Antileukemic activity and mechanism of action of cordycepin against terminal deoxynucleotidyl transferase-positive (TdT+) leukemic cells.

The nucleoside analogue cordycepin (3'-deoxyadenosine, 3'-dA) is substantially more cytotoxic to terminal deoxynucleotidyl transferase positive (TdT+) leukemic cells than to TdT leukemic cells in vitro in the presence of an adenosine deaminase inhibitor, deoxycoformycin (dCF), and has been considered as a therapeutic agent for TdT+ leukemia. The intracellular metabolism of 3'-dA was examined with HPLC, and the mechanism of its anti-TdT+ leukemic activity was analyzed. In the presence of dCF (2.5 microM), TdT+ leukemic cells (N = 5) were sensitive to the cytotoxic effect of 3'-dA, whereas TdT (N = 6) cells were not. A high level of 3'-dA-5'-triphosphate (3'-dATP) formation was detected in TdT+ NALM-6 cells (67 pmol/10(6) cells) and TdT- K562 cells (49 pmol/10(6) cells) when cultured with 1 microM [3'-3H]-labeled 3'-dA. A substantial level of 3'-dATP was detected in TdT HUT-102 cells (27 pmol/10(6) cells), whereas the level of 3'-dATP in TdT+ MOLT-4 cells was low (0.3 pmol/10(6) cells). The mean IC50 values of 3'-dA against phytohemagglutinin (PHA)-activated and resting peripheral blood mononuclear cells (PBM) (N = 5) were 8 and 32 microM, respectively. There was a modest level of 3'-dATP (7 pmol/10(6) cells) in PHA-PBM, whereas a lower level of 3'-dATP was detected in resting PBM (2.5 pmol/10(6) cells). These data suggest that the presence of 3'-dATP is not sufficient for the antileukemic effect of 3'-dA, but that TdT positivity is essential, and that PBM are significantly less sensitive to the cytotoxicity of 3'-dA in vitro. Further development of 3'-dA as a potential antileukemic agent to treat patients with TdT+ leukemia is warranted.

Antifungal activity of 3'-deoxyadenosine (cordycepin).

The antifungal activity of the nucleoside analog 3'-deoxyadenosine (cordycepin) was studied in a murine model of invasive candidiasis. When protected from deamination by either deoxycoformycin or coformycin, both of which are adenosine deaminase inhibitors, cordycepin exhibited potent antifungal efficacy, as demonstrated by prolongation of survival and a decrease in CFU in the kidneys of mice treated with cordycepin plus an adenosine deaminase inhibitor. The antifungal effect was seen with three different Candida isolates: Candida albicans 64, a relatively fluconazole-resistant clinical isolate of C. albicans (MIC, 16 micrograms/ml), and the fluconazole-resistant Candida krusei. Cordycepin and related compounds may provide another avenue for the discovery of clinically useful antifungal drugs.

The secondary leukemias: challenges and research directions.

Acute myelogenous leukemia (AML) arising following exposure to genotoxic agents has been recognized as a distinctive entity for more than 40 years. Secondary, or therapy-related, AML accounts for 10%-20% of all AML cases. This review addresses four overarching areas of investigation focused on secondary AMLs: 1) dissection of the molecular structure of the induced genetic lesions and identification of the functional consequences of these changes, thereby providing clues to the pathogenesis of secondary AML and potentially serving as a basis for innovative therapeutic interventions; 2) identification and characterization of mechanisms of DNA damage and the orderly repair of such damage; 3) identification and application of accurate biomarkers of leukemogenesis for the purpose of risk prediction and quantification, potentially allowing recognition of patients especially susceptible to the leukemogenic effects of chemotherapy (for genetic or acquired reasons) and allowing their treatment for cancer to be modified on the basis of this susceptibility; and 4) design and implementation of longitudinal clinical and genetic monitoring of high-risk populations (i.e., individuals under-going cytotoxic therapies for primary cancers). This review of the literature relating to these areas builds upon these themes and attempts to synthesize these seemingly disparate areas of research so that they can be more effectively utilized together to address the problem of secondary AML. Ultimately, the evaluation of these areas will improve our understanding of de novo leukemia and will serve as a springboard for the development of new concepts of therapy and prevention.

