Pt-DNA Adducts Research Articles

Interactions with DNA Models of the Oxaliplatin Analog (cis-1,3-DACH)PtCl2.

It is generally accepted that adjacent guanine residues in DNA are the primary target for platinum antitumor drugs and that differences in the conformations of the Pt-DNA adducts can play a role in their antitumor activity. In this study, we investigated the effect of the carrier ligand cis-1,3-diaminocyclohexane (cis-1,3-DACH) upon formation, stability, and stereochemistry of the (cis-1,3-DACH)PtG2 and (cis-1,3-DACH)Pt(d(GpG)) adducts (G = 9-EthlyGuanine, guanosine, 5'- and 3'-guanosine monophosphate; d(GpG) = deoxyguanosil(3'-5')deoxyguanosine). A peculiar feature of the cis-1,3-DACH carrier ligand is the steric bulk of the diamine, which is asymmetric with respect to the Pt-coordination plane. The (cis-1,3-DACH)Pt(5'GMP)2 and (cis-1,3-DACH)Pt(3'GMP)2 adducts show preference for the ΛHT and ∆HT conformations, respectively (HT stands for Head-to-Tail). Moreover, the increased intensity of the circular dichroism signals in the cis-1,3-DACH derivatives with respect to the analogous cis-(NH3)2 species could be a consequence of the greater bite angle of the cis-1,3-DACH carrier ligand with respect to cis-(NH3)2. Finally, the (cis-1,3-DACH)Pt(d(GpG)) adduct is present in two isomeric forms, each one giving a pair of H8 resonances linked by a NOE cross peak. The two isomers were formed in comparable amounts and had a dominance of the HH conformer but with some contribution of the ΔHT conformer which is related to the HH conformer by having the 3'-G base flipped with respect to the 5'-G residue.

NIR-Light-Triggered Mild-Temperature Hyperthermia to Overcome the Cascade Cisplatin Resistance for Improved Resistant Tumor Therapy.

Currently, cisplatin resistance has been recognized as a multistep cascade process for its clinical chemotherapy failure. Hitherto, it remains challenging to develop a feasible and promising strategy to overcome the cascade drug resistance (CDR) issue for achieving fundamentally improved chemotherapeutic efficacy. Herein, a novel self-assembled nanoagent is proposed, which is constructed by Pt(IV) prodrug, cyanine dye (cypate), and gadolinium ion (Gd3+), for systematically conquering the cisplatin resistance by employing near-infrared (NIR) light activated mild-temperature hyperthermia in tumor targets. The proposed nanoagents exhibit high photostability, GSH/H+-responsive dissociation, preferable photothermal conversion, and enhanced cellular uptake performance. In particular, upon 785-nm NIR light irradiation, the generated mild temperature of ≈ 43 °C overtly improves the cell membrane permeability and drug uptake, accelerates the disruption of intracellular redox balance, and apparently enhances the formation of Pt-DNA adducts, thereby effectively overcoming the CDR issue and achieves highly improved therapeutic efficacy for cisplatin-resistant tumor ablation.

Nuclear-Targeting Lipid PtIV Prodrug Amphiphile Cooperates with siRNA for Enhanced Cancer Immunochemotherapy by Amplifying Pt-DNA Adducts and Reducing Phosphatidylserine Exposure.

Patients treated with Pt-based anticancer drugs (PtII) often experience severe side effects and are susceptible to cancer recurrence due to the limited bioavailability of PtII and tumor-induced immunosuppression. The exposure of phosphatidylserine on the cell's outer surface induced by PtII results in profound immunosuppression through the binding of phosphatidylserine to its receptors on immune cells. Here, we report a novel approach for enhanced cancer chemoimmunotherapy, where a novel nuclear-targeting lipid PtIV prodrug amphiphile was used to deliver a small interfering RNA (siXkr8) to simultaneously amplify Pt-DNA adducts and reduce the level of exposure of phosphatidylserine. This drug delivery vehicle is engineered by integrating the PtIV prodrug with self-assembly performance and siXkr8 into a lipid nanoparticle, which shows tumor accumulation, cancer cell nucleus targeting, and activatable in a reduced microenvironment. It is demonstrated that nuclear-targeting lipid PtIV prodrug increases the DNA cross-linking, resulting in increased Pt-DNA adduct formation. The synergistic effects of the PtIV prodrug and siXkr8 contribute to the improvement of the tumor immune microenvironment. Consequently, the increased Pt-DNA adducts and immunogenicity effectively inhibit primary tumor growth and prevent tumor recurrence. These results underscore the potential of utilizing the nuclear-targeting lipid PtIV prodrug amphiphile to enhance Pt-DNA adduct formation and employing siXkr8 to alleviate immunosuppression during chemotherapy.

