Cisplatin inhibits chromatin remodeling, transcription factor binding, and transcription from the mouse mammary tumor virus promoter in vivo

Cisplatin in Liver Cancer Therapy

Hepatocellular carcinoma (HCC) is the most common primary liver tumor and is often diagnosed at an unresectable advanced stage. Systemic chemotherapy as well as transarterial chemoembolization (TACE) and hepatic arterial infusion chemotherapy (HAIC) are used to treat advanced HCC. TACE and HAIC have long been the standard of care for patients with unresectable HCC but are limited to the treatment of intrahepatic lesions. Systemic chemotherapy with doxorubicin or chemohormonal therapy with tamoxifen have also been considered, but neither has demonstrated survival benefits. In the treatment of unresectable advanced HCC, cisplatin is administered transhepatic arterially for local treatment. Subsequently, for cisplatin-refractory cases due to drug resistance, a shift to systemic therapy with a different mechanism of action is expected to produce new antitumor effects. Cisplatin is also used for the treatment of liver tumors other than HCC. This review summarizes the action and resistance mechanism of cisplatin and describes the treatment of the major hepatobiliary cancers for which cisplatin is used as an anticancer agent, with a focus on HCC.

Revisiting the Anti-Cancer Toxicity of Clinically Approved Platinating Derivatives

Cisplatin (CDDP), carboplatin (CP), and oxaliplatin (OXP) are three platinating agents clinically approved worldwide for use against a variety of cancers. They are canonically known as DNA damage inducers; however, that is only one of their mechanisms of cytotoxicity. CDDP mediates its effects through DNA damage-induced transcription inhibition and apoptotic signalling. In addition, CDDP targets the endoplasmic reticulum (ER) to induce ER stress, the mitochondria via mitochondrial DNA damage leading to ROS production, and the plasma membrane and cytoskeletal components. CP acts in a similar fashion to CDDP by inducing DNA damage, mitochondrial damage, and ER stress. Additionally, CP is also able to upregulate micro-RNA activity, enhancing intrinsic apoptosis. OXP, on the other hand, at first induces damage to all the same targets as CDDP and CP, yet it is also capable of inducing immunogenic cell death via ER stress and can decrease ribosome biogenesis through its nucleolar effects. In this comprehensive review, we provide detailed mechanisms of action for the three platinating agents, going beyond their nuclear effects to include their cytoplasmic impact within cancer cells. In addition, we cover their current clinical use and limitations, including side effects and mechanisms of resistance.

Dual-Drug Nanosystem: Etoposide Prodrug and Cisplatin Coloaded Nanostructured Lipid Carriers for Lung Cancer Therapy

Purpose

Cisplatin (CDDP) and etoposide (Etp) are recommended first-line therapy for lung cancer. Nanostructured lipid carriers (NLCs) are engineered to deliver drugs for lung cancer treatment. In the present study, NLCs were applied to coload an Etp prodrug (EtpP) and CDDP.

Methods

The Etp prodrug was synthesized by linking the phenolic hydroxyl group of Etp with polyethylene glycol (PEG). EtpP and CDDP coencapsulated NLCs (EtpP-CDDP NLCs) were prepared using film ultrasound. Cytotoxicity of drugs and drug-containing NLCs was assessed by evaluating cell viability using MTT assays. In vivo antitumor efficiency of EtpP-CDDP NLCs was evaluated on lung cancer-bearing xenografts.

Results

EtpP-CDDP NLCs showed a uniformly spherical morphology with a size of 176.8±4.9 nm and -potential of -31.9±3.2 mV. Cellular uptake efficiency of EtpP-CDDP NLCs was 57.4%±3.9% on A549/DDP cells. EtpP-CDDP NLCs exhibited more sustained plasma retention, the highest drug distribution in tumors, and the highest tumor-inhibition rates in lung tumor-bearing mice.

Conclusion

EtpP-CDDP NLCs improved tumor-cell uptake, cytotoxicity, and tumor-inhibition efficiency, and could be used as a promising drug-delivery system for lung cancer combination therapy.

Targeting HNRNPU to overcome cisplatin resistance in bladder cancer

Purpose

The overall response of cisplatin-based chemotherapy in bladder urothelial carcinoma (BUC) remains unsatisfactory due to the complex pathological subtypes, genomic difference, and drug resistance. The genes that associated with cisplatin resistance remain unclear. Herein, we aimed to identify the cisplatin resistance associated genes in BUC.

Experimental design

The cytotoxicity of cisplatin was evaluated in six bladder cancer cell lines to compare their responses to cisplatin. The T24 cancer cells exhibited the lowest sensitivity to cisplatin and was therefore selected to explore the mechanisms of drug resistance. We performed genome-wide CRISPR screening in T24 cancer cells in vitro, and identified that the gene heterogeneous nuclear ribonucleoprotein U (HNRNPU) was the top candidate gene related to cisplatin resistance. Epigenetic and transcriptional profiles of HNRNPU-depleted cells after cisplatin treatment were analyzed to investigate the relationship between HNRNPU and cisplatin resistance. In vivo experiments were also performed to demonstrate the function of HNRNPU depletion in cisplatin sensitivity.

