Attenuated transforming growth factor beta signaling promotes metastasis in a model of HER2 mammary carcinogenesis

Dynamic extracellular matrix stiffening induces a phenotypic transformation and a migratory shift in epithelial cells

Soft tissue tumors, including breast cancer, become stiffer throughout disease progression. This increase in stiffness has been shown to correlate to malignant phenotype and epithelial-to-mesenchymal transition (EMT) in vitro. Unlike current models, utilizing static increases in matrix stiffness, our group has previously created a system that allows for dynamic stiffening of an alginate-matrigel composite hydrogel to mirror the native dynamic process. Here, we utilize this system to evaluate the role of matrix stiffness on EMT and metastasis both in vitro and in vivo. Epithelial cells were seen to lose normal morphology and become protrusive and migratory after stiffening. This shift corresponded to a loss of epithelial markers and gain of mesenchymal markers in both the cell clusters and migrated cells. Furthermore, stiffening in a murine model reduced tumor burden and increased migratory behavior prior to tumor formation. Inhibition of FAK and PI3K in vitro abrogated the morphologic and migratory transformation of epithelial cell clusters. This work demonstrates the key role extracellular matrix stiffening has in tumor progression through integrin signaling and, in particular, its ability to drive EMT-related changes and metastasis.

Adenosine/TGFβ axis in regulation of mammary fibroblast functions

Cancer associated fibroblasts (CAF) play a key role in cancer progression and metastasis. Diminished TGFβ response on CAF correlates with poor outcome and recurrence in cancer patients. Mechanisms behind lost TGFβ signaling on CAF are poorly understood, but, utilizing MMTV-PyMT mouse model, we have previously demonstrated that in tumor microenvironment myeloid cells, producing adenosine, contribute to downregulated TGFβ signaling on CAFs. In the current work, we performed serial in vitro studies to investigate the role of adenosine/TGFβ axis in mouse mammary fibroblast functions, i.e., proliferation, protein expression, migration, and contractility. We found that adenosine analog NECA diminished TGFβ-induced CCL5 and MMP9 expression. Additionally, we discovered that NECA completely inhibited effect of TGFβ to upregulate αSMA, key protein of cytoskeletal rearrangements, necessary for migration and contractility of fibroblasts. Our results show that TGFβ increases contractility of mouse mammary fibroblasts and human fibroblast cell lines, and NECA attenuates theses effects. Using pharmacological approach and genetically modified animals, we determined that NECA effects on TGFβ pathway occur via A_2A/A_2B adenosine receptor—AC—PKA dependent manner. Using isolated CD11b⁺ cells from tumor tissue of CD73-KO and CD39-KO animals in co-culture experiments with ATP and AMP, we confirmed that myeloid cells can affect functions of mammary fibroblasts through adenosine signaling. Our data suggest a novel mechanism of interaction between adenosine and TGFβ signaling pathways that can impact phenotype of fibroblasts in a tumor microenvironment.

Babao Dan inhibits the migration and invasion of gastric cancer cells by suppressing epithelial-mesenchymal transition through the TGF-β/Smad pathway

OBJECTIVE

To investigate the anti-metastatic effects of Babao Dan (BBD) on gastric cancer (GC) cells (AGS and MGC80-3) and explore the underlying molecular mechanisms by which it inhibits epithelial-mesenchymal transition (EMT).

METHODS

AGS and MGC80-3 cells were treated with BBD. In addition, cells were treated with the EMT inducer transforming growth factor-β1 (TGF-β1). Cell viability was determined using the MTT assay, and the live cell ratio was calculated via cell counting. Cell invasion and migration were evaluated using the Transwell assay. Western blotting was performed to measure the protein expression of EMT biomarkers and related genes.

RESULTS

BBD inhibited the viability, migration, and invasion of AGS and MGC80-3 cells, but it did not reduce the live cell ratio. Furthermore, BBD inhibited the expression of N-cadherin, vimentin, zinc finger E-box binding homeobox (ZEB)1, ZEB2, Twist1, matrix metalloproteinase (MMP)2, MMP9, TGF-β1, and p-Smad2/3, whereas E-cadherin expression was increased in AGS and MGC80-3 cells to different degrees. Using a GC cell model of EMT induced by TGF-β1, we proved that BBD inhibited p-Smad2/3 and N-cadherin expression, cell migration, and cell invasion.

