Cytotoxic efficacy of an anthraquinone linked platinum anticancer drug

Platinum nanoparticles in cancer therapy: chemotherapeutic enhancement and ROS generation

Platinum nanoparticles (PtNPs) offer significant promise in cancer therapy by enhancing the therapeutic effects of platinum-based chemotherapies like cisplatin. These nanoparticles improve tumor targeting, reduce off-target effects, and help overcome drug resistance. PtNPs exert their anti-cancer effects primarily through the generation of reactive oxygen species (ROS), which induce oxidative stress and apoptosis in cancer cells. Additionally, PtNPs interact with cellular signaling pathways such as PI3K/AKT and MAPK, sensitizing cancer cells to chemotherapy. Advances in PtNP synthesis focus on optimizing size, shape, and surface modifications to enhance biocompatibility and targeting. Functionalization with biomolecules allows selective tumor delivery, while smart release systems enable controlled drug release. In vivo studies have shown that PtNPs significantly inhibit tumor growth and metastasis. Ongoing clinical trials are evaluating their safety and efficacy. This review explores PtNPs' mechanisms of action, nanotechnology advancements, and challenges in biocompatibility, with a focus on their potential integration into cancer treatments.

Aloe-Emodin Isolated from Rheum Undulatum L. Regulates Cell Cycle Distribution and Cellular Senescence in Human Prostate Cancer LNCaP Cells

Senescence can promote hyperplastic pathologies, such as cancer. Prostate cancer is the second most common type of cancer in men. The p21-mediate cellular senescence, facilitated through the tumor suppressor p53-dependent pathway, is considered the primary mechanism for cancer treatment. Aloe-emodin, has been reported to exert anticancer effects in various types of cancers. This study aimed to investigate the bioactivity of aloe-emodin in LNCaP cells via the activation of p21-mediated cellular senescence. Aloe-emodin treatment increased the percentage of cells in the G1 phase while decreasing the percentage in the S phase. This effect was reflected in the expression levels of proteins associated with cell cycle progression, such as p21CIP, retinoblastoma protein, and cyclin-dependent kinase2/4 in LNCaP cells. However, aloe-emodin-treated LNCaP cells did not induce cell cycle arrest at G2/M checkpoint. Moreover, increased senescence-associated-galactosidase activity was observed in a dose-dependent manner following treatment with aloe-emodin. Aloe-emodin also induced DNA damage by modulating the expression of histone H2AX and lamin B1. Furthermore, aloe-emodin inhibited the proliferation of LNCaP cells, contrasting with the exponential growth observed in the nontreated cells. Importantly, this inhibition did not impact the immune system, as evidenced by the increased proliferation of splenocytes isolated from mice. These findings provide preliminary evidence of the anticancer effect of aloe-emodin in LNCaP cells, necessitating further investigations into the underlying mechanisms in vivo and human subjects.

Photosensitization of a subcutaneous tumour by the natural anthraquinone parietin and blue light

Photodynamic therapy (PDT) is an anticancer treatment involving administration of a tumour-localizing photosensitizer, followed by activation by light of a suitable wavelength. In previous work, we showed that the natural anthraquinone (AQ) Parietin (PTN), was a promising photosensitizer for photodynamic therapy of leukemic cells in vitro. The present work aimed to analyze the photosensitizing ability of PTN in the mammary carcinoma LM2 cells in vitro and in vivo in a model of subcutaneously implanted tumours. Photodynamic therapy mediated by parietin (PTN-PDT) (PTN 30 µM, 1 h and 1.78 J/cm² of blue light) impaired cell growth and migration of LM2 cells in vitro. PTN per se induced a significant decrease in cell migration, and it was even more marked after illumination (migration index was 0.65 for PTN and 0.30 for PTN-PDT, *p < 0.0001, ANOVA test followed by Tukey's multiple comparisons test), suggesting that both PTN and PTN-PDT would be potential inhibitors of metastasis. Fluorescence microscopy observation indicated cytoplasmic localization of the AQ and no fluorescence at all was recorded in the nuclei. When PTN (1.96 mg) dissolved in dimethyl sulfoxide was topically applied on the skin of mice subcutaneously implanted with LM2 cells, PTN orange fluorescence was strongly noticed in the stratum corneum and also in the inner layers of the tumour up to approximately 5 mm. After illumination with 12.74 J/cm² of blue light, one PDT dose at day 1, induced a significant tumour growth delay at day 3, which was not maintained in time. Therefore, we administered a second PTN-PDT boost on day 3. Under these conditions, the delay of tumour growth was 28% both on days 3 and 4 of the experiment (*p < 0.05 control vs. PTN-PDT, two-way ANOVA, followed by Sidak's multiple comparisons test). Histology of tumours revealed massive tumour necrosis up to 4 mm of depth. Intriguingly, a superficial area of viable tumour in the 1 mm superficial area, and a quite conserved intact skin was evidenced. We hypothesize that this may be due to PTN aggregation in contact with the skin and tumour milieu of the most superficial tumour layers, thus avoiding its photochemical properties. On the other hand, normal skin treated with PTN-PDT exhibited slight histological changes. These preliminary findings encourage further studies of natural AQs administered in different vehicles, for topical treatment of cutaneous malignancies.

