Because protein phosphorylation is a dynamic process whereby phosphatases counterbalance kinase action, phosphatases may be used to inhibit NF-κB activation. Protein phosphatase 2A is a serine/threonine phosphatase that has been reported to dephosphorylate and modulate the activity of IKKβ [75]. Cytosine arabinoside, a pyrimidine analogue used to effectively treat acute leukemia, has been reported to induce apoptosis by activating protein phosphatases 2A and 2B-A and dephosphorylating the p65 subunit of NF-κB [22, 76]. Recently, OspF, a protein phosphatase from Shigella flexneri, was found to dephosphorylate MAPK and prevent histone H3 phosphorylation at Ser10 in a gene-specific manner to block the activation of a subset of NF-κB responsive genes [77]. Our previous studies have shown that protein tyrosine phosphatase (PTP) inhibitors can suppress NF-κB activation and that phenylarsine oxide, a specific PTP inhibitor, can promote tyrosine 42 phosphorylation of IκBα [78]. While some PTPs stimulate NF-κB activation, other PTPs negatively regulate NF-κB activation. For instance, PTEN, a tumor suppressor with phosphatase activity is known to inhibit NF-κB activation [79]. Recently, Chew et al., [80] found that WIP1, a Ser/Thr PP2C family
