bryostatin-1 and Lymphoma

A Phase Ib trial of bryostatin 1, a macrocyclic lactone and protein kinase C (PKC) activator, was conducted in patients with refractory nonhematological malignancies with the primary goal of determining whether down-regulation of peripheral blood mononuclear cell (PBMNC) PKC activity could be achieved in vivo in humans. Patients (four patients/cohort) received bryostatin 1 (25 microg/m2) as a 1-h infusion weekly three times every 4 weeks, but to study the schedule dependence of pharmacokinetics and pharmacodynamics, the first dose was administered according to one of three schedules: (a) a 1-h infusion; (b) a 24-h infusion; or (c) a split course (12.5 microg/m2 as a 30-min infusion) on days 1 and 4. Conventional toxicities (grades I-III) included myalgias, fever, anemia, fatigue, phlebitis, and headache; in addition, two patients in cohort 3 experienced transient elevations in liver function tests, although these patients had preexisting liver metastases. No objective clinical responses were encountered. Effects on PBMNC PKC activity were heterogeneous. Several patients in cohorts 1 and 2 experienced significant declines in activity (approximately 50%) that were sustained in some cases for periods of > or = 72 h. Comparison of 72-h with baseline values for all three patient cohorts combined revealed a trend toward PKC down-regulation (P = 0.06; signed rank test). For each schedule, plasma bryostatin 1 levels were below the level of detection of a platelet aggregation-based bioassay (3-4 nm). Bryostatin 1 administration failed to produce consistent alterations in lymphocyte immunophenotypic profiles, interleukin 2-induced proliferation, or cytotoxicity, although two of three samples from patients in cohort 3 did show significant posttreatment increases in proliferation. Moreover, in some patients, bryostatin 1 treatment increased lymphokine-activated killer cell activity. These findings indicate that bryostatin 1 doses of 25 microg/m2 can induce in vivo PBMNC PKC down-regulation in at least a subset of patients and raise the possibility that higher bryostatin 1 doses may be more effective in achieving this effect.

Topics: Adult; Aged; Antineoplastic Agents; Bryostatins; Cohort Studies; Cytotoxicity, Immunologic; Drug Administration Schedule; Female; Humans; Immunophenotyping; Infusions, Intravenous; Interleukin-2; Lactones; Lymphocyte Activation; Lymphocytes; Lymphoma; Macrolides; Male; Metabolic Clearance Rate; Middle Aged; Neoplasms; Patient Selection; Platelet Aggregation; Protein Kinase C

Topics: Antineoplastic Agents; Bryostatins; Clinical Protocols; Clinical Trials as Topic; Humans; Lactones; Leukemia; Lymphoma; Macrolides; Melanoma; Neoplasms; United States

Annexin VIII is a calcium- and phospholipid-binding protein with anticoagulant activity. Annexin VIII mRNA was found to be specifically expressed in acute promyelocytic leukemia (APL) cells; it was not found in other types of acute myeloid leukemia (AML) nor in lymphoid malignancies. Using Northern blot analysis we investigated annexin VIII expression in 142 continuous human leukemia and lymphoma cell lines at the mRNA level. While the only APL cell line, NB-4, was indeed positive, other cell lines also displayed annexin VIII mRNA: 4/22 myeloid cell lines, 8/23 monocytic cell lines, 2/8 megakaryoblastic cell lines, 5/26 lymphoma-derived cell lines, 2/10 myeloma cell lines and 1/44 lymphoid leukemia cell lines. The strongest expression was seen in NB-4 and in the Hodgkin's disease derived cell line HDLM-2. Treatment of NB-4 cells with all-trans retinoic acid (ATRA) or the phorbol ester TPA induced terminal differentiation and down-regulated annexin VIII mRNA expression rapidly within a few hours; vitamin D3 was ineffective in this regard; the protein kinase C activator Bryostatin 1 up-regulated the expression. A panel of initially negative cell lines could not be induced by any of these biomodulators to transcribe annexin VIII. The half-life (T1/2) of annexin VIII mRNA was about 3-4 h using actinomycin D as transcription inhibitor. Treatment with ATRA or TPA prior to exposure to actinomycin shortened the T1/2 to 2 h while Bryostatin 1 extended it to 6h. As 21/141 non-APL cell lines were positive, annexin VIII cannot be used as a marker gene for APL cells; however, it might be associated with myelomonocytic or erythro-megakaryoblastic precursor cells. Annexin VIII gene expression might play a unique role in the proliferation and/or differentiation of leukemic cells and could be associated with the particular abnormal hemostasis of some leukemias.

Topics: Annexins; Blotting, Northern; Bryostatins; Cell Differentiation; Cholecalciferol; Dactinomycin; Gene Expression Regulation, Neoplastic; Half-Life; Humans; Lactones; Leukemia; Leukemia, Myeloid; Leukemia, Promyelocytic, Acute; Lymphoma; Macrolides; RNA, Messenger; Tetradecanoylphorbol Acetate; Tretinoin; Tumor Cells, Cultured

The macrocyclic lactone bryostatin-1 was found to exert in vitro antineoplastic activity against several leukemic cell lines, including human K562 erythroleukemia, HL60 promyelocytic leukemia, REH and MOLT-4 lymphoblastic leukemias, CCRF-CEM lymphoma, KG-1 myeloid leukemia, and murine P388 lymphocytic leukemia. No statistically significant difference in sensitivity to bryostatin-1 was found between adriamycin-resistant P388 and K526 subclones and their sensitive counterparts. Freshly explanted clonogenic leukemic cells showed a variable sensitivity to bryostatin-1 in 10/12 tested samples. The IC50 of clonogenic leukemic cells was 4 x 10(-3) M bryostatin-1, and that of normal marrow CFU-GM was 10(-5) M. Leukemic cells exposed to bryostatin-1 showed a variable degree of monocytic differentiation as evaluated by ANAE staining and morphology. Bryostatin-1 is also able to inhibit the growth of CFU-GM from myelodysplastic marrow and to shorten the duration of dysplastic hematopoiesis in liquid culture. In conclusion, these data suggest that bryostatin-1 is a potent antileukemic agent in vitro that may be potentially useful for clinical studies.

Topics: Antineoplastic Agents; Bryostatins; Drug Screening Assays, Antitumor; Humans; Lactones; Leukemia; Lymphoma; Macrolides; Tumor Cells, Cultured; Tumor Stem Cell Assay