Platelet activation is a significant determinant of spontaneous metastasis but not tumor growth. (A) Serial measurements of tumor volume after transplantation of LLCGFP cells into the dorsal subcutis of control (•, n = 9) and Gαq–/– mice (○, n = 8). There was no significant difference in tumor volumes between wild-type and mutant mice at any time point. Data shown are means with standard deviations. (B) Quantitative analysis of spontaneous pulmonary metastases. Metastatic foci were enumerated 14 days after primary tumor irradiation. Note that spontaneous metastasis, like experimental metastasis, was significantly diminished in Gαq-deficient mice. Horizontal bars indicate median values; *P < .03, Mann-Whitney U test. No genotype-dependent difference was observed in overall primary tumor architecture based on histologic analyses of subcutaneous LLCGFP tumors from control (representative data in panel C) and Gαq–/– (representative data in panel D) mice. Note that tumor cell invasion into overlying dermal structures (arrowheads) and numerous blood vessels (arrows) were observed in tumors harvested from mice of both genotypes. The horizontal bars denote 100 μm. Photomicrographs were obtained using a Zeiss Axioplan 2 microscope equipped with a 20×/0.75 objective lens and an Axiovision digital camera (Zeiss, Oberkochen, Germany). Axiovision software was used to acquire images (Zeiss).
