Paradoxical behavior of 6-mercaptopurine as a cytotoxic agent: decreasing cell kill with increasing drug dose.

9L rat brain tumor cells were continuously exposed to "low" (2.9 microM) and "high" (18 and 35 microM) doses of 6-mercaptopurine (6-MP); cell kill was measured with a colony forming efficiency assay. The low dose of 6-MP killed more cells than the high doses, as measured by surviving fraction, when they were treated for greater than 48 hours.

Cytokinetic and cytotoxic effects of antimetabolites on 9L rat brain tumor cells in vitro.

Treatment of exponentially growing 9L monolayer cells with graded concentrations of methotrexate or 5-fluorouracil (5-FUra) resulted in approximately 95% cell kill, corresponding to the percentage of cells in this system labeled by autoradiography (98%). Additional cell kill could be obtained if 5-FUra was administered at a high concentration (7.7 x 10(-4) M) and could be partly reversed in the presence of 8.

The 9L rat brain tumor: description and application of an animal model.

Animal models allow determination of tumor response to anticancer agents under various experimental conditions. The chemically induced 9L rat brian tumor has been developed as both in vivo and in vitro models. Animal survival, clonogenic cell survival, and tumor growth delay provide means to measure the effectiveness of treatment modalities in this tumor model.

Effect of feeder cell-released substances on the survival of clonogenic 9L cells after treatment with antimetabolites.

Exponentially growing monolayer cultures of 9L rat brain tumor cells were treated with either 5-fluorouracil or methotrexate. The surviving fraction of cells was determined by a colony formation assay. After 5-fluorouracil treatment, 2 to 5 X 10(5) feeder cells were required to maximize surviving fractions for each drug concentration and to generate a biphasic dose-response curve.

Meningeal involvement in leukemias and malignant lymphomas of adults: incidence, course of disease, and treatment for prevention.

As prognosis has improved over the last several years, an increasing incidence of meningeal involvement has been recognized in adult patients with acute leukemias and malignant lymphomas. In 210 patients evaluated retrospectively, the incidence of meningeal disease was 33% for patients with acute lymphocytic leukemia (ALL), 20% for patients with acute myelogenous leukemia (AML), 22% for patients with non-Hodgkin's lymphomas with an unfavorable histology (NHL), 3% for patients with chronic myelogenous leukemia (CML), and 1% for patients with chronic lymphocytic leukemia (CLL). In most patients, meningeal involvement appeared several months after diagnosis of acute leukemia, often preceding systemic relapse if bone marrow remission had been achieved before.