beta-catenin and its regulatory network

β-Catenin/c-Myc Axis Modulates Autophagy Response to Different Ammonia Concentrations

Ammonia a by-product of nitrogen containing molecules is detoxified by liver into non-toxic urea and glutamine. Impaired ammonia detoxification leads to hyperammonemia. Ammonia has a dual role on autophagy, it acts as inducer at low concentrations and as inhibitor at high concentrations. However, little is known about the mechanisms responsible for this switch. Wnt/β-catenin signalling is emerging for its role in the regulation of ammonia metabolizing enzymes and autophagosome synthesis through c-Myc. Here, using Huh7 cell line, we show a modulation in c-Myc expression under different ammonia concentrations. An increase in c-Myc expression and in its transcriptional regulator β-catenin was detected at low concentrations of ammonia, when autophagy is active, whereas these modifications were lost under high ammonia concentrations. These observations were also recapitulated in the livers of spf-ash mice, a model of constitutive hyperammonaemia due to deficiency in ornithine transcarbamylase enzyme. Moreover, c-Myc-mediated activation of autophagy plays a cytoprotective role in cells under ammonia stress conditions as confirmed through the pharmacological inhibition of c-Myc in Huh7 cells treated with low ammonia concentrations. In conclusion, the unravelled role of c-Myc in modulating ammonia induced autophagy opens new landscapes for the development of novel strategies for the treatment of hyperammonemia.

Association between the expression of epithelial-mesenchymal transition (EMT)-related markers and oncologic outcomes of colorectal cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) is a key step in the development of colorectal cancer (CRC) that confers metastatic capabilities to cancer cells. The present study aimed to assess the immunohistochemical (IHC) expression and impact of EMT markers, including E-cadherin, Vimentin, β-catenin, and SMAD4, on the oncologic outcomes of CRC.

METHODS

This was a retrospective review of 118 CRC patients. Tissue slides were retrieved from the slide archive and five tissue microarray construction blocks were constructed. IHC for E-cadherin, Vimentin, β-catenin, and SMAD4 was done. The main outcome was the association between abnormal marker expression and overall survival (OS), and disease-free survival (DFS).

RESULTS

Adenocarcinomas accounted for 71.2% of tumors, whereas 25.4% and 3.4% were mucinous and signet ring cell carcinomas. The rates of lymphovascular invasion and perineural invasion were 72.9% and 20.3%, respectively. There was a positive, significant correlation, and association between the four markers. Abnormal expression of E-cadherin was associated with significantly lower OS (p < 0.0001) and similar DFS (p = 0.06). Abnormal Vimentin expression was associated with a significantly higher rate of distant metastasis (p = 0.005) and significantly lower OS and DFS (p < 0.0001). Abnormal expression of β-catenin was associated with significantly lower OS (p < 0.0001) and similar DFS (p = 0.15). Abnormal expression of SMAD4 was associated with significantly lower OS and DFS (p < 0.0001). Abnormal expression of all four markers was associated with a higher disease recurrence, lower OS, and lower DFS.

CONCLUSION

Abnormal expression of each marker was associated with lower OS, whereas abnormal expression of Vimentin and SMAD4 only was associated with lower DFS.

Epithelial-Mesenchymal Transition: A Fundamental Cellular and Microenvironmental Process in Benign and Malignant Prostate Pathologies

Epithelial-mesenchymal transition (EMT) is a crucial and fundamental mechanism in many cellular processes, beginning with embryogenesis via tissue remodulation and wound healing, and plays a vital role in tumorigenesis and metastasis formation. EMT is a complex process that involves many transcription factors and genes that enable the tumor cell to leave the primary location, invade the basement membrane, and send metastasis to other tissues. Moreover, it may help the tumor avoid the immune system and establish radioresistance and chemoresistance. It may also change the normal microenvironment, thus promoting other key factors for tumor survival, such as hypoxia-induced factor-1 (HIF-1) and promoting neoangiogenesis. In this review, we will focus mainly on the role of EMT in benign prostate disease and especially in the process of establishment of malignant prostate tumors, their invasiveness, and aggressive behavior. We will discuss relevant study methods for EMT evaluation and possible clinical implications. We will also introduce clinical trials conducted according to CONSORT 2010 that try to harness EMT properties in the form of circulating tumor cells to predict aggressive patterns of prostate cancer. This review will provide the most up-to-date information to establish a keen understanding of the cellular and microenvironmental processes for developing novel treatment lines by modifying or blocking the pathways.

Comprehensive analysis of prognostic significance of cadherin (CDH) gene family in breast cancer

Breast cancer is one of the leading deaths in all kinds of malignancies; therefore, it is important for early detection. At the primary tumor site, tumor cells could take on mesenchymal properties, termed the epithelial-to-mesenchymal transition (EMT). This process is partly regulated by members of the cadherin (CDH) family of genes, and it is an essential step in the formation of metastases. There has been a lot of study of the roles of some of the CDH family genes in cancer; however, a holistic approach examining the roles of distinct CDH family genes in the development of breast cancer remains largely unexplored. In the present study, we used a bioinformatics approach to examine expression profiles of CDH family genes using the Oncomine, Gene Expression Profiling Interactive Analysis 2 (GEPIA2), cBioPortal, MetaCore, and Tumor IMmune Estimation Resource (TIMER) platforms. We revealed that CDH1/2/4/11/12/13 messenger (m)RNA levels are overexpressed in breast cancer cells compared to normal cells and were correlated with poor prognoses in breast cancer patients’ distant metastasis-free survival. An enrichment analysis showed that high expressions of CDH1/2/4/11/12/13 were significantly correlated with cell adhesion, the extracellular matrix remodeling process, the EMT, WNT/beta-catenin, and interleukin-mediated immune responses. Collectively, CDH1/2/4/11/12/13 are thought to be potential biomarkers for breast cancer progression and metastasis.

