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Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction.

ABSTRACT: TriplatinNC is a highly positively charged, substitution-inert derivative of the phase II clinical anticancer drug, BBR3464. Such substitution-inert complexes form a distinct subset of polynuclear platinum complexes (PPCs) interacting with DNA and other biomolecules through noncovalent interactions. Rapid cellular entry is facilitated via interaction with cell surface glycosoaminoglycans and is a mechanism unique to PPCs. Nanoscale secondary ion mass spectrometry (nanoSIMS) showed rapid distribution within cytoplasmic and nucleolar compartments, but not the nucleus. In this article, the downstream effects of nucleolar localization are described. In human colon carcinoma cells, HCT116, the production rate of 47S rRNA precursor transcripts was dramatically reduced as an early event after drug treatment. Transcriptional inhibition of rRNA was followed by a robust G1 arrest, and activation of apoptotic proteins caspase-8, -9, and -3 and PARP-1 in a p53-independent manner. Using cell synchronization and flow cytometry, it was determined that cells treated while in G1 arrest immediately, but cells treated in S or G2 successfully complete mitosis. Twenty-four hours after treatment, the majority of cells finally arrest in G1, but nearly one-third contained highly compacted DNA; a distinct biological feature that cannot be associated with mitosis, senescence, or apoptosis. This unique effect mirrored the efficient condensation of tRNA and DNA in cell-free systems. The combination of DNA compaction and apoptosis by TriplatinNC treatment conferred striking activity in platinum-resistant and/or p53 mutant or null cell lines. Taken together, our results support that the biological activity of TriplatinNC reflects reduced metabolic deactivation (substitution-inert compound not reactive to sulfur nucleophiles), high cellular accumulation, and novel consequences of high-affinity noncovalent DNA binding, producing a new profile and a further shift in the structure-activity paradigms for antitumor complexes.

SUBMITTER: Peterson EJ

PROVIDER: S-EPMC4334294 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction.

Peterson Erica J EJ Menon Vijay R VR Gatti Laura L Kipping Ralph R Dewasinghe Dilhara D Perego Paola P Povirk Lawrence F LF Farrell Nicholas P NP

Molecular pharmaceutics 20141203 1

TriplatinNC is a highly positively charged, substitution-inert derivative of the phase II clinical anticancer drug, BBR3464. Such substitution-inert complexes form a distinct subset of polynuclear platinum complexes (PPCs) interacting with DNA and other biomolecules through noncovalent interactions. Rapid cellular entry is facilitated via interaction with cell surface glycosoaminoglycans and is a mechanism unique to PPCs. Nanoscale secondary ion mass spectrometry (nanoSIMS) showed rapid distribu ...[more]

PMID: 25407898

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Project description:BackgroundDespite the advancement in chemotherapeutic drugs for colon cancer treatment, it is still a life-threatening disease worldwide due to drug resistance. Therefore, an urgently needed to develop novel drugs for colon cancer therapies. AGA is a combination of traditional Chinese medicine Antler's extract (A), Ganoderma lucidum (G), and Antrodia camphorata (A); it contains a lot of biomolecules like polysaccharides, fatty acids, and triterpenoids that are known to exerting anti-oxidative, anti-inflammatory, anti-microbial and anti-tumor activities in oral cancer. In this study, we investigate AGA anti-proliferative, anti-metastatic and apoptotic activity to explore its anti-cancer activity against colon cancer cells and its underlying mechanism.MethodHere, in-vitro studies were performed to determine the antiproliferative activity of AGA through MTT and colony formation assays. Wound healing and transwell migration assay were used to evaluate the metastasis. Flow cytometry and protein expression were used to investigate the involved molecular mechanism by evaluating the cell cycle and apoptosis. The in-vivo anti-cancerous activity of AGA was assessed by xenograft mice model of colon cancer cells.ResultsWe found that AGA significantly inhibited the proliferative capacity and metastasis of colon cancer cells in-vitro. In addition, AGA induced cell cycle arrest in the sub-G1 phase through upregulating p21 and downregulating CDK2, CDK6 in SW620, and CDK4 in SW480 and HT29, respectively. Annexin-v assay indicated that colon cancer cells had entered early and late apoptosis after treatment with AGA. Furthermore, a mechanistic protein expressions study revealed that AGA in p53-dependent and independent regulated the apoptosis of colon cancer by downregulating the p53 protein expression in SW620 and SW480 cells but upregulating in a dose-dependent manner in HT29 cells and increasing the expression of Bax and caspase-9 to inhibit the colon cancer cells. In vivo study, we found that AGA significantly reduced the xenograft tumor growth in NOD/SCID mice with no adverse effect on the kidney and liver.ConclusionCollectively, AGA has the potential to inhibit colon cancer through inhibiting proliferation, migration, and cell cycle kinase by upregulating p21 protein expression and promoting the apoptotic protein in a p53-dependent and independent manner.

Dataset Information

Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction.

Publications

Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction.

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