Effects of folate deficiency on the metastatic potential of murine melanoma cells.

Experiments were designed to measure the effect of folic acid deficiency on a major determinant of cancer lethality, the propensity to form metastases. Murine B16 melanoma cells (F10 strain) were grown in folate-deficient and -supplemented media. After 3 days, cells in the deficient medium had restricted proliferative capacity, low folate levels by bioassay, increased cell volume, abnormal deoxyuridine suppression tests, accumulation of cells in S phase by flow cytometry, and increased numbers of DNA strand breaks. These folate-deficient cells consistently initiated more pulmonary metastases than control cells when injected into host mice. Cell size did not appear to be a major factor in pulmonary metastasis formation. In vitro growth rates and cloning efficiencies were comparable for cells in both types of medium as was subcutaneous growth of tumors. We conclude that folate deficiency increases the metastatic potential of cultured melanoma cells.

High-performance liquid chromatographic analysis of phosphorothioate analogues of oligodeoxynucleotides in biological fluids.

Phosphorothioate oligodeoxynucleotides (S-ODNs) have potential as anti-viral agents and are being investigated for the chemotherapy of AIDS. A high-performance liquid chromatographic method is described for the analysis, in urine and plasma, of a 28-unit deoxycytidine homopolymer (S-dC28) and a 28-unit S-ODN "antisense" to the rev gene of the human immunodeficiency virus. This method employs ion-pairing HPLC with a polymeric column. Tetrabutylammonium is used as the ion-pairing agent in a mobile phase of acetonitrile in pH 7.0 phosphate buffer. Analysis of the S-ODNs is relatively rapid (20 min) and sensitive (20 nm) and is accomplished by a gradient elution (22.5-30.0% acetonitrile) followed by ultraviolet (266 or 272 nm) absorption detection. This method is likely applicable, with appropriate modifications, to all S-ODNs of similar molecular weight regardless of sequence. The S-ODNs bind very strongly to plasma proteins but are readily prepared for analysis by a phenol extraction procedure. In a preliminary pharmacokinetic study in mice with S-dC28, very rapid elimination of the oligomer from plasma was observed (half-time, 11.6 min). Estimates for the apparent volume of distribution and total body clearance were 3 ml and 0.2 ml/min, respectively. It appears that the majority of the oligomer is eliminated by renal clearance (glomerular filtration), a property likely shared by all S-ODNs of similar molecular mass.