Neuropeptide Y receptor Y5 as an inducible pro-survival factor in neuroblastoma: implications for tumor chemoresistance.

Neuroblastoma (NB) is a pediatric tumor of neural crest origin with heterogeneous phenotypes. Although low-stage tumors carry a favorable prognosis, >50% of high-risk NB relapses after treatment with a fatal outcome. Thus developing therapies targeting refractory NB remains an unsolved clinical problem. Brain-derived neurotrophic factor (BDNF) and its TrkB receptor are known to protect NB cells from chemotherapy-induced cell death, while neuropeptide Y (NPY), acting via its Y2 receptor (Y2R), is an autocrine proliferative and angiogenic factor crucial for maintaining NB tumor growth. Here we show that in NB cells, BDNF stimulates the synthesis of NPY and induces expression of another one of its receptors, Y5R. In human NB tissues, the expression of NPY and Y5R positively correlated with the expression of BDNF and TrkB. Functionally, BDNF triggered Y5R internalization in NB cells, whereas Y5R antagonist inhibited BDNF-induced p44/42 mitogen-activated protein kinase activation and its pro-survival activity. These observations suggested TrkB-Y5R transactivation that resulted in cross-talk between their signaling pathways. Additionally, NPY and Y5R were upregulated in a BDNF-independent manner in NB cells under pro-apoptotic conditions, such as serum deprivation and chemotherapy, as well as in cell lines and tissues derived from posttreatment NB tumors. Blocking Y5R in chemoresistant NB cells rich in this receptor sensitized them to chemotherapy-induced apoptosis and inhibited their growth in vivo by augmenting cell death. In summary, the NPY/Y5R axis is an inducible survival pathway activated in NB by BDNF or cellular stress. Upon such activation, Y5R augments the pro-survival effect of BDNF via its interactions with TrkB receptor and exerts an additional BDNF-independent anti-apoptotic effect, both of which contribute to NB chemoresistance. Therefore, the NPY/Y5R pathway may become a novel therapeutic target for patients with refractory NB, thus far an incurable form of this disease.

Neuropeptide Y and its Y2 receptor: potential targets in neuroblastoma therapy.

Neuroblastomas are pediatric tumors that develop from sympathetic precursors and express neuronal proteins, such as neuropeptide Y (NPY). NPY is a sympathetic neurotransmitter acting via multiple receptors (Y1-Y5R). Both NPY and Y2Rs are commonly expressed in neuroblastoma cell lines and tissues. The peptide secreted from neuroblastomas stimulates tumor cell proliferation and angiogenesis. As both processes are Y2R-mediated, the aim of this study was to assess Y2R as a potential therapeutic target for neuroblastoma. In vitro, Y2R antagonist (BIIE0246) prevented activation of p44/42 mitogen-activated protein kinase (MAPK) induced by endogenous NPY, which resulted in decreased proliferation and induction of Bim-mediated apoptosis. Similar growth-inhibitory effects were achieved with NPY small interfering RNA (siRNA) and Y2R siRNA. In vivo, Y2R antagonist significantly inhibited growth of SK-N-BE(2) and SK-N-AS xenografts, which was associated with decreased activation of p44/42 MAPK, as well as reduced proliferation (Ki67) and increased apoptosis (TdT-mediated dUTP nick end labeling; TUNEL). The Y2R antagonist also exerted an antiangiogenic effect. In vitro, it reduced the proliferation of endothelial cells induced by neuroblastoma-conditioned media. Consequently, the Y2R antagonist-treated xenografts had decreased vascularization and a high degree of focal fibrosis. In human neuroblastoma tissues, the expression of Y2R was observed in both tumor and endothelial cells, while NPY was predominantly expressed in neuroblastoma cells. In summary, Y2R is a promising new target for neuroblastoma therapy affecting both cancer cells and tumor vasculature.

Simultaneous high-performance liquid chromatographic stability-indicating analysis of acetaminophen, codeine phosphate, and sodium benzoate in elixirs.

A stability-indicating high-performance liquid chromatographic method has been developed for the simultaneous determination of acetaminophen, codeine phosphate and sodium benzoate in an elixir formulation. The reversed-phase paired-ion method utilizes UV detection at 214 nm, a C18 column at 50 degrees C and requires ca. 10 min per analysis. The method has been validated for use with elixirs containing 120 mg of acetaminophen, 12 mg of codeine phosphate and 7.5 mg sodium benzoate preservative per 5 ml. The known potential degradation products p-aminophenol, codeine N-oxide and codeinone are separated for quantitation simultaneous with the parent compounds. The method has been shown to be linear, reproducible, specific, sensitive and rugged.

Simultaneous high-performance liquid chromatographic stability-indicating analysis of acetaminophen and codeine phosphate in tablets and capsules.

