Manuela Marra

The biological functions of polyamine oxidation products by amine oxidases: perspectives of clinical applications.

Summary.The polyamines spermine, spermidine and putrescine are ubiquitous cell components. If they accumulate excessively within the cells, due either to very high extracellular concentrations or to deregulation of the systems which control polyamine homeostasis, they can induce toxic effects. These molecules are substrates of a class of enzymes that includes monoamine oxidases, diamine oxidases, polyamine oxidases and copper containing amine oxidases. Polyamine concentrations are high in growing tissues such as tumors. Amine oxidases are important because they contribute to regulate levels of mono- and polyamines. These enzymes catalyze the oxidative deamination of biogenic amines and polyamines to generate the reaction products H2O2 and aldehyde(s) that are able to induce cell death in several cultured human tumor cell lines. H2O2 generated by the oxidation reaction is able to cross the inner membrane of mitochondria and directly interact with endogenous molecules and structures, inducing an intense oxidative stress. Since amine oxidases are involved in many crucial physiopathological processes, investigations on their involvement in human diseases offer great opportunities to enter novel classes of therapeutic agents.

Role of the lung resistance-related protein (LRP) in the drug sensitivity of cultured tumor cells.

Drug resistance, one of the major obstacle in the successful anticancer therapy, can be observed at the outset of therapy (intrinsic resistance) or after exposure to the antitumor agent (acquired resistance). To gain a better insight into the mechanisms of intrinsic resistance we have analyzed two human cell types derived from untreated tumors: MCF-7 breast cancer and A549 non small cell lung cancer (NSCLC). We have examined: the cytotoxic effect induced by doxorubicin (DOX); the time course of drug accumulation by flow cytometry and intracellular drug distribution by confocal microscopy; the expression and distribution of proteins related to anthracycline resistance, such as P-gp (P-glycoprotein), MRP1 (multidrug resistance-associated protein) and LRP (lung resistance-related protein). The cytotoxicity assays showed that A549 cells were less sensitive than MCF-7 cells to the DOX treatment in agreement with the different DOX uptake. Moreover, while in A549 cells DOX was mostly located in well defined intracytoplasmic vesicles, in MCF-7 cells it was mainly revealed inside the nuclei. The analysis of P-gp and MRP expression did not show significant differences between the two cell lines while a high expression of LRP was detected at the nuclear envelope and cytoplasmic levels in A549 cells. These findings suggest that the lower sensitivity to DOX treatment showed by lung carcinoma cells could be ascribed to drug sequestration by LRP inside the cytoplasmic compartments.

Enzymatic oxidation products of spermine induce greater cytotoxic effects on human multidrug-resistant colon carcinoma cells (LoVo) than on their wild-type counterparts

The occurrence of resistance to cytotoxic agents in tumor cells, associated with several phenotypic alterations, is one of the major obstacles to successful anticancer chemotherapy. A new strategy to overcome MDR of human cancer cells was studied, using BSAO, which generates cytotoxic products from spermine, H2O2 and aldehyde(s). The involvement of these products in causing cytotoxicity was investigated in both drug‐sensitive (LoVo WT) and drug‐resistant (LoVo DX) colon adenocarcinoma cells. Evaluation of clonogenic cell survival showed that LoVo DX cells are more sensitive than LoVo WT cells. Fluorometric assay and treatments performed in the presence of catalase demonstrated that the cytotoxicity was due mainly to the presence of H2O2. Cytotoxicity was eliminated in the presence of both catalase and ALDH. Transmission electron microscopic observations showed more pronounced mitochondrial modifications in drug‐resistant than in drug‐sensitive cells. Mitochondrial functionality studies performed by flow cytometry after JC‐1 labeling revealed basal hyperpolarization of the mitochondrial membrane in LoVo DX cells. After treatment with BSAO and spermine, earlier and higher mitochondrial membrane depolarization was found in LoVo DX cells than in drug‐sensitive cells. In addition, higher basal ROS production in LoVo DX cells than in drug‐sensitive cells was detected by flow‐cytometric analysis, suggesting increased mitochondrial activity in drug‐resistant cells. Our results support the hypothesis that mitochondrial functionality affects the sensitivity of cells to the cytotoxic enzymatic oxidation products of spermine, which might be promising anticancer agents, mainly against drug‐resistant tumor cells.