Thiol-Based Antioxidants and the Epithelial/Mesenchymal Transition in Cancer

Significance: The epithelial/mesenchymal transition (EMT) is commonly associated with tumor metastasis. Oxidative and nitrosative stress is maintained in cancer cells and is involved in the EMT. Cancer cells are endowed with high levels of enzymatic and nonenzymatic antioxidants, which counteract the effects of oxidative and nitrosative stress. Thiol-based antioxidant systems such as the thioredoxin/thioredoxin reductase (Trx/TrxR) and glutathione/glutaredoxin (GSH/Grx) are continually active in cancer cells, while the thioredoxin-interacting protein (Txnip), the negative regulator of the Trx/TrxR system, is downregulated. Recent Advances: Trx/TrxR and GSH/Grx systems play a major role in maintaining EMT signaling and cancer cell progression. Critical Issues: Enhanced stress conditions stimulated in cancer cells inhibit EMT signaling. The elevated expression levels of the Trx/TrxR and GSH/Grx systems in these cells provide the antioxidant protection necessary to guarantee the occurrence of the EMT. Future Directions: Elevation of the intracellular reactive oxygen species and nitric oxide concentrations in cancer cells has been viewed as a promising strategy for elimination of these cells. The development of inhibitors of GSH synthesis and of the Trx/TrxR system together with genetic-based strategies to enhance Txnip levels may provide the necessary means to achieve this goal. Antioxid. Redox Signal. 36, 1037-1050.

Epithelial-Mesenchymal Transition in Cancer: A Historical Overview

Epithelial-mesenchymal transitions (EMTs), the acquisition of mesenchymal features from epithelial cells, occur during some biological processes and are classified into three types: the first type occurs during embryonic development, the second type is associated with adult tissue regeneration, and the third type occurs in cancer progression. EMT occurring during embryonic development in gastrulation, renal development, and the origin and fate of the neural crest is a highly regulated process, while EMT occurring during tumor progression is highly deregulated. EMT allows the solid tumors to become more malignant, increasing their invasiveness and metastatic activity. Secondary tumors frequently maintain the typical histologic characteristics of the primary tumor. These histologic features connecting the secondary metastatic tumors to the primary is due to a process called mesenchymal-epithelial transition (MET). MET has been demonstrated in different mesenchymal tumors and is the expression of the reversibility of EMT. EMT modulation could constitute an approach to avoid metastasis. Some of the targeted small molecules utilized as antiproliferative agents have revealed to inhibit EMT initiation or maintenance because EMT is regulated through signaling pathways for which these molecules have been designed.

3D-microenvironments initiate TCF4 expression rescuing nuclear β-catenin activity in MCF-7 breast cancer cells

Mechanical cues sensed by tumor cells in their microenvironment can influence important mechanisms including adhesion, invasion and proliferation. However, a common mechanosensitive protein and/or pathway can be regulated in different ways among diverse types of tumors. Of particular interest are human breast epithelial cancers, which markedly exhibit a heterogeneous pattern of nuclear β-catenin localization, a protein known to be involved in both mechanotransduction and tumorigenesis. β-catenin can be aberrantly accumulated in the nucleus wherein it binds to and activates lymphoid enhancer factor/T cell factor (LEF/TCF) transcription factors. At present, little is known about how mechanical cues are integrated into breast cancer cells harboring impaired mechanisms of β-catenin's nuclear uptake and/or retention. This prompted us to investigate the influence of mechanical cues on MCF-7 human breast cancer cells which are known to fail in relocating β-catenin into the nucleus due to very low baseline levels of LEF/TCFs. Exploiting three-dimensional (3D) microscaffolds realized by two-photon lithography, we show that surrounding MCF-7 cells have not only a nuclear pool of β-catenin, but also rescue from their defective expression of TCF4 and boost invasiveness. Together with heightened amounts of vimentin, a β-catenin/TCF-target gene regulator of proliferation and invasiveness, such 3D-elicited changes indicate an epithelial-to-mesenchymal phenotypic switch of MCF-7 cells. This is also consistent with an increased in situ MCF-7 cell proliferation that can be abrogated by blocking β-catenin/TCF-transcription activity. Collectively, these data suggest that 3D microenvironments are per se sufficient to prime a TCF4-dependent rescuing of β-catenin nuclear activity in MCF-7 cells. The employed methodology could, therefore, provide a mechanism-based rationale to dissect further aspects of mechanotranscription in breast cancerogenesis, somewhat independent of β-catenin's nuclear accumulation. More importantly, by considering the heterogeneity of β-catenin signaling pathway in breast cancer patients, these data may open alternative avenues for personalized disease management and prevention. STATEMENT OF SIGNIFICANCE: Mechanical cues play a critical role in cancer pathogenesis. Little is known about their influence in breast cancer cells harboring impaired mechanisms of β-catenin's nuclear uptake and/or retention, involved in both mechanotransduction and tumorigenesis. We engineered 3D scaffold, by two-photon lithography, to study the influence of mechanical cues on MCF-7 cells which are known to fail in relocating β-catenin into the nucleus. We found that 3D microenvironments are per se sufficient to prime a TCF4-dependent rescuing of β-catenin nuclear activity that boost cell proliferation and invasiveness. Thus, let us suggest that our system could provide a mechanism-based rationale to further dissect key aspects of mechanotranscription in breast cancerogenesis and progression, somewhat independent of β-catenin's nuclear accumulation.

Expression of GLS1 in intrahepatic cholangiocarcinoma and its clinical significance

