Inhibiting HER3 Hyperphosphorylation in HER2-Overexpressing Breast Cancer through Multimodal Therapy with Branched Gold Nanoshells

Treatment failure in breast cancers overexpressing human epidermal growth factor receptor 2 (HER2) is associated mainly to the upregulation of human epidermal growth factor receptor 3 (HER3) oncoprotein linked to chemoresitence. Therefore, to increase patient survival, here a multimodal theranostic nanoplatform targeting both HER2 and HER3 is developed. This consists of doxorubicin-loaded branched gold nanoshells functionalized with the near-infrared (NIR) fluorescent dye indocyanine green, a small interfering RNA (siRNA) against HER3, and the HER2-specific antibody Transtuzumab, able to provide a combined therapeutic outcome (chemo- and photothermal activities, RNA silencing, and immune response). In vitro assays in HER2+ /HER3+ SKBR-3 breast cancer cells have shown an effective silencing of HER3 by the released siRNA and an inhibition of HER2 oncoproteins provided by Trastuzumab, along with a decrease of the serine/threonine protein kinase Akt (p-AKT) typically associated with cell survival and proliferation, which helps to overcome doxorubicin chemoresistance. Conversely, adding the NIR light therapy, an increment in p-AKT concentration is observed, although HER2/HER3 inhibitions are maintained for 72 h. Finally, in vivo studies in a tumor-bearing mice model display a significant progressively decrease of the tumor volume after nanoparticle administration and subsequent NIR light irradiation, confirming the potential efficacy of the hybrid nanocarrier.

From neural stem cells to glioblastoma: A natural history of GBM recapitulated in vitro

Due to its aggressive and invasive nature glioblastoma (GBM), the most common and aggressive primary brain tumour in adults, remains almost invariably lethal. Significant advances in the last several years have elucidated much of the molecular and genetic complexities of GBM. However, GBM exhibits a vast genetic variation and a wide diversity of phenotypes that have complicated the development of effective therapeutic strategies. This complex pathogenesis makes necessary the development of experimental models that could be used to further understand the disease, and also to provide a more realistic testing ground for potential therapies. In this report, we describe the process of transformation of primary mouse embryo astrocytes into immortalized cultures with neural stem cell characteristics, that are able to generate GBM when injected into the brain of C57BL/6 mice, or heterotopic tumours when injected IV. Overall, our results show that oncogenic transformation is the fate of NSC if cultured for long periods in vitro. In addition, as no additional hit is necessary to induce the oncogenic transformation, our model may be used to investigate the pathogenesis of gliomagenesis and to test the effectiveness of different drugs throughout the natural history of GBM.

Expression of myostatin in human hematopoietic cells unveils novel autocrine/paracrine actions for the hormone

Myostatin is a member of the transforming growth factor β (TGFβ) superfamily that has a well-established role as a mediator of muscle growth and development. However, myostatin is now emerging as a pleiotropic hormone with multiple actions in the regulation of the metabolism as well as several aspects of both cardiac and smooth muscle cells physiology. In addition, myostatin is also expressed in several nonmuscular cells where its physiological role remains to be elucidated in most cases. In this report, we have shown that both myostatin and its receptor system are expressed in blood cells and in hematopoietic cell lines. Furthermore, myostatin treatment promotes differentiation of both HL60 and K562 cells through a mechanism that involves activation of extracellular signal-regulated kinases 1/2 and p38-mitogen-activated protein kinase, thus leading to the possibility that myostatin may be a paracrine/autocrine factor involved in the control of haematopoiesis. In addition, the presence of myostatin expression in immune cells could envisage a novel role for the hormone in the pathogenesis of inflammatory diseases.

Uncoupling Oncogene-Induced Senescence (OIS) and DNA Damage Response (DDR) triggered by DNA hyper-replication: lessons from primary mouse embryo astrocytes (MEA)

Oncogene-induced senescence (OIS) is a complex process, in which activation of oncogenic signals during early tumorigenesis results in a high degree of DNA replication stress. The ensuing response to the DNA damage produces a permanent G1 arrest that prevents unlimited cell proliferation and lessens the development of tumours. However, despite the role of OIS in the proliferative arrest resulting from an activating oncogenic-lesion has obtained wide support, there is also evidence indicating that cells may overcome oncogene-induced senescence under some circumstances. In this study, we have investigated the possibility that some of the assumptions on the role of DNA damage response (DDR) in triggering OIS may depend on the fact that most of the available data were obtained in mouse embryo fibroblast. By comparing the degree of OIS observed in mouse embryo fibroblasts (MEF) and mouse embryo astrocytes (MEA) obtained from the same individuals we have demonstrated that, despite truthful activation of DDR in both cell types, significant levels of OIS were only detected in MEF. Therefore, this uncoupling between OIS and DDR observed in astrocytes supports the intriguingly possibility that OIS is not a widespread response mechanism to DDR.

