification procedure. This exemplifies advantages and differences of both strategies to identify PDZ interactions.

Extracellular vesicle-associated miR-135b and -135a regulate stemness in Group 4 medulloblastoma cells by targeting angiomotin-like 2

Background

Extracellular vesicles (EVs) secreted by tumours, including exosomes, are important factors that regulate cell–cell interactions in oncogenesis. Although EV studies are ongoing, the biological understanding of EV-miRNAs derived from brain tumour spheroid-forming cells (BTSCs) of medulloblastoma is poor.

Purposes

We explored the specific cellular miRNAs and EV-miRNAs in medulloblastoma BTSCs to determine their potential biological function.

Methods

Bulk tumor cells (BTCs) and BTSCs were cultured under different conditions from medulloblastoma tissues (N = 10).

Results

Twenty-four miRNAs were simultaneously increased in both cells and EVs derived from BTSCs in comparison to BTCs. After inhibition of miR-135b or miR135a which were the most significantly increased in BTSCs, cell viability, self-renewal and stem cell marker expression decreased remarkably. Through integrated analysis of mRNAs and miRNAs data, we found that angiomotin-like 2 (AMOTL2), which was significantly decreased, was targeted by both miR-135b and miR-135a. STAT6 and GPX8 were targeted only by miR-135a. Importantly, low expression of AMOTL2 was significantly associated with overall poor survival in paediatric Group 3 and Group 4 medulloblastoma patients.

Conclusion

Our results indicated that inhibition of miR-135b or miR-135a leads to suppress stemness of BTSC through modulation of AMOTL2.

Emerging roles for angiomotin in the nervous system

Angiomotins are a family of molecular scaffolding proteins that function to organize contact points (called tight junctions in vertebrates) between adjacent cells. Some angiomotin isoforms bind to the actin cytoskeleton and are part of signaling pathways that influence cell morphology and migration. Others cooperate with components of the Hippo signaling pathway and the associated networks to control organ growth. The 130-kDa isoform, AMOT-p130, has critical roles in neural stem cell differentiation, dendritic patterning, and synaptic maturation-attributes that are essential for normal brain development and are consistent with its association with autism. Here, we review and discuss the evidence that supports a role for AMOT-p130 in neuronal development in the central nervous system.

De novo variant in AMOTL1 in infant with cleft lip and palate, imperforate anus and dysmorphic features

AMOTL1 belongs to the Motin family of proteins that are involved in organogenesis and tumorigenesis through regulation of cellular migration, tube formation, and angiogenesis. While involvement of all AMOTs in development or suppression of cancers is relatively well described, little is known about the congenital phenotype of pathogenic variants in these genes in humans. Recently, a heterozygous variant in AMOTL1 was published in association with orofacial clefts and cardiac abnormalities in an affected father and his daughter. However, studies in mice did not recapitulate the human phenotype and the case was summarized as inconclusive. We present a female infant with cleft lip and palate, imperforate anus and dysmorphic features, in whom trio exome sequencing revealed a de novo variant in AMOTL1 affecting a highly conserved amino acid (c.479C>T; p.[Pro160Leu]). Bioinformatic predictions and in silico modeling supported pathogenicity. This case reinforces the conjecture regarding the disruptive effect of pathogenic variants in AMOTL1 on organ formation in humans. Studies of additional families will reveal the full phenotypic spectrum associated with this multiple malformation syndrome.

Revisiting Cell Death Responses in Fibrotic Lung Disease: Crosstalk between Structured and Non-Structured Cells

Fibrosis is a life-threatening disorder caused by excessive formation of connective tissue that can affect several critical organs. Innate immune cells are involved in the development of various disorders, including lung fibrosis. To date, several hematopoietic cell types have been implicated in fibrosis, including pro-fibrotic monocytes like fibrocytes and segregated-nucleus-containing atypical monocytes (SatMs), but the precise cellular and molecular mechanisms underlying its development remain unclear. Repetitive injury and subsequent cell death response are triggering events for lung fibrosis development. Crosstalk between lung structured and non-structured cells is known to regulate the key molecular event. We recently reported that RNA-binding motif protein 7 (RBM7) expression is highly upregulated in the fibrotic lung and plays fundamental roles in fibrosis development. RBM7 regulates nuclear degradation of NEAT1 non-coding RNA, resulting in sustained apoptosis in the lung epithelium and fibrosis. Apoptotic epithelial cells produce CXCL12, which leads to the recruitment of pro-fibrotic monocytes. Apoptosis is also the main source of autoantigens. Recent studies have revealed important functions for natural autoantibodies that react with specific sets of self-antigens and are unique to individual diseases. Here, we review recent insights into lung fibrosis development in association with crosstalk between structured cells like lung epithelial cells and non-structured cells like migrating immune cells, and discuss their relevance to acquired immunity through natural autoantibody production.

