G(1)/S but not G(0)/G(1)cell fraction is related to 5-fluorouracil cytotoxicity.
BACKGROUND
Bromodeoxyuridine (BrdU) cell cycle analysis using flow cytometry is of clinical interest for making treatment decisions or for predicting response and survival, through proliferation rate (labeling index or S-phase fraction) assessment or T(pot) calculation. Thymidylate synthase expression was tested in vitro, in vivo, and clinically as a prognostic factor for 5-fluorouracil (5FU) sensitivity. However, results were still controversial. Moreover, we had reported that 5FU sensitivity was related to the labeling index of untreated cell cultures.


METHODS
We used six human cancer cell lines that exhibited a wide range of 5FU sensitivity. Cell cycle analysis was performed using flow cytometry monovariate propidium iodide (PI) analysis and bivariate distributions of BrdU incorporation versus DNA content. 5FU sensitivity was assayed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) colorimetric assay.


RESULTS
In all cell lines, 5FU exposure resulted in a statistically significant G(1)/S accumulation. No statistically significant relationship was seen between G(0)/G(1) delay determined by monovariate analysis and 5FU sensitivity. However, 5FU sensitivity was statistically correlated to the labeling index and G(1)/S subpopulation assessed with bivariate analysis using BrdU incorporation versus DNA content.


CONCLUSIONS
Cellular proliferation parameters using BrdU incorporation are more informative than PI for in vitro 5FU sensitivity. Because BrdU incorporation could be assessed clinically, it could also be informative for 5FU clinical response prediction.
Laboratoire de Recherche en Oncologie, Centre Alexis Vautrin, F-54511 Vandoeuvre-les-Nancy Cedex, France.
J-F
JF
Mirjolet
C
C
Didelot
M
M
Barberi-Heyob
J-L
JL
Merlin
D000230:Adenocarcinoma; D000963:Antimetabolites; D000964:Antimetabolites, Antineoplastic / Q000633:toxicity*; D001943:Breast Neoplasms; D001973:Bromodeoxyuridine; D004396:Coloring Agents; D005260:Female; D005434:Flow Cytometry; D005472:Fluorouracil / Q000633:toxicity*; D016193:G1 Phase / Q000187:drug effects*; D006258:Head and Neck Neoplasms; D006801:Humans; D010190:Pancreatic Neoplasms; D011419:Propidium; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D016196:S Phase / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects
D000963:Antimetabolites; D000964:Antimetabolites, Antineoplastic; D004396:Coloring Agents; D011419:Propidium; D001973:Bromodeoxyuridine; D005472:Fluorouracil