ACP5 and cancer: In addition, several protein kinases and phosphatases, including PKA [3,4], PKC [5,6], CKII [7], alkaline phosphatase [8], tartrate-resistant acid phosphatase (TRAP) [9] and the PTEN phosphatase [10], have been shown to accumulate in conditioned cell culture media of different cell lines [11], as well as in human plasma and/or serum samples from cancer patients [12].