Novel polyamide amidine anthraquinone platinum(II) complexes: cytotoxicity, cellular accumulation, and fluorescence distributions in 2D and 3D cell culture models

1- and 1,5-Aminoalkylamine substituted anthraquinones (AAQs, 1C3 and 1,5C3) were peptide coupled to 1-, 2-, and 3-pyrrole lexitropsins to generate compounds that incorporated both DNA minor groove and intercalating moieties. The corresponding platinum(II) amidine complexes were synthesized through a synthetically facile amine-to-platinum mediated nitrile 'Click' reaction. The precursors as well as the corresponding platinum(II) complexes were biologically evaluated in 2D monolayer cells and 3D tumour cell models. Despite having cellular accumulation levels that were up to five-fold lower than that of cisplatin, the platinum complexes had cytotoxicities that were only three-fold lower. Accumulation was lowest for the complexes with two or three pyrrole groups, but the latter was the most active of the complexes exceeding the activity of cisplatin in the MDA-MB-231 cell line. All compounds showed moderate to good penetration into spheroids of DLD-1 cells with the distributions being consistent with active uptake of the pyrrole containing complexes in regions of the spheroids starved of nutrients.

Assisted delivery of anti-tumour platinum drugs using DNA-coiling gold nanoparticles bearing lumophores and intercalators: towards a new generation of multimodal nanocarriers with enhanced action

New gold and lipoic based nanocarriers for the delivery of platinum(ii) and platinum(iv) drugs are developed, which allow enhanced loading of the drug on the surface of the nanocarriers and release in a pH-dependent fashion, with superior release at lower pHs which are associated with many tumours. The conjugate nanoparticles and their conjugates enter cells rapidly (within 3 hours). They tend to cluster in vesicles and are also observed by light and electron microscopies in the cytoplasm, endoplasmic reticulum and nucleus. We further incorporate aminoanthraquinone units that are both fluorophores and DNA intercalators. This results in nanocarriers that after drug release will remain surface decorated with DNA-binders challenging the conventional design of the nanocarrier as an inert component. The outcome is nanocarriers that themselves have distinctive, remarkable and unusual DNA binding properties being able to bind and wrap DNA (despite their anionic charge) and provide enhanced cytotoxic activity beyond that conferred by the platinum agents they release. DNA coiling is usually associated with polycations which can disrupt cell membranes; anionic nanoparticles that can cause novel and dramatic effects on DNA may have fascinating potential for new approaches to in-cell nucleic acid recognition. Our findings have implications for the understanding and interpretation of the biological activities of nanoparticles used to deliver other DNA-binding drugs including clinical drug doxorubicin and its formulations.

Reshaping the Energy Landscape Transforms the Mechanism and Binding Kinetics of DNA Threading Intercalation

Molecules that bind DNA via threading intercalation show high binding affinity as well as slow dissociation kinetics, properties ideal for the development of anticancer drugs. To this end, it is critical to identify the specific molecular characteristics of threading intercalators that result in optimal DNA interactions. Using single-molecule techniques, we quantify the binding of a small metal-organic ruthenium threading intercalator (Δ,Δ-B) and compare its binding characteristics to a similar molecule with significantly larger threading moieties (Δ,Δ-P). The binding affinities of the two molecules are the same, while comparison of the binding kinetics reveals significantly faster kinetics for Δ,Δ-B. However, the kinetics is still much slower than that observed for conventional intercalators. Comparison of the two threading intercalators shows that the binding affinity is modulated independently by the intercalating section and the binding kinetics is modulated by the threading moiety. In order to thread DNA, Δ,Δ-P requires a "lock mechanism", in which a large length increase of the DNA duplex is required for both association and dissociation. In contrast, measurements of the force-dependent binding kinetics show that Δ,Δ-B requires a large DNA length increase for association but no length increase for dissociation from DNA. This contrasts strongly with conventional intercalators, for which almost no DNA length change is required for association but a large DNA length change must occur for dissociation. This result illustrates the fundamentally different mechanism of threading intercalation compared with conventional intercalation and will pave the way for the rational design of therapeutic drugs based on DNA threading intercalation.

