Abstract A08: Divergent tumor cell states in neuroblastoma possess distinct immunogenic phenotypes

Active immunotherapy approaches for neuroblastoma (NB), a pediatric cancer of the sympathetic nervous system, has met with limited success. Especially challenging is the genetic heterogeneity of NB which makes it difficult to identify factors that consistently indicate the likelihood of an effective immune response and thereby select patients who are most likely to benefit from immunotherapy. Hence, we undertook an unbiased analysis of gene expression signatures from >500 well-annotated primary NBs representing diverse clinical and genetic subtypes to identify of predictors of immune response. Using clustering analysis of bulk transcriptomic signatures from these tumors, we identified a subset of NBs that was notable for the high expression of genes associated with anti-tumor immune response. These “immunogenic” tumors showed a predominance of gene expression signatures derived from malignant cells with primitive neural crest-like or mesenchymal properties, one of the two cell states that shape intratumoral heterogeneity in NB. In contrast, tumors that expressed committed, adrenergic neuron-like signatures were less immunogenic. Single-cell (sc) RNA-seq and immunohistochemistry analysis further confirmed that NBs comprise both adrenergic and mesenchymal tumor cells, and that the presence of mesenchymal cells positively associated with immune cell infiltration into the TME. scRNA-seq also revealed that mesenchymal NB cells were enriched for inflammatory gene signature. Gene expression analysis of isogenic pairs of adrenergic and mesenchymal cells showed that mesenchymal NBs differentially upregulate genes involved in regulating antigen processing and presentation, MHC class I expression, type-I interferon and TLR3 signaling, and NK cell activation. This is achieved through a permissive chromatin landscape at the promoters of these immune regulatory genes that support their high expression in mesenchymal cells. By contrast, in adrenergic cells, tumor-intrinsic immune genes are epigenetically silenced by the PRC2 complex and PRC2 inhibition leads to increased immune cell activation. Remarkably, induction of the mesenchymal state in adrenergic cells through transcriptional reprogramming by PRRX1 or therapy resistance is accompanied by the epigenetic activation of innate and adaptive immune response genes. Functionally, the inherent immunogenicity of mesenchymal cells promotes T cell infiltration by secreting inflammatory cytokines, enables efficient targeting by antigen-specific cytotoxic T and NK cells, and imparts responsiveness to immune checkpoint blockade in a syngeneic NB model. In conclusion, our study uncovers an unappreciated link between immunogenicity and tumor lineage state in NB, and rationalizes future interrogations into (i) avenues through which the vulnerability of mesenchymal cells to immune-mediated targeting could be harnessed clinically and (ii) how perturbation of epigenetically-regulated cell states could be harnessed to promote anti-tumor immune response. Citation Format: Satyaki Sengupta, Sanjukta Das, Angela C. Crespo, Annelisa M. Cornel, Anand G. Patel, Navin R. Mahadevan, Marco Campisi, Alaa K. Ali, Bandana Sharma, Jared H. Rowe, Rogier Versteeg, Rudolf Jaenisch, Stefani Spranger, Rizwan Romee, Brian C. Miller, David A. Barbie, Stefan Nierkens, Michael A. Dyer, Judy Lieberman, Rani E. George. Divergent tumor cell states in neuroblastoma possess distinct immunogenic phenotypes [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A08.