Deregulated lipid metabolism is a common feature of liver cancers needed to sustain tumor cell growth and survival. We aim at taking advantage of this vulnerability and rewiring the oncogenic metabolic hub by targeting the key metabolic player pro-protein convertase subtilisin/kexin type 9 (PCSK9). We assessed the effect of PCSK9 inhibition using the three hepatoma cell lines Huh6, Huh7 and HepG2 and validated the results using the zebrafish in vivo model. PCSK9 deficiency led to strong inhibition of cell proliferation in all cell lines. At the lipid metabolic level, PCSK9 inhibition was translated by an increase in intracellular neutral lipids, phospholipids and polyunsaturated fatty acids as well as a higher accumulation of lipid hydroperoxide. Molecular signaling analysis involved the disruption of the sequestome 1/Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (p62/Keap1/Nrf2) antioxidative axis, leading to ferroptosis, for which morphological features were confirmed by electron and confocal microscopies. The anti-tumoral effects of PCSK9 deficiency were validated using xenograft experiments in zebrafish. The inhibition of PCSK9 was effective in disrupting the oncometabolic process, inducing metabolic exhaustion and enhancing the vulnerability of cancer cells to iron-triggered lipid peroxidation. We provide strong evidence supporting the drug repositioning of anti-PCSK9 approaches to treat liver cancers.

Alterations in lipid handling are an important hallmark in cancer. Our aim here is to target key metabolic enzymes to reshape the oncogenic lipid metabolism triggering irreversible cell breakdown. We targeted the key metabolic player proprotein convertase subtilisin/kexin type 9 (PCSK9) using a pharmacological inhibitor (R-IMPP) alone or in combination with 3-hydroxy 3-methylglutaryl-Coenzyme A reductase (HMGCR) inhibitor, simvastatin. We assessed the effect of these treatments using 3 hepatoma cell lines, Huh6, Huh7 and HepG2 and a tumor xenograft in chicken choriorallantoic membrane (CAM) model. PCSK9 deficiency led to dose-dependent inhibition of cell proliferation in all cell lines and a decrease in cell migration. Co-treatment with simvastatin presented synergetic anti-proliferative effects. At the metabolic level, mitochondrial respiration assays as well as the assessment of glucose and glutamine consumption showed higher metabolic adaptability and surge in the absence of PCSK9. Enhanced lipid uptake and biogenesis led to excessive accumulation of intracellular lipid droplets as revealed by electron microscopy and metabolic tracing. Using xenograft experiments in CAM model, we further demonstrated the effect of anti-PCSK9 treatment in reducing tumor aggressiveness. Targeting PCSK9 alone or in combination with statins deserves to be considered as a new therapeutic option in liver cancer clinical applications.

Metabolic rewiring and defective immune responses are considered to be the main driving forces sustaining cell growth and oncogenesis in many cancers. The atypical enzyme, proprotein convertase subtilisin/kexin type 9 (PCSK9), is produced by the liver in large amounts and plays a major role in lipid metabolism via the control of the low density lipoprotein receptor (LDLR) and other cell surface receptors. In this context, many clinical studies have clearly demonstrated the high efficacy of PCSK9 inhibitors in treating hyperlipidemia and cardiovascular diseases. Recent data implicated PCSK9 in the degradation of major histocompatibility complex I (MHC-I) receptors and the immune system as well as in other physiological activities. This review highlights the complex crosstalk between PCSK9, lipid metabolism and immunosuppression and underlines the latest advances in understanding the involvement of this convertase in other critical functions. We present a comprehensive assessment of the different strategies targeting PCSK9 and show how these approaches could be extended to future therapeutic options to treat cancers with a main focus on the liver.

Remodelage du métabolisme lipidique en ciblant PCSK9 comme nouvelle approche thérapeutique dans les cancers du foie: La dérégulation du métabolisme énergétique, dont l'augmentation de la biosynthèse des lipides, est une caractéristique émergente de nombreux cancers, dont les cancers du foie adultes (le carcinome hépatocellulaire ou CHC) et pédiatriques (l'hépatoblastome ou HBL). Le CHC est la 3ème cause mondiale de décès par cancer. L'HBL est un cancer embryonnaire rare dont l'incidence augmente. L'analyse des données transcriptomiques disponibles montre une dérégulation de l'expression de gènes impliqués dans l'absorption et le métabolisme des lipides dans les deux cancers. Ainsi sont surexprimées PCSK9, pro-protéine convertase qui régule négativement le LDLR, et HMGCR, enzyme de la voie de synthèse de novo du cholestérol. Le rôle de PCSK9 dans le cancer du foie est peu connu. Aussi, l'objectif de mon projet est de remodeler le métabolisme des lipides autour de PCSK9 en utilisant des médicaments disponibles et surexprimer une enzyme impliquée dans la maturation de PCSK9, la méprine alpha (Mep1a) dont l’expression est augmentée dans les cancers du foie. Mes résultats montrent que le ciblage pharmacologique ou génique de PCSK9 diminue croissance et migration cellulaires et augmente la consommation d'O2. L’inhibition de l’expression génique de PCSK9 augmente les niveaux intracellulaires de certains lipides et perturbe l'axe p62/KEAP1/Nrf2 qui conduit à la ferroptose. Les effets anti-tumoraux de l’inhibition de PCSK9 ont été validés in vivo. J’ai aussi surexprimé Mep1a pour mimer le profil des tumeurs, ce qui induit une augmentation de protéines interagissant avec PCSK9 et un changement du métabolisme lipidique in vitro et in vivo. En conclusion mes résultats soulignent le rôle clé de PCSK9 dans le métabolisme lipidique et montre pour la première fois son implication dans le maintien de l'homéostasie redox cellulaire et la ferroptose. Ils ouvrent la voie au repositionnement de médicaments anti-PCSK9 pour traiter les cancers du foie avec un bénéfice thérapeutique réel.