CONCLUSION

BBD suppressed cell migration and invasion by inhibiting TGF-β-induced EMT and inactivating TGF-β/Smad signaling in GC cells.

Myeloid Cell-Derived TGFβ Signaling Regulates ECM Deposition in Mammary Carcinoma via Adenosine-Dependent Mechanisms

TGFβ plays a crucial role in the tumor microenvironment by regulating cell-cell and cell-stroma interactions. We previously demonstrated that TGFβ signaling on myeloid cells regulates expression of CD73, a key enzyme for production of adenosine, a protumorigenic metabolite implicated in regulation of tumor cell behaviors, immune response, and angiogenesis. Here, using an MMTV-PyMT mouse mammary tumor model, we discovered that deletion of TGFβ signaling on myeloid cells (PyMT/TGFβRII^LysM) affects extracellular matrix (ECM) formation in tumor tissue, specifically increasing collagen and decreasing fibronectin deposition. These changes were associated with mitigated tumor growth and reduced metastases. Reduced TGFβ signaling on fibroblasts was associated with their proximity to CD73⁺ myeloid cells in tumor tissue. Consistent with these findings, adenosine significantly downregulated TGFβ signaling on fibroblasts, an effect regulated by A_2A and A_2B adenosine receptors. METABRIC dataset analysis revealed that patients with triple-negative breast cancer and basal type harbored a similar signature of adenosine and ECM profiles; high expression of A_2B adenosine receptors correlated with decreased expression of Col1 and was associated with poor outcome. Taken together, our studies reveal a new role for TGFβ signaling on myeloid cells in tumorigenesis. This discovered cross-talk between TGFβ/CD73 on myeloid cells and TGFβ signaling on fibroblasts can contribute to ECM remodeling and protumorigenic actions of cancer-associated fibroblasts. SIGNIFICANCE: TGFβ signaling on fibroblasts is decreased in breast cancer, correlates with poor prognosis, and appears to be driven by adenosine that accelerates tumor progression and metastasis via ECM remodeling.

TGF-β-SMAD-miR-520e axis regulates NSCLC metastasis through a TGFBR2-mediated negative-feedback loop

Transforming growth factor-β (TGF-β) pathway plays crucial roles during the carcinogenesis and metastasis. TGF-β receptor 2 (TGFBR2) is a key molecule for the regulation of TGF-β pathway and frequently downregulated or lost in several cancer types including non-small cell lung cancer (NSCLC), and TGF-β pathway is often regulated by negative-feedback mechanisms, but little is known about the mechanism of TGFBR2 downregulation in NSCLC. Here, we found that the expression of miR-520e is upregulated in metastatic tumor tissues compared with non-metastatic ones, and its expression is inversely correlated with that of TGFBR2 in clinical samples. We also discovered that TGF-β dramatically increased the expression of miR-520e, which targeted and downregulated TGFBR2, and the suppression of miR-520e significantly impaired TGF-β-induced TGFBR2 downregulation. Chromatin immunoprecipitation-PCR experiments further showed that miR-520e is transcriptionally induced by SMAD2/3 in response to TGF-β. Our findings reveal a novel negative-feedback mechanism in TGF-β signaling and the expression level of miR-520e could be a predictive biomarker for NSCLC metastasis.

Inflammatory breast cancer cells are characterized by abrogated TGFβ1-dependent cell motility and SMAD3 activity

PURPOSE

Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with elevated metastatic potential, characterized by tumor emboli in dermal and parenchymal lymph vessels. This study has investigated the hypothesis that TGFβ signaling is implicated in the molecular biology of IBC.

METHODS

TGFβ1-induced cell motility and gene expression patterns were investigated in three IBC and three non-IBC (nIBC) cell lines. Tissue samples from IBC and nIBC patients were investigated for the expression of nuclear SMAD2, SMAD3, and SMAD4. SMAD protein levels were related to gene expression data.