Fluorescent drug-loaded, polymeric-based, branched gold nanoshells for localized multimodal therapy and imaging of tumoral cells

Here we report the synthesis of PLGA/DOXO-core Au-branched shell nanostructures (BGNSHs) functionalized with a human serum albumin/indocyanine green/folic acid complex (HSA-ICG-FA) to configure a multifunctional nanotheranostic platform. First, branched gold nanoshells (BGNSHs) were obtained through a seeded-growth surfactant-less method. These BGNSHs were loaded during the synthetic process with the chemotherapeutic drug doxorubicin, a DNA intercalating agent and topoisomerase II inhibitior. In parallel, the fluorescent near-infrared (NIR) dye indocyanine green (ICG) was conjugated to the protein human serum albumin (HSA) by electrostatic and hydrophobic interactions. Subsequently, folic acid was covalently attached to the HSA-ICG complex. In this way, we created a protein complex with targeting specificity and fluorescent imaging capability. The resulting HSA-ICG-FA complex was adsorbed to the gold nanostructures surface (BGNSH-HSA-ICG-FA) in a straightforward incubation process thanks to the high affinity of HSA to gold surface. In this manner, BGNSH-HSA-ICG-FA platforms were featured with multifunctional abilities: the possibility of fluorescence imaging for diagnosis and therapy monitoring by exploiting the inherent fluorescence of the dye, and a multimodal therapy approach consisting of the simultaneous combination of chemotherapy, provided by the loaded drug, and the potential cytotoxic effect of photodynamic and photothermal therapies provided by the dye and the gold nanolayer of the hybrid structure, respectively, upon NIR light irradiation of suitable wavelength. The combination of this trimodal approach was observed to exert a synergistic effect on the cytotoxicity of tumoral cells in vitro. Furthermore, FA was proved to enhance the internalization of nanoplatform. The ability of the nanoplatforms as fluorescence imaging contrast agents was tested by preliminary analyzing their biodistribution in vivo in a tumor-bearing mice model.

Interferon-beta protects astrocytes against tumour necrosis factor-induced apoptosis via activation of p38 mitogen-activated protein kinase

Several large clinical trials have demonstrated that interferon-beta (IFN-beta) therapy is effective in the treatment of multiple sclerosis (MS) patients. However, the mechanisms underlying the beneficial effects of IFN-beta are not fully understood. Most of the effort in the study of the relevant mechanisms of IFN-beta has dealt with its immunomodulatory actions. However, the beneficial effects of IFN-beta in MS patients may also depend on non-immune mechanisms, including the modulation of astrocyte function. In the present work, we have found that IFN-beta treatment protects astrocytes against tumour necrosis factor-induced apoptosis via activation of p38 mitogen-activated protein kinase. We propose that this effect may be of importance to protect astrocytes against apoptosis within the demyelinated plaques of the MS.

Cyclin-dependent kinase antagonizes promyelocytic leukemia zinc-finger through phosphorylation

Acute promyelocytic leukemia is associated with chromosomal translocations that involve the RARalpha gene and several distinct loci producing a variety of fusion proteins. One such fusion partner is promyelocytic leukemia zinc-finger gene (PLZF), a member of the POK (POZ and Krüppel) family of transcriptional repressors that is a key developmental regulator, stem cell maintenance factor and tumor suppressor. Overexpression of PLZF has been shown to induce cell cycle arrest at the G(1) to S transition and repress the expression of key pro-proliferative genes such as CCNA2 and MYC. However, given this data suggesting an important growth inhibitory role for PLZF, relatively little is known regarding regulation of its activity. Here we show that the main cyclin-dependent kinase involved at the G(1) to S transition (CDK2) phosphorylates PLZF at two consensus sites found within PEST domains present in the hinge region of the protein. This phosphorylation triggers the ubiquitination and subsequent degradation of PLZF, which impairs PLZF transcriptional repression ability and antagonizes its growth inhibitory effects. This critical mechanism of PLZF regulation may thus be relevant for cell cycle progression during the development and the pathogenesis of human cancer.

