Molecular basis for the tissue specificity of β-catenin oncogenesis

DGKA interacts with SRC/FAK to promote the metastasis of non-small cell lung cancer

Metastasis is responsible for the high mortality rate of lung cancer, but its underlying molecular mechanisms are poorly understood. Here, we demonstrated that the expression of diacylglycerol kinase alpha (DGKA) was elevated in the metastatic lesions of non-small cell lung cancer (NSCLC) and correlated with poor survival. Mechanistic studies revealed a direct physical interaction as well as a mutual regulation among DGKA, proto-oncogene tyrosine-protein kinase Src (SRC), and focal adhesion kinase 1 (FAK) proteins. The C-terminal domain of DGKA was responsible for the SRC SH3 domain binding, while the catalytic domain of DGKA interacted with the FREM domain of FAK. DGKA phosphorylated the SRC protein at Tyr416 and the FAK protein at Tyr397 to form and activate the DGKA/SRC/FAK complex, thus initiating the downstream WNT/β-catenin and VEGF signaling pathways, promoting epithelial-mesenchymal transition (EMT) and angiogenesis, and resulting in the metastasis of NSCLC. DGKA knockdown inhibited the invasive phenotype of NSCLC cells in vitro. Pharmacologic ablation of DGKA inhibited the metastasis of NSCLC cells in vivo, and this was reversed by the overexpression of DGKA. These results suggested that DGKA was a potential prognostic biomarker as well as a promising therapeutic target for NSCLC, especially when there was lymphatic or distant metastasis.

Non-target genetic manipulation induces rhabdomyosarcoma in KrasPten-driven mouse model of ovarian cancer

Background

Genetically engineered mice are ideal models to advance our understanding the tumorigenesis of ovarian cancer. Our original objective was to establish an ovarian cancer model induced by Kras activation and Pten deletion. However, proficiently establishing the model remains a technical problem, which limits its application.

Methods

We established the Kras activation/Pten deletion-induced mouse model of ovarian cancer by injecting Cre recombinase-expressing adenovirus in the ovarian bursa. PCR analysis, Western blotting, and immunohistochemistry staining were performed to verify the alteration of conditional genes. We detected expression of canonical molecular markers in order to examine the origin of the tumors.

Results

Subcutaneous lumps developed accidentally in mice with ovarian cancer, as early as 2 weeks post in vivo genetic manipulation, far before the destructive growth of ovarian cancer. PCR analysis confirmed the efficient Cre-mediated recombination of Kras and Pten in tumor tissues, which are consistent with the activation of the MAPK and PI3K/Akt/mTOR pathways. Histomorphological and histological analysis showed that the lumps were actually rhabdomyosarcoma (RMS). We confirmed that the leakage of adenovirus transformed healthy adjacent tissues into RMS.

Conclusions

Avoiding accidental exposure of non-target tissues to adenovirus is crucial to successfully establish the ovarian cancer mouse model. Moreover, non-specific genetic manipulations can induce the development of RMS.

CTNNB1 Knockdown Inhibits Cell Proliferation and Aldosterone Secretion Through Inhibiting Wnt/β-Catenin Signaling in H295R Cells

Aldosterone-producing adenomas (APA) is one of the causative factors of primary aldosteronism. Previous studies have suggested that there are somatic CTNNB1 mutations in APA, but the specific mechanism of CTNNB1 mutation in APA tumorigenesis and aldosterone secretion remains unclear. In the present study, human adrenocortical carcinoma cell line H295 R was used to establish stable CTNNB1 knockdown cell lines. Cell proliferation and aldosterone secretion of H295 R cells in response to angiotensin Ⅱ (Agn Ⅱ) were analyzed. We found that CTNNB1 knockdown reduced β-catenin expression and inhibited proliferation of H295 R cells. CTNNB1 knockdown inhibited Wnt/β-catenin signaling pathway and downregulated expression of downstream genes including axin 2, lymphoid enhancer binding factor 1 (LEF1), and cyclin D1. In addition, CTNNB1 knockdown decreased responses of H295 R cells to Agn Ⅱ and decreased aldosterone secretion. Our findings suggest that CTNNB1 knockdown can inhibit H295 R cell proliferation and decrease aldosterone secretion in the responses of H295 R cells to Ang II through inhibiting Wnt/β-catenin signaling pathway, indicating that targeting Wnt/β-catenin signaling pathway may be an important approach to decrease aldosterone secretion in the treatment of aldoster-producing adenomas.

