Fiona Lanigan

Increased claudin-4 expression is associated with poor prognosis and high tumour grade in breast cancer

The role of intercellular tight junctions in breast epithelial cells is traditionally thought to be in maintaining polarity and barrier function. However, claudin‐4, a tight junction protein, is overexpressed in breast tumour cells compared to normal epithelial cells, which generally corresponds to a loss in polarity. The aim of this study was to investigate the distribution and potential clinical value of claudin‐4 in breast cancer, and to evaluate its usefulness as a prognostic and predictive biomarker. Expression of claudin‐4 was initially examined by Western blot analysis in a cohort of 88 breast tumours, and was found to correlate positively with tumour grade and negatively with ER. Claudin‐4 expression was then evaluated by immunohistochemistry in a larger cohort of 299 tumours represented on a tissue microarray. Claudin‐4 expression correlated positively with tumour grade and Her2, and negatively with ER. High claudin‐4 expression was also associated with worse breast cancer‐specific survival (p = 0.003), recurrence‐free survival (p = 0.025) and overall survival (p = 0.034). Multivariate analysis revealed that claudin‐4 independently predicted survival in the entire cohort (HR 1.95; 95%CI 1.01–3.79; p = 0.047) and in the ER positive subgroup treated with adjuvant tamoxifen (HR 4.34; 95%CI 1.14–16.53; p = 0.032). This relationship between increased claudin‐4 expression and adverse outcome was validated at the mRNA level in a DNA microarray dataset of 295 breast tumours. We conclude that high levels of claudin‐4 protein are associated with adverse outcome in breast cancer patients, including the subgroup of patients treated with adjuvant tamoxifen.

Molecular links between mammary gland development and breast cancer.

Abstract.During its lifetime, the mammary gland undergoes many phases of development and differentiation. Much of this occurs during puberty, when the ductal epithelium expands by branching morphogenesis, invading the surrounding fat pad to form an organised mammary tree. Throughout its existence, the epithelium will go through several cycles of proliferation and cell death during pregnancy, lactation and involution. Many of the signalling mechanisms which control the initial invasion of the fat pad by the epithelium, and regulate its continuing plasticity, can be harnessed or corrupted by tumour cells in order to support their aberrant growth and progression towards invasion. This is true not just for the epithelial cells themselves but also for cells in the surrounding microenvironment, including fibroblasts, macrophages and adipocytes. This review examines the complex web of signalling and adhesion interactions controlling branching morphogenesis, and how their alteration can promote malignancy. Current in vivo and in vitro mammary gland models are also discussed. (Part of a Multi-author Review)

Transcriptional regulation of cellular senescence

Cellular senescence is an irreversible arrest of proliferation. It is activated when a cell encounters stress such as DNA damage, telomere shortening or oncogene activation. Like apoptosis, it impedes tumour progression and acts as a barrier that pre-neoplastic cells must overcome during their evolution toward the full tumourigenic state. This review focuses on the role of transcriptional regulators in the control of cellular senescence, explores how their function is perturbed in cancer and discusses the potential to harness this knowledge for future cancer therapies.

Common Molecular Mechanisms of Mammary Gland Development and Breast Cancer

Abstract.During its lifetime, the mammary gland undergoes many phases of development and differentiation. Much of this occurs during puberty, when the ductal epithelium expands by branching morphogenesis, invading the surrounding fat pad to form an organised mammary tree. Throughout its existence, the epithelium will go through several cycles of proliferation and cell death during pregnancy, lactation and involution. Many of the signalling mechanisms which control the initial invasion of the fat pad by the epithelium, and regulate its continuing plasticity, can be harnessed or corrupted by tumour cells in order to support their aberrant growth and progression towards invasion. This is true not just for the epithelial cells themselves but also for cells in the surrounding microenvironment, including fibroblasts, macrophages and adipocytes. This review examines the complex web of signalling and adhesion interactions controlling branching morphogenesis, and how their alteration can promote malignancy. Current in vivo and in vitro mammary gland models are also discussed. (Part of a Multi-author Review)

PKCζ regulates cell polarisation and proliferation restriction during mammary acinus formation

Mammary epithelial cells organize in three dimensions and generate acini when supported on laminin-rich extracellular matrix. Acinus formation begins with the apicobasal polarisation of the outer cells of the assembly and the withdrawal of these cells from the cell cycle. Internal cells then clear out to form a hollow lumen. Here, we show that PKCζ is phosphorylated (at T410) and activated in the early stages of acinus formation in both primary cells and MCF10A cells, and during mammary tree maturation in vivo. Phospho-PKCζ colocalised with tight junction components and bound to the Par polarising complex in developing acini. To further investigate the importance of PKCζ phosphorylation in this context, acinus formation was studied in MCF10A cells overexpressing non-phosphorylatable (T410A) or ‘constitutively phosphorylated’ (T410E) PKCζ. In both cell types, acinus-associated cell polarisation and lumen clearance were compromised, emphasising the importance of regulated phosphorylation of PKCζ at T410 for successful acinus formation. PKCζ can be activated in a phosphorylation (at T410)-dependent and a phosphorylation-independent manner. Cells overexpressing a complete kinase-deficient PKCζ (K281W) displayed a cell polarising deficit, but also generated large ‘multi-acinar’ structures with associated early lumenal cell hyperproliferation. Therefore our data shows, for the first time, that two separable PKCζ activities (one phosphorylation-dependent, the other not) are required to support the cell polarisation and proliferation restriction that underpins successful acinus formation. Paralleling these contributions, we found that low levels of PKCζ mRNA expression are associated with more ‘poorly differentiated’ tumours and a poor outcome in a cohort of 295 breast cancer patients.

