An Organometallic Protein Kinase Inhibitor Pharmacologically Activates p53 and Induces Apoptosis in Human Melanoma Cells

Smalley, Keiran S.M.; Contractor, Rooha; Haass, Nikolas K.; Kulp, Angela N.; Atilla‐Gokcumen, G. Ekin; Williams, Douglas S.; Bregman, Howard; Flaherty, Keith T.; Soengas, Marı́a S.; Meggers, Eric; Herlyn, Meenhard

doi:10.1158/0008-5472.can-06-1538

Cited by 223 publications

(178 citation statements)

References 35 publications

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“…Importantly, the sensitivity of wild-type p53-carrying melanoma cells to SPARC removal indicates that their survival is reliant on SPARC levels. Reactivation of p53-dependent cell death programs has been proposed previously for therapeutic intervention for melanomas with a wild-type p53 status (Soengas et al, 2001;Smalley et al, 2007). Our study shows the efficacy of SPARC RNA interference to activate a p53 response leading to apoptosis.…”

Section: Discussionsupporting

confidence: 59%

SPARC functions as an anti-stress factor by inactivating p53 through Akt-mediated MDM2 phosphorylation to promote melanoma cell survival

et al. 2011

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Aberrant expression of Secreted Protein Acidic and Rich in Cysteine (SPARC)/osteonectin has been associated with an invasive tumor cell phenotype and poor outcome in human melanomas. Although it is known that SPARC controls melanoma tumorigenesis, the precise role of SPARC in melanoma cell survival is still unclear. Here, we show that SPARC has a cell-autonomous survival activity, which requires Akt-dependent regulation of p53. Suppression of SPARC by RNA interference in several human melanoma cells and xenografted A375 tumors triggers apoptotic cell death through the mitochondrial intrinsic pathway and activation of caspase-3. Cell death induced by depletion of SPARC is dependent on p53 and induction of Bax, and results in the generation of ROS. Stabilization of p53 in SPARC-depleted cells is associated with a decrease in Akt-mediated activating phosphorylation of MDM2. Inhibition of Akt signaling pathway is important for the observed changes as overexpression of constitutively active Akt protects cells against apoptosis induced by SPARC depletion. Conversely, increased expression of SPARC stimulates Akt and MDM2 phosphorylation, thus facilitating p53 degradation. Finally, we show that overexpression of SPARC renders cells more resistant to the p53-mediated cytotoxic effects of the DNA-damaging drug actinomycin-D. Our study indicates that SPARC functions through activation of Akt and MDM2 to limit p53 levels and that acquired expression of SPARC during melanoma development would confer survival advantages through suppression of p53-dependent apoptotic pathways.

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Section: Discussionsupporting

confidence: 59%

SPARC functions as an anti-stress factor by inactivating p53 through Akt-mediated MDM2 phosphorylation to promote melanoma cell survival

et al. 2011

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“…We next determined whether Skp2 knockdown induced a cell cycle arrest in two mutant p53 cell lines. WM983A and SK-MEL-28 cells harbor p53 mutants, P278F and L145R, respectively (Weiss et al, 1993;Ikediobi et al, 2006;Smalley et al, 2007). siRNA-mediated knockdown of Skp2 in WM983A up-regulated p27 Kip1 levels, but it did not alter the expression of cyclin B1, CDK1, and cyclin A ( Figure 7A, left).…”

Section: Lack Of Tetraploidy After Skp2 Knockdown In Mutant P53mentioning

confidence: 98%

“…The tumor suppressor p53 is known to repress transcription of CDK1, cyclin B1, and cyclin A2, at least in part through the binding of a p53-NF-Y complex to multiple CCAAT boxes within the promoter regions of these genes (Bolognese et al, 1999;Farina et al, 1999;Manni et al, 2001). Because the p53 status is wild type in WM115 and many other melanoma cell lines (Smalley et al, 2007), we determined the requirement of p53 in G2/M arrest and repression of mitotic regulators after Skp2 knockdown. We individually or jointly depleted cells of Skp2 and p53 ( Figure 6A).…”