An immunohistochemical approach to detect oncogenic CTNNB1 mutations in primary neoplastic tissues

The Wnt/β-catenin signaling pathway is dysregulated in different types of neoplasms including colorectal cancer (CRC). Aberrant activation of this signaling pathway is a key early event in the development of colorectal neoplasms, and is mainly caused by loss of function mutations in Adenomatous Polyposis Coli (APC), and less frequently by β-catenin stabilization mutations via missense or interstitial genomic deletions in CTNNB1. In this study, we have defined an immunohistochemical algorithm to dissect Wnt pathway alterations in formalin-fixed and paraffin-embedded neoplastic tissues. Basically, consecutive sections of tumor specimens were stained by immunohistochemistry with two different monoclonal antibodies against β-catenin: one (anti-active β-catenin antibody) recognizes hypo-phosphorylated β-catenin and the other recognizes the total pool of β-catenin. We validated the strategy in the HCT116 CRC cell line which has an in-frame deletion of β-catenin serine 45, and then studied human tumor microarrays containing colon adenomas, CRCs, solid pseudopapillary neoplasms of the pancreas as well as the whole tissue sections of CRCs, desmoid fibromatosis, and pilomatrixoma of the skin. In some tumors, we found strong β-catenin cytoplasmic and/or nuclear staining with the total β-catenin antibody but no staining with the anti-active β-catenin antibody. This was inferred to be an altered/mutant β-catenin staining pattern. All six colon adenomas of the 126 total adenomas studied for the altered/mutant β-catenin staining pattern had presumptively pathogenic point mutations or deletions in CTNNB1. Four of 10 CRCs with the alterated/mutant β-catenin staining pattern studied in depth, from 181 total CRCs from tissue microarray, had pathogenic CTNNB1 mutations. The frequencies of CTNNB1 alterations in non-colonic tumors with altered/mutant β-catenin staining ranged between 46 and 100%. Our results demonstrate that the immunohistochemical approach described here can detect oncogenic forms of β-catenin in primary tissue samples and can also highlight other tumors with presumptive novel defects activating the Wnt/β-catenin pathway.

Wnt-signaling enhances neural crest migration of melanoma cells and induces an invasive phenotype

Background

During embryonic development Wnt family members and bone morphogenetic proteins (BMPs) cooperatively induce epithelial-mesenchymal transition (EMT) in the neural crest. Wnt and BMPs are reactivated during malignant transformation in melanoma. We previously demonstrated that the BMP-antagonist noggin blocked the EMT phenotype of melanoma cells in the neural crest and malignant invasion of melanoma cells in the chick embryo; vice-versa, malignant invasion was induced in human melanocytes in vivo by pre-treatment with BMP-2.

Results

Although there are conflicting results in the literature about the role of β-catenin for invasion of melanoma cells, we found Wnt/β-catenin signaling to be analogously important for the EMT-like phenotype of human metastatic melanoma cells in the neural crest and during invasion: β-catenin was frequently expressed at the invasive front of human primary melanomas and Wnt3a expression was inversely correlated with survival of melanoma patients. Accordingly, cytoplasmic β-catenin levels were increased during invasion of melanoma cells in the rhombencephalon of the chick embryo. Fibroblast derived Wnt3a reduced melanoma cell adhesion and enhanced migration, while the β-catenin inhibitor PKF115–584 increased adhesion and reduced migration in vitro and in the chick embryonic neural crest environment in vivo. Similarly, knockdown of β-catenin impaired intradermal melanoma cell invasion and PKF115–584 efficiently reduced liver metastasis in a chick chorioallantoic membrane model. Our observations were accompanied by specific alterations in gene expression which are linked to overall survival of melanoma patients.

Conclusion

We present a novel role for Wnt-signaling in neural crest like melanoma cell invasion and metastasis, stressing the crucial role of embryonic EMT-inducing neural crest signaling for the spreading of malignant melanoma.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0773-5) contains supplementary material, which is available to authorized users.

