Bongers, A. | Search bioRxiv

bioRxiv2024

The polyamine transporter ATP13A3 mediates DFMO-induced polyamine uptake in neuroblastoma

High-risk neuroblastomas, often associated with MYCN oncogene amplification, are addicted to polyamines, small polycations vital for cellular functioning. We have shown that neuroblastoma cells increase polyamine uptake when exposed to the polyamine biosynthesis inhibitor DFMO, currently in clinical trial, and that this mechanism limits the efficacy of the drug. While this finding resulted in the clinical development of polyamine transport inhibitors including AMXT 1501, presently under clinical investigation in combination with DFMO, the mechanisms and transporters involved in DFMO-induced polyamine uptake are unknown. Knockdown of ATP13A3, a member of the P5B-ATPase family, limited basal and DFMO-induced polyamine uptake, attenuated MYCN-amplified and non-MYCN-amplified neuroblastoma cell growth and potentiated the inhibitory effects of DFMO. Overexpression of ATP13A3 in neuroblastoma cells increased polyamine uptake, which was inhibited by AMXT 1501, highlighting ATP13A3 as a key target of the drug. The association between high ATP13A3 expression and poorer survival in neuroblastoma further supports a role of this transporter in neuroblastoma progression. Thus, this study identified ATP13A3 as a critical regulator of basal and DFMO-induced polyamine uptake and a novel therapeutic target for neuroblastoma. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/581161v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@11bef78org.highwire.dtl.DTLVardef@106c250org.highwire.dtl.DTLVardef@bf39b1org.highwire.dtl.DTLVardef@64d05f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

Myeloperoxidase activity predicts atherosclerotic plaque disruption and atherothrombosis

BackgroundUnstable atherosclerotic plaque is characterized by increased myeloperoxidase (MPO) activity. As unstable plaque is vulnerable to disruption and ensuing thrombosis, we examined whether plaque MPO activity predicts atherothrombosis in a pre-clinical model and correlates with ruptured human atheroma. MethodsTo assess if plaque MPO activity predicts atherothrombosis, rabbits were subjected to aortic endothelial denudation, cholesterol feeding, in vivo magnetic resonance imaging (MRI) of MPO activity using MPO-Gd (gadolinium), followed by pharmacological triggering of atherothrombosis, histology, and MPO activity determined by liquid chromatography tandem mass spectrometry (LC-MSMS) by quantifying the MPO-specific product of hydroethidine, 2-chloroethidium. To correlate plaque MPO activity to ruptured human atheroma, ex vivo determination of MPO activity by MPO-Gd retention in carotid endarterectomy (CEA) specimens was correlated with in vivo MRI plaque phenotyping in patients, histology, and MPO activity determined by LC-MSMS. ResultsIn rabbits, pre-trigger in vivo MPO activity, validated by LC-MSMS and histology, was higher in thrombosis-prone than thrombosis-resistant plaques and lesion-free segments (R1 relaxation rate = 2.2 {+/-} 0.4 versus 1.6 {+/-} 0.2 and 1.5 {+/-} 0.2 s-1, respectively, p<0.0001), and it predicted atherothrombosis. In CEA specimens, MPO-Gd retention was greater in histologic and MRI-graded American Heart Association (AHA) type VI than types III, IV and V plaques ({Delta}R1 relaxation rate from baseline = 48 {+/-} 6 versus 16 {+/-} 7, 17 {+/-} 8 and 23 {+/-} 8%, respectively, p<0.0001). This association was confirmed by comparing AHA grade to MPO activity determined by LC-MSMS (277 {+/-} 338 versus 7 {+/-} 6, 11 {+/-} 12 and 42 {+/-} 39 pmol 2-chloroethidium/mg protein for type VI versus type III-V plaques, respectively, p=0.0008). ConclusionsMPO activity is elevated in thrombosis-prone rabbit and ruptured human atheroma. Non-invasive molecular imaging of MPO activity predicts atherothrombosis, highlighting the potential of arterial MPO activity to detect vulnerable, destabilized atherosclerosis.

biochemistry↗