Appendiceal sessile serrated lesions are distinct from their right-sided colonic counterparts and may be precursors for appendiceal mucinous neoplasms

Low-grade appendiceal mucinous neoplasms (LAMNs) can occur concurrently with appendiceal sessile serrated lesions (SSLs). To interrogate relatedness, we performed multigene and immunohistochemical characterizations of paired and unpaired SSLs and LAMNs. We evaluated 62 serrated lesions from 50 appendectomy specimens for hotspot mutations in BRAF, KRAS and GNAS genes. Cases were subdivided into 3 groups: 20 unpaired SSLs, 18 unpaired LAMNs, and 12 with an SSL and concurrent LAMN. β-catenin and Annexin A10 immunostaining were performed on the SSL and LAMN components in the 12 paired cases, and fourteen colonic SSLs served as controls. There was no significant difference in KRAS hotspot mutation rates in appendiceal SSLs (17/26; 65.4%) and LAMNs (16/30; 53.3%) (p=0.42). BRAF V600E was identified in a single case (1/50; 2.0%) of SSL and concurrent LAMN (p=1.0). Mutations in GNAS were more common in LAMNs (6/30; 20.0%) compared to SSLs (1/31; 3.2%) (p=0.05). The molecular genotypes between paired SSLs and LAMNs were concordant in most cases (10/12; 83.3%). Annexin A10 immunostaining was significantly greater in colonic SSLs (14/14; 100%) compared to appendiceal SSLs (1/12; 8.3%) (p<0.0001). β-catenin immunostaining was significantly increased in LAMNs (10/12; 83.3%) compared to their paired appendiceal SSLs (2/12; 16.7%)(p=0.003). Overall, appendiceal sessile serrated lesions are predominantly driven by KRAS mutations and are not characterized by Annexin A10 immunostaining. Our data suggests that at least a subset of LAMNs may arise from a precursor SSL in which GNAS mutations and/or upregulation of the WNT-signaling pathway are likely key events modulating this progression.

Bilateral Meningioma: A Case Report and Review of the Literature

Here, we present a rarely seen example of bilateral meningiomas exhibiting different malignancy grades, I (meningothelial) and II (atypical), recorded in a 72-year-old patient. The presence of two separated lesions of different grades in a single patient can elucidate meningioma progression. To this end, the involvement of specific protein markers of epithelial to mesenchymal transition (EMT), the process responsible for progression, was tested in both tumors. Protein expression status of specific epithelial (E-cadherin) and mesenchymal markers (N-cadherin, SNAIL&SLUG and TWIST1) was investigated. Furthermore, markers that are connected to Wnt signaling pathway–beta-catenin, GSK3beta and DVL1—were also analyzed. For signs of neurofibromatosis and schwanomatosis genetic testing was performed. Immunohistochemistry evaluated by immunoreactivity score (IRS) was used to determine the signal strengths and proteins’ location. Our results indicated that, in comparison to the grade I tumor, mesenchymal markers SNAIL and SLUG were upregulated in the atypical meningioma. TWIST1, beta-catenin and GSK3beta were upregulated in both grades, while E-cadherin was partially lost. A pronounced cadherin switch could not be established; however, N-cadherin showed widespread tissue presence. Genetic testing did not detect changes of NF2 or SMARCB1 genes denying germline origin of the lesions. The rare presence of two different grades in one patient elucidate previously unknown molecules involved in meningioma progression.

Ovarian microcystic stromal tumour: From morphological observations to syndromic associations

Microcystic stromal tumour (MST) is a rare, usually benign, ovarian neoplasm characterised morphologically in its classic form by a distinctive triad of features comprising microcysts, solid cellular regions and fibrous stroma. Variant morphology also occurs, including the presence of nests, tubules, cords, and signet ring cells. Immunohistochemically, this neoplasm is characterised by diffuse nuclear expression of β-catenin, cyclin D1, WT1 and SF1, as well as diffuse staining with FOXL2 and CD10. Inhibin and calretinin are typically negative. At the genomic level, these neoplasms harbour mutually exclusive mutations in CTNNB1 or APC genes with the former being significantly more common. This molecular characteristic raises possible links to other rare ovarian lesions including solid pseudopapillary tumour, signet-ring stromal tumour and Sertoli cell tumour. Rarely, MST is an extracolonic manifestation of familial adenomatous polyposis (FAP) and serves as a sentinel event that could trigger the identification of the syndrome. Herein, we review the published literature on ovarian MST and provide practical advice for pathologists reporting these rare neoplasms.

