P120-catenin isoforms 1A and 3A differently affect invasion and proliferation of lung cancer cells

Delta-catenin is required for cell proliferation in virus-positive Merkel cell carcinoma cell lines but not in human fibroblasts

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine skin cancer often driven by the integration of Merkel cell polyomavirus (MCPyV) into the host genome and the persistent expression of its viral oncoproteins, small tumor (ST) antigen, and truncated large tumor (t-LT) antigen. While human fibroblasts support MCPyV replication, the cell of origin for MCC remains unknown. We hypothesized that MCPyV initially replicates in fibroblasts but, in rare cases, infects Merkel cell progenitors, contributing to MCC development. Using TurboID mass spectrometry, we identified δ-catenin as a novel ST interactor in fibroblasts. However, while ST binds δ-catenin in fibroblasts, this interaction is absent in virus-positive (VP)-MCC cell lines. Despite this, δ-catenin is essential for VP-MCC, but not for fibroblast cell proliferation. We found that fibroblasts predominantly express δ-catenin isoform 1, whereas VP-MCC cells mainly express isoform 3. Overexpression of isoform 1 in VP-MCC failed to restore ST binding. δ-Catenin promotes VP-MCC proliferation by regulating cell cycle gene expression through its interaction with Kaiso, a transcriptional repressor. Additionally, we found that lysine-specific histone demethylase 1 (LSD1, also known as KDM1A) regulates δ-catenin isoform 3 expression by modulating ESRP1, a δ-catenin splicing factor. Our findings reveal novel host factors involved in MCPyV infection and MCC tumorigenesis, suggesting that the host cell supporting viral replication and the MCC cell of origin may be distinct cell types.IMPORTANCEMerkel cell polyomavirus (MCPyV), the only known human oncogenic polyomavirus, is the primary cause of Merkel cell carcinoma (MCC), a rare and aggressive type of skin cancer. MCC is driven by two viral proteins: small T (ST) and large T (LT). While the virus can replicate in skin fibroblasts, it is still unknown which type of skin cell becomes cancerous. We found that ST binds to a host protein, δ-catenin in fibroblasts, potentially playing a role in the virus lifecycle, but this interaction is missing in the cancer cells. Our study provides evidence that the cells in which the virus replicates and causes cancer are different.

Delta-catenin is required for cell proliferation in virus positive Merkel cell carcinoma cell lines but not in human fibroblasts

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine skin cancer often driven by the integration of Merkel cell polyomavirus (MCPyV) into the host genome and the persistent expression of its viral oncoproteins, small tumor (ST) antigen and truncated large tumor (t-LT) antigen. While human fibroblasts support MCPyV replication, the cell of origin for MCC remains unknown. We hypothesized that MCPyV initially replicates in fibroblasts but, in rare cases, infects Merkel cell progenitors, contributing to MCC development. Using TurboID mass spectrometry, we identified δ-catenin as a novel ST interactor in fibroblasts. However, while ST binds δ-catenin in fibroblasts, this interaction is absent in virus-positive (VP)-MCC cell lines. Despite this, δ-catenin is essential for VP-MCC, but not for fibroblast, cell proliferation. We found that fibroblasts predominantly express δ-catenin isoform 1, whereas VP-MCC cells mainly express isoform 3. Overexpression of isoform 1 in VP-MCC failed to restore ST binding. δ-catenin promotes VP-MCC proliferation by regulating cell cycle gene expression through its interaction with Kaiso, a transcriptional repressor. Additionally, we found that LSD1 (KDM1A) regulates δ-catenin isoform 3 expression by modulating ESRP1, a δ-catenin splicing factor. Our findings reveal novel host factors involved in MCPyV infection and MCC tumorigenesis, suggesting that the host cell supporting viral replication and the MCC cell of origin may be distinct cell types.

The role of alternative splicing in lung cancer

Aberrant alternative splicing (AS) events are frequently observed in lung cancer, which can be attributed to aberrant gene AS, alterations in splicing regulatory factors, or changes in splicing regulatory mechanisms. Consequently, the dysregulation of alternative RNA splicing is the fundamental cause of lung cancer. In this review, we have summarized the pivotal role of AS in the development, progression, invasion, metastasis, angiogenesis, and drug resistance of lung cancer. Ultimately, this review emphasizes the potential of AS as biomarkers in lung cancer prognosis and diagnosis, and introduces some applications of AS isoform in the treatment of lung cancer. The comprehension of the AS may provide a glimmer of hope for the eradication of lung cancer.

PTP-PEST Regulated Membranous/Cytoplasmic Translocation of p120ctn in the Lung Cancer Resistance to Tyrosine Kinase Inhibitor

