Walker 256 Tumor Growth Suppression by Crotoxin Involves Formyl Peptide Receptors and Lipoxin A₄

Figure 6

Proposed scheme for CTX action on Walker 256 tumor growth suppression. Subcutaneous injection of Walker 256 carcinoma cells in the plantar region of the rat right hind paw promoted a marked infiltration of leukocytes into the deep dermis that migrated from the systemic circulation. Five days after tumor cell injection, there was a marked proliferation of tumor cells. Monocyte chemotactic factors or extracellular matrix proteins are secreted by solid tumor, which attract and activate macrophages. Animals treated with CTX showed increased plasma levels of LXA₄ and its analogue being probably released by leukocytes (mainly macrophages but also neutrophils and monocytes). The increased formation of LXA₄ and 15-epi-LXA₄ is accompanied by tumor growth reduction and a significant decrease in both number and diameter of vessels and therefore pain attenuation. CTX actions require the participation of FPRs.