Hole Spin Mixing in InAs Quantum Dot Molecules

Holes confined in single InAs quantum dots have recently emerged as a promising system for the storage or manipulation of quantum information. These holes are often assumed to have only heavy-hole character and further assumed to have no mixing between orthogonal heavy hole spin projections (in the absence of a transverse magnetic field). The same assumption has been applied to InAs quantum dot molecules formed by two stacked InAs quantum dots that are coupled by coherent tunneling of the hole between the two dots. We present experimental evidence of the existence of a hole spin mixing term obtained with magneto-photoluminescence spectroscopy on such InAs quantum dot molecules. We use a Luttinger spinor model to explain the physical origin of this hole spin mixing term: misalignment of the dots along the stacking direction breaks the angular symmetry and allows mixing through the light-hole component of the spinor. We discuss how this novel spin mixing mechanism may offer new spin manipulation opportunities that are unique to holes.Comment: 13 pages, 9 figure

HER2 testing in breast cancer: Opportunities and challenges

Human epidermal growth factor receptor 2 (HER2) is overexpressed in 15-25% of breast cancers, usually as a result of HER2 gene amplification. Positive HER2 status is considered to be an adverse prognostic factor. Recognition of the role of HER2 in breast cancer growth has led to the development of anti-HER2 directed therapy, with the humanized monoclonal antibody trastuzumab (Herceptin (R)) having been approved for the therapy of HER2-positive metastatic breast cancer. Clinical studies have further suggested that HER2 status can provide important information regarding success or failure of certain hormonal therapies or chemotherapies. As a result of these developments, there has been increasing demand to perform HER2 testing on current and archived breast cancer specimens. This article reviews the molecular background of HER2 function, activation and inhibition as well as current opinions concerning its role in chemosensitivity and interaction with estrogen receptor biology. The different tissue-based assays used to detect HER2 amplification and overexpression are discussed with respect to their advantages and disadvantages, when to test (at initial diagnosis or pre-treatment), where to test (locally or centralized) and the need for quality assurance to ensure accurate and valid testing results

tabAnti-HER2 (erbB-2) oncogene effects of phenolic compounds directly isolated from commercial Extra-Virgin Olive Oil (EVOO)

<p>Abstract</p> <p>Background</p> <p>The effects of the olive oil-rich Mediterranean diet on breast cancer risk might be underestimated when HER2 (<it>ERB</it>B2) oncogene-positive and HER2-negative breast carcinomas are considered together. We here investigated the anti-HER2 effects of phenolic fractions directly extracted from Extra Virgin Olive Oil (EVOO) in cultured human breast cancer cell lines.</p> <p>Methods</p> <p>Solid phase extraction followed by semi-preparative high-performance liquid chromatography (HPLC) was used to isolate phenolic fractions from commercial EVOO. Analytical capillary electrophoresis coupled to mass spectrometry was performed to check for the composition and to confirm the identity of the isolated fractions. EVOO polyphenolic fractions were tested on their tumoricidal ability against HER2-negative and HER2-positive breast cancer <it>in vitro </it>models using MTT, crystal violet staining, and Cell Death ELISA assays. The effects of EVOO polyphenolic fractions on the expression and activation status of HER2 oncoprotein were evaluated using HER2-specific ELISAs and immunoblotting procedures, respectively.</p> <p>Results</p> <p>Among the fractions mainly containing the <it>single phenols </it>hydroxytyrosol and tyrosol, the <it>polyphenol acid </it>elenolic acid, the <it>lignans </it>(+)-pinoresinol and 1-(+)-acetoxypinoresinol, and the <it>secoiridoids </it>deacetoxy oleuropein aglycone, ligstroside aglycone, and oleuropein aglycone, all the major EVOO polyphenols (<it>i.e. </it>secoiridoids and lignans) were found to induce strong tumoricidal effects within a micromolar range by selectively triggering high levels of apoptotic cell death in HER2-overexpressors. Small interfering RNA-induced depletion of HER2 protein and lapatinib-induced blockade of HER2 tyrosine kinase activity both significantly prevented EVOO polyphenols-induced cytotoxicity. EVOO polyphenols drastically depleted HER2 protein and reduced HER2 tyrosine autophosphorylation in a dose- and time-dependent manner. EVOO polyphenols-induced HER2 downregulation occurred regardless the molecular mechanism contributing to HER2 overexpression (<it>i.e</it>. naturally by gene amplification and ectopically driven by a viral promoter). Pre-treatment with the proteasome inhibitor MG132 prevented EVOO polyphenols-induced HER2 depletion.</p> <p>Conclusion</p> <p>The ability of EVOO-derived polyphenols to inhibit HER2 activity by promoting the proteasomal degradation of the HER2 protein itself, together with the fact that humans have safely been ingesting secoiridoids and lignans as long as they have been consuming olives and OO, support the notion that the stereochemistry of these phytochemicals might provide an excellent and safe platform for the design of new HER2-targeting agents.</p

