Lineage dependence of the neuroblastoma surfaceome defines tumor cell state-dependent and -independent immunotherapeutic targets.

Background: Neuroblastoma is a heterogeneous disease with adrenergic (ADRN)-like cells and therapy-resistant mesenchymal (MES)-like cells driven by distinct transcription factor networks. Here, we investigate the expression of immunotherapeutic targets in each neuroblastoma subtype and propose pan-neuroblastoma and cell state-specific targetable cell surface proteins.

Methods: We characterized cell lines, patient-derived xenografts, and patient samples as ADRN-dominant or MES-dominant to define subtype-specific and pan-neuroblastoma gene sets. Targets were validated with ChIP-sequencing, immunoblotting, and flow cytometry in neuroblastoma cell lines and isogenic ADRN-to-MES transition cell line models. Finally, we evaluated the activity of MES-specific agents in vivo and in vitro.

Results: Most immunotherapeutic targets being developed for neuroblastoma showed significantly higher expression in the ADRN subtype with limited expression in MES-like tumor cells. In contrast, CD276 (B7-H3) and L1CAM maintained expression across both ADRN and MES states. We identified several receptor tyrosine kinases (RTKs) enriched in MES-dominant samples and showed that AXL targeting with ADCT-601 was potently cytotoxic in MES-dominant cell lines and showed specific antitumor activity in a MES cell line-derived xenograft.

Conclusions: Immunotherapeutic strategies for neuroblastoma must address the potential of epigenetic downregulation of antigen density as a mechanism for immune evasion. We identified several RTKs as candidate MES-specific immunotherapeutic target proteins for the elimination of therapy-resistant cells. We hypothesize that the phenomena of immune escape will be less likely when targeting pan-neuroblastoma cell surface proteins such as B7-H3 and L1CAM, and/or dual targeting strategies that consider both the ADRN and MES cell states.