New avenues of translational research in leukemia and lymphoma: outgrowth of a Leukemia Society of America-National Cancer Institute workshop.

The workshop was organized on the premise that truly innovative approaches are needed if we are to significantly change the clinical outcomes for leukemias and lymphomas. Several new concepts and pioneering approaches surfaced during the workshop discussions, as summarized above. The design and implementation of translational clinical trials that emphasize these innovative strategies were encouraged as a way to test the concepts put forward at the workshop. Representatives of the Leukemia Society of America and the National Cancer Institute plan to continue their dialogue to develop recommendations regarding the priorities for linked clinical-laboratory investigations on the hematopoietic malignancies and the optimal ways in which to foster such translational research. To this end, the explosion in basic science discoveries during the last two decades and especially during the last 5 years is producing a critical mass of knowledge. This knowledge, in turn, allows us to view leukemia from new perspectives that span molecular pathogenesis, epidemiology, early detection of minimal disease, and the selective targeting of critical leukemogenic mechanisms for therapeutic and ultimately preventive purposes. As in previous decades, during which leukemia has served as the testing ground for precedent-setting concepts of curative therapy (dose-intensity, non-cross-resistance-inducing combinations and aggressive therapy in the minimal residual disease state), leukemia should again serve as a clinical beacon for the identification and exploitation of new molecular targets for therapy. Any impact on curability and duration and quality of survival will be achieved only by building on the cumulative knowledge accrued at multiple levels--molecular and cellular levels as well as in the intact patient--and augmenting the momentum of the bidirectional exchange of information between the laboratory and the clinic that has characterized leukemia research from its incipience. The challenge is formidable and worthy of our most creative and concerted efforts.

Treatment of malignant pleural mesothelioma with cisplatin, mitomycin C and alpha interferon.

From October 1990 to September 1991, 20 consecutive patients with histologically proven malignant pleural mesothelioma (MPM), secondary to environmental exposure to asbestos or erionite, were treated with cisplatin, mitomycin C and alpha interferon (cisplatin 50 mg/m2 i.v. on day 1 of a 21-day cycle; mitomycin C 10 mg/m2 i.v. day 1 of cycles 1,3 and 5; alpha-2b-interferon 10 x 10(6) units i.m., 4 h prior to cisplatin and 10 x 10(6) units i.v. immediately prior to cisplatin day 1 of each cycle). Eighty-two treatment cycles were administered to 19 evaluable patients. Two patients attained a partial response. Eleven patients had stable disease and 6 had disease progression. Toxicities included interferon-related fever and flu-like symptoms, and vomiting. Actuarial median survival was 15 months. Three patients are alive at 20+, 21+ and 27+ months. We conclude that while the addition of alpha interferon to cisplatin and mitomycin C did not result in an objective response higher than previously reported with the cytotoxic agents alone, the trend towards an improvement in median survival as compared to a well-matched historical group suggests some benefit from the inclusion of interferon.

Treatment of AIDS and AIDS-related complex with 2',3'-dideoxyinosine given once daily.

In a phase I dosage-finding trial, 2',3'-dideoxyinosine (didanosine; ddI) was administered once daily to 36 patients with AIDS or AIDS-related complex for up to 65 weeks (mean, 32.1 weeks) at six dosage levels. Thirteen of 18 patients previously treated with zidovudine had developed hematologic intolerance. The maximal tolerated dosage of ddI was 12 mg/(kg.d); dose-limiting toxicities were pancreatitis and peripheral neuropathy. Other toxicities included elevation in hepatic transaminase levels, rash, cardiac conduction abnormality, and asymptomatic hyperuricemia. Eighty-six percent of patients who completed 6 weeks of treatment showed improvement in constitutional symptoms and significant weight gain. In patients treated with ddI, the mean number of CD4+ lymphocytes increased from 124/mm3 at baseline to 199/mm3 at 24 weeks (P = .0027) and the mean leukocyte count, total lymphocyte count, and hemoglobin level showed increases (all P less than .01) after 12 weeks. Serum levels of viral p24 antigen decreased greater than or equal to 50% in 14 of 19 assessable patients. No differences between the responses of patients previously treated with zidovudine and those of zidovudine-naive patients were observed. These results indicate that ddI has significant antiretroviral activity in vivo and a toxicity profile different from that of zidovudine.