Multi-scale imaging of anticancer platinum(iv) compounds in murine tumor and kidney

Nano-scale secondary ion mass spectrometry (NanoSIMS) enables trace element and isotope analyses with high spatial resolution. This unique capability has recently been exploited in several studies analyzing the subcellular distribution of Au and Pt anticancer compounds. However, these studies were restricted to cell culture systems. To explore the applicability to the in vivo setting, we developed a combined imaging approach consisting of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), NanoSIMS and transmission electron microscopy (TEM) suitable for multi-scale detection of the platinum distribution in tissues. Applying this approach to kidney and tumor samples upon administration of selected platinum(iv) anticancer prodrugs revealed uneven platinum distributions on both the organ and subcellular scales. Spatial platinum accumulation patterns were quantitatively assessed by LA-ICP-MS in histologically heterogeneous organs (e.g., higher platinum accumulation in kidney cortex than in medulla) and used to select regions of interest for subcellular-scale imaging with NanoSIMS. These analyses revealed cytoplasmic sulfur-rich organelles accumulating platinum in both kidney and malignant cells. Those in the tumor were subsequently identified as organelles of lysosomal origin, demonstrating the potential of the combinatorial approach for investigating therapeutically relevant drug concentrations on a submicrometer scale.

Structure-activity relationship studies on rhodamine B-based fluorogenic probes and their activation by anticancer platinum(II) compounds

Fluorescence microscopy has emerged as an attractive technique for imaging intracellular Pt species arising from exposure to clinical anticancer drugs such as cisplatin. A rhodamine-B based fluorogenic probe termed Rho-DDTC can be activated selectively in the presence of Pt(II) compounds, and possesses the ability to discriminate Pt(II) species from Pt(IV) carboxylate prodrug complexes, thereby providing a unique platform to investigate the reduction of these Pt(IV) complexes after cell entry. In this report, we seek to establish the mechanism of activation of Rho-DDTC through a structure-activity relationship study on its structural analogues.

Fibrillarin from Archaea to human

Fibrillarin is an essential protein that is well known as a molecular marker of transcriptionally active RNA polymerase I. Fibrillarin methyltransferase activity is the primary known source of methylation for more than 100 methylated sites involved in the first steps of preribosomal processing and required for structural ribosome stability. High expression levels of fibrillarin have been observed in several types of cancer cells, particularly when p53 levels are reduced, because p53 is a direct negative regulator of fibrillarin transcription. Here, we show fibrillarin domain conservation, structure and interacting molecules in different cellular processes as well as with several viral proteins during virus infection.

Lysosomal targeting with stable and sensitive fluorescent probes (Superior LysoProbes): applications for lysosome labeling and tracking during apoptosis

Intracellular pH plays an important role in the response to cancer invasion. We have designed and synthesized a series of new fluorescent probes (Superior LysoProbes) with the capacity to label acidic organelles and monitor lysosomal pH. Unlike commercially available fluorescent dyes, Superior LysoProbes are lysosome-specific and are highly stable. The use of Superior LysoProbes facilitates the direct visualization of the lysosomal response to lobaplatin elicited in human chloangiocarcinoma (CCA) RBE cells, using confocal laser scanning microscopy. Additionally, we have characterized the role of lysosomes in autophagy, the correlation between lysosome function and microtubule strength, and the alteration of lysosomal morphology during apoptosis. Our findings indicate that Superior LysoProbes offer numerous advantages over previous reagents to examine the intracellular activities of lysosomes.