The C7orf43/TRAPPC14 component links the TRAPPII complex to Rabin8 for preciliary vesicle tethering at the mother centriole during ciliogenesis

The primary cilium is a cellular sensor that detects light, chemicals, and movement and is important for morphogen and growth factor signaling. The small GTPase Rab11-Rab8 cascade is required for ciliogenesis. Rab11 traffics the guanine nucleotide exchange factor (GEF) Rabin8 to the centrosome to activate Rab8, needed for ciliary growth. Rabin8 also requires the transport particle protein complex (TRAPPC) proteins for centrosome recruitment during ciliogenesis. Here, using an MS-based approach for identifying Rabin8-interacting proteins, we identified C7orf43 (also known as microtubule-associated protein 11 (MAP11)) as being required for ciliation both in human cells and zebrafish embryos. We find that C7orf43 directly binds to Rabin8 and that C7orf43 knockdown diminishes Rabin8 preciliary centrosome accumulation. Interestingly, we found that C7orf43 co-sediments with TRAPPII complex subunits and directly interacts with TRAPPC proteins. Our findings establish that C7orf43 is a TRAPPII-specific complex component, referred to here as TRAPPC14. Additionally, we show that TRAPPC14 is dispensable for TRAPPII complex integrity but mediates Rabin8 association with the TRAPPII complex. Finally, we demonstrate that TRAPPC14 interacts with the distal appendage proteins Fas-binding factor 1 (FBF1) and centrosomal protein 83 (CEP83), which we show here are required for GFP-Rabin8 centrosomal accumulation, supporting a role for the TRAPPII complex in tethering preciliary vesicles to the mother centriole during ciliogenesis. In summary, our findings have revealed an uncharacterized TRAPPII-specific component, C7orf43/TRAPPC14, that regulates preciliary trafficking of Rabin8 and ciliogenesis and support previous findings that the TRAPPII complex functions as a membrane tether.

Role of Tricellular Tight Junction Protein Lipolysis-Stimulated Lipoprotein Receptor (LSR) in Cancer Cells

Maintaining a robust epithelial barrier requires the accumulation of tight junction proteins, LSR/angulin-1 and tricellulin, at the tricellular contacts. Alterations in the localization of these proteins temporarily cause epithelial barrier dysfunction, which is closely associated with not only physiological differentiation but also cancer progression and metastasis. In normal human endometrial tissues, the endometrial cells undergo repeated proliferation and differentiation under physiological conditions. Recent observations have revealed that the localization and expression of LSR/angulin-1 and tricellulin are altered in a menstrual cycle-dependent manner. Moreover, it has been shown that endometrial cancer progression affects these alterations. This review highlights the differences in the localization and expression of tight junction proteins in normal endometrial cells and endometrial cancers and how they cause functional changes in cells.

Loss of cell polarity regulated by PTEN/Cdc42 enrolled in the process of Hepatopulmonary Syndrome

One central factor in hepatopulmonary syndrome (HPS) pathogenesis is pulmonary vascular remodelling (PVR) which involves dysregulation of proliferation and migration in pulmonary microvascular endothelial cells (PMVECs). Growing evidence suggests that Apical/basolateral polarity plays an important role in cell proliferation, migration, adhesion and differentiation. In this study, we explored whether cell polarity is involved and critical in experimental HPS rats that are induced by common bile duct ligation (CBDL). Cell polarity related proteins were analysed in CBDL rats lung and PMVECs under the HPS serum stimulation by immunofluorescence assay. Cdc42/PTEN activity, cell proliferation and migration and Annexin A2 (AX2) in PMVECs were determined, respectively. Cell polarity related proteins, lost their specialized luminal localization in PMVECs of the CBDL rat. The loss of cell polarity was induced by abnormal activity of Cdc42, which was strongly enhanced by the interaction between p‐PTEN and Annexin A2 in PMVECs, after treatment with serum from CBDL rats. It led to over‐proliferation and high migration ability of PMVECs. Down‐regulation of PTEN‐Cdc42 activity in PMVECs restored cell polarity and thus reduced their ability of migration and proliferation. Our study suggested that the loss of cell polarity plays a critical role in the pathogenesis of HPS‐associated PVR and may become a potentially effective therapeutic target.

