Suppressive and Hypermethylated MicroRNAs in the Pathogenesis of Breast Cancer

MicroRNAs (miRNAs) are involved in oncogenesis by suppression of proto-oncogenes or tumor suppressive genes. This review presents data of suppressive miRNAs role in the mechanisms of occurrence and development of malignant tumors of breast cancer as the example—that is the most widespread oncopathology in women. Targets and functions of suppressive and antimetastatic miRNAs have been illustrated, as well as for suppressive miRNAs with an oncogenic potential (such as miR-200a, miR-200c) that appears probably owing to the ability of miRNA to interact with a variety of targets depending on the cellular content. Based on the published and the authors’ own data, the role of hypermethylation of promoter regions in inhibition of expression and regulatory function of miRNA genes in breast cancer was characterized. In conclusion, the authors pointed future prospects of clinical application of suppressive miRNAs in diagnostics and treatment of breast cancer.     

Activation-coupled membrane-type 1 matrix metalloproteinase membrane trafficking

The transmembrane collagenase MT1-MMP (membrane-type 1 matrix metalloproteinase), also known as MMP-14, has a critical function both in normal development and in cancer progression, and is subject to extensive controls at the post-translational level which affect proteinase activity. As zymogen activation is crucial for MT1-MMP activity, an alpha1-PI (alpha1-proteinase inhibitor)-based inhibitor was designed by incorporating the MT1-MMP propeptide cleavage sequence into the alpha1-PI reactive-site loop (designated alpha1-PI(MT1)) and this was compared with wild-type alpha1-PI (alpha1-PI(WT)) and the furin inhibitory mutant alpha1-PI(PDX). Alpha1-PI(MT1) formed an SDS-stable complex with furin and inhibited proMT1-MMP activation. A consequence of the loss of MT1-MMP activity was the activation of proMMP-2 and the inhibition of MT1-MMP-mediated collagen invasion. alpha1-PI(MT1) expression also resulted in the intracellular accumulation of a glycosylated species of proMT1-MMP that was retained in the perinuclear region, leading to significantly decreased cell-surface accumulation of proMT1-MMP. These observations suggest that both the subcellular localization and the activity of MT1-MMP are regulated in a coordinated fashion, such that proMT1-MMP is retained intracellularly until activation of its zymogen, then proMT1-MMP traffics to the cell surface in order to cleave extracellular substrates.     

Increased lymphocyte infiltration in patients with head and neck cancer treated with the IRX-2 immunotherapy regimen

Twenty-seven subjects with squamous cell cancer of the head and neck received the neoadjuvant IRX-2 immunotherapy regimen prior to surgery in a Phase 2 trial. Pretreatment tumor biopsies were compared with the primary tumor surgical specimens for lymphocyte infiltration, necrosis and fibrosis, using hematoxylin and eosin stain and immunohistochemistry in 25 subjects. Sections were examined by three pathologists. Relative to pretreatment biopsies, increases in lymphocyte infiltration (LI) were seen using H and E or immunohistochemistry. CD3+ CD4+ T cells and CD20+ B cells were primarily found in the peritumoral stroma and CD3+ CD8+ T cells and CD68+ macrophages were mainly intratumoral. LI in the surgical specimens were associated with reductions in the primary tumor size. Improved survival at 5?years was correlated with high overall LI in the tumor specimens. Neoadjuvant IRX-2 immunotherapy regimen may restore immune responsiveness presumably by mobilizing tumor infiltrating effector lymphocytes and macrophages into the tumor.     

Activation of human peripheral IgM+ B cells is transiently inhibited by BCR-independent aggregation of Fc gammaRIIB

Immune complexes can trigger a SHIP-1-independent proapoptotic signal in mouse class-switched IgG(+) B cells and plasma cells by binding to Fc gammaRIIB, in the absence of concomitant coaggregation with BCR, hence regulating plasma cell survival and participating in the selection of B cells producing high affinity Abs during secondary Ab responses. By contrast, we demonstrate in the present study that the unique aggregation of Fc gammaRIIB on human peripheral IgM(+) B cells does not induce apoptosis but transiently inhibits B cell proliferation and calcium influx triggered by BCR cross-linking. Using human peripheral B cells and IIA1.6 lymphoma B cells expressing wild-type human Fc gammaRIIB (IIA1.6-Fc gammaRIIB), we also show that the unique aggregation of human Fc gammaRIIB induces ITIM phosphorylation. This aggregation provokes the recruitment of phosphorylated SHIP-1 by Fc gammaRIIB and inhibits the constitutive phosphorylation of Akt in human IIA1.6-Fc gammaRIIB cells. This inhibitory signaling pathway is abrogated in IIA1.6 cells expressing ITIM-mutated Fc gammaRIIB (Fc gammaRIIB(Y292G)), suggesting that ITIM phosphorylation is necessary for Fc gammaRIIB-induced B cell blockade. Overall, we demonstrate that the unique aggregation of Fc gammaRIIB on human peripheral IgM(+) B cells is sufficient to transiently down-regulate their activation without inducing apoptosis. Our results suggest that Fc gammaRIIB could negatively regulate IgM(+) B cells before class-switch occurrence and that its unique engagement by immune complexes represents a reversible checkpoint for peripheral IgM(+) B cells.     