Chemotherapy screening assay using 3-dimensional cell culture.

A new alginate culture method (ACM) was used to test the effects of vincristine and 5-fluorouracil (5-FU) on the commonly used human colon carcinoma cell line HT-29. Colorimetric analysis of viability following treatment with physiologically tolerated levels of vincristine showed significant reduction of the surviving cell population. Hematoxylin and eosin staining of sections of treated organoid growths corroborated the colorimetric analyses. The ACM is inexpensive, rapid and extremely versatile. Many alginate beads containing "mini-tissue" growths of many cell lines can be used simultaneously to evaluate numerous chemotherapeutic agents in an "in vivo-like" environment.

Once-daily administration of 2',3'-dideoxyinosine (ddI) in patients with the acquired immunodeficiency syndrome or AIDS-related complex. Results of a Phase I trial.

We conducted a Phase I open-label trial of 2',3'-dideoxyinosine (ddI) for the treatment of the acquired immunodeficiency syndrome (AIDS) and severe AIDS-related complex. A single daily dose of ddI was administered orally to 34 patients (17 with AIDS and 17 with AIDS-related complex) for a median of 12 weeks (range, 2 to 56). We studied six dose levels from 1.6 to 30.4 mg per kilogram of body weight per day. Of the 17 patients previously treated with zidovudine, 13 had had hematologic side effects. The maximal tolerated dose of oral ddI was estimated to be 20.4 mg per kilogram per day. Pancreatitis and peripheral neuropathy were the major dose-limiting toxic effects. Other toxic effects included elevations in hepatic transaminase levels, abnormalities in cardiac conduction, rash, and asymptomatic elevations in serum urate levels and the creatine kinase fraction from skeletal muscle. Treatment with ddI was associated with an increase in the mean number of CD4 lymphocytes from 125 per cubic millimeter at base line to 182 per cubic millimeter after 10 weeks (P = 0.005). There were also increases after 12 weeks in the mean total lymphocyte count (from 0.8 to 1.2 x 10(9) per liter) and the mean hemoglobin level (from 12.9 to 14.1 g per deciliter) (both P less than 0.01). The amount of human immunodeficiency virus p24 antigen decreased by more than 50 percent in 14 of 19 patients with detectable antigen. No differences in response were observed between patients previously treated with zidovudine and those never treated with the drug. We conclude that ddI has antiretroviral activity in patients with AIDS or AIDS-related complex and that the toxicity of ddI differs from that of zidovudine. However, controlled trials are necessary to evaluate the efficacy of ddI.

Spurious detection of terminal deoxynucleotidyl transferase in phytohemagglutinin-stimulated lymphocytes.

Expression of terminal transferase (TdT) is believed to be restricted to primitive lymphoid cells; recently, however, indirect immunofluorescent (IF) assays have been used to demonstrate the apparent presence of TdT in phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes and in various nonlymphoid malignancies. Using an IF assay, we found that a heteroantiserum to TdT reacted with cultured and PHA-stimulated human peripheral blood mononuclear cells, but we were unable to confirm the presence of TdT in these cells using immunoblotting and biochemical assays. We conclude that the IF results are spurious and most likely represent recognition by the heteroantiserum of inducible protein(s) other than TdT.

Eosinophilic cytoplasmic inclusions in fetal leukocytes: are Auer bodies a recapitulation of fetal morphology?