Faulty oxygen sensing disrupts angiomotin function in trophoblast cell migration and predisposes to preeclampsia

Human placenta development and a successful pregnancy is incumbent upon precise oxygen-dependent control of trophoblast migration/invasion. Persistent low oxygen leading to failed trophoblast invasion promotes inadequate spiral artery remodeling, a characteristic of preeclampsia. Angiomotin (AMOT) is a multifaceted scaffolding protein involved in cell polarity and migration, yet its upstream regulation and significance in the human placenta remain unknown. Herein, we show that AMOT is primarily expressed in migratory extravillous trophoblast cells (EVTs) of the intermediate and distal anchoring column. Its expression increases after 10 weeks of gestation when oxygen tension rises and EVT migration/invasion peaks. Time-lapse imaging confirmed that the AMOT 80-kDa isoform promotes migration of trophoblastic JEG3 and HTR-8/SVneo cells. In preeclampsia, however, AMOT expression is decreased and its localization to migratory fetomaternal interface EVTs is disrupted. We demonstrate that Jumonji C domain-containing protein 6 (JMJD6), an oxygen sensor, positively regulates AMOT via oxygen-dependent lysyl hydroxylation. Furthermore, in vitro and ex vivo studies show that transforming growth factor-β (TGF-β) regulates AMOT expression, its interaction with polarity protein PAR6, and its subcellular redistribution from tight junctions to cytoskeleton. Our data reveal an oxygen- and TGF-β-driven migratory function for AMOT in the human placenta, and implicate its deficiency in impaired trophoblast migration that plagues preeclampsia.

IQGAP1, AmotL2, and FKBP51 Scaffoldins in the Glioblastoma Microenvironment

Glioblastoma (GB) is the most frequently occurring and aggressive primary brain tumor. Glioma stem cells (GSCs) and astrocytoma cells are the predominant malignant cells occurring in GB besides a highly heterogeneous population of migrating, neovascularizing and infiltrating myeloid cells that forms a complex tumor microenvironment (TME). Cross talk between the TME cells is pivotal in the biology of this tumor and, consequently, adaptor proteins at critical junctions of signaling pathways may be crucial. Scaffold proteins (scaffolins or scaffoldins) integrate external and internal stimuli to regulate various signaling pathways, interacting simultaneously with multiple proteins involved. We investigated by double and triple immunofluorescence the localization of IQGAP1, AmotL2, and FKBP51, three closely related scaffoldins, in malignant cells and TME of human GB tumors. We found that IQGAP1 is preferentially expressed in astrocytoma cells, AmotL2 in GSCs, and FKBP51 in white blood cells in human GB tumors. As GSCs are specially the target for novel therapies, we will investigate in further studies whether AmotL2 inhibition is effective in the treatment of GB.

A transcriptomic roadmap to alpha- and beta cell differentiation in the embryonic pancreas

During pancreatic development, endocrine cells appear from the pancreatic epithelium when Neurog3 positive cells delaminate and differentiate into alpha, beta, gamma and delta cells. The mechanisms involved in this process are still incompletely understood. We characterized the temporal, lineage-specific developmental programs during pancreatic development by sequencing the transcriptome of thousands of individual pancreatic cells from embryonic day E12.5 to E18.5 in mice, and identified all known cell types that are present in the embryonic pancreas, but focused specifically on alpha and beta cell differentiation by enrichment of a MIP-GFP reporter. We characterized transcriptomic heterogeneity in the tip domain based on proliferation, and characterized two endocrine precursor clusters marked by expression of Neurog3 and Fev. Pseudotime analysis revealed specific branches for developing alpha- and beta cells, which allowed identification of specific gene regulation patterns. These include some known and many previously unreported genes that appear to define pancreatic cell fate transitions. This resource allows dynamic profiling of embryonic pancreas development at single cell resolution and reveals novel gene signatures during pancreatic differentiation into alpha and beta cells.