Effective monitoring of Platinum-DNA adducts formation under simulated physiological conditions by CE-ICP-MS/MS

The leading Pt(II)-based anticancer drugs have been used for decades; however, chemotherapy with their application is burdened with severe side effects. The administration of compounds capable of DNA platination in the form of prodrugs has the potential to overcome the drawbacks associated with their use. Progress toward their clinical application depends on establishing proper methodologies that would allow assessing their ability to bind to DNA in the biological environment. Herein, we propose implementing the approach based on the hyphenation of capillary electrophoresis with inductively coupled plasma tandem mass spectrometry (CE-ICP-MS/MS) for studying Pt-DNA adduct formation. The presented methodology opens the possibility to employ the multielement monitoring for studying the differences in the behavior of Pt(II) and Pt(IV) complexes and, interestingly, revealed the formation of various adducts with DNA and cytosol components for the latter one.

A nuclease-mimetic platinum nanozyme induces concurrent DNA platination and oxidative cleavage to overcome cancer drug resistance

Platinum (Pt) resistance in cancer almost inevitably occurs during clinical Pt-based chemotherapy. The spontaneous nucleotide-excision repair of cancer cells is a representative process that leads to Pt resistance, which involves the local DNA bending to facilitate the recruitment of nucleotide-excision repair proteins and subsequent elimination of Pt-DNA adducts. By exploiting the structural vulnerability of this process, we herein report a nuclease-mimetic Pt nanozyme that can target cancer cell nuclei and induce concurrent DNA platination and oxidative cleavage to overcome Pt drug resistance. We show that the Pt nanozyme, unlike cisplatin and conventional Pt nanoparticles, specifically induces the nanozyme-catalyzed cleavage of the formed Pt-DNA adducts by generating in situ reactive oxygen species, which impairs the damage recognition factors-induced DNA bending prerequisite for nucleotide-excision repair. The recruitment of downstream effectors of nucleotide-excision repair to DNA lesion sites, including xeroderma pigmentosum groups A and F, is disrupted by the Pt nanozyme in cisplatin-resistant cancer cells, allowing excessive accumulation of the Pt-DNA adducts for highly efficient cancer therapy. Our study highlights the potential benefits of applying enzymatic activities to the use of the Pt nanomedicines, providing a paradigm shift in DNA damaging chemotherapy.

Low-Intensity Light-Responsive Anticancer Activity of Platinum(II) Complex Nanocolloids on 2D and 3D In Vitro Cancer Cell Model.

This study aimed to evaluate the therapeutic efficacy of low-intensity visible light responsive nanocolloids of a Pt-based drug using a 2D and three-dimensional (3D) in vitro cancer cell model. Biocompatible and biodegradable polymeric nanocolloids, obtained using the ultrasonication method coupled with Layer by Layer technology, were characterized in terms of size (100 ± 20 nm), physical stability, drug loading (78%), and photoactivation through spectroscopy studies. The in vitro biological effects were assessed in terms of efficacy, apoptosis induction, and DNA-Pt adducts formation. Biological experiments were performed both in dark and under visible light irradiation conditions, exploiting the complex photochemical properties. The light-stimuli responsive nanoformulation gave a significant enhancement in drug bioactivity. This allowed us to achieve satisfying results by using nanomolar drug concentration (50 nM), which was ineffective in darkness condition. Furthermore, our nanocolloids were validated in 3D in vitro spheroids using confocal microscopy and cytofluorimetric assay to compare their behavior on culture in 2D monolayers. The obtained results confirmed that these nanocolloids are promising tools for delivering Pt-based drugs.

