Correlation of P-glycoprotein expression and function in childhood acute leukemia: a children's cancer group study

Clinical drug resistance may be attributed to the simultaneous selection and expression of genes modulating the uptake and metabolism of chemotherapeutic agents. P-glycoprotein (P-gp) functions as a membrane-associated drug efflux pump whose increased expression results in resistance to anthracyclines, epipodophyllotoxins, vinca alkaloids, and some alkylating agents. This type of resistance occurs as both de novo and acquired resistance to therapy for leukemia. We have studied P- gp expression and function in childhood acute leukemias by developing a series of doxorubicin- and vincristine-selected CEM, T-cell lymphoblastoid cell lines that recapitulate the low levels of expression and resistance seen clinically. These cell lines have been used to develop flow cytometric assays for the semiquantitative measurements of P-gp expression with the MRK16 monoclonal antibody and P-gp function using the enhanced retention of rhodamine 123 in the presence of verapamil, a resistance modulator. Kolmogorov-Smirnov statistics, represented by the D measurement, are used to determine the difference in level of P-gp expression by comparing MRK16 staining to an IgG2a isotype control. When D is > 0.09, there is an excellent correlation (R = 0.82) between P-gp expression and function. The evaluation of 107 bone marrow specimens from 84 children with lymphoblastic or myelogenous leukemia showed a statistically significant (P = .004) increase in P-gp function at relapse. P-gp expression at relapse, however, approached but did not reach a significant level (P = .097). Using this methodology, we can identify patients with levels of P-gp expression and function that we can define clinically, as well as children with discordant multidrug resistance phenotypes. This study supports the role of P-gp-mediated drug resistance in childhood leukemia and confirms that P-gp expression and function are measurable in their leukemic blasts. These assays provide the means for the in vitro testing of resistance modulators and the monitoring of in vivo response to treatment with these agents.     

Quantitation of platelet-associated IgG by radial immunodiffusion

Platelet-associated IgG (PAIgG) was measured by a simple radial immunodiffusion technique using washed solubilized platelets and commercially available immunoplates. Subjects with normal platelet counts had PAIgG levels of 1.5--7.0 fg/platelet. Subjects with idiopathic immune thrombocytopenic purpura (ITP) had levels ranging from 5.7 to 70.5 fg/platelet. All patients with recurrent ITP and 85% of patients with acute ITP had elevated PAIgg. Elevated PAIgG was also found in 17% of patients with recovered ITP, 40% of patients with SLE and thrombocytopenia, 57% of patients with thrombocytopenia occurring during the course of septicemia, and 100% of patients with IgG myeloma in whom the serum IgG level was clearly elevated, regardless of the platelet count. The results are similar to reports that used more complex techniques.     

Plastic bronchitis and the role of bronchoscopy in the acute chest syndrome of sickle cell disease

STUDY OBJECTIVES: To review the prevalence, clinical features, and role of bronchoscopy in patients with plastic bronchitis during the acute chest syndrome (ACS) of sickle cell disease (SCD). DESIGN: Eight-year review of clinical experience. SETTING: Tertiary referral children's hospital. PATIENTS: Twenty-six pediatric inpatients with 29 ACS episodes requiring diagnostic bronchoscopy. RESULTS: Of the pediatric inpatients with ACS who underwent bronchoscopy, plastic bronchitis was diagnosed in 21 of 29 episodes (72%). There was no difference in clinical features between the patients with and without plastic bronchitis. Bronchoscopy was an essential diagnostic tool, but its therapeutic benefits were doubtful. CONCLUSIONS: This is the first report of the prevalence of plastic bronchitis in patients with ACS of SCD. In our patient population, this condition was found to be common. The role of diagnostic bronchoscopy is essential. A large series, multicenter study is required to determine whether bronchoscopy and BAL are therapeutically beneficial when added to currently practiced supportive care.     

Treatment of toxoplasmic encephalitis in patients with AIDS. A randomized trial comparing pyrimethamine plus clindamycin to pyrimethamine plus sulfadiazine. The California Collaborative Treatment Group.

OBJECTIVE: To compare pyrimethamine plus clindamycin (PC) to pyrimethamine plus sulfadiazine (PS) as a treatment for toxoplasmic encephalitis (TE) in patients with the acquired immunodeficiency syndrome (AIDS). DESIGN: Randomized, unblinded phase II, multicenter trial with provision for crossover for failure or intolerance of the assigned regimen. SETTING: University hospitals. PATIENTS: Eighty-four patients with presumptive TE were entered. Thirteen were excluded when they were found to have another diagnosis, and 12 were excluded because they did not meet entry criteria. The baseline characteristics in the remaining 26 patients randomized to PC and 33 randomized to PS were comparable. INTERVENTIONS: Patients were treated for 6 weeks with pyrimethamine and folinic acid plus either sulfadiazine or clindamycin. Clindamycin was given intravenously during the first 3 weeks. MEASUREMENTS AND MAIN RESULTS: There was a trend toward greater survival in patients randomized to PS (hazard ratio, 3.25; 95% CI, 0.63 to 16.8; P = 0.13), but most study deaths were not directly related to TE. In contrast, patients randomized to PC appeared more likely to achieve complete clinical (odds ratio, 0.67; CI, 0.2 to 1.97; P greater than 0.2) and radiologic responses (odds ratio, 0.28; CI, 0.08 to 0.96; P = 0.02). Multivariate analysis revealed drug effects to be largely independent of other variables. Similar efficacy of the treatments was also suggested by a hazard analysis of resolution of abnormal mental status, fever, and headache. Skin rash was the most common adverse event in both treatment arms. Because of toxicity, six patients randomized to PC and 11 patients randomized to PS had to switch to the alternate treatment, but only three were unable to complete therapy after crossover. CONCLUSIONS: The results of several end points of efficacy, taken together, suggest that the relative efficacy of PC approximately equals that of PS. PC appears to be an acceptable alternative in patients unable to tolerate PS.     

A method for simultaneous study of the karyotype, morphology, and immunologic phenotype of mitotic cells in hematologic malignancies

A major problem in the cytogenetic analysis of hematologic neoplasms has been an inability to identify the cell from which the chromosomes were obtained. We describe a procedure that allows simultaneous analysis of karyotype and cell cytology in mitotic cells. The method differs from conventional cytogenetic analysis in that after mild hypotonic treatment, the cells are cytocentrifuged onto glass slides. In mitotic cells, this procedure often results in adequate spread of the chromosomes within the intact cell membrane. The cytoplasmic structure also remains intact, so that cytologic preparations are of good quality. Morphologic and immunologic identification of mitotic cells can be done using routine hematologic stains, such as Giemsa or Sudan black B, and various antisera using immunofluorescence techniques. The chromosomes can be simultaneously analyzed either without banding on slides stained with Giemsa or with Q-banding on slides stained with immunofluorescence techniques. Identification of numerical and structural karyotype aberrations thus is possible in morphologically identified cells.     

Resolution of Corticosteroid-Induced Diabetes in Allergic Bronchopulmonary Aspergillosis with Omalizumab Therapy: A Novel Approach

There are substantial numbers of reports showing that leukotrienes (LTs) play important roles in adult asthma. No definite evidence has been demonstrated that LTs are involved in asthma attacks in children, although it is highly expected. In this report, we demonstrated that the levels of LTB₄ and LTC₄ but not thromboxane B₂ (TXB₂), a stable metabolite of TXA₂, were significantly elevated in the bronchoalveolar lavage fluid, which was obtained from intubated and mechanically ventilated children with severe asthma attacks. This is direct evidence that LTB₄ and LTC₄ predominantly participate in asthma attacks in pediatric patients.