Different effects of TrkA expression in neuroblastoma cell lines with or without MYCN amplification

Related expression of TRKA and P75 receptors and the changing copy number of MYC-oncogenes determine the sensitivity of brain tumor cells to the treatment of the nerve growth factor in combination with cisplatin and temozolomide

Objectives Oncological diseases are an urgent medical and social problem. The chemotherapy induces not only the death of the tumor cells but also contributes to the development of their multidrug resistance and death of the healthy cells and tissues. In this regard, the search for the new pharmacological substances with anticancer activity against drug-resistant tumors is of utmost importance. In the present study we primarily investigated the correlation between the expression of TrkA and p75 receptors with the nerve growth factor (NGF) and cisplatin or temozolomide sensitivity of anaplastic astrocytoma (AA), glioblastoma (GB) and medulloblastoma (MB) cell cultures. We then evaluated the changing of copy numbers of MYCC and MYCN and its correlation with cytotoxicity index (CI) in MB cells under NGF exposition. Methods The primary cell cultures were obtained from the tumor biopsy samples of the patients with AA (n=5), GB (n=7) or MB (n=25) prior to radiotherapy and chemotherapy. The cytotoxicity effect of NGF and its combinations with cisplatin or temozolomide, the relative expression of TrkA and p75 receptors, its correlations with CI in AA, GB and MB primary cell cultures were studied by trypan blue cytotoxicity assay and immunofluorescence staining respectively. The effect of NGF on MYCC and MYCN copy numbers in MB cell cultures was studied by fluorescence in situ hybridization. Results We found that the expression of TrkA and p75 receptors (p=0.03) and its ratio (p=0.0004) depends on the sensitivity of AA and GB cells to treatment with NGF and its combinations with cisplatin or temozolomide. NGF reduces (p<0.05) the quantity of MB cells with six or eight copies of MYCN and three or eight copies of MYCC. Besides, NGF increases (p<0.05) the quantity of MB cells containing two copies of both oncogenes. The negative correlation (r=-0.65, p<0.0001) is established between MYCC average copy numbers and CI of NGF in MB cells. Conclusions The relative expression of NGF receptors (TrkA/p75) and its correlation with CI of NGF and its combinations in AA and GB cells point to the mechanism involving a cell death signaling pathway. NGF downregulates (p<0.05) some increased copy numbers of MYCC and MYCN in the human MB cell cultures, and upregulates normal two copies of both oncogenes (p<0.05).

Related expression of TRKA and P75 receptors and the changing copy number of MYC-oncogenes determine the sensitivity of brain tumor cells to the treatment of the nerve growth factor in combination with cisplatin and temozolomide

OBJECTIVES

Oncological diseases are an urgent medical and social problem. The chemotherapy induces not only the death of the tumor cells but also contributes to the development of their multidrug resistance and death of the healthy cells and tissues. In this regard, the search for the new pharmacological substances with anticancer activity against drug-resistant tumors is of utmost importance. In the present study we primarily investigated the correlation between the expression of TrkA and p75 receptors with the nerve growth factor (NGF) and cisplatin or temozolomide sensitivity of anaplastic astrocytoma (AA), glioblastoma (GB) and medulloblastoma (MB) cell cultures. We then evaluated the changing of copy numbers of MYCC and MYCN and its correlation with cytotoxicity index (CI) in MB cells under NGF exposition.

METHODS

The primary cell cultures were obtained from the tumor biopsy samples of the patients with AA (n=5), GB (n=7) or MB (n=25) prior to radiotherapy and chemotherapy. The cytotoxicity effect of NGF and its combinations with cisplatin or temozolomide, the relative expression of TrkA and p75 receptors, its correlations with CI in AA, GB and MB primary cell cultures were studied by trypan blue cytotoxicity assay and immunofluorescence staining respectively. The effect of NGF on MYCC and MYCN copy numbers in MB cell cultures was studied by fluorescence in situ hybridization.

