Modulation by bryostatin 1 of the in vitro radioprotective effects of the GM-CSF/IL-3 fusion protein, PIXY 321, on normal human myeloid progenitors

Pharmacology and clinical experience with bryostatin 1: a novel anticancer drug

Bryostatin 1 (bryo 1) is an example of a novel class of anticancer drug which modulates protein kinase C (PKC) activity. It has varied biological effects mediated largely by the initial activation of PKC, followed by its rapid downregulation. Bryo 1 stimulates in vitro and in vivo haematopoietic progenitor cell growth in a concentration-dependent and lineage-specific fashion. Granulocytes, lymphocytes, monocytes and platelets are all functionally stimulated by bryo 1. Stimulation of cytotoxic T-cell activity by bryo 1 has led to research utilising bryo 1 as an immunotherapeutic agent in mouse tumour xenograft models. The clinical development of bryo 1 followed the demonstration of direct in vitro activity against various tumour cell lines. Multiple Phase I trials have shown muscle pain and flu-like symptoms are the most common toxicities associated with administration of bryo 1. There is particular interest in the role of bryo 1 in haematologic malignancies because of its capacity to induce leukaemic cell differentiation. There is ample in vitro data demonstrating that bryo 1 can sensitise tumour cells to cytotoxic agents. Recent clinical work has focused on combining bryo 1 with traditional chemotherapeutic agents for both haematologic and non-haematologic cancers.

Sensitivity to cis-diamminedichloroplatinum in human cancer cells is related to expression of cyclin D1 but not c-raf-1 protein

Although several oncogenes, including c-myc, ras and c-raf-1, have been implicated in cellular resistance to ionising radiation, there is less information relating oncogene expression to cis-diamminedichloroplatinum (CDDP) resistance. However, transfection of c-myc or v-H-ras and activation of protein kinase C (PKC), which contributes to the RAF-1, MAP kinase signal transduction pathway, can influence therapeutic response to CDDP. Activation of PKC increases CDDP sensitivity, whilst transfected c-myc or v-H-ras induce CDDP resistance. We have previously reported that human in vitro cell lines show different patterns of sensitivity to CDDP and 4 MeV X-irradiation. In these cells radiation sensitivity is related to high levels of expression of the C-raf-1 proto-oncogene. We thus predicted that cells sensitive to CDDP might show a different relationship to c-raf-1 expression. In addition, because cyclin D1 expression can be upregulated by the myc or ras oncogenes, we also chose to study putative relationships between cyclin D1 protein levels and intrinsic cellular sensitivity to CDDP and gamma-irradiation. We report that in the 16 human cell lines which we have studied, high cyclin D1 expression is related to CDDP resistance but has no relationship with radiation responsiveness, whereas high c-raf-1 expression, although related to radiosensitivity has no relationship with CDDP responsiveness.

Antineoplastic agents. 340. Isolation and structural elucidation of bryostatins 16-18

Separation of two trace cancer cell growth inhibitory (P388 leukemia) fractions from about 1000 kg of wet Gulf of Mexico Bugula neritina (Bryozoa) has led to the isolation of bryostatins 16-18 (2-4). A combination of HRFABMS and high-field (400 MHz) 1H- and 13C-NMR spectral analyses were employed to assign the structures. The three new 20-desoxybryostatins 16 (2), 17 (3), and 18 (4) showed significant growth inhibitory activity (P388 ED50, 2, 9.3 x 10(-3) micrograms/mL, 3, 1.9 x 10(-2) micrograms/mL, and 4, 3.3 x 10(-3) micrograms/mL) against murine P388 lymphocytic leukemia.