Cytotoxic Evaluation and Molecular Docking studies of Aminopyridine derivatives as Potential Anticancer Agents

BACKGROUND

The development of resistance to available anticancer drugs is increasingly becoming a major challenge and new chemical entities could be unveiled to compensate for this therapeutic failure.

OBJECTIVES

The current study demonstrated whether N-protected and deprotected amino acid derivatives of 2-aminopyridine could attenuate tumor development using colorectal cancer cell lines.

METHODS

Biological assays were performed to investigate the anticancer potential of synthesized compounds. The in silico ADME profiling and docking studies were also performed by docking the designed compounds against the active binding site of beta-catenin (CTNNB1) to analyze the binding mode of these compounds. Four derivatives 4a, 4b, 4c, and 4d were selected for investigation of in vitro anticancer potential using colorectal cancer cell line HCT 116. The anti-tumor activities of synthesized compounds were further validated by evaluating the inhibitory effects of these compounds on the target protein beta-catenin through in vitro enzyme inhibitory assay.

RESULTS

The docking analysis revealed favorable binding energies and interactions with the target proteins. The in vitro MTT assay on colorectal cancer cell line HCT 116 and HT29 revealed potential anti-tumor activities with an IC50 range of 3.7-8.1µM and 3.27-7.7 µM, respectively. The inhibitory properties of these compounds on the concentration of beta-catenin by ELISA revealed significant percent inhibition of target protein at 100 µg/ml.

CONCLUSION

In conclusion, the synthesized compounds showed significant anti-tumor activities both in silico and in vitro, having potential for further investigating its role in colorectal cancer.

β-Catenin Limits Osteogenesis on Regenerative Materials in a Stiffness-Dependent Manner

Targeted refinement of regenerative materials requires mechanistic understanding of cell-material interactions. The nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) scaffold is shown to promote skull regeneration in vivo without additive exogenous growth factors or progenitor cells, suggesting potential for clinical translation. This work evaluates modulation of MC-GAG stiffness on canonical Wnt (cWnt) signaling. Primary human bone marrow-derived mesenchymal stem cells (hMSCs) are differentiated on two MC-GAG scaffolds (noncrosslinked, NX-MC, 0.3 kPa vs conventionally crosslinked, MC, 3.9 kPa). hMSCs increase expression of activated β-catenin, the major cWnt intracellular mediator, and the mechanosensitive YAP protein with near complete subcellular colocalization on stiffer MC scaffolds. Overall Wnt pathway inhibition reduces activated β-catenin and osteogenic differentiation, while elevating BMP4 and phosphorylated Smad1/5 (p-Smad1/5) expression on MC, but not NX-MC. Unlike Wnt pathway downregulation, isolated canonical Wnt inhibition with β-catenin knockdown increases osteogenic differentiation and mineralization specifically on the stiffer MC. β-catenin knockdown also increases p-Smad1/5, Runx2, and BMP4 expression only on the stiffer MC material. Thus, while stiffness-induced activation of the Wnt and mechanotransduction pathways promotes osteogenesis on MC-GAG, activated β-catenin is a limiting agent and may serve as a useful target or readout for optimal modulation of stiffness in skeletal regenerative materials.

Trends in diagnostic and therapeutic strategies for extra-abdominal desmoid-type fibromatosis: Japanese musculoskeletal oncology group questionnaire survey

OBJECTIVE

The mainstay of treatment modality for extra-abdominal desmoid-type fibromatosis (DF) has shifted from surgery, which often impairs ADL/QOL, to conservative treatment including active surveillance. In the present study, we conducted a longitudinal survey on the diagnosis and treatment of DF at facilities belonging to the Japanese Musculoskeletal Oncology Group, which is a research group of facilities specializing in the treatment of bone and soft tissue tumors in Japan to clarify the transition of medical care for extra-abdominal DF.

METHODS

The same questionnaire was administered in 2015 and 2018, and responses were obtained from 46 (69%) of 67 facilities and 42 (53%) of 80 facilities in 2015 and 2018, respectively.

RESULTS

Although immunostaining for β-catenin was often used for the pathological diagnosis in both 2015 and 2018, CTNNB1 mutation analysis was not performed either in 2015 or in 2018. As for the treatment strategy for resectable cases, surgical treatment including wide resection was selected at 11 facilities (24% of respondents) in 2015, and further decreased to 5 facilities (12%) in 2018. Conservative treatment with active surveillance or medical treatment was the most common treatment for both resectable and difficult-to-resect cases. COX-2 inhibitors and tranilast were often used in the drug treatment of both resectable and difficult-to-resect cases. Few facilities provided radiotherapy, methotrexate and vinblastine, or DOX-based chemotherapy for refractory cases in both 2015 and 2018.