Cellular Toxicity Mechanisms and the Role of Autophagy in Pt(IV) Prodrug-Loaded Ultrasmall Iron Oxide Nanoparticles Used for Enhanced Drug Delivery.

Ultrasmall iron oxide nanoparticles (<10 nm) were loaded with cis-diamminetetrachloroplatinum (IV), a cisplatin (II) prodrug, and used as an efficient nanodelivery system in cell models. To gain further insight into their behavior in ovarian cancer cells, the level of cellular incorporation as well as the platination of mitochondrial and nuclear DNA were measured using inductively coupled plasma mass spectrometry (ICP-MS) strategies. Quantitative Pt results revealed that after 24 h exposure to 20 µM Pt in the form of the Pt(IV)-loaded nanoparticles, approximately 10% of the incorporated Pt was associated with nuclear DNA. This concentration increased up to 60% when cells were left to stand in drug-free media for 3 h. These results indicated that the intracellular reducing conditions permitted the slow release of cisplatin (II) from the cisplatin (IV)-loaded nanoparticles. Similar results were obtained for the platination of mitochondrial DNA, which reached levels up to 17,400 ± 75 ng Pt/ mg DNA when cells were left in drug-free media for 3 h, proving that this organelle was also a target for the action of the released cisplatin (II). The time-dependent formation of Pt-DNA adducts could be correlated with the time-dependent decrease in cell viability. Such a decrease in cell viability was correlated with the induction of apoptosis as the main route of cell death. The formation of autophagosomes, although observed upon exposure in treated cells, does not seem to have played an important role as a means for cells to overcome nanoparticles’ toxicity. Thus, the designed nanosystem demonstrated high cellular penetration and the “in situ” production of the intracellularly active cisplatin (II), which is able to induce cell death, in a sustained manner.

Decomposable black phosphorus nano-assembly for controlled delivery of cisplatin and inhibition of breast cancer metastasis

Novel platforms for cisplatin delivery with a controllable manner and combinable with other treatment modality to achieve synergistic antitumor effect and inhibition metastasis for treatment of triple negative breast cancer (TNBC) are highly desirable. Herein, we report a black phosphorus (BP) nanosheets-based nano-assembly which consists of cisplatin, BP, polydopamine (PDA) and hyaluronic acid (HA), cisplatin/BP/PDA-HA (CBPH), for controlled delivery of cisplatin and inhibition tumor growth as well as lung metastasis of TNBC. For constructing CBPH, the surface of BP was dual modified by PDA and HA, resulting in enhanced stability, tumor target ability and photothermal efficiency of BP. Cisplatin was released in response both to internal and external stimuli existed in tumor microenvironment, including low pH, hydrogen peroxide and NIR light, as accompanied by decomposition of BP. In vitro experiments demonstrated CBPH-treated 4 T1 cells showed elevated intracellular content of Pt and Pt-DNA adduct, which was further improved when exposure to NIR light, leading to potent antitumor effect in a synergistic pattern. Anti-metastasis studies in 2D monolayers and 3D organoids revealed that CBPH plus NIR light treatment exhibited significantly decreased migration, invasion and regrowth ability of 4 T1 cells. Furthermore, TNBC-bearing mice with systemic administrate of CBPH showed enhanced tumor accumulation of cisplatin and light-triggered inhibition of tumor growth at primary site and lung metastasis, with alleviated toxicity. But CBPH is yet to be optimized for realizing smart cisplatin delivery in response to acidic and redox stimuli in vivo. Collectively, our study demonstrates that this novel BP-based nano-assembly with controllable tumor delivery of cisplatin and metastasis inhibition of breast cancer expand the use of BP in biomedicine field and hold great promise for further development.

A Systematic Strategy of Combinational Blow for Overcoming Cascade Drug Resistance via NIR-Light-Triggered Hyperthermia.

