Pt(II) Complexes of a Combretastatin A-4 Analogous Chalcone: Effects of Conjugation on Cytotoxicity, Tumor Specificity, and Long-Term Tumor Growth Suppression

A review on synthetic chalcone derivatives as tubulin polymerisation inhibitors

Microtubules play an important role in the process of cell mitosis and can form a spindle in the mitotic prophase of the cell, which can pull chromosomes to the ends of the cell and then divide into two daughter cells to complete the process of mitosis. Tubulin inhibitors suppress cell proliferation by inhibiting microtubule dynamics and disrupting microtubule homeostasis. Thereby inducing a cell cycle arrest at the G2/M phase and interfering with the mitotic process. It has been found that a variety of chalcone derivatives can bind to microtubule proteins and disrupt the dynamic balance of microtubules, inhibit the proliferation of tumour cells, and exert anti-tumour effects. Consequently, a great number of studies have been conducted on chalcone derivatives targeting microtubule proteins. In this review, synthetic or natural chalcone microtubule inhibitors in recent years are described, along with their structure-activity relationship (SAR) for anticancer activity.

Chalcone Derivatives: Role in Anticancer Therapy

Chalcones (1,3-diaryl-2-propen-1-ones) are precursors for flavonoids and isoflavonoids, which are common simple chemical scaffolds found in many naturally occurring compounds. Many chalcone derivatives were also prepared due to their convenient synthesis. Chalcones as weandhetic analogues have attracted much interest due to their broad biological activities with clinical potentials against various diseases, particularly for antitumor activity. The chalcone family has demonstrated potential in vitro and in vivo activity against cancers via multiple mechanisms, including cell cycle disruption, autophagy regulation, apoptosis induction, and immunomodulatory and inflammatory mediators. It represents a promising strategy to develop chalcones as novel anticancer agents. In addition, the combination of chalcones and other therapies is expected to be an effective way to improve anticancer therapeutic efficacy. However, despite the encouraging results for their response to cancers observed in clinical studies, a full description of toxicity is required for their clinical use as safe drugs for the treatment of cancer. In this review, we will summarize the recent advances of the chalcone family as potential anticancer agents and the mechanisms of action. Besides, future applications and scope of the chalcone family toward the treatment and prevention of cancer are brought out.

Dual-target platinum(IV) complexes exhibit antiproliferative activity through DNA damage and induce ER-stress-mediated apoptosis in A549 cells

Platinum(II)-based chemotherapeutics are commonly used to treat various types of solid tumors, such as lung cancers. However, these compounds can cause serious side effects, including nephrotoxicity and ototoxicity, which affect the quality of life of patients. In our work, four novel dual target platinum(IV) complexes were designed and synthesized. In vitro results indicated that the title platinum(IV) complexes exhibited effective antitumor activities against the tested cancer cells and had lower toxicity and resistance factors than oxaliplatin and cisplatin. Further mechanistic experiments demonstrated that complex 11 accumulated in mitochondria and induced an elevation in ROS and an ER stress response via mitochondrial dysfunction. Notably, complex 11 significantly modulated the expression levels of proapoptosis proteins including cleaved-Caspase-3, Bax, and p53, and decreased the level of the prosurvival protein Bcl-2. Together, these results suggested that complex 11 might be a potential lead compound for future cancer therapy due to its potency and selectivity.

Novel diaryl-2H-azirines: Antitumor hybrids for dual-targeting tubulin and DNA

Multiple-target drugs may achieve better therapeutic effect via different pathways than single-target ones, especially for complex diseases. Tubulin and DNA are well-characterized molecular targets for anti-cancer drug development. A novel class of diaryl substituted 2H-azirines were designed based on combination of pharmacophores from Combretastatin A-4 (CA-4) and aziridine-type alkylating agents, which are known tubulin polymerization inhibitor and DNA damaging agents, respectively. The antitumor activities of these compounds were evaluated in vitro and 6h showed the most potent activities against four cancer cell lines with IC₅₀ values ranging from 0.16 to 1.40 μM. Further mechanistic studies revealed that 6h worked as a bifunctional agent targeting both tubulin and DNA. In the nude mice xenograft model, 6h significantly inhibited the tumor growth with low toxicity, demonstrating the promising potential for further developing novel cancer therapy with a unique mechanism.