Our previous studies indicate that resistance induction using first-generation tyrosine kinase inhibitors (TKIs) in lung cancer is accompanied with p120-catenin (p120ctn) cytoplasmic translocation from the membrane. However, the molecular mechanism underlying p120ctn intracytoplasmic translocation has not yet been reported. We performed immunohistochemistry to detect the correlation of p120ctn distribution with protein tyrosine phosphatase non-receptor type 12 (PTP-PEST) and p120ctn Y335 phosphorylation levels in non-small cell lung cancer (NSCLC) patients. After resistance induction using first-generation TKIs in lung cancer cells, Western blotting and substrate trapping were used to assess PTP-PEST expression and its influence on p120ctn Y335 phosphorylation, as well as the role of p120ctn Y335 phosphorylation on the association of p120ctn with E-cadherin and p120ctn membrane/cytoplasm translocation. In 197 samples collected from NSCLC patients, cytoplasmic p120ctn and enhanced p120ctn Y335 phosphorylation were associated with decreased PTP-PEST. After resistance induction using gefitinib, decreased PTP-PEST expression was accompanied by enhanced phosphorylation of p120ctn Y335 and p120ctn translocated to the cytoplasm. In gefitinib-resistant cells, PTP-PEST overexpression restrained p120ctn Y335 phosphorylation and restored membrane p120ctn expression. PTP-PEST enhanced the interaction of p120ctn with E-cadherin and elevated p120ctn membrane expression. However, increased p120ctn-Y335F mutant had no effect on p120ctn interaction with E-cadherin and membrane/cytoplasm translocation compared with the control group. In conclusion, resistance to first-generation TKIs inhibited PTP-PEST expression, which promoted p120ctn-Y335 phosphorylation and reduced the interaction of p120ctn with E-cadherin, resulting in p120ctn cytoplasmic translocation.

Overexpression of PTPRZ1 Regulates p120/ β -Catenin Phosphorylation to Promote Carcinogenesis of Oral Submucous Fibrosis

Background

Oral submucous fibrosis (OSF) is a potentially malignant disease of the oral cavity. New molecular predictors are needed to identify the high risk of malignant transformation in potentially malignant oral lesions. Our purpose is to explore PTPRZ1 and p120/β-catenin pathogenesis in the carcinogenesis of OSF to identify novel drug targets.

Methods

The expression of PTPRZ1, p120, and β-catenin in clinical tissues was detected. Then, PTPRZ1, p120, β-catenin, RhoA, Rac1, CDC42, cyclin D1, and c-myc expressions were detected by qRT-PCR and western blot. CCK-8 was applied to measure hOMF cells viability. Wound healing and transwell assay were applied to measure cell migration and invasion. Western blot and IF detected the distribution of p-p120 and p-β-catenin. Tumor formation experiment explored PTPRZ1 effects on OSF.

Results

PTPRZ1, p120, and β-catenin were abnormally expressed in cancer tissues. PTPRZ1 regulated the phosphorylation of p120/β-catenin. Western blot and IF showed that in the oe-NC group, p-p120 and p-β-catenin were expressed in the cell membrane. p-p120 and p-β-catenin were expressed in the cytoplasm and nucleus of the oe-PTPRZ1 group. In vitro experimental results revealed overexpression of PTPRZ1 and β-catenin, and silencing of p120 promoted cell proliferation, migration, and invasion. The tumor volume and weight in the sh-PTPRZ1 group were significantly reduced. IHC revealed the positive rate of PTPRZ1 was also low.

Conclusions

Overexpression of PTPRZ1 regulated the phosphorylation of p120/β-catenin to promote OSF malignancy.

Cytoplasmic P120ctn Promotes Gefitinib Resistance in Lung Cancer Cells by Activating PAK1 and ERK Pathway

Our previous studies indicated that cytoplasmic p120ctn mediated epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) resistance in lung cancer. In the present study, we aim to further explore the underlying molecular mechanisms. Immunohistochemistry detected PAK1, Cdc42, and Rac1 expression in lung cancer with cytoplasmic p120ctn. Immunoblotting, protein activity analysis, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide evaluated p120ctn location, PAK1, Cdc42/Rac1, and extracellular signal-regulated kinase (ERK) activity in response to TKI treatment in HCC827 and PC9 cell lines, as well as the cell sensitivity to Gefitinib. Most non-small cell lung cancer patients with cytoplasmic p120ctn showed enhanced PAK1 and Cdc42/Rac1. When Gefitinib resistance was induced, cytoplasmic p120ctn is accompanied with increasing PAK1 and Cdc42/Rac1. Cytoplasmic p120ctn activated ERK via PAK1, while PAK1 downregulation attenuated ERK activation by cytoplasmic p120ctn. After Cdc42/Rac1 inhibition, cytoplasmic p120ctn could not activate PAK1. Cytoplasmic p120ctn activates PAK1 via Cdc42/Rac1 activation, constitutively activates ERK in the EGFR downstream signaling, and promotes EGFR-TKI resistance in lung cancer cells. The current study will aid to screen the subpopulation patients who would benefit from therapy with first-generation EGFR-TKIs.

Relationship between apical junction proteins, gene expression and cancer

The apical junctional complex (AJC) is a cell-cell adhesion system present at the upper portion of the lateral membrane of epithelial cells integrated by the tight junction (TJ) and the adherens junction (AJ). This complex is crucial to initiate and stabilize cell-cell adhesion, to regulate the paracellular transit of ions and molecules and to maintain cell polarity. Moreover, we now consider the AJC as a hub of signal transduction that regulates cell-cell adhesion, gene transcription and cell proliferation and differentiation. The molecular components of the AJC are multiple and diverse and depending on the cellular context some of the proteins in this complex act as tumor suppressors or as promoters of cell transformation, migration and metastasis outgrowth. Here, we describe these new roles played by TJ and AJ proteins and their potential use in cancer diagnostics and as targets for therapeutic intervention.