Kidney‑type glutaminase (GLS1) plays a significant role in tumor metabolism. Our recent studies demonstrated that GLS1 was aberrantly expressed in hepatocellular carcinoma (HCC) and facilitated tumor progression. However, the roles of GLS1 in intrahepatic cholangiocarcinoma (ICC) remain largely unknown. Thus, the aim of this study was to evaluate the expression and clinical significance of GLS1 in ICC. For this purpose, combined data from the Oncomine database with those of immunohistochemistry were used to determine the expression levels of GLS1 in cancerous and non‑cancerous tissues. Second, a wound‑healing assay and Transwell assay were used to observe the effects of the knockdown and overexpression of GLS1 on the invasion and migration of ICC cells. We examined the associations between the expression of GLS1 and epithelial‑mesenchymal transition (EMT)‑related markers by western blot analysis. Finally, we examined the associations between GLS1 levels and clinicopathological factors or patient prognosis. The results revealed that GLS1 was overexpressed in different digestive system tumors, including ICC, and that GLS1 expression in ICC tissue was higher than that in peritumoral tissue. The overexpression of GLS1 in RBE cells induced metastasis and invasion. Moreover, the EMT‑related markers, E‑cadherin and Vimentin, were regulated by GLS1 in ICC cells. By contrast, the knockdown of GLS1 expression in QBC939 cells yielded opposite results. Clinically, a high expression of GLS1 in ICC samples negatively correlated with E‑cadherin expression and positively correlated with Vimentin expression. GLS1 protein expression was associated with tumor differentiation (P=0.001) and lymphatic metastasis (P=0.029). Importantly, patients with a high GLS1 expression had a poorer overall survival (OS) and a shorter time to recurrence than patients with a low GLS1 expression. Multivariate analysis indicated that GLS1 expression was an independent prognostic indicator. On the whole, the findings of this study demonstrated that GLS1 is an independent prognostic biomarker of ICC. GLS1 facilitates ICC progression and may thus prove to be a therapeutic target in ICC.

LKB1 and YAP phosphorylation play important roles in Celastrol-induced β-catenin degradation in colorectal cancer

Wnt/β-catenin and Hippo pathways play essential roles in the tumorigenesis and development of colorectal cancer. We found that Celastrol, isolated from Tripterygium wilfordii plant, exerted a significant inhibitory effect on colorectal cancer cell growth in vitro and in vivo, and further unraveled the molecular mechanisms. Celastrol induced β-catenin degradation through phosphorylation of Yes-associated protein (YAP), a major downstream effector of Hippo pathway, and also Celastrol-induced β-catenin degradation was dependent on liver kinase B1 (LKB1). Celastrol increased the transcriptional activation of LKB1, partially through the heat shock factor 1 (HSF1). Moreover, LKB1 activated AMP-activated protein kinase α (AMPKα) and further phosphorylated YAP, which eventually promoted the degradation of β-catenin. In addition, LKB1 deficiency promoted colorectal cancer cell growth and attenuated the inhibitory effect of Celastrol on colorectal cancer growth both in vitro and in vivo. Taken together, Celastrol inhibited colorectal cancer cell growth by promoting β-catenin degradation via the HSF1–LKB1–AMPKα–YAP pathway. These results suggested that Celastrol may potentially serve as a future drug for colorectal cancer treatment.

USP22 drives colorectal cancer invasion and metastasis via epithelial-mesenchymal transition by activating AP4

Ubiquitin specific peptidase 22 (USP22), a putative cancer stem cell marker, is overexpressed in liver metastases of colorectal cancer (CRC). However, the mechanism by which USP22 promotes CRC metastasis remains largely unknown. Here, we report that USP22 and AP4 are simultaneously overexpressed during TGF-β1-induced CRC cell epithelial-mesenchymal transition (EMT). USP22 up-regulation enhances CRC cell migration and invasion and EMT-related marker and AP4 expression, but these effects are partly blocked by AP4 knockdown. In addition, USP22 binds to the promoter region of AP4 to activate its transcription. In vivo, elevated USP22 expression promotes CRC cell metastasis to the lungs in nude mice, as evidenced by the fact that CRC metastatic nodules stain deeply positive for USP22 and AP4. In human CRC tissues, the genes encoding USP22 and AP4 are overexpressed in metastatic liver lesions compared with primary cancer tissues, and their overexpression is significantly associated with poor CRC patient survival. These findings indicate that USP22 and AP4 may serve as prognostic markers for predicting the risk of developing distant metastases in CRC.

Transcription factor E2F1 promotes EMT by regulating ZEB2 in small cell lung cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) is an early event in tumour invasion and metastasis, and widespread and distant metastasis at early stages is the typical biological behaviour in small cell lung cancer (SCLC). Our previous reports showed that high expression of the transcription factor E2F1 was involved in the invasion and metastasis of SCLC, but the role of E2F1 in the process of EMT in SCLC is unknown.

METHODS

Immunohistochemistry was performed to evaluate the expressions of EMT related markers. Immunofluorescence was used to detect the expressions of cytoskeletal proteins and EMT related markers when E2F1 was silenced in SCLC cell lines. Adenovirus containing shRNA against E2F1 was used to knock down the E2F1 expression, and the dual luciferase reporter system was employed to clarify the regulatory relationship between E2F1 and ZEB2.

RESULTS

In this study, we observed the remodelling of cytoskeletal proteins when E2F1 was silenced in SCLC cell lines, indicating that E2F1 was involved in the EMT in SCLC. Depletion of E2F1 promoted the expression of epithelial markers (CDH1 and CTNNB1) and inhibited the expression of mesenchymal markers (VIM and CDH2) in SCLC cell lines, verifying that E2F1 promotes EMT occurrence. Next, the mechanism by which E2F1 promoted EMT was explored. Among the CDH1 related inhibitory transcriptional regulators ZEB1, ZEB2, SNAI1 and SNAI2, the expression of ZEB2 was the highest in SCLC tissue samples and was highly consistent with E2F1 expression. ChIP-seq data and dual luciferase reporter system analysis confirmed that E2F1 could regulate ZEB2 gene expression.

CONCLUSION

Our data supports that E2F1 promotes EMT by regulating ZEB2 gene expression in SCLC.

Estrogen and ERα enhanced β-catenin degradation and suppressed its downstream target genes to block the metastatic function of HA22T hepatocellular carcinoma cells via modulating GSK-3β and β-TrCP expression

In our previous experiments, we found β-catenin was highly expressed in the tumor area with high invasive ability and poor prognosis. In this study, we have examined the mechanism by which ERα regulates β-catenin expression as well as the metastasis ability of hepatocellular cancer HA22T cells. To identify whether the anticancer effect of estrogen and ERα is mediated through suppression of β-catenin expression, we co-transfected pCMV-β-catenin and ERα into HA22T cells, and determined the cell motility by wound healing, invasion, and migration assays. Results showed that estrogen and/or ERα inhibited β-catenin gene expression and repressed HA22T cell motility demonstrated that similar data was observed in cells expressing the ERα stable clone. Moreover, we examined the protein-protein interaction between ERα and β-catenin by immunostain, co-immunoprecipitation, and Western blotting. E2 enhanced the binding of ERα with β-catenin and then triggered β-catenin to bind with E3 ligase (βTrCP) to promote β-catenin degradation. Finally by employing systematic ChIP studies, we showed ERα can interact directly with the β-catenin promoter region following E2 treatment. All our results reveal that estrogen and ERα blocked metastatic function of HA22T cells by modulating GSK3β and βTrCP expression and further enhanced β-catenin degradation and suppressed its downstream target genes. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 519-529, 2017.