Ni(ii), Cu(ii) and Zn(ii) complexes with the 1-trifluoroethoxyl-2,9,10-trimethoxy-7-oxoaporphine ligand simultaneously target microtubules and mitochondria for cancer therapy

Complexes 1–3 display potent anticancer activity against T-24 cell by disrupting mitochondria and microtubules. Furthermore, complex 1 exhibits almost same tumor growth inhibition activity in T-24 xenograft mouse model as cisplatin and paclitaxel.

Platinum(IV) complexes conjugated with chalcone analogs as dual targeting anticancer agents: In vitro and in vivo studies

For the sake to develop novel platinum(IV) complexes to reverse cisplatin (CDDP) resistence, four multifunctional platinum(IV) prodrugs via conjugating chalcones with the related platinum(IV) complexes derived from cisplatin were designed and evaluated for anti-tumor actyivities in vitro and in vivo. Among them, complex 9 exhibited excellent anticancer activities in vitro with IC₅₀ values at the submicromolar level against the tested human cancer cells, whereas showed low cytotoxicity towards human normal liver cells HL-7702. Further mechanistic studies indicated that complex 9 induced G2/M phase arrest and apoptosis in A549 cells, which was associated with a collapse of the mitochondrial membrane potential (MMP), alterations in the expression of some apoptosis-related proteins, and enhanced level of the intracellular reactive oxygen species (ROS). More importantly, complex 9 significantly suppressed the tumor growth in the A549 xenograft model without obvious hints of toxicity.

Novel chalcone derivatives containing a 1,2,4-triazine moiety: design, synthesis, antibacterial and antiviral activities

A series of novel chalcone derivatives containing the 1,2,4-triazine moiety were synthesized and their structures were confirmed by 1H NMR, 13C NMR and elemental analyses. Antiviral bioassays revealed that most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL-1. The designated compound 4l was 50% effective in terms of curative and protective activities against TMV with 50% effective concentrations (EC50) of 10.9 and 79.4 μg mL-1, which were better than those of ningnanmycin (81.4 and 82.2 μg mL-1). Microscale thermophoresis (MST) also showed that the binding of compound 4l to coat protein (TMV-CP) yielded a K d value of 0.275 ± 0.160 μmol L-1, which was better than that of ningnanmycin (0.523 ± 0.250 μmol L-1). At the same time, molecular docking studies for 4l with TMV-CP (PDB code:1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP. Meanwhile, compound 4a demonstrated excellent antibacterial activities against Ralstonia solanacearum (R. solanacearum), with an EC50 value of 0.1 μg mL-1, which was better than that of thiodiazole-copper (36.1 μg mL-1) and bismerthiazol (49.5 μg mL-1). The compounds act by causing folding and deformation of the bacterial cell membrane as observed using scanning electron microscopy (SEM). The chalcone derivatives thus synthesized could become potential alternative templates for novel antiviral and antibacterial agents.

Biological activity evaluation and action mechanism of chalcone derivatives containing thiophene sulfonate

A series of novel chalcone derivatives containing a thiophene sulfonate group were designed and synthesized. The structures of all title compounds were determined by ¹H-NMR, ¹³C-NMR and HRMS. Antibacterial bioassays indicated that, compound 2l demonstrated excellent antibacterial activities against Xanthomonas axonopodis pv. citri (Xac), with an EC₅₀ value of 11.4 μg mL⁻¹, which is significantly superior to those of bismerthiazol (BT) (51.6 μg mL⁻¹) and thiodiazole-copper (TC) (94.7 μg mL⁻¹). Meanwhile, the mechanism of action of compound 2l was confirmed by using scanning electron microscopy (SEM). In addition, compound 2e showed remarkable inactivation activity against Tobacco mosaic virus (TMV), with an EC₅₀ value of 44.3 μg mL⁻¹, which was superior to that of ningnanmycin (120.6 μg mL⁻¹). Microscale thermophoresis (MST) also showed that the binding of compounds 2e and 2h to Tobacco mosaic virus coat protein (TMV-CP) yielded K_d values of 0.270 and 0.301 μmol L⁻¹, which are better than that of ningnanmycin (0.596 μmol L⁻¹). At the same time, molecular docking studies for 2e and 2h with TMV-CP (PDB code: 1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP in each case. These results suggested that chalcone derivatives containing a thiophene sulfonate group may be considered as activators in the design of antibacterial and antiviral agents.