MDR1 and cytochrome P450 gene-expression profiles as markers of chemosensitivity in human chronic myelogenous leukemia cells treated with cisplatin and Ru(III) metallocomplexes

Leukemia is a major type of cancer affecting a significant segment of the population, and especially children. In fact, leukemia is the most frequent childhood cancer, with 26 % of all cases, and 20 % mortality. The multidrug resistance phenotype (MDR) is considered one of the major causes of failure in cancer chemotherapy. The present study aimed to investigate the relationship between the expression of MDR1 and CYP450 genes in human chronic myelogenous leukemia cells (K-562) treated with cisplatin (cisPt) and two ruthenium-based coordinated complexes [cisCRu(III) and cisDRu(III)]. The tested compounds induced apoptosis in K-562 tumor cells as evidenced by caspase 3 activation. Results also revealed that the amplification of P-gp gene is greater in K-562 cells exposed to cisPt and cisCRu(III) than cisDRu(III). Taken together, all these results strongly demonstrate that MDR-1 overexpression in K-562 cells could be associated to a MDR phenotype, and moreover, it is also contributing to the platinum and structurally related compound, resistance in these cells.

Fluorescent sensing of monofunctional platinum species

A fluorescein derivative exhibits increased fluorescence selectively in response to monofunctional platinum complexes, and can be used to study the metabolism of platinum-based chemotherapeutics.

Investigation of the pharmacological profiles of dinuclear metal complexes as novel, potent and selective cytotoxic agents against ras-transformed cells

Around the world scientists try to design successful cures against still incurable diseases, especially cancers. New targets for prevention and new agents for therapy need to be identified. We synthesized novel metal complexes [Au(L1)(L2)Pt]Cl2 and [Ru(L1)2(L2)Pt]Cl2 for determining their cytotoxic and apoptotic effects. The complexes are synthesized by using 1,8-diaminonaphthalene (L1), and bis-1,4-di[([1,10]phenanthroline-5-il)aminomethyl]cyclohexane (L2) as ligands. This is the first study to examine these metals and these molecules in cancer treatment. We elucidated the effects of test compounds with embryonic rat fibroblast-like cells (F2408) and H-ras oncogene activated embryonic rat fibroblast-like cancer cells (5RP7). Results showed that our complexes are more effective than cisplatin to kill ras-transformed cells. Although the [Au(L1)(L2)Pt]Cl2 compound showed a cytotoxic potency higher than [Ru(L1)2(L2)Pt]Cl2 against cancer cells, it proved to be almost five times less effective in decreasing cell viability over healthy cells. Au(III) compound selectively targets the cancer cells but not the healthy cells.

Design, modeling, synthesis and biological activity evaluation of camptothecin-linked platinum anticancer agents

The design, modeling, synthesis and biological activity evaluation of two hybrid agents formed by 7-oxyiminomethylcamptothecin derivatives and diaminedichloro-platinum (II) complex are reported. The compounds showed growth inhibitory activity against a panel of human tumor cell lines, including sublines resistant to topotecan and platinum compounds. The derivatives were active in all the tested cell lines, and compound 1b, the most active one, was able to overcome cisplatin resistance in the osteosarcoma U2OS/Pt cell line. Platinum-containing camptothecins produced platinum-DNA adducts and topoisomerase I-mediated DNA damage with cleavage pattern and persistence similar to SN38, the active principle of irinotecan. Compound 1b exhibited an appreciable antitumor activity in vivo against human H460 tumor xenograft, comparable to that of irinotecan at lower well-tolerated dose levels and superior to cisplatin. The results support the interpretation that the diaminedichloro-platinum (II) complex conjugated via an oxyiminomethyl linker at the 7-position of the camptothecin resulted in a new class of effective antitumor compounds.

Facile preparation of mono-, di- and mixed-carboxylato platinum(IV) complexes for versatile anticancer prodrug design

Facile strategies were developed for the versatile functionalization of platinum(IV) axial sites, allowing for easy accessibility to unsymmetric mono- and mixed-carboxylato, as well as symmetric di-substituted platinum(IV) complexes. The first method involves the direct oxidation and carboxylation of the platinum(II) center using an appropriate peroxide and the carboxylate of choice to firstly yield a monocarboxylato monohydroxido platinum(IV) complex. This platinum(IV) intermediate can undergo further carboxylation to give rise to a mixed-carboxylato platinum(IV) complex. The second method involves the activation of the carboxylate of choice by a common carbodiimide coupling reagent, and its reaction with a dihydroxido platinum(IV) precursor to give the monocarboxylato platinum(IV) complex. Uronium salts can be employed to promote efficient dicarboxylation of the dihydroxido platinum(IV) precursor. Lastly, an axial azide pendant group was demonstrated to be suitable for orthogonal "click" conjugation reactions.