A systematic combination strategy is proposed for overcoming cisplatin resistance using near-infrared (NIR)-light-triggered hyperthermia. A new photothermal polymer DAP-F is complexed with a reduction-sensitive amphiphilic polymer P1 to form F-NPs with photothermal effect. Subsequently, to build the final nanosystem F-Pt-NPs, F-NPs are combined with Pt-NPs, which are obtained by encapsulating a Pt(IV) prodrug with P1. Mild hyperthermia (43 °C), generated from F-Pt-NPs induced by an 808 nm NIR laser, have various effects such as: i) enhancing the cellular membrane permeability to promote the uptake of drugs; ii) activating cisplatin by accelerating the glutathione consumption; iii) increasing the Pt-DNA adducts formation and possibly the formation of a portion of irreparable Pt-DNA interstrand crosslinks, thereby inhibiting the repair of DNA. In vitro, it is found that even on cisplatin-resistant A549DDP cells, the IC50 of F-Pt-NPs (43 °C) is only 7.0 × 10-6 m Pt mL-1 . In vivo, on a patient-derived xenograft model of multidrug resistant lung cancer, the efficacy of the F-Pt-NPs (43 °C) treatment group shows a tumor inhibition rate of 94%. Taken together, here, an important perspective of resolving cascade drug resistance with the assistance of mild hyperthermia triggered by NIR light is presented, which can be of great significance for clinic translation.

RUNX3 Transcript Variants Have Distinct Roles in Ovarian Carcinoma and Differently Influence Platinum Sensitivity and Angiogenesis.

Simple SummaryEpithelial ovarian cancer treatment is limited by missing predictive markers, frequent chemotherapy resistance and an incomplete understanding of the biology of tumors. Earlier work proved that hypermethylation of the gene RUNX3 coding for a transcription factor has prognostic value, and RUNX3 transcript variant overexpression, regulated by this epigenetic mechanism, influences cisplatin sensitivity and malignant properties of cells contrary. The present data validate RUNX3 transcript variant-specific effects for high-grade serous ovarian cancer and identify RUNX3-regulated genes and processes. Specifically, DNA damage repair and angiogenesis are influenced by RUNX3, and transcript variant 1 mediates stronger carcinogenic properties.The prognosis of late-stage epithelial ovarian cancer (EOC) patients is affected by chemotherapy response and the malignant potential of the tumor cells. In earlier work, we identified hypermethylation of the runt-related transcription factor 3 gene (RUNX3) as a prognostic biomarker and contrary functions of transcript variants (TV1 and TV2) in A2780 and SKOV3 cells. The aim of the study was to further validate these results and to increase the knowledge about RUNX3 function in EOC. New RUNX3 overexpression models of high-grade serous ovarian cancer (HGSOC) were established and analyzed for phenotypic (IC50 determination, migration, proliferation and angiogenesis assay, DNA damage analysis) and transcriptomic consequences (NGS) of RUNX3 TV1 and TV2 overexpression. Platinum sensitivity was affected by a specific transcript variant depending on BRCA background. RUNX3 TV2 induced an increased sensitivity in BRCA1wt cells (OVCAR3), whereas TV1 increased the sensitivity and induced a G2/M arrest under treatment in BRCA1mut cells (A13-2-12). These different phenotypes relate to differences in DNA repair: homologous recombination deficient A13-2-12 cells show less γH2AX foci despite higher levels of Pt-DNA adducts. RNA-Seq analyses prove transcript variant and cell-line-specific RUNX3 effects. Pathway analyses revealed another clinically important function of RUNX3—regulation of angiogenesis. This was confirmed by thrombospondin1 analyses, HUVEC spheroid sprouting assays and proteomic profiling. Importantly, conditioned media (CM) from RUNX3 TV1 overexpressing A13-2-12 cells induced an increased HUVEC sprouting. Altogether, the presented data support the hypothesis of different functions of RUNX3 transcript variants related to the clinically relevant processes—platinum resistance and angiogenesis.