HER2 Phosphorylation Is Maintained by a PKB Negative Feedback Loop in Response to Anti-HER2 Herceptin in Breast Cancer

A feedback loop maintains HER2 receptor signalling and cell survival in response to Herceptin treatment in HER2-positive breast cancers, but this Herceptin resistance may be bypassed by pan-HER inhibitors

Associations between cigarette smoking and mitochondrial DNA abnormalities in buccal cells

DNA alterations in mitochondria are believed to play a role in carcinogenesis and are found in smoking-related cancers. We sought to replicate earlier findings for the association of smoking with increased mitochondrial DNA (mtDNA) content in buccal cells and further hypothesized that there would be an increased number of somatic mtDNA mutations in smokers. Buccal cells and blood lymphocytes were studied from 42 healthy smokers and 30 non-smokers. Temporal temperature gradient electrophoresis screening and sequencing was used to identify mtDNA mutations. The relative mtDNA content was determined by real-time polymerase chain reaction. Assuming that mtDNA in lymphocytes represents the inherited sequence, it was found that 31% of smokers harbored at least one somatic mtDNA mutation in buccal cells with a total of 39 point mutations and 8 short deletions/insertions. In contrast, only 23% of non-smokers possessed mutations with a total of 10 point mutations and no insertions/deletions detected. mtDNA somatic mutation density was higher in smokers (0.68/10 000 bp per person) than in non-smokers (0.2/10 000 bp per person). There was a statistically significant difference in the pattern of homoplasmy and heteroplasmy mutation changes between smokers and non-smokers. Whereas non-smokers had the most mutations in D-loop region (70%), smokers had mutations in both messenger RNA encoding gene (36%) and D-loop region (49%). The mean ratio of buccal cells to lymphocytes of mtDNA content in smokers was increased (2.81) when compared with non-smokers (0.46). These results indicate that cigarette smoke exposure affects mtDNA in buccal cells of smokers. Additional studies are needed to determine if mitochondrial mutation assays provide new or complementary information for estimating cigarette smoke exposure at the cellular level or as a cancer risk biomarker

Targeting of mutant hogg1 in mammalian mitochondria and nucleus: effect on cellular survival upon oxidative stress

BACKGROUND: Oxidative damage to mitochondrial DNA has been implicated as a causative factor in a wide variety of degenerative diseases, aging and cancer. The modified guanine, 7,8-dihydro-8-oxoguanine (also known as 8-hydroxyguanine) is one of the major oxidized bases generated in DNA by reactive oxygen species and has gained most of the attention in recent years as a marker of oxidative DNA injury and its suspected role in the initiation of carcinogenesis. 8-hydroxyguanine is removed by hOgg1, a DNA glycosylase/AP lyase involved in the base excision repair pathway. METHODS: We over-expressed wild type and R229Q mutant hOGG1 in the nucleus and mitochondria of cells lacking mitochondrial hOGG1 expression through an expression vector containing nuclear and mitochondrial targeting sequence respectively. We used quantitative real time PCR to analyze mtDNA integrity after exposure to oxidative damaging agents, in cells transfected with or without mitochondrially-targeted mutant hogg1. RESULT: Over-expression of wild type hOgg1 in both nucleus and mitochondria resulted in increased cellular survival when compared to vector or mutant over-expression of hOGG1. Interestingly, mitochondrially-targeted mutant hogg1 resulted in more cell death than nuclear targeted mutant hogg1 upon exposure of cells to oxidative damage. Additional we examined mitochondrial DNA integrity after oxidative damage exposure using real-time quantitative PCR. The presence of mutant hogg1 in the mitochondria resulted in reduced mitochondrial DNA integrity when compared to the wild type. Our work indicates that the R229Q hOGG1 mutation failed to protect cells from oxidative damage and that such mutations in cancer may be more detrimental to cellular survival when present in the mitochondria than in the nucleus. CONCLUSION: These findings suggest that deficiencies in hOGG1, especially in the mitochondria may lead to reduced mitochondrial DNA integrity, consequently resulting in decreased cell viability

Targeting ErbB2 and ErbB3 with a bispecific single-chain Fv enhances targeting selectivity and induces a therapeutic effect in vitro