The emerging role of FK506-binding proteins as cancer biomarkers: a focus on FKBPL

FKBPs (FK506-binding proteins) have long been recognized as key regulators of the response to immunosuppressant drugs and as co-chaperones of steroid receptor complexes. More recently, evidence has emerged suggesting that this diverse protein family may also represent cancer biomarkers owing to their roles in cancer progression and response to treatment. FKBPL (FKBP-like) is a novel FKBP with roles in GR (glucocorticoid receptor), AR (androgen receptor) and ER (oestrogen receptor) signalling. FKBPL binds Hsp90 (heat-shock protein 90) and modulates translocation, transcriptional activation and phosphorylation of these steroid receptors. It has been proposed as a novel prognostic and predictive biomarker, where high levels predict for increased recurrence-free survival in breast cancer patients and enhanced sensitivity to endocrine therapy. Since this protein family has roles in a plethora of signalling pathways, its members represent novel prognostic markers and therapeutic targets for cancer diagnosis and treatment.

Functional and prognostic relevance of the homeobox protein MSX2 in malignant melanoma

Background:The homeobox containing transcription factor MSX2 is a key regulator of embryonic development and has been implicated to have a role in breast and pancreatic cancer.Methods:Using a selection of two- and three-dimensional in vitro assays and tissue microarrays (TMAs), the clinical and functional relevance of MSX2 in malignant melanoma was explored. A doxycyline-inducible over-expression system was applied to study the relevance of MSX2 in vitro. For TMA construction, tumour material from 218 melanoma patients was used.Results:Ectopic expression of MSX2 resulted in the induction of apoptosis and reduced the invasive capacity of melanoma cells in three-dimensional culture. MSX2 over-expression was shown to affect several signalling pathways associated with cell invasion and survival. Downregulation of N-Cadherin, induction of p21 and inhibition of both BCL2 and Survivin were observed. Cytoplasmic MSX2 expression was found to correlate significantly with increased recurrence-free survival (P=0.008). Nuclear expression of MSX2 did not result in significant survival correlations, suggesting that the beneficial effect of MSX2 may be independent of its DNA binding activity.Conclusions:MSX2 may be an important regulator of melanoma cell invasion and survival. Cytoplasmic expression of the protein was identified as biomarker for good prognosis in malignant melanoma patients.

Master Transcriptional Regulators in Cancer: Discovery via Reverse Engineering Approaches and Subsequent Validation

Reverse engineering of transcriptional networks using gene expression data enables identification of genes that underpin the development and progression of different cancers. Methods to this end have been available for over a decade and, with a critical mass of transcriptomic data in the oncology arena having been reached, they are ever more applicable. Extensive and complex networks can be distilled into a small set of key master transcriptional regulators (MTR), genes that are very highly connected and have been shown to be involved in processes of known importance in disease. Interpreting and validating the results of standardized bioinformatic methods is of crucial importance in determining the inherent value of MTRs. In this review, we briefly describe how MTRs are identified and focus on providing an overview of how MTRs can and have been validated for use in clinical decision making in malignant diseases, along with serving as tractable therapeutic targets. Cancer Res; 77(9); 2186-90. ©2017 AACR.

Delineating transcriptional networks of prognostic gene signatures refines treatment recommendations for lymph node-negative breast cancer patients

The majority of women diagnosed with lymph node‐negative breast cancer are unnecessarily treated with damaging chemotherapeutics after surgical resection. This highlights the importance of understanding and more accurately predicting patient prognosis. In the present study, we define the transcriptional networks regulating well‐established prognostic gene expression signatures. We find that the same set of transcriptional regulators consistently lie upstream of both ‘prognosis’ and ‘proliferation’ gene signatures, suggesting that a central transcriptional network underpins a shared phenotype within these signatures. Strikingly, the master transcriptional regulators within this network predict recurrence risk for lymph node‐negative breast cancer better than currently used multigene prognostic assays, particularly in estrogen receptor‐positive patients. Simultaneous examination of p16INK4A expression, which predicts tumours that have bypassed cellular senescence, revealed that intermediate levels of p16INK4A correlate with an intact pRB pathway and improved survival. A combination of these master transcriptional regulators and p16INK4A, termed the OncoMasTR score, stratifies tumours based on their proliferative and senescence capacity, facilitating a clearer delineation of lymph node‐negative breast cancer patients at high risk of recurrence, and thus requiring chemotherapy. Furthermore, OncoMasTR accurately classifies over 60% of patients as ‘low risk’, an improvement on existing prognostic assays, which has the potential to reduce overtreatment in early‐stage patients. Taken together, the present study provides new insights into the transcriptional regulation of cellular proliferation in breast cancer and provides an opportunity to enhance and streamline methods of predicting breast cancer prognosis.

Common Molecular Mechanisms of Mammary Gland Development and Breast Cancer: Molecular links between mammary gland development and breast cancer

Abstract.During its lifetime, the mammary gland undergoes many phases of development and differentiation. Much of this occurs during puberty, when the ductal epithelium expands by branching morphogenesis, invading the surrounding fat pad to form an organised mammary tree. Throughout its existence, the epithelium will go through several cycles of proliferation and cell death during pregnancy, lactation and involution. Many of the signalling mechanisms which control the initial invasion of the fat pad by the epithelium, and regulate its continuing plasticity, can be harnessed or corrupted by tumour cells in order to support their aberrant growth and progression towards invasion. This is true not just for the epithelial cells themselves but also for cells in the surrounding microenvironment, including fibroblasts, macrophages and adipocytes. This review examines the complex web of signalling and adhesion interactions controlling branching morphogenesis, and how their alteration can promote malignancy. Current in vivo and in vitro mammary gland models are also discussed. (Part of a Multi-author Review)