Oxyphenisatin acetate (NSC 59687) triggers a cell starvation response leading to autophagy, mitochondrial
Bethanie L Morrison1, Michael E Mullendore, Luke H Stockwin
1Drug Mechanism Group, Biological Testing Branch, Developmental Therapeutics Program, SAIC-Frederick Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, 21702.
Abstract:
Oxyphenisatin (3,3-bis(4-hydroxyphenyl)-1H-indol-2-one) and several structurally related molecules have been shown to have in vitro and in vivo antiproliferative activity. This study aims to confirm and extend mechanistic studies by focusing on oxyphenisatin acetate (OXY, NSC 59687), the pro-drug of oxyphenisatin. Results confirm that OXY inhibits the growth of the breast cancer cell lines MCF7, T47D, HS578T, and MDA-MB-468. This effect is associated with selective inhibition of translation accompanied by rapid phosphorylation of the nutrient sensing eukaryotic translation initiation factor 2α (eIF2α) kinases, GCN2 and PERK. This effect was paralleled by activation of AMP-activated protein kinase (AMPK) combined with reduced phosphorylation of the mammalian target of rapamycin (mTOR) substrates p70S6K and 4E-BP1. Microarray analysis highlighted activation of pathways involved in apoptosis induction, autophagy, RNA/protein metabolism, starvation responses, and solute transport. Pathway inhibitor combination studies suggested a role for AMPK/mTOR signaling, de novo transcription and translation, reactive oxygen species (ROS)/glutathione metabolism, calcium homeostasis and plasma membrane Na(+) /K(+) /Ca(2+) transport in activity. Further examination confirmed that OXY treatment was associated with autophagy, mitochondrial dysfunction, and ROS generation. Additionally, treatment was associated with activation of both intrinsic and extrinsic apoptotic pathways. In the estrogen receptor (ER) positive MCF7 and T47D cells, OXY induced TNFα expression and TNFR1 degradation, indicating autocrine receptor-mediated apoptosis in these lines. Lastly, in an MCF7 xenograft model, OXY delivered intraperitoneally inhibited tumor growth, accompanied by phosphorylation of eIF2α and degradation of TNFR1. These data suggest that OXY induces a multifaceted cell starvation response, which ultimately induces programmed cell death.
Insights
Oxyphenisatin acetate (OXY) inhibits breast cancer cell growth by selectively blocking translation and activating cell death pathways. This multifaceted starvation response leads to programmed cell death, offering a potential new therapeutic strategy.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Oxyphenisatin and related compounds exhibit antiproliferative effects.
- Oxyphenisatin acetate (OXY) is a pro-drug of oxyphenisatin, necessitating further mechanistic investigation.
Purpose of the Study:
- To confirm and extend mechanistic studies on OXY's antiproliferative activity.
- To elucidate the molecular pathways involved in OXY-induced cell death.
Main Methods:
- Cell viability assays on breast cancer cell lines (MCF7, T47D, HS578T, MDA-MB-468).
- Western blotting to assess protein phosphorylation (eIF2α, GCN2, PERK, AMPK, mTOR substrates).
- Microarray analysis to identify activated pathways.
- Pathway inhibitor studies.
- Autophagy, mitochondrial dysfunction, ROS, and apoptosis assays.
- In vivo xenograft studies in mice.
Main Results:
- OXY inhibited growth in all tested breast cancer cell lines.
- OXY selectively inhibited translation via eIF2α kinase phosphorylation (GCN2, PERK).
- OXY activated AMP-activated protein kinase (AMPK) and inhibited mTOR signaling.
- Microarray revealed OXY activates apoptosis, autophagy, starvation responses, and solute transport pathways.
- OXY induced autophagy, mitochondrial dysfunction, ROS generation, and both intrinsic/extrinsic apoptosis.
- OXY inhibited tumor growth in an MCF7 xenograft model.
Conclusions:
- OXY induces a multifaceted cell starvation response.
- This response ultimately leads to programmed cell death.
- OXY demonstrates potential as an anti-cancer therapeutic agent.
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