Endocrine lineage biases arise in temporally distinct endocrine progenitors during pancreatic morphogenesis

Decoding the molecular composition of individual Ngn3 + endocrine progenitors (EPs) during pancreatic morphogenesis could provide insight into the mechanisms regulating hormonal cell fate. Here, we identify population markers and extensive cellular diversity including four EP subtypes reflecting EP maturation using high-resolution single-cell RNA-sequencing of the e14.5 and e16.5 mouse pancreas. While e14.5 and e16.5 EPs are constantly born and share select genes, these EPs are overall transcriptionally distinct concomitant with changes in the underlying epithelium. As a consequence, e16.5 EPs are not the same as e14.5 EPs: e16.5 EPs have a higher propensity to form beta cells. Analysis of e14.5 and e16.5 EP chromatin states reveals temporal shifts, with enrichment of beta cell motifs in accessible regions at later stages. Finally, we provide transcriptional maps outlining the route progenitors take as they make cell fate decisions, which can be applied to advance the in vitro generation of beta cells.

Endocrine progenitors form early in pancreatic development but the diversity of this cell population is unclear. Here, the authors use single cell RNA sequencing of the mouse pancreas at e14.5 and e16.5 to show that endocrine progenitors are temporally distinct and those formed later are more likely to become beta cells

Hypoxia is involved in the reduction of HtrA3 in patients with endometrial hyperplasia and cancer

Endometrial cancer (EC) has recently become a major gynecological cancer and endometrial hyperplasia increases the risk for developing EC. Previous studies have reported that human high temperature requirement factor A3 (HtrA3), a member of ATP independent serine proteases family, is involved in endometrial carcinogenesis. However, the underlying mechanism of HtrA3 function is unclear in endometrial hyperplasia and cancer. In this study, we investigated that HtrA3 expression was reduced in endometrial hyperplasia as well as EC. The circulating levels of HtrA3 were also significantly reduced in both atypical hyperplasia and EC. Whether hypoxia is involved in the reduction of HtrA3 in EC was further investigated. Immunohistochemistry (IHC) scores of Glut1 and HtrA3 in type 1 and type 2 EC tissues showed the inverse correlation. And hypoxic condition reduced the expression of HtrA3. Furthermore, silencing HtrA3 promoted EC cell migration. Our study demonstrated the reduced levels of HtrA3 in endometrial hyperplasia including atypical hyperplasia which is a premalignant condition; and as the degree of hypoxia increases in EC, HtrA3 eventually loses its expression. Hypoxia is responsible for the reduction of HtrA3 which in turn promotes EC progression. These findings suggested that HtrA3 is an important adaptor in hypoxic regions that drives endometrial cancer development.

The physiological role of Motin family and its dysregulation in tumorigenesis

Members in Motin family, or Angiomotins (AMOTs), are adaptor proteins that localize in the membranous, cytoplasmic or nuclear fraction in a cell context-dependent manner. They control the bioprocesses such as migration, tight junction formation, cell polarity, and angiogenesis. Emerging evidences have demonstrated that AMOTs participate in cancer initiation and progression. Many of the previous studies have focused on the involvement of AMOTs in Hippo-YAP1 pathway. However, it has been controversial for years that AMOTs serve as either positive or negative growth regulators in different cancer types because of the various cellular origins. The molecular mechanisms of these opposite roles of AMOTs remain elusive. This review comprehensively summarized how AMOTs function physiologically and how their dysregulation promotes or inhibits tumorigenesis. Better understanding the functional roles of AMOTs in cancers may lead to an improvement of clinical interventions as well as development of novel therapeutic strategies for cancer patients.

