Harmine suppresses pancreatic cancer through DYRK1A-mediated hyper-activated RAS/MAPK inhibition.

KRAS G12D is the most frequent RAS mutation in pancreatic cancer (PC). Recently, small molecule inhibitors like MRTX1133, which target KRAS G12D, have shown efficacy in inhibiting PC growth. However, the development of intrinsic and acquired resistance to these inhibitors has been observed, necessitating the identification of novel therapeutic targets. In this study, we first reported that dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) could modulate the level of KRAS G12D-GTP depending on its phosphatase activity, and its knockdown could inhibit the hyperactivation of KRAS G12D. It was found that DYRK1A could be the target of harmine (HM) to regulate the activity of KRAS G12D/MAPK, resulting in HM inhibiting the malignant phenotypes of PC cells. To elucidate the underlying mechanism, we confirmed the interaction between DYRK1A and KRAS G12D using fluorescence colocalization, bimolecular fluorescence complementation (Bi-FC), and co-immunoprecipitation (Co-IP). We further established that the kinase activity was essential for DYRK1A to activate KRAS G12D. In addition, RNA sequencing revealed that HM induced downregulation of RAS-related pathway gene expression in PC. It was also found that HM may demonstrate anti-PC effect by inhibiting autophagy. In spite of the mechanism, we further validated the potential of DYRK1A as a therapeutic target for KRAS G12D-induced cancer based on Caenorhabditis elegans model. The loss-of-function mutation in mbk-1 (DYRK1A homologous gene) could inhibit the multivulva (Muv) phenotype in nematodes with KRAS G12D. Collectively, our findings indicate that HM could suppress the RAS/MAPK pathway by inhibiting DYRK1A kinase activity, suggesting that DYRK1A could serve as a therapeutic target for PC treatment.