The reduction of (ImH)[<Emphasis Type="Italic">trans</Emphasis>-Ru<Superscript>III</Superscript>Cl<Subscript>4</Subscript>(dmso)(Im)] under physiological conditions: preferential reaction of the reduced complex with human serum albumin

A systematic study of the reduction of (ImH)[trans-RuCl(4)(dmso)(Im)] (NAMI-A; dmso is dimethyl sulfoxide, Im is imidazole), a promising antimetastasing agent, by L: -ascorbic acid under physiological conditions is reported. Under blood plasma conditions (pH 7.4, 0.1-0.15 M NaCl , 37 degrees C) the rapid reduction of trans-[Ru(III)Cl(4)(dmso)(Im)](-) results in the formation of trans-[Ru(II)Cl(4)(dmso)(Im)](2-) within seconds, and is followed by successive dissociation of the chloride ligands, whereas neither dmso nor imidazole ligands are released during the reaction. Under our experimental conditions, the formation of the ascorbate dianion is the rate-determining step, and once it has formed it reacts rapidly with NAMI-A. Moreover, the NAMI-A complex is very unstable at physiological pH (7.4); therefore, the hydrolysis of NAMI-A cannot be excluded as a competing reaction. During hydrolysis, aquated derivatives via stepwise dissociation of chloride and dmso ligands are formed, and most of these species have a higher redox potential and are expected to be even more easily reduced by ascorbic acid. Thus, it is very likely that the reduced form of NAMI-A or the reduction products of its hydrolytic derivatives react with albumin. The reaction of reduced NAMI-A with human serum albumin leads to the formation of stable adducts, with a binding efficiency very similar to that of the parent complex, viz., 3.2 +/- 0.3 and 4.0 +/- 0.4 mol of Ru(II) and Ru(III) per mole of albumin, respectively, however with a significantly higher reactivity.     

Inhibition of the metastatic progression of breast and colorectal cancer in vitro and in vivo in murine model by the oxidovanadium(IV) complex with luteolin

The anticancer and antimetastatic behavior of the flavonoid luteolin and its oxidovanadium(IV) complex [VO(lut)(H₂O)₂]Na·3H₂O (VOlut) has been investigated. Considering that the complex displayed strong anticancer activity on MDAMB231 human breast cancer cell line we herein determined through in vitro assays that the complex would probably reduce breast cancer cell metastasis in a higher extent than the natural antioxidant. In the CT26 colon cancer cell line a stronger anticancer effect has also been determined for the complex (IC₅₀ 0.9 μM) and in addition it did not exert toxic effects on normal colon epithelial cells at concentrations up to 10 μM. Working with a murine model of highly aggressive, orthotopic colon cancer model (CT26 cancer cell lines) it has been determined that the complex might prevent metastatic dissemination of the colon cancer cells to the liver. The flavonoid luteolin also exerted anticancer effects (at a low degree, IC₅₀ 5.9 μM) on CT26 cell line and produced a 24% reduction of colon cancer liver metastasis.     

Further studies of the therapeutic effectsof murine melanoma-specific monoclonal antibodies

The results presented here further characterize four murine monoclonal antibodies (mAb) that recognize melanoma-specific antigens (9B6, T97, 2-3-1 and 2-3-3). These melanoma-specific mAbs are of the IgG_2b isotype and are significantly therapeutic when administered systemically against established pulmonary melanoma metastases. Here we show a consistent and significantly inhibition of the growth of melanoma lung metastases by all four mAbs and the existence of a time ‘window’ at days 5–8 after tumor inoculation for optimal therapy. Since these mAbs were found not to be cytotoxic or cytolytic in vitro, we looked for host immune response regulation as being responsible for the therapeutic effects. Natural killer (NK) cells were implication as one arm of the host immune system involved in this response since depletion of NK cells in vivo by αasialoGM1 or αNK1.1 antibodies partially abrogated the inhibitory effect of the mAbs. The observed antimetastatic effects could also be partially abrogated using antibodies directed against the T-cell subset surface markers, CD4⁺ and CD8⁺. Intramuscular melanoma tumor growth was also found to be suppressed by mAb 2-3-1, but only if administered in the area of tumor growth and only if multiple inoculations are administered over a 13-day period. The beneficial effect of mAb antimetastatic therapy was found to be useful against several syngeneic melanomas, including JB/MS, B16 and several sublines of the B16 F10 melanoma.     

Discovery of novel cathepsin inhibitors with potent anti-metastatic effects in breast cancer cells

