Characterization of Sigma Receptor Mediated Apoptosis in Breast Tumor Cells
Abstract
We have shown that chronic exposure of tumor cells to sigma-2 agonists produces apoptosis and that these compounds potentiate effects of anti-neoplastic agents. To determine if this effect is mediated by ceramides, breast tumors (MCF-7/Adr-, T47D) were incubated with 3Hpalmitic acid to label sphingolipids. Cells were then incubated with or without sigma-2 agonists (CB 184, BD737) for 24hr.. Treatment with sigma-2 agonists increased labeled ceramide 2-4 fold over control, and in most experiments, a concomitant decrease in labeled sphingomyelin was observed from TLC analysis. These effects were diminished by the sigma-2 receptor antagonist AC927. When analyzed by reverse phase-HPLC coupled with atmospheric pressure chemical ionization-mass spectrometry, the ratio of C-16 ceramide to other sphingolipids is significantly increased in treated-cells compared with controls, in a dose-dependent manner. To determine the mechanism of sigma-2 receptor control of sphingolipid metabolism, assays for sphingomyelinase and sphingolipid ceramide N- deacylase (SCDase) were developed using tumor cell detergent-extracts (T47D, SKBr3 breast tumors cells). Our current findings suggest that sigma-2 receptors may modulate SCDase activity producing sphingosylphosphorylcholine. SCDase also posseses an acylase activity and can generate ceramide from sphingosine. Studies are underway to determine if sigma-2 receptor activation of SCDase is the source of increased ceramide that we have observed in numerous cell lines.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2000
- Accession Number
- ADA387795
Entities
People
- Keith W. Crawford
Organizations
- Howard University