Click Chemistry-Based Force Spectroscopy Revealed Enhanced Binding Dynamics of Phosphorylated HMGB1 to Cisplatin-DNA.

Cisplatin, a cornerstone in cancer chemotherapy, is known for its DNA-binding capacity and forms lesions that lead to cancer cell death. However, the repair of these lesions compromises cisplatin's effectiveness. This study investigates how phosphorylation of HMGB1, a nuclear protein, modifies its binding to cisplatin-modified DNA (CP-DNA) and thus protects it from repair. Despite numerous methods for detecting protein-DNA interactions, quantitative approaches for understanding their molecular mechanism remain limited. Here, we applied click chemistry-based single-molecule force spectroscopy, achieving high-precision quantification of the interaction between phosphorylated HMGB1 and CP-DNA. This method utilizes a synergy of click chemistry and enzymatic ligation for precise DNA-protein immobilization and interaction in the system. Our results revealed that HMGB1 binds to CP-DNA with a significantly high rupture force of ∼130 pN, stronger than most natural DNA-protein interactions and varying across different DNA sequences. Moreover, Ser14 is identified as the key phosphorylation site, enhancing the interaction's kinetic stability by 35-fold. This increase in stability is attributed to additional hydrogen bonding suggested by molecular dynamics (MD) simulations. Our findings not only reveal the important role of phosphorylated HMGB1 in potentially improving cisplatin's therapeutic efficacy but also provide a precise method for quantifying protein-DNA interactions.

Cisplatin-loaded mesoporous polydopamine nanoparticles capped with MnO2 and coated with platelet membrane provide synergistic anti-tumor therapy.

A multifunctional nanoplatform was constructed in this work, with the goal of ameliorating the challenges faced with traditional cancer chemotherapy. Cisplatin (CP) was loaded into mesoporous polydopamine (mPDA) nanoparticles (NPs) with a drug loading of 15.8 ± 0.1 %, and MnO2 used as pore sealing agent. Finally, the NPs were wrapped with platelet membrane (PLTM). P-selectin on the PLTM can bind to CD44, which is highly expressed on the tumor cell membrane, so as to improve the targeting performance of the NPs. In addition, the CD47 on the PLTM can prevent the NPs from being phagocytosed by macrophages, which is conducive to immune escape. The final PLTM-CP@mPDA/MnO2 NPs were found to have a particle size of approximately 198 nm. MnO2 is degraded into Mn2+ in the tumor microenvironment, leading to CP release from the pores in the mPDA. CP both acts as a chemotherapy agent and can also increase the concentration of H2O2 in cells. Mn2+ can catalyze the conversion of H2O2 to OH, resulting in oxidative damage and chemodynamic therapy. In addition, Mn2+ can be used as a contrast agent in magnetic resonance imaging (MRI). In vitro and in vivo experiments were performed to explore the therapeutic effect of the NPs. When the concentration of CP is 30 µg/mL, the NPs cause approximately 50 % cell death. It was found that the PLTM-CP@mPDA/MnO2 NPs are targeted to cancerous cells, and in the tumor site cause extensive apoptosis. Tumor growth is thereby repressed. No negative off-target side effects were noted. MRI could be used to confirm the presence of the NPs in the tumor site. Overall, the nano-platform developed here provides cooperative chemotherapy and chemodynamic therapy, and can potentially be used for effective cancer treatment which could be monitored by MRI.

Structure-Guided Design of Ferritin-Platinum Prodrugs for Targeted Therapy of Esophageal Squamous Cell Carcinoma.

Due to its intrinsic tumor-targeting attribute, limited immunogenicity, and cage architecture, ferritin emerges as a highly promising nanocarrier for targeted drug delivery. In the effort to develop ferritin cage-encapsulated cisplatin (CDDP) as a therapeutic agent, we found unexpectedly that the encapsulation led to inactivation of the drug. Guided by the structural information, we deciphered the interactions between ferritin cages and CDDP, and we proposed a potential mechanism responsible for attenuating the antitumor efficacy of CDDP encapsulated within the cage. Six platinum prodrugs were then designed to avoid the inactivation. The antitumor activities of these ferritin-platinum prodrug complexes were then evaluated in cells of esophageal squamous cell carcinoma (ESCC). Compared with free CDDP, the complexes were more effective in delivering and retaining platinum in the cells, leading to increased DNA damage and enhanced cytotoxic action. They also exhibited improved pharmacokinetics and stronger antitumor activities in mice bearing ESCC cell-derived xenografts as well as patient-derived xenografts. The successful encapsulation also illustrates the critical significance of comprehending the interactions between small molecular drugs and ferritin cages for the development of precision-engineered nanocarriers.

