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Electrochemical methods hold promise for fast and inexpensive determination of cancer biomarkers, including microRNAs playing an important role in regulation of gene expression. We developed a simple assay utilizing (i) microRNA labeling with osmium(VI) complexes, (ii) hybridization of microRNA with magnetic bead-immobilized capture probe, and (iii) adsorptive transfer stripping (AdTS) technique in which working electrode is dipped into a microliter-sized drop for direct adsorption of microRNA. Increased sensitivity and decreased sample consumption was achieved, and nanogram quantities of microRNA present in 500-fold excess of total RNA were determined. Our results indicate only negligible interference during hybridization from other RNA molecules. [ABSTRACT FROM AUTHOR]

Transcriptomic screens in breast cancer cell lines have identified a protein named anterior gradient-2 (AGR2) as a potentially novel oncogene overexpressed in estrogen receptor (ER) positive tumours. As targeting the ER is responsible for major improvements in cure rates and prevention of breast cancers, we have evaluated the pro-oncogenic function of AGR2 in anti-hormone therapeutic responses. We show that AGR2 expression promotes cancer cell survival in clonogenic assays and increases cell proliferation and viability in a range of cancer cell lines. Chromatin immunoprecipitation and reporter assays indicate that AGR2 is transcriptionally activated by estrogen through ERα. However, we also found that AGR2 expression is elevated rather than inhibited in response to tamoxifen, thus identifying a novel mechanism to account for an agonistic effect of the drug on a specific pro-oncogenic pathway. Consistent with these data, clinical analysis indicates that AGR2 expression is related to treatment failure in ERα-positive breast cancers treated with tamoxifen. In contrast, AGR2 is one of the most highly suppressed genes in cancers of responding patients treated with the anti-hormonal drug letrozole. These data indicate that the AGR2 pathway represents a novel pro-oncogenic pathway for evaluation as anti-cancer drug developments, especially therapies that by-pass the agonist effects of tamoxifen. [ABSTRACT FROM AUTHOR]

p53 missense mutant proteins commonly show increased stability compared to wild-type p53, which is thought to depend largely on the inability of mutant p53 to induce the ubiquitin ligase MDM2. However, recent work using mouse models has shown that the accumulation of mutant p53 occurs only in tumour cells, indicating that stabilization requires additional factors. To clarify the stabilization of p53 mutants in tumours, we analysed factors that affect their folding and degradation. Although all missense mutants that we studied are more stable than wild-type p53, the levels correlate with individual structural characteristics, which may be reflected in different gain-of-function properties. In the absence of Hsp90 activity, the less stable unfolded p53 mutants preferentially associate in a complex with Hsp70 and CHIP (carboxy terminus of Hsp70-interacting protein), and we show that CHIP is responsible for ubiquitination and degradation of these mutants. The demonstration of a complex interplay between Hsp90, Hsp70 and CHIP that regulate the stability of different p53 mutant proteins improves our understanding of the pro-tumorigenic effects of increased Hsp90 activity during multi-stage carcinogenesis. Understanding the roles of Hsp90, Hsp70 and CHIP in cancers may also provide an important avenue through which to target p53 to enhance treatment of human cancers.Oncogene (2008) 27, 3371–3383; doi:10.1038/sj.onc.1211010; published online 28 January 2008 [ABSTRACT FROM AUTHOR]

Ferrocenes represent an interesting group of drugs with potential antitumor properties. Moreover, their electronic properties make them suitable for electrochemical studies. We determined an uptake of a novel ferrocene derivative in low μM concentrations by selected cancer cell lines and showed its localization predominantly in cytoplasm, using glassy carbon electrodes. [ABSTRACT FROM AUTHOR]

Heat shock proteins Hsp90 and Hsp70 facilitate protein folding but can also direct proteins for ubiquitin-mediated degradation. The mechanisms regulating these opposite activities involve Hsp binding to co-chaperones including CHIP and HOP at their C-termini. We demonstrated that the extreme C-termini of Hsp70 and Hsp90 contain phosphorylation sites targeted by kinases including CK1, CK2 and GSK3-β in vitro. The phosphorylation of Hsp90 and Hsp70 prevents binding to CHIP and thus enhances binding to HOP. Highly proliferative cells contain phosphorylated chaperones in complex with HOP and phospho-mimetic and non-phosphorylable Hsp mutant proteins show that phosphorylation is directly associated with increased proliferation rate. We also demonstrate that primary human cancers contain high levels of phosphorylated chaperones and show increased levels of HOP protein and mRNA. These data identify C-terminal phosphorylation of Hsp70 and Hsp90 as a switch for regulating co-chaperone binding and indicate that cancer cells possess an elevated protein folding environment by the concerted action of co-chaperone expression and chaperone modifications. In addition to identifying the pathway responsible for regulating chaperone-mediated protein folding/degradation balances in normal cells, the data provide novel mechanisms to account for the aberrant chaperone activities observed in human cancer cells and have implications for the application of anti-chaperone therapies in cancer treatment. [ABSTRACT FROM AUTHOR]

Clinical studies have defined the core 'genetic blueprint' of a cancer cell, but this information does not necessarily predict the cancer phenotype. Signalling hubs that mediate such phenotype have been identified largely using OMICS platforms that measure dynamic molecular changes within the cancer cell landscape. The pro-oncogenic protein anterior gradient 2 (AGR2) is a case in point; AGR2 has been shown using a range of expression platforms to be involved in asthma, inflammatory bowel disease, cell transformation, cancer drug resistance and metastatic growth. AGR2 protein is also highly overexpressed in a diverse range of human cancers and can be secreted and detected in extracellular fluids, thus representing a compelling pro-oncogenic signalling intermediate in human cancer. AGR2 belongs to the protein disulphide isomerase family with all the key features of an endoplasmic reticulum-resident protein-this gives clues into how it might function as an oncoprotein through the regulation of protein folding, maturation and secretion that can drive metastatic cell growth. In this review, we will describe the known aspects of AGR2 molecular biology, including gene structure and regulation, emerging protein interaction networks and how its subcellular localization mediates its biological functions. We will finally review the cases of AGR2 expression in human cancers, the pathophysiological consequences of AGR2 overexpression, its potential role as a tumour biomarker that predicts the response to therapy and how the AGR2 pathway might form the basis for drug discovery programmes aimed at targeting protein folding/maturation pathways that mediate secretion and metastasis. [ABSTRACT FROM AUTHOR]