Modification of immunogenic tumor growth by adrenalectomy in a syngeneic murine system

The immunosuppressive action of adrenal glucocorticosteroids is well-known, and depressed cell-mediated immunity and adrenal cortical hyperplasia have been described in tumor-bearing animals. This study was designed to evaluate the effect of removing the source of lympholytic steroids by adrenalectomy upon tumor growth rate, thymus weight, and thymocyte incorporation of iodine 125 (125I) deoxyuridine into DNA. Newly derived methylcholanthrene-induced immunogenic fibrosarcomas were used in male syngeneic mice. Log dosages of 10(4), 10(5), and 10(6) viable tumor cells as single cell suspension were injected subcutaneously into the popliteal space of adrenalectomized and control mice. Tumor size was followed serially with caliper measurements, and the animals were killed 4 weeks after inoculation. Adrenalectomized mice inoculated with 10(4) cells had smaller tumors (P less than 0.02), heavier thymi (P less than 0.01), and more thymic DNA synthesis (P less than 0.05) than their tumor-bearing controls. No differences were seen between populations receiving 10(5) or 10(6) tumor cell inoculations. A second experiment was carried out in which intact controls, adrenalectomized animals, and sham adrenalectomy animals were inoculated with 10(4) tumor cells and killed 28 days later. Tumor growth rate and volume were significantly decreased for the adrenalectomized mice, which had higher thymus weights and DNA synthesis. These findings suggest that pretreatment adrenalectomy slows the growth of antigenic tumor cells and prevents thymic involution after tumor growth in a syngeneic murine system.