CONCLUSIONS

A good trend was found in the questionnaire survey. It will be further necessary to disseminate clinical practice guidelines to physicians more widely, and to have them understand and implement the most up-to-date medical practice strategies for this rare disease.

β-Catenin-NF-κB-CFTR interactions in cholangiocytes regulate inflammation and fibrosis during ductular reaction

Expansion of biliary epithelial cells (BECs) during ductular reaction (DR) is observed in liver diseases including cystic fibrosis (CF), and associated with inflammation and fibrosis, albeit without complete understanding of underlying mechanism. Using two different genetic mouse knockouts of β-catenin, one with β-catenin loss is hepatocytes and BECs (KO1), and another with loss in only hepatocytes (KO2), we demonstrate disparate long-term repair after an initial injury by 2-week choline-deficient ethionine-supplemented diet. KO2 show gradual liver repopulation with BEC-derived β-catenin-positive hepatocytes and resolution of injury. KO1 showed persistent loss of β-catenin, NF-κB activation in BECs, progressive DR and fibrosis, reminiscent of CF histology. We identify interactions of β-catenin, NFκB, and CF transmembranous conductance regulator (CFTR) in BECs. Loss of CFTR or β-catenin led to NF-κB activation, DR, and inflammation. Thus, we report a novel β-catenin-NFκB-CFTR interactome in BECs, and its disruption may contribute to hepatic pathology of CF.

The liver has an incredible capacity to repair itself or ‘regenerate’ – that is, it has the ability to replace damaged tissue with new tissue. In order to do this, the organ relies on hepatocytes (the cells that form the liver) and bile duct cells (the cells that form the biliary ducts) dividing and transforming into each other to repair and replace damaged tissue, in case the insult is dire.

During long-lasting or chronic liver injury, bile duct cells undergo a process called ‘ductular reaction’, which causes the cells to multiply and produce proteins that stimulate inflammation, and can lead to liver scarring (fibrosis). Ductular reaction is a hallmark of severe liver disease, and different diseases exhibit ductular reactions with distinct features. For example, in cystic fibrosis, a unique type of ductular reaction occurs at late stages, accompanied by both inflammation and fibrosis. Despite the role that ductular reaction plays in liver disease, it is not well understood how it works at the molecular level.

Hu et al. set out to investigate how a protein called β-catenin – which can cause many types of cells to proliferate – is involved in ductular reaction. They used three types of mice for their experiments: wild-type mice, which were not genetically modified; and two strains of genetically modified mice. One of these mutant mice did not produce β-catenin in biliary duct cells, while the other lacked β-catenin both in biliary duct cells and in hepatocytes.

After a short liver injury – which Hu et al. caused by feeding the mice a specific diet – the wild-type mice were able to regenerate and repair the liver without exhibiting any ductular reaction. The mutant mice that lacked β-catenin in hepatocytes showed a temporary ductular reaction, and ultimately repaired their livers by turning bile duct cells into hepatocytes. On the other hand, the mutant mice lacking β-catenin in both hepatocytes and bile duct cells displayed sustained ductular reactions, inflammation and fibrosis, which looked like that seen in patients with liver disease associated to cystic fibrosis. Further probing showed that β-catenin interacts with a protein called CTFR, which is involved in cystic fibrosis. When bile duct cells lack either of these proteins, another protein called NF-B gets activated, which causes the ductular reaction, leading to inflammation and fibrosis.

The findings of Hu et al. shed light on the role of β-catenin in ductular reaction. Further, the results show a previously unknown interaction between β-catenin, CTFR and NF-B, which could lead to better treatments for cystic fibrosis in the future.

The Wnt signaling pathway in tumorigenesis, pharmacological targets, and drug development for cancer therapy

Wnt signaling was initially recognized to be vital for tissue development and homeostasis maintenance. Further studies revealed that this pathway is also important for tumorigenesis and progression. Abnormal expression of signaling components through gene mutation or epigenetic regulation is closely associated with tumor progression and poor prognosis in several tissues. Additionally, Wnt signaling also influences the tumor microenvironment and immune response. Some strategies and drugs have been proposed to target this pathway, such as blocking receptors/ligands, targeting intracellular molecules, beta-catenin/TCF4 complex and its downstream target genes, or tumor microenvironment and immune response. Here we discuss the roles of these components in Wnt signaling pathway in tumorigenesis and cancer progression, the underlying mechanisms that is responsible for the activation of Wnt signaling, and a series of drugs targeting the Wnt pathway provide multiple therapeutic values. Although some of these drugs exhibit exciting anti-cancer effect, clinical trials and systematic evaluation should be strictly performed along with multiple-omics technology.

