Effects of physiological oxygen concentration on human tumor colony growth in soft agar

Cloning efficiencies of 67 fresh human tumor specimens, consisting of 29 ovarian, 10 lung, and 7 each of colon, breast, mesenchymal, and miscellaneous tumors, from 58 patients were studied using the technique of Hamburger and Salmon to evaluate the effect of incubation in a 5% rather than 20% oxygen environment. Under the low-oxygen tension, carcinomas exhibited an average of 170% increase in cloning efficiency (p less than 0.01). The number of carcinomas forming at least 30 colonies/dish increased from 22 to 27. Mesenchymal tumors, however, exhibited a 20% decrease in cloning efficiency (not significant). A mixture of 5% oxygen, 5% carbon dioxide, and 90% nitrogen gives a higher cloning efficiency than 20% oxygen, 5% carbon dioxide, and 75% nitrogen for certain human carcinomas in semisolid agar.