The Expression Pattern of p120-Catenin is Associated With Acquired Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer

BACKGROUND

Previous research connects p120-catenin (p120ctn) with epidermal growth factor receptor (EGFR) signaling pathways, which presents a potential role for p120ctn in EGFR tyrosine kinase inhibitor (EGFR-TKIs) resistance. However, a direct correlation between the expression pattern of p120ctn in solid tumors and the therapeutic effect of EGFR-TKIs has not yet been demonstrated.

METHODS AND RESULTS

In this study, the expression pattern of p120ctn was examined in patients with the EGFR gene mutation in lung adenocarcinoma, and p120ctn was found to have different patterns of expression even in the same mutation type. The therapeutic effect of EGFR-TKIs was investigated in these patients, and patients with an abnormal expression of p120ctn were found to be more likely to have drug resistance. A gefitinib-resistant lung cancer cell line was established and alterations in the p120ctn expression pattern were also observed in vitro.

CONCLUSIONS

Therefore, this study demonstrates that the expression pattern of p120ctn is associated with acquired resistance to EGFR-TKIs in lung cancer, providing information toward addressing the problem of drug resistance in patients with non-small cell lung cancer.

p120-catenin is required for regulating epidermal proliferation, differentiation, and barrier function

p120-catenin (p120) is an important regulator in the function and stability of E-cadherin. However, the role of p120 in the epidermis is unclear. Previous studies have shown that globally knockout of p120 caused increased epidermal proliferation but little changes in epidermal differentiation and permeability. In the present study, we generated a conditional knockout mouse model and examined epidermal proliferation, differentiation and permeability. The results showed that conditional knockout of p120 in the epidermis caused not only increased epidermal proliferation but also decreased epidermal differentiation and increased permeability. These data suggest that p120 is required for suppressing epidermal proliferation, promoting epidermal differentiation and maintaining permeability barrier function of the epidermis.

Jinfu'an Decoction Inhibits Invasion and Metastasis in Human Lung Cancer Cells (H1650) via p120ctn-Mediated Induction and Kaiso

BACKGROUND Previous research showed that Jin-Fu-An decoction has a significant effect on lung cancer. However, it remains unclear whether p120ctn and its transcription factor Kaiso play a role in lung cancer cell proliferation, adhesion, migration, and metastasis. MATERIAL AND METHODS Proliferation inhibition was detected by CCK-8 assay. The migration and invasion were detected using Transwell assay. The location and expression of p120ctn and Kaiso were monitored by immunofluorescence staining. The expression changes of p120ctn, its isoform 1A, its S288 phosphorylation, and Kaiso were measured by Western blot assay. RESULTS The lung cancer cell line H1650 administered Jin-Fu-An decoction had significantly reduced the growth in dose-dependent and time-dependent manners. Migration and metastasis were significantly inhibited by application of Jin-Fu-An decoction in a dose-dependent manner. Additionally, Jin-Fu-An decoction decreased the expressions of p120ctn, its isoform 1A, and its S288 phosphorylation, but the protein level of Kaiso was elevated. CONCLUSIONS Jin-Fu-An decoction inhibits the proliferation, adhesion, migration, and metastasis though down-regulation of p120ctn or its isoform 1A expression, mediating the up-regulation of Kaiso. The underlying mechanism of Jin-Fu-An decoction might involve targeting the lower expression of p120ctn S288 phosphorylation, which suggests that Jin-Fu-An decoction may be a potential therapeutic measure as prevention and control of recurrence and metastasis of lung cancer.

Emerging Non-Canonical Functions and Regulation by p53: p53 and Stemness

Since its discovery nearly 40 years ago, p53 has ascended to the forefront of investigated genes and proteins across diverse research disciplines and is recognized most exclusively for its role in cancer as a tumor suppressor. Levine and Oren (2009) reviewed the evolution of p53 detailing the significant discoveries of each decade since its first report in 1979. In this review, we will highlight the emerging non-canonical functions and regulation of p53 in stem cells. We will focus on general themes shared among p53's functions in non-malignant stem cells and cancer stem-like cells (CSCs) and the influence of p53 on the microenvironment and CSC niche. We will also examine p53 gain of function (GOF) roles in stemness. Mutant p53 (mutp53) GOFs that lead to survival, drug resistance and colonization are reviewed in the context of the acquisition of advantageous transformation processes, such as differentiation and dedifferentiation, epithelial-to-mesenchymal transition (EMT) and stem cell senescence and quiescence. Finally, we will conclude with therapeutic strategies that restore wild-type p53 (wtp53) function in cancer and CSCs, including RING finger E3 ligases and CSC maintenance. The mechanisms by which wtp53 and mutp53 influence stemness in non-malignant stem cells and CSCs or tumor-initiating cells (TICs) are poorly understood thus far. Further elucidation of p53's effects on stemness could lead to novel therapeutic strategies in cancer research.