Detection of CTNNB1 Hotspot Mutations in Cell-Free DNA from the Urine of Hepatocellular Carcinoma Patients

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide. The beta-catenin gene, CTNNB1, is among the most frequently mutated in HCC tissues. However, mutational analysis of HCC tumors is hampered by the difficulty of obtaining tissue samples using traditional biopsy. Here, we explored the feasibility of detecting tumor-derived CTNNB1 mutations in cell-free DNA (cfDNA) extracted from the urine of HCC patients. Using a short amplicon qPCR assay targeting HCC mutational hotspot CTNNB1 codons 32-37 (exon 3), we detected CTNNB1 mutations in 25% (18/73) of HCC tissues and 24% (15/62) of pre-operative HCC urine samples in two independent cohorts. Among the CTNNB1-mutation-positive patients with available matched pre- and post-operative urine (n = 13), nine showed apparent elimination (n = 7) or severalfold reduction (n = 2) of the mutation in urine following tumor resection. Four of the seven patients with no detectable mutations in postoperative urine remained recurrence-free within five years after surgery. In contrast, all six patients with mutation-positive in post-operative urine recurred, including the two with reduced mutation levels. This is the first report of association between the presence of CTNNB1 mutations in pre- and post-operative urine cfDNA and HCC recurrence with implications for minimum residual disease detection.

M01 as a novel drug enhancer for specifically targeting the blood-brain barrier

Drug delivery to the brain is limited for most pharmaceuticals by the blood-brain barrier (BBB) where claudin-5 dominates the paraendothelial tightening. For circumventing the BBB, we identified the compound M01 as a claudin-5 interaction inhibitor. M01 causes transient permeabilisation of the BBB depending on the concentration of small molecules in different cell culture models within 3 to 48 h. In mice, brain uptake of fluorescein peaked within the first 3 h after M01 injection and normalised within 48 h. Compared to the cytostatic paclitaxel alone, M01 improved delivery of paclitaxel to mouse brain and reduced orthotopic glioblastoma growth. Results on interactions of M01 with claudin-5 were incorporated into a binding model which suggests association of its aromatic parts with highly conserved residues of the extracellular domain of claudin-5 and adjacent transmembrane segments. Our results indicate the following mode of action: M01 preferentially binds to the extracellular claudin-5 domain, which weakens trans-interactions between adhering cells. Further decrease in membranous claudin-5 levels due to internalization and transcriptional downregulation enables the paracellular passage of small molecules. In summary, the first small molecule is introduced here as a drug enhancer, which specifically permeabilises the BBB for a sufficient interval for allowing neuropharmaceuticals to enter the brain.

WNT Signaling as a Therapeutic Target for Glioblastoma

The WNT (Wingless/Integrated) signaling pathway is implicated in various stages of glioblastoma, which is an aggressive brain tumor for which therapeutic options are limited. WNT has been recognized as a hallmark of therapeutic challenge due to its context-dependent role and critical function in healthy tissue homeostasis. In this review, we deeply scrutinize the WNT signaling pathway and its involvement in the genesis of glioblastoma as well as its acquired therapy resistance. We also provide an analysis of the WNT pathway in terms of its therapeutic importance in addition to an overview of the current targeted therapies under clinical investigation.

Evaluation of β-Catenin Inhibition of Axitinib and Nitazoxanide in Human Monocyte-Derived Dendritic Cells

Modulation of β-catenin signaling has attractive therapeutic potential in cancer immunotherapy. Several studies have found that β-catenin can mediate immune evasion in cancer and promote anti-inflammatory features of antigen-presenting dendritic cells. Many small molecular compounds that inhibit Wnt/β-catenin signaling are currently in clinical development, but none have entered routine clinical use. New inhibitors of β-catenin signaling are consequently desirable. Here, we have tested, in monocyte-derived dendritic cells, the effects of two small molecular compounds, axitinib and nitazoxanide, that previously have been discovered to inhibit β-catenin signaling in colon cancer cells. Immature and lipopolysaccharide-matured dendritic cells prepared from healthy blood donor buffy coats were stimulated with 6-bromoindirubin-3′-oxime (6-BIO) to boost basal β-catenin activity, and the effects of axitinib and nitazoxanide were compared with the commercial β-catenin inhibitor ICG-001. Assays, including genome-wide RNA-sequencing, indicated that neither axitinib nor nitazoxanide demonstrated considerable β-catenin inhibition. Both compounds were found to be less toxic to monocyte-derived dendritic cells than either 6-BIO or ICG-001. Axitinib stimulated several aspects of dendritic cell function, such as IL12-p70 secretion, and counteracted IL-10 secretion, according to the present study. However, neither axitinib nor nitazoxanide were found to be efficient β-catenin inhibitors in monocyte-derived dendritic cells.