Acidic solvent improves cisplatin action in in-vitro.

As cisplatin is one of the most broadly used chemotherapeutics, it is widely tested in vitro & in vivo assays, involving attempts to better understand its mechanism of action, develop strategies to mitigate its toxicity, or develop new drug combinations. Presently, for in vitro assays, dissolving cisplatin in dimethyl sulfoxide (DMSO) is discouraged due to its significant reduction in drug activity, Alternatively, inorganic solvents like normal saline (NS) are recommended. However, this approach is still problematic, including 1) instability of cisplatin in NS, 2) limited solubility, 3) the need to avoid long-term storage at -80 °C (or -20 °C) after dissolving, and 4) complications when combining with other DMSO-solubilized compounds. Here, we report a DMSO-HCl mixture as an alternative solvent to address these challenges. Cisplatin in DMSO-HCl not only retains comparable drug activity to cisplatin in NS but also exhibits increased stability over an extended period. Our brief report sheds light on cisplatin action, providing insights to aid in cancer research in vitro.

Platinum(0)-η2-1,2-(E)ditosylethene Complexes Bearing Phosphine, Isocyanide and N-Heterocyclic Carbene Ligands: Synthesis and Cytotoxicity towards Ovarian and Breast Cancer Cells.

A wide range of platinum(0)-η2-(E)-1,2-ditosylethene complexes bearing isocyanide, phosphine and N-heterocyclic carbene ancillary ligands have been prepared with high yields and selectivity. All the novel products underwent thorough characterization using spectroscopic techniques, including NMR and FT-IR analyses. Additionally, for some compounds, the solid-state structures were elucidated through X-ray diffractometry. The synthesized complexes were successively evaluated for their potential as anticancer agents against two ovarian cancer cell lines (A2780 and A2780cis) and one breast cancer cell line (MDA-MB-231). The majority of the compounds displayed promising cytotoxicity within the micromolar range against A2780 and MDA-MB-231 cells, with IC50 values comparable to or even surpassing those of cisplatin. However, only a subset of compounds was cytotoxic against cisplatin-resistant cancer cells (A2780cis). Furthermore, the assessment of antiproliferative activity on MRC-5 normal cells revealed certain compounds to exhibit in vitro selectivity. Notably, complexes 3d, 6a and 6b showed low cytotoxicity towards normal cells (IC50 > 100 µM) while concurrently displaying potent cytotoxicity against cancer cells.

Molecular targets of cisplatin in HeLa cells explored through competitive activity-based protein profiling strategy.

Cisplatin is widely used as anticancer drugs, and DNA is considered as the main target. Considering its high affinity towards cysteines and the important role of cystine containing proteins, we applied a competitive activity-based protein profiling strategy to identify protein cysteines that bind with cisplatin in HeLa cells. Living cells were treated with cisplatin at cytotoxic concentrations, then the protein was extracted. After labeling with desthiobiotin iodoacetamide (DBIA) probe, protein was precipitated, digested and isotopically labeled, subsequently the peptides were combined, and the biotinylated cysteine-containing peptides were enriched and quantified by LC-MS/MS. A total of 3571 peptides which originated from 1871 proteins were identified using the DBIA probe. Among them, 46 proteins were screened as targets, including proteins that have been identified as binding proteins by previous study. A novel cisplatin target, calpain-1 (CAPN1), was identified and validated as binding with cisplatin in vitro.

Analysis of free cisplatin in microdialysates and plasma ultrafiltrate by liquid chromatography-tandem mass spectrometry.

