Mast-cell-deficient W/Wv mice exhibit a decreased rate of tumor angiogenesis.

The role of host mast cells in tumor-associated angiogenesis was investigated by comparing the angiogenic response of genetically mast-cell-deficient W/Wv mice and mast-cell-sufficient +/+ littermate mice to s.c. growing B16-BL6 tumors. The angiogenic response was found to be slower and initially less intense in W/Wv mice than in +/+ mice. Fewer W/Wv mice than +/+ mice developed spontaneous lung metastases and W/Wv mice exhibited fewer lung metastases per mouse. Bone-marrow repair of the mast-cell deficiency restored the angiogenic response of W/Wv mice and also restored the incidence of hematogenous metastases to approach that of +/+ mice. Differences in lymphatic metastasis were not detected between W/Wv and +/+ mice. These results demonstrate a role for mast cells in vivo during tumor angiogenesis, and suggest a role also for host mast cells in hematogenous metastasis.