Modification of lung tumor growth by hyperoxia.

The effects of hyperoxia on lung tumor development were examined in mice and rats. In mice, exposure to 70% O2 prevented the development of urethan- or 3-methylcholanthrene-induced lung tumors. Dietary antioxidants [butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)] were unable to prevent the inhibition of tumor development by oxygen, although BHT retained its capability to enhance tumor development in mouse lung. In visible-size tumors, oxygen did not depress DNA synthesis. Oxygen also reduced the number of pulmonary metastatic nodules after i.v. injection of mammary gland-derived carcinoma cells, but failed to inhibit growth of murine lung carcinoma or murine melanoma-derived cell lines. Rats treated with one single intratracheal instillation of 3-methylcholanthrene developed multiple lung lesions; their growth could be prevented by exposure of the animals to 40 or 70% O2. It is concluded that hyperoxia prevents development of transformed cells in vivo in the lung and may affect adversely the growth of selected cell lines metastatic to the lung.