Results

Significant correlation was found between HNRNPU expression level and sensitivity to cisplatin in bladder cancer cell lines. In the high HNRNPU expressing T24 cancer cells, knockout of HNRNPU inhibited cell proliferation, invasion, and migration. In addition, loss of HNRNPU promoted apoptosis and S-phase arrest in the T24 cells treated with cisplatin. Data from The Cancer Genome Atlas (TCGA) demonstrated that HNRNPU expression was significantly higher in tumor tissues than in normal tissues. High HNRNPU level was negatively correlated with patient survival. Transcriptomic profiling analysis showed that knockout of HNRNPU enhanced cisplatin sensitivity by regulating DNA damage repair genes. Furthermore, it was found that HNRNPU regulates chemosensitivity by affecting the expression of neurofibromin 1 (NF1).

Conclusions

Our study demonstrated that HNRNPU expression is associated with cisplatin sensitivity in bladder urothelial carcinoma cells. Inhibition of HNRNPU could be a potential therapy for cisplatin-resistant bladder cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01517-9.

Chromatin accessibility regulates chemotherapy-induced dormancy and reactivation

Cisplatin-based chemotherapy remains the standard care for non-small cell lung cancer (NSCLC) patients. Relapse after chemotherapy-induced dormancy affects the overall survival of patients. The evolution of cancer cells under chemotherapy stress is regulated by transcription factors (TFs) with binding sites initially buried deep within inaccessible chromatin. The transcription machinery and dynamic epigenetic alterations during the process of dormancy-reactivation of lung cancer cells after chemotherapy need to be investigated. Here, we investigated the chromatin accessibility of lung cancer cells after cisplatin treatment, using an assay for transposase-accessible chromatin sequencing (ATAC-seq). We observed that global chromatin accessibility was extensively improved. Transcriptional Regulatory Relationships Unraveled by Sentence-based Text mining (TRRUST) v.2 was used to elucidate TF-target interaction during the process of dormancy and reactivation. Enhancer regions and motifs specific to key TFs including JUN, MYC, SMAD3, E2F1, SP1, CTCF, SMAD4, STAT3, NFKB1, and KLF4 were enriched in differential loci ATAC-seq peaks of dormant and reactivated cancer cells induced by chemotherapy. The findings suggest that these key TFs regulated gene expressions during the process of dormancy and reactivation of cancer cells through altering promoter accessibility of target genes. Our study helps advance understanding of how cancer cells adapt to the stress induced by chemotherapy through TF binding motif accessibility.

Cisplatin fastens chromatin irreversibly even at a high chloride concentration

Cisplatin is one of the most potent anti-cancer drugs developed so far. Recent studies highlighted several intriguing roles of histones in cisplatin's anti-cancer effect. Thus, the effect of nucleosome formation should be considered to give a better account of the anti-cancer effect of cisplatin. Here we investigated this important issue via single-molecule measurements. Surprisingly, the reduced activity of cisplatin under [NaCl] = 180 mM, corresponding to the total concentration of cellular ionic species, is still sufficient to impair the integrity of a nucleosome by retaining its condensed structure firmly, even against severe mechanical and chemical disturbances. Our finding suggests that such cisplatin-induced fastening of chromatin can inhibit nucleosome remodelling required for normal biological functions. The in vitro chromatin transcription assay indeed revealed that the transcription activity was effectively suppressed in the presence of cisplatin. Our direct physical measurements on cisplatin-nucleosome adducts suggest that the formation of such adducts be the key to the anti-cancer effect by cisplatin.

Revealing DNA Structure at Liquid/Solid Interfaces by AFM-Based High-Resolution Imaging and Molecular Spectroscopy

DNA covers the genetic information in all living organisms. Numerous intrinsic and extrinsic factors may influence the local structure of the DNA molecule or compromise its integrity. Detailed understanding of structural modifications of DNA resulting from interactions with other molecules and surrounding environment is of central importance for the future development of medicine and pharmacology. In this paper, we review the recent achievements in research on DNA structure at nanoscale. In particular, we focused on the molecular structure of DNA revealed by high-resolution AFM (Atomic Force Microscopy) imaging at liquid/solid interfaces. Such detailed structural studies were driven by the technical developments made in SPM (Scanning Probe Microscopy) techniques. Therefore, we describe here the working principles of AFM modes allowing high-resolution visualization of DNA structure under native (liquid) environment. While AFM provides well-resolved structure of molecules at nanoscale, it does not reveal the chemical structure and composition of studied samples. The simultaneous information combining the structural and chemical details of studied analyte allows achieve a comprehensive picture of investigated phenomenon. Therefore, we also summarize recent molecular spectroscopy studies, including Tip-Enhanced Raman Spectroscopy (TERS), on the DNA structure and its structural rearrangements.