Synthesis, antibacterial, antiviral activities and action mechanism of chalcone derivatives containing thiophene sulfonate.

Therapeutic Potential of Nitrogen Mustard Based Hybrid Molecules

As medicine advances, cancer is still among one of the major health problems, posing significant threats to human health. New anticancer agents features with novel scaffolds and/or unique mechanisms of action are highly desirable for the treatment of cancers, especially those highly aggressive and drug-resistant ones. Nitrogen mustard has been widely used as an anticancer drug since the discovery of its antitumor effect in the 1942. However, the lack of selectivity to cancer cells restricts the wide usage of a mass of nitrogen mustard agents to achieve further clinical significance. Discovery of antitumor hybrids using nitrogen mustards as key functional groups has exhibited enormous potential in the drug development. Introduction of nitrogen mustards resulted in improvement in the activity, selectivity, targetability, safety, pharmacokinetics and pharmacodynamics properties of corresponding lead compounds or agents. Herein, the recently developed nitrogen mustard based hybrids have been introduced in the cancer therapy.

Pt(IV) prodrugs containing microtubule inhibitors displayed potent antitumor activity and ability to overcome cisplatin resistance

It is well-known that cisplatin exhibited a broad spectrum of anticancer activities against many solid tumors, but its severe toxicity and drug resistance have largely limited wider clinical applications. Various strategies have been tried to discover new Pt (II) drugs with at least equal activity as well as low toxicity compared to cisplatin, but the inherent problem remains unsolved. Here we report that Pt (IV) complexes comprising a CA-4 analogue, as dual-targeting Pt (IV) prodrug, were synthesized and evaluated for anti-proliferative activity using MTT assay. Among them, complex 19 displayed most potent activity against the tested cancer cell lines, and simultaneously exhibited better cell selectivity between cancer cells and normal cells than that of cisplatin. Mechanism studies revealed that complex 19 effectively induced cell cycle arrest at the G2/M phase and dramatically disrupted the microtubule organization. Moreover, complex 19 significantly induced cell apoptosis and decreased MMP. Importantly, complex 19 significantly inhibited tumor growth in SK-OV-3 xenograft model in vivo without apparent toxicity.

Metal Complexes of Natural Product Like-compounds with Antitumor Activity

Cancer continues to be one of the major causes of death worldwide. Despite many advances in the understanding of this complex disease, new approaches are needed to improve the efficacy of current therapeutic treatments against aggressive tumors. Natural products are one of the most consistently successful sources of drug leads. In recent decades, research activity into the clinical potential of this class of compounds in cancer has increased. Furthermore, a highly promising field is the use of metals and their complexes in the design and development of metal-based drugs for the treatment of cancer. Metal complexes offer unique opportunities due to their ability to alter pharmacology, improving the efficacy and/or reducing the negative side effects of drug molecules. In addition, transition metals as copper, iron, and manganese, among others, can interact with active sites of enzymes, playing important roles in multiple biological processes. Thus, these complexes not only possess higher activities but also reach their targets more efficiently. This review article highlights recent advances on the emerging and expanding field of metal-based drugs. The emphasis is on new therapeutic strategies consisting of metal complexes with natural product like-compounds as a starting point for the rational design of new antitumor agents.

Dual-targeting antitumor hybrids derived from Pt(IV) species and millepachine analogues

Many strategies have been developed to circumvent the shortcomings of Pt(II)-based chemotherapy, but the inherent problems still have not been effectively resolved. Here we report a new series of dual-targeting Pt(IV) prodrugs, conjugates of millepachine analogues with the related Pt(IV) complexes derived from cisplatin or oxaliplatin, respectively, which can inhibit tubulin polymerization and induce DNA damage. Among them, compound 19 possessed excellent antitumor activities against the tested human cancer cell lines, and arrested the cell cycle at the G2/M phases and ultimately induced cell apoptosis. Interestingly, its low cytotoxicity toward two human normal cells and sensitivity toward two cisplatin-resistant cells revealed the possibility for cancer therapy. More importantly, 19 displayed excellent antitumor efficacy in the SK-OV-3 xenograft model better than cisplatin and the corresponding millepachine analogue. Our research provided an efficient strategy for multi-targeting antitumor drug development.

