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Neuroblastoma, the most common extracranial solid tumour of childhood, is a malignancy of unknown origin and non-specific symptoms. One of the markers of the disease is GD2 ganglioside (disialoganglioside), which is abundantly expressed on the surface of neuroblastoma cells. Gangliosides are known to be shed by tumour cells and this phenomenon can be significant in cancer progression as they inhibit a number of immune responses both in vitro and in vivo. In search for novel markers useful in monitoring and prognosis of neuroblastoma, we developed and validated a new quantitative method of GD2 ganglioside analysis in human blood plasma. We evaluated the level of gangliosides in blood serum of 34 neuroblastoma patients using high-performance liquid chromatography. The technique was used to detect fluorescently labelled oligosaccharides derived from serum glycosphingolipids by enzymatic digestion with ceramide glycanase. The developed method allowed determination of GD2 concentrations at the picomole level and required only 40 microl of plasma, which should be particularly useful when the quantity of clinical material is limiting. Moreover, this method can be applied to study concentration of other gangliosides, as shown for GD3 ganglioside. Analysis of plasma samples from the 34 neuroblastoma patients did not reveal any correlations between the concentration of GD2 ganglioside and clinical parameters, including the results of therapy; it showed, however, that the concentration of GD2 ganglioside in the plasma of neuroblastoma patients decreased substantially in the course of treatment.

We present three novel mutations in the G6PD gene and discuss the changes they cause in the 3-dimensional structure of the enzyme: 573C-->G substitution that predicts Phe to Leu at position 191 in the C-terminus of helix alphae, 851T-->C mutation which results in the substitution 284Val--> -->Ala in the beta+alpha domain close to the C-terminal part of helix alphaj, and 1175T-->C substitution that predicts Ile to Thr change at position 392.

In vitro antileukemic activity of five glucocorticoids and their cross-resistance pattern in childhood acute lymphoblastic and non-lymphoblastic leukemia were determined by means of the MTT assay in 25 leukemia cell samples of childhood acute leukemias. The equivalent antileukemic concentrations of the drugs tested were: 34 microM hydrocortisone (HC), 8 microM prednisolone (PRE), 1.5 microM methylprednisolone (MPR), 0.44 microM dexamethasone (DX) and 0.22 microM betamethasone (BET). In comparison with initial ALL cell samples, the relapsed ALL group was more resistant to PRE (38-fold, p = 0.044), DX (> 34-fold, p = 0.04), MPR (38-fold), BET (45-fold) and HC (33-fold). The AML cell samples were even more resistant to: PRE (> 85-fold, p = 0.001), DX (> 34-fold, p = 0.004), MPR (> 69-fold, p = 0.036), BET (> 69-fold, p = 0.038) and HC (54-fold, p = 0.059) when compared with ALL on initial diagnosis. A significant cross-resistance among all the glucocorticoids used was found. Only in some individual cases the cross-resistance was less pronounced.

Uptake and efflux of two anthracyclines, idarubicin (IDA) and daunorubicin (DNR), was studied in childhood acute leukemia samples. A comparison of IDA and DNR transport phenomena in relation to drug cytotoxicity and expression of P-glycoprotein (PGP) was made. Intracellular content of IDA/DNR was determined by flow cytometry using the fluorescent properties of the drugs. In vitro drug cytotoxicity was measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. PGP expression was analysed by flow cytometry. The uptake and efflux rates were non-significantly higher for IDA than DNR. There were no differences between three types of leukemia with respect to drug content during accumulation and retention. After correction for the cell volume, intracellular concentration of both drugs in each moment of uptake and efflux was significantly lower in relapsed ALL and AML samples in comparison with initial ALL cells. Efflux, but not uptake, of both drugs was inversely correlated with PGP expression and IDA, but not DNR, cytotoxicity. The cytotoxicity was correlated with drug accumulation for both drugs and with drug retention for IDA. In conclusion, it seems that (1) intracellular content was related to the lipophilic properties of the drugs rather than to the type of leukemia, (2) decreased intracellular concentration of both drugs might have an impact on compromised therapy results in AML and relapsed ALL children, (3) IDA presents higher cytotoxicity, which possibly might be decreased by the presence of PGP. These results might have a practical impact on the rational design of new chemotherapy protocols.