Disruption of PLZP in mice leads to increased T-lymphocyte proliferation, cytokine production, and altered hematopoietic stem cell homeostasis

Deregulated function of members of the POK (POZ and Kruppel) family of transcriptional repressors, such as promyelocytic leukemia zinc finger (PLZF) and B-cell lymphoma 6 (BCL-6), plays a critical role in the pathogenesis of acute promyelocytic leukemia (APL) and non-Hodgkin's lymphoma, respectively. PLZP, also known as TZFP, FAZF, or ROG, is a novel POK protein that displays strong homology with PLZF and has been implicated in the pathogenesis of the cancer-predisposing syndrome, Fanconi's anemia, and of APL, in view of its ability to heterodimerize with the FANC-C and PLZF proteins, respectively. Here we report the generation and characterization of mice in which we have specifically inactivated the PLZP gene through in-frame insertion of a lacZ reporter and without perturbing the expression of the neighboring MLL2 gene. We show that PLZP-deficient mice display defects in cell cycle control and cytokine production in the T-cell compartment. Importantly, PLZP inactivation perturbs the homeostasis of the hematopoietic stem and/or progenitor cell. On the basis of our data, a deregulation of PLZP function in Fanconi's anemia and APL may affect the biology of the hematopoietic stem cell, in turn contributing to the pathogenesis of these disorders.

Essential role of Plzf in maintenance of spermatogonial stem cells

Little is known of the molecular mechanisms whereby spermatogonia, mitotic germ cells of the testis, self-renew and differentiate into sperm. Here we show that Zfp145, encoding the transcriptional repressor Plzf, has a crucial role in spermatogenesis. Zfp145 expression was restricted to gonocytes and undifferentiated spermatogonia and was absent in tubules of W/W(v) mutants that lack these cells. Mice lacking Zfp145 underwent a progressive loss of spermatogonia with age, associated with increases in apoptosis and subsequent loss of tubule structure but without overt differentiation defects or loss of the supporting Sertoli cells. Spermatogonial transplantation experiments revealed a depletion of spermatogonial stem cells in the adult. Microarray analysis of isolated spermatogonia from Zfp145-null mice before testis degeneration showed alterations in the expression profile of genes associated with spermatogenesis. These results identify Plzf as a spermatogonia-specific transcription factor in the testis that is required to regulate self-renewal and maintenance of the stem cell pool.

Plzf mediates transcriptional repression of HoxD gene expression through chromatin remodeling

The molecular mechanisms that regulate coordinated and colinear activation of Hox gene expression in space and time remain poorly understood. Here we demonstrate that Plzf regulates the spatial expression of the AbdB HoxD gene complex by binding to regulatory elements required for restricted Hox gene expression and can recruit histone deacetylases to these sites. We show by scanning forced microscopy that Plzf, via homodimerization, can form DNA loops and bridge distant Plzf binding sites located within HoxD gene regulatory elements. Furthermore, we demonstrate that Plzf physically interacts with Polycomb proteins on DNA. We propose a model by which the balance between activating morphogenic signals and transcriptional repressors such as Plzf establishes proper Hox gene expression boundaries in the limb bud.

Activation of human somatostatin receptor 2 promotes apoptosis through a mechanism that is independent from induction of p53

The ability of both somatostatin (SS) and its stable analogues to inhibit cell growth depends on the stimulation of specific membrane receptors (SSTR1-5), which belong to the G protein-coupled receptor family. Accumulating evidence suggests that the SSTR2 plays a major role in mediating cell cycle arrest, and it is also clear that SHP-1, a cytoplasmic phosphotyrosine phosphatase (PTP), is an essential component of the SSTR2-mediated cytostatic effect. In contrast, the possibility that SSTR2 activation may also lead to increased apoptosis is still beyond debate, despite SHP-1 activation is also able to promote cell death in several cell types. In the present work we have investigated the ability of SSTR2 to induce apoptosis in HL-60 cells. We have found that HL-60 cells uniquely express the SSTR2 subtype, and that stimulation of SSTR2 with the SS analogue SMS 201-995 results in an increased cell death. In all, these findings demonstrate that activation of SSTR2 promotes apoptosis in HL-60 cells. Moreover, in contrast with the proapoptotic mechanism previously reported for SSTR3, cell death induced by activation of SSTR2 is independent from accumulation of p53.

