Modifications of protein phosphatase 2A (PP2A) by mutations and interactions with viral proteins can cause cancer.
Protein phosphatase 2A (PP2A) is considered to be a tumour suppressor because cancers can develop or be exacerbated when the activity of this enzyme is reduced either by mutations of the subunits or by interactions with viral proteins:
Mutations of the scaffolding A subunit, which then fails to bind the B and C subunits, have been identified in a number of human cancers (breast, colon, lung and skin).
Truncation of the B subunit, which prevents it from interacting with the catalytic C subunit, has been implicated in metastasis.
Tumour-promoting viruses act by binding to the scaffolding A subunit to displace the regulatory B subunit.