A decision-point between programmed cell death and transdifferentiation in pancreatic cancer

Transdifferentiation and changes of cellular identity are hallmarks of malignant transformation1-3. As such, the process of acinar-to-ductal metaplasia (ADM) represents a fundamental step in pancreatic ductal adenocarcinoma (PDAC) development, but regulatory pathways controlling ADM are not fully understood4,5. Here, we show that murine pancreatic acinar cells upregulate expression of CASPASE3, CASPASE8, RIPK3 and MLKL - key molecules driving both apoptosis and necroptosis6,7 - during transdifferentiation towards a duct-like phenotype. Spontaneous activation of these respective programmed cell death (PCD) pathways during KRAS-driven transdifferentiation is counterbalanced by transforming growth factor (TGF)-ß-activated kinase 1 (TAK1), a kinase transmitting inhibitory phosphorylation signals towards the apoptosis- and necroptosis activator RIPK18. Genetic deletion or pharmacological inhibition of TAK1 simultaneously triggered apoptosis and necroptosis and thereby prevented KRAS-driven ADM in vitro as well as KRAS-driven PDAC in vivo. In line, TAK1 expression is upregulated in human PDAC cells, and pharmacological inhibition of TAK1 triggered PCD in organoid and spheroid cells derived from PDAC patients. Collectively, these findings suggest that TAK1 defines a decision point between ADM and PCD in pancreas cells and represents a promising pharmacological target for the prevention and treatment of PDAC patients. Overall design: To investigate the functional effects of TAK1 inhibitor on immune cells in pancreatic tumor, we generated pancreatic tumorspheroids, treated them with TAK1 inhibitor or DMSO (vehicle CTRL) and isolated CD45+ immue cell populations by FACS sorting. We then analyzed the effect of the compound by scRNA-Seq