A 79-kb paternally inherited 7q32.2 microdeletion involving MEST in a patient with a Silver-Russell syndrome-like phenotype.

Maternal uniparental disomy of human chromosome 7 [upd(7)mat] is well-characterized as a cause of the growth disorder Silver-Russell syndrome (SRS). However, the causative gene is not currently known. There is growing evidence that molecular changes at the imprinted MEST region in 7q32.2 are associated with a phenotype evocative of SRS. This report details a patient with a SRS-like phenotype and a paternally inherited microdeletion of 79 kilobases (35-fold smaller than the previously reported smallest deletion) in the 7q32.2 region. This microdeletion encompasses only five genes, including MEST, which corroborates the hypothesis that MEST plays a central role in the 7q32.2 microdeletion growth disorder, as well as further implicating MEST in upd(7)mat SRS itself.

Matricellular proteins in cancer: a focus on secreted Frizzled-related proteins.

Tumours are complex entities, wherein cancer cells interact with myriad soluble, insoluble and cell associated factors. These microenvironmental mediators regulate tumour growth, progression and metastasis, and are produced by cancer cells and by stromal components such as fibroblast, adipocytes and immune cells. Through their ability to bind to extracellular matrix proteins, cell surface receptors and growth factors, matricellular proteins enable a dynamic reciprocity between cancer cells and their microenvironment. Hence, matricellular proteins play a critical role in tumour progression by regulating where and when cancer cells are exposed to key growth factors and regulatory proteins. Recent studies suggest that, in addition to altering Wingless (Wnt) signalling, certain members of the Secreted Frizzled Related Protein (sFRP) family are matricellular in nature. In this review, we outline the importance of matricellular proteins in cancer, and discuss how sFRPs may function to both inhibit and promote cancer progression in a context-dependent manner. By considering the matricellular functionality of sFRPs, we may better understand their apparently paradoxical roles in cancers.

A pan-cancer analysis of secreted Frizzled-related proteins: re-examining their proposed tumour suppressive function.

Secreted frizzled-related proteins (SFRPs), containing five family members (SFRPs 1-5) are putative extracellular Wnt inhibitors. Given their abilities to inhibit Wnt signalling, as well as the loss of SFRP1 in many cancers, this family is generally considered to be tumour suppressive. In this study we analyzed gene expression, promoter methylation and survival data from over 8000 tumour and normal samples from 29 cancers in order to map the context-specific associations of SFRPs 1-5 with patient survival, gene silencing and gene expression signatures. We show that only SFRP1 associates consistently with tumour suppressive functions, and that SFRP2 and SFRP4 typically associate with a poor prognosis concomitant with the expression of genes associated with epithelial-to-mesenchymal transition. Moreover, our results indicate that while SFRP1 is lost in cancer cells via the process of DNA methylation, SFRP2 and 4 are likely derived from the tumour stroma, and thus tend to increase in tumours as compared to normal tissues. This in-depth analysis highlights the need to study each SFRP as a separate entity and suggests that SFRP2 and SFRP4 should be approached as complex matricellular proteins with functions that extend far beyond their putative Wnt antagonistic ability.

Investigating the utility of human melanoma cell lines as tumour models.

Melanoma researchers utilize cell lines to model many tumour phenomena. It is thus important to understand similarities and differences between cell lines and the tumours that they represent, so that the optimal models can be chosen to answer specific research questions. Herein, we compared the transcriptomes of 42 melanoma cell lines to hundreds of tumours from The Cancer Genome Atlas and thousands of single melanoma cells. Tumour purity was accounted for using the ESTIMATE algorithm, so that differences likely resulting from non-tumour cells could be accounted for. In addition, UV mutational signatures and the expression of skin-associated genes were analyzed in order to identify the putative origin of various cell lines. We found the transcriptional and mutational characteristics of melanoma cell lines to mirror those of the tumours, with the exception of immune-associated transcripts, which were absent in cell culture. We also determined cell lines that highly or poorly recapitulate melanomas and have identified colon (COLO 741) and lung (COLO 699) cancer cell lines that may actually be melanoma. In summary, this study represents a comprehensive comparison of melanoma cell lines and tumours that can be used as a guide for researchers when selecting melanoma cell line models.

