(A) Experimental protocols for promotion of NNK-induced lung cancer. 7-week-old male A/J mice were MTS-exposed using two different regimens starting 1 week after NNK injection. Tumor development was analyzed 9 months later.
(B) Effect of MTS exposure on weight gain in A/J mice. Results are means ± S.E. (air control: n = 12; 2 cig./day: n = 12; 4 cig./day: n = 13).
(C) Lung appearance (left panels) and histology (H&E stain; right panels) in A/J mice 9 months after initiation of the NNK + MTS protocol.
(D) Lung tumor multiplicity and incidence were determined by serial sectioning at 350 μm intervals. Incidence = number of tumor-bearing mice divided by the number of mice in each group. Results are means ± S.E. (n: as described in panel B). Significant difference, *P < 0.03.
(E) Histological appearance of adenoma (left panel) and adenocarcinoma with bronchial invasion (right panel) in A/J mice given NNK and 4 cig./day MTS. Scale bar = 100 μm. See also Figure S1.