The effect of cortisol on the growth of a transplantable mouse fibrosarcoma.

Many studies have established the fact that cortisol and cortisone inhibit the growth of tumors of lymphoid origin (8,19, 20, 23, 24). However, the effect of these steroids on other types of tumors is by no means certain. In most instances in which any effect on tumor growth is observed, these corticoids have been found to inhibit the tumors, but there have also been a few reports (5, 26) of en hancement of tumor growth. On the other hand, except for the lymphoid tumors, removal of the adrenal glands slows tumor growth in all cases where an effect is seen (4, 10, 14, 15, 17, 22, 26). This subject has been recently reviewed by Noble (18). There are a number of possible explanations for the variability of the reported actions of these corticoids on tumor growth. In some cases, no effect of cortisol or cortisone can be seen in intact ani mals, whereas a measurable effect of the hormones may be observed after adrenalectomy (21, 26). Qualitative differences in the response of tumors to corticoids may represent differences in the tumorhost relationships. Studies on the effect of these hormones on heterologous tumor transplants have shown that the host response may profoundly af fect the final growth of the tumor (1, 9, 12,13, 28). Interpretation of the data in studies of tumor growth is frequently difficult. The density of tu mor tissue varies with the degree of necrosis, for example, so that tumor weight may not be a true measure of the inhibition or enhancement of growth. In addition, no matter what index of growth is used, a high degree of variability is found among tumors transplanted into different animals, so that it is often difficult to obtain statistically significant data (25). A further complication is the fact that a wide range of hormone doses has been used, with many workers paying little attention to