Abstract 2360: The role of the neurogenic transcription factor ATOH1 in small cell lung cancer

Abstract SCLC is an aggressive neuroendocrine (NE) cancer with a 7% 5-year survival rate. SCLC is treated as a clinically homogenous disease, but evidence of its intra- and inter-tumor heterogeneity is increasing. This is partly attributed to expression of neurogenic transcription factors (TFs) ASCL1 and NEUROD1, which correlate with SCLC pathogenesis and NE status, and are now included in a consensus for SCLC classification1. Our Circulating tumor cell patient Derived eXplant (CDX) models recapitulate disease heterogeneity in terms of neurogenic TF expression; furthermore, we recently identified a previously unrecognized subset within our CDX biobank expressing another neurogenic TF, ATOH12. ATOH1 function has been inferred from mouse embryonic and neonatal developmental mouse models, where Atoh1 governs the formation of cerebellar granule cells, auditory hair cells and Merkel cells. In human settings, ATOH1 reprograms pluripotent stem cells to a neuronal lineage and has context-dependent activity in cancer, being considered an oncogene in medulloblastoma and a tumor suppressor in the intestine3. I am investigating the role of ATOH1 in SCLC, to refine disease classification and explore new therapeutic approaches stratified to SCLC phenotypes. To interrogate the role of ATOH1 in SCLC, we developed an in-house antibody and established stable SCLC CDX and cell lines in which ATOH1 can be inducibly depleted in vitro and in vivo. To understand the transcriptional profile mediated by ATOH1, we performed ChIP-Seq and RNA-Seq in ATOH1-competent and depleted cells and integrated the datasets to infer ATOH1 direct transcriptional targets. In concordance with its role in development, ATOH1 direct transcriptional targets are enriched for processes regulating neurogenesis and inner ear hair cell differentiation. ATOH1 depletion in vitro in CDX17P resulted in elevated expression of Non-NE marker genes and NE to Non-NE phenotype transition, confirmed by gene set enrichment analysis, which implicated a possible role for ATOH1 in regulating neuroendocrine plasticity in SCLC. ATOH1 depletion resulted in a significant increase in apoptosis-independent cell death (p < 0.003), and whilst ATOH1 depletion did not affect cell proliferation in CDX17P, there was decreased S-phase progression in CDX30 and HCC33 cells. Depletion of ATOH1 in CDX17P In vivo did result in slower tumor growth and further studies will investigate the impact of ATOH1 on cell death, proliferation and NE to Non-NE transition in vivo. In summary, we have characterized a rare subset of SCLC expressing ATOH1 and found that ATOH1 is necessary for cell survival in vitro and ablation of ATOH1 slows tumor growth in vivo. Ongoing studies focus on investigating possible therapeutic approaches to modulate ATOH1 expression. Citation Format: Alessia Catozzi, Mitchell Revill, Jordan Roebuck, Sam Humphrey, Melanie Galvin, Fiona Blackhall, Kathryn Simpson, Alastair Kerr, Kristopher Frese, Caroline Dive. The role of the neurogenic transcription factor ATOH1 in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2360.