MicroRNAs Provide Feedback Regulation of Epithelial-Mesenchymal Transition Induced by Growth Factors

As regulators in gene expression, microRNAs take part in most biological processes including cell differentiation, apoptosis, cell cycle, and epithelial-to-mesenchymal transition (EMT). In order to evaluate their roles in EMT process, microRNA expression profile changes induced by EGF or TGF-β treatment on nasopharyngeal carcinoma cell HK-1 were analyzed, and miR-21, miR-148a, miR-505, and miR-1207-5p were found to be upregulated in growth factors-induced EMT process. miR-21 is already known as an oncogenic miRNA to promote metastasis, however, the exact functions of other three miRNAs in EMT are unclear. To our surprise, we found that miR-148a, miR-505, and miR-1207-5p can suppress EMT and metastasis phenotypes in HK-1 cells both in vitro and in vivo, which may relate to their inhibition on EMT and Wnt signaling molecules. MiRNAs confer robustness to biological processes by posttranscriptional repression of key transcriptional programs that are related to previous developmental stages or to alternative cell fates. Our findings indicate that miRNA feedback circuit is tuned to respond to growth factors-induced EMT, and we suggested a new negative feedback loop which may be an important element of the EMT process and confer biological robustness.

Selected case from the Arkadi M. Rywlin International Pathology Slide Club: carcinoma of the transverse colon in a young girl

We report a case of a 14-year-old female with primary adenocarcinoma of the transverse colon. She was hospitalized after presenting with abdominal pain and signs of intestinal obstruction. There was no health antecedent or family history of neoplasia. Physical examination revealed a distended abdomen. Tenderness was elicited to palpation of the right lower quadrant. Magnetic resonance imaging of the abdomen revealed obstructive signs, with a constricting lesion in the mid-transverse colon of probable neoplastic nature. Laparoscopic segmental resection of the colon was followed by standard right hemicolectomy. A circumferential mid-transverse tumor was diagnosed as primary colorectal carcinoma (CRC) of signet-ring cell type, AJCC stage IIIC, Dukes' C stage. On the basis of immunohistochemistry and clinical data, hereditary nonpolyposis and hamartomatous colorectal cancer syndromes were excluded. Involvement of either the p53, BRAF, or K-RAS genes was ruled out by immunohistochemistry profiling and genetic testing. The neoplasm was categorized as sporadic. The possibility of activation of the Wnt signaling pathway was suspected, because of a defective turnover of the β-catenin protein. Postoperatively, the patient was treated with both systemic and intra-abdominal adjuvant chemotherapy, including oxaliplatin. Between 18 and 24 months after diagnosis, intra-abdominal tumor recurrences were detected. The patient underwent bilateral oophorectomies for Krukenberg tumors and received salvage chemotherapy. Recently, additional recurrent metastatic retroperitoneal disease caused hydronephrosis. The retroperitoneal mass was debulked and a ureteric stent was placed. At the time of this writing, 43 months after diagnosis, the patient is receiving FOLFOX chemotherapy combined with panitumumab. CRC of childhood is exceedingly rare, generally develops in the setting of unrecognized genetic predisposing factors to cancer, presents with advanced disease, is high grade, and tends to have dismal prognosis.

Prognostic and diagnostic value of epithelial to mesenchymal transition markers in pulmonary neuroendocrine tumors

Background

Pulmonary neuroendocrine tumors (Pulmonary NETs) include a wide spectrum of tumors, from the low-grade typical carcinoid (TC) and the intermediate-grade atypical carcinoid (AC), to the high-grade large-cell neuroendocrine carcinoma (LCNEC) and the small-cell carcinoma (SCLC). Epithelial Mesenchymal Transition (EMT) is a process initially recognised during several critical stages of embryonic development, which has more recently been implicated in promoting carcinoma invasion and metastasis. The initial stage of the EMT process begins with the deregulation of adhesion molecules, such as E-cadherin, due to transcriptional repression carried out by factors such as Snail family members, Twist and Foxc2.

Methods

Immunohistochemistry for EMT markers and E-cadherin/ β-catenin complex in 134 patients with pulmonary NETs between 1990 – 2009. Analysis of potential associations with clinicopathological variables and survival.

Results

Pulmonary NETs of high malignant potential (LCNEC and SCLC) had reduced expression of the adhesion molecules and high level expression of transcriptional repressors (Snail1, Snail2, Twist and Foxc2). Snail high expression levels and the loss of E-cadherin/β-catenin complex integrity had the strongest negative effect on the five-year survival rates. E-cadherin/β-catenin complex integrity loss independently predicted lymph node involvement and helped in Atypical Carcinoid (AC) vs Typical Carcinoid (TC) differential diagnosis. Importantly, among the TC group, the loss of E-cadherin/β-catenin complex integrity identified patients with an adverse clinical course despite favourable clinicopathological features.

Conclusion

The immunohistochemical determination of E-cadherin/β-catenin complex integrity loss and EMT markers in the clinical setting might be a potential useful diagnostic and prognostic tool especially among the TC patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-855) contains supplementary material, which is available to authorized users.