Expression of multidrug resistance-related protein (MRP-1), lung resistance-related protein (LRP) and topoisomerase-II (TOPO-II) in Wilms' tumor: immunohistochemical study using TMA methodology

Aims: MRP-1, LRP and TOPO-II are all associated with protection of the cells from the adverse effects of various chemotherapeutics. The aim of this study was to measure the expression of these proteins in Wilms' tumor (WT). Materials and Methods: TMA block was constructed from 14 samples of WT's and from xenografts derived from them. Sections of the TMA were used for immunostaining against MRP-1, LRP and TOPO-IIa. Results: All normal kidneys expressed MRP-1 but were either weakly or negatively stained for LRP and TOPO-IIa. In WT samples, MRP-1 was universally expressed, exclusively in the tubular component, while there was no expression of LRP and TOPO-IIa showed heterogeneous distribution. The xenografts varied in their MRP-1 and TOPO-IIa expression and exhibited weak/negative staining of LRP. Conclusions: This study shows that although all the proteins evaluated, had different expression patterns in the tumor samples, the most prominent changes in expression were found for MRP-1. The exact clinical implications of these changes in expression and their relevance to the resistance of these tumors to chemotherapy requires further investigation. The finding of different expression profiles for the multidrug resistance proteins in the original WT's and their xenografts suggests that the results of animal cancer models may be difficult to interpret.     

Two tightly linked QTLs modify tomato sugar content via different physiological pathways

Congenic lines that differ in a single defined chromosome segment are useful for the study of complex phenotypes, as they allow isolation of the effect of a particular quantitative trait locus (QTL) from those of the entire genome. We conducted high-resolution QTL mapping of a 9-cM introgression, originating from the wild tomato species Lycopersicon pennellii, in two extremely different genetic and physiological backgrounds. In the "indeterminate" glasshouse background we identified only a single QTL ( Brix9-2-5) that affects the total soluble solids of the fruit [mainly sugars, measured in Brix units (B)]. This QTL was previously delimited within the gene for an apoplastic invertase, Lin5, that modulates sugar partitioning to the fruit. Analysis of the effects of the same chromosome segment in "determinate", open-field tomatoes, revealed two QTLs, 0.3 cM apart: the fruit-specific Brix9-2-5 that affects B only, and the shoot-specific PW9-2-5, which accounts for an altered growth habit resulting in increases in plant weight, yield, and B. This study highlights the power of the congenic approach for dissecting developmental pathways leading to complex phenotypes.     

Human cytotoxic T lymphocytes (CTL) against Epstein-Barr virus (EBV) infected cells: EBV specificity and involvement of major histocompatibility complex determinants in the lysis exerted by anti-EBV CTL toward HLA-compatible and allogeneic target cells

Human peripheral blood lymphocytes (PBL), from anti-Epstein-Barr virus (EBV)-seropositive donors, were stimulated by EBV and were shown to be cytotoxic toward autologous, HLA-compatible, and fully allogeneic EBV-transformed target cells. The lysis was not due to natural killer (NK) cells since the target cells used were resistant to lysis by fresh PBL and by virus-stimulated PBL-depleted of AET-SRBC-rosetting T cells (the latter being still fully cytotoxic on K562 NK-susceptible target cells). Conversely only E-rosette-purified (T) lymphocytes killed EBV-transformed HLA-compatible and allogeneic target cells. Moreover, anti-MHC antibodies inhibited the cytotoxicity exerted by EBV-induced cytotoxic T lymphocytes (CTL) on both autologous and allogeneic target cells. Finally the lysis was EBV specific since PHA blasts were not killed and since only EBV-transformed cells could compete for lysis with the EBV-positive target cells. Efficient competition was achieved by EBV-transformed cells autologous or allogeneic to the targets, even when effector and target cells were fully allogeneic. All together, the data suggest that human anti-EBV CTL may recognize nonpolymorphic HLA determinants on the target cells in association with the virus-induced antigens.