The development of resistance to chemotherapeutic drugs is the main obstacle to the successful treatment of many cancers, including childhood neuroblastoma, the most common solid tumour of infants. One factor that may play a role in determining response of neuroblastoma tumours to therapeutic agents is the p53 tumour suppressor gene. A number of previous studies have suggested that this tumour suppressor protein is inactive in neuroblastoma due to its cytoplasmic sequestration. This thesis therefore has examined the functionality of p53 and its role in determining drug response of neuroblastoma cells. An initial study was undertaken that characterised an unusually broad multidrug resistance (MDR) phenotype of a neuroblastoma cell line (IMR/KAT100). The results demonstrated that the MDR phenotype of the IMR/KAT100 cells was associated with the acquisition of mutant p53. To explore the role of p53 in drug resistance further, p53-deficient variants in cell lines with wild-type p53 were generated by transduction of p53-suppressive constructs encoding either shRNA or a dominant-negative p53 mutant. Analysis of these cells indicated that: (i) in contrast to previous reports, wild-type p53 was fully functional in all neuroblastoma lines tested, as evidenced by its activation and nuclear translocation in response to DNA damage, transactivation of target genes and control of cell cycle checkpoints; (ii) inactivation of p53 in neuroblastoma cells resulted in establishment of an MDR phenotype; (iii) knockdown of mutant p53 did not revert the drug resistance phenotype, suggesting it is determined by loss of wild-type function rather than gain of mutant function; (iv) p53-dependent cell senescence, the primary response of S-type neuroblastoma cells to DNA damage, is replaced, after p53 inactivation, by mitotic catastrophe and subsequent apoptosis. In contrast to neuroblastoma, p53 suppression had no effect or increased drug susceptibility in several other tumour cell types, indicating the importance of tissue context for p53- mediated modulation of tumour cell sensitivity to treatment. Taken together, these data provide strong evidence for p53 having a role in mediating drug resistance in neuroblastoma and suggest that p53 status may be an important prognostic marker of treatment response in this disease.

<p>Neuroblastoma is a malignant childhood cancer, originating from sympathetic neuroblasts of the peripheral nervous system. Neuroblastoma is a heterogenous group of tumours, while some are highly malignant others can spontaneosly mature into a more benign form or regress. Less than half of the patients survive and this statistics has improved only modestly over the past 20 years. </p><p>SH-SY5Y is a human neuroblastoma cell line established from a highly malignant tumour. The cells have retained a capacity to differentiate <i>in vitro</i> in response to low concentrations of the phorbolester 12-O-tetradecanoylphorbol-13-acetate (TPA) in the presence of serum or defined growth factors. Differentiated cells are characterised by neurite formation and upregulation of neuronal marker genes. SH-SY5Y are unresponsive to nerve growth factor (NGF), but when transfected to express the NGF-receptor TrkA, they differentiate in response to NGF. Protein kinase C (PKC) is pivotal for the differentiation response to take place.</p><p>We have investigated the role of signaling through the Ras-MAPK pathway in differentiating SH-SY5Y, with respect to neurite formation, expression of neuronal marker genes and growth control. Our results show that differentiation-promoting treatment induced a sustained activation and nuclear accumulation of the MAPK ERK in SH-SY5Y. The nuclear accumulation of ERK was PKC-dependent. However, nuclear accumulation of ERK was not sufficient for a differentiation response to take place in these cells, but ERK activity was needed for the characteristic upregulation of <i>NPY</i> and <i>GAP-43</i> induced by TPA. ERK activity did not induce neurite formation, neither was it necessary for TPA-induced neurite formation. Instead, stimulation of a pathway distinct from MEK/ERK, but downstream of Ras, was needed for morphological differentiation. We could also show that differentiated cells still entered S-phase and that there was no correlation between expression of the CKI p21_cip1 (an ERK target), BrdU-incorporation or neurite formation. </p>

<p>Neuroblastoma is one of the most common solid cancers of early childhood. In Sweden, approximately 10-15 cases occur annually. The overall five-year neuroblastoma survival in Europe is approximately 45%. Since cancer treatment involves drugs with risks of side effects in the growing child, there is a need for more effective and less toxic drugs. One new approach in cancer treatment is inhibition of tumor angiogenesis, i.e., of new blood vessel growth into the tumor. An angiogenesis inhibitor may be combined with cytostatic drugs to enhance the efficacy. The aim of this study was to investigate how drugs could be used to inhibit angiogenesis and tumor growth in a xenograft model of human neuroblastoma in nude mice. </p><p>The tumors express the angiogenesis stimulator vascular endothelial growth factor (VEGF) on both protein and mRNA levels. The angiogenesis inhibitors SU5416 (an inhibitor of VEGF signalling) and TNP-470 (an inhibitor of endothelial cell proliferation) inhibited angiogenesis in our model. TNP-470, however, inhibited angiogenesis without significant reduction of the tumor growth, in contrast to SU5416. </p><p>We also discovered that the cytostatic drug CHS 828 could cause regression of neuroblastoma tumors in the model when given orally at a low daily dose, alone or in combination with the angiogenesis inhibitor SU5416 or TNP-470. </p><p>Furthermore, a new use of the cardiac glycoside digoxin was found. Digoxin inhibited FGF-2 -stimulated bovine capillary endothelial cell growth in vitro, and inhibited angiogenesis in vivo in the chick chorioallantoic membrane assay (CAM). It also inhibited neuroblastoma growth by approximately 50% in our neuroblastoma model. </p><p>In conclusion, CHS 828 and digoxin represent two classes of drugs with potent antitumor effects that may be valuable in treatment of neuroblastoma, either alone or in combination with angiogenesis inhibitors.</p>