Pt(IV) complexes conjugating with chalcone analogue as inhibitors of microtubule polymerization exhibited selective inhibition in human cancer cells

Six novel of Pt(IV) complexes comprising chalcone analogues were synthesized and evaluated for anti-proliferative activity using MTT assay. In vitro evaluation revealed that all Pt(IV) complexes showed better and more potent activity against three human cancer cells including CDDP resistant cells than that of their corresponding mother Pt(II) species. Among them, two representative complexes, 14 and 17, exhibited better cell selectivity between cancer cells and normal cells than CDDP. Molecular docking study indicated that complexes 14 and 17 could bind to the colchicine site of tubulin. Moreover, complexes 14 and 17 also remarkably displayed inhibition of cell migration against HUVEC cells in vitro. Molecular mechanism studies suggested that 14 and 17 induced production of reactive oxygen species (ROS), cell cycle arrest at the G2/M phase, and mitochondria-mediated apoptosis by regulating the expression of Bcl-2 family members.

Platinum(IV) complexes conjugated with phenstatin analogue as inhibitors of microtubule polymerization and reverser of multidrug resistance

Pt(IV) complexes comprising a phenstatin analogue, as dual-targeting Pt(IV) prodrug, were designed and synthesized. They were found not only to carry the DNA binding platinum warhead into the tumor cells, but also to have a small molecular unit to inhibit tubulin polymerization. In vitro evaluation results revealed that Pt(IV) complexes showed better and more potent activity against the test human cancer cells including cisplatin resistant cell lines than their corresponding Pt(II) counterparts. In addition, the Pt(IV) derivative of cisplatin, complex 10, exhibited highly selective inhibition in human cancer cells and displayed no obvious toxicity to two human normal cell lines, respectively. Mechanism study suggested that complex 10 induced cell-cycle arrest at the G2/M phase and caused apoptotic cell death of human lung cancer NCI-H460 cells through the mitochondrial mediated pathway. Moreover, complex 10 effectively inhibited the tumor growth in the NCI-H460 xenograft model.

Chalcone: A Privileged Structure in Medicinal Chemistry

Privileged structures have been widely used as an effective template in medicinal chemistry for drug discovery. Chalcone is a common simple scaffold found in many naturally occurring compounds. Many chalcone derivatives have also been prepared due to their convenient synthesis. These natural products and synthetic compounds have shown numerous interesting biological activities with clinical potentials against various diseases. This review aims to highlight the recent evidence of chalcone as a privileged scaffold in medicinal chemistry. Multiple aspects of chalcone will be summarized herein, including the isolation of novel chalcone derivatives, the development of new synthetic methodologies, the evaluation of their biological properties, and the exploration of the mechanisms of action as well as target identification. This review is expected to be a comprehensive, authoritative, and critical review of the chalcone template to the chemistry community.

Combretastatin A-4 Analogue: A Dual-Targeting and Tubulin Inhibitor Containing Antitumor Pt(IV) Moiety with a Unique Mode of Action

Three new Pt(IV) complexes comprising a combretastatin A-4 analogue were designed and synthesized. The resulting antitumor Pt(IV) complexes could significantly improve the antiproliferative activity and overcome the drug resistance of cisplatin in vitro. Interestingly, these novel compounds not only can carry the DNA binding Pt(II) warhead into the cancer cells but also have a small molecule fragment that can inhibit tubulin polymerization. Among them, complex 13, which was attached to an inhibitor of tubulin at one axial position of Pt(IV) octahedral coordination sphere, could effectively enter cancer cells, arrest the cell cycle in HepG-2 cancer cells at G2/M phases, and induce activation of caspases triggering apoptotic signaling via the mitochondrial-dependent apoptosis pathways. Moreover, complex 13 has the ability to effectively inhibit the tumor growth in the HepG-2 xenograft model without causing significant loss of animal body weight in comparison with cisplatin.

