title: Down-regulation of SKP2 induces apoptosis in lung-cancer cells.
abstract: S-Phase kinase associated protein 2 (SKP2), an F-box protein constituting the substrate-recognition subunit of the SCF(SKP2) ubiquitin ligase complex, targets cell-cycle regulators, such as the cyclin-dependent kinase inhibitor p27(KIP1), for ubiquitin-mediated degradation. Our earlier studies indicated frequent amplification and over-expression of the SKP2 gene in primary small-cell lung cancers (SCLCs) and cell lines derived from this type of tumor, and showed that down-regulation of SKP2 expression by means of an antisense oligonucleotide inhibited the growth of SCLC cells in culture (Yokoi et al., Am J Pathol, 161, 207-216, 2002). The antisense effect was confirmed in two cell lines of non-small cell lung cancer (NSCLC) that also exhibited over-expression of the gene. In the work reported here, we examined the mechanism(s) responsible for antisense-mediated growth inhibition of SCLC- and NSCLC-derived cultures. SKP2-antisense treatment not only suppressed DNA synthesis, as determined by [(3)H]thymidine incorporation, but also induced spontaneous apoptosis characterized by an increase in the sub-G1 population, fragmentation of nuclei, and activation of caspase-3. Our results suggest that since down-regulation of SKP2 appears to induce apoptosis in lung-cancer cells directly, targeting this molecule could represent a promising new therapeutic approach for this type of cancer, and possibly other tumors that over-express SKP2.
authors.affiliation: Department of Molecular Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan.
authors.forename: Sana
authors.initials: S
authors.lastname: Yokoi
authors.forename: Kohichiroh
authors.initials: K
authors.lastname: Yasui
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iizasa
authors.forename: Takashi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Takehiko
authors.initials: T
authors.lastname: Fujisawa
authors.forename: Johji
authors.initials: J
authors.lastname: Inazawa
mesh_terms: D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000235:genetics / Q000473:pathology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D004789:Enzyme Activation; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology*; D020320:Oligoribonucleotides, Antisense / Q000494:pharmacology; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D020320:Oligoribonucleotides, Antisense; D044786:S-Phase Kinase-Associated Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D013936:Thymidine