Mitochondrial signatures shape phenotype switching and apoptosis in response to PLK1 and RSK inhibitiors in melanoma

PLK1 inhibitors are emerging anti-cancer agents being tested in monotherapy and combination therapies for various cancers. Although PLK1 inhibition in experimental models shows potent antitumor effects, translation to the clinic has been hampered by low antitumor activity and tumor relapse. Here, we report the identification of mitochondrial protein signatures that determine sensitivity to approaches targeting PLK1 in human melanoma cell lines. In response to PLK1 inhibition or gene silencing, resistant cells adopt a pro-inflammatory and dedifferentiated phenotype, while sensitive cells engage apoptosis. Mitochondrial DNA depletion and silencing of the ABCD1 transporter sensitize cells to PLK1 inhibition and attenuate the associated pro-inflammatory response. We also found that non-selective inhibitors of the p90 ribosomal S6 kinase (RSK) exert their anti-proliferative and pro-inflammatory effects via PLK1 inhibition. This work reveals overlooked impacts of PLK1 on phenotype switching and suggests that mitochondrial precision medicine can help improve response to targeted therapies. Human melanoma cell lines were treated with p90 ribosomal S6 kinase (RSK) inhibitors for 72 h. The MeWo cell line was treated with DMSO 0.1% or the RSK inhibitor BI-D1870 3 µM. The A-375 cell line was treated with DMSO 0.1% or the RSK inhibitor LJH685 at 3 µM. The 3 samples per condition are from 3 independent experiments in which a pair of plates is treated with DMSO or a RSK inhibitor. A-375 and MeWo samples cannot be compared as they were analysed by RNA-seq separately.