Cisplatin is a potent cytotoxic agent used in the treatment of various malignancies and exerts its antitumor effect through malignant cell DNA damage and apoptosis induction. Evaluation of systemic delivery of cisplatin is important in optimization of cisplatin treatment. However, accurate quantification of systemic cisplatin is challenging due to its various forms in circulation. This study aimed to develop a sensitive (LOQ < 0.1 µg/mL) and precise Ultra Performance Liquid Chromatography (UPLC) - Tandem Mass Spectrometry (MS/MS) method for quantifying free cisplatin in microdialysates and plasma. Furthermore the aim was to compare free cisplatin concentrations measured in standard plasma samples with those obtained from intravenous microdialysis catheters in a porcine model. The method developed utilizes dichloro(ethylenediamine)platinum(II) as an internal standard that co-elutes with cisplatin, ensuring precise correction for ion suppression/enhancement effects. The method was validated, demonstrating linearity up to 100 µg/mL and good intermediate precision (CV% < 6 %) in the range of 1.0-100 µg/mL, with an LOQ of 0.03 µg/mL. The pharmacokinetic parameters (AUC0-last, Cmax, T1/2, and Tmax) showed no significant differences between the two sampling methods. This validated LC-MS/MS method provides a reliable tool for quantifying systemic free cisplatin concentrations, facilitating future systemic and local pharmacokinetic evaluations for optimization of cisplatin-based cancer treatments.

Thermoresponsive carboplatin-releasing prodrugs.

Platinum-based anticancer drugs, while potent, are associated with numerous and severe side effects. Hyperthermia therapy is an effective adjuvant in anticancer treatment, however, clinically used platinum drugs have not been optimised for combination with hyperthermia. The derivatisation of existing anticancer drugs with appropriately chosen thermoresponsive moieties results in drugs being activated only at the heated site. Perfluorinated chains of varying lengths were installed on carboplatin, a clinically approved drug, leading to the successful synthesis of a series of mono- and di- substituted platinum(IV) carboplatin prodrugs. Some of these complexes display relevant thermosensitivity on ovarian cancer cell lines, i.e., being inactive at 37 °C while having comparable activity to carboplatin under mild hyperthermia (42 °C). Nuclear magnetic resonance spectroscopy and mass spectrometry indicated that carboplatin is likely the active platinum(II) anticancer agent upon reduction and cyclic voltammetry revealed that the length of the fluorinated alkyl chain has a strong influence on the rate of carboplatin formation, regulating the subsequent cytotoxicity.

A Nanoscale Trans-Platinum(II)-Based Supramolecular Coordination Self-Assembly with a Distinct Anticancer Mechanism.

Drug resistance significantly hampers the clinical application of existing platinum-based anticancer drugs. New platinum medications that possess distinct mechanisms of action are highly desired for the treatment of Pt-resistant cancers. Herein, a nanoscale trans-platinum(II)-based supramolecular coordination self-assembly (Pt-TCPP-BA) is prepared via using trans-[PtCl2(pyridine)(NH3)] (transpyroplatin), tetracarboxylporphyrin (TCPP), and benzoic acid (BA) as building blocks to combat drug resistance in platinum-based chemotherapy. Mechanistic studies indicate that Pt-TCPP-BA shows a hydrogen-peroxide-responsive dissociation behavior along with the generation of bioactive trans-Pt(II) and TCPP-Pt species. Different from cisplatin, these degradation products interact with DNA via interstrand cross-links and small groove binding, and induce significant upregulation of cell-death-related proteins such as p53, cleaved caspase 3, p21, and phosphorylated H2A histone family member X in cisplatin-resistant cancer cells. As a result, Pt-TCPP-BA exhibits potent killing effects against Pt-resistant tumors both in vitro and in vivo. Overall, this work not only provides a new platinum drug for combating drug-resistant cancer but also offers a new paradigm for the development of platinum-based supramolecular anticancer drugs.

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.

Antitumor active trans­platinum complexes through metabolic stability and enhanced cellular accumulation.