Chibby functions in Xenopus ciliary assembly, embryonic development, and the regulation of gene expression

Wnt signaling and ciliogenesis are core features of embryonic development in a range of metazoans. Chibby (Cby), a basal-body associated protein, regulates β-catenin-mediated Wnt signaling in the mouse but not Drosophila. Here we present an analysis of Cby's embryonic expression and morphant phenotypes in Xenopus laevis. Cby RNA is supplied maternally, negatively regulated by Snail2 but not Twist1, preferentially expressed in the neuroectoderm, and regulates β-catenin-mediated gene expression. Reducing Cby levels reduced the density of multiciliated cells, the number of basal bodies per multiciliated cell, and the numbers of neural tube primary cilia; it also led to abnormal development of the neural crest, central nervous system, and pronephros, all defects that were rescued by a Cby-GFP chimera. Reduction of Cby led to an increase in Wnt8a and decreases in Gli2, Gli3, and Shh RNA levels. Many, but not all, morphant phenotypes were significantly reversed by the Wnt inhibitor SFRP2. These observations extend our understanding of Cby's role in mediating the network of interactions between ciliogenesis, signaling systems and tissue patterning.

Cyclin D1, E-cadherin and beta-catenin expression in FIGO Stage IA cervical squamous carcinoma: diagnostic value and evidence for epithelial-mesenchymal transition

AIMS

Immunohistochemistry is helpful in distinguishing cervical neoplastic lesions from their histological mimics, but has contributed less towards the sometimes problematic distinction of in-situ and superficially invasive tumours. Epithelial-mesenchymal transition (EMT) may be a mechanism of invasion in cervical neoplasia and expression of EMT-associated proteins could prove useful in this diagnostic setting.

METHODS AND RESULTS

Immunohistochemical expression of cyclin D1, E-cadherin and beta-catenin was assessed in 22 biopsy specimens from FIGO Stage IA cervical squamous carcinomas, all of which also included foci of cervical intraepithelial neoplasia (CIN) 3, nine biopsies of CIN 3 adjacent to carcinoma, and 10 cases of CIN 3 only. Most invasive tumour cells expressed cyclin D1 and showed a reduction in E-cadherin and beta-catenin staining. Nuclear beta-catenin expression was not observed. Cyclin D1 staining was reduced or showed altered distribution in most cases of CIN 3, while adhesion protein expression generally was preserved. However, altered protein expression similar to that of invasion was seen in some CIN lesions.

CONCLUSIONS

Most superficially invasive cervical squamous carcinomas show immunophenotypical changes consistent with EMT. These alterations, particularly cyclin D1 expression, may be useful diagnostically. Similar changes in CIN 3 lesions may indicate the acquisition of increased invasive potential.

Interplay between neural-cadherin and vascular endothelial-cadherin in breast cancer progression

Introduction

Deregulation of cadherin expression, in particular the loss of epithelial (E)-cadherin and gain of neural (N)-cadherin, has been implicated in carcinoma progression. We previously showed that endothelial cell-specific vascular endothelial (VE)-cadherin can be expressed aberrantly on tumor cells both in human breast cancer and in experimental mouse mammary carcinoma. Functional analyses revealed that VE-cadherin promotes tumor cell proliferation and invasion by stimulating transforming growth factor (TGF)-β signaling. Here, we investigate the functional interplay between N-cadherin and VE-cadherin in breast cancer.

Methods

The expression of N-cadherin and VE-cadherin was evaluated by immunohistochemistry in a tissue microarray with 84 invasive human breast carcinomas. VE-cadherin and N-cadherin expression in mouse mammary carcinoma cells was manipulated by RNA interference or overexpression, and cells were then analyzed by immunofluorescence, reverse transcriptase-polymerase chain reaction, and western blot. Experimental tumors were generated by transplantation of the modified mouse mammary carcinoma cells into immunocompetent mice. Tumor growth was monitored, and tumor tissue was subjected to histological analysis.

Results

VE-cadherin and N-cadherin were largely co-expressed in invasive human breast cancers. Silencing of N-cadherin in mouse mammary carcinoma cells led to decreased VE-cadherin expression and induced changes indicative of mesenchymal-epithelial transition, as indicated by re-induction of E-cadherin, localization of β-catenin at the cell membrane, decreased expression of vimentin and SIP1, and gain of epithelial morphology. Suppression of N-cadherin expression also inhibited tumor growth in vivo, even when VE-cadherin expression was forced.

Conclusions

Our results highlight the critical role of N-cadherin in breast cancer progression and show that N-cadherin is involved in maintaining the malignant tumor cell phenotype. The presence of N-cadherin prevents the re-expression of E-cadherin and localization of β-catenin at the plasma membrane of mesenchymal mammary carcinoma cells. N-cadherin is also required to maintain the expression of VE-cadherin in malignant tumor cells but not vice versa. Thus, N-cadherin acts in concert with VE-cadherin to promote tumor growth.

Transcriptional activation of the beta-catenin gene at the invasion front of colorectal liver metastases

beta-Catenin is a pivotal molecule of the Wnt-signalling pathway, involved in regulation of developmental and oncogenic processes as well as in intercellular adhesion. So far, beta-catenin has been thought to be regulated mainly at the protein level. Here, we provide evidence for a transcriptional mechanism of beta-catenin regulation at the invasion front of colorectal liver metastases. In a nude mouse/LS174T cell xenograft model of colorectal liver metastases, we observed beta-catenin up-regulation at the mRNA and protein levels and a 13.7-fold increase of beta-catenin promoter activity in the cancer cells of the invasion front. In addition, the promoter activity was five-fold higher in the interior of the tumour than in cells growing in cell culture. In vitro studies revealed binding of TCF-4 to the beta-catenin promoter and reduced promoter activity by over-expression of dominant negative TCF-4, or beta-catenin knock-down and increased activity by beta-catenin over-expression, indicating that beta-catenin acts as co-transcription factor of its own promoter. In 55% (7/13) of clinical specimens, beta-catenin mRNA was markedly elevated in the cancer cells of the invasion front. Elevation of mRNA was paralleled by increased nuclear and cytoplasmic beta-catenin protein concentrations. These data indicate that transcriptional regulation contributes to the dynamic changes of beta-catenin levels upon the confrontation of tumour cells with the host microenvironment.

