Netrin-1 acts as a survival factor for aggressive neuroblastoma

Abstract

Neuroblastoma (NB), the most frequent solid tumor of early childhood, is diagnosed as a disseminated disease in >60% of cases, and several lines of evidence support the resistance to apoptosis as a prerequisite for NB progression. We show that autocrine production of netrin-1, a multifunctional laminin-related molecule, conveys a selective advantage in tumor growth and dissemination in aggressive NB, as it blocks the proapoptotic activity of the UNC5H netrin-1 dependence receptors. We show that such netrin-1 up-regulation is a potential marker for poor prognosis in stage 4S and, more generally, in NB stage 4 diagnosed infants. Moreover, we propose that interference with the netrin-1 autocrine loop in malignant neuroblasts could represent an alternative therapeutic strategy, as disruption of this loop triggers in vitro NB cell death and inhibits NB metastasis in avian and mouse models.

Kremen1 and Dickkopf1 control cell survival in a Wnt-independent manner

“…New perspectives are currently arising, consisting in characterizing tumors that express both a dependence receptor and its ligand and trying to interfere with production of the latter. [38][39][40][41] We provide strong evidences supporting an evolutionary acquisition of dependence behavior for Krm1, which might be one of the mechanisms by which placental mammals tackled the necessity to develop protective strategies against cancers. We further suggest that in humans, Krm1 apoptotic behavior can be regulated by alternative splicing.…”

Netrin-1 up-regulation in inflammatory bowel diseases is required for colorectal cancer progression

“…either a gain of netrin-1 or a loss of netrin-1 receptors (16,17), in AOM/DSS-associated tumors, the analysis of the netrin-1 receptors expression by Q-RT-PCR shows that UNC5H1, UNC5H2, UNC5H3, UNC5H4, or DCC were not downregulated-that is, while UNC5H1 and UNC5H2 level was not significantly changed, UNC5H3, UNC5H4, and DCC were actually up-regulated- (Fig. S1).…”

Anchoring of Protein Kinase A by ERM (Ezrin-Radixin-Moesin) Proteins Is Required for Proper Netrin Signaling through DCC (Deleted in Colorectal Cancer)

“…It should be noted here that UNC5H is expressed in IMR-32 cells (Ref. 62 and data not shown), the cells used in the current study to show that uncoupling PKA from ERM proteins and DCC switches netrin tropism from attraction to repulsion. Although recently solved crystal structures of netrin-receptor complexes (70,71) provide intriguing possibilities, the exact molecular mechanism through which this dramatic switch in cellular response takes place and the manner in which PKA and ERM proteins might contribute to the switch remains unclear.…”

“…IMR-32 human neuroblastoma cells were used for subsequent experiments for the following reasons: they express all of the proteins of interest (Fig. 4C), they have been used previously to great effect for analyses of DCC function (40,62), they can be differentiated easily and form axonal processes with well formed growth cones (63)(64)(65), and finally, they allow ERM-silencing and rescue experiments to be performed with unaltered murine homologs, which are naturally resistant to commercially available human-specific RNAi reagents. Transfection of IMR-32 cells with shRNA plasmids targeting individual ERM proteins confirmed the specificity and efficacy of the reagents; for each plasmid, there was at least a 75% knockdown in the expression of the target ERM protein with no significant effect on the other two (Fig.…”