RESULTS

TGFβ1-induced cell motility was strongly abrogated in IBC cells (P = 0.003). Genes differentially expressed between IBC and nIBC cells post TGFβ1 exposure revealed attenuated expression of SMAD3 transcriptional regulators, but overexpression of MYC target genes in IBC. IBC patient samples demonstrated a near absence of SMAD3 and -4 expression in the primary tumor compared to nIBC patient samples (P < 0.001) and a further reduction of staining intensity in tumor emboli. Integration of gene and protein expression data revealed that a substantial fraction of the IBC signature genes correlated with SMAD3 and these genes are indicative of attenuated SMAD3 signaling in IBC.

CONCLUSION

We demonstrate attenuated SMAD3 transcriptional activity and SMAD protein expression in IBC, together with obliterated TGFβ1-induced IBC cell motility. The further reduction of nuclear SMAD expression levels in tumor emboli suggests that the activity of these transcription factors is involved in the metastatic dissemination of IBC cells, possibly by enabling collective invasion after partial EMT.

TGF-β signaling in cancer

Signals from the transforming growth factor-β (TGF-β) superfamily mediate a broad spectrum of cellular processes and are deregulated in many diseases, including cancer. TGF-β signaling has dual roles in tumorigenesis. In the early phase of tumorigenesis, TGF-β has tumor suppressive functions, primarily through cell cycle arrest and apoptosis. However, in the late stage of cancer, TGF-β acts as a driver of tumor progression and metastasis by increasing tumor cell invasiveness and migration and promoting chemo-resistance. Here, we briefly review the mechanisms and functions of TGF-β signaling during tumor progression and discuss the therapeutic potentials of targeting the TGF-β pathway in cancer.

An insight into metastasis: Random or evolving paradigms?

Mechanical or fostered molecular events define metastatic cascade. Three distinct sets of molecular events characterize metastasis, viz invasion of extracellular matrix; angiogenesis, vascular dissemination and anoikis resistance; tumor homing and relocation of tumor cells to selective organ. Invasion of extracellular matrix requires epithelial to mesenchymal transition through disrupted lamellopodia formation and contraction of actin cytoskeleton; aberration of Focal adhesion complex formation involving integrins and the extracellular matrix; degradation of extracellular matrix by matrix metalloproteases; faulty immune surveillance in tumor microenvironment and an upregulated proton efflux pump NHE1 in tumors. Vascular dissemination and anoikis resistance depend upon upregulation of integrins, phosphorylation of CDCP1, attenuated apoptotic pathways and upregulation of angiogenesis. Tumor homing depends on recruitment of mesenchymal stem cells, expression on chemokines and growth factors, upregulated stem cell renewal pathways. Despite of many potential challenges in curbing metastasis, future targeted therapies involving immunotherapy, stem cell engineered and oncolytic virus based therapy, pharmacological activation of circadian clock are held promising. To sum up, metastasis is a complex cascade of events and warrants detailed molecular understanding for development of therapeutic strategies.

Next-generation sequencing of idiopathic multicentric and unicentric Castleman disease and follicular dendritic cell sarcomas

Castleman disease (CD) is a rare lymphoproliferative disorder subclassified as unicentric CD (UCD) or multicentric CD (MCD) based on clinical features and the distribution of enlarged lymph nodes with characteristic histopathology. MCD can be further subtyped based on human herpes virus 8 (HHV8) infection into HHV8-associated MCD, HHV8-/idiopathic MCD (iMCD), and polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin change (POEMS)-associated MCD. In a subset of cases of UCD, an associated follicular dendritic cell sarcoma (FDCS) may be seen. Although numerous reports of the clinical and histologic features of UCD, MCD, and FDCS exist, an understanding of the genetic and epigenetic landscape of these rare diseases is lacking. Given this paucity of knowledge, we analyzed 15 cases of UCD and 3 cases of iMCD by targeted next-generation sequencing (NGS; 405 genes) and 3 cases of FDCS associated with UCD hyaline vascular variant (UCD-HVV) by whole-exome sequencing. Common amplifications of ETS1, PTPN6, and TGFBR2 were seen in 1 iMCD and 1 UCD case; the iMCD case also had a somatic DNMT3A L295Q mutation. This iMCD patient also showed clinicopathologic features consistent with a specific subtype known as Castleman-Kojima disease (thrombocytopenia, anasarca, fever, reticulin fibrosis, and organomegaly [TAFRO] clinical subtype). Additionally, 1 case of UCD-HVV showed amplification of the cluster of histone genes on chromosome 6p. FDCS associated with UCD-HVV showed mutations and copy number changes in known oncogenes, tumor suppressors, and chromatin structural-remodeling proteins.

