Abstract SY24-02: Neuroblastoma: A developmental twist
Authors: Versteeg Rogier , Valentijn Linda , Koster Jan , Groningen Tim van , Hamdi Mohamed , Westerhout Ellen , Nes Johan van 
Published: August 2019

Abstract
Intra-tumor heterogeneity is considered as a source of drug-resistant cells that can escape therapy and form relapses. Several tumor types display a structured intra-tumor heterogeneity, consisting of immature tumor cells and lineage-committed tumor cells. The immature populations of some tumor types have been implicated in drug resistance. The pediatric tumor neuroblastoma includes besides lineage committed adrenergic (ADRN) cells a minority of undifferentiated mesenchymal (MES) tumor cells which diverge in gene expression and epigenetic modifications (van Groningen et al., Nature Genetics 2017). MES cells are relatively resistant to chemotherapy and are enriched in post-treatment samples, suggesting selection and a role in relapse development. However, the co-existence of two tumor cell populations, their differential drug sensitivity and their relation to normal development remain enigmatic. Here we show how MES-type neuroblastoma cells fundamentally differ from ADRN-type cells and resemble normal precursor cells of the adrenergic lineage, including expression of metabolic routes providing resistance to therapy. MES cells and ADRN cells share the same genetic defects, but strongly differ in super enhancers. Each cell type is marked by about 200 specific super enhancers that are absent in the other cell type. Analysis of the genes under their control identified about 20 MES-specific transcription factors and 20 ADRN-specific transcription factors. Chip-seq analysis showed that they conform to a model of MES-specific or ADRN-specific core regulatory circuitries (CRC). Such circuitries were proposed to form a feed-forward system that imposes lineage specification (Hnisz et al., Cell 2012). In agreement with a cell-type specifying role for the CRC, we found that induced expression of MES-specific CRC transcription factors could reprogram ADRN-type cells into MES-type cells. This included a shift towards MES-type super enhancers and expression of associated MES-type genes. Neuroblastoma are tumors of the peripheral adrenergic lineage, which is neural crest derived. MES-type cells lack expression of typical differentiation markers of this lineage, like enzymes for the adrenalin synthesis route TH and DBH. We therefore analyzed whether MES cells resemble precursor cell types of this lineage. Schwann Cell Precursors (SCP) were recently implicated as migratory precursor cells of the adrenergic lineage (Furlan et al., Science 2017). We found that MES cells are highly similar to SCP cells. We therefore analyzed whether the drug resistance of MES cells relate to their normal developmental counterparts. Indeed we observed that the similarity of SCP and MES cells extends to metabolic routes that affect resistance to drugs used in neuroblastoma therapy. Our analyses show that heterogeneity in neuroblastoma is structured and resembles cell types of the normal differentiation program of the adrenergic lineage. MES and ADRN cell types have conserved gene expression programs that determine their response to therapy. MES cells are thereby unresponsive to clinically used therapeutic drugs and may survive therapy. Targeting of lineage-differentiated as well as immature tumor cell types may therefore be a promising strategy to attenuate development of therapy-resistant tumor relapses.
Citation Format: Rogier Versteeg, Linda Valentijn, Jan Koster, Tim van Groningen, Mohamed Hamdi, Ellen Westerhout, Johan van Nes. Neuroblastoma: A developmental twist [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 SY24-02.