Multiaction Platinum(IV) Prodrug Containing Thymidylate Synthase Inhibitor and Metabolic Modifier against Triple-Negative Breast Cancer

Multifunctional platinum^IV anticancer prodrugs have the potential to enrich the anticancer properties and overcome the clinical problems of drug resistance and side effects of platinum^II anticancer agents. Herein, we develop dual and triple action platinum^IV complexes with targeted and biological active functionalities. One complex (PFL) that consists of cisplatin, tegafur, and lonidamine exhibits strong cytotoxicity against triple negative breast cancer (TNBC) cells. Cellular uptake and distribution studies reveal that PFL mainly accumulates in mitochondria. As a result, PFL disrupts the mitochondrial ultrastructure and induces significant alterations in the mitochondrial membrane potential, which further leads to an increase in production of reactive oxygen species (ROS) and a decrease in ATP synthesis in MDA-MB-231 TNBCs. Western blot analysis reveals the formation of ternary complex of thymidylate synthase, which shows the intracellular conversion of tegafur into 5-FU after its release from PFL. Furthermore, treatment with PFL impairs the mitochondrial function, leading to the inhibition of glycolysis and mitochondrial respiration and induction of apoptosis through the mitochondrial pathway. The RNA-sequencing experiment shows that PFL can perturb the pathways involved in DNA synthesis, DNA damage, metabolism, and transcriptional activity. These findings demonstrate that PFL intervenes in several cellular processes including DNA damage, thymidylate synthase inhibition, and perturbation of the mitochondrial bioenergetics to kill the cancer cells. The results highlight the significance of a triple-action prodrug for efficient anticancer therapy for TNBCs.

Mitochondria-targeting monofunctional platinum(ii)–lonidamine conjugates for cancer cell de-energization

We report the rational design and anticancer mechanism studies of novel mitochondria-targeting monofunctional Pt(ii)–lonidamine conjugates for the selective de-energization of cancer cells.

P-MAPA immunotherapy potentiates the effect of cisplatin on serous ovarian carcinoma through targeting TLR4 signaling

Background

Toll-like receptors (TLRs) are transmembrane proteins expressed on the surface of ovarian cancer (OC) and immune cells. Identifying the specific roles of the TLR-mediated signaling pathways in OC cells is important to guide new treatments. Because immunotherapies have emerged as the adjuvant treatment for patients with OC, we investigated the effect of a promising immunotherapeutic strategy based on protein aggregate magnesium-ammonium phospholinoleate-palmitoleate anhydride (P-MAPA) combined with cisplatin (CIS) on the TLR2 and TLR4 signaling pathways via myeloid differentiation factor 88 (MyD88) and TLR-associated activator of interferon (TRIF) in an in vivo model of OC.

Methods

Tumors were chemically induced by a single injection of 100 μg of 7,12-dimethylbenz(a)anthracene (DMBA) directly under the left ovarian bursa in Fischer 344 rats. After the rats developed serous papillary OC, they were given P-MAPA, CIS or the combination P-MAPA+CIS as therapies. To understand the effects of the treatments, we assessed the tumor size, histopathology, and the TLR2- and TLR4-mediated inflammatory responses.

Results

Although CIS therapy was more effective than P-MAPA in reducing the tumor size, P-MAPA immunotherapy significantly increased the expressions of TLR2 and TLR4. More importantly, the combination of P-MAPA with CIS showed a greater survival rate compared to CIS alone, and exhibited a significant reduction in tumor volume compared to P-MAPA alone. The combination therapy also promoted the increase in the levels of the following OC-related proteins: TLR4, MyD88, TRIF, inhibitor of phosphorylated NF-kB alpha (p-IkBα), and nuclear factor kappa B (NF-kB p65) in both cytoplasmic and nuclear sites. While P-MAPA had no apparent effect on tumor necrosis factor alpha (TNF-α) and interleukin (IL)-6, it seems to increase interferon-γ (IFN-γ), which may induce the Thelper (Th1)-mediated immune response.

Conclusion

Collectively, our results suggest that P-MAPA immunotherapy combined with cisplatin could be considered an important therapeutic strategy against OC cells based on signaling pathways activated by TLR4.