The plant alkaloid voacamine induces apoptosis-independent autophagic cell death on both sensitive and multidrug resistant human osteosarcoma cells.

In our previous studies, the bisindolic alkaloid voacamine (VOA), isolated from the plant Peschiera fuchsiaefolia, proved to exert a chemosensitizing effect on cultured multidrug resistant (MDR) osteosarcoma cells exposed to doxorubicin (DOX). In particular, VOA was capable of inhibiting P-glycoprotein action in competitive way, thus explaining the enhancement of the cytotoxic effect induced by DOX on MDR cells. Afterwards, preliminary observations suggested that such an enhancement did not involve the apoptotic process but was rather due to the induction of autophagic cell death. The results of the present investigation demonstrate that the plant alkaloid VOA is an autophagy inducer able to exert apoptosis-independent cytotoxic effect on both wild type and MDR tumor cells. In fact, under treatment condition causing about 50% of cell death, no evidence of apoptosis could be revealed by microscopical observations, Annexin V-FITC labeling and analysis of PARP cleavage, whereas the same cells underwent apoptosis when treated with apoptosis inducers, such as doxorubicin and staurosporine. Conversely, VOA-induced autophagy was clearly evidentiated by electron microscopy observations, monodansylcadaverine staining, LC3 expression and conversion. These results were confirmed by the analysis of the modulating effects of the pretreatment with autophagy inhibitors prior to VOA administration. In addition, transfection of osteosarcoma cells with siRNA against ATG genes reduced VOA cytotoxicity. In conclusion, considering the very debated dual role of autophagy in cancer cells (protective or lethal, pro- or anti-apoptotic) our findings seem to demonstrate, at least in vitro, that a natural product able to induce autophagy can be effective against drug resistant tumors, either used alone or in association with conventional chemotherapeutics.

2p15-p16.1 microdeletions encompassing and proximal to BCL11A are associated with elevated HbF in addition to neurologic impairment

Elevated fetal hemoglobin (HbF) ameliorates the clinical severity of hemoglobinopathies such as β-thalassemia and sickle cell anemia. Currently, the only curative approach for individuals under chronic transfusion/chelation support therapy is allogeneic stem cell transplantation. However, recent analyses of heritable variations in HbF levels have provided a new therapeutic target for HbF reactivation: the transcriptional repressor BCL11A. Erythroid-specific BCL11A abrogation is now actively being sought as a therapeutic avenue, but the specific impact of such disruption in humans remains to be determined. Although single nucleotide polymorphisms in BCL11A erythroid regulatory elements have been reported, coding mutations are scarcer. It is thus of great interest that patients have recently been described with microdeletions encompassing BCL11A. These patients display neurodevelopmental abnormalities, but whether they show increased HbF has not been reported. We have examined the hematological phenotype, HbF levels, and erythroid BCL11A expression in 3 such patients. Haploinsufficiency of BCL11A induces only partial developmental γ-globin silencing. Of greater interest is that a patient with a downstream deletion exhibits reduced BCL11A expression and increased HbF. Novel erythroid-specific regulatory elements in this region may be required for normal erythroid BCL11A expression, whereas loss of separate elements in the developing brain may explain the neurological phenotype.