Study on the effect and mechanism of NFKBIA on cervical cancer progress in vitro and in vivo

AIM

NFKBIA is frequently encountered. However, its expression and relevance of the proliferation, invasion, and migration in human cervical cancer (CC) remain unclear. The role and novel mechanism of NFKBIA in CC progression were investigated in this study.

METHODS

We analyzed the expression of NFKBIA in CC and adjacent normal tissues and explored the proliferation, migration, and invasion of HeLa cells by treating with either wild-type NFKBIA plasmid or NFKBIA siRNA. Effect of NFKBIA on the epithelial-mesenchymal transition (EMT) and the β-catenin-mediated transcription of target genes were evaluated subsequently.

RESULTS

NFKBIA expression was lower in CC tissues than that of adjacent tissues. An obvious dysregulation of NFKBIA overexpression was revealed in CC cell proliferation, invasion, and migration, which differed from the effect of knockdown NFKBIA. NFKBIA overexpression facilitated the expression of both phosphorylated β-catenin and E-cadherin protein. It inhibited the expression of vimentin, TWIST, as well as downstream targets of β-catenin including c-MYC, TCF-4 and MMP14. Conversely, NFKBIA silencing elevated the expression of c-MYC, TCF-4, and MMP14, and promoted the EMT in HeLa cells. Both endogenous and exogenous NFKBIA interacted with β-catenin. Moreover, β-catenin overexpression stemmed effects of NFKBIA on the proliferation, migration, and invasion of HeLa cells. By overexpressing NFKBIA in vivo, the volume and size of tumors were notably decreased, while no obvious alteration was found in mice body weight.

CONCLUSION

By inhibiting β-catenin-mediated transcription, NFKBIA functioning as a tumor suppressor might be introduced as a novel anti-metastatic agent for the treatment of targeted CC.

Lobular Breast Cancer: Histomorphology and Different Concepts of a Special Spectrum of Tumors

Simple Summary

Invasive lobular breast cancer (ILC) is a special type of breast cancer (BC) that was first described in 1941. The diagnosis of ILC is made by microscopy of tumor specimens, which reveals a distinct morphology. This review recapitulates the developments in the microscopic assessment of ILC from 1941 until today. We discuss different concepts of ILC, provide an overview on ILC variants, and highlight advances which have contributed to a better understanding of ILC as a special histologic spectrum of tumors.

Abstract

Invasive lobular breast cancer (ILC) is the most common special histological type of breast cancer (BC). This review recapitulates developments in the histomorphologic assessment of ILC from its beginnings with the seminal work of Foote and Stewart, which was published in 1941, until today. We discuss different concepts of ILC and their implications. These concepts include (i) BC arising from mammary lobules, (ii) BC growing in dissociated cells and single files, and (iii) BC defined as a morpho-molecular spectrum of tumors with distinct histological and molecular characteristics related to impaired cell adhesion. This review also provides a comprehensive overview of ILC variants, their histomorphology, and differential diagnosis. Furthermore, this review highlights recent advances which have contributed to a better understanding of the histomorphology of ILC, such as the role of the basal lamina component laminin, the molecular specificities of triple-negative ILC, and E-cadherin to P-cadherin expression switching as the molecular determinant of tubular elements in CDH1-deficient ILC. Last but not least, we provide a detailed account of the tumor microenvironment in ILC, including tumor infiltrating lymphocyte (TIL) levels, which are comparatively low in ILC compared to other BCs, but correlate with clinical outcome. The distinct histomorphology of ILC clearly reflects a special tumor biology. In the clinic, special treatment strategies have been established for triple-negative, HER2-positive, and ER-positive BC. Treatment specialization for patients diagnosed with ILC is just in its beginnings. Accordingly, ILC deserves greater attention as a special tumor entity in BC diagnostics, patient care, and cancer research.