A multigene support vector machine predictor for metastasis of cutaneous melanoma

Gene expression profiles of cutaneous melanoma were analyzed to identify critical genes associated with metastasis. Two gene expression datasets were downloaded from Gene Expression Omnibus (GEO) and another dataset was obtained from The Cancer Genome Atlas (TCGA). Differentially expression genes (DEGs) between metastatic and non‑metastatic melanoma were identified by meta‑analysis. A protein‑protein interaction (PPI) network was constructed for the DEGs using information from BioGRID, HPRD and DIP. Betweenness centrality (BC) was calculated for each node in the network and the top feature genes ranked by BC were selected to construct the support vector machine (SVM) classifier using the training set. The SVM classifier was then validated in another independent dataset. Pathway enrichment analysis was performed for the feature genes using Fisher's exact test. A total of 798 DEGs were identified and a PPI network including 337 nodes and 466 edges was then constructed. Top 110 feature genes ranked by BC were included in the SVM classifier. The prediction accuracies for the three datasets were 96.8, 100 and 94.4%, respectively. A total of 11 KEGG pathways and 13 GO biological pathways were significantly over‑represented in the 110 feature genes, including endometrial cancer, regulation of actin cytoskeleton, focal adhesion, ubiquitin mediated proteolysis, regulation of apoptosis and regulation of cell proliferation. A SVM classifier of high prediction accuracy was acquired. Several critical genes implicated in melanoms metastasis were also revealed. These results may advance understanding of the molecular mechanisms underlying metastasis, and also provide potential therapeutic targets.

Tropomyosin-related kinase C (TrkC) enhances podocyte migration by ERK-mediated WAVE2 activation

Podocyte malfunction is central to glomerular diseases and is marked by defective podocyte intercellular junctions and actin cytoskeletal dynamics. Podocytes share many morphologic features with neurons, so that similar sets of proteins appear to regulate cell process formation. One such protein is the tropomyosin-related kinase C (TrkC). TrkC deficiency in mice leads to proteinuria as a surrogate of defective kidney filter function. Activation of endogenous TrkC by its ligand neurotrophin-3 resulted in increased podocyte migration-a surrogate of podocyte actin dynamics in vivo. Employing a mutagenesis approach, we found that the Src homologous and collagen-like (Shc) binding site Tyr⁵¹⁶ within the TrkC cytoplasmic domain was necessary for TrkC-induced migration of podocytes. TrkC activation led to a mobility shift of Wiskott-Aldrich syndrome family verprolin-homologous protein (WAVE)-2 which is known to orchestrate Arp2/3 activation and actin polymerization. Chemical inactivation of Erk or mutagenesis of 2 of 4 known Erk target sites within WAVE2, Thr³⁴⁶ and Ser³⁵¹, abolished the TrkC-induced WAVE2 mobility shift. Knockdown of WAVE2 by shRNA abolished TrkC-induced podocyte migration. In summary, TrkC signals to the podocyte actin cytoskeleton to induce migration by phosphorylating WAVE2 Erk dependently. This signaling mechanism may be important for TrkC-mediated cytoskeletal dynamics in podocyte disease.-Gromnitza, S., Lepa, C., Weide, T., Schwab, A., Pavenstädt, H., George, B. Tropomyosin-related kinase C (TrkC) enhances podocyte migration by ERK-mediated WAVE2 activation.

The E-cadherin/AmotL2 complex organizes actin filaments required for epithelial hexagonal packing and blastocyst hatching

Epithelial cells connect via cell-cell junctions to form sheets of cells with separate cellular compartments. These cellular connections are essential for the generation of cellular forms and shapes consistent with organ function. Tissue modulation is dependent on the fine-tuning of mechanical forces that are transmitted in part through the actin connection to E-cadherin as well as other components in the adherens junctions. In this report we show that p100 amotL2 forms a complex with E-cadherin that associates with radial actin filaments connecting cells over multiple layers. Genetic inactivation or depletion of amotL2 in epithelial cells in vitro or zebrafish and mouse in vivo, resulted in the loss of contractile actin filaments and perturbed epithelial packing geometry. We further showed that AMOTL2 mRNA and protein was expressed in the trophectoderm of human and mouse blastocysts. Genetic inactivation of amotL2 did not affect cellular differentiation but blocked hatching of the blastocysts from the zona pellucida. These results were mimicked by treatment with the myosin II inhibitor blebbistatin. We propose that the tension generated by the E-cadherin/AmotL2/actin filaments plays a crucial role in developmental processes such as epithelial geometrical packing as well as generation of forces required for blastocyst hatching.