It is still challenging to determine the potential targets of natural products, which is essential for further drug research and development. Due to its novel mechanism of action of inducing autophagy effects in breast cancer cells, asperphenamate has received our considerable attention. However, its unknown target inevitably impedes further study. In our previous work, the target enzyme of asperphenamate was predicted as cathepsin by the natural product consensus pharmacophore strategy. Then, asperphenamate and its three derivatives were chosen to study in detail by molecular docking calculations with AutoDock 4 suite. The docking results showed the three derivatives interacted more tightly with either cathepsin L or cathepsin S than with asperphenamate. The ortho-benzyloxyl phenylacetyl derivative 1 and p-toluenesulfonyl derivative 3 showed similar interactions with cathepsin L and adopted a better geometric shape within the binding pocket than did the N-CBZ-piperidyl analog 2. On the other hand, compound 2 formed more hydrogen bonds than 1 and 3 to make it tightly bind within cathepsin S. The cathepsin inhibitory activity assay verified the molecular simulation results. Compound 2 was remarkably less active than 1 and 3 against cathepsin L. However, compound 2 showed the strongest potency against cathepsin S with IC₅₀ of 13.12 ± 0.29 μM. Considering that cathepsin S plays a vital role in the process of metastasis in breast cancer cells, the inhibitory effect of 2 on migration and invasion was further studied in human breast cancer MDA-MB-231 cells by wound healing and transwell chamber assays. The results illustrated that 2 exhibited an apparent inhibitory ability to the metastasis of MDA-MB-231 cells. Next, 2 will be chosen as a lead compound to develop novel double functional chemotherapeutic agents with both novel mechanisms of action against apoptosis-resistant cancer cells, such as inducing autophagy and inhibiting cancer metastasis.     

Tumor cell cholesterol depletion and V-ATPase inhibition as an inhibitory mechanism to prevent cell migration and invasiveness in melanoma

Background

V-ATPase interactions with cholesterol enriched membrane microdomains have been related to metastasis in a variety of cancers, but the underlying mechanism remains at its beginnings. It has recently been reported that the inhibition of this H⁺ pump affects cholesterol mobilization to the plasma membrane.

Arylamidonaphtalene sulfonate compounds as a novel class of heparanase inhibitors

The search for antimetastatic agents for cancer therapy may involve the ability of new compounds to maintain the tissue extracellular matrix integrity. Among known factors, heparanase, an endoglucuronidase responsible for heparan sulfate cleavage, is a promising target whose inhibition could represent a strong obstacle for metastatic cancerous mechanisms. The antimetastatic activity of some suramin derivatives reported in literature suggests a possible involvement of the heparanase enzyme. To confirm such hypothesis, we have investigated FCE27266, a molecule known for its antiangiogenic and antimetastatic properties. Other new derivatives were also synthesized and investigated. Our findings revealed that FCE27266 as well as some derivatives have a strong heparanase inhibition activity, together with no cytotoxic power. Moreover, a FCE27266 analogue (SST0546NA1; 17a) resulted also positive to lower gene expression of some proangiogenic factors.     

Antitumor effects of rhodium(I), iridium(I) and ruthenium(II) complexes in comparison with cis-dichlorodiammino platinum(II) in mice bearing Lewis lung carcinoma

The effects of square planar rhodium, [RhacacCOD]o and iridium, [IracacCOD]o complexes and of octahedral ruthenium, [cis-RuCl2 (DMSO)4]o complex have been examined in comparison with cis-dichlorodiammino platinum(II) (cis-PDD). The toxicity in BDF1 mice varies widely and decreasing LD50-values, ranging from 0.94 mg/kg to 1000 mg/kg, have been obtained for cis-PDD, [RhacacCOD]o, [IracacCOD]o and [cis-RuCl2(DMSO)4]o, respectively. All the tested complexes similarly inhibit the growth of subcutaneous Lewis lung carcinoma and the development of spontaneous as well as of artificial metastases, with the exception of [IracacCOD]o which is inactive on metastases. The antitumor activity of [RhacacCOD]o and [cis-RuCl2(DMSO)4]o appears interesting, since it is of the same magnitude as that of cis-PDD, considering also that they were found to be only marginally nephrotoxic.     

Markedly induced asialoGM1+CD8+ T cell production and enhancement of antimetastatic activity by interferon β with folic or folinic acid

 Either folic or folinic acid enhanced the antimetastatic activity of recombinant murine interferon β (rMuIFNβ) toward highly metastatic colon carcinoma 26 (Co 26Lu). Folinic acid administered with rMuIFNβ markedly increased asialoGM1⁺CD4⁺ and asialoGM1⁺CD8⁺ T cell production in the peritoneal cavity but not in the thymus and spleen. Peritoneal cells expressed killing activity toward Co 26Lu cells in vitro. In athymic nude mice, the above combination produced many asialoGM1⁺CD4⁺ and few asialoGM1⁺CD8⁺ T cells in the peritoneal cavity, but did not decrease lung metastatic colonies. AsialoGM1⁺CD4⁺ T cells would thus appear to have no or only very weak killing activity toward these tumor cells. The antimetastatic activity of folinic acid with rMuIFNβ was significantly decreased with anti-asialoGM1 and anti-CD8 antibodies. Inactivated CD8⁺ and asialoGM1⁺ cells cease to have killing activity toward Co 26Lu cells as shown by Winn’s assay. AsialoGM1⁺CD8⁺ cell production was markedly induced in the peritoneal cavity by treatment with rMuIFNβ and folinic acid. AsialoGM1⁺CD8⁺ T cells may be inhibiting lung metastasis of Co 26Lu. Folinic acid and interferon are used in combination therapy with 5-fluorouracil for biochemical modulation. Folinic acid with interferon, as adjuvant therapy, may promote the induction of CD8⁺ T cell production with consequent prevention of metastasis. Received: 1 August 1996 / Accepted: 31 December 1996