Growth of pulmonary metastases of B16 melanoma in mast cell-free mice.

The relationship of mast cells to tumor growth has been debated but not elucidated. The existence of a mast cell-free animal, the W/Wv mouse, provides a model in which tumor metastasis can be studied with special reference to host tissues and their mast cell content rather than to the adhesiveness of the tumor cell itself. Both hind footpads of 30 W/Wv mice and 30 control mice (+/+) were injected with 2 X 10(5) cells of B16-F10 melanoma cells. The left paw received 1000 rads orthovoltage radiation 12 hr before tumor inoculation. Growth of tumors in both paws was recorded. Ten animals from each group were killed on Day 31 after tumor inoculation, and the remaining animals were kept until they died. Autopsy was performed in all animals, and patterns of metastasis were recorded. Results showed that (1) preinoculation radiation significantly slowed tumor growth in the left paw (P = 0.0009), and (2) lung metastases were present in 4 of 10 W/Wv mice, but in none of 10 +/+ mice killed after 31 days (P = 0.05). Overall, 17 of 25 W/Wv mice and 8 of 26 +/+ mice had lung metastases (P = 0.008).