The p53 isoform Δ133p53β promotes cancer stem cell potential

Cancer stem cells (CSC) are responsible for cancer chemoresistance and metastasis formation. Here we report that Δ133p53β, a TP53 splice variant, enhanced cancer cell stemness in MCF-7 breast cancer cells, while its depletion reduced it. Δ133p53β stimulated the expression of the key pluripotency factors SOX2, OCT3/4, and NANOG. Similarly, in highly metastatic breast cancer cells, aggressiveness was coupled with enhanced CSC potential and Δ133p53β expression. Like in MCF-7 cells, SOX2, OCT3/4, and NANOG expression were positively regulated by Δ133p53β in these cells. Finally, treatment of MCF-7 cells with etoposide, a cytotoxic anti-cancer drug, increased CSC formation and SOX2, OCT3/4, and NANOG expression via Δ133p53, thus potentially increasing the risk of cancer recurrence. Our findings show that Δ133p53β supports CSC potential. Moreover, they indicate that the TP53 gene, which is considered a major tumor suppressor gene, also acts as an oncogene via the Δ133p53β isoform.

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The Δ133p53β isoform promotes stemness of breast cancer cells

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The Δ133p53β isoform regulates SOX2, OCT3/4, and NANOG expression, but not C-MYC

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Etoposide promotes cancer cell stemness through Δ133p53β induction

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Δ133p53β expression, like p53 mutations, promotes cancer cell stemness

The expression of δ-catenin in esophageal squamous cell carcinoma and its correlations with prognosis of patients

As a member of the catenin family, expression of δ-catenin and its clinical implication in numerous tumors remain unclear. In the present study, expression of δ-catenin in esophageal squamous cell carcinoma (ESCC) and its correlations with patient prognosis were explored. We detected the expression of δ-catenin, by immunohistochemistry, in ESCC tissues from 299 cases and analyzed the correlation between δ-catenin expression and patient clinicopathological features. Compared with a lack of expression in adjacent normal esophageal epithelium (0%, 0/47), the frequency of δ-catenin protein was increased in ESCC tissues to 41.5% (124/299, P < .001) and expression correlated with TNM stage and lymph node metastasis (P = .025 and .019, respectively). Furthermore, Kaplan-Meier survival analysis revealed that patients with high δ-catenin expression had shorter survival than patients with low expression (P = .010), and multivariate Cox analysis revealed that high δ-catenin expression was also an independent prognostic factor (P = .001). In transwell assays, migration of ESCC cells was enhanced by δ-catenin overexpression, whereas proliferation of ESCC cells was unchanged. Together, our results suggest that δ-catenin acts as an oncoprotein when overexpressed in ESCC, and its expression is associated with poor prognosis and malignant cell behavior.

Impact of p120-catenin isoforms 1A and 3A on epithelial mesenchymal transition of lung cancer cells expressing E-cadherin in different subcellular locations

The epithelial mesenchymal transition (EMT) is an important process in tumor development. Despite previous investigations, it remains unclear how p120-catenin (p120ctn) isoforms 1A and 3A affect the EMT of tumor cells. Here we investigated expression of p120ctn, E-cadherin and vimentin in 78 human non-small cell lung cancer (NSCLC) samples by immunohistochemistry and found that p120ctn membrane expression positively correlated with E-cadherin expression (P<0.001) and negatively correlated with vimentin expression and lymph node metastasis (P<0.05). Meanwhile, p120ctn cytoplasmic expression negatively correlated with E-cadherin expression (P<0.001) and positively correlated with vimentin expression and lymph node metastasis (P<0.05). Cells expressing high (H460 and SPC) and low (H1299 and LK2) levels of p120ctn were screen to investigate its impact on EMT. E-cadherin was restricted to the cell membrane in H460 and H1299 cells, whereas it was expressed in the cytoplasm of SPC and LK2 cells. Ablation of endogenous p120ctn isoform 1A in cells expressing high levels of the protein resulted in decreased E-cadherin expression, increased N-cadherin, vimentin and snail expression and enhanced invasiveness in H460 cells. Meanwhile, completely opposite results were observed in SPC cells. Furthermore, transfection of in H1299 cells expressing low p120ctn levels with the p120ctn isoform 1A plasmid resulted in increased E-cadherin expression, decreased N-cadherin, vimentin and snail expression and weakened invasiveness, while LK2 cells showed completely opposite results. Both cell lines expressing low p120ctn levels and transfected with the p120ctn isoform 3A plasmid appeared to have increased E-cadherin expression, decreased N-cadherin, vimentin and snail expression and weakened invasiveness. In conclusion, in cells with membrane E-cadherin, both p120ctn isoforms 1A and 3A inhibited EMT and decreased cell invasiveness. In cells with cytoplasmic E-cadherin, p120ctn isoform 1A promoted EMT and increased cell invasiveness, while p120ctn isoform 3A inhibited the EMT and decreased cell invasiveness.

Kaiso interacts with p120-catenin to regulate β-catenin expression at the transcriptional level

BACKGROUND

We have reported that p120-catenin could regulate β-catenin transcription in lung cancer cells, but the specific mechanism is unclear.

METHODS AND RESULTS

In this study, bisulfite sequencing PCR showed that the β-catenin promoter region in SPC-A-1 and LTEP-a-2 lung cancer cell lines has Kaiso binding sites sequences and CpG islands which may combine with Kaiso. The demethylating reagent 5-Aza-2'-deoxycytidine significantly upregulated β-catenin mRNA expression in lung cancer cell lines, whereas expression was significantly reduced following transfection with Kaiso. However, the upregulation of β-catenin mRNA expression after treatment with 5-Aza-2'-deoxycytidine was not reduced by subsequent transfection with Kaiso cDNA. Chromatin immunoprecipitation showed that, in lung cancer cell lines, methylated CpG-dinucleotides sequences combined with Kaiso and the Kaiso binding sites sequence did not. The capacity of Kaiso to combine with p120-catenin isoforms was confirmed by immunoprecipitation.