The role of Wnt/β-catenin signaling pathway in melanoma epithelial-to-mesenchymal-like switching: evidences from patients-derived cell lines

Deregulations or mutations of WNT/β-catenin signaling have been associated to both tumour formation and progression. However, contradictory results concerning the role of β-catenin in human melanoma address an open question on its oncogenic nature and prognostic value in this tumour. Changes in WNT signaling pathways have been linked to phenotype switching of melanoma cells between a highly proliferative/non-invasive and a slow proliferative/metastatic condition. We used a novel panel of cell lines isolated from melanoma specimens, at initial passages, to investigate phenotype differences related to the levels and activity of WNT/β-catenin signaling pathway. This in vitro cell system revealed a marked heterogeneity that comprises, in some cases, two distinct tumour-derived subpopulations of cells presenting a different activation level and cellular distribution of β-catenin. In cells derived from the same tumor, we demonstrated that the prevalence of LEF1 (high β-catenin expressing cells) or TCF4 (low β-catenin expressing cells) as β-catenin partner for DNA binding, is associated to the expression of two distinct profiles of WNT-responsive genes. Interestingly, melanoma cells expressing relative low level of β-catenin and an invasive markers signature were associated to the TNF-α-induced pro-inflammatory pathway and to the chemotherapy resistance, suggesting that the co-existence of melanoma subpopulations with distinct biological properties could influence the impact of chemo- and immunotherapy.

Wnt Signaling as Master Regulator of T-Lymphocyte Responses: Implications for Transplant Therapy

T cell-mediated immune responses to the grafted tissues are the major reason for failed organ transplantation. The regulation of T cell responses is complex and involves major histocompatibility complex molecules on transplanted organs, cytokines, regulatory cells, and antigen-presenting cells. The evolutionary conserved Wnt signal transduction pathway has long been known for its importance in development of stem cells and immature T cells in the thymus. Recent evidence indicates the Wnt pathway as a master regulator of T cell immune responses via governing the balance between T helper 17/regulatory T cells and by regulating the formation of effector and memory cytotoxic CD8 T cell responses. In doing so, Wnt signals influence the outcome of immune responses in transplantation settings.

MUC4 is negatively regulated through the Wnt/β-catenin pathway via the Notch effector Hath1 in colorectal cancer

MUC4 is a transmembrane mucin lining the normal colonic epithelium. The aberrant/de novo over-expression of MUC4 is well documented in malignancies of the pancreas, ovary and breast. However, studies have reported the loss of MUC4 expression in the majority of colorectal cancers (CRCs). A MUC4 promoter analysis showed the presence of three putative TCF/LEF sites, implying a possible regulation by the Wnt/β-catenin pathway, which has been shown to drive CRC progression. Thus, the objective of our study was to determine whether MUC4 is regulated by β-catenin in CRC. We first knocked down (KD) β-catenin in three CRC cell lines; LS180, HCT-8 and HCT116, which resulted in increased MUC4 transcript and MUC4 protein. Additionally, the overexpression of stabilized mutant β-catenin in LS180 and HCT-8 resulted in a decrease in MUC4 expression. Immunohistochemistry (IHC) of mouse colon tissue harboring tubular adenomas and high grade dysplasia showed dramatically reduced Muc4 in lesions relative to adjacent normal tissue, with increased cytosolic/nuclear β-catenin. Luciferase assays with the complete MUC4 promoter construct p3778 showed increased MUC4 promoter luciferase activity in the absence of β-catenin (KD). Mutation of all three putative TCF/LEF sites showed that MUC4 promoter luciferase activity was increased relative to the un-mutated promoter. Interestingly, it was observed that MUC4 expressing CRC cell lines also expressed high levels of Hath1, a transcription factor repressed by both active Wnt/β-catenin and Notch signaling. The KD of β-catenin and/or treatment with a Notch γ-secretase inhibitor, Dibenzazepine (DBZ) resulted in increased Hath1 and MUC4 in LS180, HCT-8 and HCT116. Furthermore, overexpression of Hath1 in HCT-8 and LS180 caused increased MUC4 transcript and MUC4 protein. Taken together, our results indicate that the Wnt/β-catenin pathway suppresses the Notch pathway effector Hath1, resulting in reduced MUC4 in CRC.