AmotL2 integrates polarity and junctional cues to modulate cell shape

The assembly of individual epithelial or endothelial cells into a tight cellular sheet requires stringent control of cell packing and organization. These processes are dependent on the establishment and further integration of cellular junctions, the cytoskeleton and the formation of apical-basal polarity. However, little is known how these subcellular events are coordinated. The (Angiomotin) Amot protein family consists of scaffold proteins that interact with junctional cadherins, polarity proteins and the cytoskeleton. In this report, we have studied how these protein complexes integrate to control cellular shapes consistent with organ function. Using gene-inactivating studies in zebrafish and cell culture systems in vitro, we show that Par3 to be essential for localization of AmotL2 to cellular junctions to associate with VE/E-cadherin and subsequently the organization of radial actin filaments. Our data provide mechanistic insight in how critical processes such as aortic lumen expansion as well as epithelial packing into hexagonal shapes are controlled.

Mechanisms of Cell Polarity-Controlled Epithelial Homeostasis and Immunity in the Intestine

Intestinal epithelial cell polarity is instrumental to maintain epithelial homeostasis and balance communications between the gut lumen and bodily tissue, thereby controlling the defense against gastrointestinal pathogens and maintenance of immune tolerance to commensal bacteria. In this review, we highlight recent advances with regard to the molecular mechanisms of cell polarity-controlled epithelial homeostasis and immunity in the human intestine.

Angiomotin Family Members: Oncogenes or Tumor Suppressors?

Angiomotin (Amot) family contains three members: Amot (p80 and p130 isoforms), Amot-like protein 1 (Amotl1), and Amot-like protein 2 (Amotl2). Amot proteins play an important role in tube formation and migration of endothelial cells and the regulation of tight junctions, polarity, and epithelial-mesenchymal transition in epithelial cells. Moreover, these proteins regulate the proliferation and migration of cancer cells. In most cancers, Amot family members promote the proliferation and invasion of cancer cells, including breast cancer, osteosarcoma, colon cancer, prostate cancer, head and neck squamous cell carcinoma, cervical cancer, liver cancer, and renal cell cancer. However, in glioblastoma, ovarian cancer, and lung cancer, Amot inhibits the growth of cancer cells. In addition, there are controversies on the regulation of Yes-associated protein (YAP) by Amot. Amot promotes either the internalization of YAP into the nucleus or the retention of YAP in the cytoplasm of different cell types. Moreover, Amot regulates the AMPK, mTOR, Wnt, and MAPK signaling pathways. However, it is unclear whether Amot is an oncogene or a tumor suppressor gene in different cellular processes. This review focuses on the multifunctional roles of Amot in cancers.

CRB3 downregulation confers breast cancer stem cell traits through TAZ/β-catenin

The cancer stem cell (CSC) theory depicts a special population within the cancer mass that self-renew and sustain the cancer, even if the other cells were eliminated by therapies. How CSCs acquire these unique traits is still unclear. Crumbs homolog 3 (CRB3), a member of the CRB polarity complex, has been reported to act as a tumor suppressor. Here, we detected significantly lower or negative CRB3 expression in human breast cancer tissues. Knockdown of CRB3 generated non-tumorigenic, immortalized breast epithelial cell line MCF 10A with CSC properties. Simultaneously, we found that CRB3 downregulation induced the epithelial–mesenchymal transition and activated TAZ (transcriptional co-activator with PDZ-binding motif) and β-catenin. Significantly, the activation of TAZ and β-catenin sufficed in conferring MCF 10A cells with CSC properties. This study demonstrates that cell polarity proteins may serve as a switch of the differentiated vs multipotent states in breast cancers.

Commitment of Scaffold Proteins in the Onco-Biology of Human Colorectal Cancer and Liver Metastases after Oxaliplatin-Based Chemotherapy

Scaffold proteins play pivotal roles in the regulation of signaling pathways, integrating external and internal stimuli to various cellular outputs. We report the pattern of cellular and subcellular expression of scaffoldins angiomotin-like 2 (AmotL2), FK506 binding protein 5 (FKBP51) and IQ motif containing GTPase-activating protein 1 (IQGAP1) in colorectal cancer (CRC) and metastases in liver resected after oxaliplatin-based chemotherapy (CT). Positive immunostaining for the three scaffoldins was found in most cells in healthy colon, tumor, healthy liver and metastasized liver. The patterns of expression of AmotL2, FKBP51 and IQGAP1 show the greatest variability in immune system cells and neurons and glia cells and the least in blood vessel cells. The simultaneous subcellular localization in tumor cells and other cell types within the tumor suggest an involvement of these three scaffoldins in cancer biology, including a role in Epithelial Mesenchymal Transition. The display in differential localization and quantitative expression of AmotL2, FKBP51, and IQGAP1 could be used as biomarkers for more accurate tumor staging and as potential targets for anti-cancer therapeutics by blocking or slowing down their interconnecting functions. Tough further research needs to be done in order to improve these assessments.