Inappropriate signalling through the EGFR and ErbB2/HER2 members of the epidermal growth factor family of receptor tyrosine kinases is well recognised as being causally linked to a variety of cancers. Consequently, monoclonal antibodies specific for these receptors have become increasingly important components of effective treatment strategies for cancer. Increasing evidence suggests that ErbB3 plays a critical role in cancer progression and resistance to therapy. We hypothesised that co-targeting the preferred ErbB2/ErbB3 heterodimer with a bispecific single-chain Fv (bs-scFv) antibody would promote increased targeting selectivity over antibodies specific for a single tumour-associated antigen (TAA). In addition, we hypothesised that targeting this important heterodimer could induce a therapeutic effect. Here, we describe the construction and evaluation of the A5-linker-ML3.9 bs-scFv (ALM), an anti-ErbB3/ErbB2 bs-scFv. The A5-linker-ML3.9 bs-scFv exhibits selective targeting of tumour cells in vitro and in vivo that co-express the two target antigens over tumour cells that express only one target antigen or normal cells that express low levels of both antigens. The A5-linker-ML3.9 bs-scFv also exhibits significantly greater in vivo targeting of ErbB2‘+'/ErbB3‘+' tumours than derivative molecules that contain only one functional arm targeting ErbB2 or ErbB3. Binding of ALM to ErbB2‘+'/ErbB3‘+' cells mediates inhibition of tumour cell growth in vitro by effectively targeting the therapeutic anti-ErbB3 A5 scFv. This suggests both that ALM could provide the basis for an effective therapeutic agent and that engineered antibodies selected to co-target critical functional pairs of TAAs can enhance the targeting specificity and efficacy of antibody-based cancer therapeutics

Olive oil's bitter principle reverses acquired autoresistance to trastuzumab (Herceptin™) in HER2-overexpressing breast cancer cells

[Background] A low incidence of breast cancer in the Mediterranean basin suggests that a high consumption of Extra Virgin Olive Oil (EVOO) might confer this benefit. While the anti-HER2 oncogene effects of the main ω-9 fatty acid present in EVOO triacylglycerols (i.e., oleic acid) have been recently described, the anti-breast cancer activities of EVOO non-glyceridic constituents -which consist of at least 30 phenolic compounds-, remained to be evaluated. [Methods] Semi-preparative HPLC was used to isolate EVOO polyphenols (i.e., tyrosol, hydroxytyrosol, oleuropein). Both the anti-proliferative and the pro-apoptotic effects of EVOO phenolics were evaluated by using MTT-based quantification of metabolically viable cells and ELISA-based detection of histone-associated DNA fragments, respectively. The nature of the interaction between oleuropein aglycone and the anti-HER2 monoclonal antibody trastuzumab (Herceptin™) was mathematically evaluated by the dose-oriented isobologram technique. HER2-specific ELISAs were employed to quantitatively assess both the basal cleavage of the HER2 extracellular domain (ECD) and the expression level of total HER2. The activation status of HER2 was evaluated by immunoblotting procedures using a monoclonal antibody specifically recognizing the tyrosine phosphorylated (Phosphor-Tyr1248) form of HER2. [Results] Among EVOO polyphenols tested, oleuropein aglycone was the most potent EVOO phenolic in decreasing breast cancer cell viability. HER2 gene-amplified SKBR3 cells were ~5-times more sensitive to oleuropein aglycone than HER2-negative MCF-7 cells. Retroviral infection of the HER2 oncogene in MCF-7 cells resulted in a "SKBR3-assimilated" phenotype of hypersensitivity to oleuropein aglycone. An up to 50-fold increase in the efficacy of trastuzumab occurred in the presence of oleuropein aglycone. A preclinical model of acquired autoresistance to trastuzumab (SKBR3/Tzb100 cells) completely recovered trastuzumab sensitivity (> 1,000-fold sensitization) when co-cultured in the presence of oleuropein aglycone. Indeed, the nature of the interaction between oleuropein aglycone and trastuzumab was found to be strongly synergistic in Tzb-resistant SKBR3/Tzb100 cells. Mechanistically, oleuropein aglycone treatment significantly reduced HER2 ECD cleavage and subsequent HER2 auto-phosphorylation, while it dramatically enhanced Tzb-induced down-regulation of HER2 expression. [Conclusion] Olive oil's bitter principle (i.e., oleuropein aglycone) is among the first examples of how selected nutrients from an EVOO-rich "Mediterranean diet" directly regulate HER2-driven breast cancer disease.JAM is the recipient of a Basic, Clinical and Translational Research Award (BCTR0600894) from the Susan G. Komen Breast Cancer Foundation (Texas, USA). This work was also supported by the Instituto de Salud Carlos III (Ministerio de Sanidad y Consumo, Fondo de Investigación Sanitaria -FIS-, Spain, Grants CP05-00090 and PI06-0778 to JAM, and Grant RD06-0020-0028 to JAM, RC and JB)

The clinical and functional significance of c-Met in breast cancer: a review

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.CMH-Y is funded by a Cancer Research UK Clinical Research Fellowship. JLJ is funded by the Breast Cancer Campaign Tissue Bank