Abstract 1385: In vitro evaluation of platinum chemotherapy combinations with the ATR inhibitor, ceralasertib (AZD6738)

Abstract Introduction: The combination of platinum-based chemotherapy with inhibitors of the DNA damage response (DDR) is therapeutically challenging due to overlapping toxicities, such as myelosuppression. The optimal sequence and schedule of drug delivery to mitigate toxicity and maximise efficacy has not been determined for many combinations. Ceralasertib is an oral inhibitor of ATR, a key constituent of the DDR. Ceralasertib has entered early phase clinical trials in combination with carboplatin (NCT02264678). The aim of the current study was to investigate the mechanism of interaction of ceralasertib with platinum (Pt) chemotherapy, characterising the formation and removal of Pt-induced DNA adducts, in order to provide insight into the repair and recovery of DNA following combination treatment. Methods: The growth inhibitory effects of ceralasertib alone and in combination with cisplatin were tested using sulphorhodamine B (SRB) colorimetric assays in a panel of non-small cell lung (H460 and H23) and breast (MCF7, T47D, HCC1806, MDA-MB-436 and MDA-MB-468) cancer cell lines. Median effect analysis using CalcuSyn software (Biosoft, Cambridge, UK) was used to evaluate synergistic combinations. Time- and schedule-dependent analyses of Pt-DNA adduct formation in cells treated with the combination were carried out using inductively-coupled mass spectrometry (ICP-MS). Cell cycle analysis and DNA replication combing assays were performed to explore alternative mechanisms of synergy between ceralasertib and cisplatin. Results: Ceralasertib was synergistic with cisplatin, inhibiting growth across the cell line panel. However, neither pre-exposure with either agent or co-exposure of cisplatin treated cells to ceralasertib affected the total number, nor longevity, of Pt-DNA adducts compared with cisplatin treatment alone. Continued exposure to ceralasertib for up to 48 hours following wash out of cisplatin (after 4, 8 or 24 hours treatment) did not maintain Pt-induced adducts within the DNA. Peak Pt-DNA adduct formation did not consistently correlate with cell line sensitivity to either drug, combination synergy score, or the effects of ceralasertib or cisplatin on cell cycle progression. Combination treatment did result in a reduction in replication fork speed, but this effect was no greater than that seen with ceralasertib monotherapy. Conclusion: Synergy was observed between cisplatin and ceralasertib in the cell lines tested. However, our in vitro data suggests that this is not associated with an interaction at the level of Pt-DNA adduct formation. Citation Format: Sally E. Hall, Alan Lau, Emma Dean, Elizabeth Martin, Christopher Ottley, Yvette Drew, Gareth Veal. In vitro evaluation of platinum chemotherapy combinations with the ATR inhibitor, ceralasertib (AZD6738) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1385.

Gas-blasting nanocapsules to accelerate carboplatin lysosome release and nucleus delivery for prostate cancer treatment

To improve therapeutic effect and reduce severely side effects of carboplatin (CBP), the gas-generating nanocapsules were developed to accelerate CBP lysosome release and nucleus delivery. CBP/SB-NC was prepared by co-loading CBP and NaHCO3 (SB) in nanocapsules using w/o/w emulsification solvent evaporation. They exhibited vesicle-like spherical morphology, uniform particle size and negative zeta potential. Reaching the tumor site with a relatively high concentration is the first step for CBP delivery and the results showed that CBP/SB-NC could effectively increase drug accumulation at tumor site. After that, the drug delivery carriers need to be internalized into tumor cells and the in vitro cellular uptake ability results showed CBP/SB-NC could be internalized into RM-1 cells more efficient than CBP solution. After internalized by RM-1 cells, the gas-blasting release process was tested in acid environment. It was demonstrated that 5 mg/ml NaHCO3 was optimal to achieve pH-responsive gas-blasting release. In vitro release results showed that CBP significantly rapid release in acid environment (pH 5.0) compared to neutral pH (pH 7.4) (P < 0.05). Meanwhile, TEM and the change of the concentration of H+ results exhibited that the explosion of CBP/SB5-NC was more easily happened in lysosome acid environment (pH 5.0). The blasting release can accelerate CBP lysosome release to cytoplasm. Furthermore, the nucleus delivery results showed CBP/SB5-NC can promote pH-triggered rapid nucleus delivery. And the results of Pt-DNA adduct assay showed that the binding efficiency between CBP and DNA of CBP/SB5-NC was higher than CBP solution. At last, in vitro and in vivo anti-tumor efficacy proved that CBP/SB5-NC could enhance anti-tumor activity for prostate cancer therapy. CBP/SB5-NC also showed superior safety in vitro and in vivo by hemolysis assay and histopathological study. All of the results demonstrate that CBP/SB5-NC would be an efficient gas-blasting release formulation to enhance prostate cancer treatment.