Neuroblastoma is a malignant childhood cancer, originating from sympathetic neuroblasts of the peripheral nervous system. Neuroblastoma is a heterogenous group of tumours, while some are highly malignant others can spontaneosly mature into a more benign form or regress. Less than half of the patients survive and this statistics has improved only modestly over the past 20 years. SH-SY5Y is a human neuroblastoma cell line established from a highly malignant tumour. The cells have retained a capacity to differentiate in vitro in response to low concentrations of the phorbolester 12-O-tetradecanoylphorbol-13-acetate (TPA) in the presence of serum or defined growth factors. Differentiated cells are characterised by neurite formation and upregulation of neuronal marker genes. SH-SY5Y are unresponsive to nerve growth factor (NGF), but when transfected to express the NGF-receptor TrkA, they differentiate in response to NGF. Protein kinase C (PKC) is pivotal for the differentiation response to take place. We have investigated the role of signaling through the Ras-MAPK pathway in differentiating SH-SY5Y, with respect to neurite formation, expression of neuronal marker genes and growth control. Our results show that differentiation-promoting treatment induced a sustained activation and nuclear accumulation of the MAPK ERK in SH-SY5Y. The nuclear accumulation of ERK was PKC-dependent. However, nuclear accumulation of ERK was not sufficient for a differentiation response to take place in these cells, but ERK activity was needed for the characteristic upregulation of NPY and GAP-43 induced by TPA. ERK activity did not induce neurite formation, neither was it necessary for TPA-induced neurite formation. Instead, stimulation of a pathway distinct from MEK/ERK, but downstream of Ras, was needed for morphological differentiation. We could also show that differentiated cells still entered S-phase and that there was no correlation between expression of the CKI p21cip1 (an ERK target), BrdU-incorporation or neurite formation.

Neuroblastoma is one of the most common solid cancers of early childhood. In Sweden, approximately 10-15 cases occur annually. The overall five-year neuroblastoma survival in Europe is approximately 45%. Since cancer treatment involves drugs with risks of side effects in the growing child, there is a need for more effective and less toxic drugs. One new approach in cancer treatment is inhibition of tumor angiogenesis, i.e., of new blood vessel growth into the tumor. An angiogenesis inhibitor may be combined with cytostatic drugs to enhance the efficacy. The aim of this study was to investigate how drugs could be used to inhibit angiogenesis and tumor growth in a xenograft model of human neuroblastoma in nude mice. The tumors express the angiogenesis stimulator vascular endothelial growth factor (VEGF) on both protein and mRNA levels. The angiogenesis inhibitors SU5416 (an inhibitor of VEGF signalling) and TNP-470 (an inhibitor of endothelial cell proliferation) inhibited angiogenesis in our model. TNP-470, however, inhibited angiogenesis without significant reduction of the tumor growth, in contrast to SU5416. We also discovered that the cytostatic drug CHS 828 could cause regression of neuroblastoma tumors in the model when given orally at a low daily dose, alone or in combination with the angiogenesis inhibitor SU5416 or TNP-470. Furthermore, a new use of the cardiac glycoside digoxin was found. Digoxin inhibited FGF-2 -stimulated bovine capillary endothelial cell growth in vitro, and inhibited angiogenesis in vivo in the chick chorioallantoic membrane assay (CAM). It also inhibited neuroblastoma growth by approximately 50% in our neuroblastoma model. In conclusion, CHS 828 and digoxin represent two classes of drugs with potent antitumor effects that may be valuable in treatment of neuroblastoma, either alone or in combination with angiogenesis inhibitors.