Molecular etiology of an indolent lymphoproliferative disorder determined by whole-genome sequencing

In an attempt to assess potential treatment options, whole-genome and transcriptome sequencing were performed on a patient with an unclassifiable small lymphoproliferative disorder. Variants from genome sequencing were prioritized using a combination of comparative variant distributions in a spectrum of lymphomas, and meta-analyses of gene expression profiling. In this patient, the molecular variants that we believe to be most relevant to the disease presentation most strongly resemble a diffuse large B-cell lymphoma (DLBCL), whereas the gene expression data are most consistent with a low-grade chronic lymphocytic leukemia (CLL). The variant of greatest interest was a predicted NOTCH2-truncating mutation, which has been recently reported in various lymphomas.

The expression of tumour suppressors and proto-oncogenes in tissues susceptible to their hereditary cancers

BACKGROUND

Studies of familial cancers have found that only a small subset of tissues are affected by inherited mutations in a given tumour suppressor gene (TSG) or proto-oncogene (POG), even though the mutation is present in all tissues. Previous tests have shown that tissue specificity is not due to the presence vs absence of gene expression, as TSGs and POGs are expressed in nearly every type of normal human tissue. Using published microarray expression data we tested the related hypothesis that tissue-specific expression of a TSG or POG is highest in tissue where it is of oncogenic importance.

METHODS

We tested this hypothesis by examining whether individual TSGs and POGs had higher expression in the normal (noncancerous) tissues where they are implicated in familial cancers relative to those tissues where they are not. We examined data for 15 TSGs and 8 POGs implicated in familial cancer across 12 human tissue types.

RESULTS

We found a significant difference between expression levels in susceptible vs nonsusceptible tissues. It was found that 9 (60%, P<0.001) of the TSGs and 5 (63%, P<0.001) of the POGs had their highest expression level in the tissue type susceptible to their oncogenic effect.

CONCLUSIONS

This highly significant association supports the hypothesis that mutation of a specific TSG or POG is likely to be most oncogenic in the tissue where the gene has its highest level of expression. This suggests that high expression in normal tissues is a potential marker for linking cancer-related genes with their susceptible tissues.

From inception to output, Tcf1 and Lef1 safeguard development of T cells and innate immune cells

Transcription factors have recurring roles during T cell development and activation. Tcf1 and Lef1 are known to be essential for early stages of thymocyte maturation. Recent research has revealed several novel aspects of their functionality. Tcf1 is induced at the very earliest step of specifying hematopoietic progenitors to the T cell lineage as a key target gene downstream of Notch activation. In addition to promoting maturation of T-lineage-committed thymocytes, Tcf1 functions as a tumor suppressor in developing thymocytes, and this is mediated, paradoxically, by restraining Lef1 expression. After positive selection, Tcf1 and Lef1 act together to direct CD4(+)CD8(+) double positive thymocytes to a CD4(+) T cell fate. Although not required for CD8(+) T cell differentiation, Tcf1 and Lef1 cooperate with Runx factors to achieve stable silencing of the Cd4 gene in CD8(+) T cells. Tcf1 is also found to have versatile roles in innate immune cells, which partly mirror its functions in mature T helper cells. Discrepancy in requirements of Tcf1/Lef1 and β-catenin in T cells has been a long-standing enigma. We will review other protein factors interacting with Tcf1 and Lef1 and discuss their regulatory roles independent of β-catenin.

A critical role for the regulated wnt-myc pathway in naive T cell survival

Wnt signaling is involved in T cell development, activation, and differentiation. However, the role for Wnt signaling in mature naive T cells has not been investigated. In this article, we report that activation of Wnt signaling in T cell lineages by deletion of the Apc (adenomatous polyposis coli) gene causes spontaneous T cell activation and severe T cell lymphopenia. The lymphopenia is the result of rapid apoptosis of newly exported, mature T cells in the periphery and is not due to defects in thymocyte development or emigration. Using chimera mice consisting of both wild-type and Apc-deficient T cells, we found that loss of naive T cells is due to T cell intrinsic dysregulation of Wnt signaling. Because Apc deletion causes overexpression of the Wnt target gene cMyc, we generated mice with combined deletion of the cMyc gene. Because combined deletion of cMyc and Apc attenuated T cell loss, cMyc overexpression is partially responsible for spontaneous T cell apoptosis and lymphopenia. Cumulatively, our data reveal a missing link between Wnt signaling and survival of naive T cells.