Defining the Na+/H+ exchanger NHE1 interactome in triple-negative breast cancer cells.

Mounting evidence supports a major role for the Na+/H+ exchanger NHE1 in cancer progression and metastasis. NHE1 is hyperactive at the onset of oncogenic transformation, resulting in intracellular alkalinization and extracellular microenvironmental acidification. These conditions promote invasion and facilitate metastasis. However, the signal pathways governing the regulation of exchanger activity are still unclear. This is especially important in the aggressively metastatic, triple-negative basal breast cancer subtype. We used affinity chromatography followed by mass spectrometry to identify novel and putative interaction partners of NHE1 in MDA-MB-231 triple-negative breast cancer cells. NHE1 associated with several types of proteins including cytoskeletal proteins and chaperones. We validated protein interactions by co-immunoprecipitation for: 14-3-3, AKT, α-enolase, CHP1, HSP70 and HSP90. Additionally, we used The Cancer Genome Atlas (TCGA) to study NHE1 gene expression in primary patient breast tumours versus adjacent normal tissue. NHE1 expression was elevated in breast tumour samples and, when broken down by breast cancer subtype, NHE1 gene expression was significantly lower in tumours of the basal subtype compared to luminal and HER2+ subtypes. Reverse phase protein array (RPPA) analysis showed that NHE1 expression positively correlated with p90RSK expression in basal, but not luminal, primary tumours. Other proteins were negatively correlated with NHE1 expression in basal breast cancer tumours. Taken together, our data provides the first insight into the signalling molecules that form the NHE1 interactome in triple-negative breast cancer cells. These results will focus our search for novel targeted therapies.

Assessing breast cancer cell lines as tumour models by comparison of mRNA expression profiles.

INTRODUCTION: Breast cancer researchers use cell lines to model myriad phenomena ranging from DNA repair to cancer stem cell phenotypes. Though appropriate, and even requisite, for many studies, the suitability of cell lines as tumour models has come into question owing to possibilities of tissue culture artefacts and clonal selection. These issues are compounded by the inability of cancer cells grown in isolation to fully model the in situ tumour environment, which also contains a plethora of non-tumour cell types. It is thus important to understand similarities and differences between cancer cell lines and the tumours that they represent so that the optimal tumour models can be chosen to answer specific research questions. METHODS: In the present study, we compared the RNA-sequencing transcriptomes of a collection of breast cancer cell lines to transcriptomes obtained from hundreds of tumours using The Cancer Genome Atlas. Tumour purity was accounted for by analysis of stromal and immune scores using the ESTIMATE algorithm so that differences likely resulting from non-tumour cells could be accounted for. RESULTS: We found the transcriptional characteristics of breast cancer cell lines to mirror those of the tumours. We identified basal and luminal cell lines that are most transcriptionally similar to their respective breast tumours. Our comparison of expression profiles revealed pronounced differences between breast cancer cell lines and tumours, which could largely be attributed to the absence of stromal and immune components in cell culture. A focus on the Wnt pathway revealed the transcriptional downregulation or absence of several secreted Wnt antagonists in culture. Gene set enrichment analysis suggests that cancer cell lines have enhanced proliferation and glycolysis independent of stromal and immune contributions compared with breast cancer cells in situ. CONCLUSIONS: This study demonstrates that many of the differences between breast cancer cell lines and tumours are due to the absence of stromal and immune components in vitro. Hence, extra precautions should be taken when modelling extracellular proteins in vitro. The specific differences discovered emphasize the importance of choosing an appropriate model for each research question.