Utilizing isoquinoline as a carrier ligand, we have evaluated the reactivity of selected trans­platinum planar amine (TPA) carboxylate compounds by varying the leaving carboxylate group (acetate, hydroxyacetate, and lactate) in an effort to optimize the cytotoxic and metabolic efficiency. To measure the pharmacological properties of these compounds, a combination of systematic biophysical and biological studies were carried out mainly involving substitution reaction with NAM (N-acetyl-methionine), effects on DNA structural perturbation, cytotoxicity, cellular accumulation, metabolic stability, and cell cycle effects. TPA compounds showed minimal losses in cytotoxic efficacy and outperformed cisplatin after pre-incubation with serum, while displaying a distinct micromolar cytotoxic activity with minimal DNA binding and unaltered cell cycle. Monitoring the TPA compounds with NAM suggests the following trend for the reactivity: hydroxyacetate > lactate > acetate. The same trend was seen for the cytotoxicity in tumor cells and DNA binding, while the rate of drug inactivation/protein binding in cells was not significantly different among these leaving groups. Thus, our results show superior cellular efficacy of TPA compounds and distinct micromolar cytotoxic activities different than cisplatin. Moreover, we found the TPA compounds had prolonged survival and decreased tumor burden compared to the control mice in a relevant human ovarian cancer mouse model with A2780 cells expressing luciferase. Therefore, we propose that further optimization of the basic TPA structure can give further enhanced in vivo activity and may eventually be translated into the development of clinically relevant non-traditional platinum drugs.

On the mechanism of action of arsenoplatins: arsenoplatin-1 binding to a B-DNA dodecamer.

The reaction of Pt-based anticancer agents with arsenic trioxide affords robust complexes known as arsenoplatins. The prototype of this family of anticancer compounds is arsenoplatin-1 (AP-1) that contains an As(OH)2 fragment linked to a Pt(II) moiety derived from cisplatin. Crystallographic and spectrometric studies of AP-1 binding to a B-DNA double helix dodecamer are presented here, in comparison with cisplatin and transplatin. Results reveal that AP-1, cisplatin and transplatin react differently with the DNA model system. Notably, in the AP-1/DNA systems, the Pt-As bond can break down with time and As-containing fragments can be released. These results have implications for the understanding of the mechanism of action of arsenoplatins.

Evidence of direct interaction between cisplatin and the caspase-cleaved prostate apoptosis response-4 tumor suppressor.

Prostate apoptosis response-4 (Par-4) tumor suppressor protein has gained attention as a potential therapeutic target owing to its unique ability to selectively induce apoptosis in cancer cells, sensitize them to chemotherapy and radiotherapy, and mitigate drug resistance. It has recently been reported that Par-4 interacts synergistically with cisplatin, a widely used anticancer drug. However, the mechanistic details underlying this relationship remain elusive. In this investigation, we employed an array of biophysical techniques, including circular dichroism spectroscopy, dynamic light scattering, and UV-vis absorption spectroscopy, to characterize the interaction between the active caspase-cleaved Par-4 (cl-Par-4) fragment and cisplatin. Additionally, elemental analysis was conducted to quantitatively assess the binding of cisplatin to the protein, utilizing inductively coupled plasma-optical emission spectroscopy and atomic absorption spectroscopy. Our findings provide evidence of direct interaction between cl-Par-4 and cisplatin, and reveal a binding stoichiometry of 1:1. This result provides insights that could be useful in enhancing the efficacy of cisplatin-based and tumor suppressor-based cancer therapies.

Modeling the Cellular Uptake of Functionalized Carbon Nanohorns Loaded with Cisplatin through a Breast Cancer Cell Membrane.

The cisplatin encapsulation into carbon nanohorns (CNH) is a promising nanoformulation to circumvent the drug dissipation and to specifically accumulate it in tumor sites. Herein, biased molecular dynamics simulations were used to analyze the transmembrane transport of the CNH loaded with cisplatin through a breast cancer cell membrane prototype. The simulations revealed a four-stage mechanism: approach, insertion, permeation, and internalization. Despite the lowest structural disturbance of the membrane provided by the nanocarrier, the average free energy barrier for the translocation was 55.2 kcal mol-1, suggesting that the passive process is kinetically unfavorable. In contrast, the free energy profiles revealed potential wells of -6.8 kcal mol-1 along the insertion stage in the polar heads region of the membrane, which might enhance the retention of the drug in tumor sites; therefore, the most likely cisplatin delivery mechanism should involve the adsorption and retention of CNH on the surface of cancer cells, allowing the loaded cisplatin be slowly released and passively transported through the cell membrane.

Enhanced potency of a chloro-substituted polyaromatic platinum(II) complex and its platinum(IV) prodrug against lung cancer.