Dynamic maps of UV damage formation and repair for the human genome

Formation and repair of UV-induced DNA damage in human cells are affected by cellular context. To study factors influencing damage formation and repair genome-wide, we developed a highly sensitive single-nucleotide resolution damage mapping method [high-sensitivity damage sequencing (HS-Damage-seq)]. Damage maps of both cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4) photoproducts [(6-4)PPs] from UV-irradiated cellular and naked DNA revealed that the effect of transcription factor binding on bulky adducts formation varies, depending on the specific transcription factor, damage type, and strand. We also generated time-resolved UV damage maps of both CPDs and (6-4)PPs by HS-Damage-seq and compared them to the complementary repair maps of the human genome obtained by excision repair sequencing to gain insight into factors that affect UV-induced DNA damage and repair and ultimately UV carcinogenesis. The combination of the two methods revealed that, whereas UV-induced damage is virtually uniform throughout the genome, repair is affected by chromatin states, transcription, and transcription factor binding, in a manner that depends on the type of DNA damage.

Comparison of different methods for erythroid differentiation in the K562 cell line

OBJECTIVE

To compare methods for erythroid differentiation of K562 cells that will be promising in the treatment of beta-thalassemia by inducing γ-globin synthesis.

RESULTS

Cells were treated separately with: RPMI 1640 medium without glutamine, RPMI 1640 medium without glutamine supplemented with 1 mM sodium butyrate, RPMI 1640 medium supplemented with 1 mM sodium butyrate, 25 µg cisplatin/ml, 0.1 µg cytosine arabinoside/ml. The highest differentiation (84 %) with minimum toxicity was obtained with cisplatin at 15 µg /ml. Real-time RT-PCR showed that expression of the γ-globin gene was significantly higher in the cells differentiated with cisplatin compared to undifferentiated cells (P < 0.001).

CONCLUSIONS

Cisplatin is useful in the experimental therapy of ß-globin gene defects and can be considered for examining the basic mechanism of γ-reactivation.

Visualizing inhibition of nucleosome mobility and transcription by cisplatin-DNA interstrand crosslinks in live mammalian cells

Cisplatin is a widely used anticancer drug that acts by binding DNA and causing the formation of intrastrand and interstrand (ICL) crosslinks, but the precise downstream effects of the latter damage are not well understood. In this study, we investigated the influence of cisplatin ICLs on synthetic nucleosomes that were platinated in a site-specific manner in vitro and on gene transcription in live mammalian cells. Nucleosome core particles that we constructed contained site-specific cisplatin 5'-d(G*pC)/5'-d(G*pC) ICLs, where the asterisk denotes the platinated nucleoside, to examine the influence of platinum lesions on the dynamic behavior of nucleosomes in solution. A cisplatin ICL, but not a 1,2-d(GpG) crosslink, significantly inhibited ATP-independent histone octamer-DNA sliding. We also used a novel linearization-recircularization strategy described here to synthesize mammalian expression vectors containing site-specific cisplatin ICLs. Plasmid vectors were tested in live mammalian cells to study the transcription inhibition effects of cisplatin ICLs in the context of two different repair backgrounds. Cisplatin ICLs inhibit transcription as effectively as 1,2-d(GpG) crosslinks. We determined that nucleotide excision repair plays a key role in the removal of cisplatin ICLs, acting in a replication-independent fashion. We also found that loss of mismatch repair function dramatically attenuates the transcription inhibition effects by cisplatin ICLs but not 1,2-d(GpG) intrastrand crosslinks. Our results revealed the unique properties of cisplatin ICLs on nucleosome mobility and on transcription, and they defined how these adducts act in a manner completely different from that used for cisplatin 1,2-d(GpG) crosslinks. These new findings provide direct support for a role of ICLs in the pharmacologic activities of cisplatin, despite the lower frequency of their formation.

Consequences of cisplatin binding on nucleosome structure and dynamics

The effects of cisplatin binding to DNA were explored at the nucleosome level to incorporate key features of the eukaryotic nuclear environment. An X-ray crystal structure of a site-specifically platinated nucleosome carrying a 1,3-cis-{Pt(NH₃)₂}²+-d(GpTpG) intrastrand cross-link reveals the details of how this adduct dictates the rotational positioning of DNA in the nucleosome. Results from in vitro nucleosome mobility assays indicate that a single platinum adduct interferes with ATP-independent sliding of DNA around the octamer core. Data from in vitro transcription experiments suggest that RNA polymerases can successfully navigate along cisplatin-damaged DNA templates that contain nucleosomes, but stall when the transcription elongation complex physically contacts a platinum cross-link located on the template strand. These results provide information about the effects of cisplatin binding to nuclear DNA and enhance our understanding of the mechanism of transcription inhibition by platinum anticancer compounds.

