Cyclosporin A potentiation of VP-16: production of long-term survival in murine acute lymphatic leukemia

Retinoblastoma CSF metastasis cured by multimodality chemotherapy without radiation

OBJECTIVE

Cerebrospinal fluid (CSF) metastasis is the most difficult type of retinoblastoma metastasis to cure, even with bone marrow transplant. Most metastatic retinoblastoma cells express P-glycoprotein causing multidrug resistance (MDR). P-glycoprotein-rich blood vessels form blood-brain and blood-eye barriers, inhibit drug entry into central nervous system (CNS) and eyes. High-dose craniospinal radiation is too morbid for treatment of young children. To cure CSF metastasis without radiation, we designed an intensive multimodality chemotherapy regimen.

METHOD

After left eye enucleation, a 4-month-old boy with bilateral International Intraocular Retinoblastoma Classification Group E eyes and CSF metastasis was treated with 7-cycle high-dose carboplatin and etoposide, standard-dose vincristine, and high-dose/short-infusion cyclosporine to inhibit P-glycoprotein. Intraventricular drugs, non-substrate of P-glycoprotein (cytarabine), or less susceptible to MDR (topotecan), contributed to treatment of the metastasis. On achieving complete response, he was consolidated with supralethal-dosage carboplatin, etoposide, and cyclophosphamide, and his bone marrow rescued with autologous cord blood stem cells.

RESULTS

Following 1-cycle systemic chemotherapy and 2-dose intraventricular chemotherapy, the CSF metastasis cleared. The right eye tumor regressed completely. The patient remains in remission 8.3 years after diagnosis and 7.8 years post-transplant.

CONCLUSION

Intensive multimodality chemotherapy can cure CSF metastasis in retinoblastoma without incurring extreme morbidity from craniospinal radiation.

Comparison of cyclosporin A, verapamil, PSC-833 and cremophor EL as enhancing agents of VP-16 in murine lymphoid leukemias

Although verapamil, cyclosporin A. cremophor EL and PSC-833 are active as multidrug resistance modulators, there has been limited study of these compounds as possible chemotherapy enhancing agents against drug-sensitive tumors. We compared these agents as modifiers of VP-16 cytotoxicity in vitro and modifiers of VP-16 efficacy in vivo against drug-sensitive P388 and L1210 leukemias. Our study indicates that cyclosporin A enhances VP-16 cytotoxicity to a significantly greater extent than equimolar concentrations of verapamil or PSC-833. Although cremophor EL shows significantly greater activity than verapamil in VP-16 cytotoxicity enhancement in vitro, it is ineffective when added to VP-16 therapy of mice bearing L1210 leukemia.

Lymphotoxicity and myelotoxicity of doxorubicin and SDZ PSC 833 combined chemotherapies for normal mice

In the mouse, the P-glycoprotein-directed chemosensitizer SDZ PSC 833 could both restore a therapeutic window for doxorubicin against multidrug-resistant tumors, by inhibiting P-glycoprotein function, and increase the anti-cancer drug efficacy against drug-sensitive tumors, by increasing doxorubicin bioavailability. Since the success of such combined chemotherapy treatments might have been limited by the myelotoxicity of doxorubicin and the P-glycoprotein expression on some blood cells, their lymphotoxicity and myelotoxicity was studied on normal B6D2F1 mice, and whenever possible, the persistence of blood cell alterations was also searched for in scid recipients of lymphohaematopoietic grafts from the donor mice. Analyzed parameters were blood, lymphoid and myeloid cell numbers, proliferative responses to T- and B-cell mitogens, and serum immunoglobulin levels. Cell alterations caused by doxorubicin alone were potentiated by SDZ PSC 833, but did not persist in scid recipients. Chemotherapy regimens combining SDZ PSC 833 and doxorubicin, and known for their therapeutic benefit for multidrug-resistant tumor-bearing mice, only caused a rather mild toxicity for the lympho-myeloid system of normal mice.