HER2-PI9 and HER2-I12: two novel and functionally active splice variants of the oncogene HER2 in breast cancer.

In this study, two novel alternative splice variants of HER2, named HER2-PI9 and HER2-I12, were identified in breast cancer cell lines and breast tumour tissues. Whilst HER2-P19 arises from the inclusion of an 117 bp cassette-exon of intron 9 of HER2, HER2-I12 results from intron 12 inclusion. In silico analyses were performed to predict the amino acid sequences of these two HER2 novel variants.

HER2 splice variants in breast cancer: investigating their impact on diagnosis and treatment outcomes.

Overexpression of the HER2 receptor occurs in approximately 20% of breast cancer patients. HER2 positivity is associated with poor prognosis and aggressive tumour phenotypes, which led to rapid progress in HER2 targeted therapeutics and diagnostic testing. Whilst these advances have greatly increased patients' chances of survival, resistance to HER2 targeted therapies, be that intrinsic or acquired, remains a problem.

Regulation of Mcl-1 alternative splicing by hnRNP F, H1 and K in breast cancer cells.

Myeloid cell leukemia-1 (Mcl -1) is one of the most frequently amplified genes in cancer, and its overexpression is associated with poor prognosis and drug resistance. As a member of the Bcl-2 family it is involved in the control of the mitochondrial (intrinsic) cell death pathway. Alternative splicing of the (Mcl-1) gene results in the expression of two functionally distinct proteins, the anti-apoptotic Mcl-1 (exon 2 included) and the pro-apoptotic Mcl-1 (exon 2 skipped).

How is Herstatin, a tumor suppressor splice variant of the oncogene HER2, regulated?

The human epidermal growth factor receptor 2 (HER2)/receptor tyrosine-protein kinasebB-2 (ERBB2) is overexpressed in 20-30% of breast tumors leading to faster growing and more aggressive tumors. Alternative splicing generates a functionally distinct HER2 variant called Herstatin, which is produced by the inclusion of intron 8. Herstatin acts as a tumor suppressor by effectively blocking HER2 activity and cell proliferation, while promoting apoptosis.

SRSF3 and hnRNP H1 regulate a splicing hotspot of HER2 in breast cancer cells.

Overexpression of the oncogene HER2 occurs in 20-30% of invasive breast cancer and is associated with poor prognosis. A number of different splice variants of HER2 have been identified which produce functionally different proteins. Previously these splice variants have been investigated separately, but in the present study we collectively look at the expression and regulation of a group of HER2 splice variants produced by a splicing hotspot.

Unravelling the RNA-Binding Properties of SAFB Proteins in Breast Cancer Cells.

Scaffold attachment factor B1 (SAFB1) and SAFB2 proteins are oestrogen (ER) corepressors that bind to and modulate ER activity through chromatin remodelling or interaction with the basal transcription machinery. SAFB proteins also have an internal RNA-recognition motif but little is known about the RNA-binding properties of SAFB1 or SAFB2. We utilised crosslinking and immunoprecipitation (iCLIP) coupled with high-throughput sequencing to enable a transcriptome-wide mapping of SAFB1 protein-RNA interactions in breast cancer MCF-7 cells.

Deregulation of splicing factors and breast cancer development.

It is well known that many genes implicated in the development and progression of breast cancer undergo aberrant alternative splicing events to produce proteins with pro-cancer properties. These changes in alternative splicing can arise from mutations or single-nucleotide polymorphisms (SNPs) within the DNA sequences of cancer-related genes, which can strongly affect the activity of splicing factors and influence the splice site choice. However, it is important to note that absence of mutations is not sufficient to prevent misleading choices in splice site selection.

The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web.

The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies.

DNA methylation abnormalities at gene promoters are extensive and variable in the elderly and phenocopy cancer cells.

Abnormal patterns of DNA methylation are one of the hallmarks of cancer cells. The process of aging has also been associated with similar, albeit less dramatic, changes in methylation patterns, leading to the hypothesis that age-related changes in DNA methylation may partially underlie the increased risk of cancer in the elderly. Here we studied 377 participants aged 85 yr from the Newcastle 85+ Study to investigate the extent of, and interindividual variation in, age-related changes in DNA methylation at specific CpG islands.

Acquisition of aberrant DNA methylation is associated with frailty in the very old: findings from the Newcastle 85+ Study.

Frailty is a major health problem in older people and, as the population ages, identification of its underlying biological mechanisms will be increasingly important. DNA methylation patterns within genomic DNA change during ageing and alterations in DNA methylation, particularly at gene promoter regions, can lead to altered gene expression. However the importance of altered DNA methylation in frailty is largely unknown.

Clinical Significance of HER-2 Splice Variants in Breast Cancer Progression and Drug Resistance.