Mitochondrial alterations induced by serum amine oxidase and spermine on human multidrug resistant tumor cells

Summary.Multidrug resistance (MDR) has been studied extensively because it is one of major problems in cancer chemotherapy. The MDR phenotype is often due to overexpression of P-glycoprotein (P-gp), that acting as an energy-dependent drug efflux pump exports various anticancer drugs out of cells. The major goal of our investigation is to establish whether bovine serum amine oxidase (BSAO), which generates the products H2O2 and aldehyde(s), from the polyamine spermine, is able to overcome MDR of human cancer cells. The cytotoxicity of the products was evaluated in both drug-sensitive (LoVo WT) and drug-resistant (LoVo DX) colon adenocarcinoma cells. A clonogenic cell survival assay demonstrated that LoVo DX cells were more sensitive than LoVo WT cells. Exogenous catalase protected cells against cytotoxicity mainly due to the formation of H2O2. However, spermine-derived aldehyde(s) still induced some cytotoxicity. The cytotoxic effect was totally inhibited in the presence of both enzymes, catalase and NAD-dependent aldehyde dehydrogenase (ALDH). Transmission electron microscopy investigations showed that BSAO and spermine induced evident mitochondria alterations, more pronounced in MDR than in LoVo WT cells. The mitochondrial activity was checked by flow cytometry studies, labelling cells with the probe JC1, that displayed a basal hyperpolarized status of the mitochondria in multidrug-resistant cells. After treatment with amine oxidase in the presence of polyamine-spermine, the cells showed a marked increase in mitochondrial membrane depolarization higher in LoVo DX than in LoVo WT cells. Our findings suggest that toxic oxidation products formed from spermine and BSAO could be a powerful tool in the development of new anticancer treatments, mainly against MDR tumor cells.

CD14+ cells from peripheral blood positively regulate hematopoietic stem and progenitor cell survival resulting in increased erythroid yield

Expansion of erythroblasts from human peripheral blood mononuclear cells is 4- to 15-fold more efficient than that of CD34+ cells purified from peripheral blood mononuclear cells. In addition, purified CD34+ and CD34− populations from blood do not reconstitute this erythroid yield, suggesting a role for feeder cells present in blood mononuclear cells that increase hematopoietic output. Immunodepleting peripheral blood mononuclear cells for CD14+ cells reduced hematopoietic stem and progenitor cell expansion. Conversely, the yield was increased upon co-culture of CD34+ cells with CD14+ cells (full contact or transwell assays) or CD34+ cells re-constituted in conditioned medium from CD14+ cells. In particular, CD14++CD16+ intermediate monocytes/macrophages enhanced erythroblast outgrowth from CD34+ cells. No effect of CD14+ cells on erythroblasts themselves was observed. However, 2 days of co-culturing CD34+ and CD14+ cells increased CD34+ cell numbers and colony-forming units 5-fold. Proliferation assays suggested that CD14+ cells sustain CD34+ cell survival but not proliferation. These data identify previously unrecognized erythroid and non-erythroid CD34− and CD34+ populations in blood that contribute to the erythroid yield. A flow cytometry panel containing CD34/CD36 can be used to follow specific stages during CD34+ differentiation to erythroblasts. We have shown modulation of hematopoietic stem and progenitor cell survival by CD14+ cells present in peripheral blood mononuclear cells which can also be found near specific hematopoietic niches in the bone marrow.

Three cases of rare salivary gland tumours: a molecular study of TP53, CDKN2A/ARF, RAS, BRAF, PTEN, MAPK2 and EGFR genes.

Salivary gland tumours are rare tumours characterized by histopathologic complexity and a wide variety of morphologic features. Studies on genetic changes in different histological subtypes of salivary gland tumours are important to better understand molecular pathogenetic mechanisms and to identify diagnostic and prognostic markers. Data are even more scanty dealing with unusual subtypes of these tumours. The aim of the present study was to analyse two high grade transformation adenoid cystic carcinomas (hgACC) and one hybrid tumour in order to identify, by mutational and microsatellite analysis, genetic alterations in TP53, CDKN2A/ARF, RAS, BRAF, PTEN, MAPK2 and EGFR genes. The two hgACCs showed snps missense in RAS genes and alterations with allelic instability in CDKN2A/ARF; moreover, a double mutation in TP53 was detected in one case. The hybrid tumour showed alterations in CDKN2A/ARF gene and snps missense in NRAS genes. Our data suggest that CDKN2A/ARF pathway might be involved in pathogenesis of the salivary gland tumours analysed. Further molecular analyses of these very rare tumours are necessary to better understand the role of other genetic alterations detected in our study.