Redox state-dependent interaction of HMGB1 and cisplatin-modified DNA

HMGB1, one of the most abundant nuclear proteins, has a strong binding affinity for cisplatin-modified DNA. It has been proposed that HMGB1 enhances the anticancer efficacy of cisplatin by shielding platinated DNA lesions from repair. Two cysteine residues in HMGB1 domain A form a reversible disulfide bond under mildly oxidizing conditions. The reduced domain A protein binds to a 25-bp DNA probe containing a central 1,2-d(GpG) intrastrand cross-link, the major platinum-DNA adduct, with a 10-fold greater binding affinity than the oxidized domain A. The binding affinities of singly and doubly mutated HMGB1 domain A, respectively deficient in one or both cysteine residues that form the disulfide bond, are unaffected by changes in external redox conditions. The redox-dependent nature of the binding of HMGB1 domain A to cisplatin-modified DNA suggests that formation of the intradomain disulfide bond induces a conformational change that disfavors binding to cisplatin-modified DNA. Hydroxyl radical footprinting analyses of wild-type domain A bound to platinated DNA under different redox conditions revealed identical cleavage patterns, implying that the asymmetric binding mode of the protein across from the platinated lesion is conserved irrespective of the redox state. The results of this study reveal that the cellular redox environment can influence the interaction of HMGB1 with the platinated DNA and suggest that the redox state of the A domain is a potential factor in regulating the role of the protein in modulating the activity of cisplatin as an anticancer drug.

Mitogen-activated protein (MAP) kinase/MAP kinase phosphatase regulation: roles in cell growth, death, and cancer

Mitogen-activated protein kinase dual-specificity phosphatase-1 (also called MKP-1, DUSP1, ERP, CL100, HVH1, PTPN10, and 3CH134) is a member of the threonine-tyrosine dual-specificity phosphatases, one of more than 100 protein tyrosine phosphatases. It was first identified approximately 20 years ago, and since that time extensive investigations into both mkp-1 mRNA and protein regulation and function in different cells, tissues, and organs have been conducted. However, no general review on the topic of MKP-1 exists. As the subject matter pertaining to MKP-1 encompasses many branches of the biomedical field, we focus on the role of this protein in cancer development and progression, highlighting the potential role of the mitogen-activated protein kinase (MAPK) family. Section II of this article elucidates the MAPK family cross-talk. Section III reviews the structure of the mkp-1 encoding gene, and the known mechanisms regulating the expression and activity of the protein. Section IV is an overview of the MAPK-specific dual-specificity phosphatases and their role in cancer. In sections V and VI, mkp-1 mRNA and protein are examined in relation to cancer biology, therapeutics, and clinical studies, including a discussion of the potential role of the MAPK family. We conclude by proposing an integrated scheme for MKP-1 and MAPK in cancer.

Inhibition of transcription by platinum antitumor compounds

Cisplatin, carboplatin, and oxaliplatin are three FDA-approved members of the platinum anticancer drug family. These compounds induce apoptosis in tumor cells by binding to nuclear DNA, forming a variety of structural adducts and triggering cellular responses, one of which is the inhibition of transcription. In this report we present (i) a detailed review of the structural investigations of various Pt-DNA adducts and the effects of these lesions on global DNA geometry; (ii) research detailing inhibition of cellular transcription by Pt-DNA adducts; and (iii) a mechanistic analysis of how DNA structural distortions induced by platinum damage may inhibit RNA synthesis in vivo. A thorough understanding of the molecular mechanism of action of platinum antitumor agents will aid in the development of new compounds in the family.

Platinum drug adduct formation in the nucleosome core alters nucleosome mobility but not positioning

Nucleosome positioning and reorganization regulate DNA site exposure in chromatin. Platinum anticancer agents form DNA adducts that disrupt nuclear activities, triggering apoptosis. Mechanistic insight would aid in the development of improved therapies to circumvent drug toxicity and resistance. We show that platinum adducts formed by reaction of cisplatin or oxaliplatin with the nucleosome core inhibit histone octamer-DNA sliding but do not cause significant alteration of positioning. Thus, adduct formation reinforces positional preferences intrinsic to the DNA sequence, which indicates that modulation of platinum drug site selectivity by histone octamer association may relate to nucleosome-specific properties of DNA. This sheds light on platinum drug-mediated inhibition of chromatin remodeling in vivo and suggests that adducts can shield their own repair and interfere with genomic activities by directly altering nucleosome dynamics.

The anti-tumour agent, cisplatin, and its clinically ineffective isomer, transplatin, produce unique gene expression profiles in human cells

Cisplatin is a DNA-damaging anti-cancer agent that is widely used to treat a range of tumour types. Despite its clinical success, cisplatin treatment is still associated with a number of dose-limiting toxic side effects. The purpose of this study was to clarify the molecular events that are important in the anti-tumour activity of cisplatin, using gene expression profiling techniques. Currently, our incomplete understanding of this drug's mechanism of action hinders the development of more efficient and less harmful cisplatin-based chemotherapeutics. In this study the effect of cisplatin on gene expression in human foreskin fibroblasts has been investigated using human 19K oligonucleotide microarrays. In addition its clinically inactive isomer, transplatin, was also tested. Dualfluor microarray experiments comparing treated and untreated cells were performed in quadruplicate. Cisplatin treatment was shown to significantly up- or down-regulate a consistent subset of genes. Many of these genes responded similarly to treatment with transplatin, the therapeutically inactive isomer of cisplatin. However, a smaller proportion of these transcripts underwent differential expression changes in response to the two isomers. Some of these genes may constitute part of the DNA damage response induced by cisplatin that is critical for its anti-tumour activity. Ultimately, the identification of gene expression responses unique to clinically active compounds, like cisplatin, could thus greatly benefit the design and development of improved chemotherapeutics.