CONCLUSIONS

Based on these results, we concluded that Kaiso participates in the regulation by p120ctn of β-catenin mRNA expression in the lung cancer cell lines.

Overexpression of a novel regulator of p120 catenin, NLBP, promotes lung adenocarcinoma proliferation

NLBP (novel LZAP-binding protein) was recently shown to function as a tumor suppressor capable of inhibiting the NFκB signaling pathway. NLBP is also known as a negative regulator of cell invasion, and its expression is reduced in several cancer cell lines that have little invasive activity. Although these phenomena suggest that NLBP may be a potential tumor suppressor, its role as a tumor suppressor in human lung cancer is not well established. In contrast to our expectation, NLBP was highly expressed in the early stage of lung adenocarcinoma tissues, and overexpression of NLBP promoted proliferation of H1299 lung adenocarcinoma cells. We also found that p120 catenin (p120ctn) was a novel binding partner of NLBP, and that NLBP binds to the regulatory domain of p120ctn, and p120ctn associates with N-terminal region of NLBP, respectively. This binding leads to p120ctn stability to inhibit proteasomal degradation of p120ctn by inhibiting its ubiqutination. In addition, we also found that overexpression of NLBP and p120ctn in human lung cancer are closely related with adenocarcinoma compared with squamous cell carcinoma. Taken together, our findings reveal that NLBP is highly overexpressed in human lung adenocarcinoma, and that overexpression of NLBP promotes the cell proliferation of lung adenocarcinoma through interacting with p120ctn and suggest that NLBP may function as an oncogene in early stage carcinogenesis of lung adenocarcinoma.

Down's-syndrome-related kinase Dyrk1A modulates the p120-catenin-Kaiso trajectory of the Wnt signaling pathway

The Wnt pathways contribute to many processes in cancer and development, with β-catenin being a key canonical component. p120-catenin, which is structurally similar to β-catenin, regulates the expression of certain Wnt target genes, relieving repression conferred by the POZ- and zinc-finger-domain-containing transcription factor Kaiso. We have identified the kinase Dyrk1A as a component of the p120-catenin-Kaiso trajectory of the Wnt pathway. Using rescue and other approaches in Xenopus laevis embryos and mammalian cells, we found that Dyrk1A positively and selectively modulates p120-catenin protein levels, thus having an impact on p120-catenin and Kaiso (and canonical Wnt) gene targets such as siamois and wnt11. The Dyrk1A gene resides within the Down's syndrome critical region, which is amplified in Down's syndrome. A consensus Dyrk phosphorylation site in p120-catenin was identified, with a mutant mimicking phosphorylation exhibiting the predicted enhanced capacity to promote endogenous Wnt-11 and Siamois expression, and gastrulation defects. In summary, we report the biochemical and functional relationship of Dyrk1A with the p120-catenin-Kaiso signaling trajectory, with a linkage to canonical Wnt target genes. Conceivably, this work might also prove relevant to understanding the contribution of Dyrk1A dosage imbalance in Down's syndrome.

Expression of P120 catenin, Kaiso, and metastasis tumor antigen-2 in thymomas

Thymomas of the same histological subtype sometimes manifest different biological behaviors. Metastasis Tumor Antigen-2 (MTA2) is targeted by the transcriptional repressor Kaiso, the distribution which is thought to be modulated by p120catenin (p120ctn). It is currently unclear if expression of p120ctn, Kaiso, and MTA2 relates to the biological behavior of thymoma. P120ctn, Kaiso, and MTA2 expression were examined in 137 cases of thymoma, three cases of thymic carcinoma, and 18 paired autologous normal thymic tissues using immunohistochemistry, and correlation of these proteins with histological subtypes and clinical stages were analyzed. In normal thymic epithelial cells, p120ctn was expressed on the cell membrane but Kaiso and MTA2 were not detected. Membranous p120ctn expression was reduced in thymoma epithelial cells, while ectopic cytoplasmic expression was observed in 76.6 % (105/137) of the cases. Cytoplasmic Kaiso was detected in 69.3 % (95/137) and nuclear MTA2 was detected in 70.8 % (97/137) of the thymomas. There were good consistencies (Kappa = 0.559, 0.512, 0.652; all P < 0.001) and correlations (r = 0.733, 0.652, 0.708; all P < 0.001) between cytoplasmic p120ctn, cytoplasmic Kaiso, and nuclear MTA2 expression in thymomas. All three protein factors correlated with histological type and clinical stage in thymoma (P < 0.05). Specifically, cytoplasmic p120ctn and Kaiso expression and nuclear MTA2 expression were higher in high-risk (types B2 and B3) thymomas and Masaoka stage III/IV thymomas than low-risk (types A, AB, and B1) and stage I/II thymomas (both P < 0.001), respectively. Cytoplasmic p120ctn, cytoplasmic Kaiso, and nuclear MTA2 expression correlated directly with histological type and Masaoka stage and may thus be used as potential biomarkers to predict biological behavior of thymoma.