Section: Cell Cycle Arrest After Skp2 Depletion Is Dependent On P53mentioning

confidence: 99%

Skp2 Regulates G2/M Progression in a p53-dependent Manner

Aplin

2008

MBoC

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Targeted proteasomal degradation mediated by E3 ubiquitin ligases controls cell cycle progression, and alterations in their activities likely contribute to malignant cell proliferation. S phase kinase-associated protein 2 (Skp2) is the F-box component of an E3 ubiquitin ligase complex that targets p27 Kip1 and cyclin E1 to the proteasome. In human melanoma, Skp2 is highly expressed, regulated by mutant B-RAF, and required for cell growth. We show that Skp2 depletion in melanoma cells resulted in a tetraploid cell cycle arrest. Surprisingly, co-knockdown of p27 Kip1 or cyclin E1 failed to prevent the tetraploid arrest induced by Skp2 knockdown. Enhanced Aurora A phosphorylation and repression of G2/M regulators cyclin B1, cyclin-dependent kinase 1, and cyclin A indicated a G2/early M phase arrest in Skp2-depleted cells. Furthermore, expression of nuclear localized cyclin B1 prevented tetraploid accumulation after Skp2 knockdown. The p53 status is most frequently wild type in melanoma, and the tetraploid arrest and down-regulation of G2/M regulatory genes were strongly dependent on wild-type p53 expression. In mutant p53 melanoma lines, Skp2 depletion did not induce cell cycle arrest despite up-regulation of p27 Kip1 . These data indicate that elevated Skp2 expression may overcome p53-dependent cell cycle checkpoints in melanoma cells and highlight Skp2 actions that are independent of p27 Kip1 degradation. INTRODUCTIONUbiquitin-mediated proteolysis of cell cycle regulators is critical for tight control of normal cell proliferation. The rate-limiting step in ubiquitin-dependent degradation is substrate recognition by E3 ubiquitin ligases. Altered expression and/or activity of E3 ubiquitin ligases in cancer cells leads to deregulated proteolysis and aberrant proliferation (Guardavaccaro and Pagano, 2004;Nakayama and Nakayama, 2006). It is critical to understand how E3 ubiquitin ligases contribute to malignant cell proliferation, because they represent a potential new class of therapeutic targets (Nalepa et al., 2006).One major class of E3 ubiquitin ligases that regulates cell cycle progression contains Skp1/Cullin/F-box protein (SCF) complexes (Krek, 1998;Patton et al., 1998). Within these complexes, the cullin protein serves as a scaffold for the E2 ubiquitin-conjugating enzyme and Skp1/F-box protein complex. The F-box protein determines the substrate specificity of the SCF complex; ϳ70 exist in the human genome. The F-box protein S phase kinase-associated protein 2 (Skp2) has received attention as a putative oncogene. Its expression correlates with tumor malignancy in several tumor types, and the SKP2 gene is amplified in small cell lung and biliary tract cancers (reviewed in Guardavaccaro and Pagano, 2004). High expression of Skp2 is sufficient to promote anchorage-independent growth (Carrano et al., 1999), and Skp2 cooperates with mutant Ras to transform rat fibroblasts (Gstaiger et al., 2001). Evidence from transgenic mice models shows that expression of Skp2 in the T-lymphoid lineage cooperates with activate...

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“…This is a result of the reductive atmosphere in tumours due to fast anabolic processes [9,19]. DNA and cellular proteins like kinases or other enzymes were suggested as intracellular targets [20,21].…”

Section: [Tetrachlorido(1h-imidazole)(dimethylsulfoxide-κs)ruthenate(mentioning

confidence: 99%

Solution equilibrium studies of anticancer ruthenium(II)-η6-p-cymene complexes of pyridinecarboxylic acids

et al. 2014

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Stoichiometry and stability of antitumor ruthenium(II)-η 6 -p-cymene complexes of picolinic acid and its 6-methyl and 6-carboxylic acid derivatives were determined by pHpotentiometry, 1 H NMR spectroscopy and UV/Vis spectrophotometry in aqueous solution in the presence or absence of coordinating chloride ions. The picolinates form exclusively monoligand complexes in which they can coordinate via the bidentate (O,N) mode and a chloride or a water molecule is found at the third binding site of the ruthenium(II)-η 6 -p-cymene moiety depending on the conditions. [Ru(η 6 -p-cymene)(L)(H 2 O/Cl)] species are predominant at physiological pH in all studied cases. Hydrolysis of the aqua complex or the chlorido/hydroxido co-ligand exchange results in the formation of the mixed-hydroxido species [Ru(η 6 -p-cymene)(L)(OH)] in the basic pH range. There is no indication for the decomposition of the mono-ligand complexes during 24 h in the ruthenium(II)-η 6 -pcymene−picolinic acid system between pH 3 and 11; however, a slight dissociation with a low reaction rate was found in the other two systems leading to the appearance of the dinuclear trihydroxido-bridged species [Ru 2 (η 6 -p-cymene) 2 (OH) 3 ] + and free ligands at pH > 10. The replacement of the chlorido by an aqua ligand in [Ru(η 6 -p-cymene)(L)Cl] was also monitored and equilibrium constants for the exchange process were determined.

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An Organometallic Protein Kinase Inhibitor Pharmacologically Activates p53 and Induces Apoptosis in Human Melanoma Cells

Cited by 223 publications

References 35 publications

SPARC functions as an anti-stress factor by inactivating p53 through Akt-mediated MDM2 phosphorylation to promote melanoma cell survival

SPARC functions as an anti-stress factor by inactivating p53 through Akt-mediated MDM2 phosphorylation to promote melanoma cell survival

Skp2 Regulates G2/M Progression in a p53-dependent Manner

Solution equilibrium studies of anticancer ruthenium(II)-η6-p-cymene complexes of pyridinecarboxylic acids

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