Table 1.

Colony formation of RLE, LKR or H5800 cells in soft agar upon the treatments.

Cell Type	No. of seeded cells	No. of Colonies	SD
RLE	5,000	0	0
RLE (nicotine)	5,000	0	0
RLE (NNK)	5,000	44	±0.2
RLE (nicotine + NNK)	5,000	67	±1.8
LKR	5,000	21	±3.5
LKR (nicotine)	5,000	26	±0.3
LKR (NNK)	5,000	76	±0.3
LKR (nicotine + NNK)	5,000	99	±0.3
H5800	5,000	64	±4.8
H5800 (nicotine)	5,000	72	±5.2
H5800 (NNK)	5,000	135	±6.1
H5800 (nicotine + NNK)	5,000	151	±5.6

RLE (rat lung epithelial), LKR (murine lung cancer) and H5800 (human lung cancer) cells were cultured in soft agar in the presence or absence of nicotine, NNK or both for 2 weeks. Five microliter of fresh medium containing the drugs was added into the cultures every 4 days.

SD: standard deviation over 5 independent experiments.