2-Hydroxy-oleic acid does not activate sphingomyelin synthase activity

Abstract

Edited by George M. Carman 2-Hydroxy-oleic acid (2OHOA) is a potent anticancer drug that induces cancer cell cycle arrest and apoptosis. Previous studies have suggested that 2OHOA's anticancer effect is mediated by SMS activation in cancer cells, including A549 and U118 cells. To confirm this phenomenon, in this study, we treated both A549 and U118 cells with 2OHOA and measured SMS activity. To our surprise, we found neither 2OHOA-mediated SMS activation nor sphingomyelin accumulation in the cells. However, we noted that 2OHOA significantly reduces phosphatidylcholine in these cells. We also did not observe 2OHOAmediated SMS activation in mouse tissue homogenates. Importantly, 2OHOA inhibited rather than activated recombinant SMS1 (rSMS1) and rSMS2 in a dose-dependent fashion. Intragastric treatment of C57BL/6J mice with 2OHOA for 10 days had no effects on liver and small intestine SMS activities and plasma sphingomyelin levels. The treatment inhibited lysophosphatidylcholine acyltransferase (LPCAT) activity, consistent with the aforementioned reduction in plasma phosphatidylcholine. Because total cellular phosphatidylcholine is used as a predictive biomarker for monitoring tumor responses, the previously reported 2OHOA-mediated cancer suppression could be related to this phosphatidylcholine reduction, which may influence cell membrane structure and properties. We conclude that 2OHOA is not a SMS activator and that its anticancer property may be related to an effect on phosphatidylcholine metabolism.2-Hydroxy-oleic acid (2OHOA) 3 is a potent anticancer drug that induces cancer cell cycle arrest (1), differentiation (2), and death (3-5). The European Medicines Agency has designated 2OHOA as an orphan drug for the treatment of glioma.However, the underlying mechanisms leading to cancer cell death remain largely unknown, although it has been reported that the effect was mediated by activation of sphingomyelin synthase (SMS) in cancer cells and accumulation of cell sphingomyelin levels (6).The biochemical synthesis of SM occurs through the action ofserinepalmitoyltransferase,3-ketosphinganinereductase,ceramide synthase, dihydroceramide desaturase, and SMS (7). SMS catalyzes the conversion of ceramide to sphingomyelin. The SMS gene family consists of three members, SMS1, SMS2, and SMS-related protein (SMSr). SMS1 is found in the trans-Golgi complex, whereas SMS2 is predominantly found in the plasma membranes (8,9). SMSr, the third member of the gene family, has no SMS activity but catalyzes the synthesis of ceramide-phosphoethanolamine in the ER lumen (8, 10). We and another research group reported that systemic SMS1 KO exhibited moderate neonatal lethality (11, 12) (i.e. 25% of homozygotes die during the first 3 weeks; the remainder can grow to adulthood). On the other hand, SMS2 KO mice display no obvious abnormalities and grow to adulthood (13). We and others have suggested that SMS2 might be a therapeutic target for metabolic diseases, including type 2 diabetes, fatty liver, and atherosclerosis (14 -20). However, ...

LC-HRMS based approach to identify novel sphingolipid biomarkers in breast cancer patients

“…A reduction in the levels of sphingomyelins has been reported in colon cancer tissues 52 . Reduced plasma levels of sphingomyelins SM(16:0), SM(24:0) and SM(24:1) have also been observed in A549 and U118 cancer cell lines 53 . Contrary to our results, Nagahashi and colleagues reported high concentration of sphingomyelins in breast tumor samples 10 .…”

The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA

“…Finally, the fact that induction of SM synthesis by 2OHOA was observed only in cells expressing SMS1 (independently of SMS2 expression) suggests a specific and direct interaction of 2OHOA with SMS1, particularly considering the short times of treatment needed to produce this increase in SMS activity. A recently published study questions the activation of SMS activity in response to treatment with 2OHOA [38]. However, substantial differences in the protocol used in this publication compared to previous studies [19] might well explain the divergent results obtained, such as the method of dissolution of the drug or the direct addition of the substrate NBD-Cer instead of adding it in the form of LUVs, among others.…”

Ceramide/Sphingomyelin Rheostat Regulated by Sphingomyelin Synthases and Chronic Diseases in Murine Models

“…However, increased SM/ceramide ratio has also been implicated in autophagy-dependent cell death. In SF767 human glioma cells, 2-hydroxyoleic acid (2OHOA), which is a potent antitumor compound and indirect SMS activator, 69 70 induces glioma cell differentiation into mature glial cells and subsequent autophagy-dependent cell death by increasing SMS activity and SM levels. 71 In addition, accumulation of high SM levels due to dysfunction of ASM, whose gene ( SMPD1 ) mutation is responsible for Niemann Pick disease type A (NPA), 72 induces lysosomal impairment and accumulation of autophagolysosomes, leading to autophagy-dependent cell death.…”