Restoration of the molecular clock is tumor suppressive in neuroblastoma

Abstract

MYCN activation is a hallmark of advanced neuroblastoma (NB) and a known master regulator of metabolic reprogramming, favoring NB adaptation to its microenvironment. We found that the expression of the main regulators of the molecular clock loops is profoundly disrupted in MYCN-amplified NB patients, and this disruption independently predicts poor clinical outcome. MYCN induces the expression of clock repressors and downregulates the one of clock activators by directly binding to their promoters. Ultimately, MYCN attenuates the molecular clock by suppressing BMAL1 expression and oscillation, thereby promoting cell survival. Reestablishment of the activity of the clock activator RORα via its genetic overexpression and its stimulation through the agonist SR1078, restores BMAL1 expression and oscillation, effectively blocks MYCN-mediated tumor growth and de novo lipogenesis, and sensitizes NB tumors to conventional chemotherapy. In conclusion, reactivation of RORα could serve as a therapeutic strategy for MYCN-amplified NBs by blocking the dysregulation of molecular clock and cell metabolism mediated by MYCN.

MYCN-driven fatty acid uptake is a metabolic vulnerability in neuroblastoma

“…To specifically evaluate the lipid metabolic changes induced by MYCN, we performed targeted lipidomics in LAN5 shMYCN, MYCN3 Tet-On cells, and SK-N-AS MYCN-ER ™ cells, in which MYCN-mediated transcription is conditionally activated by 4-hydroxytamoxifen (4-OHT) 23 . Significantly altered lipids are represented in the heatmap (FDR < 0.25, Fig.…”

“…MRI images were analyzed and processed in Osirix (5.8.5, Pixmeo, Bernex, Switzerland), and data are expressed as tumor volume in cm 3 . Power Analysis : based on our previous studies 23 , at least six mice per group are required to reach 80% statistical power at p < 0.05 ( https://www.stat.ubc.ca/~rollin/stats/ssize/n2 ). Mice were randomized and evenly allocated into treatment groups.…”

“…Synergy heatmaps were prepared in GraphPad Prism (7.01). Caspase 3/7 activity : Caspase 3/7-mediated apoptosis was measured using a Caspase-Glo assay kit (Promega, WI, USA, G8091) as previously described 23 . FA uptake assay: Real-time FA uptake was determined using a QBT Fatty Acid Uptake Assay Kit (Molecular Devices, CA, USA, R6132) according to the manufacturer’s instructions.…”

“…Numerous studies support a role for de novo lipogenesis in oncogenesis 27 , 30 . We and others have shown that MYC or MYCN [MYC(N)] promotes FA synthesis by cooperating with Mondo A–sterol regulatory element-binding protein 1 (SREBP1) or directly activating transcription of key lipogenic enzymes, including acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase (SCD1) 18 , 23 , 31 . Recently developed FA synthesis inhibitors (e.g., ACC inhibitor ND-646 32 ; FASN inhibitors TVB-2640 and orlistat 22 , 33 ; and SCD1 inhibitor A939572 34 ) show varying degrees of anti-tumor activity in preclinical models.…”

ROR activation by Nobiletin enhances antitumor efficacy via suppression of IκB/NF-κB signaling in triple-negative breast cancer

“…The core clock components have shown varying cross-talks with factors involved in tumorigenesis such as cell cycle, DNA damage response, cell migration, and metastasis [ 25 , 29 , 31 , 32 ]. Although it has been postulated that the clock largely functions as a tumor suppressor, individual core components show variable effects in cancers, and in some instances appear to promote cancer [ 33 – 36 ]. However, growing evidence strongly suggests anticancer functions of RORs specifically.…”