A distinct function of the retinoblastoma protein in the control of lipid composition identified by lipidomic profiling

Abstract

Here, by combining lipidomics with transcriptome analysis, we demonstrate that Rb depletion in mouse embryonic fibroblastss induces significant alterations in their lipid composition. We discovered that Rb depletion induced increase in lysophosphatidylserine, diacylglycerol (DAG), fatty acid (FA), acylcarnitine, phosphatidylcholine (PC), arachidonoyl ethanolamine, and decrease in phosphatidylglycerol, monoacylglycerol, without change in total lipid per protein levels. Analysis of the acyl chain composition of DAG, PC and phosphatidylserine revealed increase of saturated and mono-unsaturated acyl chains with specific carbon chain length. Consistently, we observed that Rb depletion increased the levels of fatty acids with the corresponding carbon chain length and number of carbon–carbon double bondssuch as myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0) and all forms of FA 18:1. Microarray analysis revealed that Rb depletion induced significant upregulation of enzymes involved in elongation and desaturation of fatty acids. Among these, we found that elongation of long chain fatty acid family member 6 (Elovl6) and stearoyl-CoA desaturase 1 (Scd1) are the most robustly controlled by Rb possibly through E2F and sterol regulatory element-binding protein transcription factors. Depletion of Elovl6 or Scd1 significantly suppressed colony formation, sphere formation and xenograft tumor growth of Rb-deficient tumor cells. Suppression of self-renewal by the SCD1 inhibitor was rescued upon supplementation of the mono-unsaturated fatty acids generated by this enzyme. This study suggests a novel role for Rb in suppressing the malignant progression of tumors by controlling the lipid composition.

Metabolite systems profiling identifies exploitable weaknesses in retinoblastoma

“…While 20% of healthy secretion metabolites were supported via either experimental validation or literature curation, 22% of RB model metabolites were validated (Table S5). Furthermore, a recent study done on mouse embryonic fibroblast cells also identified that upon knockdown of RB gene resulted in significant changes of cellular lipid composition [64]. However, in the current study, majority of the model predictions with respect to secretion profile was for lipid class (i.e., 38%, Fig.…”

“…3). Furthermore, a recent study done on mouse embryonic fibroblast cells also identified that upon knockdown of RB gene resulted in significant changes of cellular lipid composition [64]. Herein, we would like to emphasize on the need for targeted lipidomics experimentation for identification and validation of RB-specific metabolites that could aid in rapid medical diagnostics.…”

Current Challenges and Opportunities in Treating Glioblastoma

“…Increased ELOVL6 mRNA expression was found in triple-negative breast cancer tissue ( Yamashita et al, 2017 ). Additionally, ELOVL6 and lipid composition may be regulated by the RB-E2F transcription factor 1 pathway ( Muranaka et al, 2017 ). An ELOVL6 inhibitor, Compound A, inhibited tumor growth in an in vivo model of squamous cell carcinoma ( Marien et al, 2016 ), and therefore validation and pursuit of ELOVL6 inhibition in GBM is warranted.…”

Differential Effects of 2-Hydroxypropyl-Cyclodextrins on Lipid Accumulation in Npc1-Null Cells

“…Each sphingolipid was measured by LC-MS/MS with the Acquity UPLC system coupled with a 4000QTRAP triple quadrupole mass spectrometer (AB Sciex Pte. Ltd., Tokyo, Japan) equipped with an electrospray ionization source as described previously [48]. Briefly, the Acquity UPLC BEH-C18 reverse-phase column (1.7 µm particle size, 1.0 mm i.d.…”