Biological properties of a benzothiazole-based mononuclear platinum(II) complex as a potential anticancer agent

A mononuclear platinum(II) complex, [PtLCl]Cl (1, where L = N-(4-(benzo[d]thiazol-2-yl)phenyl)-2-(bis(pyridine-2-ylmethyl)-amino)acetamide), was synthesized by covalently tethering a benzothiazole derivative 2-(4-aminophenyl)benzothiazole to the 2,2′-dipicolylamine (DPA) chelating PtII center by an amidic bond. 1 showed a cytotoxicity comparable to that of cisplatin against MCF-7 cell lines and more potent activities against HeLa and A-549 cell lines. Investigation of the reaction of 1 with 5′-GMP displayed 1 could coordinate with N7-GMP to form the Pt-GMP adduct. Thus 1 has potential to form Pt-DNA adducts in vivo. Similarly, the glutathione (GSH) ligand could also coordinate to the PtII center to form a monodentate Pt-GS complex. The competition experiments of 1 with 5′-GMP and GSH showed that the coordination binding of 1 with GSH did not prevent formation of a certain amount of the Pt-GMP adduct in the reaction process. DNA binding experiments displayed that 1 could bind to DNA through multiple binding modes involving non-covalent interaction and monofunctional platination of the platinum(II) moiety, and induce a visible conformational change of DNA. The evaluation of the protein binding ability showed that 1 could bind to human serum albumin (HSA) with a moderate binding affinity, quench the intrinsic fluorescence of HSA, and destroy the tertiary structure of HSA.

Targeting of radioactive platinum-bisphosphonate anticancer drugs to bone of high metabolic activity

Platinum-based chemotherapeutics exhibit excellent antitumor properties. However, these drugs cause severe side effects including toxicity, drug resistance, and lack of tumor selectivity. Tumor-targeted drug delivery has demonstrated great potential to overcome these drawbacks. Herein, we aimed to design radioactive bisphosphonate-functionalized platinum (195mPt-BP) complexes to confirm preferential accumulation of these Pt-based drugs in metabolically active bone. In vitro NMR studies revealed that release of Pt from Pt BP complexes increased with decreasing pH. Upon systemic administration to mice, Pt-BP exhibited a 4.5-fold higher affinity to bone compared to platinum complexes lacking the bone-seeking bisphosphonate moiety. These Pt-BP complexes formed less Pt-DNA adducts compared to bisphosphonate-free platinum complexes, indicating that in vivo release of Pt from Pt-BP complexes proceeded relatively slow. Subsequently, radioactive 195mPt-BP complexes were synthesized using 195mPt(NO3)2(en) as precursor and injected intravenously into mice. Specific accumulation of 195mPt-BP was observed at skeletal sites with high metabolic activity using micro-SPECT/CT imaging. Furthermore, laser ablation-ICP-MS imaging of proximal tibia sections confirmed that 195mPt BP co-localized with calcium in the trabeculae of mice tibia.

New minor groove covering DNA binding mode of dinuclear Pt(II) complexes with various pyridine-linked bridging ligands and dual anticancer-antiangiogenic activities.