BACKGROUND: Serum amyloid P component (SAP) is a glycoprotein that is universally found associated with different types of amyloid deposits. It has been suggested that it stabilizes amyloid fibrils and therefore protects them from proteolytic degradation. METHODOLOGY/PRINCIPAL FINDINGS: In this paper, we show that SAP binds not only to mature amyloid fibrils but also to early aggregates of amyloidogenic mutants of the plasma protein transthyretin (TTR). It does not inhibit fibril formation of TTR mutants, which spontaneously form amyloid in vitro at physiological pH. We found that SAP prevents cell death induced by mutant TTR, while several other molecules that are also known to decorate amyloid fibrils do not have such effect. Using a Drosophila model for TTR-associated amyloidosis, we found a new role for SAP as a protective factor in inhibition of TTR-induced toxicity. Overexpression of mutated TTR leads to a neurological phenotype with changes in wing posture. SAP-transgenic flies were crossed with mutated TTR-expressing flies and the results clearly confirmed a protective effect of SAP on TTR-induced phenotype, with an almost complete reduction in abnormal wing posture. Furthermore, we found in vivo that binding of SAP to mutated TTR counteracts the otherwise detrimental effects of aggregation of amyloidogenic TTR on retinal structure. CONCLUSIONS/SIGNIFICANCE: Together, these two approaches firmly establish the protective effect of SAP on TTR-induced cell death and degenerative phenotypes, and suggest a novel role for SAP through which the toxicity of early amyloidogenic aggregates is attenuated. / <p>Epub 2013 Feb 4.</p>

Objective: To evaluate the anti-tumor and histone deacetylase (HDAC) inhibitory activity of the dietary isothiocyanate, sulforaphane (SFN) in the paediatric cancer,neuroblastoma (NB). Materials and Methods: NB cell line (NUB-7), fibroblasts (FLF; negative control) and MCF-7 (positive control), were treated with SFN for up to 7 days and effects on growth, cytotoxicity, differentiation and tumorigenicity assessed. HDAC inhibition was determined by histone (H3/ H4) acetylation. Results: 10 μM SFN significantly decreased in vitro growth and survival of NUB-7 to 10.22 ± 0.71% (p < 0.001) with no significant effect on FLF. SFN induced G1, G2 and S phase cell cycle arrests and stimulated H3/H4 histone acetylation. SFN markedly decreased NUB-7 clonogenicity and tumorigenicity in vivo. Conclusion: Results suggest that low dose SFN reduces proliferation, survival and tumorigenicity of NB NUB-7. As a dietary factor of negligible intrinsic toxicity SFN is a promising therapeutic agent for the treatment of NB.

In an attempt to identify agents that specifically target neuroblastoma (NB) tumour-initiating cells (TIC) we performed drug screens using libraries of bioactive compounds. Cardiac glycosides (CGs) were the largest class of drugs identified with antitumour activity. At high CG doses inhibitory effects on the Na+/K+-ATPase induce cardiotoxicity; therefore, CG analogues were designed in an attempt to separate the effects on NB cells from cardiotoxicity. We identified RIDK34 as our lead compound from a structure-activity-relationship analysis (IC50 8 nM). RIDK34 contains a unique oxime group and shows increasing potency against NB TICs. The Na+/K+-ATPase is a target for the apoptotic activity of digoxin and RIDK34, whereby a signaling cascade involving Src and ERK may induce apoptosis. Furthermore, we predict that signaling activation does not require inactivation of the Na+/K+-ATPase and subsequent deregulation of [Na+]i and [K+]I gradients. Thus CGs and particularly RIDK34 may be expected to display diminished cardiotoxicity and greater therapeutic potential.

Objective: To evaluate the anti-tumor and histone deacetylase (HDAC) inhibitory activity of the dietary isothiocyanate, sulforaphane (SFN) in the paediatric cancer,neuroblastoma (NB). Materials and Methods: NB cell line (NUB-7), fibroblasts (FLF; negative control) and MCF-7 (positive control), were treated with SFN for up to 7 days and effects on growth, cytotoxicity, differentiation and tumorigenicity assessed. HDAC inhibition was determined by histone (H3/ H4) acetylation. Results: 10 μM SFN significantly decreased in vitro growth and survival of NUB-7 to 10.22 ± 0.71% (p < 0.001) with no significant effect on FLF. SFN induced G1, G2 and S phase cell cycle arrests and stimulated H3/H4 histone acetylation. SFN markedly decreased NUB-7 clonogenicity and tumorigenicity in vivo. Conclusion: Results suggest that low dose SFN reduces proliferation, survival and tumorigenicity of NB NUB-7. As a dietary factor of negligible intrinsic toxicity SFN is a promising therapeutic agent for the treatment of NB.

In an attempt to identify agents that specifically target neuroblastoma (NB) tumour-initiating cells (TIC) we performed drug screens using libraries of bioactive compounds. Cardiac glycosides (CGs) were the largest class of drugs identified with antitumour activity. At high CG doses inhibitory effects on the Na+/K+-ATPase induce cardiotoxicity; therefore, CG analogues were designed in an attempt to separate the effects on NB cells from cardiotoxicity. We identified RIDK34 as our lead compound from a structure-activity-relationship analysis (IC50 8 nM). RIDK34 contains a unique oxime group and shows increasing potency against NB TICs. The Na+/K+-ATPase is a target for the apoptotic activity of digoxin and RIDK34, whereby a signaling cascade involving Src and ERK may induce apoptosis. Furthermore, we predict that signaling activation does not require inactivation of the Na+/K+-ATPase and subsequent deregulation of [Na+]i and [K+]I gradients. Thus CGs and particularly RIDK34 may be expected to display diminished cardiotoxicity and greater therapeutic potential.