Table 2

Percentage of apoptosis and viable cell number × 106 after treatment of A549 cells with flavopiridol

Low doses of flavopiridol require prolonged exposure to achieve maximal cytotoxicity in a representative experiment in A549 cells. Cells were treated with DMSO or the indicated doses. At time 0 of flavopiridol treatment, the cell count was 1.28 × 106 with <1% apoptosis.
T = 0: <1 (1.28)24/24a24/72b72/72c72/120d120/120e
DMSO<1 (3.63)<1 (12.6)<1 (15.6)<1 (ND)f3 (ND)
300 nm3 (1.38)<1 (2.47)27 (0.65)12 (0.30)58 (0.22)
400 nm3 (1.35)3 (1.37)38 (0.72)62 (0.14)61 (0.14)
500 nm2 (1.50)30 (0.80)42 (0.71)56 (0.17)60 (0.17)
1000 nm5 (1.43)53 (0.55)62 (0.65)34 (0.12)67 (0.19)
1500 nm4 (1.35)57 (0.45)50 (0.47)33 (0.12)53 (0.19)
2000 nm2 (1.03)55 (0.39)43 (0.39)43 (0.18)50 (0.12)
  • a 24/24, cells were treated for 24 h and collected at 24 h.

  • b 24/72, cells were treated for 24 h and collected at 72 h.

  • c 72/72, cells were treated for 72 h and collected at 72 h.

  • d 72/120, cells were treated for 72 h and collected at 120 h.

  • e 120/120, cells were treated for 120 h and collected at 120 h. At doses <500 nm, continuous exposure for 72 h produced more cytotoxicity than only 24 h of exposure; at doses >500 nm, 24 and 72 h of exposure are equivalent, if cells are analyzed at 72 h. Removal of drug at 72 h does not reverse flavopiridol-mediated cell death, and cytotoxicity continues and is even more marked after analysis at 120 h. (At doses of 1000 nm and above, the percentage of apoptosis does not significantly increase after 72 h, suggesting a nonapoptotic component of the continued cell death observed in these samples). The percentage of apoptosis was determined by TUNEL assay.

  • f ND, not determined.