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Biomedical subjects

B A Chabner

Publications and source records attributed to B A Chabner.

At least 145 records · Page 8Linked to original sources
PubMed1982

Malignant lymphoma. 1. The histology and staging of 473 patients at the National Cancer Institute.

A retrospective review was performed of 473 consecutive patients with malignant lymphoma referred to the National Cancer Institute. All patients had their clinical and pathologic material reviewed and where necessary reclassified. Using a modification of the Rappaport system, 180 (38.1%) patients had a nodular lymphoma, 293 (61.9%) had a diffuse lymphoma. Nodular lymphoma patients usually presented with lymphadenopathy; diffuse lymphoma patients often presented with extranodal disease, particularly those patients with poorly differentiated lymphocytic, "histiocytic", and Burkitt's lymphoma. Median age for all patients was 46 years, but was lower for diffuse poorly differentiated lymphocytic, diffuse undifferentiated, and Burkitt's lymphoma patients. Women were more likely to have a nodular rather than diffuse lymphoma. P less than 0.05. Analyzed by clinical staging, most nodular lymphoma patients had CS III (66.1%) disease, while most diffuse lymphoma patients had either CS III (31.1%) or CS IV (38.9%) disease. Analyzed by pathologic staging, most nodular lymphoma patients had PS III (34.8%) or PS IV (49.4%) disease, most diffuse lymphoma patients had PS IV (56.3%) disease. Only 7% of all lymphoma patients had PS I disease, only 14.9% were PS II. Systemic symptoms were more likely to be found in diffuse lymphoma and/or advanced stage patients.

Burkitt Lymphoma↗
PubMed1982

Synthesis, retention, and biological activity of methotrexate polyglutamates in cultured human breast cancer cells.

To determine the pharmacologic importance of methotrexate (MTX) polyglutamates, we examined the formation, retention, and effect of these metabolites in cultured human breast cancer cells. Two cell lines (MCF-7 and ZR-75-B) converted the drug to gamma-polyglutamate derivatives in a dose- and time-dependent reaction. After 24-h incubations with 2 muM MTX, polyglutamates of two to five amino acids in length accounted for 55.4% (51.9 nmol/g) of intracellular drug in the MCF-7 cells and 87.6% (62.4 nmol/g) of drug in ZR-75-B cells. In contrast, MDA-231 cells showed lesser accumulation of MTX, and only 32% (4.06 nmol/g) of the intracellular drug was in the form of polyglutamates, a difference that could only partially be explained by decreased ability of these cells to take up free drug from the medium. When MCF-7 and ZR-75-B cells containing polyglutamates were transferred to drug-free medium for 24 h, 22 and 51% of the total intracellular drug were, respectively, retained in each cell line. The loss of intracellular drug was primarily accounted for by disappearance of parent compound and polyglutamates containing 1-3 additional glutamyl residues. The rates of disappearance from cells decreased with increasing glutamyl chain length. All of the 4-NH(2)-10-CH(3)-PteGlu(5) and 47 and 38% of the 4-NH(2)-10-CH(3)-PteGlu(4) remained in the MCF-7 and ZR-75-B cells, respectively, and could be identified in the cytosol after 24 h in drug-free medium. The retention of MTX polyglutamates in these two cell lines in excess of dihydrofolate reductase binding capacity led to prolonged inhibition of thymidylate synthesis and loss of cell viability after removal of extracellular MTX. After 24-h incubation with 2 muM MTX and an additional 24 h in drug-free medium, [(3)H]deoxyuridine incorporation was still inhibited to 30% of control in the MCF-7 cells and 34.7% of control in ZR-75-B cells; this persistent inhibition was associated with a 30% reduction in cell numbers in each cell line during the 24-h period in drug-free medium. In contrast, [(3)H]deoxyuridine incorporation and cell growth quickly recovered to normal in the MDA-231 cells following removal of 2 muM MTX from the medium after a 24-h incubation. Prolonged inhibition of both thymidylate synthesis and cell growth was observed in this cell line in drug-free medium only after a 24-h incubation with 10 muM MTX, a condition that leads to the synthesis of 11.3 nmol/g of MTX polyglutamates. These studies demonstrate that polyglutamate formation allows a prolonged retention of drug in a noneffluxable form and prolonged inhibition of both thymidylate synthesis and cell growth following removal of extracellular drug.

Breast Neoplasms↗
PubMed1982

Phase I-phase II trial of N-phosphonacetyl-L-aspartic acid given by intravenous infusion and 5-fluorouracil given by bolus injection.