Among the most striking morphological features of acute nonlymphoblastic leukemias (ANLL) is the occurrence of eosinophilic cytoplasmic inclusions known as Auer rods on Auer bodies. We examined immature myeloid cells from the peripheral blood of 9 human fetuses of 16-19 wk gestation for the presence of such structures. Five of these 9 samples contained cytoplasmic inclusions, which were identical to the Auer rods typically seen in blast cells from patients with ANLL. The incidence of positive cells was low (1-5 cells/10,000 cells surveyed). The inclusions were azurophilic with Wright-Giemsa staining and were cytochemically positive with peroxidase, acid phosphatase, and Sudan black staining. We observed no inclusions in identically prepared control myeloid cells from the bone marrow of 5 patients with acute lymphoblastic leukemia in remission and 3 patients with chronic myelogenous leukemia in stable phase. Nor were they present in peripheral blood myeloid cells of 10 normal adults. Myeloid precursors in long-term bone marrow culture from 2 normal adult donors did not develop the inclusions during 24 hr of incubation with prostaglandin F2 (the abortifacient). These observations suggest that Auer rod formation is an occasional but normal phenomenon in fetal hematopoiesis.

Abnormal histamine-induced suppressor-cell function in atopic subjects.

To detect a potential defect in immunoregulatory function in atopic subjects, we studied histamine-induced suppressor-T-cell activity and histamine Type 1 and Type 2 receptors on T cells. Peripheral-blood mononuclear cells from 16 atopic subjects generated less histamine-induced suppressor activity than did those from 20 nonatopic normal controls (P less than 0.005). The percentage of T lymphocytes bearing histamine Type 2 receptors was lower in the atopic group than in the control group (P less than 0.001), but the percentage of cells with Type 1 receptors was the same in both groups. In the atopic subjects, the functional suppressor-cell abnormality positively correlated with the decreased phenotypic expression of histamine Type 2 receptors. No abnormality in concanavalin A-induced suppressor activity was detected in these subjects. Nonatopic control subjects with systemic mastocytosis had normal functional and phenotypic data, suggesting that chronic activation of atopic T cells in vivo by circulating histamine does not explain the abnormal histamine-induced suppressor response.

Characterization of the inhibitory effects of the phytotoxic agent propachlor (alpha-chloro-N-isopropyl-acetanilide), on L1210 cell proliferation.

We recently reported that a variety of phytotoxic compounds are capable of inhibiting the proliferation of mammalian tumor cells. We now report that an additional herbicide, propachlor (alpha-chloro-N-isopropyl-acetanilide), has a strong inhibitory effect on the proliferation of L1210 mouse leukemia cells. When tested in vitro against L1210 cells, propachlor displayed an ID50 on cell proliferation of less than 3 x 10(-7) M. Propachlor also inhibited significantly the uptake of leucine, thymidine and uridine. Kinetic experiments indicate that the inhibitory effects on cell proliferation and precursor uptake are present after the first day of culture. Furthermore, the inhibitory effect of propachlor is largely reversible in that cells grown in propachlor and then washed free of the compound return to a nearly normal rate of proliferation. Finally, these effects of propachlor were dependent on cell density, with greater activity occurring at higher propachlor to cell ratios.

Biochemical analysis of specific histamine HI and H2 receptors on lymphocytes.

It is increasingly clear that histamine mediates a variety of lymphocyte functions. Further understanding of these mechanisms requires a method for the analysis of histamine membrane receptors on the lymphocyte surface. We report now a biochemical technique for the identification and quantitation of specific histamine H1 and H2 receptors of lymphocytes. The method can be performed on small numbers of formaldehyde-fixed cells. The data this assay yields, together with that resulting from the flow cytometric analysis of histamine receptor distribution (a technique we have previously described), will be a powerful tool in the study of histamine mediation of lymphocyte function.

Histiocytosis-X.

