Longitudinal dynamics of the tumor hypoxia response: From enzyme activity to biological phenotype

Poor oxygenation (hypoxia) is a common spatially heterogeneous feature of human tumors. Biological responses to tumor hypoxia are orchestrated by the decreased activity of oxygen-dependent enzymes. The affinity of these enzymes for oxygen positions them along a continuum of oxygen sensing that defines their roles in launching reactive and adaptive cellular responses. These responses encompass regulation of all steps in the central dogma, with rapid perturbation of the metabolome and proteome followed by more persistent reprogramming of the transcriptome and epigenome. Core hypoxia response genes and pathways are commonly regulated at multiple inflection points, fine-tuning the dependencies on oxygen concentration and hypoxia duration. Ultimately, shifts in the activity of oxygen-sensing enzymes directly or indirectly endow cells with intrinsic hypoxia tolerance and drive processes that are associated with aggressive phenotypes in cancer including angiogenesis, migration, invasion, immune evasion, epithelial mesenchymal transition, and stemness.

Abstract 1431: ADO contributes to tumour initiating phenotypes

2-aminoethanethiol dioxygenase (ADO) is a thiol dioxygenase that plays a role in both metabolism and protein stability. ADO directly metabolizes cysteamine to produce hypotaurine and taurine in mammals. ADO has also been recently identified to promote oxygen dependent stability of a subset of substrates involved in the N-degron pathway in mammals (IL32, RGS4 and RGS5). The ability of ADO to target protein stability of signaling molecules suggests that it may have the potential to transduce rapid responses to hypoxia and affect tumour initiation and progression phenotypes. Here, we have successfully knocked down and knocked out ADO using two independent siRNAs and clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR-Cas9) system, respectively. We have assessed proliferation and migration through the Incucyte® ZOOM system by imaging cell confluency over time. Survival was assessed through a clonogenic assay. siRNA mediated knockdown of ADO in cervical (HeLa and SiHa), pancreatic (Panc1 and Capan2) and liver (SNU499 and Huh6) cancer cell lines drastically reduced proliferation, survival, and migration in normoxia. These results were also replicated in hypoxia (0.2% O2) across all 6 cell lines. Out of the 6 cell lines, the liver cancer cell lines were most drastically affected by the knockdown of ADO. This phenotype was replicated in the ADO KO cell lines. Taken together, these data suggest that expression of ADO may contribute to phenotypes that induce aggressive tumour phenotypes by targeting the stability of specific proteins and altering cellular metabolism in mammals.

Citation Format: Sandy Che-Eun Serena Lee, Andrea Hye An Pyo, Marianne Koritzinsky. ADO contributes to tumour initiating phenotypes [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 1431.