Regulation of Wnt Signaling by FOX Transcription Factors in Cancer

Simple Summary

Cancer is caused by a breakdown of cell-to-cell communication, which results in the unrestricted expansion of cells within a tissue. In many cases, tumor growth is maintained by the continuous activation of cell signaling programs that normally drive embryonic development and wound repair. In this review article, I discuss how one of the largest human protein families, namely FOX proteins, controls the activity of the Wnt pathway, a major regulatory signaling cascade in developing organisms and adult stem cells. Evidence suggests that there is considerable crosstalk between FOX proteins and the Wnt pathway, which contributes to cancer initiation and progression. A better understanding of FOX biology may therefore lead to the development of new targeted treatments for many types of cancer.

Abstract

Aberrant activation of the oncogenic Wnt signaling pathway is a hallmark of numerous types of cancer. However, in many cases, it is unclear how a chronically high Wnt signaling tone is maintained in the absence of activating pathway mutations. Forkhead box (FOX) family transcription factors are key regulators of embryonic development and tissue homeostasis, and there is mounting evidence that they act in part by fine-tuning the Wnt signaling output in a tissue-specific and context-dependent manner. Here, I review the diverse ways in which FOX transcription factors interact with the Wnt pathway, and how the ectopic reactivation of FOX proteins may affect Wnt signaling activity in various types of cancer. Many FOX transcription factors are partially functionally redundant and exhibit a highly restricted expression pattern, especially in adults. Thus, precision targeting of individual FOX proteins may lead to safe treatment options for Wnt-dependent cancers.

Quantitative live-cell imaging and computational modeling shed new light on endogenous WNT/CTNNB1 signaling dynamics

WNT/CTNNB1 signaling regulates tissue development and homeostasis in all multicellular animals, but the underlying molecular mechanism remains incompletely understood. Specifically, quantitative insight into endogenous protein behavior is missing. Here, we combine CRISPR/Cas9-mediated genome editing and quantitative live-cell microscopy to measure the dynamics, diffusion characteristics and absolute concentrations of fluorescently tagged, endogenous CTNNB1 in human cells under both physiological and oncogenic conditions. State-of-the-art imaging reveals that a substantial fraction of CTNNB1 resides in slow-diffusing cytoplasmic complexes, irrespective of the activation status of the pathway. This cytoplasmic CTNNB1 complex undergoes a major reduction in size when WNT/CTNNB1 is (hyper)activated. Based on our biophysical measurements, we build a computational model of WNT/CTNNB1 signaling. Our integrated experimental and computational approach reveals that WNT pathway activation regulates the dynamic distribution of free and complexed CTNNB1 across different subcellular compartments through three regulatory nodes: the destruction complex, nucleocytoplasmic shuttling, and nuclear retention.

Cutaneous desmoid-type fibromatosis: A rare case with molecular profiling

Fibromatoses encompass a broad group of histopathologically similar fibroblastic/myofibroblastic proliferations with divergent clinical manifestations and behavior. Deep (desmoid-type) fibromatoses are typically large, rapidly growing, and locally aggressive tumors that occur in the abdominal wall, mesentery, and extra-abdominal soft tissue, principally the musculature of the trunk and extremities. Most sporadic cases of desmoid fibromatosis harbor inactivating mutations in CTNNB1, the gene encoding beta-catenin. Tumors occurring in the context of familial adenomatous polyposis and Gardner syndrome bear inactivating mutations in APC. By contrast, mutations in CTNNB1 or APC have not been identified in cases of superficial fibromatosis. Cutaneous involvement by desmoid fibromatosis is exceedingly rare. Here we present a 78-year-old male with desmoid-type fibromatosis arising in the dermis of the right medial calf with a pathogenic mutation in CTNNB1 and a variant of unknown significance in APC.

High glucose promotes the aging of human dental pulp cells through Wnt/beta-catenin signaling

BACKGROUND

Diabetes is one of the most common metabolic diseases that disrupt the functioning of different body organs, including oral tissue. Some diabetic complications remain even after the control of the hyperglycemic condition. The adverse effect of hyperglycemia on the pulp structure and function has been shown previously.

OBJECTIVES

The purpose of this study was to investigate the effect of the hyperglycemic state on the aging of pulp cells and evaluate the role of Wnt signaling as the underlying mechanism of this process.

