Olfactory neuroblastoma mimics molecular subtypes and lineage trajectories of small cell lung cancer [Single cell RNA seq on RPM-GFP and RPMA ONB tumors]
The olfactory epithelium relies on active neuron regeneration from basal stem cells and is susceptible to olfactory neuroblastoma (ONB), a rare, aggressive tumor of unclear origins. Here, we establish a new, highly-penetrant, genetically-engineered mouse model of ONB with alterations in Rb1/Trp53/Myc that exhibit a NEUROD1+ immature neuronal state. ASCL1 loss leads to emergence of non-neuronal histopathologies, including a POU2F3+ microvillar-like state. We find ONB tumor heterogeneity to recapitulate developmental states of multipotent globose basal cells (GBCs), which our data demonstrate is a cell of origin for ONB. Similar to small cell lung cancer (SCLC), mouse and human ONB exhibit: mutually exclusive ASCL1, NEUROD1, and POU2F3- like states, an immune-cold tumor microenvironment, intratumoral subtype heterogeneity comprising neuronal and non-neuronal lineages, and subtype plasticity—as evidenced by barcode-based lineage tracing and single-cell transcriptomics. Collectively, our findings highlight conserved developmental trajectories between ONB and SCLC subtypes with significant implications for ONB classification and treatment. Overall design: We harvested olfactory neuroblastoma tumor cells from n=1 homozygous Rb1 fl/fl; Trp53 fl/fl; H11b-LSL-MycT58A-Ires-Luc (RPM)-Rosa26-LSL-Cas9-Ires-Gfp  (RPM-GFP) mouse in which tumor cells are GFP+, and n=3  homozygous Rb1 fl/fl; Trp53 fl/fl; H11b-LSL-MycT58A-Ires-Luc; Ascl1 fl/fl (RPMA) to perform single cell RNA-sequencing (scRNA-seq). Tumors were micro-dissected from the olfactory cavity of each mouse, processed into single cell suspensions, and subject to  10X Genomics single-cell gene expression library construction (Dual-Index 3' GEX) and downstream Illumina-based sequencing.