New anticancer platinum(II) compounds simultaneously targeting tumor cells and tumor-derived neoangiogenesis, with new DNA interacting mode and large therapeutic window are appealing alternative to improve efficacy of clinical platinum chemotherapeutics. Herein, we describe three novel dinuclear [{Pt(en)Cl}2(μ-L)]2+ complexes with different pyridine-like bridging ligands (L), 4,4'-bipyridine (Pt1), 1,2-bis(4-pyridyl)ethane (Pt2) and 1,2-bis(4-pyridyl)ethene (Pt3), which highly, positively charged aqua derivatives, [{Pt(en)(H2O)}2(μ-L)]4+, interact with the phosphate backbone forming DNA-Pt adducts with an unique and previously undescribed binding mode, called a minor groove covering. The results of this study suggested that the new binding mode of the aqua-Pt(II) complexes with DNA could be attributed to the higher anticancer activities of their chloride analogues. All three compounds, particularly complex [{Pt(en)Cl}2(μ-4,4'-bipy)]Cl2·2H2O (4,4'-bipy is 4,4'-bipyridine) (Pt1), overcame cisplatin resistance in vivo in the zebrafish-mouse melanoma xenograft model, showed much higher therapeutic potential than antiangiogenic drug sunitinib malate, while effectively blocking tumor neovascularization and melanoma cell metastasis. Overall therapeutic profile showed new dinuclear Pt(II) complexes could be novel, effective and safe anticancer agents. Finally, the correlation with the structural characteristics of these complexes can serve as a useful tool for developing new and more effective anticancer drugs.

Oxygen-enriched Fe3O4/Gd2O3 nanopeanuts for tumor-targeting MRI and ROS-triggered dual-modal cancer therapy through platinum (IV) prodrugs delivery

In this study, we designed a novel peanut probe that could load oxygen molecules and platinum(IV) prodrug (GINP-Pt) to elicit ferroptosis and apoptosis in cancer cells. In addition, transferrin-labeled amino polyethylene glycol (Tf-PEG-NH2) was equipped to GINP-Pt to obtain targeting and pH-responsive ability. When the system enters cancer cells, platinum(IV) can be released and reduced to platinum(II) by depleting glutathione (GSH), resulting in a ROS increase. Meanwhile, Tf-PGINP-Pt deliver abundant oxgen molecules into cancer cells, significantly elevating oxygen levels. Moreover, generated platinum(II) can activate nicotinamide adenine dinucleotide phosphate oxidases (NOXs), accelerating the conversion of oxygen to superoxide anions and enhancing downstream H2O2 levels. Next, Fe2+/Fe3+ ions released from Tf-PGINP-Pt rapidly converted H2O2 into highly toxic OH, causing DNA and mitochondrial membrane damage, resulting in cell ferroptosis. Notably, platinum(II) can coordinate with DNA bases and form Pt-DNA adducts, inhibiting DNA replication and inducing cell apoptosis. In addition, the contrast superimposed effect originated from Gd2O3 and Fe3O4 in Tf-PGINP-Pt endows accurate diagnostic capability for tumor identification, achieving MRI-guided dual-modal cancer therapy. Therefore, this work provides an unique and clinically promising strategy for accurate diagnosis and effective therapy of cancer.

Probing drug delivery and mechanisms of action in 3D spheroid cells by quantitative analysis.

Human tumor cells in a 3-dimensional (3D) spheroid can reflect the characteristics of solid tumors by forming cell-cell interactions and microenvironments. This makes 3D cell culture useful for preclinical stability and drug efficacy tests. In this study, the drug delivery and action mechanisms in SK-N-SH neuroblastoma cells cultured in 3D spheroids were quantitatively compared to those cultured in 2D monolayers using confocal microscopy imaging and inductively coupled plasma-mass spectrometry. In the 3D spheroids, cisplatin only accessed the surface, accumulating in the cells on the spheroid exterior. As a result, an increased cellular amount of cisplatin was required to obtain similar cytotoxicity in the 3D spheroid cells to that in 2D monolayers. The mechanisms of reduction of drug efficacy by dimethyl sulfoxide (DMSO) in the 3D spheroid cells compared to those in the 2D monolayer cells were further investigated. DMSO reduced the drug cytotoxicity by forming stable DMSO-substituted compounds that inhibited the cellular uptake of cisplatin and DNA-Pt adduct formation. The quantitative analysis used in this study is promising for understanding drug delivery and drug action mechanisms in cells in various microenvironments.

Oleandrin sensitizes human osteosarcoma cells to cisplatin by preventing degradation of the copper transporter 1.

