Platinum Complexes Can Bind to Telomeres by Coordination.

It is suggested that several compounds, including G-quadruplex ligands, can target telomeres, inducing their uncapping and, ultimately, cell death. However, it has never been demonstrated whether such ligands can bind directly and quantitatively to telomeres. Here, we employed the property of platinum and platinum-G-quadruplex complexes to target G-rich sequences to investigate and quantify their covalent binding to telomeres. Using inductively coupled plasma mass spectrometry, surprisingly, we found that, in cellulo, in the presence of cisplatin, a di-functional platinum complex, telomeric DNA was platinated 13-times less than genomic DNA in cellulo, as compared to in vitro data. On the contrary, the amount of mono-functional platinum complexes (Pt-ttpy and Pt-tpy) bound either to telomeric or to genomic DNA was similar and occurred in a G-quadruplex independent-manner. Importantly, the quantification revealed that the low level of cisplatin bound to telomeric DNA could not be the direct physical cause of TRF2 displacement from telomeres. Altogether, our data suggest that platinum complexes can affect telomeres both directly and indirectly.

The Opportunity of Precision Medicine for Breast Cancer With Context-Sensitive Tumor Suppressor Maspin.

To improve the precision of molecular diagnosis and to develop and guide targeted therapies of breast cancer, it is essential to determine the mechanisms that underlie the specific tumor phenotypes. To this end, the application of a snapshot of gene expression profile for breast cancer diagnosis and prognosis is fundamentally challenged since the tissue-based data are derived from heterogonous cell types and are not likely to reflect the dynamics of context-dependent tumor progression and drug sensitivity. The intricate network of epithelial differentiation program can be concertedly controlled by tumor suppressor maspin, a homologue of clade B serine protease inhibitors (serpin), through its multifaceted molecular interactions in multiple subcellular localizations. Unlike most other serpins that are expressed in multiple cell types, maspin is epithelial specific and has distinct roles in luminal and myoepithelial cells. Endogenously expressed maspin has been found in the nucleus and cytoplasm, and detected on the surface of cell membrane. It is also secreted free and as an exosomal cargo protein. Research in the field has led to the identification of the maspin targets and maspin-associated molecules, as well as the structural determinants of its suppressive functions. The current review discusses the possibility for maspin to serve as a cell type-specific and context-sensitive marker to improve the precision of breast cancer diagnosis and prognosis. These advancements further suggest a new window of opportunity for designing novel maspin-based chemotherapeutic agents with improved anti-cancer potency. J. Cell. Biochem. 118: 1639-1647, 2017. © 2017 Wiley Periodicals, Inc.

Pt-ttpy, a G-quadruplex binding platinum complex, induces telomere dysfunction and G-rich regions DNA damage.

Pt-ttpy (tolyl terpyridin-Pt complex) covalently binds to G-quadruplex (G4) structures in vitro and to telomeres in cellulo via its Pt moiety. Here, we identified its targets in the human genome, in comparison to Pt-tpy, its derivative without G4 affinity, and cisplatin. Pt-ttpy, but not Pt-tpy, induces the release of the shelterin protein TRF2 from telomeres concomitantly to the formation of DNA damage foci at telomeres but also at other chromosomal locations. γ-H2AX chromatin immunoprecipitation (ChIP-seq) after treatment with Pt-ttpy or cisplatin revealed accumulation in G- and A-rich tandemly repeated sequences, but not particularly in potential G4 forming sequences. Collectively, Pt-ttpy presents dual targeting efficiency on DNA, by inducing telomere dysfunction and genomic DNA damage at specific loci.

Antitumor trans-N-heterocyclic carbene-amine-Pt(II) complexes: synthesis of dinuclear species and exploratory investigations of DNA binding and cytotoxicity mechanisms.

A series of bimetallic [(NHC)PtX2]2(diamine) complexes have been prepared as a new chemotype for potential anticancer agents. These complexes display an uncommon set of structural features as far as they combine two bifunctional, trans-configured platinum centers. They display cytotoxic activities in the micromolar range on many cancerous cell lines and do not cross-react with cisplatin in A2780/DDP cell lines. They bind slowly to double-stranded DNAs, giving monoadducts as the major products. Pathways for cellular toxicity have been investigated for both mono- and bimetallic trans-(NHC)PtX2(amine) complexes. It has been highlighted that, unlike cisplatin, these complexes do not induce cell cycle arrest. They trigger apoptosis in A2780 cells by a pathway involving translocation of apoptosis-inducing factor and caspase 12 to the nucleus. Moreover, bimetallic complexes may induce necrosis.