Downregulation of the PHLDA1 gene in IMR-32 neuroblastoma cells increases levels of Aurora A, TRKB and affects proteins involved in apoptosis and autophagy pathways
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We have recently shown that mRNA and protein of PHLDA1 (pleckstrin-homology-like domain family A, member 1) were by far the most upregulated molecules upon treatment of IMR-32 cells with the anti-GD2 ganglioside monoclonal antibody 14G2a. Hence, we decided to study functions of PHLDA1 using human neuroblastoma IMR-32 cells as a model. Here, we show that constitutive expression of mRNA and protein of the PHLDA1 gene in IMR-32 cells was inversely correlated with transcript of the AURKA gene and Aurora A oncoprotein. Next, we silenced PHLDA1 expression in IMR-32 cells using an shRNA interference method. We report that IMR-32 cells with stable downregulation of PHLDA1 showed enhanced cellular ATP levels and an increase in mitochondrial membrane potential, as compared to control and non-transduced cells. We demonstrated that downregulation of PHLDA1 leads to a significant increase in expression of Aurora A and TRKB that are markers of poor prognosis in neuroblastoma. Also, we measured an increase in Aurora A and Akt kinases phosphorylation in the cells. Most importantly, PHLDA1-silenced cells were less susceptible to apoptosis than control cells, as shown by the lower expression of cleaved caspase-3 and PARP as well as a decreased activity of caspase-3 and -7. Our study negatively correlates expression of PHLDA1 and Aurora A in IMR-32 cells and sheds new light on functions of PHLDA1 in the neuroblastoma tumor cells, suggesting its role as a pro-apoptotic protein. Additionally, our results show possible links of the protein to regulation of features of mitochondria and formation of autophagosomes.Purpose:MYCN is one of the most well-characterized genetic markers of neuroblastoma. However, the mechanisms as to how MYCN mediate neuroblastoma tumorigenesis are not fully clear. Increasing evidence has confirmed that the dysregulation of miRNAs is involved in MYCN-mediated neuroblastoma tumorigenesis, supporting their potential as therapeutic targets for neuroblastoma. Although miR-221 has been reported as one of the upregulated miRNAs, the interplay between miR-221 and MYCN-mediated neuroblastoma progression remains largely elusive.Experimental Design: The expression of miR-221 in the formalin-fixed, paraffin-embedded tissues from 31 confirmed patients with neuroblastoma was detected by locked nucleic acid-in situ hybridization and qRT-PCR. The correlation between miR-221 expression and clinical features in patients with neuroblastoma was assessed. The mechanisms as to how miR-221 regulate MYCN in neuroblastoma were addressed. The effect of miR-221 on cellular proliferation in neuroblastoma was determined both in vitro and in vivoResults: miR-221 was significantly upregulated in neuroblastoma tumor cells and tissues that overexpress MYCN, and high expression of miR-221 was positively associated with poor survival in patients with neuroblastoma. Nemo-like kinase (NLK) as a direct target of miR-221 in neuroblastoma was verified. In addition, overexpression of miR-221 decreased LEF1 phosphorylation but increased the expression of MYCN via targeting of NLK and further regulated cell cycle, particularly in S-phase, promoting the growth of neuroblastoma cells.Conclusions: This study provides a novel insight for miR-221 in the control of neuroblastoma cell proliferation and tumorigenesis, suggesting potentials of miR-221 as a prognosis marker and therapeutic target for patients with MYCN overexpressing neuroblastoma. Clin Cancer Res; 23(11); 2905-18. ©2016 AACR.
Pediatric cancer
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Neuroblastoma is a pediatric malignant tumor of the postganglionic sympathetic nervous system that usually develops in the adrenal gland or in nonadrenal abdominal or thoracic sites.[1] It is the most common malignancy in infants and the most common extracranial solid tumor of childhood, with approximately 650 cases diagnosed annually in the United States.[2] The dramatic age-related survival differences among neuroblastoma patients with a similar tumor stage emphasize the heterogeneity of neuroblastoma pathobiology. Early research efforts to understand the pathobiology of neuroblastoma[3-5] and the significant progress made in neuroblastoma molecular biology[6] have informed the clinical treatment of neuroblastoma.