A fluorine containing bipyridine cisplatin analog is more effective than cisplatin at inducing apoptosis in cancer cell lines

Novel cisplatin analogs dichloro[4,4'-bis(4,4,4-trifluorobutyl)-2,2'-bipyridine]platinum (1) and fac-tricarbonylchloro[4,4'-bis(4,4,4-trifluorobutyl)-2,2'-bipyridine]rhenium (3) were synthesized and evaluated for their cytotoxicity. While 3 was not cytotoxic, 1 was 14 to 125 times more lethal than cisplatin in breast, prostate, and lung cancer cell lines. Compound 1 was able to induce apoptosis and the presence of the platinum atom was essential to its function as a cytotoxin.

More pronounced salt dependence and higher reactivity for platination of the hairpin r(CGCGUUGUUCGCG) compared with d(CGCGTTGTTCGCG)

The DNA interference pathways exhibited by cisplatin and related anticancer active metal complexes have been extensively studied. Much less is known to what extent RNA interaction pathways may operate in parallel, and perhaps contribute to both antineoplastic activity and toxicity. The present study was designed with the aim of comparing the reactivity of two model systems comprising RNA and DNA hairpins, r(CGCGUUGUUCGCG) and d(CGCGTTGTTCGCG), towards a series of platinum(II) complexes. Three platinum complexes were used as metallation reagents; cis-[PtCl(NH3)2(OH2)]+ (1), cis-[PtCl(NH3)(c-C6H11NH2)(OH2)]+ (2), and trans-[PtCl(NH3)(quinoline)(OH2)]+ (3). The reaction kinetics were studied at pH 6.0, 25 degrees C, and 1.0 mM < or = I < or = 500 mM. For both types of nucleic acid targets, compound 3 was found to react about 1 order of magnitude more rapidly than compounds 1 and 2. Further, all platinum compounds exhibited a more pronounced salt dependence for the interaction with r(CGCGUUGUUCGCG). Chemical and enzymatic cleavage studies revealed similar interaction patterns with r(CGCGUUGUUCGCG) after long exposure times to 1 and 2. A substantial decrease of cleavage intensity was found at residues G4 and G7, indicative of bifunctional adduct formation. Circular dichroism studies showed that platinum adduct formation leads to a structural change of the ribonucleic acid. Thermal denaturation studies revealed platination to cause a decrease of the RNA melting temperatures by 5-10 degrees C. Our observations therefore suggest that RNA is a kinetically competitive target to DNA. Furthermore, platination causes destabilization of RNA structural elements, which may lead to deleterious intracellular effects on biologically relevant RNA targets.

Kinetic preference for interaction of cisplatin with the G–C-rich wobble basepair region in both tRNAAlaand MhAla

The anticancer active complex cisplatin interacts preferentially with the common, G-C rich, wobble base pair region of both tRNA(Ala) and Mh(Ala) in a reaction that at pH 6.3 is rate limited by the acid hydrolysis of the metal complex.

Cellular processing of platinum anticancer drugs

Cisplatin, carboplatin and oxaliplatin are platinum-based drugs that are widely used in cancer chemotherapy. Platinum-DNA adducts, which are formed following uptake of the drug into the nucleus of cells, activate several cellular processes that mediate the cytotoxicity of these platinum drugs. This review focuses on recently discovered cellular pathways that are activated in response to cisplatin, including those involved in regulating drug uptake, the signalling of DNA damage, cell-cycle checkpoints and arrest, DNA repair and cell death. Such knowledge of the cellular processing of cisplatin adducts with DNA provides valuable clues for the rational design of more efficient platinum-based drugs as well as the development of new therapeutic strategies.

Effect of cisplatin treatment on speckled distribution of a serine/arginine-rich nuclear protein CROP/Luc7A

The C-half of cisplatin resistance-associated overexpressed protein (CROP), an SR-related protein, comprises domains rich in arginine and glutamate residues (RE domain), and is rich in arginine and serine residues (RS domain). We analyzed the role of the individual domains of CROP in cellular localization, subnuclear localization, and protein-protein interaction. CROP fused with green fluorescent protein, GFP-CROP, localized exclusively to the nucleus and showed a speckled intranuclear distribution. The yeast two-hybrid system revealed that CROP interacted with SF2/ASF, an SR protein involved in RNA splicing, as well as CROP itself. The RE and RS domains were necessary for both the intranuclear speckled distribution and the protein-protein interaction. CROP was phosphorylated by mSRPK1, mSRPK2, and Clk1 in vitro, and when cells were treated with cisplatin the subnuclear distribution of GFP-CROP was changed. These results suggest that cisplatin affects RNA splicing by changing the subnuclear distribution of SR proteins including CROP.