The thrombopoietin/MPL axis is activated in the Gata1low mouse model of myelofibrosis and is associated with a defective RPS14 signature

Myelofibrosis (MF) is characterized by hyperactivation of thrombopoietin (TPO) signaling, which induces a RPS14 deficiency that de-regulates GATA1 in megakaryocytes by hampering its mRNA translation. As mice carrying the hypomorphic Gata1low mutation, which reduces the levels of Gata1 mRNA in megakaryocytes, develop MF, we investigated whether the TPO axis is hyperactive in this model. Gata1low mice contained two times more Tpo mRNA in liver and TPO in plasma than wild-type littermates. Furthermore, Gata1low LSKs expressed levels of Mpl mRNA (five times greater than normal) and protein (two times lower than normal) similar to those expressed by LSKs from TPO-treated wild-type mice. Gata1low marrow and spleen contained more JAK2/STAT5 than wild-type tissues, an indication that these organs were reach of TPO-responsive cells. Moreover, treatment of Gata1low mice with the JAK inhibitor ruxolitinib reduced their splenomegaly. Also in Gata1low mice activation of the TPO/MPL axis was associated with a RSP14 deficiency and a discordant microarray ribosome signature (reduced RPS24, RPS26 and SBDS expression). Finally, electron microscopy revealed that Gata1low megakaryocytes contained poorly developed endoplasmic reticulum with rare polysomes. In summary, Gata1low mice are a bona fide model of MF, which recapitulates the hyperactivation of the TPO/MPL/JAK2 axis observed in megakaryocytes from myelofibrotic patients.

P‐Selectin Sustains Extramedullary Hematopoiesis in the Gata1low Model of Myelofibrosis

Splenomegaly is a major manifestation of primary myelofibrosis (PMF) contributing to clinical symptoms and hematologic abnormalities. The spleen from PMF patients contains increased numbers of hematopoietic stem cells (HSC) and megakaryocytes (MK). These MK express high levels of P‐selectin (P‐sel) that, by triggering neutrophil emperipolesis, may cause TGF‐β release and disease progression. This hypothesis was tested by deleting the P‐sel gene in the myelofibrosis mouse model carrying the hypomorphic Gata1low mutation that induces megakaryocyte abnormalities that recapitulate those observed in PMF. P‐selnullGata1low mice survived splenectomy and lived 3 months longer than P‐selWTGata1low littermates and expressed limited fibrosis and osteosclerosis in the marrow or splenomegaly. Furthermore, deletion of P‐sel disrupted megakaryocyte/neutrophil interactions in spleen, reduced TGF‐β content, and corrected the HSC distribution that in Gata1low mice, as in PMF patients, is abnormally expanded in spleen. Conversely, pharmacological inhibition of TGF‐β reduced P‐sel expression in MK and corrected HSC distribution. Spleens, but not marrow, of Gata1low mice contained numerous cKITpos activated fibrocytes, probably of dendritic cell origin, whose membrane protrusions interacted with MK establishing niches hosting immature cKITpos hematopoietic cells. These activated fibrocytes were not detected in spleens from P‐selnullGata1low or TGF‐β‐inhibited Gata1low littermates and were observed in spleen, but not in marrow, from PMF patients. Therefore, in Gata1low mice, and possibly in PMF, abnormal P‐sel expression in MK may mediate the pathological cell interactions that increase TGF‐β content in MK and favor establishment of a microenvironment that supports myelofibrosis‐related HSC in spleen. Stem Cells 2016;34:67–82