RESULTS

We found that the expression of TrkA and p75 receptors (p=0.03) and its ratio (p=0.0004) depends on the sensitivity of AA and GB cells to treatment with NGF and its combinations with cisplatin or temozolomide. NGF reduces (p<0.05) the quantity of MB cells with six or eight copies of MYCN and three or eight copies of MYCC. Besides, NGF increases (p<0.05) the quantity of MB cells containing two copies of both oncogenes. The negative correlation (r=-0.65, p<0.0001) is established between MYCC average copy numbers and CI of NGF in MB cells.

CONCLUSIONS

The relative expression of NGF receptors (TrkA/p75) and its correlation with CI of NGF and its combinations in AA and GB cells point to the mechanism involving a cell death signaling pathway. NGF downregulates (p<0.05) some increased copy numbers of MYCC and MYCN in the human MB cell cultures, and upregulates normal two copies of both oncogenes (p<0.05).

TrkA is amplified in malignant melanoma patients and induces an anti-proliferative response in cell lines

BACKGROUND

The nerve growth factor (NGF) receptor tyrosine-kinase TrkA is a well-known determinant of the melanocytic lineage, through modulation of the MAPK and AKT cascades. While TrkA gene is frequently rearranged in cancers, its involvement in malignant melanoma (MM) development is still unclear.

METHODS

We analyzed a dataset of primary cutaneous MM (n = 31) by array comparative genomic hybridization (aCGH), to identify genomic amplifications associated with tumor progression. The analysis was validated by genomic quantitative PCR (qPCR) on an extended set of cases (n = 64) and the results were correlated with the clinical outcome. To investigate TrkA molecular pathways and cellular function, we generated inducible activation of the NGF-TrkA signaling in human MM cell lines.

RESULTS

We identified amplification of 1q23.1, where the TrkA locus resides, as a candidate hotspot implicated in the progression of MM. Across 40 amplicons detected, segmental amplification of 1q23.1 showed the strongest association with tumor thickness. By validation of the analysis, TrkA gene amplification emerged as a frequent event in primary melanomas (50 % of patients), and correlated with worse clinical outcome. However, experiments in cell lines revealed that induction of the NGF-TrkA signaling produced a phenotype of dramatic suppression of cell proliferation through inhibition of cell division and pronounced intracellular vacuolization, in a way straightly dependent on NGF activation of TrkA. These events were triggered via MAPK activity but not via AKT, and involved p21(cip1) protein increase, compatibly with a mechanism of oncogene-induced growth arrest.

CONCLUSIONS

Taken together, our findings point to TrkA as a candidate oncogene in MM and support a model in which the NGF-TrkA-MAPK pathway may mediate a trade-off between neoplastic transformation and adaptive anti-proliferative response.

Discovery and preclinical characterization of novel small molecule TRK and ROS1 tyrosine kinase inhibitors for the treatment of cancer and inflammation

Receptor tyrosine kinases (RTKs), in response to their growth factor ligands, phosphorylate and activate downstream signals important for physiological development and pathological transformation. Increased expression, activating mutations and rearrangement fusions of RTKs lead to cancer, inflammation, pain, neurodegenerative diseases, and other disorders. Activation or over-expression of ALK, ROS1, TRK (A, B, and C), and RET are associated with oncogenic phenotypes of their respective tissues, making them attractive therapeutic targets. Cancer cDNA array studies demonstrated over-expression of TRK-A and ROS1 in a variety of cancers, compared to their respective normal tissue controls. We synthesized a library of small molecules that inhibit the above indicated RTKs with picomolar to nanomolar potency. The lead molecule GTx-186 inhibited RTK-dependent cancer cell and tumor growth. In vitro and in vivo growth of TRK-A-dependent IMR-32 neuroblastoma cells and ROS1-overexpressing NIH3T3 cells were inhibited by GTx-186. GTx-186 also inhibited inflammatory signals mediated by NFκB, AP-1, and TRK-A and potently reduced atopic dermatitis and air-pouch inflammation in mice and rats. Moreover, GTx-186 effectively inhibited ALK phosphorylation and ALK-dependent cancer cell growth. Collectively, the RTK inhibitor GTx-186 has a unique kinase profile with potential to treat cancer, inflammation, and neuropathic pain.