Recent advances of cytotoxic chalconoids targeting tubulin polymerization: Synthesis and biological activity

Since microtubules have an important role in mitosis and other vital cellular functions, tubulin-targeting chemotherapy has been received growing attention in anticancer drug design and development. It was found that a number of naturally occurring compounds including distinct chalcones exert their effect by inhibition of tubulin polymerization. After the identification of tubulin polymerization as potential target for chalcone-type compounds, extensive researches have been made to design and synthesis of new anti-tubulin chalconoids. Although diverse chalcones have found to be potent anticancer agents but in the present review, we focused on the recently reported tubulin polymerization inhibitors from chalcone origin and related synthetic compounds, and their detailed synthetic methods and biological activities.

Molecular targeted approaches to cancer therapy and prevention using chalcones

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.

Anti-cancer chalcones: Structural and molecular target perspectives

Chalcone or (E)-1,3-diphenyl-2-propene-1-one scaffold remained a fascination among researchers in the 21st century due to its simple chemistry, ease of synthesis and a wide variety of promising biological activities. Several natural and (semi) synthetic chalcones have shown anti-cancer activity due to their inhibitory potential against various targets namely ABCG2/P-gp/BCRP, 5α-reductase, aromatase, 17-β-hydroxysteroid dehydrogenase, HDAC/Situin-1, proteasome, VEGF, VEGFR-2 kinase, MMP-2/9, JAK/STAT signaling pathways, CDC25B, tubulin, cathepsin-K, topoisomerase-II, Wnt, NF-κB, B-Raf and mTOR etc. In this review, a comprehensive study on molecular targets/pathways involved in carcinogenesis, mechanism of actions (MOAs), structure activity relationships (SARs) and patents granted have been highlighted. With the knowledge of molecular targets, structural insights and SARs, this review may be helpful for (medicinal) chemists to design more potent, safe, selective and cost effective anti-cancer chalcones.

SAR-guided development and characterization of a potent antitumor compound toward B-cell neoplasms with no detectable cytotoxicity toward healthy cells

Acute hematological diseases (leukemias and aggressive lymphomas) can be cured in approximately half of the patients, while the other patients die from their disease. Chronic leukemias and indolent lymphomas can be well controlled for years in most cases. However, the cure rate of these patients is low and the course of the disease is characterized by frequent recurrence. Therefore, novel agents for monotherapies or combination therapies still need to be explored. The presented study describes the identification of the chalcone derivative 15 on different types of human malignant cells of the lymphoid and myeloid lineage. Further experiments performed with compound 15 on peripheral blood mononuclear cells (PBMCs) of chronic lymphocytic leukemia (CLL) patients clearly stated a higher cytotoxicity in PBMC from CLL patients compared to healthy donors (HD). The newly identified chalcone derivative 15 showed a higher therapeutic potential than fludarabine, a drug already in use in lymphoma treatment.

(2Z,4E)-1-(5-Fluoro-2-hy-droxy-phen-yl)-5-(4-fluoro-phen-yl)-3-hy-droxy-penta-2,4-dien-1-one

In the title mol-ecule, C17H12F2O3, the dihedral angle between the benzene rings is 8.6 (2)°. In the crystal, two pairs of O-H⋯O hydrogen bonds connect the mol-ecules into inversion dimers. In addition, weak C-H⋯F hydrogen bonds link the dimers into a two-dimensional network parallel to (10-4). The carbonyl O atom is an acceptor for two weak intra-molecular hydrogen bonds.

Synthesis and biological evaluation of α-triazolyl chalcones as a new type of potential antimicrobial agents and their interaction with calf thymus DNA and human serum albumin

A series of α-triazolyl chalcones were efficiently synthesized. Most of the prepared compounds showed effective antibacterial and antifungal activities. Noticeably, α-triazolyl derivative 9a exhibited low MIC value of 4 μg/mL against MRSA and Micrococcus luteus, which was comparable or even superior to reference drugs. The further research revealed that compound 9a could effectively intercalate into Calf Thymus DNA to form 9a-DNA complex which might block DNA replication to exert their powerful antimicrobial activities. Competitive interactions between 9a and metal ions to Human Serum Albumin (HSA) suggested the participation of Fe(3+), K(+) and Mg(2+) ions in 9a-HSA system could increase the concentration of free 9a, shorten its storage time and half-life in the blood, thus improving its antimicrobial efficacy.