Staurosporine augments EGF-mediated EMT in PMC42-LA cells through actin depolymerisation, focal contact size reduction and Snail1 induction - a model for cross-modulation

BACKGROUND

A feature of epithelial to mesenchymal transition (EMT) relevant to tumour dissemination is the reorganization of actin cytoskeleton/focal contacts, influencing cellular ECM adherence and motility. This is coupled with the transcriptional repression of E-cadherin, often mediated by Snail1, Snail2 and Zeb1/deltaEF1. These genes, overexpressed in breast carcinomas, are known targets of growth factor-initiated pathways, however it is less clear how alterations in ECM attachment cross-modulate to regulate these pathways. EGF induces EMT in the breast cancer cell line PMC42-LA and the kinase inhibitor staurosporine (ST) induces EMT in embryonic neural epithelial cells, with F-actin de-bundling and disruption of cell-cell adhesion, via inhibition of aPKC.

METHODS

PMC42-LA cells were treated for 72 h with 10 ng/ml EGF, 40 nM ST, or both, and assessed for expression of E-cadherin repressor genes (Snail1, Snail2, Zeb1/deltaEF1) and EMT-related genes by QRT-PCR, multiplex tandem PCR (MT-PCR) and immunofluorescence +/- cycloheximide. Actin and focal contacts (paxillin) were visualized by confocal microscopy. A public database of human breast cancers was assessed for expression of Snail1 and Snail2 in relation to outcome.

RESULTS

When PMC42-LA were treated with EGF, Snail2 was the principal E-cadherin repressor induced. With ST or ST+EGF this shifted to Snail1, with more extreme EMT and Zeb1/deltaEF1 induction seen with ST+EGF. ST reduced stress fibres and focal contact size rapidly and independently of gene transcription. Gene expression analysis by MT-PCR indicated that ST repressed many genes which were induced by EGF (EGFR, CAV1, CTGF, CYR61, CD44, S100A4) and induced genes which alter the actin cytoskeleton (NLF1, NLF2, EPHB4). Examination of the public database of breast cancers revealed tumours exhibiting higher Snail1 expression have an increased risk of disease-recurrence. This was not seen for Snail2, and Zeb1/deltaEF1 showed a reverse correlation with lower expression values being predictive of increased risk.

CONCLUSION

ST in combination with EGF directed a greater EMT via actin depolymerisation and focal contact size reduction, resulting in a loosening of cell-ECM attachment along with Snail1-Zeb1/deltaEF1 induction. This appeared fundamentally different to the EGF-induced EMT, highlighting the multiple pathways which can regulate EMT. Our findings add support for a functional role for Snail1 in invasive breast cancer.

The hedgehog pathway as a therapeutic target for treatment of breast cancer

The Hedgehog (Hh) signaling pathway plays a key role in a variety of processes, such as embryogenesis and maintenance of adult tissue homeostasis. It is also becoming increasingly clear that this pathway can have a crucial role in tumorigenesis. Most recently, the Hh signaling pathway has been implicated in the development and maintenance of breast cancer. Here we review Hh signaling, advances in small molecule and antibody-based inhibitors targeting the Hh pathway, and dysregulation of the Hh signaling pathway in breast cancer.

Epithelial--mesenchymal and mesenchymal--epithelial transitions in carcinoma progression

Like a set of bookends, cellular, molecular, and genetic changes of the beginnings of life mirror those of one of the most common cause of death--metastatic cancer. Epithelial to mesenchymal transition (EMT) is an important change in cell phenotype which allows the escape of epithelial cells from the structural constraints imposed by tissue architecture, and was first recognized by Elizabeth Hay in the early to mid 1980's to be a central process in early embryonic morphogenesis. Reversals of these changes, termed mesenchymal to epithelial transitions (METs), also occur and are important in tissue construction in normal development. Over the last decade, evidence has mounted for EMT as the means through which solid tissue epithelial cancers invade and metastasize. However, demonstrating this potentially rapid and transient process in vivo has proven difficult and data connecting the relevance of this process to tumor progression is still somewhat limited and controversial. Evidence for an important role of MET in the development of clinically overt metastases is starting to accumulate, and model systems have been developed. This review details recent advances in the knowledge of EMT as it occurs in breast development and carcinoma and prostate cancer progression, and highlights the role that MET plays in cancer metastasis. Finally, perspectives from a clinical and translational viewpoint are discussed.

Molecular plasticity of beta-catenin: new insights from single-molecule measurements and MD simulation

The multifunctional protein, beta-catenin, has essential roles in cell adhesion and, through the Wnt signaling pathway, in controlling cell differentiation, development, and generation of cancer. Could distinct molecular forms of beta-catenin underlie these two functions? Our single-molecule force spectroscopy of armadillo beta-catenin, with molecular dynamics (MD) simulation, suggests a model in which the cell generates various forms of beta-catenin, in equilibrium. We find beta-catenin and the transcriptional factor Tcf4 form two complexes with different affinities. Specific cellular response is achieved by the ligand binding to a particular matching preexisting conformer. Our MD simulation indicates that complexes derive from two conformers of the core region of the protein, whose preexisting molecular forms could arise from small variations in flexible regions of the beta-catenin main binding site. This mechanism for the generation of the various forms offers a route to tailoring future therapeutic strategies.

Bcr-Abl stabilizes beta-catenin in chronic myeloid leukemia through its tyrosine phosphorylation

Self-renewal of Bcr-Abl(+) chronic myeloid leukemia (CML) cells is sustained by a nuclear activated serine/threonine-(S/T) unphosphorylated beta-catenin. Although beta-catenin can be tyrosine (Y)-phosphorylated, the occurrence and biological relevance of this covalent modification in Bcr-Abl-associated leukemogenesis is unknown. Here we show that Bcr-Abl levels control the degree of beta-catenin protein stabilization by affecting its Y/S/T-phospho content in CML cells. Bcr-Abl physically interacts with beta-catenin, and its oncogenic tyrosine kinase activity is required to phosphorylate beta-catenin at Y86 and Y654 residues. This Y-phospho beta-catenin binds to the TCF4 transcription factor, thus representing a transcriptionally active pool. Imatinib, a Bcr-Abl antagonist, impairs the beta-catenin/TCF-related transcription causing a rapid cytosolic retention of Y-unphosphorylated beta-catenin, which presents an increased binding affinity for the Axin/GSK3beta complex. Although Bcr-Abl does not affect GSK3beta autophosphorylation, it prevents, through its effect on beta-catenin Y phosphorylation, Axin/GSK3beta binding to beta-catenin and its subsequent S/T phosphorylation. Silencing of beta-catenin by small interfering RNA inhibited proliferation and clonogenicity of Bcr-Abl(+) CML cells, in synergism with Imatinib. These findings indicate the Bcr-Abl triggered Y phosphorylation of beta-catenin as a new mechanism responsible for its protein stabilization and nuclear signalling activation in CML.

