LIF mediates proinvasive activation of stromal fibroblasts in cancer

Capturing tumor complexity in vitro: Comparative analysis of 2D and 3D tumor models for drug discovery

Two-dimensional (2D) cell cultures growing on plastic do not recapitulate the three dimensional (3D) architecture and complexity of human tumors. More representative models are required for drug discovery and validation. Here, 2D culture and 3D mono- and stromal co-culture models of increasing complexity have been established and cross-comparisons made using three standard cell carcinoma lines: MCF7, LNCaP, NCI-H1437. Fluorescence-based growth curves, 3D image analysis, immunohistochemistry and treatment responses showed that end points differed according to cell type, stromal co-culture and culture format. The adaptable methodologies described here should guide the choice of appropriate simple and complex in vitro models.

Progress toward Treatment and Cure of Epidermolysis Bullosa: Summary of the DEBRA International Research Symposium EB2015

Epidermolysis bullosa (EB), a group of complex heritable blistering diseases, is the topic of triennial research meetings organized by DEBRA International, the umbrella of patient advocacy organizations. The DEBRA 2015 Research Conference, held in May 2015, brought together investigators and clinicians from around the world working at the forefront of EB research. Discussing the state-of-the-art approaches from a wide range of disciplines, there was a palpable excitement at this conference brought about by the optimism about applying new sequencing techniques, genome editing, protein replacement, autologous and allogeneic stem cell therapy, innovations in cancer biology, revertant mosaicism and iPSC techniques, all of which are aimed at developing new therapies for EB. Many in the field who have participated in EB research for many years were especially enthusiastic and felt that, possibly for the first time, the field seems uniquely poised to bring these new tools to effectively tackle EB using multiple complementary approaches towards improved quality of life and eventually a cure for patients suffering from EB, a currently intractable disease.

Mechano-reciprocity is maintained between physiological boundaries by tuning signal flux through the Rho-associated protein kinase

The mechanical properties of the ECM strongly influence the behavior of all cell types within a given tissue. Increased matrix tension promotes epithelial cell proliferation by engaging mitogenic mechanotransduction signaling including the Salvador/Warts/Hippo, PI 3-kinase, Rho, Wnt and MAP kinase pathways. The Rho signaling pathways in particular are capable of increasing intra-cellular tension by elevating the production and contractility of the actomyosin cytoskeleton, which counteracts tension changes within the matrix in a process termed mechano-reciprocity. We have discovered that Rho-ROCK signaling increases the production of ECM through paracrine signaling between the epithelium and fibroblasts and also the remodeling of the ECM by regulating focal adhesion dynamics in fibroblasts. These two phenomena together cause increased ECM tension. Enhanced mechano-reciprocity results in ever-increasing intra- and extra-cellular tension in a vicious cycle that promotes cell proliferation and tumor progression. These insights reveal that inhibiting mechano-reciprocity, reducing ECM tension and targeting cancer-associated fibroblasts in a coordinated fashion has potential as cancer therapy.

Rho, ROCK and actomyosin contractility in metastasis as drug targets

Metastasis is the spread of cancer cells around the body and the cause of the majority of cancer deaths. Metastasis is a very complex process in which cancer cells need to dramatically modify their cytoskeleton and cope with different environments to successfully colonize a secondary organ. In this review, we discuss recent findings pointing at Rho-ROCK or actomyosin force (or both) as major drivers of many of the steps required for metastatic success. We propose that these are important drug targets that need to be considered in the clinic to palliate metastatic disease.

