Cell death-inducing properties of selected dendrimers against different breast cancer and leukemia cell lines.

Dendrimers represent an opportunity for targeted drug delivery into tumor cells. This is facilitated, for example, by loading of dendrimers with anticancer compounds. However, to assess the effects caused by such conjugates, knowledge of the cytotoxicity of the dendrimers themselves is necessary. The poly(amido amine)-derived dendrimers G1 (Phe)6 , G1 (Dan)3 , and G2 were selected due to their different numbers of free amino groups and the poly(propylene imine) (PPI) dendrimer PPI-G3 served as a reference. The compounds were evaluated for cell-death induction using breast cancer (MCF-7, MDA-MB-231) and leukemia (LAMA-84, K562, SD-1, SUP-B15) cell lines. The compounds exhibited concentration-dependent effects in the low micromolar range against the mammary carcinoma cells. A dependency on the generation, and particularly on the type of dendrimer, was deduced while the quantity of the free amino groups was subsidiary. G2 revealed to be most cytotoxic, also against all tested leukemia cell lines. The cell line SD-1, however, was susceptible to all dendrimers. The mode of cell death was mainly determined by necrosis, especially at higher concentrations, while apoptosis played a subordinate role. The other dendrimers exerted no antimetabolic effects against LAMA-84, K562, and SUP-B15 cells. Therefore, these dendrimers are generally suitable as nontoxic drug carriers for leukemia cells.

Platinum(II)-dendrimer conjugates: synthesis and investigations on cytotoxicity, cellular distribution, platinum release, DNA, and protein binding.

A set of polyamidoamine dendrimers were modified in such a way that they are able to act as carrier and drug delivery systems for cytostatics. The terminal binding of the non-proteinogenic D,L-2,3-diaminopropionic acid allowed the attachment of the cytotoxic PtX(2) moiety (X = Cl, I: A(PtI(2))(2), A(PtCl(2))(2), B(PtI(2))(2), B(PtCl(2))(2)), while the 2-carboxypentanedioic acid acted as leaving group for [meso-1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II) ((m-4F-Pt)(3)C, (m-4F-Pt)(3)D). Poly(ethylene glycol) chains at C(PtI(2))(3) and C(PtCl(2))(3) as well as (m-4F-Pt)(3)C and (m-4F-Pt)(3)D mediated sufficient water solubility. Additional dansyl residues (B(PtI(2))(2) and (m-4F-Pt)(3)D) made a simultaneous determination of platinum (graphite furnace atomic absorption spectroscopy (GF-AAS)) and dendrimer (fluorimetry) possible. The ethylenediamine-terminated dendrimers were typically accumulated into MCF-7 cells in clathrin-dependent pathways and targeted the platinum moieties to the nuclear compartment. The highest intracellular platinum concentration and DNA binding caused the dendrimers A(PtX(2))(2) and B(PtX(2))(2). A coordinative DNA binding, however, is very unlikely because of low cytotoxic effects. (m-4F-Pt)(3)C and (m-4F-Pt)(3)D are labile conjugates and liberated the m-4F-Pt moiety in biological systems. The effects of these dendrimers were similar to that of the reference compounds m-4F-PtCl(2) and m-4F-Pt(H(2)O)(2).

Investigations on surface modified dendrimers: enzymatic hydrolysis and uptake into MCF-7 breast cancer cells.

A series of G(0) and G(1) generation 1,3,5-tris(3-aminopropyl)benzene dendrimers surface modified with the amino acids phenylalanine (Phe), methionine (Met), aspartic acid (Asp), and diaminopropionic acid (Dap) was investigated with regard to their stability against enzymatic hydrolysis with the model enzymes papain, chymotrypsin, trypsin, and pepsin. Additionally, the cytosol of MCF-7 cells was used to get an insight into the possible degradation in intracellular medium. The cytosol, chymotrypsin, and papain had similar activities on the tested dendrimers and efficiently cleaved methionine and phenylalanine from the surface of the dendrimers. The cellular uptake of the dendrimers into the MCF-7 cells depended on the surface modification (Phe>Met unmodified>>Dap=Asp) and the generations (G(0)>G(1)).

Biological effect of mono- and dinuclear alkylamine platinum(II) compounds on human lymphoma cells.