Premature lung aging and cellular senescence in the pathogenesis of idiopathic pulmonary fibrosis and COPD/emphysema

Different anatomic and physiological changes occur in the lung of aging people that can affect pulmonary functions, and different pulmonary diseases, including deadly diseases such as chronic obstructive pulmonary disease (COPD)/emphysema and idiopathic pulmonary fibrosis (IPF), can be related to an acceleration of the aging process. The individual genetic background, as well as exposure to a variety of toxic substances (cigarette smoke in primis) can contribute significantly to accelerating pulmonary senescence. Premature aging can impair lung function by different ways: by interfering specifically with tissue repair mechanisms after damage, thus perturbing the correct crosstalk between mesenchymal and epithelial components; by inducing systemic and/or local alteration of the immune system, thus impairing the complex mechanisms of lung defense against infections; and by stimulating a local and/or systemic inflammatory condition (inflammaging). According to recently proposed pathogenic models in COPD and IPF, premature cellular senescence likely affects distinct progenitors cells (mesenchymal stem cells in COPD, alveolar epithelial precursors in IPF), leading to stem cell exhaustion. In this review, the large amount of data supporting this pathogenic view are discussed, with emphasis on the possible molecular and cellular mechanisms leading to the severe parenchymal remodeling that characterizes, in different ways, these deadly diseases.

The nuclear effector of Wnt-signaling, Tcf1, functions as a T-cell-specific tumor suppressor for development of lymphomas

Tcf1 is known to function as a transcriptional activator of Wnt-induced proliferation during T cell development in the thymus. Evidence for an additional contrasting role for Tcf1 as a T-cell specific tumor suppressor gene is now presented.

The HMG-box factor Tcf1 is required during T-cell development in the thymus and mediates the nuclear response to Wnt signals. Tcf1^−/− mice have previously been characterized and show developmental blocks at the CD4−CD8− double negative (DN) to CD4+CD8+ double positive transition. Due to the blocks in T-cell development, Tcf1^−/− mice normally have a very small thymus. Unexpectedly, a large proportion of Tcf1^−/− mice spontaneously develop thymic lymphomas with 50% of mice developing a thymic lymphoma/leukemia at the age of 16 wk. These lymphomas are clonal, highly metastatic, and paradoxically show high Wnt signaling when crossed with Wnt reporter mice and have high expression of Wnt target genes Lef1 and Axin2. In wild-type thymocytes, Tcf1 is higher expressed than Lef1, with a predominance of Wnt inhibitory isoforms. Loss of Tcf1 as repressor of Lef1 leads to high Wnt activity and is the initiating event in lymphoma development, which is exacerbated by activating Notch1 mutations. Thus, Notch1 and loss of Tcf1 functionally act as collaborating oncogenic events. Tcf1 deficiency predisposes to the development of thymic lymphomas by ectopic up-regulation of Lef1 due to lack of Tcf1 repressive isoforms and frequently by cooperating activating mutations in Notch1. Tcf1 therefore functions as a T-cell–specific tumor suppressor gene, besides its established role as a Wnt responsive transcription factor. Thus, Tcf1 acts as a molecular switch between proliferative and repressive signals during T-lymphocyte development in the thymus.

Cancers often develop as a consequence of deregulated expression of key factors that operate during normal development. T-cell factor 1 (Tcf1) has an established role in the nuclear response to Wnt signaling during normal T-cell development in the thymus. Here we show in mice that the absence of Tcf1 can trigger tumorigenesis. As expected from previous work, lack of Tcf1 results in a small thymus with several partial blocks in T-cell development in the thymus. Surprisingly, we observe that a large proportion of Tcf1^−/− mice spontaneously develop thymic lymphomas. Thorough investigation of these thymic-derived tumors revealed that the mechanism underlying these lymphomas is, paradoxically, increased levels of Wnt-signaling. We propose that Wnt-signaling in these tumors is mediated by up-regulated expression of the Tcf1-homologue, Lef1, and specifically its long isoform. Furthermore, we have evidence to propose that in a normal thymus, short isoforms of Tcf1 that cannot respond to Wnt signals act as repressors of Lef1-mediated Wnt-signaling. Thus, we propose that Tcf1 has a dual function developing T cells in mice: it functions as a T-cell–specific tumor suppressor gene in addition to its established role as a transcriptional activator of Wnt-induced proliferation. Whether loss of function of Tcf-1 as a tumor suppressor gene actually occurs in human T-cell lymphoblastic leukemias is currently under investigation.