Epigenetic switch drives the conversion of fibroblasts into proinvasive cancer-associated fibroblasts

Carcinoma-associated fibroblasts (CAF) mediate the onset of a proinvasive tumour microenvironment. The proinflammatory cytokine LIF reprograms fibroblasts into a proinvasive phenotype, which promotes extracellular matrix remodelling and collective invasion of cancer cells. Here we unveil that exposure to LIF initiates an epigenetic switch leading to the constitutive activation of JAK1/STAT3 signalling, which results in sustained proinvasive activity of CAF. Mechanistically, p300-histone acetyltransferase acetylates STAT3, which, in turn, upregulates and activates the DNMT3b DNA methyltransferase. DNMT3b methylates CpG sites of the SHP-1 phosphatase promoter, which abrogates SHP-1 expression, and results in constitutive phosphorylation of JAK1. Sustained JAK1/STAT3 signalling is maintained by DNA methyltransferase DNMT1. Consistently, in human lung and head and neck carcinomas, STAT3 acetylation and phosphorylation are inversely correlated with SHP-1 expression. Combined inhibition of DNMT activities and JAK signalling, in vitro and in vivo, results in long-term reversion of CAF-associated proinvasive activity and restoration of the wild-type fibroblast phenotype.

Carcinoma-associated fibroblasts are key components of solid tumours and associated with poor clinical outcome. Here the authors show that the cytokine LIF initiates an epigenetic switch which results in the sustained invasive activity of the tumour cells.

HIF-2α mediates hypoxia-induced LIF expression in human colorectal cancer cells

Leukemia inhibitory factor (LIF), a multi-functional cytokine, has a complex role in cancer. While LIF induces the differentiation of several myeloid leukemia cells and inhibits their growth, it also promotes tumor progression, metastasis and chemoresistance in many solid tumors. LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients. Currently, the mechanism for LIF overexpression in tumor cells is not well-understood. Here, we report that hypoxia, a hallmark of solid tumors, induced LIF mRNA expression in human colorectal cancer cells. Analysis of LIF promoter revealed several hypoxia-responsive elements (HREs) that can specifically interact with and be transactivated by HIF-2α but not HIF-1α. Consistently, ectopic expression of HIF-2α but not HIF-1α transcriptionally induced LIF expression levels in cells. Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells. Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens. In summary, results from this study demonstrate that hypoxia induces LIF expression in human cancer cells mainly through HIF-2α, which could be an important underlying mechanism for LIF overexpression in human cancers.

The regulation of leukemia inhibitory factor

Leukemia inhibitory factor (LIF), a secreted cytokine, plays an important role in a wide array of biological processes including inducing differentiation of leukemia cell, inflammatory response, neuronal development, embryonic implantation, stem cell self-renewal and cancer progression, etc. LIF exerts its biological functions mainly through the activation and regulation of JAK/STAT3, AKT, EKR1/2 and mTOR signal pathways. The expression levels of LIF are regulated by many different factors under different conditions in different tissue/cell types. For example, estrogen and p53 are important regulators for the high LIF production in uterine tissues at the implantation stage. Hypoxia plays a critical role in LIF overexpression in solid tumors. Many cytokines, including IL-6, IL-1β, can also induce the LIF expression and production. In this review, we summarize the current understanding on the transcriptional regulation of LIF under various conditions.

Microenvironment, tumor cell plasticity, and cancer

PURPOSE OF REVIEW

Much effort has been devoted to determining how cellular and noncellular components of the tumoral niche initiate and promote cancer development. Cancer cells perceive biochemical signals from components of the extracellular matrix (ECM) and sense physical features, such as matrix stiffness and cell confinement. The past decade has seen a better understanding of the biophysics and mechanobiology associated with cancer cells. Indeed, loss of mechanisms controlling the production, the degradation, and the remodeling of ECM contributes to tumor growth or cell dissemination by affecting cell contractility in response to ECM stiffness and by stimulating mechanical dependence of growth factor activation.

RESULTS

Cell plasticity allows adaptative strategies for cancer cells to survive or eventually escape from tumoral environment through modification of the microenvironment-cell interface, internal tension increase, and nuclear deformation partly leading to intratumoral heterogeneity. However, although alteration of the biomechanical properties of the ECM are sufficient to promote cell migration and invasion in cancer cells, this microenvironment can also provide a hospitable niche for tumor dormancy and resistance to cancer therapy.

CONCLUSION

The review will focus on how physicochemical properties of ECM might promote tumor growth or cell dissemination or on the contrary maintain quiescent state of cancer cells. It is crucial to clarify the molecular basis of mechanotransduction in the development and progression of tumors to identify new potential biomarkers and anticancer therapeutic targets.

