Simple　Summary　Cancer　cells　generally　reprogram　their　gene　expression　profiles　to　satisfy　continuous　growth,　proliferation,　and　metastasis.　Most　eukaryotic　mRNAs　are　degraded　in　a　deadenylation-dependent　pathway,　in　which　deadenylases　are　the　key　enzymes.　We　found　that　human　Ccr4　(hCcr4a/b)　and　Caf1　(hCaf1a/b),　the　dominant　cytosolic　deadenylases,　were　dysregulated　in　several　types　of　cancers　including　stomach　adenocarcinoma.　Stably　knocking　down　hCaf1a/b　or　hCcr4a/b　blocks　cell　cycle　progression　by　enhancing　the　levels　of　cell　cycle　inhibitors　and　by　inhibiting　the　formation　of　processing　bodies,　which　are　cytosolic　foci　involved　in　mRNA　metabolism.　More　importantly,　depletion　of　hCaf1a/b　or　hCcr4a/b　dramatically　inhibits　cell　proliferation　and　tumorigenicity.　Our　results　suggest　that　perturbating　global　RNA　metabolism　may　provide　a　potential　novel　strategy　for　cancer　treatment.　Cancer　cells　generally　have　reprogrammed　gene　expression　profiles　to　meet　the　requirements　of　survival,　continuous　division,　and　metastasis.　An　interesting　question　is　whether　the　cancer　cells　will　be　affected　by　interfering　their　global　RNA　metabolism.　In　this　research,　we　found　that　human　Ccr4a/b　(hCcr4a/b)　and　Caf1a/b　(hCaf1a/b)　deadenylases,　the　catalytic　components　of　the　Ccr4-Not　complex,　were　dysregulated　in　several　types　of　cancers　including　stomach　adenocarcinoma.　The　impacts　of　the　four　deadenylases　on　cancer　cell　growth　were　studied　by　the　establishment　of　four　stable　MKN28　cell　lines　with　the　knockdown　of　hCcr4a/b　or　hCaf1a/b　or　transient　knockdown　in　several　cell　lines.　Depletion　of　hCcr4a/b　or　hCaf1a/b　significantly　inhibited　cell　proliferation　and　tumorigenicity.　Mechanistic　studies　indicated　that　the　cells　were　arrested　at　the　G2/M　phase　by　knocking　down　hCaf1a,　while　arrested　at　the　G0/G1　phase　by　depleting　hCaf1b　or　hCcr4a/b.　The　four　enzymes　did　not　affect　the　levels　of　CDKs　and　cyclins　but　modulated　the　levels　of　CDK-cyclin　inhibitors.　We　identified　that　hCcr4a/b,　but　not　hCaf1a/b,　targeted　the　p21　mRNA　in　the　MKN28　cells.　Furthermore,　depletion　of　any　one　of　the　four　deadenylases　dramatically　impaired　processing-body　formation　in　the　MKN28　and　HEK-293T　cells.　Our　results　highlight　that　perturbating　global　RNA　metabolism　may　severely　affect　cancer　cell　proliferation,　which　provides　a　potential　novel　strategy　for　cancer　treatment.