Antiproliferative and anti-invasive effects of inorganic and organic arsenic compounds on human and murine melanoma cells in vitro.

OBJECTIVES: For patients with advanced melanoma, no treatment options are available at present that provide either sufficient response rates or a significant prolongation of overall survival. The present study examines the effects of two inorganic and six organic arsenic compounds on cell proliferation and cell invasion of melanoma cells in vitro. METHODS: The effects of arsenic compounds on proliferation of human melanoma A375 cells and murine melanoma B16F10 cells were examined by MTT assay and 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, and the effects of the compounds on cell invasion were examined by the Boyden chamber invasion assay. The amounts of active matrix metalloproteinase (MMP)-2 and pro-MMP-2 in the culture supernatant of A375 cells were determined by an MMP-2 activity assay system. KEY FINDINGS: Arsenate and arsenic trioxide (As(2) O(3) ) inhibited the proliferation of A375 and B16F10 cells significantly at concentration ranges of 0.1-20µg/ml (P<0.001), while the organic compounds arsenobetaine, arsenocholine, dimethylarsinic acid, methylarsonic acid, tetramethylarsonium and trimethylarsine oxide did not show any inhibitory effects even at 20µg/ml. Cell invasion of A375 and B16F10 cells through a layer of collagen IV was significantly inhibited by 0.1-20 µg/ml of arsenate or As(2) O(3) (P<0.05), while the organic compounds did not inhibit cell invasion. Arsenate or As(2) O(3) at 0.2-10µg/ml significantly inhibited the amount of active MMP-2 and pro-MMP-2 secreted into the A375 cell culture supernatant (P<0.05). CONCLUSIONS: Our findings show that the inorganic arsenic compounds arsenate and As(2) O(3) inhibit cell proliferation and prevent the invasive properties of melanoma cells, possibly by decreasing MMP-2 production from the cells.

Effects of naturally occurring polymethyoxyflavonoids on cell growth, p-glycoprotein function, cell cycle, and apoptosis of daunorubicin-resistant T lymphoblastoid leukemia cells.

Effects of polymethoxyflavonoids tangeretin and nobiletin and the related polyphenolic compounds baicalein, wogonin, quercetin, and epigallocatechin gallate on the cell growth, P-glycoprotein function, apoptosis, and cell cycle of human T lymphoblastoid leukemia MOLT-4 and its daunorubicin-resistant cells were investigated. The IC50 values of these compounds on the cell growth were 7.1-32.2 micromol/L, and the inhibitory effects were observed to be almost equal to the parent MOLT-4 and the daunorubicin-resistant cells. Tangeretin and nobiletin showed the strongest effects with the IC50 values of 7.1-14.0 micromol/L. These polymethoxyflavonoids inhibited the P-glycoprotein function and significantly influenced the cell cycle (p<.05), whereas they did not induce apoptosis.

Methoxy- and fluoro-chalcone derivatives arrest cell cycle progression and induce apoptosis in human melanoma cell A375.

Because of the lack of efficacious treatments for advanced melanoma, new approaches are necessary. Chalcones are contained in fruits and vegetables, and have been suggested to be cancer-preventive. In this study, effects of synthetic chalcone derivatives were investigated especially on the proliferation of human melanoma cells and peripheral blood mononuclear cells (PBMCs). Four out of the 12 synthetic chalcones: 4-trifluoromethyl-4'-methoxychalcone (CH-1), 4-trifluoromethyl-2'-methoxychalcone (CH-3), 3-trifluoromethyl-2',4'-dimethoxychalcone (CH-4) and 3-trifluoromethyl-4'-methoxychalcone (CH-7) exhibited significant antiproliferative efficacies against the cultured cells of the human melanoma cell line A375. CH-1, CH-3, CH-4, and CH-7 induced cell cycle arrest at the S-G(2)/M phase within 24 h after the treatment. CH-3, CH-4, and CH-7 significantly activated caspase-3 at 12 h, subsequently induced apoptosis at 72 h. All chalcones inhibited concanavalin A-induced proliferation of PBMCs dose-dependently. Our results suggest that some methoxy- and/or fluoro-chalcones have antitumor efficacy by inducing apoptosis and the cell-cycle arrest.