N-terminal 1-54 amino acid sequence and Armadillo repeat domain are indispensable for P120-catenin isoform 1A in regulating E-cadherin

P120-catenin (p120ctn) exerts important roles in regulating E-cadherin and invasiveness in cancer cells. However, the mechanisms by which p120ctn isoforms 1 and 3 modulate E-cadherin expression are poorly understood. In the current study, HBE, H460, SPC and LTE cell lines were used to examine the effects of p120ctn isoforms 1A and 3A on E-cadherin expression and cell invasiveness. E-cadherin was localized on the cell membrane of HBE and H460 cells, while it was confined to the cytoplasm in SPC and LTE cells. Depletion of endogenous p120ctn resulted in reduced E-cadherin expression; however, p120ctn ablation showed opposite effects on invasiveness in the cell lines by decreasing invasiveness in SPC and LTE cells and increasing it in HBE and H460 cells. Restitution of 120ctn isoform 1A restored E-cadherin on the cell membrane and blocked cell invasiveness in H460 and HBE cells, while it restored cytoplasmic E-cadherin and enhanced cell invasiveness in SPC and LTE cells. P120ctn isoform 3A increased the invasiveness in all four cell lines despite the lack of effect on E-cadherin expression, suggesting a regulatory pathway independent of E-cadherin. Moreover, five p120ctn isoform 1A deletion mutants were constructed and expressed in H460 and SPC cells. The results showed that only the M4 mutant, which contains N-terminal 1–54 amino acids and the Armadillo repeat domain, was functional in regulating E-cadherin and cell invasiveness, as observed in p120ctn isoform 1A. In conclusion, the N-terminal 1–54 amino acid sequence and Armadillo repeat domain of p120ctn isoform 1A are indispensable for regulating E-cadherin protein. P120ctn isoform 1A exerts opposing effects on cell invasiveness, corresponding to the subcellular localization of E-cadherin.

P120-catenin isoforms 1 and 3 regulate proliferation and cell cycle of lung cancer cells via β-catenin and Kaiso respectively

Background

The different mechanisms involved in p120-catenin (p120ctn) isoforms' 1/3 regulation of cell cycle progression are still not elucidated to date.

Methods and Findings

We found that both cyclin D1 and cyclin E could be effectively restored by restitution of p120ctn-1A or p120ctn-3A in p120ctn depleted lung cancer cells. When the expression of cyclin D1 was blocked by co-transfection with siRNA-cyclin D1 in p120ctn depleted cells restoring p120ctn-1A or 3A, the expression of cyclin E was slightly decreased, not increased, implying that p120ctn isoforms 1 and 3 cannot up-regulate cyclin E directly but may do so through up-regulation of cyclin D1. Interestingly, overexpression of p120ctn-1A increased β-catenin and cyclin D1 expression, while co-transfection with siRNA targeting β-catenin abolishes the effect of p120ctn-1A on up-regulation of cyclin D1, suggesting a role of β-catenin in mediating p120ctn-1A's regulatory function on cyclin D1 expression. On the other hand, overexpression of p120ctn isoform 3A reduced nuclear Kaiso localization, thus decreasing the binding of Kaiso to KBS on the cyclin D1 promoter and thereby enhancing the expression of cyclin D1 gene by relieving the repressor effect of Kaiso. Because overexpressing NLS-p120ctn-3A (p120ctn-3A nuclear target localization plasmids) or inhibiting nuclear export of p120ctn-3 by Leptomycin B (LMB) caused translocation of Kaiso to the nucleus, it is plausible that the nuclear export of Kaiso is p120ctn-3-dependent.

Conclusions

Our results suggest that p120ctn isoforms 1 and 3 up-regulate cyclin D1, and thereby cyclin E, resulting in the promotion of cell proliferation and cell cycle progression in lung cancer cells probably via different protein mediators, namely, β-catenin for isoform 1 and Kaiso, a negative transcriptional factor of cyclin D1, for isoform 3.

Overexpression of small GTPases directly correlates with expression of δ-catenin and their coexpression predicts a poor clinical outcome in nonsmall cell lung cancer

δ-catenin can affect cytoskeletal assembly, and promote cell migration by regulating the activity of small GTPases. While many malignancies have been shown to be positive for δ-catenin, it is still unclear whether δ-catenin and small GTPases are coexpressed in tumor cells, and so is the relationship between their coexpression and prognosis in the tumor patients. In this study, immunohistochemistry was performed to examine expressive levels of δ-catenin, cdc42, and Rac1 in 135 cases of nonsmall cell lung cancer (NSCLC), including 60 cases with follow-up records. Thirty samples of paired lung cancer tissues and adjacent normal lung tissues were collected to analyze mRNA and protein expression of δ-catenin and small GTPases. The effects of δ-catenin on small GTPases expression and invasive ability of lung cancer cells were also evaluated. Compared with normal lung tissues, both mRNA and protein levels of δ-catenin and small GTPases were increased in lung cancer tissues (P < 0.05), and the expression of small GTPases directly correlated with that of δ-catenin (P < 0.001). In addition, δ-catenin and small GTPases tended to be coexpressed in lung adenocarcinoma, advanced stages, and primary tumors with lymph node metastasis (all P < 0.05). The patients with coexpression of δ-catenin and small GTPases had a shorter survival time than those without coexpression (P < 0.05). Furthermore, δ-catenin overexpression could enhance invasive ability of lung cancer cells by upregulating protein and transcriptional level of small GTPases. Therefore, δ-catenin likely upregulates the activity of small GTPases at transcriptional level, and their coexpression may predict a poor clinical outcome in NSCLC patients.