Human intellectual disability genes form conserved functional modules in Drosophila

Intellectual Disability (ID) disorders, defined by an IQ below 70, are genetically and phenotypically highly heterogeneous. Identification of common molecular pathways underlying these disorders is crucial for understanding the molecular basis of cognition and for the development of therapeutic intervention strategies. To systematically establish their functional connectivity, we used transgenic RNAi to target 270 ID gene orthologs in the Drosophila eye. Assessment of neuronal function in behavioral and electrophysiological assays and multiparametric morphological analysis identified phenotypes associated with knockdown of 180 ID gene orthologs. Most of these genotype-phenotype associations were novel. For example, we uncovered 16 genes that are required for basal neurotransmission and have not previously been implicated in this process in any system or organism. ID gene orthologs with morphological eye phenotypes, in contrast to genes without phenotypes, are relatively highly expressed in the human nervous system and are enriched for neuronal functions, suggesting that eye phenotyping can distinguish different classes of ID genes. Indeed, grouping genes by Drosophila phenotype uncovered 26 connected functional modules. Novel links between ID genes successfully predicted that MYCN, PIGV and UPF3B regulate synapse development. Drosophila phenotype groups show, in addition to ID, significant phenotypic similarity also in humans, indicating that functional modules are conserved. The combined data indicate that ID disorders, despite their extreme genetic diversity, are caused by disruption of a limited number of highly connected functional modules.

Intellectual Disability (ID) affects 2% of our population and is associated with many different disorders. Although more than 400 causative genes (‘ID genes’) have been identified, their function remains poorly understood and the degree to which these disorders share a common molecular basis is unknown. Here, we systematically characterized behavioral and morphological phenotypes associated with 270 conserved ID genes, using the Drosophila eye and photoreceptor neurons as a model. These and follow up approaches generated previously undescribed genotype-phenotype associations for the majority (180) of ID gene orthologs, and identified, among others, 16 novel regulators of basal neurotransmission. Importantly, groups of genes that show the same phenotype in Drosophila are highly enriched in known connectivity, also share increased phenotypic similarity in humans and successfully predicted novel gene functions. In total, we mapped 26 conserved functional modules that together comprise 100 ID gene orthologs. Our findings provide unbiased evidence for the long suspected but never experimentally demonstrated functional coherence among ID disorders. The identified conserved functional modules may aid to develop therapeutic strategies that target genetically heterogeneous ID patients with a common treatment.

Expression of NTRK1/TrkA affects immunogenicity of neuroblastoma cells

High levels of the NTRK1/TrkA receptor are expressed in low-stage neuroblastomas, which are characterized by a good patient prognosis and often undergo spontaneous regression. In addition to apoptosis, tumor-immune responses might contribute to this regression. We hypothesized that TrkA expression might enhance the immune response to neuroblastomas. Immunohistochemistry on neuroblastoma tissue microarrays confirmed significantly higher lymphocyte infiltration in low-stage compared with high-stage tumors. Flow cytometry of human SH-SY5Y cells stably transfected with NTRK1/TrkA cDNA revealed significant upregulation of major histocompatibility complex (MHC) class I complexes on TrkA-expressing cells. Corresponding to this upregulation, T cell activity and cytoxicity was enhanced in the presence of SY5Y-TrkA cells or by medium conditioned by them, suggesting the existence of additional soluble factors stimulating the T cell response. Activation of natural killer (NK) cells was only increased in the presence of SY5Y-TrkA conditioned medium (CM) and not in co-culture assays, suggesting a dominant inhibitory effect of upregulated MHC class I as the primary NK cell escape mechanism of TrkA-expressing neuroblastomas. We reanalyzed gene expression data obtained from the cell culture model to identify additional genes involved in the TrkA-mediated modulation of immune responses. Upregulation of selected target genes in SY5Y-TrkA cells was confirmed on transcript and protein levels. However, none of the proteins were detected in medium conditioned by SY5Y-TrkA cells, arguing against these factors as soluble mediators of the TrkA-induced immune response. We here provide evidence that TrkA expression in neuroblastoma leads to an increased immunogenicity that may contribute to a less malignant phenotype and/or spontaneous regression of neuroblastoma cells.