Anticancer metallodrug research analytically painting the "omics" picture--current developments and future trends

Anticancer metallodrug development has for a long time been characterised by the similarity of new drug candidates to cisplatin and DNA as the primary target. Recent advances in bioanalytical techniques with high sensitivity and selectivity have revealed that metal-based drugs can undergo a wide range of biomolecular interactions beyond DNA and have generated interest in proteins as possible targets for metallodrugs. In fact, implementation of metallomics approaches that are able to reveal the fate of the compounds in biological systems can help to move drug development towards more targeted and rational design of novel metallodrugs. Additionally, proteomic screening and gene expression analysis can provide insight into physiological response to drug treatment and identify the reasons for drug resistance. Herein, we review selected applications which led to a better understanding of the mode of action of clinically established metal-based anticancer agents and novel metallodrug candidates.

Synthesis and biological studies of pyrazolyl-diamine Pt(II) complexes containing polyaromatic DNA-binding groups

New [PtCl(pz*NN)](n+) complexes anchored by pyrazolyl-diamine (pz*NN) ligands incorporating anthracenyl or acridine orange DNA-binding groups have been synthesized so as to obtain compounds that would display synergistic effects between platination and intercalation of DNA. Study of their interaction with supercoiled DNA indicated that the anthracenyl-containing complex L(2) Pt displays a covalent type of binding, whereas the acridine orange counterpart L(3) Pt shows a combination of intercalative and covalent binding modes with a strong contribution from the former. L(2) Pt showed a very strong cytotoxic effect on ovarian carcinoma cell lines A2780 and A2780cisR, which are, respectively, sensitive to and resistant to cisplatin. In these cell lines, L(2) Pt is nine to 27 times more cytotoxic than cisplatin. In the sensitive cell line, L(3) Pt showed a cytotoxic activity similar to that of cisplatin, but like L(2) Pt was able significantly to overcome cisplatin cross-resistance. Cell-uptake studies showed that L(2) Pt accumulates preferentially in the cytoplasm, whereas L(3) Pt reaches the cell nucleus more easily, as clearly visualized by time-lapse confocal imaging of live A2870 cells. Altogether, these findings seem to indicate that interaction with biological targets other than DNA might be involved in the mechanism of action of L(2) Pt because this compound, despite having a weaker ability to target the cell nucleus than L(3) Pt, as well as an inferior DNA affinity, is nevertheless more cytotoxic. Furthermore, ultrastructural studies of A2870 cells exposed to L(2) Pt and L(3) Pt revealed that these complexes induce different alterations in cell morphology, thus indicating the involvement of different modes of action in cell death.

Synthesis of amphiphilic polythiophene for cell imaging and monitoring the cellular distribution of a cisplatin anticancer drug

A new amphiphilic conjugated polythiophene derivative (PT-Boc) is synthesized via Suzuki coupling reaction. The amphiphilic characteristic makes it form nanoaggregates in water, in which hydrophobic moieties come together to form the inner core. The polymer shows good photostability and no toxicity to human lung epithelial (A549) cells even at a high concentration (100 μg mL(-1) ). It therefore meets the crucial requirement for cellular imaging and other biological applications. The anticancer drug cisplatin is used as a model, and is linked to polythiophene to obtain a conjugate 'PT-Pt' by coordinated interactions between cisplatin and the amine groups of the polythiophene side chain. The PT-Pt can be used for monitoring the cellular distribution of cisplatin by fluorescence microscopy. The amphiphilic polythiophene provides a platform for fluorescent imaging of drugs and biological molecules in living cells.

Enhancing lipophilicity as a strategy to overcome resistance against platinum complexes?

Decreased influx represents one of the major resistance mechanisms of platinum complexes. In order to address the question if this mechanism of resistance can be overcome by enhancing the lipophilicity of platinum complexes, we investigated the influence of lipophilicity on cellular accumulation and cytotoxicity in a panel of oxaliplatin analogues with different carrier ligands. Cellular accumulation, DNA platination and cytotoxicity were measured in a cisplatin-sensitive and -resistant ovarian carcinoma (A2780/A2780cis) and in an oxaliplatin-sensitive and -resistant ileocecal colorectal adenocarcinoma (HCT-8/HCT-8ox) cell line pair. Platinum concentrations were determined by flameless atomic absorption spectrometry or adsorptive stripping voltammetry. Passive diffusion represented the main influx mechanism of oxaliplatin analogues during the first minutes of incubation as indicated by a correlation between lipophilicity and early influx rate. Afterwards, the predominant influx mechanism was lipophilicity-independent. More lipophilic complexes showed a reduced cytotoxic activity, although the early influx rate was increased. The resistance profiles of the two cell line pairs were found to be different: HCT-8ox cells were less resistant against more lipophilic complexes, whereas A2780cis cells exhibited a comparable degree of resistance against all investigated compounds. However, the reduction in resistance factor of HCT-8ox cells cannot be explained by increased influx suggesting that other resistance mechanisms are circumvented upon exposure to more lipophilic compounds. Though resistance against more lipophilic platinum complexes analogues is lower we conclude that enhancing lipophilicity is not a successful strategy to overcome platinum resistance as higher lipophilicity is also associated with lower cytotoxic activity.