The role of promyelocytic leukemia zinc finger and promyelocytic leukemia in leukemogenesis and development

Acute promyelocytic leukemia (APL) was originally distinguished by an extremely poor clinical outcome. In the past few years, however, important progress has been made in defining the molecular basis of APL pathogenesis and in optimizing its treatment to an extent that this leukemia is now considered curable. Two features are unique to this leukemia: its remission after retinoic acid (RA) treatment through induction of blast differentiation, and the presence in the leukemic blast of fusion proteins in which the retinoic acid receptor alpha (RARalpha) fuses to distinct partners. Here we review how a detailed analysis of the functions of two of these RARalpha partners, the promyelocytic leukemia (PML) and promyelocytic leukemia zinc finger (PLZF) proteins, has allowed a greater understanding of the molecular mechanisms implicated in APL pathogenesis.

N-glycosylated variants of growth hormone in human pituitary extracts

This study was designed to investigate the existence, in human pituitary extracts, of growth hormone (GH) variants not encoded by the hGH-N gene. Using anion exchange-fast protein liquid chromatography followed by SDS-PAGE, we isolated several basic forms of pituitary GH. Incubation of these basic forms with endoglycosidase F/N-glycosidase F revealed that two of them (about 34 and 12 kD) were N-glycosylated. In contrast, no changes were found when samples were incubated with the O-linked glycosylation-specific O-glycosidase. Since the GH-N molecule lacks consensus sequences for N-linked glycosylation, our findings suggest that GH genes other than hGH-N are expressed in the human pituitary gland.

Role of growth hormone receptor in HL-60 cell survival

Although it is presently well established that locally produced growth hormone (GH) plays a major role in the regulation of survival mechanisms in hemopoietic cells, the responsible mechanisms are poorly understood, and the involvement of the GH receptor (GHR) has not even been demonstrated to date. In this work we investigated the presence of GHR in the human promyelocytic leukemia cell line HL-60, as well as the ability of GH treatment to stimulate both GHR and survival signaling pathways downstream GHR. Our results demonstrate that (1) both GHR mRNA and GHR immunoreactivity are present in HL-60 cells; (2) GH treatment results in an increase in the phosphorylation of the GHR-associated Jak2 and Stat3 proteins, indicating the ability of the hormone to induce receptor activation; and (3) activation of GHR increases the activity of Akt, a serine/threonine kinase that plays a prominent role in the regulation of cell survival. Taken together, these results demonstrate that GHR activation promotes survival of HL-60 cells, thus suggesting that GH plays a major role in the regulation of cell survival in the hemopoietic system, via an autocrine/paracrine mechanism.

Expression of growth hormone receptor in the human brain

This study was designed to investigate the presence of growth hormone receptor (GHR) expression in the human brain tissue, both normal and tumoral, as well as in the human glioblastoma cell line U87MG. Reverse transcription-polymerase chain reaction revealed the presence of GHR mRNA in all brain samples investigated and in U87MG cells. GHR immunoreactivity was also detected in this cell line using both immunocytochemistry and western blotting. All together, our data demonstrate the existence of GHR expression within the central nervous system (CNS), thus supporting a possible role for GH in the CNS physiology.

Activation of growth hormone receptor delivers an antiapoptotic signal: evidence for a role of Akt in this pathway

A signaling pathway was delineated by which GH promotes cell survival. Experiments were performed in human leukemic cells (HL-60) and Chinese hamster ovary (CHO) cells. In HL-60 cells, GH treatment reduced starvation-induced cell death. In contrast, when HL-60 cells were treated with an anti-GH antibody, cell survival was sharply reduced. In CHO cells stably expressing either the wild-type (wtGHR) or a truncated form (delta454GHR) of the GH receptor in which GH induces a sustained activation of the receptor-associated tyrosine kinase JAK2, we found that GH stimulation inhibited programmed cell death induced by withdrawal of survival factors. This effect was enhanced in cells expressing the truncated form. In contrast, GH did not affect cell survival in CHO cells transfected with either the empty vector or a mutated GHR unable to transduce the signal (4P/AGHR). We also showed that the inhibitory action of GH on apoptosis is probably mediated via stimulation of the serine-threonine kinase Akt, as 1) GH treatment induces a prompt phosphorylation of Akt; and 2) GH effects on cell survival are abolished by transfection of an Akt mutant that exhibits dominant negative function. Experiments with pharmacological inhibitors demonstrated that GH-induced Akt phosphorylation is dependent on phosphoinositide 3-kinase activation. In contrast, we found no changes in Bcl-2 levels secondary to GHR activation.