Epithelial Membrane Protein 2 and β1 integrin signaling regulate APC-mediated processes

Adenomatous Polyposis Coli (APC) plays a critical role in cell motility, maintenance of apical-basal polarity, and epithelial morphogenesis. We previously demonstrated that APC loss in Madin Darby Canine Kidney (MDCK) cells increases cyst size and inverts polarity independent of Wnt signaling, and upregulates the tetraspan protein, Epithelial Membrane Protein 2 (EMP2). Herein, we show that APC loss increases β1 integrin expression and migration of MDCK cells. Through 3D in vitro model systems and 2D migration analysis, we have depicted the molecular mechanism(s) by which APC influences polarity and cell motility. EMP2 knockdown in APC shRNA cells revealed that APC regulates apical-basal polarity and cyst size through EMP2. Chemical inhibition of β1 integrin and its signaling components, FAK and Src, indicated that APC controls cyst size and migration, but not polarity, through β1 integrin and its downstream targets. Combined, the current studies have identified two distinct and novel mechanisms required for APC to regulate polarity, cyst size, and cell migration independent of Wnt signaling.

Crumbs 3b promotes tight junctions in an ezrin-dependent manner in mammalian cells

Crumbs 3 (CRB3) is a component of epithelial junctions, which has been implicated in apical-basal polarity, apical identity, apical stability, cell adhesion, and cell growth. CRB3 undergoes alternative splicing to yield two variants: CRB3a and CRB3b. Here, we describe novel data demonstrating that, as with previous studies on CRB3a, CRB3b also promotes the formation of tight junctions (TJs). However, significantly we demonstrate that the 4.1-ezrin-radixin-moesin-binding motif of CRB3b is required for CRB3b functionality and that ezrin binds to the FBM of CRB3b. Furthermore, we show that ezrin contributes to CRB3b functionality and the correct distribution of TJ proteins. We demonstrate that both CRB3 isoforms are required for the production of functionally mature TJs and also the localization of ezrin to the plasma membrane. Finally, we demonstrate that reduced CRB3b expression in head and neck squamous cell carcinoma (HNSCC) correlates with cytoplasmic ezrin, a biomarker for aggressive disease, and shows evidence that while CRB3a expression has no effect, low CRB3b and high cytoplasmic ezrin expression combined may be prognostic for HNSCC.

The ZEB1/miR-200c feedback loop regulates invasion via actin interacting proteins MYLK and TKS5

Epithelial to mesenchymal transition (EMT) is a developmental process which is aberrantly activated during cancer invasion and metastasis. Elevated expression of EMT-inducers like ZEB1 enables tumor cells to detach from the primary tumor and invade into the surrounding tissue. The main antagonist of ZEB1 in controlling EMT is the microRNA-200 family that is reciprocally linked to ZEB1 in a double negative feedback loop. Here, we further elucidate how the ZEB1/miR-200 feedback loop controls invasion of tumor cells. The process of EMT is attended by major changes in the actin cytoskeleton. Via in silico screening of genes encoding for actin interacting proteins, we identified two novel targets of miR-200c - TKS5 and MYLK (MLCK). Co-expression of both genes with ZEB1 was observed in several cancer cell lines as well as in breast cancer patients and correlated with low miR-200c levels. Depletion of TKS5 or MYLK in breast cancer cells reduced their invasive potential and their ability to form invadopodia. Whereas TKS5 is known to be a major component, we could identify MYLK as a novel player in invadopodia formation. In summary, TKS5 and MYLK represent two mediators of invasive behavior of cancer cells that are regulated by the ZEB1/miR-200 feedback loop.