p120 catenin is required for normal renal tubulogenesis and glomerulogenesis

Defects in the development or maintenance of tubule diameter correlate with polycystic kidney disease. Here, we report that absence of the cadherin regulator p120 catenin (p120ctn) from the renal mesenchyme prior to tubule formation leads to decreased cadherin levels with abnormal morphologies of early tubule structures and developing glomeruli. In addition, mutant mice develop cystic kidney disease, with markedly increased tubule diameter and cellular proliferation, and detached luminal cells only in proximal tubules. The p120ctn homolog Arvcf is specifically absent from embryonic proximal tubules, consistent with the specificity of the proximal tubular phenotype. p120ctn knockdown in renal epithelial cells in 3D culture results in a similar cystic phenotype with reduced levels of E-cadherin and active RhoA. We find that E-cadherin knockdown, but not RhoA inhibition, phenocopies p120ctn knockdown. Taken together, our data show that p120ctn is required for early tubule and glomerular morphogenesis, as well as control of luminal diameter, probably through regulation of cadherins.

c-Crk proto-oncogene contributes to transcriptional repression of p120-catenin in non-small cell lung cancer cells

As a member of adherens junction, p120-catenin (p120ctn) plays a major role in cell adhesions through stabilization of E-cadherin. p120ctn is transcriptionally down-regulated in non-small cell lung cancer (NSCLC), although the molecular mechanisms underlying p120ctn repression are incompletely defined. Here we further investigated transcriptional regulation of p120ctn in NSCLC. We prepared a promoter reporter plasmid construct that contained p120ctn promoter region from position -1082 to +320 relative to transcription start site. Through serial deletion mutation analysis of the p120ctn promoter, we pinpointed cis-acting elements involved in regulation of p120ctn. We identified transcription factor SP1 as a transcriptional repressor of p120ctn that directly binds to segment (-9 to +36) of the p120ctn promoter. SP1 can receive multiple signals from several intracellular signaling pathways. Through examination of SP1 binding partners, we identified proto-oncogene c-Crk to be involved in transcriptional down-regulation of p120ctn. RNAi mediated silencing of CRK in A549, H157 and H358 cells increased p120ctn protein levels. On the other hand, over-expression of CRK-I and CRK-II in NSCLC cells down-regulated p120ctn, an effect that was abrogated by simultaneous silencing of SP1. In summary, our data provide evidence for the role of c-Crk proto-oncogene in transcriptional repression of p120ctn that further clarifies the mechanism by which this biochemical signal promotes metastasis in NSCLC.

Upregulation of δ-catenin is associated with poor prognosis and enhances transcriptional activity through Kaiso in non-small-cell lung cancer

δ-Catenin is the only member of the p120 catenin (p120ctn) subfamily that its primary expression is restricted to the brain. Since δ-catenin is upregulated in human lung cancer, the effects of δ-catenin overexpression in lung cancer still need to be clarified. Immunohistochemistry was performed to investigate the expression of δ-catenin and Kaiso, a δ-catenin-binding transcription factor, in 151 lung cancer specimens. A correlation between cytoplasmic δ-catenin and Kaiso expression was also associated with high TNM stage, lymph node metastases and poor prognosis. Co-immunoprecipitation assay confirmed the interactions of δ-catenin and Kaiso in lung cancer cells. In addition, gene transfection and RNAi technology were used to demonstrate that increased δ-catenin expression was promoted, whereas its knockdown suppressed its lung cancer invasive ability. In addition, methylation-specific PCR and ChIP assay demonstrated that δ-catenin could regulate MTA2 via Kaiso in a methylation-dependent manner, while it could regulate cyclin D1 and MMP7 expression through Kaiso in a sequence-specific manner. In conclusion, a δ-catenin/Kaiso pathway exists in lung cancer cells. Increased δ-catenin expression is critical for maintenance of the malignant phenotype of lung cancer, making δ-catenin a candidate target protein for future cancer therapeutics.

Shared molecular mechanisms regulate multiple catenin proteins: canonical Wnt signals and components modulate p120-catenin isoform-1 and additional p120 subfamily members

Wnt signaling pathways have fundamental roles in animal development and tumor progression. Here, employing Xenopus embryos and mammalian cell lines, we report that the degradation machinery of the canonical Wnt pathway modulates p120-catenin protein stability through mechanisms shared with those regulating β-catenin. For example, in common with β-catenin, exogenous expression of destruction complex components, such as GSK3β and axin, promotes degradation of p120-catenin. Again in parallel with β-catenin, reduction of canonical Wnt signals upon depletion of LRP5 and LRP6 results in p120-catenin degradation. At the primary sequence level, we resolved conserved GSK3β phosphorylation sites in the amino-terminal region of p120-catenin present exclusively in isoform-1. Point-mutagenesis of these residues inhibited the association of destruction complex components, such as those involved in ubiquitylation, resulting in stabilization of p120-catenin. Functionally, in line with predictions, p120 stabilization increased its signaling activity in the context of the p120-Kaiso pathway. Importantly, we found that two additional p120-catenin family members, ARVCF-catenin and δ-catenin, associate with axin and are degraded in its presence. Thus, as supported using gain- and loss-of-function approaches in embryo and cell line systems, canonical Wnt signals appear poised to have an impact upon a breadth of catenin biology in vertebrate development and, possibly, human cancers.