Sarcomatoid carcinomas of the lung—are these histogenetically heterogeneous tumors?

Sarcomatoid carcinomas (SC) of the lung are a heterogeneous group of nonsmall cell lung carcinomas (NSCLC) containing a sarcoma or sarcoma-like component. SC may represent an epithelial neoplasm undergoing divergent tissue differentiation originating from a single clone. Epithelial-mesenchymal transition (EMT) best describes the origin of the spindle and giant cells. We aimed to define chromosomal aberrations within the subgroups of SC and if EMT does play a role in SC. Twenty-two SC were investigated by chromosomal comparative genomic hybridization (CGH). Immunohistochemical staining was performed with antibodies for E-cadherin, Vimentin, c-Fos, c-Jun, Snail, TGFbeta1, Notch1, beta-catenin, Glycogen synthase kinase 3beta (GSK3beta), and Fascin. Gains occurred more frequently than losses (70.5 vs 29.5%). The shortest regions of overlap were gains on chromosomes 8q and 7 followed by 1q, 3q, and 19, supporting the common origin of the different subtypes of SC. The immunohistochemical staining suggests that the sarcomatoid components of SC might have undergone EMT, not triggered by the signaling pathways Notch1, Snail, and TGFbeta1, but probably initiated by an upregulation of c-Jun and a consecutive overexpression of Vimentin and Fascin. The Wnt-pathway was not deregulated because combined membrane and cytoplasmic reactivity for beta-catenin and GSK3beta was observed.

An immunohistochemical study of morules in endometrioid lesions of the female genital tract: CD10 is a characteristic marker of morular metaplasia

PURPOSE

To analyze immunohistochemically morules in endometrioid lesions to show that CD10 is a sensitive marker for morular metaplasia.

EXPERIMENTAL DESIGN

Immunohistochemical analysis of 53 instances of morular metaplasia comprising 1 cyclic endometrium and 52 endometrioid lesions associated with focal glandular complexity corresponding to 9 polyps, 4 atypical polypoid adenomyomas, 24 complex endometrial hyperplasias (18 with and 6 without atypia), 12 grade 1 endometrioid adenocarcinomas in early clinical stages of both uterus and ovary, and three ovarian adenofibromas. Immunohistochemistry in paraffin sections was done for CD10, beta-catenin, estrogen and progesterone receptors, and cytokeratins 5-6, 7, 8, 13, 18, 19, 20, and 34beta-E12.

RESULTS

Morules were negative for estrogen and progesterone receptors and had beta-catenin-positive nuclei. Cytokeratins 8, 18, 19 were positive; cytokeratins 7 and 20 were negative; and cytokeratins 5-6, 13, and 34beta-E12 were weakly positive. All cases revealed strongly positive membranous CD10 staining in morules, which was absent in glands. CD10 positivity allowed easy identification of morules at low power in various types of surgical specimens and in curettings. CD10 also highlighted early morular metaplasia in glandular epithelium. In cases associated with squamous, keratinizing metaplasia, CD10 discriminated between both types of metaplasia.

CONCLUSIONS

CD10 staining represents a useful marker of morules in endometrioid neoplasms of the female genital tract, permitting identification of lesions usually associated with an attenuated malignancy. Considering the immunohistochemical and genetic similarities of morules in tumors of different organs, it is likely that this marker may be also useful to diagnose morular metaplasia in similar neoplasms of extragenital locations.

Developmental functions of the P120-catenin sub-family

For more than a decade, cell, developmental and cancer investigators have brought about a wide interest in the biology of catenin proteins, an attraction being their varied functions within differing cellular compartments. While the diversity of catenin localizations and roles has been intriguing, it has also posed a challenge to the clear interpretation of loss- or gain-of-function developmental phenotypes. The most deeply studied member of the larger catenin family is beta-catenin, whose contributions span areas including cell adhesion and intracellular signaling/ transcriptional control. More recently, attention has been directed towards p120-catenin, which in conjunction with the p120-catenin sub-family members ARVCF- and delta-catenins, are the subjects of this review. Although the requirement for vertebrate versus invertebrate p120-catenin are at variance, vertebrate p120-catenin sub-family members may each inter-link cadherin, cytoskeletal and gene regulatory functions in embryogenesis and disease.

Claudin 1 differentiates endometrioid and serous papillary endometrial adenocarcinoma

OBJECTIVE

The expression of claudins, the main tight junction proteins involved in cell adhesion and carcinogenesis, was studied in endometrioid (type I) and seropapillary (type II) endometrial adenocarcinoma. The characteristics and possible diagnostic potential of claudin expression pattern were investigated in the two cancer types having different prognosis.

METHODS

Protein and mRNA expression of claudins was evaluated in 17 endometrioid carcinomas and 15 seropapillary adenocarcinomas by immunohistochemistry and real-time PCR in comparison with 38 cases of hyperplasia, normal proliferative and secretory endometrium samples. Further, protein expressions used in diagnostics (estrogen and progesterone receptors, p53, PCNA and beta-catenin) were also studied.

RESULTS

In endometrioid carcinoma and hyperplasia low claudin 1 and high claudin 2 protein contents, whereas in seropapillary adenocarcinoma high claudin 1 and low claudin 2 levels were detected. Intense protein expression was noted for claudins 3, 4, 5, and 7, without significantly different patterns in carcinoma, hyperplasia, secretory, and proliferative endometrium. Real-time PCR results confirmed differences in claudin 1 but not claudin 2 mRNA expression, whereas some minor discrepancies were observed in comparison with immunohistochemistry patterns.