The RNF146 and tankyrase pathway maintains the junctional Crumbs complex through regulation of angiomotin

The Crumbs complex is an important determinant of epithelial apical-basal polarity that functions in regulation of tight junctions, resistance to epithelial-to-mesenchymal transitions and as a tumour suppressor. Although the functional role of the Crumbs complex is being elucidated, its regulation is poorly understood. Here, we show that suppression of RNF146, an E3 ubiquitin ligase that recognizes ADP-ribosylated substrates, and tankyrase, a poly(ADP-ribose) polymerase, disrupts the junctional Crumbs complex and disturbs the function of tight junctions. We show that RNF146 binds a number of polarity-associated proteins, in particular members of the angiomotin (AMOT) family. Accordingly, AMOT proteins are ADP-ribosylated by TNKS2, which drives ubiquitylation by RNF146 and subsequent degradation. Ablation of RNF146 or tankyrase, as well as overexpression of AMOT, led to the relocation of PALS1 (a Crumbs complex component) from the apical membrane to internal puncta, a phenotype that is rescued by AMOTL2 knockdown. We thus reveal a new function of RNF146 and tankyrase in stabilizing the Crumbs complex through downregulation of AMOT proteins at the apical membrane.

Single cell dual adherent-suspension co-culture micro-environment for studying tumor-stromal interactions with functionally selected cancer stem-like cells

Considerable evidence suggests that cancer stem-like cells (CSCs) are critical in tumor pathogenesis, but their rarity and transience has led to much controversy about their exact nature. Although CSCs can be functionally identified using dish-based tumorsphere assays, it is difficult to handle and monitor single cells in dish-based approaches; single cell-based microfluidic approaches offer better control and reliable single cell derived sphere formation. However, like normal stem cells, CSCs are heavily regulated by their microenvironment, requiring tumor-stromal interactions for tumorigenic and proliferative behaviors. To enable single cell derived tumorsphere formation within a stromal microenvironment, we present a dual adherent/suspension co-culture device, which combines a suspension environment for single-cell tumorsphere assays and an adherent environment for co-culturing stromal cells in close proximity by selectively patterning polyHEMA in indented microwells. By minimizing dead volume and improving cell capture efficiency, the presented platform allows for the use of small numbers of cells (<100 cells). As a proof of concept, we co-cultured single T47D (breast cancer) cells and primary cancer associated fibroblasts (CAF) on-chip for 14 days to monitor sphere formation and growth. Compared to mono-culture, co-cultured T47D have higher tumorigenic potential (sphere formation rate) and proliferation rates (larger sphere size). Furthermore, 96-multiplexed single-cell transcriptome analyses were performed to compare the gene expression of co-cultured and mono-cultured T47D cells. Phenotypic changes observed in co-culture correlated with expression changes in genes associated with proliferation, apoptotic suppression, tumorigenicity and even epithelial-to-mesechymal transition. Combining the presented platform with single cell transcriptome analysis, we successfully identified functional CSCs and investigated the phenotypic and transcriptome effects induced by tumor-stromal interactions.

Dynamic Change of Polarity in Primary Cultured Spheroids of Human Colorectal Adenocarcinoma and Its Role in Metastasis

Intestinal epithelial cells possess apical-basal polarity, which governs the exchange of nutrients and waste. Perturbation of cell polarity appears to be a general feature of cancers, although most colorectal cancers are differentiated adenocarcinomas, in which polarity is maintained to some extent. Little is known about the role of dysregulated polarity in cancer. The cancer tissue-originated spheroid method was applied to the preparation and culture of spheroids. Spheroids were cultured in suspension or in type I collagen gel. Polarity was assessed by IHC of apical markers and electron microscopy. Two types of polarity status in spheroids were observed: apical-in, with apical membrane located at cavities inside the spheroids in type I collagen gel; and apical-out, with apical membrane located at the outermost layer of spheroids in suspension. These polarities were highly interchangeable. Inhibitors of Src and dynamin attenuated the polarity switch. In patients, clusters of cancer cells that invaded vessels had both apical-in and apical-out morphologic features, whereas primary and metastatic tumors had apical-in features. In a mouse liver metastasis model, apical-out spheroids injected into the portal vein became apical-in spheroids in the liver within a few days. Inhibitors of Src and dynamin significantly decreased liver metastasis. Polarity switching was observed in spheroids and human cancer. The polarity switch was critical in an experimental liver metastasis model.