Investigation of melanoma cell transcriptomic states in subpopulations with high and low levels of ALDH1A3

Cancer progression and therapy resistance arise from metabolic and transcriptional adaptations, but how these are interconnected is less well understood. We propose that in melanoma, the pan-cancer stem cell marker aldehyde dehydrogenase 1A3 (ALDH1A3) couples TFAP2B-neural crest stem cell gene transcription with a distinct acetyl-histone H3 landscape via its substrate acetaldehyde. Mechanistically, nuclear acetyl-CoA synthetase 2 (ACSS2) colocalises with ALDH1A3 to bind glucose metabolic and neural crest stem cell gene loci and promote local acetyl-histone H3 modification dependent on ALDH1A3. Consistent with clinical observations that dedifferentiation into stem cell states confer poor prognosis in melanoma patients and mediate drug resistance, we found in a zebrafish melanoma model that targeting the ALDH1A3-high subpopulation with an ALDH1 suicide inhibitor delayed BRAF inhibitor drug-resistant relapse. Our work identifies ALDH1A3 as a master coordinator of acetaldehyde metabolites that directly regulates chromatin-based gene regulation, and which can be pharmacologically targeted to improve therapeutic outcomes. A375 melanoma cells with the highest and lowest ALDH activity were sorted based on Aldefluor signal and profiled for differential gene expression.