Overexpression of biliverdin reductase enhances resistance to chemotherapeutics

Biliverdin reductase (BVR) converts biliverdin to bilirubin. Additionally, acting as a transcription factor and possessing a capacity of a serine/threonine kinase, it may modulate signaling pathways. In order to gain better understanding of BVR functions, we used genetically modified line of mouse fibroblasts with reversible overexpression of BVR. Current study revealed that enhanced activity of BVR may protect cells in stressful conditions arising from anti-cancer drugs, cisplatin and doxorubicin, the effect most probably related to PKC α/β activity, as its inhibition reversed BVR action. Therefore activity of BVR may be of significance in tumors and may influence the effectiveness of therapies.

Accumulation of an anthraquinone and its platinum complexes in cancer cell spheroids: the effect of charge on drug distribution in solid tumour models

The penetration of anthraquinones and their platinum complexes into cancer cell spheroids reveals that they model well the distribution of such compounds in solid tumours and that the proportion of the compound that accumulates deep in the spheroid is inversely related to the rate of cellular uptake which is affected by the charge of the compound.

Binding of [Pt(1C3)(dien)](2+) to the duplex DNA oligonucleotide 5'-d(TGGCCA)-3': the effect of an appended positive charge on the orientation and location of anthraquinone intercalation

The binding of a platinum intercalator complex [Pt(1C3)(dien)](2+) (1C3 = 1-[(3-aminopropyl)amino]-anthracene-9,10-dione, dien = 3-azapentane-1,5-diamine) to DNA and to the self-complementary oligonucleotide 5'-d(TGGCCA)-3' has been investigated by UV-visible spectrophotometry and 2D NMR spectroscopy, respectively. The uncomplexed anthraquinone, 1C3, has an apparent DNA binding constant of 1.4 x 10(4), similar to that of ethidium bromide. Addition of the coordinatively saturated {Pt(dien)} moiety increases the binding constant to 3.7 x 10(5) M(-1), showing the effect of the increased positive charge introduced by this moiety. Multiple binding modes are evident from the lack of isosbestic points in the titration spectra and the non-linear nature of the half-reciprocal plot used to calculate the binding constant. [Pt(1C3)(dien)](2+) forms a 2 : 1 adduct with 5'-d(TGGCCA)-3' and is shown by 2D NMR to intercalate primarily in the TG:CA base pairs at the ends of the oligonucleotide with the side chain and {Pt(dien)} situated in the minor groove.

The role of cellular accumulation in determining sensitivity to platinum-based chemotherapy

The platinum (Pt) drugs cisplatin and carboplatin are heavily employed in chemotherapy regimens; however, similar to other classes of drugs, a number of intrinsic and acquired resistance mechanisms hamper their effectiveness. The method by which Pt drugs enter cells has traditionally been attributed to simple passive diffusion. However, recent evidence suggests a number of active uptake and efflux mechanisms are at play, and altered regulation of these transporters is responsible for the reduced accumulation of drug in resistant cells. This review suggests a model that helps reconcile the disparate literature by describing multiple pathways for Pt-containing drugs into and out of the cell.

Antiproliferative, antioxidant, and antimutagenic activities of flavonoid-enriched extracts from (Tunisian) Rhamnus alaternus L.: combination with the phytochemical composition

A pronounced antiproliferative effect on human leukemia K562 cells was shown with flavonoid-enriched extracts from Rhamnus alaternus roots and leaves, with, respectively, IC(50) values of 165 and 210.73 microg/mL. High DPPH radical-scavenging activity (7.21 and 18.84 microg/mL, respectively) and antioxidative effects using the xanthine oxidase assay (IC(50) values of 83.33 and 103.96 microg/mL, respectively) were detected in the presence of the two tested extracts. Although no mutagenic effect was observed when using the Salmonella typhimurium assay system with TA1535 and TA100 strains, the two tested extracts exhibited a high-level protection toward the direct mutagen, sodium azide-induced response.