Solid tumor
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Pediatric cancer
Ganglioneuroblastoma
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Abstract MYCN amplification strongly predicts adverse outcome of neuroblastoma. However, the significance of MYCN expression in the clinical and biological behavior of neuroblastoma has been unclear. To address this question, we first examined the expression of MYCN in combination with TrkA (a favorable prognostic indicator of neuroblastoma) in 91 primary neuroblastoma by quantitative reverse transcription-PCR and investigated the relationship among patient survival, MYCN, and TrkA expressions. Three subsets of neuroblastoma were defined based on MYCN and TrkA expression. Neuroblastoma expressing the highest level of MYCN but little TrkA were MYCN-amplified cases, which had a 5-year survival of 9.3%. Interestingly, MYCN and TrkA expression showed a linear correlation (r = 0.5664, P < 0.00005) in neuroblastoma lacking MYCN amplification, and the 5-year survival of neuroblastoma patients with low MYCN and low TrkA expressions was 63.7%, whereas those with high expression of both had a 5-year survival of 88.1% (P < 0.00005). This nonlinear distribution of disease outcome relative to MYCN expression in neuroblastoma explains why MYCN expression is not predictive of neuroblastoma disease outcome by dichotomous division of the neuroblastoma cohort. However, high-level MYCN expression is associated with favorable outcome in neuroblastoma lacking MYCN amplification. Furthermore, forced expression of MYCN significantly suppresses growth of neuroblastoma cells lacking MYCN amplification by inducing apoptosis and enhancing favorable neuroblastoma gene expression. Collectively, these data suggest that high-level MYCN expression in neuroblastoma lacking MYCN amplification results in a benign phenotype. Thus, the high MYCN expression confers the opposite biological consequence in neuroblastoma, depending on whether or not MYCN is amplified. (Cancer Res 2006; 66(5): 2826-33)
N-Myc
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The prognosis of mediastinal neuroblastoma has been reported to be better than for other neuroblastomas. The reason for this is however not clear. Furthermore, a comparison between mediastinal neuroblastoma and the other neuroblastomas has been rarely reported so far. In this study, the characteristics of mediastinal neuroblastoma (84 cases) are investigated and compared with those of other neuroblastomas (440 cases). Regarding clinical factors, the age distribution and the rate of cases detected at mass screening were similar in both groups. According to Evan's staging system, the rates of early stage (I, II) were 62% in the mediastinal neuroblastoma and 38% in the other neuroblastomas (p<0.001). Regarding the biological prognostic factors, a favorable histology based on Shimada's classification was found in 100% (35/35) of the mediastinal neuroblastoma cases and in 85% (112/132) of the other neuroblastoma cases (p<0.05). With regard to N-myc amplification, all of the examined 42 cases in mediastinal neuroblastoma had a N-copy number of less than 10 copies, while 32 of the examined 263 cases (12%) in the other neuroblastomas had an amplification of N-myc of more than 10 copies (p<0.05). The 5-year survival rates were 78% in the mediastinal neuroblastoma and 59% in the other neuroblastomas, respectively. Of the cases who underwent an incomplete resection of primary tumors in localized neuroblastoma, the 5-year survival rate of the mediastinal neuroblastoma cases was significantly more favorable than that of the other neuroblastomas. The majority of mediastinal neuroblastoma cases showed an early stage and favorable prognostic factors. It is likely that the clinical and biological prognostic factors of the tumor are therefore more closely correlated with the outcome of mediastinal neuroblastoma rather than the degree of the surgical resection. Regarding the treatment for mediastinal neuroblastoma, it is most important to evaluate the biology of the tumor after surgical resection.
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1. A genomic amplification of N-myc of neuroblastoma was frequently observed in patients in the advanced stage of the disease, in those with the tumor originating from the suprarenal region, and in those with a histologically undifferentiated neuroblastoma. Thus, N-myc may be one of the most pertinent prognostic factors of neuroblastoma in patients over one year of age. 2. The neuroblastoma patient with 1-10 copies of N-myc responded to aggressive multidisciplinary therapy, even those over one year of age. 3. Rapid invasion and progression of the tumor was evident in children with more than 10 copies of N-myc. 4. N-myc amplification may correlate with immaturity of catecholamine metabolism of neuroblastoma.
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Overproduction and accumulation of amyloid-β (Aβ) have been proposed to be an initiating factor of neuron loss in Alzheimer's disease (AD). AKT is a pivotal molecule in regulating neuronal survival, however, it is still not known whether upregulation of AKT can protect the cells from the Aβ-induced apoptosis. By using cell viability assay and flow cytometry, we demonstrated in the present study that overexpression of AKT could significantly attenuate the cell apoptosis induced by Aβ1-42, whereas simultaneous inhibition of PI3 K, the immediate upstream stimulator of AKT, abolished the protective effect of AKT in HEK293 cells. Upregulation of AKT restored the Aβ-induced alterations of the mitochondria-related Bcl-2 family members (including Bcl-xL, Bcl-w, Bad, and Bax) and suppressed the activation of caspase-3 and JNK. Our data suggest that upregulation of AKT could be a promising therapeutic strategy for arresting Aβ toxicity in AD patients.
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Cancer cells differ from normal cells in both gain of functions (i.e., upregulation) and loss of functions (i.e., downregulation). While it is common to suppress gain of function for chemotherapy, it remains challenging to target downregulation in cancer cells. Here we show the combination of enzyme-instructed assembly and disassembly to target downregulation in cancer cells by designing peptidic precursors as the substrates of both carboxylesterases (CESs) and alkaline phosphatases (ALPs). The precursors turn into self-assembling molecules to form nanofibrils upon dephosphorylation by ALP, but CES-catalyzed cleavage of the ester bond on the molecules results in disassembly of the nanofibrils. The precursors selectively inhibit the cancer cells that downregulate CES (e.g., OVSAHO) but are innocuous to a hepatocyte that overexpresses CES (HepG2), while the two cell lines exhibit comparable ALP activities. This work illustrates a potential approach for the development of chemotherapy via targeting downregulation (or loss of functions) in cancer cells.
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