Synergistic cytotoxicity of buthionine sulfoximine (BSO) and intensive melphalan (L-PAM) for neuroblastoma cell lines established at relapse after myeloablative therapy.
Patients with high-risk neuroblastoma (NB) initially respond to aggressive, alkylator-based therapy only to die from recurrent disease that is refractory to chemotherapy, including alkylating agents. We examined the ability of buthionine sulfoximine (BSO)-mediated glutathione (GSH) depletion to modulate melphalan (L-PAM) resistance in five NB cell lines established after progressive disease following myeloablative therapy (high-dose melphalan, carboplatin, etoposide and total body irradiation) supported by autologous hematopoietic stem cell transplant (AHSCT), and in 15 NB cell lines established at diagnosis or after non-myeloablative therapy (pre-AHSCT). Four of five post-AHSCT NB cell lines and 10 of 15 pre-AHSCT NB cell lines were sensitive to single agent BSO (LC(90) <300 microM BSO), while two of five post-AHSCT lines and one of 15 pre-AHSCT lines showed high-level resistance to L-PAM (LC(90)>30 microM). Fixed ratio analysis demonstrated BSO/L-PAM synergy (combination index <1) for all five post-AHSCT and for all 15 pre-AHSCT cell lines tested. Multi-log cytotoxicity (often exceeding four logs of cell kill) was observed in post-AHSCT L-PAM-resistant cell lines (including p53 non-functional lines) only when clinically achievable concentrations of BSO were combined with myeloablative concentrations of L-PAM. We conclude that most neuroblastoma cell lines, including post-AHSCT NB cell lines that are highly resistant to myeloablative levels of L-PAM and lack p53 function, are sensitive to clinically achievable concentrations of L-PAM and BSO. However, some L-PAM-resistant NB cell lines (especially those lacking p53 function) require dose escalation of L-PAM to myeloablative concentrations in order to demonstrate significant synergistic cytotoxicity. Thus, optimal clinical application of BSO/L-PAM may require AHSCT.
Division of Hematology-Oncology, Childrens Hospital Los Angeles, CA 90027, USA.
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Anderson
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Reynolds
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D019328:Buthionine Sulfoximine / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005978:Glutathione / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008558:Melphalan / Q000494:pharmacology*; D019653:Myeloablative Agonists / Q000627:therapeutic use*; D009447:Neuroblastoma / Q000188:drug therapy* / Q000473:pathology; D012008:Recurrence; D014407:Tumor Cells, Cultured
D019653:Myeloablative Agonists; D019328:Buthionine Sulfoximine; D005978:Glutathione; D008558:Melphalan