Abstract 3106: Targeting vitamin D signalling in metastatic neuroblastoma

Background: Neuroblastoma (NB) is the most common extra-cranial solid tumor and the most frequent cause of cancer-related deaths in children. More than half of patients with NB have metastases and their survival is <50%, and only 5% after relapse. Currently, there are no therapies that specifically target metastatic NB and there is a lack of NB models that recapitulate the sites and burden of metastases observed in patients.Methods: To study metastatic NB, we have developed a mouse model using in vivo selection of SKNAS cells that metastasize following intra-cardiac injection. We isolated subpopulations from bone and brain with enhanced metastatic properties and compared their gene expression profiles to those of the parental SKNAS cells. Using Connectivity Map (CMap) analyses, we identified drugs that were predicted to change the gene expression in the metastatic subpopulations to a profile that is similar to that of parental cell lines.Results: Calcipotriol, a synthetic analogue of vitamin D, was identified from the CMap analysis to be a potentially selective agent for metastatic NB cell lines. In comparison to the parental cells, treatment of the metastatic subpopulations with calcipotriol resulted in reduced proliferation. Furthermore, calcipotriol sensitivity was reduced in metastatic cells with a knockout of vitamin D receptor (VDR) suggesting its effect is on-target. In contrast to the parental cells, following calcipotriol treatment metastatic subpopulations did not exhibit an increase in protein levels of CYP24A1, the enzyme that metabolizes vitamin D, suggesting a potential mechanism for the differential sensitivity of parental and metastatic cells. Calcipotriol treatment also reduced levels of hippo pathway effectors, YAP and TAZ, which we previously reported to play a role in mediating the metastatic phenotype of the isolated subpopulations. Additionally, metastatic cells that were pre-treated with calcipotriol showed reduced migration in a transwell assay whereas the migration potential of parental cells was not affected. Furthermore, RASSF2, an upstream regulator of the hippo pathway, was identified to be upregulated in a VDR-dependent manner after calcipotriol treatment in the metastatic subpopulations indicating a possible mechanistic link for the effects of calcipotriol on the hippo pathway in these metastatic cells.Conclusions: Calcipotriol was identified to be more effective against metastatic NB subpopulations in vitro and this may be in part due to defects in CYP24A1 induction in these metastatic cells. Our data also suggests a novel link between VDR, the hippo pathway and metastasis in NB. Further experiments are required to determine the role of VDR, mechanism of action of calcipotriol in selectively inhibiting growth of metastatic NB cells.Citation Format: Yagnesh Ladumor, Bo Kyung Alex Seong, Robin Hallett, Teresa Adderley, Yingying Wang, Lynn Kee, David Kaplan, Meredith Irwin. Targeting vitamin D signalling in metastatic neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3106.