CX3CR1 is associated with recruitment to tissues or vasculature and repair of damage in response to CX3CR1/fractalkine.26 A decrease in CX3CR1 on classical monocytes suggests that the monocytes with the highest levels of CX3CR1 have emigrated from the circulation in response to the progression of prostate cancer (increased PSA). The gene discussed is KLK3; the disease is prostate cancer.