A major problem in osteosarcoma treatment is cisplatin resistance. We have reported the anti-osteosarcoma effect of oleandrin; however, whether oleandrin sensitizes osteosarcoma to cisplatin is unknown. We investigated the chemosensitization of oleandrin and potential mechanisms in osteosarcoma cells U-2OS, SaOS-2, and MG-63. The median-effect analysis demonstrated that cisplatin+oleandrin exerted synergistic (U-2OS and MG-63) or additive effects (SaOS-2), which were consistent with the changes of the intracellular accumulation of platinum (Pt) and Pt-DNA adducts. Immunohistochemistry staining showed that the expression level of the mature form CTR1, the major influx transporter of cisplatin, was low in osteosarcoma tissue. However, oleandrin with or without cisplatin significantly increased the expression and membrane localization of the mature CTR1. Furthermore, CTR1 knockdown reversed the synergistic effect and decreased cisplatin uptake. The mRNA microarray analysis suggested that oleandrin downregulated the expression of proteasome-related genes, which was verified by the proteasome activity assay. Besides, the proteasome inhibitor MG132 upregulated the expression of the mature CTR1 in U-2OS and MG-63 cells. Overall, we conclude that oleandrin sensitizes osteosarcoma cells to cisplatin in synergistic or additive manners. The synergy results from the enhanced cisplatin uptake via oleandrin-mediated inhibition of proteasome activity and subsequent blockage of the mature CTR1 degradation.

The influence of the nonleaving group on the anticancer activity of tetrachlorido platinum(IV) complexes with pyridine/bipyridine derivatives

Due to their inertness, platinum(IV) complexes are well known potential candidates to improve the pharmacological properties and selective cellular uptake of commonly used platinum(II) anticancer agents. In these 6-coordinate prodrugs, the equatorial nonleaving groups are the only ligands which remain in the final Pt-DNA adducts and directly affect the DNA binding property. In an effort to discover the structure–activity relationship; in this report, two novel platinum(IV) complexes, trans-[Pt(3phpy)2Cl4] (1) and [Pt(4dtb-bpy)Cl4].DMSO (2) (3phpy = 3-phenylpyridine and 4dtb-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine) were prepared and fully characterized. Their in vitro activity was evaluated and compared with those of similar platinum(IV) complexes, containing unbranched ligands, trans-[Pt(py)2Cl4] and [Pt(bpy)Cl4]. Interestingly, complex 1, with phenylpyridine nonleaving ligands, demonstrated further antiproliferative properties among the studied platinum(IV) prodrugs. Moreover, the apoptosis rate in cell lines was also determined using flow cytometry. Furthermore, the resistance factor of complexes 1 and 2 were 1.1 and 1.3, respectively, using wild-type and cisplatin-resistant A2780 cell lines.

Acidity-triggered TAT-presenting nanocarriers augment tumor retention and nuclear translocation of drugs

Hierarchical targeting strategy can combat the sequential drug delivery barriers by changing their properties with response to tumor stimuli. Among these strategies, much less attention has been paid to address the issues of rapid tumor clearance and insufficient cellular translocation. In this work, we demonstrate that a transactivator of transcription (TAT)-presenting nanomedicine (DATAT-NP/Pt), apart from improving tumor accumulation and cellular uptake, can simultaneously enhance tumor retention and promote nuclear translocation of encapsulated platinum prodrugs, and thus improve therapeutic efficacy. Specifically, a protecting 2,3-dimethylmaleic anhydride (DA) corona on the nanomedicine prevented the TAT peptide from serum. DATAT-NP/Pt efficiently accumulated at the tumor site through the enhanced permeability and retention (EPR) effect, followed by acid-triggered TAT presenting within the tumor acidic microenvironment (pH ~ 6.8). The exposed TAT peptide augmented tumor retention and nuclear translocation of DATAT-NP/Pt. We used a tumor-on-a-chip microfluidic system to real-time mimic and analyze tumor accumulation and retention at physiological flow conditions and revealed that surface absorption of nanomedicines on tumors was critical in determining their tumor retention and clearance. Furthermore, the TAT peptide rapidly translocated the DATAT-NP/Pt into the perinuclear region, allowing for higher nuclear platinum concentrations and increased Pt-DNA adduct formation in nuclei, which consequently reversed cisplatin resistance. Our work presents a new strategy to overcome pathophysiological barriers of tumor clearance and insufficient cellular translocation and provides new insights for the design of cancer nanomedicines.