Cisplatin-induced apoptosis in 43-3B and 27-1 cells defective in nucleotide excision repair

Cisplatin is a highly potent cytotoxic and genotoxic agent used in the chemotherapy of various types of tumors. Its cytotoxic effect is supposed to be due to the induction of intra- and interstrand DNA cross-links which are repaired via the nucleotide excision repair (NER) pathway. Here, we elucidated the mechanism of cisplatin-induced cytotoxicity in mutants derived from CHO-9 cells defective in NER. We compared 43-3B and 27-1 cells deficient for ERCC1 and ERCC3, respectively, with the corresponding wild-type and ERCC1 complemented 43-3B cells. It is shown that cells defective in ERCC1 are more sensitive than cells defective in ERCC3 with regard to cisplatin-induced reproductive cell death. ERCC1 and ERCC3 mutants showed a higher frequency of apoptosis and, to a lesser degree, necrosis compared to repair proficient cells. Induction of apoptosis in both ERCC1 and ERCC3 defective cells was accompanied by decline in Bcl-2 protein level, activation of caspases 8, 9 and 3 and poly(ADP-ribose)polymerase (PARP) cleavage. Since the mutant cells are defective in the repair of cisplatin-induced DNA lesions, the data demonstrate that non-repaired cisplatin-induced DNA adducts act as a trigger of the mitochondrial apoptotic pathway by down-regulation of Bcl-2 followed by caspase activation.

Evidence for epidermal growth factor receptor-enhanced chemosensitivity in combinations of cisplatin and the new irreversible tyrosine kinase inhibitor CI-1033

Irreversible inhibitors of the epidermal growth factor receptor (EGFR) are showing promise in clinical trials. This report is the first to show that inhibition of the EGFR tyrosine kinase by an irreversible binder synergizes with cisplatin, at least in EGFR-overexpressing tissue culture cell lines in vitro. Unlike previous synergies demonstrated between ErbB2 blockade and DNA-damaging drugs, the synergy between the irreversible EGFR inhibitor and cisplatin does not appear to involve the repair of DNA-cisplatin adducts. Given the current clinical data, this combination may be of more than theoretical interest.

Functional modulation of the mineralocorticoid receptor by cis-diamminedichloroplatinum (II)

BACKGROUND

Renal salt wasting and hypotension are some of the frequent complications in patients treated with cis-diamminedichloroplatinum (II) (cDDP), and it is suggested that cDDP produces an abnormality in the renin-angiotensin system. However, not only the underlying mechanism but also prophylactic treatment of this cDDP toxicity remains unknown. In the present study, we investigated the molecular mechanism of this cDDP-induced disturbance of renal sodium handling with focusing on the effect of cDDP on mineralocorticoid receptor (MR) function.

METHODS

The effect of cDDP was studied on nuclear translocation, DNA binding activity, and transactivation function of the MR.

RESULTS

In a transient transfection assay, cDDP suppressed MR-dependent reporter gene expression. This cDDP-mediated repression of MR function, at least in part, is suggested to be due to the generation of reactive oxygen species and a subsequent decrease in ligand-dependent nuclear translocation and suppression of the interaction with DNA of the MR. This redox-dependent repression of MR function both in vitro and in vivo was reversed by treatment with reducing reagents. Moreover, cDDP, most possibly via formation of DNA adducts, inhibited MR-DNA interaction in a redox-independent fashion.

CONCLUSIONS

MR function is impaired by cDDP at multiple levels, via redox-dependent and -independent mechanisms.

Induction of erythroid differentiation of human K562 cells by cisplatin analogs

Human leukemic K562 cells can be induced in vitro to erythroid differentiation by a variety of chemical compounds, including hemin, butyric acid, 5-azacytidine, and cytosine arabinoside. Differentiation of K562 cells is associated with an increase in the expression of embryo-fetal globin genes, such as the zeta-, epsilon-, and gamma-globin genes. Therefore, the K562 cell line has been proposed as a very useful in vitro model system for determining the therapeutic potential of new differentiating compounds as well as for studying the molecular mechanism(s) regulating changes in the expression of embryonic and fetal human globin genes. Inducers of erythroid differentiation that stimulate gamma-globin synthesis could be considered for possible use in the experimental therapy of hematological diseases associated with a failure in the expression of adult beta-globin genes. In this paper, we analyzed the effects of a series of cisplatin analogs on both cell growth and differentiation of K562 cells. Among seven cisplatin analogs studied, three were found to be potent inducers of erythroid differentiation. Erythroid differentiation was associated with an increase in the accumulation of (a) hemoglobins Gower 1 and Portland and (b) gamma-globin mRNA.