Gene expression of TRK neurotrophin receptors in advanced neuroblastomas in Singapore--a pilot study

The clinical hallmark of neuroblastoma is heterogeneity. Biologically, ploidy and N-Myc amplification are currently the only 2 features used to define risk group and to determine therapy. Tyrosine kinase neurotrophin receptors (Trks, including TrkA, TrkB, and TrkC) are important in the clinical and biological behavior of neuroblastomas. The authors aim to study Trks gene expression in their local population of advanced neuroblastoma patients. Multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) assay on the expression of TrkA, TrkB, TrkB-truncated, and TrkC was performed on a total of 19 advanced neuroblastoma archival tumors, diagnosed in KK Women's and Children's Hospital between 2003 and 2007. Of the 19 tumors investigated, Trks expression was present in 14 (73.6%) cases. Of these cases, 8 (42.1%), 10 (52.6%), 7 (36.8%), and 6 (31.6%) expressed TrkA, TrkB, TrkB-truncated, and TrkC receptor mRNAs, respectively. Subsequently, the authors compared Trks expression with N-Myc amplification status of the 19 patients. N-Myc was amplified in 5 (26.3%) of the cases. Within the non-N-Myc-amplified group, Trks expression was present in 9 (64%) of the 14 cases. The significant expression of Trk isoforms among advanced neuroblastoma cases as evident from this study support their role as possible risk assessment tools alongside N-Myc amplification status.

The effect of P75 on Trk receptors in neuroblastomas

Neuroblastomas (NBs) with favorable outcome usually express TrkA, whereas unfavorable NBs frequently express TrkB and its cognate ligand BDNF. P75 (p75(LNTR), NGFR, TNFRSF16) binds NGF-related neurotrophins with low affinity and usually is coexpressed with Trk receptors in NBs. Here, we investigated the importance of p75 coexpression with Trk receptors in NBs. We transfected p75 into two Trk-null NB cell lines, SH-SY5Y and NLF that were also engineered to stably express TrkA or TrkB. Cell numbers were compared between single (Trk alone) and double (Trk+p75) transfectants, and proliferation was assessed by flow cytometry. P75 coexpression had little effect on cell growth in Trk NB cells in the absence of ligand, but it increased sensitivity and greatly enhanced the effect of cognate ligand. Exogenous NGF induced greater phosphorylation of TrkA and AKT. This was associated with increased cell number in TrkA/p75 cells compared to TrkA cells (p<0.01), which was due to increased proliferation in TrkA/p75 cells (p<0.05), followed by differentiation. Exogenous BDNF also increased cell number in TrkB/p75 compared to TrkB cells (p<0.01), due to an increase in proliferation, but without differentiation. Coexpression of p75 also increased specificity of Trk-expressing cells to ligand. NT3-induced phosphorylation of TrkA and AKT was reduced in TrkA/p75 cells. NT3-induced phosphorylation of TrkB (as well as AKT and MAPK) was also reduced with p75 coexpression. Our results suggest that p75 plays an important role in enhancing both the sensitivity of Trk receptors to low levels of ligand, as well as increasing the specificity of Trks to their cognate ligands. It also enhances ligand-induced differentiation in TrkA/p75 but not TrkB/p75 cells.

