The chemokine network in cancer--much more than directing cell movement.

Cytokine and chemokine gradients are central to the directed movement of cells in both homeostatic and pathological processes. Most cancers have a complex chemokine network which can influence immune responses to the tumor, direct the extent and cellular composition of the leukocyte infiltrate and also play a role in angiogenesis. Tumor cells can also hijack the chemokine system and gain expression of certain chemokine receptors and respond to specific chemokine gradients. Chemokine receptor expression and activation on malignant cells may be central to the growth, survival and migration of cancer cells from the primary tumor. Chemokine receptors, both CC and CXC have been detected on malignant cells and the relevant ligands are sometimes expressed at the tumor site and at sites of tumor spread, suggesting a role for the chemokine family in malignant growth and metastasis.