The present study investigates the anti-neoplastic activity of a platinum (II) complex, Pt(II)5ClSS, and its platinum (IV) di-hydroxido analogue, Pt(IV)5ClSS, against mesenchymal cells (MCs), lung (A549), melanoma (A375) and breast (MDA-MB-231) cancer cells. Both complexes exhibited up to 14-fold improved cytotoxicity compared to cisplatin. NMR was used to determine that ∼25 % of Pt(IV)5ClSS was reduced to Pt(II)5ClSS in the presence of GSH (Glutathione) after 72 h. The complex 1H NMR spectra acquired for Pt(II)5ClSS with GSH shows evidence of degradation and environmental effects (∼30 %). The prominence of the 195Pt peak at âˆ¼ -2800 ppm suggests that a significant amount of Pt(II)5ClSS remained in the mixture. Pt(II)5ClSS and Pt(IV)5ClSS have shown exceptional selectivity to cancer cells in comparison to MCs (IC50 > 150 µM). Western blot analysis of Pt(II)5ClSS and Pt(IV)5ClSS on A549 cells revealed significant upregulation of cleaved PARP-1, BAX/Bcl2 ratio, cleaved caspase 3 and cytochrome thus suggesting apoptosis was induced through the intrinsic pathway. Flow cytometry also revealed significant cell death by apoptosis. Treatment with Pt(II)5ClSS and Pt(IV)5ClSS also showed significant amounts of free radical production while the COMET assay showed that both complexes cause minimal DNA damage. Cellular uptake results via ICP-MS suggest a time-dependent active mode of transport for both complexes with Pt(II)5ClSS being transported at a higher rate compared to Pt(IV)5ClSS. A Dose Escalation Study carried out on BALB/c mice showed that Pt(II)5ClSS and Pt(IV)5ClSS were approximately 8- folds and 12.5-folds, respectively, more tolerated than cisplatin. The present study provides evidence that both complexes may have the characteristics of an efficient and potentially safe anti-tumor drug that could support NSCLC treatment.

Synthesis and Characterisation of Platinum(II) Diaminocyclohexane Complexes with Pyridine Derivatives as Anticancer Agents.

Cisplatin-type covalent chemotherapeutics are a cornerstone of modern medicinal oncology. However, these drugs remain encumbered with dose-limiting side effects and are susceptible to innate and acquired resistance. The bulk of platinum anticancer research has focused on Cisplatin and its derivatives. Here, we take inspiration from the design of platinum complexes and ligands used successfully with other metals to create six novel complexes. Herein, the synthesis, characterization, DNA binding affinities, and lipophilicity of a series of non-traditional organometallic Pt(II)-complexes are described. These complexes have a basic [Pt(PL)(AL)]Cl2 molecular formula which incorporates either 2-pyrrolidin-2-ylpyridine, 2-(1H-Imidazol-2-yl)pyridine, or 2-(2-pyridyl)benzimidazole as the PL; the AL is resolved diaminocyclohexane. Precursor [Pt(PL)(Cl)2] complexes were also characterized for comparison. While the cytotoxicity and DNA binding properties of the three precursors were unexceptional, the corresponding [Pt(PL)(AL)]2+ complexes were promising; they exhibited different DNA binding interactions compared with Cisplatin but with similar, if not slightly better, cytotoxicity results. Complexes with 2-pyrrolidin-2-ylpyridine or 2-(2-pyridyl)benzimidazole ligands had similar DNA binding properties to those with 2-(1H-Imidazol-2-yl)pyridine ligands but were not as cytotoxic to all cell lines. The variation in activity between cell lines was remarkable and resulted in significant selectivity indices in MCF10A and MCF-7 breast cancer cell lines, compared with previously described similar Pt(II) complexes such as 56MESS.

Novel design of dual-action Pt(IV) anticancer pro-drugs based on cisplatin and derivatives of the tyrosine kinase inhibitors imatinib and nilotinib.

Tyrosine kinases (TKs) are emerging as important targets in cancer therapy and some of their inhibitors, TKIs (e.g. imatinib and nilotinib), are FDA-approved drugs that are used as selective anti-cancer therapeutics against cell lines that overexpress TKs. Many examples of metal-based complexes functionalised with TKIs are reported in the literature but very few have been functionalised with platinum. Here we report the design, a detailed computational analysis/simulation, the complete chemical characterisation and the preliminary biological evaluation of two novel Pt(IV) anticancer pro-drugs based on cisplatin tethered with a derivative of either imatinib or nilotinib in the axial position. Pt(IV) complexes are a strategic scaffold in combination therapy due to their axial ligands that can be functionalised to form dual action drugs. The activation by reduction releases the Pt(II) core and the axial ligands upon cellular internalisation. The antiproliferative activity and the TK inhibition properties of the novel adducts are analysed with a theoretical approach and confirmed in vitro with preliminary biological assays.