delta-Catenin promotes malignant phenotype of non-small cell lung cancer by non-competitive binding to E-cadherin with p120ctn in cytoplasm

As a member of the catenin family, little is known about the clinical significance and possible mechanism of delta-catenin expression in numerous tumours. We examined the expression of delta-catenin by immunohistochemistry in 115 cases of non-small cell lung cancer (NSCLC) (including 65 cases with follow-up records and 50 cases with paired lymph node metastasis lesions). The mRNA and protein expression of delta-catenin was also detected in 30 cases of paired lung cancer tissues and normal lung tissues by RT-PCR and western blotting, respectively. Co-immunoprecipitation was used to examine whether delta-catenin competitively bound to E-cadherin with p120ctn in lung cancer cells or not. The effects of delta-catenin on the activity of small GTPases and the biological behaviour of lung cancer cells were explored by pull-down assay, flow cytometry, MTT, and Matrigel invasive assay. The results showed that the mRNA and protein expression of delta-catenin was increased in lung cancer tissues; the positive expression rate of delta-catenin was significantly increased in adenocarcinoma, stage III-IV, paired lymph node metastasis lesions, and primary tumours with lymph node metastasis (all p < 0.05); and the postoperative survival period of patients with delta-catenin-positive expression was shorter than that of patients with delta-catenin-negative expression (p < 0.05). No competition between delta-catenin and p120ctn for binding to E-cadherin in cytoplasm was found in two lung cancer cell lines. By regulating the activity of small GTPases and changing the cell cycle, delta-catenin could promote the proliferation and invasion of lung cancer cells. We conclude that delta-catenin is an oncoprotein overexpressed in NSCLC and that increased delta-catenin expression is critical for maintenance of the malignant phenotype of lung cancer.

Downregulation of HDPR1 is associated with poor prognosis and affects expression levels of p120-catenin and beta-catenin in nonsmall cell lung cancer

HDPR1 (human homologue of Dapper) is considered as a Dishevelled (DVL) antagonist in WNT signaling. We recently reported that DVL was associated with cytoplasmic accumulation of beta-catenin in nonsmall cell lung cancer (NSCLC). Whether cytoplasmic accumulation of beta-catenin is correlated with HDPR1 is unclear. Xenopus Dapper (XDpr) was found to stabilize p120-catenin (p120ctn) in Xenopus embryogenesis. However, whether HDPR1 can regulate p120ctn expression level is not reported. Furthermore, how HDPR1 influences invasiveness in lung carcinogenesis is also not well understood. In this study, our aims were to explore the effects of HDPR1 on the lung carcinogenesis and to examine the relationship among HDPR1, beta-catenin, and p120ctn. Immunohistochemical analysis in 120 NSCLC tissues showed that HDPR1 was significantly lower in 82 specimens (68.3%). Reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting analysis showed that the mRNA and protein expression of HDPR1 were lower in tumor tissues as compared to corresponding nontumorous tissues. Moreover, reduced HDPR1 expression was related to the clinicopathological factors and was an independent risk factor for prognosis of the patients with NSCLC. In addition, HDPR1 expression was also associated with the expression of p120ctn and beta-catenin in lung cancer tissues. Knockdown of HDPR1 gene enhanced the invasive ability of lung cancer cells, which was dependent on p120ctn and independent of beta-catenin. In conclusion, the function of HDPR1 on regulating p120ctn may play an important role in human lung carcinogenesis. Restoration of HDPR1 gene may be a new therapeutic target of lung cancer.

p120ctn isoform 1 expression significantly correlates with abnormal expression of E-cadherin and poor survival of lung cancer patients

Different p120ctn isoforms exert different, even opposing, effects on tumor cell growth depending on the level of E-cadherin expression, but the impact on clinicopathological parameters of lung cancer patients is not clear. Herein, we investigate the correlation between pan-p120ctn, p120ctn isoform 1, and E-cadherin expression and clinicopathological parameters, especially prognosis, of lung cancer patients. Immunohistochemistry on 20 specimens of normal bronchial epthelium revealed that, p120ctn isoform 1 was not expressed at the membrane; only weak cytoplasmic expression was seen. In contrast, both pan-p120ctn and E-cadherin were expressed clearly on the cell membrane or in the cytoplasmic peri-membrane region. However, in squamous cell lung cancer or lung adenocarcinomas, p120ctn isoform 1 over-expressed in the cytoplasm accompany with the abnormal pan-p120ctn and E-cadherin cytoplasm expression. p120ctn isoform 1 over-expression correlated positively with lymph node metastasis, poor differentiation, histological type, and high TNM stage. Cytoplasmic p120ctn isoform 1 expression in metastatic nodules was always higher than in the primary tumor. While the mean survival times of patients with normal p120 ctn isoform 1 or pan-p120ctn expression differed significantly, the mean survival times of patients with abnormal expression were similar. Lymph node metastasis, TNM stage, abnormal pan-p120ctn expression, and p120ctn isoform 1 over-expression were all independent factors affecting the prognosis of lung cancer patients. Over-expression of p120ctn isoform 1 positively correlated with poor prognosis of lung cancer patients, and therefore may be a useful marker of lung cancer patient survival.