CROP/Luc7A, a novel serine/arginine-rich nuclear protein, isolated from cisplatin-resistant cell line

A novel putative SR protein, designated cisplatin resistance-associated overexpressed protein (CROP), has been cloned from cisplatin-resistant cell lines by differential display. The N-half of the deduced amino acid sequence of 432 amino acids of CROP contains cysteine/histidine motifs and leucine zipper-like repeats. The C-half consists mostly of charged and polar amino acids: arginine (58 residues or 25%), glutamate (36 residues or 16%), serine (35 residues or 15%), lysine (30 residues, 13%), and aspartate (20 residues or 9%). The C-half is extremely hydrophilic and comprises domains rich in lysine and glutamate residues, rich in alternating arginine and glutamate residues, and rich in arginine and serine residues. The arginine/serine-rich domain is dominated by a series of 8 amino acid imperfect repetitive motif (consensus sequence, Ser-Arg-Ser-Arg-Asp/Glu-Arg-Arg-Arg), which has been found in RNA splicing factors. The RNase protection assay and Western blotting analysis indicate that the expression of CROP is about 2-3-fold higher in mRNA and protein levels in cisplatin-resistant ACHN/CDDP cells than in host ACHN cells. CROP is the human homologue of yeast Luc7p, which is supposed to be involved in 5'-splice site recognition and is essential for vegetative growth.

Constitutive mdmx expression during cell growth, differentiation, and DNA damage

The mdmx gene was shown to possess high homology to the mdm-2 gene and to encode a protein that can bind p53 and block p53 transactivation. Because Mdm-2 protein blocks the growth-suppressive activity of the p53 tumor-suppressor protein through similar activities, we examined the expression patterns of mdmx to determine how MdmX expression correlates with p53 protein levels. In this study, the expression pattern and protein levels of mdmx were examined in a number of cell culture systems. Like mdm-2, mdmx gene expression was constitutive during serum deprivation/restimulation of murine fibroblasts and differentiation of either murine teratocarcinoma or preadipocyte cells. In contrast, whereas mdm-2 gene expression was induced after cisplatin damage to ovarian carcinoma cells, mdmx expression remained constitutive. Because p53 transactivation is critical following a genotoxic stress, we examined p53:MdmX complexes after in vitro DNA-PK phosphorylation, a posttranslational modification that blocks p53 association with Mdm-2. The DNA-PK phosphorylation of p53 was capable of inhibiting p53:MdmX association. Thus, whereas DNA damage does not regulate mdmx mRNA levels, posttranslational modifications induced during DNA damage may block p53:MdmX association in vivo. These results demonstrate that, in the cell lines examined, mdmx gene expression remains constitutive during cell proliferation and differentiation or following DNA damage. Taken together, the data suggest that cells retain a constant level of MdmX. Thus, in undamaged cells, there exists the potential for an MdmX:p53 reservoir.

Proteins that specifically recognize cisplatin-damaged DNA: a clue to anticancer activity of cisplatin

Cisplatin, but not its trans geometric isomer, is a potent anticancer drug whose biological activity is a consequence of the formation of covalent adducts between the platinum compound and certain bases in DNA. Two classes of proteins have recently been identified that bind preferentially to damaged sites: proteins that specifically recognize those sites as a first step in their repair, and those that bind to such sites by virtue of structural similarity between the modified DNA and their own natural binding sites. Both classes of proteins may be involved, perhaps in opposing ways, in the cytotoxic effect of the drug.

Cisplatin inhibits synthesis of ribosomal RNA in vivo

Cis -diammininedichloroplatinum(II) (cisplatin or cis -DDP) is a DNA-damaging agent that is widely used in cancer chemotherapy. Cisplatin crosslinks DNA and the resulting adducts interact with proteins that contain high-mobility-group (HMG) domains, such as UBF(upstream binding factor). UBF is a transcription factor that binds to the promoter of ribosomal RNA (rRNA) genes thereby supporting initiation of transcription by RNA polymerase I. Here we report that cisplatin causes a redistribution of UBF in the nucleolus of human cells, similar to that observed after inhibition of rRNA synthesis. A similar redistribution was observed for the major components of the rRNA transcription machinery, namely TBP, TAFIs and RNA polymerase I. Furthermore, we provide for the first time direct in vivo evidence that cisplatin blocks synthesis of rRNA, while activity of RNA polymerase II continues to be detected throughout the nucleus. The clinically ineffective trans isomer (trans -DDP) does not alter the localization of either UBF or other components of the RNA polymerase I transcription machinery. These results suggest that disruption of rRNA synthesis, which is stimulated in proliferating cells, plays an important role in the clinical success of cisplatin.