CONCLUSION

The two types of endometrial adenocarcinomas were well distinguished by claudins 1 and 2 by immunohistochemistry, claudins 3, 4, and 7, however, did not prove useful in distinguishing the two entities. The similar claudin pattern seen in hyperplasia and endometrioid carcinoma and the differences regarding seropapillary adenocarcinoma support the dualistic model of endometrial carcinogenesis. The claudin pattern of the two tumor types might reflect a different cellular or pathogenetic pathway as well as a different cell adhesion behavior explaining the invasive properties.

Relevance of the stroma and epithelial-mesenchymal transition (EMT) for the rheumatic diseases

Epithelial-mesenchymal transition (EMT) is a term applied to the process whereby cells undergo a switch from an epithelial phenotype with tight junctions, lateral, apical, and basal membranes, and lack of mobility into mesenchymal cells that have loose interactions with other cells, are non-polarized, motile and produce an extracellular matrix. The importance of this process was initially recognized from a very early step in embryology, but more recently as a potential mechanism for the progression and spread of epithelial cancers. As the sequence of morphological changes has become understood in molecular terms, diseases characterized by alterations in stromal elements and fibrosis are being considered as examples of EMT. This review will focus on the pathogenetic features of immune-mediated renal disease, systemic sclerosis and rheumatoid arthritis that could be explained by EMT.

Parathyroid Hormone-related Protein Regulates Tumor-relevant Genes in Breast Cancer Cells

The effect of endogenous parathyroid hormone-related protein (PTHrP) on gene expression in breast cancer cells was studied. We suppressed PTHrP expression in MDA-MB-231 cells by RNA interference and analyzed changes in gene expression by microarray analysis. More than 200 genes showed altered expression in response to a PTHrP-specific small interfering (si) RNA (siPTHrP). Cell cycle-regulating gene CDC2 and genes (CDC25B and Tome-1) that control CDC2 activity showed increased expression in the presence of siPTHrP. CDC2 activity was also found to be higher in siPTHrP-treated cells. Studies with PTHrP peptides 1-34 and 67-86, forskolin, and a PTH1 receptor (PTH1R)-specific siRNA showed that PTHrP regulates CDC2 and CDC25B, at least in part, via PTH1R in a cAMP-independent manner. Other siPTHrP-responsive genes included integrin alpha6 (ITGA6), KISS-1, and PAI-1. When combined, siRNAs against ITGA6, PAI-1, and KISS-1 could mimic the negative effect of siPTHrP on migration, whereas siKISS-1 and siPTHrP similarly reduced the proliferative activity of the cells. Comparative expression analyses with 50 primary breast carcinomas revealed that the RNA level of ITGA6 correlates with that of PTHrP, and higher CDC2 and CDC25B values are found at low PTHrP expression. Our data suggest that PTHrP has a profound effect on gene expression in breast cancer cells and, as a consequence, contributes to the regulation of important cellular activities, such as migration and proliferation.

SKI-606 decreases growth and motility of colorectal cancer cells by preventing pp60(c-Src)-dependent tyrosine phosphorylation of beta-catenin and its nuclear signaling

Inhibition of deregulated protein tyrosine kinases represents an attractive strategy for controlling cancer growth. However, target specificity is an essential aim of this strategy. In this report, pp60(c-Src) kinase and beta-catenin were found physically associated and constitutively activated on tyrosine residues in human colorectal cancer cells. The use of specific small-interfering RNAs (siRNA) validated pp60(c-Src) as the major kinase responsible for beta-catenin tyrosine phosphorylation in colorectal cancer. Src-dependent activation of beta-catenin was prevented by SKI-606, a novel Src family kinase inhibitor, which also abrogated beta-catenin nuclear function by impairing its binding to the TCF4 transcription factor and its trans-activating ability in colorectal cancer cells. These effects were seemingly specific, as cyclin D1, a crucial beta-catenin/TCF4 target gene, was also down-regulated by SKI-606 in a dose-dependent manner accounting, at least in part, for the reduced growth (IC50, 1.5-2.4 micromol/L) and clonogenic potential of colorectal cancer cells. Protein levels of beta-catenin remained substantially unchanged by SKI-606, which promoted instead a cytosolic/membranous retention of beta-catenin as judged by immunoblotting analysis of cytosolic/nuclear extracts and cell immunofluorescence staining. The SKI-606-mediated relocalization of beta-catenin increased its binding affinity to E-cadherin and adhesion of colorectal cancer cells, with ensuing reduced motility in a wound healing assay. Interestingly, the siRNA-driven knockdown of beta-catenin removed the effect of SKI-606 on cell-to-cell adhesion, which was associated with prolonged stability of E-cadherin protein in a pulse-chase experiment. Thus, our results show that SKI-606 operates a switch between the transcriptional and adhesive function of beta-catenin by inhibiting its pp60(c-Src)-dependent tyrosine phosphorylation; this could constitute a new therapeutic target in colorectal cancer.

Chromosomal protein HMGN1 modulates the expression of N-cadherin

HMGN1 is a nuclear protein that binds to nucleosomes and alters the accessibility of regulatory factors to their chromatin targets. To elucidate its biological function and identify specific HMGN1 target genes, we generated Hmgn1-/- mice. DNA microarray analysis of Hmgn1+/+ and Hmgn1-/- embryonic fibroblasts identified N-cadherin as a potential HMGN1 gene target. RT-PCR and western blot analysis confirmed a linkage between HMGN1 expression and N-cadherin levels. In both transformed and primary mouse embryonic fibroblasts (MEFs), HMGN1 acted as negative regulator of N-cadherin expression. Likewise, the N-cadherin levels in early embryos of Hmgn1-/- mice were higher than those of their Hmgn1+/+ littermates. Loss of HMGN1 increased the adhesiveness, motility and aggregation potential of Hmgn1-/- MEFs, a phenotype consistent with increased levels of N-cadherin protein. Re-expression of wild-type HMGN1, but not of the mutant HMGN1 protein that does not bind to chromatin, in Hmgn1-/- MEFs, decreased the levels of N-cadherin and restored the Hmgn1+/+ phenotype. These studies demonstrate a role for HMGN1 in the regulation of specific gene expression. We suggest that in MEFs, and during early mouse development, the interaction of HMGN1 with chromatin down-regulates the expression of N-cadherin.