MATERIAL AND METHODS

The isolated pulp cells were cultured in the Minimum Essential Medium (MEM)-alpha for 7, 14 and 21 days under the influence of glucose at concentrations of 5 mM, 20 mM and 30 mM. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate cell viability, the beta-galactosidase test was applied to assess cellular senescence and gene expression was measured with quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The results of this study showed that cell proliferation decreased following exposure to 20 and 30 mM glucose, which was accompanied by an increased number of senescent cells and an increased p21 expression. There was a significant increase in beta-catenin and Wnt1 expression in response to high glucose. Treatment with beta-catenin inducer enhanced cellular aging in the hyperglycemic state, while betacatenin inhibitor decreased the senescence response.

CONCLUSIONS

The present study further confirmed the effect of the high-glucose condition on pulp cell aging and suggests a role for beta-catenin in the induction of cellular aging. Targeting the key regulators of cellular aging in pulp tissue might lead to the development of new therapies for the prevention and treatment of endodontic complications in diabetic patients.

Parallel and Sequential Pathways of Molecular Recognition of a Tandem-Repeat Protein and Its Intrinsically Disordered Binding Partner

The Wnt signalling pathway plays an important role in cell proliferation, differentiation, and fate decisions in embryonic development and the maintenance of adult tissues. The twelve armadillo (ARM) repeat-containing protein β-catenin acts as the signal transducer in this pathway. Here, we investigated the interaction between β-catenin and the intrinsically disordered transcription factor TCF7L2, comprising a very long nanomolar-affinity interface of approximately 4800 Å2 that spans ten of the twelve ARM repeats of β-catenin. First, a fluorescence reporter system for the interaction was engineered and used to determine the kinetic rate constants for the association and dissociation. The association kinetics of TCF7L2 and β-catenin were monophasic and rapid (7.3 ± 0.1 × 107 M-1·s-1), whereas dissociation was biphasic and slow (5.7 ± 0.4 × 10-4 s-1, 15.2 ± 2.8 × 10-4 s-1). This reporter system was then combined with site-directed mutagenesis to investigate the striking variability in the conformation adopted by TCF7L2 in the three different crystal structures of the TCF7L2-β-catenin complex. We found that the mutation had very little effect on the association kinetics, indicating that most interactions form after the rate-limiting barrier for association. Mutations of the N- and C-terminal subdomains of TCF7L2 that adopt relatively fixed conformations in the crystal structures had large effects on the dissociation kinetics, whereas the mutation of the labile sub-domain connecting them had negligible effect. These results point to a two-site avidity mechanism of binding with the linker region forming a "fuzzy" complex involving transient contacts that are not site-specific. Strikingly, the two mutations in the N-terminal subdomain that had the largest effects on the dissociation kinetics showed two additional phases, indicating partial flux through an alternative dissociation pathway that is inaccessible to the wild type. The results presented here provide insights into the kinetics of the molecular recognition of a long intrinsically disordered region with an elongated repeat-protein surface, a process found to involve parallel routes with sequential steps in each.

The structural biology of canonical Wnt signalling

The Wnt signalling pathways are of great importance in embryonic development and oncogenesis. Canonical and non-canonical Wnt signalling pathways are known, with the canonical (or β-catenin dependent) pathway being perhaps the best studied of these. While structural knowledge of proteins and interactions involved in canonical Wnt signalling has accumulated over the past 20 years, the pace of discovery has increased in recent years, with the structures of several key proteins and assemblies in the pathway being released. In this review, we provide a brief overview of canonical Wnt signalling, followed by a comprehensive overview of currently available X-ray, NMR and cryoEM data elaborating the structures of proteins and interactions involved in canonical Wnt signalling. While the volume of structures available is considerable, numerous gaps in knowledge remain, particularly a comprehensive understanding of the assembly of large multiprotein complexes mediating key aspects of pathway, as well as understanding the structure and activation of membrane receptors in the pathway. Nonetheless, the presently available data affords considerable opportunities for structure-based drug design efforts targeting canonical Wnt signalling.

Beta-Catenin Causes Adrenal Hyperplasia by Blocking Zonal Transdifferentiation

Activating mutations in the canonical Wnt/β-catenin pathway are key drivers of hyperplasia, the gateway for tumor development. In a wide range of tissues, this occurs primarily through enhanced effects on cellular proliferation. Whether additional mechanisms contribute to β-catenin-driven hyperplasia remains unknown. The adrenal cortex is an ideal system in which to explore this question, as it undergoes hyperplasia following somatic β-catenin gain-of-function (βcat-GOF) mutations. Targeting βcat-GOF to zona Glomerulosa (zG) cells leads to a progressive hyperplastic expansion in the absence of increased proliferation. Instead, we find that hyperplasia results from a functional block in the ability of zG cells to transdifferentiate into zona Fasciculata (zF) cells. Mechanistically, zG cells demonstrate an upregulation of Pde2a, an inhibitor of zF-specific cAMP/PKA signaling. Hyperplasia is further exacerbated by trophic factor stimulation leading to organomegaly. Together, these data indicate that β-catenin drives adrenal hyperplasia through both proliferation-dependent and -independent mechanisms.