Twelve of 17 patients with histiocytosis-X were immunologically abnormal, as shown by the presence of circulating lymphocytes spontaneously cytotoxic to cultured human fibroblasts or of antibody to autologous erythrocytes. The patients also had a notable lack of histamine H2 surface receptors on their T lymphocytes, suggesting a suppressor-cell deficiency. The lymphocyte abnormalities were reversed in vitro after incubation in a crude extract of calf thymus gland, and therefore all 17 patients were treated with daily intramuscular injections of this extract. With this therapy, 10 patients entered complete remission -- a response at least as good as that observed in historical controls treated with chemotherapy. A positive clinical response was associated with an increase in the number of T-cell histamine H2 receptors to normal levels and with correction of the other immunologic abnormalities. The results of this preliminary study justify a larger prospective clinical trial of thymic extract and further investigation of the immunoregulatory mechanisms in histiocytosis-X.

A technique for the flow cytometric analysis of lymphocytes bearing histamine receptors.

Histamine receptors have been demonstrated on lymphocyte membranes by a variety of techniques. We now report a method that allows for the flow cytometric analysis of histamine receptors on human peripheral T cells. Histamine is conjugated to fluoresceinated human albumin by the coupling agent ECDI. This conjugated histamine compound (FHA-his) binds to approximately 45% of T cells. Fluoresceinated human albumin alone (FHA), not conjugated to histamine, does not bind to T cells. In addition, unconjugated histamine can inhibit completely the binding seen with FHA-his. We conclude that this technique demonstrates specific FHA-his binding to histamine receptors on T cells and can be used to determine the number of cells bearing such receptors. In addition, the reagent could be used with a cell sorter to isolate distinct histamine-receptor-bearing (HR+) cells for further immunologic study.

Terminal deoxynucleotidyl transferase positive lymphoblastic lymphoma: a study of 15 cases.

The investigation was undertaken to define the features of lymphoblastic lymphoma. Fifteen lymph node biopsies from a group of 82 specimens studied for the enzyme terminal deoxynucleotidyl transferase (TdT) fulfilled morphological criteria for this diagnosis. These criteria required a diffuse infiltrate of relatively uniform, immature lymphoid cells with basophilic cytoplasm; round, oval or lobulated nuclei with evenly dispersed chromatin; rare or inconspicuous nucleoli; and numerous mitotic figures. Examination of 1-micron thick, plastic-embedded, Giemsa-stained tissue sections revealed convoluted nuclei in more than 50% of neoplastic cells in four cases: in six specimens there was an admixture of cells with grooved, hyperlobulated, and round nuclei, and in five the round or oval nuclei were non-convoluted. Specimens from all 15 patients were positive for TdT by fluorescent antibody and biochemical assays. The percentage of cells from involved nodes reacting by indirect immunofluorescence with an antiserum against bovine TdT ranged from 4 to 90% (mean of 52%), and the mean level of biochemically measured enzyme activity was 8.7 units/g of tissue (range of 1.9 to 27.5). Cytochemical stains for acid phosphatase were positive in 13 of the 15 cases. In eight samples more than 50% of cells formed rosettes with sheep erythrocytes, while the E rosettes varied from 14 to 38% in the other seven. The percentage of cells with complement receptors varied widely (range of 6 to 80), but cells bearing surface immunoglobulin or IgGfc receptors were not increased. All patients presented with supradiaphragmatic lymphaedenopathy, eight with an anterior mediastinal mass. Two-thirds of the patients were male, and the mean age was 20 years (range 4 to 46 years). None were leukemic at the time of diagnosis, but eight patients subsequently developed acute lymphoblastic leukemia. Involvement of the central nervous system was observed in four of the 15, and of the testes in two. Ten patients have died of their disease with a median survival of 8 months (range 4 to 20), and five are alive 3--8 months after diagnosis. We observed no differences in clinical findings at presentation, incidence of mediastinal involvement or leukemic dissemination, content of TdT, acid phosphatase staining, or immunologic cell surface characteristics between the convoluted and non-convoluted types of lymphoblastic lymphoma. Distinctive morphologic, cell surface, biochemical, and clinical features of lymphoblastic lymphoma can be identified irrespective of the presence or absence of convoluted nuclei.