Melphalan transport, glutathione levels, and glutathione-S-transferase activity in human medulloblastoma

• Published in: Cancer research (Chicago, Ill.) Ill.), 1988-10, Vol.48 (19), p.5397-5402
• Main Authors: FRIEDMAN, H. S, SKAPEK, S. X, COLVIN, O. M, ELION, G. B, BLUM, M. R, SAVINA, P. M, HILTON, J, CLIFFORD SCHOLD, S. JR, KURTZBERG, J, BIGNER, D. D
• Format: Article
• Language: English
• Subjects: Animals; Antineoplastic agents; Biological and medical sciences; Brain Neoplasms - enzymology; Brain Neoplasms - metabolism; Cell Line; General aspects; glutathione; Glutathione - metabolism; glutathione transferase; Glutathione Transferase - metabolism; Humans; Kinetics; Medical sciences; Medulloblastoma - enzymology; Medulloblastoma - metabolism; Melphalan - pharmacokinetics; Mice; Neoplasm Transplantation; Pharmacology. Drug treatments; Sodium - pharmacology; Time Factors
• ISSN: 0008-5472; 1538-7445

Melphalan transport, glutathione levels, and glutathione-S-transferase activity were measured in two continuous human medulloblastoma cell lines and transplantable xenografts in athymic nude mice, TE-671 and Daoy. In vitro mean glutathione levels were 10.06 nmol/10(6) cells in TE-671 and 2.96 nmol/10(6) cells in Daoy. In vitro mean glutathione-S-transferase values were 91.52 nmol/min/mg protein in TE-671 and 50.31 nmol/min/mg protein in Daoy. Transport studies revealed kinetic parameters of Km = 108.3 microM, Vmax = 363.1 pmol/10(6) cells/min in TE-671 and Km = 111.7 microM, Vmax = 180.6 pmol/10(6) cells/min in Daoy. Melphalan transport was inhibited by both DL-alpha-2-aminobicyclo[2.2.1]heptane-2- carboxylic acid and sodium ion depletion in TE-671 and Daoy cells in vitro, indicating that both systems of amino acid transport are functional in these medulloblastoma lines. In vivo s.c. xenograft glutathione values were lower (7.79 nmol/mg protein) in TE-671 than in Daoy (13.68 nmol/mg protein). The mean plasma concentration in mice given a 10% lethal dose (71.3 mg/m2) of melphalan i.p. was 50.3 microM at 10 min, with the half-life of 29.9 min. At this dose, s.c. xenograft levels were 2- to 3-fold higher in TE-671 than in Daoy tumors for the 3-h period measured. These studies demonstrate transport parameters confirming facilitated transport of melphalan in human medulloblastoma, a mean murine plasma melphalan concentration (following treatment with melphalan) above the in vitro drug dose at which there is a 90% reduction in the number of colonies in comparison to controls for TE-671 and Daoy for 2 h, and glutathione and glutathione-S-transferase levels in the same range previously reported in other melphalan-sensitive and melphalan-resistant human tumors. Future work with spontaneous and acquired melphalan-resistant human medulloblastoma cell lines and xenografts will define the role of these mechanisms in mediating drug resistance.