Cannabinoids inhibit breast cancer metastasis to the lungs in vivo. (A) Metastatic lung nodules (pointed by arrows). (B) Percentage of animals with lung metastases. Macroscopic metastases were visible to the naked eye and microscopic lesions were detectable only by H&E staining. These latter lesions were found only in JWH-133-treated animals. (C) Gelatin zymographies of vehicle- and cannabinoid-treated tumors. Four representative tumors are shown per experimental group. PC: positive control (conditioned medium of H71080 cells stimulated with the phorbol ester PMA). Arrows point to the latent (pro-MMP) and active MMP bands according to the positive control and the expected MMP molecular weights. Non-contiguous parts of the same gel are shown. Graphs show the densitometric analysis of MMP2 and MMP9 activities. Data are expressed in arbitrary units. *, p < 0.05 vs vehicle-treated tumors; §, p = 0.068 vs vehicle-treated tumors.