title: p27kip1 overexpression promotes paclitaxel-induced apoptosis in pRb-defective SaOs-2 cells.
abstract: p27kip1 is a cyclin-dependent kinase (CDK) inhibitor, which controls several cellular processes in strict collaboration with pRb. We evaluated the role of p27kip1 in paclitaxel-induced apoptosis in the pRb-defective SaOs-2 cells. Following 48 h of exposure of SaOs-2 cells to 100 nM paclitaxel, we observed an increase in p27kip1 expression caused by the decrease of the ubiquitin-proteasome activity. Such increase was not observed in SaOs-2 cells treated with the caspase inhibitors Z-VAD-FMK, suggesting that p27kip1 enhancement at 48 h is strictly related to apoptosis. Finally, we demonstrated that SaOs-2 cells transiently overexpressing the p27kip1 protein are more susceptible to paclitaxel-induced apoptosis than SaOs-2 cells transiently transfected with the empty vector. Indeed, after 48 h of paclitaxel treatment, 41.8% of SaOs-2 cells transiently transfected with a pcDNA3-p27kip1 construct were Annexin V-positive compared to 30.6% of SaOs-2 cells transfected with the empty vector (P < 0.05). In conclusion, we demonstrated that transfection of the pRb-defective SaOs-2 cells with the p27kip1 gene via plasmid increases their susceptibility to paclitaxel-induced apoptosis. The promoting effect of p27kip1 overexpression on apoptosis makes p27kip1 and proteasomal inhibitors interesting tools for therapy in patients with pRb-defective cancers.
authors.affiliation: Experimental Chemotherapy Laboratory, Regina Elena Cancer Institute, Rome, Italy. gabellini@ifo.it
authors.forename: Chiara
authors.initials: C
authors.lastname: Gabellini
authors.forename: Bruna
authors.initials: B
authors.lastname: Pucci
authors.forename: Paola
authors.initials: P
authors.lastname: Valdivieso
authors.forename: Giuseppina
authors.initials: G
authors.lastname: D'Andrilli
authors.forename: Marco
authors.initials: M
authors.lastname: Tafani
authors.forename: Antonio
authors.initials: A
authors.lastname: De Luca
authors.forename: Valeria
authors.initials: V
authors.lastname: Masciullo
mesh_terms: D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology*; D016160:Retinoblastoma Protein / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D016160:Retinoblastoma Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017239:Paclitaxel