Synergistic cytotoxicity in solid tumor cell lines between N-(4-hydroxyphenyl)retinamide and modulators of ceramide metabolism.

Abstract

BACKGROUND:

We previously reported that N-(4-hydroxyphenyl)retinamide (4-HPR, fenretinide) treatment caused large increases of ceramide levels in neuroblastoma cell lines and induced cell death by a combination of apoptosis and necrosis through p53 (also known as TP53)-independent and caspase-independent pathways. Our goal was to determine if several molecules that inhibit enzymes involved in ceramide metabolism-L-threo-dihydrosphingosine (safingol), d, l-threo-1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol (PPMP), and tamoxifen-enhanced 4-HPR-mediated cytotoxicity and/or affected ceramide levels.

METHODS:

Cellular lipids were quantified by radiolabeling and thin-layer chromatography. Cytotoxicity and cytotoxic synergy (expressed as combination index, where combination index <1 indicates synergy and >1 indicates antagonism) were measured in cultured cancer cell lines with the use of a fluorescence-based assay of cell viability employing digital imaging microscopy. Statistical tests were two-sided.

RESULTS:

4-HPR increased ceramide levels by de novo synthesis. Safingol (1-4 microM) was incorporated into a stereochemical variant of ceramide and synergized with a 3:1 molar ratio of 4-HPR (3-12 microM), to produce a 100-fold to 10 000-fold (2 to 4 logs) increase in cytotoxicity relative to 4-HPR alone in neuroblastoma (combination index <0.1), lung (combination index <0.1-0.2), melanoma (combination index <0.1-0.2), prostate (combination index <0.1-1.0), colon (combination index 0.1-0.3), breast (combination index = 0.1-0.5), and pancreas (combination index = 0.2) cell lines, including p53 mutant and alkylator-resistant cell lines. The 4-HPR and safingol combination was cytotoxic in low-oxygen conditions and was minimally toxic to normal fibroblasts and bone marrow myeloid progenitor cells. Addition of agents that retard ceramide glucosylation and/or acylation, such as PPMP or tamoxifen, to 4-HPR or to the combination of 4-HPR and safingol further increased cytotoxicity to tumor cells.

CONCLUSIONS:

Combinations of 4-HPR and modulators of ceramide metabolism may form the basis for a novel chemotherapy that is functional under hypoxic conditions (e.g., such as those within tumors) and is p53 independent and caspase independent.

• Authors: B J Maurer, L Melton, C Billups, M C Cabot, C P Reynolds
• Journal: Journal of the National Cancer Institute (J Natl Cancer Inst) Vol. 92 Issue 23 Pg. 1897-909 (Dec 06 2000) ISSN: 0027-8874 [Print] United States
• PMID: 11106681 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antineoplastic Agents
• Antineoplastic Agents, Hormonal
• Ceramides
• Enzyme Inhibitors
• Estrogen Receptor Modulators
• Morpholines
• Tumor Suppressor Protein p53
• Tamoxifen
• Fenretinide
• RV 538
• Glucosyltransferases
• ceramide glucosyltransferase
• Protein Kinase C
• Sphingosine
• safingol

Topics

• Antineoplastic Agents (pharmacology)
• Antineoplastic Agents, Hormonal (pharmacology)
• Apoptosis (drug effects)
• Ceramides (metabolism)
• Drug Synergism
• Enzyme Inhibitors (pharmacology)
• Estrogen Receptor Modulators (pharmacology)
• Fenretinide (pharmacology)
• Glucosyltransferases (antagonists & inhibitors)
• Humans
• Morpholines (pharmacology)
• Necrosis
• Neoplasms (drug therapy, enzymology, metabolism)
• Protein Kinase C (antagonists & inhibitors)
• Sphingosine (analogs & derivatives, pharmacology)
• Tamoxifen (pharmacology)
• Tumor Cells, Cultured
• Tumor Suppressor Protein p53 (metabolism)