Salivary gland is capable of GH synthesis under GHRH stimulation

Twelve female rats weighing approximately 150 g received in the submaxillary gland a pellet capable of releasing 3.5 microg GHRH/h for 60 days. Another eight sex- and weight-matched animals received placebo pellets in the same place. After two months the animals were killed, heart blood was collected and pituitary and submaxillary glands were carefully dissected. Pituitary GH content in both placebo- and GHRH-treated animals showed similar values, but plasma GH and IGF-I levels were significantly lower in the animals carrying GHRH pellets (P<0.03); these animals also had a significantly higher GH content in the submaxillary gland (19.2+/-8 ng/mg protein) compared with the placebo-treated group (1.1+/-0.3 ng/mg protein). GH mRNA was present only in the submaxillary gland of GHRH-treated rats as determined by PCR-Southern blot and by in situ hybridization methods. It is concluded that high local GHRH levels are capable of inducing transdifferentiation in submaxillary gland cells to synthesize GH.

Correlation of Pit-1 gene expression and Pit-1 content with proliferation and differentiation in human myeloid leukemic cells

The transcription factor pituitary-1 (Pit-1) is a homeodomain-containing protein that is expressed mainly in the pituitary, where it drives the expression of growth hormone, prolactin, and thyroid-stimulating hormone beta chain genes. In addition, Pit-1 is required for adequate pituitary cell growth and may be involved in the pathogenesis of pituitary adenomas. Pit-1 expression has been also reported in nonpituitary tissues, where it might be involved in the control of cell proliferation. In order to elucidate such a possibility, we have investigated the changes in both Pit-1 mRNA and Pit-1 immunoreactivity in HL-60 cells following the addition of several differentiating agents. Our results show that while high Pit-1 levels are found in exponentially growing HL-60 cells, a significant decrease occurs after induction of cells to differentiate along the macrophage lineage with 12-O-tetradecanoylphorbol-13-acetate (TPA). In contrast no changes were observed when cells were treated with interferon-alpha, which also induces differentiation of HL-60 cells that, at odds with TPA, is not accompanied with growth arrest. In all, these findings suggest that Pit-1 expression is specifically associated with proliferation in HL-60 cells, thus supporting the idea that one of the functions of nonpituitary Pit-1 may be the control of cell proliferation.

Pattern of presentation of the human growth hormone variant (hGH-V) gene in the normal population

The human growth hormone variant (hGH-V) gene is a member of the GH gene family, expressed by the syncytiotrophoblast. Although its physiological role is poorly understood, certain data suggest that it may be involved in the control of fetal growth and development. As a first step to asses its physiological relevance, we investigated its degree of polymorphism in the normal population. Genetic studies have been difficult to carry out due to the high sequence identity among GH-family members. We overcame this problem by selectively amplifying a fragment of the hGH-V gene by PCR. DSCP analysis of the amplimers revealed a heterozygous pattern in one of the 64 subjects studied. Investigation of the subject's relatives showed a similar pattern in his father. In all, our results indicate that the hGH-V gene is highly conserved in the normal population.

Expression of the human growth hormone normal gene (hGH-N) in proliferating and differentiated HL-60 cells

The possibility that human leukemic cells could synthesize growth hormone (GH) was investigated in the HL-60 cell line. Western blot analysis of protein extracts obtained from these cells revealed the existence of a major immunoreactive GH (irGH) band, with an approximate molecular weight of 22 kDa, together with lower amounts of 20- and 44-kDa bands. Stimulating proliferating HL-60 cells with KCl clearly increased GH concentration in the incubation medium as compared to basal values. RT-PCR amplification of HL-60 RNA and restriction assay of the amplimers demonstrated that those proteins were the result of the expression of the GH-N (normal) gene in this cell line. These results were confirmed by Northern blot, which also showed that the rate of GH-N gene expression was clearly dependent upon the proliferative state of the cells: while GH transcripts were easily detectable in actively proliferating cells, only minute amounts were observed when cells were induced to differentiate with dimethyl sulphoxide (DMSO). Similar differences were observed by Western blot. In all, these findings demonstrate that HL-60 cells are capable to produce and secrete a GH identical to pituitary GH. Interestingly, the rate of synthesis of the hormone dramatically increases when cells are actively proliferating. Therefore, it is likely that locally produced GH might be involved in the control of leukemic cell proliferation. Further studies are now in course to establish whether this mechanism occurs via an autocrine and/or paracrine way.