‘Cross-talk’ between Schwannian stroma and neuroblasts promotes neuroblastoma tumor differentiation and inhibits angiogenesis

Neuroblastoma (NB) tumors with abundant Schwannian stroma have a differentiated phenotype, low vascularity, and are associated with a favorable prognosis. These observations have led to the hypothesis that 'cross-talk' between Schwann cells and neuroblasts influences the biology and clinical behavior of NB tumors. In support of this hypothesis, laboratory studies have shown that factors secreted by Schwann cells are capable of promoting NB differentiation, inhibiting angiogenesis, and impairing NB growth. Recently, using a novel NB xenograft model that was designed to directly investigate the affects of infiltrating Schwann cells, we demonstrated that infiltrating mouse Schwann cells can directly impact the phenotype of human NB xenografts in vivo. Taken together, these studies indicate that tumor-stroma interactions are critical in determining the biology of NB tumors. Further research investigating the molecules involved in the 'cross-talk' between Schwann cells and neuroblasts may lead to new treatment strategies that will modify tumor biology and alter the clinically aggressive nature of Schwannian stroma-poor NB tumors.

Differences in gene expression profile among SH-SY5Y neuroblastoma subclones with different neurite outgrowth responses to nerve growth factor

Nerve growth factor (NGF) plays a key role in the differentiation of neurons. In this study, we established three NGF-induced neurite-positive (NIN+) subclones that showed high responsiveness to NGF-induced neurite outgrowth and three NGF-induced neurite-negative (NIN-) subclones that abolished NGF-induced neurite outgrowth from parental SH-SY5Y cells, and analyzed differences in the NGF signaling cascade. The NIN+ subclones showed enhanced responsiveness to FK506-mediated neurite outgrowth as well. To clarify the mechanism behind the high frequency of NGF-induced neurite outgrowth, we investigated differences in NGF signaling cascade among subclones. Expression levels of the NGF receptor TrkA, and NGF-induced increases in mRNAs for the immediate-early genes (IEGs) c-fos and NGF inducible (NGFI) genes NGFI-A, NGFI-B and NGFI-C, were identical among subclones. Microarray analysis revealed that the NIN+ cell line showed a very different gene expression profile to the NIN- cell line, particularly in terms of axonal vesicle-related genes and growth cone guidance-related genes. Thus, the difference in NGF signaling cascade between the NIN+ and NIN- cell lines was demonstrated by the difference in gene expression profile. These differentially expressed genes might play a key role in neurite outgrowth of SH-SY5Y cells in a region downstream from the site of induction of IEGs, or in a novel NGF signaling cascade.

The growth-inhibitory Ndrg1 gene is a Myc negative target in human neuroblastomas and other cell types with overexpressed N- or c-myc

A major prognostic marker for neuroblastoma (Nb) is N-myc gene amplification, which predicts a poor clinical outcome. We sought genes differentially expressed on a consistent basis between multiple human Nb cell lines bearing normal versus amplified N-myc, in hopes of finding target genes that might clarify how N-myc overexpression translates into poor clinical prognosis. Using differential display, we find the previously described growth-inhibitory gene Ndrg1 is strongly repressed in all tested Nb cell lines bearing N-myc amplification, as well as in a neuroepithelioma line with amplified c-myc. Overexpression of N-myc in non-amplified Nb cells leads to repression of Ndrg1, as does activation of an inducible c-myc transgene in fibroblasts. Conversely, N-myc downregulation in N-myc-amplified Nb cells results in re-expression of the Ndrg1, and stimuli known to induce Ndrg1 do so in Nb cells while simultaneously down-regulating N-myc. Relevant to these results, we demonstrate an in vitro interaction of Myc protein with the Ndrg1 core promoter. We also find that Ndrg1 levels increase dramatically during in vitro differentiation of two cell lines modeling neural and glial development, while c- and N-myc levels decline. Our results combined with previous information on the Ndrg1 gene product suggest that downregulation of this gene is an important component of N-Myc effects in neuroblastomas with poor clinical outcome. In support of this notion, we find that re-expression of Ndrg1 in high-Myc Nb cells results in smaller cells with reduced colony size in soft-agar assays, further underscoring the functional significance of this gene in human neuroblastoma cells.