Immunological hallmarks of cis-DDP-resistant Lewis lung carcinoma cells

PURPOSE

Tumor cell resistance to platinum-based chemotherapeutic agents is one of the major hurdles to successful cancer treatment with these drugs, and is associated with alterations in tumor cell immune evasion and immunomodulatory properties. Immunocyte targeting is considered as a relevant approach to fight drug-resistant cancer. In this study, immunological hallmarks of cis-DDP-resistant Lewis lung carcinoma cells (LLC/R9) were investigated.

METHODS

Immunological features of LLC/R9 cells cultured in vitro in normoxic and hypoxic conditions as well as of those that were grown in vivo were examined. The expression of immunologically relevant genes was evaluated by RT-PCR. Tumor cell susceptibility to the macrophage contact tumoricidal activity and NK-mediated cytolysis was investigated in MTT test. TNF-α-mediated tumor cell apoptosis as well as macrophage phagocytosis, oxidative metabolism, and CD206 expression after the treatment with conditioned media from normoxic and hypoxic tumor cells were studied by flow cytometry. Flow cytometry was also used to characterize dendritic cell maturity.

RESULTS

When growing in vitro, LLC/R9 were characterized by slightly increased immunosuppressive cytokine gene expression. Transition to in vivo growth was associated with the enhancement of transcription of these genes in tumor cells. LLC/R9 cells had lowered sensitivity to contact-dependent macrophage-mediated cytotoxicity and to the TNFα-mediated apoptosis in vitro. Conditioned media from hypoxic LLC/R9 cells stimulated reactive oxygen species generation and CD206 expression in non-sensitized macrophages. Acquisition of drug resistance by LLC/R9 cells was associated with their increased sensitivity to NK-cell-mediated cytolysis. Meanwhile, the treatment of LLCR/9-bearing animals with generated ex vivo and loaded with LLC/R9 cell-lysate dendritic cells (DCs) resulted in profoundly enhanced tumor metastasizing.

CONCLUSION

Decreased sensitivity to macrophage cytolysis, polarizing effect on DCs maturation along with increased susceptibility to NK-cell cytotoxic action promote extensive local growth of chemoresistant LLC/R9 tumors in vivo, but hamper their metastasizing.

TGF-β Family Signaling in Tumor Suppression and Cancer Progression

Transforming growth factor-β (TGF-β) induces a pleiotropic pathway that is modulated by the cellular context and its integration with other signaling pathways. In cancer, the pleiotropic reaction to TGF-β leads to a diverse and varied set of gene responses that range from cytostatic and apoptotic tumor-suppressive ones in early stage tumors, to proliferative, invasive, angiogenic, and oncogenic ones in advanced cancer. Here, we review the knowledge accumulated about the molecular mechanisms involved in the dual response to TGF-β in cancer, and how tumor cells evolve to evade the tumor-suppressive responses of this signaling pathway and then hijack the signal, converting it into an oncogenic factor. Only through the detailed study of this complexity can the suitability of the TGF-β pathway as a therapeutic target against cancer be evaluated.

The regulation of pre-metastatic niche formation by neutrophils

Metastasis is a multistep process requiring tumor cell detachment from the primary tumor and migration to target organs through the lymphatic or blood circulatory systems. Specific organs are predisposed to metastases in certain cancers and the formation of supportive metastatic microenvironment determines tumor cell homing. Such an environment is provided by a pre-metastatic niche that is formed through the recruitment of bone marrow-derived myeloid cells, however the mechanisms of its formation are not fully understood. Recent evidence suggests that the primary tumor itself modulates the environment of secondary organs prior to tumor cell dissemination. The contribution of neutrophils to the formation of the pre-metastatic niche is getting growing attention. Obviously, neutrophils can affect the development of metastasis in two contradicting ways, by either stimulation or inhibition of this process, depending on the activation status. Pro-tumor neutrophils actively support metastasis formation by different mechanisms, including the formation of pre-metastatic niche, tumor cell attraction, and the direct support of tumor cell proliferation. Moreover, suppressive neutrophils, which are the granulocytic arm of MDSC, promote tumor progression by dampening anti-tumor T cell immunity. On the other hand, anti-tumor neutrophils can inhibit metastasis formation by the cytotoxicity towards tumor cells in the circulation or at the pre-metastatic site, and even via stimulation of T cell proliferation. Apparently, the regulation of the pro- or anti-tumor neutrophil properties has significant implications on metastatic spread in the host. Here we provide an up to date overview of the different roles neutrophils play in regulating the metastatic processes.

