Inhibition of DNA topoisomerase I activity and induction of apoptosis by thiazacridine derivatives.
Thiazacridine derivatives (ATZD) are a novel class of cytotoxic agents that combine an acridine and thiazolidine nucleus. In this study, the cytotoxic action of four ATZD were tested in human colon carcinoma HCT-8 cells: (5Z)-5-acridin-9-ylmethylene-3-(4-methylbenzyl)-thiazolidine-2,4-dione - AC-4; (5ZE)-5-acridin-9-ylmethylene-3-(4-bromo-benzyl)-thiazolidine-2,4-dione - AC-7; (5Z)-5-(acridin-9-ylmethylene)-3-(4-chloro-benzyl)-1,3-thiazolidine-2,4-dione - AC-10; and (5ZE)-5-(acridin-9-ylmethylene)-3-(4-fluoro-benzyl)-1,3-thiazolidine-2,4-dione - AC-23. All of the ATZD tested reduced the proliferation of HCT-8 cells in a concentration- and time-dependent manner. There were significant increases in internucleosomal DNA fragmentation without affecting membrane integrity. For morphological analyses, hematoxylin-eosin and acridine orange/ethidium bromide were used to stain HCT-8 cells treated with ATZD, which presented the typical hallmarks of apoptosis. ATZD also induced mitochondrial depolarisation and phosphatidylserine exposure and increased the activation of caspases 3/7 in HCT-8 cells, suggesting that this apoptotic cell death was caspase-dependent. In an assay using Saccharomyces cerevisiae mutants with defects in DNA topoisomerases 1 and 3, the ATZD showed enhanced activity, suggesting an interaction between ATZD and DNA topoisomerase enzyme activity. In addition, ATZD inhibited DNA topoisomerase I action in a cell-free system. Interestingly, these ATZD did not cause genotoxicity or inhibit the telomerase activity in human lymphocyte cultures at the experimental levels tested. In conclusion, the ATZD inhibited the DNA topoisomerase I activity and induced tumour cell death through apoptotic pathways.
Department of Physiology and Pharmacology, Federal University of Ceará, Fortaleza, Ceará, Brazil.
Francisco W A
FW
Barros
Daniel P
DP
Bezerra
Paulo M P
PM
Ferreira
Bruno C
BC
Cavalcanti
Teresinha G
TG
Silva
Marina G R
MG
Pitta
Maria do C A
Mdo C
de Lima
Suely L
SL
Galdino
Ivan da R
Ida R
Pitta
Letícia V
LV
Costa-Lotufo
Manoel O
MO
Moraes
Rommel R
RR
Burbano
Temenouga N
TN
Guecheva
João A P
JA
Henriques
Cláudia
C
Pessoa
D000166:Acridines / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology*; D020552:Comet Assay; D053938:DNA Fragmentation / Q000187:drug effects*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006801:Humans; D008856:Microscopy, Fluorescence; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism; D045162:Thiazolidinediones / Q000494:pharmacology*
D000166:Acridines; D045162:Thiazolidinediones; D019098:Telomerase; D020169:Caspases; D004264:DNA Topoisomerases, Type I