fenretinide and Leukemia--Myeloid

N-(4-hydroxyphenyl) retinamide (Fenretinide, 4-HPR) inhibits cell growth by inducing apoptosis in numerous tumor cell types including all-trans-retinoic acid (ATRA)-resistant tumor cells. However, the mechanism(s) by which 4-HPR mediates its anti-proliferative effects remains unclear. Here, we determined whether 4-HPR induced growth inhibition and gene expression involve retinoid receptors in human acute myeloid leukemia (AML) cells (HL-60). We treated HL-60 and ATRA-resistant HL-60 (HL-60R) cells that express mutated RARalpha and very low levels of RARbeta, RARgamma and RXRalpha with 4-HPR (2 microM) for 3 days. 4-HPR showed significant anti-proliferative effects against both cell types and induced growth inhibition (92.7%) in HL-60 cells. However, at the same dose, 4-HPR induced only 53.4% growth inhibition in HL-60R cells. Growth inhibition by 4-HPR was significantly enhanced in HL-60R cells that were retroviraly transduced to express human RARalpha, RARbeta or RXRalpha (95.6%, 97.1%, and 75.6%, respectively), in comparison to HL-60R cells (P < 0.05), but not in HL-60R cells expressing RARgamma. Although ATRA and 4-HPR induced expression of CYP26, an ATRA-inducible gene encoding a cytochrome P450 enzyme, in HL-60 cells, both retinoids failed to induce CYP26 in HL-60R cells. However, induction of CYP26 mRNA by 4-HPR was restored in HL-60R cells expressing RARalpha and RARgamma, but not RARbeta and RXRalpha. In conclusion, our data suggest that nuclear retinoid receptors are involved in 4-HPR-induced growth inhibition and gene expression, and that 4-HPR can mediate its anti-proliferative effects through retinoid receptor-dependent mechanisms in HL-60 cells.

Topics: Acute Disease; Cell Proliferation; Cytochrome P-450 Enzyme System; Fenretinide; Gene Expression Regulation, Neoplastic; HL-60 Cells; Humans; Leukemia, Myeloid; Receptors, Retinoic Acid; Retinoic Acid 4-Hydroxylase; Retinoic Acid Receptor alpha; Retinoic Acid Receptor gamma; Retinoid X Receptor alpha; RNA, Messenger

Mer-NF8054X is a new type of steroid whose structure has been established as 11-oxo-18, 22-cycloergosta-6, 8(14)-diene-3beta, 5beta, 9beta, 23S-tetraol (an 18, 22-cycloergostane), which has been reported to have antifungal activity against Aspergillus fumigatus. However, other biological activities are unknown. Herein, we reported that Mer-NF8054X inhibited cell growth of HL60 human leukemia cells, when used either singly or in combination with retinoic acid (RA). In addition, Mer-NF8054X alone induced differentiation and apoptosis of HL60 cells. The induction of differentiation of HL60 cells by Mer-NF8054X was synergistic in combination with RA. On the other hand, Emesterone A, an analogue of Mer-NF8054X which is missing a hydroxy residue from the third position, showed much lower activity than Mer-NF8054X on the inhibition of cell growth and the induction of cell differentiation and apoptosis. However, Emesterone B, an analogue of Emesterone A which is missing a hydroxy residue from the fifth position, showed higher activity than Emesterone A but lower activity than Mer-NF8054X when examined for the inhibition of cell growth and the induction of cell differentiation and apoptosis. These results suggested that Mer-NF8054X and its analogs may be a new type of differentiation inducing agent. The hydroxy residue at the third position or fifth position in Mer-NF8054X may be necessary, but not essential, for inhibition of growth and induction of both differentiation and apoptosis of HL60 cells. In addition, Mer-NF8054X enhanced the differentiation of HL60 cells induced by RA. Based on these results, Mer-NF8054X may have utility in the clinic in combination with RA for leukemia patients.

Topics: Antineoplastic Agents; Apoptosis; Ascomycota; Aspergillus; Cell Differentiation; Cell Division; Cell Size; DNA; DNA Fragmentation; Dose-Response Relationship, Drug; Drug Synergism; Fenretinide; HL-60 Cells; Humans; Ketosteroids; Leukemia, Myeloid; Macrophages; Monocytes; Tretinoin

Among the Retinoic Acid (RA) derivatives, retinamides, and in particular N-(4-hydroxyphenyl) retinamide (4-HPR), are currently being investigated in selected cases of cancer chemoprevention. The cellular target range, however, seems to be limited, as cells of hemopoietic origin are virtually incapable of terminal differentiation upon addition of the compound. We have reconsidered the effect of 4-HPR on HL-60 cells by taking advantage of a mutant clone, generated in our laboratory, unresponsive to RA but highly responsive to dimethylsulfoxide (DMSO). We show here that this clone, upon addition of 4-HPR, although unable of undergoing full differentiation, shows considerable reduction of clonal growth. Moreover, the combination of 4-HPR and RA resulted in a much greater effect than the administration of 4-HPR alone. We suggest that 4-HPR and RA, at least in terms of mediating growth inhibition, may follow different metabolic pathways.

Topics: Animals; Cell Differentiation; Cell Division; Clone Cells; Dimethyl Sulfoxide; Drug Resistance; Drug Screening Assays, Antitumor; Fenretinide; Flow Cytometry; Leukemia, Myeloid; Mice; Phenotype; Tretinoin; Tumor Cells, Cultured