Using the adrenal cortex as a model for slow-cycling tissues, Pignatti et al. show that activation of the canonical Wnt/β-catenin pathway leads to tissue hyperplasia by blocking cellular differentiation/cell-fate commitment, independent of its effects on cellular proliferation.

RAB7A Regulates Vimentin Phosphorylation through AKT and PAK

Simple Summary

RAB7A (RAs-related in Brain 7A) is a master regulator of intracellular traffic controlling transport to late endosomes and lysosomes, two organelles of the endocytic pathway important for degradation. Thanks to this function, RAB7A is also involved in cellular processes linked to cancer, such as apoptosis, cytoskeletal reorganization, and cell migration. Therefore, the interest in the role of RAB7A in cancer progression is increasing. Previously, we demonstrated that RAB7A regulates phosphorylation and assembly of vimentin, a cytoskeletal intermediate filament protein, which is also an important mesenchymal marker of cancer cells. The aim of the present study is the identification of the kinases responsible for vimentin phosphorylation whose activity is affected by the modulation of RAB7A expression. We found that RAB7A is able to regulate AKT (also called protein kinase B or PKB) and PAK1 (P21-Activated Kinase 1) and several of their downstream effectors, which control proliferation, apoptosis, survival, migration, and invasion. These data suggest that RAB7A could have a key role in cancer development.

Abstract

RAB7A is a small GTPase that controls the late endocytic pathway but also cell migration through RAC1 (Ras-related C3 botulinum toxin substrate 1) and vimentin. In fact, RAB7A regulates vimentin phosphorylation at different sites and vimentin assembly, and, in this study, we identified vimentin domains interacting with RAB7A. As several kinases could be responsible for vimentin phosphorylation, we investigated whether modulation of RAB7A expression affects the activity of these kinases. We discovered that RAB7A regulates AKT and PAK1, and we demonstrated that increased vimentin phosphorylation at Ser38 (Serine 38), observed upon RAB7A overexpression, is due to AKT activity. As AKT and PAK1 are key regulators of several cellular events, we investigated if RAB7A could have a role in these processes by modulating AKT and PAK1 activity. We found that RAB7A protein levels affected beta-catenin and caspase 9 expression. We also observed the downregulation of cofilin-1 and decreased matrix metalloproteinase 2 (MMP2) activity upon RAB7A silencing. Altogether these results demonstrate that RAB7A regulates AKT and PAK1 kinases, affecting their downstream effectors and the processes they regulate, suggesting that RAB7A could have a role in a number of cancer hallmarks.

A comparison of the usefulness of nuclear beta-catenin in the diagnosis of desmoid-type fibromatosis among commonly used anti-beta-catenin antibodies

Desmoid-type fibromatosis (DF) is a locally aggressive but non-metastatic (myo)fibroblastic neoplasm. A hallmark of the tumor is nuclear positivity for beta-catenin in immunohistochemistry due mostly to CTNNB1 mutations. However, a recent study has reported that even beta-catenin 'nuclear-negative' DFs can harbor CTNNB1 mutations and that the positive ratio of nuclear beta-catenin in DF is different among antibodies. Here, we reviewed soft tissue lesions for which the possibility of DF was considered and compared the sensitivity and specificity of nuclear beta-catenin for the diagnosis of DF among commonly used anti-beta-catenin antibodies, i.e., clone beta-catenin 1, 17C2 and 14. We analyzed 26 cases of DF, 28 cases of benign fibroblastic lesions, and 27 cases of other soft tissue tumors. The sensitivity and specificity of nuclear beta-catenin for the diagnosis of DF were different among antibodies; 54% and 98% in clone beta-catenin 1, 85% and 84% in 17C2, and 96% and 62% in 14. IHC of LEF1 showed comparable results with IHC of beta-catenin, with a sensitivity of 88% and specificity of 76%. Additionally, when beta-catenin 1 was used, DFs showed characteristic dotted cytoplasmic staining, often appearing as rings. Our results might be helpful for making a correct diagnosis of DF.