title: Combined depletion of cell cycle and transcriptional cyclin-dependent kinase activities induces apoptosis in cancer cells.
abstract: Selective cyclin-dependent kinase (cdk) 2 inhibition is readily compensated. However, reduced cdk2 activity may have antiproliferative effects in concert with other family members. Here, inducible RNA interference was used to codeplete cdk2 and cdk1 from NCI-H1299 non-small cell lung cancer and U2OS osteosarcoma cells, and effects were compared with those mediated by depletion of either cdk alone. Depletion of cdk2 slowed G1 progression of NCI-H1299 cells and depletion of cdk1 slowed G2-M progression in both cell lines, with associated endoreduplication in U2OS cells. However, compared with the incomplete cell cycle blocks produced by individual depletion, combined depletion had substantial consequences, with G2-M arrest predominating in NCI-H1299 cells and apoptosis the primary outcome in U2OS cells. In U2OS cells, combined depletion affected RNA polymerase II expression and phosphorylation, causing decreased expression of the antiapoptotic proteins Mcl-1 and X-linked inhibitor of apoptosis (XIAP), effects usually mediated by inhibition of the transcriptional cdk9. These events do not occur after individual depletion of cdk2 and cdk1, suggesting that reduction of cdk2, cdk1, and RNA polymerase II activities all contribute to apoptosis in U2OS cells. The limited cell death induced by combined depletion in NCI-H1299 cells was significantly increased by codepletion of cdk9 or XIAP or by simultaneous treatment with the cdk9 inhibitor flavopiridol. These results show the potency of concomitant compromise of cell cycle and transcriptional cdk activities and may guide the selection of clinical drug candidates.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
authors.forename: Dongpo
authors.initials: D
authors.lastname: Cai
authors.forename: Vaughan M
authors.initials: VM
authors.lastname: Latham
authors.forename: Xinxin
authors.initials: X
authors.lastname: Zhang
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: Shapiro
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D001859:Bone Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics; D042863:Cyclin-Dependent Kinase 9 / Q000037:antagonists & inhibitors; D005419:Flavonoids / Q000494:pharmacology; D016193:G1 Phase / Q000502:physiology; D016195:G2 Phase / Q000502:physiology; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology* / Q000628:therapy; D012516:Osteosarcoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D010880:Piperidines / Q000494:pharmacology; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D005419:Flavonoids; D010880:Piperidines; D034741:RNA, Small Interfering; C077990:alvocidib; D016203:CDC2 Protein Kinase; C467969:CDK9 protein, human; D051357:Cyclin-Dependent Kinase 2; D042863:Cyclin-Dependent Kinase 9; D012319:RNA Polymerase II