Overexpression of human epidermal growth factor receptor (HER-2) occurs in 20-30% of breast cancers and confers survival and proliferative advantages on the tumour cells making HER-2 an ideal therapeutic target for drugs like Herceptin. Continued delineation of tumour biology has identified splice variants of HER-2, with contrasting roles in tumour cell biology. For example, the splice variant Δ16HER-2 (results from exon 16 skipping) increases transformation of cancer cells and is associated with treatment resistance; conversely, Herstatin (results from intron 8 retention) and p100 (results from intron 15 retention) inhibit tumour cell proliferation.

Regulation of Mcl-1 by SRSF1 and SRSF5 in cancer cells.

Up-regulation of the apoptosis-regulatory gene Mcl-1 (myeloid cell leukemia-1) occurs in different cancer types and is linked with drug resistance to cancer therapies. It is well known that Mcl-1 pre-mRNA undergoes alternative splicing events to produce two functionally distinct proteins, Mcl-1(S) (pro-apoptotic) and Mcl-l(L) (anti-apoptotic); the latter isoform is predominant in different cancers including breast and ovarian cancer cells. In the present study we report that the RNA-binding protein (RBP) and proto-oncogene SRSF1 (serine and arginine-rich splicing factor 1) influences splicing of Mcl-1 in both MCF-7 and MDA-MB-231 breast cancer cells and JAR choriocarcinoma cells; we also show for the first time that another RBP SRSF5 affects splicing of Mcl-1 in the MCF-7 cells.

SAFB1- and SAFB2-mediated transcriptional repression: relevance to cancer.

SAFB1 (scaffold attachment factor B1) and a second family member SAFB2, are multifunctional proteins implicated in a variety of cellular processes including cell growth, apoptosis and stress response. Their potential function as tumour suppressors has been proposed based on well-described roles in tran-scriptional repression. The present review summarizes the current knowledge of SAFB1 and SAFB2 proteins in transcriptional repression with relevance to cancer.

Differential effects of selenium and knock-down of glutathione peroxidases on TNFα and flagellin inflammatory responses in gut epithelial cells.

Selenium (Se) is essential for human health. Despite evidence that Se intake affects inflammatory responses, the mechanisms by which Se and the selenoproteins modulate inflammatory signalling, especially in the gut, are not yet defined. The aim of this work was to assess effects of altered Se supply and knock-down of individual selenoproteins on NF-κB activation in gut epithelial cells.

Epigenetic inactivation of TWIST2 in acute lymphoblastic leukemia modulates proliferation, cell survival and chemosensitivity.

Background: Altered regulation of many transcription factors has been shown to be important in the development of leukemia. TWIST2 modulates the activity of a number of important transcription factors and is known to be a regulator of hematopoietic differentiation. Here, we investigated the significance of epigenetic regulation of TWIST2 in the control of cell growth and survival and in response to cytotoxic agents in acute lymphoblastic leukemia.

A T/C polymorphism in the GPX4 3'UTR affects the selenoprotein expression pattern and cell viability in transfected Caco-2 cells.

Background: Synthesis of selenoproteins such as glutathione peroxidases (GPx) requires a specific tRNA and a stem-loop structure in the 3'untranslated region (3'UTR) of the mRNA. A common single nucleotide polymorphism occurs in the GPX4 gene in a region corresponding to the 3'UTR.

Methods: The two variant 3'UTR sequences were linked to sequences from a selenoprotein reporter gene (iodothyronine deiodinase) and expressed in Caco-2 cells.

The dual role of HLXB9 in leukemia.

Background: The HLXB9 gene encodes a homeodomain containing transcription factor which has been implicated in the development of both solid and hematological malignancies. In leukemia it is one of the two fused genes, along with ETV6, in a recurrent translocation frequently observed in infant AML.

Procedure: Here we investigate the role of epigenetic inactivation of the HLXB9 gene in leukemia.

Staufen1 is expressed in preimplantation mouse embryos and is required for embryonic stem cell differentiation.

Pluripotent mouse embryonic stem (mES) cells derived from the blastocyst of the preimplantation embryo can be induced to differentiate in vitro along different cell lineages. However the molecular and cellular factors that signal and/or determine the expression of key genes, and the localisation of the encoded proteins, during the differentiation events are poorly understood. One common mechanism by which proteins can be targeted to specific regions of the cell is through the asymmetric localisation of mRNAs and Staufen, a double-stranded RNA binding protein, is known to play a direct role in mRNA transport and localisation.

Polarised distribution of the RNA-binding protein Staufen in differentiated intestinal epithelial cells.

mRNA localisation, as a mechanism for directing localised protein synthesis, plays a vital role in the functioning of certain cells, such as neurons and oocytes. Potentially this mechanism may also occur in polarised intestinal epithelial cells. Here we show that Staufen1(55), a protein involved in mRNA localisation and transport, is asymmetrically distributed in differentiated Caco-2 intestinal epithelial cells and partly co-localised with calnexin, a marker of the endoplasmic reticulum.