A high-performance liquid chromatographic method has been developed for the simultaneous determination of acetaminophen and codeine phosphate for product stability studies, and release and dissolution testing of tablets and capsules. The reversed-phase method utilizes UV detection at 214 nm, a C18 column and requires a maximum of 10 min per analysis. The method has been validated for use with products containing as much as 500 mg of acetaminophen and as little as 7.5 mg of codeine phosphate. The known potential degradation products, p-aminophenol, codeine N-oxide, and codeinone are separated for quantitation simultaneous with the parent compounds. The method has been shown to be linear, reproducible, specific, sensitive and rugged.

Transbronchial mucus transfer of bronchogenic carcinoma.

The metastatic transfer of cells from a primary bronchogenic carcinoma to other portions of the lung as a result of mucus embolization and inoculation has been demonstrated. Histologic observations indicate tumor implantation and survival in peripheral bronchioles. In these regions mucosal dysplasia and carcinoma-in-situ changes which characteristically accompany a primary lesion are notably absent. Morphologic changes associated with acute bronchitis and focally denuded bronchial mucosa may be implicated.

Cyclic changes in the cell surface. I. Change in thymidine transport and its inhibition by cytochalasin B in Chinese hamster ovary cells.

Cytochalasin B (CB) shows a marked concentration-dependent inhibition of the incorporation of [(3)H]thymidine into Chinese hamster ovary cells. This inhibition was shown to result from an inhibition of thymidine uptake, not from an inhibition of DNA synthesis. Cells normally acquire the capacity to transport thymidine as they move from the G1 stage of the cell cycle into the S phase. If CB is added to cells while they are in G1, they do not acquire the ability to transport thymidine as they enter S. However, the addition of CB to cells that are already in S has no effect on their ability to transport thymidine. These results are discussed in terms of a model in which elements involved in thymidine transport enter the cell surface membrane as the cells move from G1 to S. It is proposed that CB prevents this structural transition by binding to the cell surface.

Cyclic changes in the cell surface. II. The effect of cytochalasin B on the surface morphology of synchronized Chinese hamster ovary cells.

The surface morphology of Chinese hamster ovary cells treated with cytochalasin B (CB) has been examined using the scanning electron microscope. The cells respond to treatment with CB by retracting peripheral processes, rounding up, and assuming a smooth or gently convoluted surface. This response occurs within minutes. Cells in different stages of the cell cycle all respond in a similar manner. When CB is removed from treated cells by washing with conditioned medium, the cells regain their normal surface conformation within minutes. The surface topography of these released cells is characteristic of their stage in the cell cycle. Because CB causes an alteration in the morphology of the cell surface and because of the speed of the response and recovery, it is proposed that the primary site of action of CB is the cell surface.

The effect of cell-to-cell contact on the surface morphology of Chinese hamster ovary cells.

In the previous report (Porter et al., in this issue) morphological changes in Chinese hamster ovary (CHO) cells during the cell cycle were described. In this report we describe the role of intercellular contact on these changes. We find that intercellular contact is required for cells to exhibit the morphologies Porter et al. described for S and G(2). When cells are synchronized by mitotic selection and plated onto cover slips at very low density such that no intercellular contact occurs, the cells remain in a G(1) configuration (rounded and highly blebbed through G(1), S, and G(2)). This G(1) morphology is also observed in nonsynchronized log phase cells plated at low densities and allowed to grow for several generations. The addition of conditioned medium from confluent cultures does not induce low density cells to change morphology during the cell cycle. These results indicate that extensive intercellular contact is required for the complete expression of the morphological changes associated with the cell cycle (as described by Porter et al.). It is concluded that although classic contact inhibition of movement and of growth may be absent in this transformed cell line, some contact-dependent response persists.

Alteration of nucleoside transport of Chinese hamster cells by dibutyryl adenosine 3':5'-cyclic monophosphate.

Cultured Chinese hamster ovary cells showed no significant change in generation time or fraction in the S-phase in the presence of 1 mM N(6),O(2')-dibutyryl adenosine 3':5'-cyclic monophosphate. Growth continued for at least two generations after expression of the morphological transformation induced by this cyclic AMP analog. Despite identical growth rates, apparent rates of DNA and RNA synthesis (incorporation of [(3)H]-thymidine or [(3)H]uridine) were reduced up to 15-fold in log phase by 1 mM cyclic nucleotide. [(3)H]Deoxycytidine incorporation was much less sensitive to dibutyryl cyclic AMP. Uptake studies with [(3)H]thymidine demonstrated an inhibition of transport rate dependent on the concentration of dibutyryl cyclic AMP in the growth medium. The rate of thymidine uptake at 1 degrees was decreased 21-fold by 1 mM cyclic nucleotide; half-maximal inhibition occurred at 6 muM. At 37 degrees , the pool size of acid-soluble thymidylate was strongly reduced by 1 mM cyclic nucleotide, and synergistic reduction of the pool size was found with 0.5 mM aminophylline. Phosphorylation of the acid-soluble intracellular label was unaffected by dibutyryl cyclic AMP. Inhibition of thymidine uptake is attributed to an observed decrease in thymidine kinase activity caused by growth in 1 mM dibutyryl cyclic AMP, and possibly to a simultaneous alteration in membrane permeability. Kinase-facilitated uptake of other metabolites may be regulated in a similar fashion by cyclic AMP.