A phase I clinical trial of N-phosphonacetyl-L-aspartic acid (PALA) and 5-fluorouracil (FUra) was performed on 30 patients. PALA was given as a 15-minute iv infusion once daily for 5 days, and FUra was given as a bolus injection on days 2, 3, 4, and 5. Cycles of treatment were repeated every 3 weeks. Dose-limiting toxicity was manifested by stomatitis and diarrhea. Skin rash was observed also but was not dose limiting. No consistent hematopoietic or renal toxicity was observed. Seventeen patients with disseminated metastatic melanoma and measurable disease were evaluated for response. One partial response was seen; however, the response was associated with significant toxicity, and the treatment could not be repeated. Stable disease was observed in 3 patients with melanoma, 1 patient with colon carcinoma, and 1 patient with ovarian carcinoma. Our findings suggest that the clinical activity of PALA and FUra given according to the above schedule for melanoma is less than 25% (P less than 0.05). Pharmacokinetic studies of FUra revealed no consistent effect of PALA pretreatment on FUra disappearance in plasma. The mean FUra elimination half-line in plasma was 7.11 +/- 0.84 minutes (SEM), which is no different from that reported for FUra alone. The recommended doses on this schedule for phase II studies are 1,000 mg PALA/m2/day iv daily for 5 days and 200 mg FUra/m2/day iv on days 2, 3, 4, and 5.

Adult↗
PubMed1981

Postchemotherapy purine excretion in lymphoma patients receiving allopurinol.

The urinary excretion of hypoxanthine, xanthine, and uric acid was measured prior to and following chemotherapy in 11 patients with rapidly growing chemotherapy-sensitive lymphomas who were receiving concomitant allopurinol therapy. Mean maximal total dairy urinary excretions of these purines postchemotherapy were: uric acid, 807 mg/day; hypoxanthine, 343 mg/day; and xanthine, 638 mg/day. The mean maximal postchemotherapy urinary concentrations of uric acid, hypoxanthine, and xanthine were 288, 115, and 179 mg/liter, respectively. Mean total daily urinary excretion of uric acid, hypoxanthine, and xanthine rose 2.2-, 6.6-, and 6.9-fold, respectively, following initiation of antineoplastic therapy. Although standard doses of allopurinol did not prevent a postchemotherapy increase in the excretion of uric acid or hypoxanthine, the urinary concentrations of both compounds remained below their solubility in urine at pH 7 in all 11 patients studied. However, the urinary concentration of xanthine exceeded its solubility in urine at pH 7 in six of the 11 patients. In three of the six patients whose urinary concentration of xanthine concentration exceeded its solubility in urine, transient renal failure developed in association with the increased excretion of xanthine. These studies indicate that, despite the use of conventional doses of allopurinol, the urinary excretion of uric acid may still increase following massive tumor lysis, and urinary excretion of xanthine can increase to concentrations potentially causing xanthine nephropathy.

Acute Kidney Injury↗
PubMed1980

Methotrexate polyglutamate synthesis by cultured human breast cancer cells.

We studied the conversion of methotrexate to poly-gamma-glutamyl derivatives by cultured human breast cancer cells. After incubation with 2 micro M [3',5',9-3H]methotrexate, MCF-7 cells were washed free of extracellular drug and were boiled to lyse cells and to release drug bound to dihydrofolate reductase (tetrahydrofolate dehydrogenase; 5,6,7,8-tetrahydrofolate:NADP+ oxidoreductase, EC 1.5.1.3). The supernatant fraction was chromatographed on Sephadex G-15 to separate parent drug from polyglutamate forms. These cells rapidly and quantitatively converted methotrexate to polyglutamates, such that after 24 hr of incubation, 70 +/- (SEM) 3% of intracellular methotrexate existed as polyglutamates. Examination of that portion of intracellular methotrexate specifically bound to dihydrofolate reductase indicated that, with prolonged incubation, methotrexate polyglutamates become the predominant drug form bound to the enzyme. These studies demonstrate that methotrexate polyglutamates are readily formed in human tumor cells and bind to dihydrofolate reductase. Because these forms of the drug may be selectively retained within the cell, they may be important determinants of the duration of action and, ultimately, the cytotoxicity of methotrexate in human solid tumors.

Breast Neoplasms↗
PubMed1980

Application of a simple competitive protein-binding assay technique to the pharmacokinetics of N-(phosphonacetyl)-L-aspartate in humans.

A competitive protein-binding assay for N-(phosphonacetyl)-L-aspartate (PALA) using aspartate transcarbamylase as the receptor protein and [14C]PALA as the radioactive ligand is described here and has been applied to study the pharmacokinetics of PALA in humans. A protein-free ultrafiltrate of plasma, prepared by centrifugation of 1-ml samples through Amicon Centriflo membrane cones, was used in the assay, which had a maximun sensitivity of 0.7 microM PALA in plasma. At this level, the coefficient of variation was less than 10%. Comparison of the competitive binding assay to a gas chromatographic-mass spectrometric technique shows that the two methods yield equivalent results in the concentration range of 1 microM to 1 mM. However, the competitive binding assay possesses practical advantages because of its simplicity and the ease with which multiple samples may be assayed. PALA disappearance from plasma was studied in seven patients and was found to be consistent with a two-compartment open model. The t1/2 alpha (elimination half-life for initial phase) and t1/2 beta (elimination half-life for terminal phase) were 0.93 +/- 0.73 (S.D.) hr and 4.82 +/- 1.48 hr, respectively. The cumulative urinary excretion of PALA int two patients was 70 and 90% of the administered dose 16 hr after the infusion was completed.

Aspartate Carbamoyltransferase↗