Single-Cell ICP-MS in Combination with Fluorescence-Activated Cell Sorting for Investigating the Effects of Nanotransported Cisplatin(IV) Prodrugs.

The combined use of fluorescence-activated cell sorting (FACS) and single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) is reported, for the first time, in this work. It is applied to evaluate the differences between the cellular uptake of ultrasmall iron oxide nanoparticles (FeNPs) loaded with cisplatin(IV) prodrug (FeNPs-Pt(IV)) and cisplatin regarding cell viability. For this aim, FACS is applied to separate viable, apoptotic, and necrotic A2780 ovarian cancer cells after exposing them to the nanotransported prodrug and cisplatin, respectively. The different sorted cell populations are individually analyzed using quantitative SC-ICP-MS to address the intracellular amount of Pt. The highest Pt intracellular content occurs in the apoptotic cell population (about 2.1 fg Pt/cell) with a narrow intercellular distribution when using FeNPs-Pt(IV) nanoprodrug and containing the largest number of cells (75% of the total). In the case of the cisplatin-treated cells, the highest Pt content (about 1.6 fg Pt/cell) could be determined in the viable sorted cell population. The combined methodology, never explored before, permits a more accurate picture of the effect of the intracellular drug content together with the cell death mechanisms associated with the free drug and the nanotransported prodrug, respectively, and opens the door to many possible single-cell experiments in sorted cell populations.

Biological interaction of Pt complex with imidazole derivative as an anticancer compound with DNA: Experimental and theoretical studies.

This investigation is applied to find out interesting information on DNA binding mode with Pt(II) derivative of two N, N bidentate ligands in treating cancer. Thus, one new water-soluble platinum complex with FIP and phen with a new formula of [Pt(phen)(FIP)](NO3)2 was prepared and specified. DFT data can be used to evaluate geometry parameters. Based on the ADMET prediction, this complex can be considered a drug-like agent. Cytotoxicity property was evaluated against some human cancerous MCF7, A549, and HCT116 cell lines. Accumulation of Pt complex, cisplatin, and oxaliplatin in each cancerous cell was determined, which is probably related to their lipophilicity and solubility properties. The binding mode of the complex to ct-DNA was investigated by fluorescence spectroscopy, circular dichroism, and molecular docking simulation. The viscosity of DNA by different concentrations of EB and Pt complex titration shows Pt complex interacts with DNA via groove binding like the spectroscopic binding result. In the MD study, DNA helix, RMSD, and RMSF analysis showed that DNA stability decreased and that the majority of residues left the initial state. DNA increased residual deviations and flexibility are linked to an increase in its gyratory radius, which is consistent with the findings of the experiments.

IRMPD spectroscopy and quantum-chemical simulations of the reaction products of cisplatin with the dipeptide CysGly.

The inorganic antineoplastic drug cisplatin was made to react in solution with the dipeptide cysteinylglycine (CysGly), chosen as a functional model of glutathione, and the reaction products were analyzed using electrospray ionization mass spectrometry (ESI-MS). Selected complexes, i.e., the primary substitution product cis-[PtCl(NH3)2(CysGly)]+ and the chelate cis-[PtCl(NH3)(CysGly)]+, were submitted to IR multiple photon dissociation (IRMPD) spectroscopy obtaining their vibrational features. The experimental IR ion spectra were compared with the calculated IR absorptions of different plausible isomeric families, finding CysGly to bind preferentially platinum(II) via its deprotonated thiolic group in the monovalent complex, cis-[PtCl(NH3)2(CysGly)]+, and to evolve in the S,N-bound chelate structure cis-[PtCl(NH3)(CysGly)]+ through the SH and NH2 functionality of the cysteine residue. Moreover, our findings indicate that the platination reaction does not affect the CysGly peptide bond, which remains in its trans configuration. These results provide additional insights into the reactivity of Pt(II)-complexes with glutathione which is involved in cellular cisplatin resistance.