Effect of the Farnesyl Transferase Inhibitor L-744,832 on the Colon Cancer Cell Line DLD-1 and Its Combined Use with Radiation and 5-FU

Heteropentanuclear Oxalato-Bridged nd-4f (n=4, 5) Metal Complexes with NO Ligand: Synthesis, Crystal Structures, Aqueous Stability and Antiproliferative Activity

A series of heteropentanuclear oxalate-bridged Ru(NO)-Ln (4d–4f) metal complexes of the general formula (nBu₄N)₅[Ln{RuCl₃(μ-ox)(NO)}₄], where Ln=Y (2), Gd (3), Tb (4), Dy (5) and ox=oxalate anion, were obtained by treatment of (nBu₄N)₂[RuCl₃(ox)(NO)] (1) with the respective lanthanide salt in 4:1 molar ratio. The compounds were characterized by elemental analysis, IR spectroscopy, electrospray ionization (ESI) mass spectrometry, while 1, 2, and 5 were in addition analyzed by X-ray crystallography, 1 by Ru K-edge XAS and 1 and 2 by ¹³C NMR spectroscopy. X-ray diffraction showed that in 2 and 5 four complex anions [RuCl₃(ox)(NO)]²⁻ are coordinated to Y^III and Dy^III, respectively, with formation of [Ln{RuCl₃(μ-ox)(NO)}₄]⁵⁻ (Ln=Y, Dy). While Y^III is eight-coordinate in 2, Dy^III is nine-coordinate in 5, with an additional coordination of an EtOH molecule. The negative charge is counterbalanced by five nBu₄N⁺ ions present in the crystal structure. The stability of complexes 2 and 5 in aqueous medium was monitored by UV/Vis spectroscopy. The antiproliferative activity of ruthenium-lanthanide complexes 2–5 were assayed in two human cancer cell lines (HeLa and A549) and in a noncancerous cell line (MRC-5) and compared with those obtained for the previously reported Os(NO)-Ln (5d–4f) analogues (nBu₄N)₅[Ln{OsCl₃(ox)(NO)}₄] (Ln=Y (6), Gd (7), Tb (8), Dy (9)). Complexes 2–5 were found to be slightly more active than 1 in inhibiting the proliferation of HeLa and A549 cells, and significantly more cytotoxic than 5d–4f metal complexes 6–9 in terms of IC₅₀ values. The highest antiproliferative activity with IC₅₀ values of 20.0 and 22.4 μM was found for 4 in HeLa and A549 cell lines, respectively. These cytotoxicity results are in accord with the presented ICP-MS data, indicating five- to eightfold greater accumulation of ruthenium versus osmium in human A549 cancer cells.

Mitomycin C and Etoposide in Advanced Colorectal Carcinoma

BACKGROUND

Aim of this study was to evaluate the activity of a combination regimen of chemotherapy containing mitomycin C (MMC) and etoposide (ETO) in advanced colorectal carcinoma.

METHODS

Fourteen pretreated patients received MMC 2 mg/m2 and ETO 60 mg/m2, days 1-5 every 28 days. The clinical study was interrupted since no clinical response was observed in 14 patients following four courses of chemotherapy. An in vitro study was then performed on HTC-8 cell line. The cytotoxic activity of the MMC/ETO combination was tested by sulforhodamine B assay and the type of drug interaction was assessed using the method of Chou and Talalay. Cell cycle perturbations and apoptosis were evaluated by flow cytometry.

RESULTS

While MMC and ETO were singularly active, the simultaneous exposure of cells to both drugs and the sequence MMC-->ETO ensued in antagonistic interaction at all levels of killed cell fraction. Conversely, the sequence ETO-->MMC produced a synergistic interaction.

CONCLUSIONS

These results suggest that the activity of the MMC/ETO combination is highly schedule-dependent and that the experimental drug associations should be based on a preclinical rationale before clinical trials are designed.

Multidrug-resistant cancer cells are preferential targets of the new antineoplastic lanthanum compound KP772 (FFC24)

Recently, we have introduced [tris(1,10-phenanthroline)lanthanum(III)] trithiocyanate (KP772, FFC24) as a new lanthanum compound which has promising anticancer properties in vivo and in vitro. Aim of this study was to investigate the impact of ABC transporter-mediated multidrug resistance (MDR) on the anticancer activity of KP772. Here, we demonstrate that all MDR cell models investigated, overexpressing ABCB1 (P-glycoprotein), ABCC1 (multidrug resistance protein 1), or ABCG2 (breast cancer resistance protein) either due to drug selection or gene transfection, were significantly hypersensitive against KP772. Using ABCB1-overexpressing KBC-1 cells as MDR model, KP772 hypersensitivity was demonstrated to be based on stronger apoptosis induction and/or cell cycle arrest at unaltered cellular drug accumulation. KP772 did neither stimulate ABCB1 ATPase activity nor alter rhodamine 123 accumulation arguing against a direct interaction with ABCB1. Accordingly, several drug resistance modulators did not sensitize but rather protect MDR cells against KP772-induced cytotoxicity. Moreover, long-term KP772 treatment of KBC-1 cells at subtoxic concentrations led within 20 passages to a complete loss of drug resistance based on blocked MDR1 gene expression. When exposing parental KB-3-1 cells to subtoxic, stepwise increasing KP772 concentrations, we observed, in contrast to several other metallo-drugs, no acquisition of KP772 resistance. Summarizing, our data demonstrate that KP772 is hyperactive in MDR cells and might have chemosensitizing properties by blocking ABCB1 expression. Together with the disability of tumor cells to acquire KP772 resistance, our data suggest that KP772 should be especially active against notoriously drug-resistant tumor types and as second line treatment after standard chemotherapy failure.

Effect of rapamycin on hepatocyte function and proliferation induced by growth factors

BACKGROUND

Rapamycin is a specific inhibitor of the mammalian target of rapamycin (mTOR). The effect of rapamycin on proliferation and cellular function was studied in hepatocytes stimulated by hepatocyte growth factor (HGF) or transforming growth factor-alpha (TGFalpha).

METHODS AND RESULTS

When isolated rat hepatocytes were cultured at low density, the addition of HGF or TGFalpha increased DNA synthesis but did not affect albumin or fibrinogen concentrations in the medium. In contrast, in hepatocytes cultured at high density, the albumin and fibrinogen concentrations, but not DNA synthesis, were increased by HGF or TGFalpha. The HGF- or TGFalpha-induced increase in DNA synthesis and in albumin or fibrinogen concentrations was suppressed by the addition of rapamycin, as well as wortmannin, a phosphatidylinositol-3 kinase inhibitor.

CONCLUSION

HGF and TGFalpha stimulate proliferation and function of hepatocytes depending upon the conditions, and rapamycin inhibited these stimulatory effects, possibly by inhibiting the mTOR-dependent signaling pathway.