The effects of the mononuclear chloro[meso-1,2-bis(4-fluorophenyl)ethylenediamine][hexylamine]platinum(II) chloride HACl and the dinuclear di[meso-1,2-bis(4-fluorophenyl)ethylenediamine]dichloro(mu-1,n-diaminoalkane-N:N')diplatinum(II)dichloride complexes DAHCl (alkane:hexane), DANCl (alkane:nonane) and DADCl (alkane:dodecane) with different alkyl chain length (n) were investigated on non-Hodgkin's lymphoma (NHL) and chronic myeloid leukemia (CML) cell lines. All compounds showed an antiproliferative effect on the NHL cell lines RAJI and U-937 accompanied in the case of DANCl, DAHCl, HACl and cisplatin by an increase in apoptosis. The growth of another NHL (JEKO-1) and one CML cell line (K-562) was decreased only by cisplatin. In contrast to HACl, DAHCl, DANCl and cisplatin, DADCl induced necrosis, suggesting toxicity because cell viability decreased. Similar effects were observed when bone marrow-derived lymphoma cells from a patient with high-grade B-NHL were incubated with the platinum complexes.

Dinuclear alkylamine platinum(II) complexes of [1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II): influence of endocytosis and copper and organic cation transport systems on cellular uptake.

Various possible pathways for the uptake of cationic alkylamine platinum(II) complexes into the MCF-7 breast cancer cells were studied with di[meso-1,2-bis(4-fluorophenyl)ethylenediamine]di[sulfinylbis(methane)-S][mu-1,6-diaminohexaneN:N']diplatinum(II) disulfate (m-4F-PtDMSO-DAH) as an example. It was demonstrated that m-4F-PtDMSO-DAH competed neither for the copper transporter nor the organic cation transporters (OCT and OATP). Instead, adsorptive endocytosis by macropinocytosis played an essential role. Inhibitors of this processes such as amiloride, N-ethyl-N-isopropylamiloride (EIPA), wortmannin, and cytochalasin D decreased the intracellular uptake of m-4F-PtDMSO-DAH dramatically. These results support the understanding of the pharmacological behavior of this promising drug family, which showed no cross resistance with cisplatin.

Mono- and polynuclear [alkylamine]platinum(II) complexes of [1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II): synthesis and investigations on cytotoxicity, cellular distribution, and DNA and protein binding.

A series of mononuclear and dinuclear alkylamine derivatives of [meso-1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II) (m-4F-PtL-R1 and (m-4F-PtL)2-R2; R(1) = alkylamine, R(2) = alkyldiamine, L = DMSO or Cl) as well as the DAB(PA)(4) polyimine dendrimer complex ((m-4F-PtDMSO)4DAB(PA)4; DAB(PA)4 = N,N,N',N'-tetrakis(3-aminopropyl)butane-1,4-diamine) were synthesized and tested for cytotoxicity, intracellular distribution, and DNA and protein binding. All compounds strongly bound to human serum albumin by hydrophobic and electrostatic interactions. These inactivation reactions hindered the uptake into tumor cells and prevented strong cytotoxic effects. If serum-free medium was used, a high accumulation grade in MCF-7 breast cancer cells and a high DNA binding was observed. As most efficient compound (m-4F-PtDMSO)4DAB(PA)4 was identified. It showed a 20-fold higher cellular uptake and an approximately 700-fold higher DNA binding than cisplatin.

A surface-modified dendrimer set for potential application as drug delivery vehicles: synthesis, in vitro toxicity, and intracellular localization.

The synthesis, cytotoxicity, and behavior in cell culture of a new set of first- (G1) and second-generation (G2) dendrimers is reported. The surface functionality of these dendrimers has been varied to see whether structure/toxicity relations can be observed. The outermost functional groups are amines that are decorated either with protons, tert-butoxycarbonyl (Boc) or benzyloxycarbonyl (Cbz) protecting groups, Boc-protected or unprotected natural amino acid residues, ethylenediamine ligands, and/or dansyl fluorescence labels. The cytotoxicity was determined in vitro in concentration-dependent assays using the human MCF-7 breast cancer cell line. Cellular uptake and intracellular distribution was monitored by confocal fluorescence microscopy after internalization of the dansyl-labeled dendrimers by HeLa cells.