From General Aberrant Alternative Splicing in Cancers and Its Therapeutic Application to the Discovery of an Oncogenic DMTF1 Isoform

Alternative pre-mRNA splicing is a crucial process that allows the generation of diversified RNA and protein products from a multi-exon gene. In tumor cells, this mechanism can facilitate cancer development and progression through both creating oncogenic isoforms and reducing the expression of normal or controllable protein species. We recently demonstrated that an alternative cyclin D-binding myb-like transcription factor 1 (DMTF1) pre-mRNA splicing isoform, DMTF1β, is increasingly expressed in breast cancer and promotes mammary tumorigenesis in a transgenic mouse model. Aberrant pre-mRNA splicing is a typical event occurring for many cancer-related functional proteins. In this review, we introduce general aberrant pre-mRNA splicing in cancers and discuss its therapeutic application using our recent discovery of the oncogenic DMTF1 isoform as an example. We also summarize new insights in designing novel targeting strategies of cancer therapies based on the understanding of deregulated pre-mRNA splicing mechanisms.

Stromal Modulators of TGF-β in Cancer

Transforming growth factor-β (TGF-β) is an intriguing cytokine exhibiting dual activities in malignant disease. It is an important mediator of cancer invasion, metastasis and angiogenesis, on the one hand, while it exhibits anti-tumor functions on the other hand. Elucidating the precise role of TGF-β in malignant development and progression requires a better understanding of the molecular mechanisms involved in its tumor suppressor to tumor promoter switch. One important aspect of TGF-β function is its interaction with proteins within the tumor microenvironment. Several stromal proteins have the natural ability to interact and modulate TGF-β function. Understanding the complex interplay between the TGF-β signaling network and these stromal proteins may provide greater insight into the development of novel therapeutic strategies that target the TGF-β axis. The present review highlights our present understanding of how stroma modulates TGF-β activity in human cancers.

Switching Roles of TGF-β in Cancer Development: Implications for Therapeutic Target and Biomarker Studies

TGF-β induces complicated and even opposite responses in numerous biological processes, e.g., tumor suppression in pre-malignant cells and metastasis promotion in cancer cells. However, the cellular contextual determinants of these different TGF-β roles remain elusive, and the driver genes triggering the determinants’ changes have not been identified. Recently, however, several findings have provided new insights on the contextual determinants of Smads in TGF-β’s biological processes. These novel switches and their effectors may serve as prognostic biomarkers and therapeutic targets of TGF-β-mediated cancer progression.

An In Vivo Gain-of-Function Screen Identifies the Williams-Beuren Syndrome Gene GTF2IRD1 as a Mammary Tumor Promoter

The broad implementation of precision medicine in cancer is impeded by the lack of a complete inventory of the genes involved in tumorigenesis. We performed in vivo screening of ∼1,000 genes that are associated with signaling for positive roles in breast cancer, using lentiviral expression vectors in primary MMTV-ErbB2 mammary tissue. Gain of function of five genes, including RET, GTF2IRD1, ADORA1, LARS2, and DPP8, significantly promoted mammary tumor growth. We further studied one tumor-promoting gene, the transcription factor GTF2IRD1. The mis-regulation of genes downstream of GTF2IRD1, including TβR2 and BMPR1b, also individually promoted mammary cancer development, and silencing of TβR2 suppressed GTF2IRD1-driven tumor promotion. In addition, GTF2IRD1 is highly expressed in human breast tumors, correlating with high tumor grades and poor prognosis. Our in vivo approach is readily expandable to whole-genome annotation of tumor-promoting genes.

