Abstract
Schweinfurthins are potent inhibitors of cancer cell growth, especially against human central nervous system tumor lines such as SF-295 cells. However, the mechanisms through which these compounds impede cell growth are not fully understood. In an effort to understand the basis for the effects of schweinfurthins, we present a fluorescent schweinfurthin, 3-deoxyschweinfurthin B-like p-nitro-bis-stilbene (3dSB-PNBS), which displays biological activity similar to that of 3-deoxyschweinfurthin B (3dSB). These two schweinfurthins retain the unique differential activity of the natural schweinfurthins, as evidenced by the spindle-like morphological changes induced in SF-295 cells and the unaltered appearance of human lung carcinoma A549 cells. We demonstrate that incubation with 3dSB or 3dSB-PNBS results in cleavage of poly-ADP-ribose polymerase (PARP) and caspase-9, both markers of apoptosis. Coincubation of 3dSB or 3dSB-PNBS with the caspase-9 inhibitor (Z)-Leu-Glu(O-methyl)-His-Asp(O-methyl)-fluoromethylketone prevents PARP cleavage. Therapeutic agents that induce apoptosis often activate cellular stress pathways. A marker for multiple stress pathways is the phosphorylation of eukaryotic initiation factor 2α, which is phosphorylated in response to 3dSB and 3dSB-PNBS treatment. Glucose-regulated protein 78 and protein disulfide isomerase, both endoplasmic reticulum chaperones, are up-regulated with schweinfurthin exposure. Using the fluorescent properties of 3dSB-PNBS and dimethoxyphenyl-p-nitro-bis-stilbene (DMP-PNBS), a control compound, we show that the intracellular levels of 3dSB-PNBS are higher than those of Rhodamine 123 or DMP-PNBS in SF-295 and A549 cells.
Footnotes
This project was supported by the National Institutes of Health National Cancer Institute [Grant 1R41-CA126020-01] (to Terpenoid Therapeutics), the Roy J. Carver Charitable Trust as a Research Program of Excellence, and the Roland W. Holden Family Program for Experimental Cancer Therapeutics.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
ABBREVIATIONS:
- NCI
- National Cancer Institute
- 3dSB-PNBS
- 3-deoxyschweinfurthin B-like p-nitro bis-stilbene
- 3dSB
- 3-deoxyschweinfurthin B
- PARP
- poly-ADP-ribose polymerase
- eIF2α
- eukaryotic initiation factor 2α
- GRP78
- glucose-regulated protein 78
- PDI
- protein disulfide isomerase
- ER
- endoplasmic reticulum
- RIPA
- radioimmunoprecipitation assay
- UPR
- unfolded protein response
- DMP-PNBS
- 3,4-dimethoxyphenyl p-nitro bis-stilbene
- Y-27632
- (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride
- OSW-1
- (3β,16β)-16-[[2-O-acetyl-3-O-[2-O-(4-methoxybenzoyl)-β-d-xylopyranosyl]-α-l-arabinopyranosyl]oxy]-3,17-dihydroxy-cholest-5-en-22-one.
- Received December 6, 2011.
- Accepted March 29, 2012.
- Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics
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