Single cell migration in oral squamous cell carcinoma - possible evidence of epithelial-mesenchymal transition in vivo

BACKGROUND

The invasion of cancer cells into the surrounding normal tissue is one of the defining features of cancer. While the phenomena of tumour budding, epithelial-mesenchymal transition and the presence of myofibroblasts have independently been shown to be related to a poor prognosis of oral carcinomas, their relationship has not been examined in detail.

METHODS

Paraffin-embedded tissues from 28 patients with oral squamous cell carcinomas were stained with antibodies to cytokeratin, α-SMA, vimentin, E-cadherin, N-cadherin and Twist and evaluated for their expression in relation to invasive cancer cells and the surrounding tumour stroma.

RESULTS AND CONCLUSIONS

A direct, histological relationship between invading, budding tumour cells and myofibroblasts was occasionally seen but was not a general feature. Most of the budding tumour cells at the invasive front had a decreased expression of E-cadherin, but we did not find that this was associated with a consistent or clear increase in either N-cadherin or vimentin. We therefore suggest that the budding of tumour cells is not dependent upon either myofibroblasts or a complete epithelial-mesenchymal transition and that these phenomena most likely represent separate processes in tumour progression.

Cancer-associated fibroblasts connect metastasis-promoting communication in colorectal cancer

Colorectal cancer (CRC) progression and eventually metastasis is directed in many aspects by a circuitous ecosystem consisting of an extracellular matrix scaffold populated by cancer-associated fibroblasts (CAFs), endothelial cells, and diverse immune cells. CAFs are recruited from local tissue-resident fibroblasts or pericryptal fibroblasts and distant fibroblast precursors. CAFs are highly abundant in CRC. In this review, we apply the metastasis-promoting communication of colorectal CAFs to 10 cancer hallmarks described by Hanahan and Weinberg. CAFs influence innate and adaptive tumor immune responses. Using datasets from previously published work, we re-explore the potential messages implicated in this process. Fibroblasts present in metastasis (metastasis-associated fibroblasts) from CRC may have other characteristics and functional roles than CAFs in the primary tumor. Since CAFs connect metastasis-promoting communication, CAF markers are potential prognostic biomarkers. CAFs and their products are possible targets for novel therapeutic strategies.

Vemurafenib resistance selects for highly malignant brain and lung-metastasizing melanoma cells

V600E being the most common mutation in BRAF, leads to constitutive activation of the MAPK signaling pathway. The majority of V600E BRAF positive melanoma patients treated with the BRAF inhibitor vemurafenib showed initial good clinical responses but relapsed due to acquired resistance to the drug. The aim of the present study was to identify possible biomarkers associated with the emergence of drug resistant melanoma cells. To this end we analyzed the differential gene expression of vemurafenib-sensitive and vemurafenib resistant brain and lung metastasizing melanoma cells. The major finding of this study is that the in vitro induction of vemurafenib resistance in melanoma cells is associated with an increased malignancy phenotype of these cells. Resistant cells expressed higher levels of genes coding for cancer stem cell markers (JARID1B, CD271 and Fibronectin) as well as genes involved in drug resistance (ABCG2), cell invasion and promotion of metastasis (MMP-1 and MMP-2). We also showed that drug-resistant melanoma cells adhere better to and transmigrate more efficiently through lung endothelial cells than drug-sensitive cells. The former cells also alter their microenvironment in a different manner from that of drug-sensitive cells. Biomarkers and molecular mechanisms associated with drug resistance may serve as targets for therapy of drug-resistant cancer.

Microenvironmental regulation of therapeutic response in cancer

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis but also has profound effects on therapeutic efficacy. In the case of microenvironment-mediated resistance this can involve an intrinsic response, including the co-option of pre-existing structural elements and signaling networks, or an acquired response of the tumor stroma following the therapeutic insult. Alternatively, in other contexts, the TME has a multifaceted ability to enhance therapeutic efficacy. This review examines recent advances in our understanding of the contribution of the TME during cancer therapy and discusses key concepts that may be amenable to therapeutic intervention.