Expression of CDKN1A/p21 and TGFBR2 in breast cancer and their prognostic significance

BACKGROUND

A new diagnostic and prognostic biomarker may be of value in cancer diseases. Our study aimed to evaluate the CDKN1A/p21 and TGFBR2 level measurable in a cohort of patients with breast cancer after mastectomy, and to confirm their suitability to serve as prognostic biomarkers of the cancer.

METHODS

The expression levels of CDKN1A/p21 and TGFBR2 were detected by reverse transcription-PCR (RT-PCR), western blot assay and immunohistochemical staining for 65 primary tumor samples and paired adjacent noncancerous breast tissues. Their relations to clinicopathologic parameters and to the prognosis of patients with breast cancer were analyzed.

RESULTS

We found the mRNA and protein expression levels of CDKN1A/p21 were significantly upregulated in breast cancer tissues compared with adjacent nontumorous breast tissues. Increased CDKN1A/p21 expression showed a significant correlation with larger tumor size (P=0.014), higher tumor dedifferentiation grade (P=0.021), lymph node metastasis (P=0.019) and a shorter disease-free survival (P=0.044). Contrarily, the expression levels of TGFBR2 mRNA and protein were significantly decreased in breast cancer tissues compared with adjacent nontumorous breast tissues. Underexpression of TGFBR2 in breast cancer was correlated with larger tumor size (P=0.034), lymph node metastasis (P=0.039) and a shorter disease-free survival (P=0.035). Statistical analysis suggested that there was no significant association between CDKN1A/p21 and TGFBR2 expression.

CONCLUSIONS

in summary, our results suggested that high CDKN1A/p21 and low TGFBR2 expression was closely correlated with adverse pathological parameters and poor prognosis in breast cancer. Both CDKN1A/p21 and TGFBR2 are presented as possible candidates for breast cancer biomarkers.

Primary breast cancer induces pulmonary vascular hyperpermeability and promotes metastasis via the VEGF-PKC pathway

The lung is one of the most frequent target organs for breast cancer metastasis. When breast cancer cells from a primary tumor do not colonize the lung, which we named the premetastatic phase, the microenvironment of the lung has already been influenced by the primary tumor. However, little is known about the exact premetastatic alteration and regulatory mechanisms of the lung. Here, we used 4T1 cells (a mouse breast cancer cell line which can specifically metastasize to the lung) to build a mouse breast cancer model. We found that primary breast tumor induced increased pulmonary vascular permeability in the premetastatic phase, which facilitated the leakage of rhodamine-dextran and the extravasation of intravenous therapy injected cancer cells. Furthermore, tight junctions (TJs) were disrupted, and the expression of zonula occludens-1(ZO-1), one of the most important components of tight junctions, was decreased in the premetastatic lung. In addition, elevated serum vascular endothelial growth factor (VEGF) was involved in the destabilization of tight junctions and the VEGF antagonist bevacizumab reversed the primary tumor-induced vascular hyperpermeability. Moreover, activation of the protein kinase C (PKC) pathway disrupted the integrity of TJs and accordingly, the disruption could be alleviated by blocking VEGF. Taken together, these data demonstrate that primary breast cancer may induce tight junction disruptions in the premetastatic lung via the VEGF-PKC pathway and promote pulmonary vascular hyperpermeability before metastasis. © 2015 Wiley Periodicals, Inc.

The global effect of heat on gene expression in cultured bovine mammary epithelial cells

Heat stress (HS) in hot climates is a major cause that strongly negatively affects milk yield in dairy cattle, leading to immeasurable economic loss. The heat stress response of bovine mammary epithelial cells (BMECs) is one component of the acute systemic response to HS. Gene networks of BMECs respond to environmental heat loads with both intra- and extracellular signals that coordinate cellular and whole-animal metabolism. Our experimental objective was to characterize the direct effects of heat stress on the cultured bovine mammary epithelial cells by microarray analyses. The data identified 2716 differentially expressed genes in 43,000 transcripts which were changed significantly between heat-stressed and normal bovine mammary epithelial cells (fold change ≥2, P ≤ 0.001). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these differentially expressed genes are involved in different pathways that regulate cytoskeleton, cell cycle, and stress response processes. Our study provides an overview of gene expression profile and the interaction between gene expression and heat stress, which will lead to further understanding of the potential effects of heat stress on bovine mammary glands.