Antiproliferative and proapoptotic activities of pyranoxanthenones, pyranothioxanthenones and their pyrazole-fused derivatives in HL-60 cells.
BACKGROUND
Synthetic pyranoxanthenones, pyranothioxanthenones and their pyrazole-fused derivatives, which bind to DNA, block the G2 + M-phases of the cell cycle and inhibit the proliferation of ascitic and solid tumor cell lines in vitro, were tested for their ability to induce apoptosis in the HL-60 cell system.


METHODS
Various markers of tumor cell metabolism, apoptosis induction and mitochondrial permeability transition (MPT) were assayed in vitro to evaluate drug cytotoxicity.


RESULTS
All these compounds, and especially the pyrazole-fused pyranoxanthenones 7, 8 and 10, which were effective in the 3-5 microM range and were more potent than the pyranoxanthenones, reduced the proliferation of HL-60 cells at 2 and 4 days. These antitumor drugs inhibited DNA synthesis at 2 h in relation to their ability to block the cellular uptake of purine and pyrimidine nucleosides within 15 min. Internmucleosomal DNA fragmentation, a late marker of apoptosis, was induced in a concentration-dependent manner by 7 and 10 at 24 h. Poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, an early event required for cells committed to apoptosis, was detected within 12 h in HL-60 cells treated with 7 and 10. In accord with the fact that the caspase cascade is responsible for PARP-1 cleavage, 7 and 10 induced the activities of initiator caspases-2 and -9 and effector caspase-3 within 9 h in HL-60 cells. The release of mitochondrial cytochrome c (Cyt c) was also detected within 9 h in HL-60 cells treated with 7 and 10, consistent with the fact that Cyt c is the apoptotic trigger that activates caspase-9. However, 7 and 10 neither caused the rapid collapse of mitochondrial transmembrane potential, nor the mitochondrial swelling linked to MPT.


CONCLUSIONS
Pyrazole-fused pyranoxanthenones are DNA-interacting antiproliferative drugs that do not directly target mitochondria in cell and cell-free systems to induce the intrinsic pathway of apoptosis.
Perchellet
Elisabeth M
EM
Anti-Cancer Drug Laboratory, Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506-4901, USA.
Ward
Mary M
MM
Skaltsounis
Alexios-Leandros
AL
Kostakis
Ioannis K
IK
Pouli
Nicole
N
Marakos
Panagiotis
P
Perchellet
Jean-Pierre H
JP
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D048708:Cell Growth Processes / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D004273:DNA, Neoplasm / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology; D009705:Nucleosides / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011714:Pyrans / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology*; D014966:Xanthenes / Q000494:pharmacology*
D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D009705:Nucleosides; D011714:Pyrans; D011720:Pyrazoles; D014966:Xanthenes; D045304:Cytochromes c; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases