Abstract
The protein kinases DYRK1A and DYRK1B are pivotal regulators of cell cycle progression by promoting cell cycle exit into quiescence. DYRK1B appears to play a more important role in cancer cell quiescence than DYRK1A, as evidenced by its overexpression or copy number variations in human tumour samples. Nonetheless, the stimuli driving DYRK1B upregulation and the potential divergence in expression patterns between DYRK1A and DYRK1B remain largely elusive. In the present study, we scrutinized the regulatory pathways modulating DYRK1B expression relative to DYRK1A in PANC-1 and A549 cancer cell lines across varying conditions. Serum deprivation, pharmacological mTOR inhibition and increased cell density resulted in the differential upregulation of DYRK1B compared to DYRK1A. We then aimed to assess the role of protein kinases MST1 and MST2, which are key transmitters of cell density dependent effects. Unexpectedly, exposure to the MST1/2 inhibitor XMU-MP-1 resulted in increased DYRK1B levels in A549 cells. Further investigation into the off-target effects of XMU-MP-1 unveiled the inhibition of Aurora kinases (AURKA and AURKB) as a potential causative factor. Consistently, AURK inhibitors VX-680 (tozasertib), MLN8237 (alisertib), AZD1152-HQPA (barasertib) resulted in the upregulation of DYRK1B expression in A549 cells. In summary, our findings indicate that the expression of DYRK1A and DYRK1B is differentially regulated in cancer cells and reveal that the kinase inhibitor XMU-MP-1 increases DYRK1B expression likely through off target inhibition of Aurora kinases.