Promyelocytic leukemia‐nuclear body formation is an early event leading to retinoic acid‐induced differentiation of neuroblastoma cells

Abstract

Neuroblastoma is one of the most common cancers in children. Neuroblastoma differentiation is linked to the presence of the promyelocytic leukemia (PML) protein. Retinoic acid, a powerful differentiation‐inducer in vitro, is a potent agent for the treatment of neuroblastoma. Using two different human neuroblastoma cell lines, SH‐SY5Y and LA‐N‐5, we show here that PML protein leads to the formation of nuclear bodies (PML‐NB) after only 1 h of retinoic acid treatment and that this formation is mediated by the extracellular signal‐regulated kinase (ERK) pathway. Inhibition of protein kinase C also leads to formation of PML‐NB via the ERK pathway. Both sumoylation and phosphorylation of PML in an ERK‐dependent pathway are also required for formation of PML‐NB. Finally, we show that PML‐NB formation in neuroblastoma cells is associated with neurite outgrowth. These results support the proposal that the formation of PML‐NB is correlated with the differentiation of neuroblastoma cells.

NF1 Is a Tumor Suppressor in Neuroblastoma that Determines Retinoic Acid Response and Disease Outcome

“…Other studies have also suggested a role for MAPK signaling in regulation of responses to RA in different cellular systems (Antonyak et al, 2003; Bruck et al, 2009; Delaune et al, 2008; Gianni et al, 2006; Kosa et al, 1995; Quinlan et al, 2008; Verheijen et al, 1999). These data indicate that the effects of MAPK signaling on RA responses can be heterogeneous.…”

Characterization of Nuclear Localization and SUMOylation of the ATBF1 Transcription Factor in Epithelial Cells

“…In addition, PML NBs themselves are also regulated by SUMOylation at two levels. Firstly, PML is directly SUMOylated at multiple lysine residues, and SUMOylation is essential for the formation of PML NBs [34], [44], [45]. Secondly, PML also has a SUMO binding motif that is independent of its SUMOylation sites but is also necessary for PML NB formation [35].…”

Interplay Between Protein Kinase C Isoforms Alpha and Epsilon, Neurofibromin, and the Ras/MAPK Pathway in Neuroblastoma Differentiation

“…Furthermore, in www.intechopen.com SH-SY5Y and LA-N-5 cells, ERK mediates an early (within 1h) RA-induced formation of promyelocytic leukemia nuclear bodies, an event associated with NB differentiation (Delaune et al, 2008). Apparently, ERK activity may impinge differentially on early and late gene regulation and inhibitor studies have not always addressed these issues with sufficient detail (Miloso et al, 2004;Lee & Kim, 2004;Delaune et al, 2008;Holzel et al, 2010). In addition, evidence from the various differentiation protocols and agents suggests that the transcription programs for neuritic outgrowth or expression of neuron-specific genes may be independently regulated in NB cells.…”

“…Stable overexpression of RKIP (Raf kinase inhibitor protein), a scaffold protein crucial for Raf and ERK pathway activation, accelerated the rate of neuritic outgrowth and increased the expression of neuronal markers in response to RA in SH-SY5Y cells, all concurrent with sustained ERK activation (Hellmann et al, 2010). Furthermore, in www.intechopen.com SH-SY5Y and LA-N-5 cells, ERK mediates an early (within 1h) RA-induced formation of promyelocytic leukemia nuclear bodies, an event associated with NB differentiation (Delaune et al, 2008). Apparently, ERK activity may impinge differentially on early and late gene regulation and inhibitor studies have not always addressed these issues with sufficient detail (Miloso et al, 2004;Lee & Kim, 2004;Delaune et al, 2008;Holzel et al, 2010).…”

“…A large body of evidence suggests a positive role of Ras, Raf, and prolonged ERK activation in neuronal differentiation in PC12 cells and several other cellular models (see section 2.1.2), but the situation is certainly more complicated when RA-induced NB differentiation is concerned. ERK is invariably activated by RA in the short- (Delaune et al, 2008) or longterm (Lee & Kim, 2004;Miloso et al, 2004), yet inhibition of the ERK activating kinase MEK by U0126 or PD98059 has yielded contradictory results on whether RA-induced ERK activation is necessary for neuritic outgrowth in SH-SY5Y and SK-N-BE(2)C cells (Miloso et al, 2004;Lee & Kim, 2004). Stable overexpression of RKIP (Raf kinase inhibitor protein), a scaffold protein crucial for Raf and ERK pathway activation, accelerated the rate of neuritic outgrowth and increased the expression of neuronal markers in response to RA in SH-SY5Y cells, all concurrent with sustained ERK activation (Hellmann et al, 2010).…”