No abstract

The recently discovered MCPIP1 (monocyte chemoattractant protein-induced protein 1), a multidomain protein encoded by the MCPIP1 (ZC3H12A) gene, has been described as a new differentiation factor, a ribonuclease, and a deubiquitination-supporting factor. However, its role in cancer is poorly recognized. Our recent analysis of microarrays data showed a lack of expression of the MCPIP1 transcript in primary neuroblastoma, the most common extracranial solid tumor in children. Additionally, enforced expression of the MCPIP1 gene in BE(2)-C cells caused a significant decrease in neuroblastoma proliferation and viability. Aim of the present study was to further investigate the role of MCPIP1 in neuroblastoma, using expression DNA microarrays and microRNA microarrays. Transient transfections of BE(2)-C cells were used for overexpression of either wild type of MCPIP1 (MCPIP1-wt) or its RN-ase defective mutant (MCPIP1-ΔPIN). We have analyzed changes of transcriptome and next, we have used qRT-PCR to verify mRNA levels of selected genes responding to MCPIP1 overexpression. Additionally, protein levels were determined for some of the selected genes. The choline transporter, CTL1, encoded by the SLC44A1 gene, was significantly repressed at the specific mRNA and protein levels and most importantly this translated into a decreased choline transport in MCPIP1-overexpressing cells. Then, we have found microRNA-3613-3p as the mostly altered in the pools of cells overexpressing the wild type MCPIP1. Next, we analyzed the predicted targets of the miR-3613-3p and validated them using qRT-PCR and western blot. These results indicate that the expression of miR-3613-3p might be regulated by MCPIP1 by cleavage of its precursor form.

The main physiological function of MCPIP1 (regnase-1) is negative regulation of inflammation. Moreover, roles of regnase-1 in apoptosis and differentiation have also been described, but its involvement in cancer is yet to be fully recognized. Earlier, we showed a lack of expression of MCPIP1 in both primary tumors and several neuroblastoma cell lines. Additionally, we reported that levels of MCPIP1 and the key neuroblastoma oncoprotein-MYCN were inversely correlated in BE(2)-C clones overexpressing the MCPIP1 gene. Here, we show that exogenous expression of the MCPIP1 protein decreases MYCN mRNA and protein levels without changing the MYCN mRNA half-life. Furthermore, it was shown that MCPIP1-wt exogenous expression affects levels and phosphorylation of MYCN partners such as Aurora A (Thr288), CDC2 (Tyr15 and Thr161), GSK3β (Ser9), and key cellular components of Akt/mTOR signaling, which regulate MYCN stability and activation. In accordance with the obtained results, we found increased phosphorylation of MYCN protein at Thr58 that causes destabilization of the oncoprotein. Moreover, it is shown that exogenous expression of MCPIP1 does not cause apoptosis. Our data extend knowledge on roles of MCPIP1 in our model and link the protein to regulation of expression and stability of MYCN through decrease of signaling via Akt/mTOR pathway. J. Cell. Biochem. 118: 1741-1755, 2017. © 2016 Wiley Periodicals, Inc.

The importance of monocyte chemotactic protein-1-induced protein 1 (MCPIP1) in the negative regulation of inflammatory reactions has already been extensively studied. However, its role in cancer is not yet established. We studied MCPIP1 gene expression in primary human neuroblastomas and several neuroblastoma cell lines. Our results showed a lack of MCPIP1 expression in primary neuroblastoma tumors. Moreover, it was found that the low expression of the protein measured in human neuroblastoma cell lines might be important for neuroblastoma survival, since enforced MCPIP1 gene expression in human neuroblastoma BE(2)-C cells caused a significant decrease in neuroblastoma cell viability and proliferation.

Abstract. Mechanisms leading to inhibitory effects of an anti-GD2 ganglioside (GD2) 14G2a mouse monoclonal antibody (mAb) and PI3K/Akt/mTOR pathway inhibitors on human neuroblastoma cell survival were studied in vitro. We have recently shown on IMR-32, CHP-134, and LA-N-1 neuroblastoma cells that targeting GD2 with the mAb decreases cell viability of the cell lines. In this study we used cytotoxicity assays, proteomic arrays and immunoblotting to evaluate the response of the three cell lines to the anti-GD2 14G2a mAb and specific PI3K/Akt/mTOR pathway inhibitors. We show here that the mAb modulates intracellular signal transduction through changes in several kinases and their substrates phosphorylation. More detailed analysis of the PI3K/Akt/ mTOR pathway showed significant decrease in activity of Akt, mTOR, p70 S6 and 4E-BP1 proteins and transient increase in PTEN (a suppressor of the pathway), leading to inhibition of the signaling network responsible for stimulation of translation and proliferation. Additionally, combining the GD2-specific 14G2a mAb with an Akt inhibitor (perifosine), dual mTOR/PI3K inhibitors (BEZ-235 and SAR245409), and a pan-PI3K inhibitor (LY294002) was shown to enhance cytotoxic effects against IMR-32, CHP-134 and LA-N-1 cells. Our study extends knowledge on mechanisms of action of the 14G2a mAb on the neuroblastoma cells. Also, it stresses the need for further delineation of molecular signal orchestration aimed at more reasonable selection of drugs to target key cellular pathways in quest for better cure for neuroblastoma patients.