Relationship between plasma leptin or soluble cleaved leptin-receptor concentrations and glucocorticoid sensitivity of peripheral blood mononuclear cells in patients with nephrotic syndrome.

Leptin is a small peptide hormone which centrally regulates weight. Leptin receptor (OB-R) is expressed in hematopoietic cells, the central nervous, and immune systems. OB-R bears a homology similar to members of the class Iota cytokine family, and therefore, leptin appears to modulate immune responses. The aim of this study was to examine the effect of plasma leptin, soluble OB-R (sOB-R), and the free leptin index (FLI), the ratio between leptin and sOB-R levels, on the sensitivities of peripheral blood mononuclear cells (PBMCs) to prednisolone and cyclosporine in 16 healthy subjects and seven nephrotic syndrome (NS) patients. The NS patients had significantly higher serum sOB-R and lower FLI, compared with the healthy subjects (respectively, P=0.0026, P=0.0383). Whereas, the NS patients had significantly lower PBMC sensitivity to prednisolone (P=0.0049). PBMCs sensitivity to cyclosporine was not significantly different between the healthy subjects and the NS patients. In addition, when the data from all subjects were analyzed, there was a significantly positive correlation between plasma sOB-R concentrations and the IC50 values of prednisolone (P=0.0478). In contrast, plasma leptin concentrations and FLIs did not correlate significantly with the prednisolone and cyclosporine IC50 values. From these observations it can be suggested that plasma leptin has little effect on PBMC sensitivity to immunosuppressive drugs in NS patients. Molecular background(s) for the influence of sOB-R on the PBMC sensitivity to glucocorticoids remain(s) to be elucidated.

P-glycoprotein functions in peripheral-blood CD4+ cells of patients with systemic lupus erythematosus.

Over-expression of P-glycoprotein (P-gp) in lymphocytes is implicated in the failure of immunosuppressant therapy. We investigated P-gp function in peripheral-blood CD3+, CD4+, and CD8+ cells of 14 healthy subjects and 12 patients with systemic lupus erythematosus (SLE). P-gp function was estimated by the transporter activity of the cells based on the efflux of Rhodamine-123 (Rh123) from the cells in the presence or absence of a P-gp inhibitor, cyclosporine A. P-gp function in the CD8+ cells of the healthy subjects was significantly higher than that of the SLE patients (p=0.0318), whereas the function in CD3+ cells and CD4+ cells were not significantly different between the healthy subjects and the SLE patients. The patients were divided into two subgroups according to their clinical response to glucocorticoid (GC) therapy, i.e., a high-response group (HR) (n=6) and a low-response group (LR) (n=6). In contrast, P-gp function in CD4+ cells of the LR group was significantly higher than that of the HR group (p=0.0432). Further, no significant differences in the P-gp function in CD3+ and CD8+ cells were observed between the two groups. The data showed a relationship between clinical sensitivity to GC therapy and P-gp function of CD4+ cells in SLE patients. Thus, the estimation of P-gp function in peripheral-blood CD4(+) cells might be useful for the estimation of clinical response to GC therapy.

Direct observation of conformational folding coupled with disulphide rearrangement by using a water-soluble selenoxide reagent--a case of oxidative regeneration of ribonuclease A under weakly basic conditions.

Oxidative regeneration pathways of bovine pancreatic ribonuclease A (RNase A), which has four SS linkages, were studied at 25 degrees C and pH 8.0 by using trans-3,4-dihydroxy-1-selenolane oxide (DHS(ox)), a new selenoxide reagent with strong oxidation power. The short-term folding study using a quench-flow instrument ( approximately 1 min) revealed that early intermediates (1S, 2S, 3S and 4S) are formed stochastically and irreversibly from the reduced protein (R) and do not have any stable structures. In the long-term folding study ( approximately 300 min), on the other hand, slow generation of the key intermediates (des[65-72] and des[40-95]) through SS rearrangement from the 3S intermediate ensemble was observed, followed by slight formation of native RNase A (N). The parallel UV and CD measurements demonstrated that formation of the key intermediates is accompanied with the formation of the native-like structures. Thus, DHS(ox) allowed facile identification of the conformational folding steps coupled with SS rearrangement on the major oxidative folding pathways.