Exploring the DNA binding/cleavage, cellular accumulation and topoisomerase inhibition of 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinone Mannich bases and their platinum(II) complexes

Several chlorido and amino Pt(2+) complexes of 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinone Mannich bases HL exhibiting moderate to high cytotoxicity against cancer cell lines were studied in order to investigate their modes of DNA binding, in vitro DNA strand breaks, mechanism of topoisomerase (Topo I) inhibition and cellular accumulation. DNA model base studies have shown that complex 1a [Pt(HL1)Cl(2)] was capable of binding covalently to 9-ethylguanine (9-EtG) and 5'-GMP. (1)H NMR and mass spectrometry studies have shown that both chlorides were substituted by 9-EtG ligands, whereas 5'-GMP was able to replace only one chlorido ligand, due to steric hindrance. The chlorido Pt(2+) complexes [Pt(HL)Cl(2)] highly accumulate in prostate (PC-3) and melanoma (MDA-MB-435) cell lines, being able to induce DNA strand breaks in vitro and inhibit Topo I by a catalytic mode. On the other hand, the free 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinones HL and the amino Pt(2+) complexes [Pt(L(-))(NH(3))(2)]NO(3) neither cause DNA strand breakage nor exhibit strong DNA interaction, nevertheless the latter were also found to be catalytic inhibitors of Topo I at 100μM. Thus, coordination of the Mannich bases HL to the "PtCl(2)" fragment substantially affects the chemical and biophysical properties of the pro-ligands, leading to an improvement of their DNA binding properties and generating compounds that cleave DNA and catalytically inhibit Topo I. Finally, the high cytotoxicity exhibited by the free (uncomplexed) 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinones might be associated with their decomposition in solution, which is not observed for the Pt(2+) complexes.

Effects of a combretastatin A4 analogous chalcone and its Pt-complex on cancer cells: A comparative study of uptake, cell cycle and damage to cellular compartments

The combretastatin A4 analogous chalcone (2E)-3-(3-hydroxy-4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one 1 and its dichloridoplatinum(II) (6-aminomethylnicotinate) complex 2 were previously found to be highly active against a variety of cancer cell lines while differing in their apoptosis induction and long-term regrowth retardation (Schobert et al. [1]). Further differences were identified now. The cellular uptake of complex 2, like that of oxaliplatin, occurred mainly via organic cation transporters (OCT-1/2; ∼32%) and copper transporter related proteins (Ctr1; ∼24%), whereas that of chalcone 1 was dependent on endocytosis (∼80%). Complex 2 was more tumour-specific than 1 concerning neural cells. This was apparent from the ratios of IC(50)(48h) values against primary astrocytes versus human glioma cells U87 (>7000 for complex 2; 55 for compound 1). In tubulin-rich neurons and 518A2 melanoma cells complex 2 disrupted microtubules and actin filaments. Cancer cells treated with 2 could repair the cytoskeletal damage but ceased to proliferate and perished. Complex 2 was particularly cytotoxic against P-gp-rich cells. It acted as a substrate for ABC-transporters of types BCRP, MRP3, and MRP1 and so was less active against the corresponding cancer cell lines. Complex 2 arrested the cell cycle of the melanoma cells in G(1) and G(2)/M phases. A fragmentation of their Golgi apparatus was observed by TEM for incubation with complex 2 but not with 1. In conclusion, unlike chalcone 1, its platinum complex 2 is highly cell line specific, is taken up via cell-controlled transporters and induces apoptosis by triggering multiple targets.

Oxazole-bridged combretastatin A analogues with improved anticancer properties

Three new oxazole-bridged combretastatin A analogues with additional functional groups at the B-ring [-SMe, -OH, p-quinone] were tested for antiproliferative activity and specificity on human HL-60 leukemia, 518A2 melanoma, and colon carcinomas HCT-116 (wt)/(p53(-/-)) and HT-29 cells. While all oxazoles, except quinone 8, were efficacious against HCT-116 cells at submicromolar IC(50) values (48 h incubation), only thioanisole 5 achieved this potency in combretastatin-refractory HT-29 cells by significant upregulation of p21(cip1/waf1) associated with an S/G(2) cell-cycle arrest.