Monocyte chemoattractant protein-1-induced protein 1 (MCPIP1) has a multidomain structure, which assures its pleiotropic activity. The physiological functions of this protein include repression of inflammatory processes and the prevention of immune disorders. The influence of MCPIP1 on the cell cycle of cancer cells has not been sufficiently elucidated. A previous study by our group reported that overexpression of MCPIP1 affects the cell viability, inhibits the activation of the phosphoinositide-3 kinase/mammalian target of rapamycin signalling pathway, and reduces the stability of the MYCN oncogene in neuroblastoma (NB) cells.Furthermore, a decrease in expression and phosphorylation levels of cyclindependent kinase (CDK) 1, which has a key role in the M phase of the cell cycle, was observed. On the basis of these previous results, the purpose of our present study was to elucidate the influence of MCPIP1 on the cell cycle of NB cells. It was confirmed that ectopic overexpression of MCPIP1 in two human NB cell lines, KELLY and BE (2)-C, inhibited cell proliferation. Furthermore, flow cytometric analyses and imaging of the cell cycle with a fluorescence ubiquitination cell-cycle indicator test, demonstrated that overexpression of MCPIP1 causes an accumulation of NB cells in the G1 phase of the cell cycle, while the possibility of an increase in G0 phase due to induction of quiescence or senescence was excluded. Additional assessment of the molecular machinery responsible for the transition between the cell-cycle phases confirmed that MCPIP1 overexpression reduced the expression of cyclins A2, B1, D1, D3, E1, and E2 and decreased the phosphorylation of CDK2 and CDK4, as well as retinoblastoma protein. In conclusion, the present results indicated a relevant impact of overexpression of MCPIP1 on the cell cycle, namely a block of the G1/S cell-cycle checkpoint, resulting in arrest of NB cells in the G1 phase. K E Y W O R D S cell cycle, G1/S cell-cycle arrest, MCPIP1, neuroblastoma

Abstract.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. IntroductionPHLDA1 was identified as a gene involved in Fas (CD95) expression and apoptosis induced after an anti-TCR antibody binding to mouse T cell hybridoma cells (1). In humans the gene is located on the long arm of the chromosome 12 [12q15 (2)] and encodes a 401 amino acid (aa) protein (45 kDa) named pleckstrin-homology-like domain family A, member 1 (PHLDA1, synonyms include: DT1P1B11, PHRIP, 'prolinehistidine rich protein', TDAG51, based on www.genecards. org).Several research groups have aimed to characterize involvement of PHLDA1 in biology of cancer cells, including its function in apoptosis. Thus, Neef et al measured levels of mRNA of PHLDA1 in three sets of cell lines, derived from paired samples of primary and metastatic melanoma tumors, and reported that PHLDA1 was downregulated in the latter. PHLDA1 was detected by the authors in benign melanocytic nevi, and its level was shown to decrease with progression of malignant melanomas. Also, constitutive expression of the PHLDA1 protein in a melanoma cell line Mel Rif has led to cell growth reduction along with an increase in basal apoptosis and sensitivity to doxorubicin and camptothecin (3). In 2006, Hayashida et al showed that PHLDA1 is a heat shock inducible gene regulated by HSF1 and when overexpressed in HeLa cells has pro-apoptotic functions (4). In yet another report, Nagai et al have reported that downregulation of PHLDA1 is a strong predictor of ...

Sulforaphane (SFN) is an isothiocyanate present in cruciferous vegetables, which has been shown to exert an anti-cancer effect when tested in vitro and in vivo. The anti-cancer effects of SFN encompass induction of cytoprotective autophagy; therefore, the present study aimed to determine whether the chemopreventive activity of SFN may be potentiated by inhibition of autophagy. The present study provided detailed insight into the susceptibility of human neuroblastoma cells to treatment with synthetic SFN, in combination with an inhibitor of autophagy, 3-methyladenine (3-MA). The present study confirmed the suppression of the viability of the human neuroblastoma cell line BE(2)-C by SFN and reported the inhibition of DNA synthesis, as determined by a decrease in tritiated thymidine incorporation. Furthermore, the results verified the effectiveness of SFN in inducing apoptosis in the BE(2)-C cell line as demonstrated by caspase activation, increased protein expression levels of B-cell lymphoma 2-associated X protein and loss of mitochondrial membrane potential. Combined treatment of the cells with SFN with 3-MA proved to be effective in decreasing cell viability, through a mechanism that may proceed via the early induction of autophagy by SFN, followed by induction of apoptosis, as well as inhibition of autophagy by 3-MA.