bryostatin-1 and Colonic-Neoplasms

Bryostatin 1 is a novel antitumour agent derived from Bugula neritina of the marine phylum Ectoprocta. Nineteen patients with advanced solid tumours were entered into a phase I study to evaluate the toxicity and biological effects of bryostatin 1. Bryostatin 1 was given as a one hour intravenous infusion at the beginning of each 2 week treatment cycle. A maximum of three treatment cycles were given. Doses were escalated in steps from 5 to 65 micrograms m-2 in successive patient groups. The maximum tolerated dose was 50 micrograms m-2. Myalgia was the dose limiting toxicity and was of WHO grade 3 in all three patients treated at 65 micrograms m-2. Flu-like symptoms were common but were of maximum WHO grade 2. Hypotension, of maximum WHO grade 1, occurred in six patients treated at doses up to and including 20 micrograms m-2 and may not have been attributable to treatment with bryostatin 1. Cellulitis and thrombophlebitis occurred at the bryostatin 1 infusion site of patients treated at all dose levels up to 50 micrograms m-2, attributable to the 60% ethanol diluent in the bryostatin 1 infusion. Subsequent patients treated at 50 and 65 micrograms m-2 received treatment with an intravenous normal saline flush and they did not develop these complications. Significant decreases of the platelet count and total leucocyte, neutrophil and lymphocyte counts were seen in the first 24 h after treatment at the dose of 65 micrograms m-2. Immediate decreases in haemoglobin of up to 1.9g dl-1 were also noted in patients treated with 65 micrograms m-2, in the absence of clinical evidence of bleeding or haemodynamic compromise. No effect was observed on the incidence of haemopoietic progenitor cells in the marrow. Some patients' neutrophils demonstrated enhanced superoxide radical formation in response to in vitro stimulation with opsonised zymosan (a bacterial polysaccharide) but in the absence of this additional stimulus, no bryostatin 1 effect was observed. Lymphocyte natural killing activity was decreased 2 h after treatment with bryostatin 1, but the effect was not consistently seen 24 h or 7 days later. With the dose schedule examined no antitumour effects were observed. We recommend that bryostatin 1 is used at a dose of 35 to 50 micrograms m-2 two weekly in phase II studies in patients with malignancies including lymphoma, leukaemia, melanoma or hypernephroma, for which pre-clinical investigations suggest antitumour activity.

Topics: Adult; Aged; Antineoplastic Agents; Bone Marrow; Bryostatins; Colonic Neoplasms; Colony-Forming Units Assay; Drug Administration Schedule; Female; Humans; Infusions, Intravenous; Killer Cells, Natural; Lactones; Leukocytes; Macrolides; Mesothelioma; Middle Aged; Neoplasms; Neutrophils; Ovarian Neoplasms; Phagocytosis; Sarcoma

Butyrate is a potentially selective therapeutic agent for many adenocarcinomas. Butyrate causes reversible growth arrest as well as some death of VACO 5 colon cancer cells. Combined treatment with butyrate and the phorbol ester TPA leads instead only to cell death, while TPA causes little death on its own. Cells dying during treatment with TPA and butyrate, as well as those dying in the presence of butyrate alone, exhibit features typical of apoptosis, including detachment, shrinkage and internucleosomal DNA cleavage. Pre-treating VACO 5 cell cultures with TPA for as little as 6 hr prior to butyrate addition led to a markedly diminished enhancement of butyrate-induced apoptosis. Treatment with a distinct PKC activator, bryostatin 1, was ineffective in enhancing butyrate-induced death and, furthermore, counteracted the death-enhancing actions of TPA. Such antagonism was apparent when bryostatin was added after 12 hr of TPA/butyrate treatment but was much less effective thereafter. The duration of TPA/butyrate treatment required for depressing cell survival by >95% was thereby estimated to be 24 hr. Other colon cancer cell lines were examined for the extent of cell death following treatment with TPA/butyrate. In each of these lines, butyrate inhibited cell replication in a reversible manner, similar to that seen in VACO 5. However, the combination of butyrate and TPA led to high levels of cell death in only a subset of these lines. TPA/butyrate-treated cultures of COLO 201 exhibited extensive apoptosis, similar in timing and magnitude to the response by VACO 5, whereas HCT 116 was reversibly growth-arrested. Our findings indicate that the PKC system plays a critical role in maintaining cell survival during butyrate-induced growth arrest.

Topics: Adenocarcinoma; Antineoplastic Agents; Apoptosis; Bryostatins; Butyrates; Butyric Acid; Cell Division; Colonic Neoplasms; Drug Interactions; Enzyme Activation; Humans; Kinetics; Lactones; Macrolides; Protein Kinase C; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

Tumor-producing phorbol esters [e.g., 12-O-tetradecanoylphorbol-13-acetate (TPA)] induce changes in a human colon cancer cell line, VACO 10MS, that mimic terminal differentiation: a rapid blockade of DNA replication and cell division, a marked increase in cell adhesion properties with striking changes in morphology, and the acquisition of ion-transporting activities. The present report shows that the triggering of this terminal differentiation sequence by TPA is associated with a rapid release of heparan sulfate proteoglycans from the cell surface that is soon followed by an acceleration of proteoglycan synthesis. The activation of the release mechanism is independent of ongoing protein synthesis, whereas the resynthesis of the proteoglycans requires the production of new proteins. A persistent high rate of proteoglycan synthesis and release appears correlated with the progression of the colon cell into the terminal differentiation state. Bryostatin 1, an agent which has been shown previously to block the TPA-induced terminal differentiation of this cell line, also largely prevents the TPA effects on proteoglycan metabolism. Since both TPA and bryostatin 1 produce their effects through the activation of members of the protein kinase C class of enzymes, it is proposed that the differentiation state of these colon cancer cells may be regulated by a differential activation of isozymes or a ligand-directed phosphorylation of proteins that are involved in proteoglycan metabolism.

Topics: Bryostatins; Cell Differentiation; Cell Division; Colonic Neoplasms; Cycloheximide; Diglycerides; DNA Replication; Enzyme Activation; Heparitin Sulfate; Humans; Isoenzymes; Lactones; Macrolides; Membrane Proteins; Neoplasm Proteins; Phosphorylation; Protein Kinase C; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

12-O-Tetradecanoylphorbol-13-acetate (TPA), a highly active representative of the tumor-promoting phorbol esters, induces a rapid terminal differentiation of a human colon cancer cell line. Bryostatin 1, a macrocyclic lactone, completely counteracts this effect of TPA and promotes continued replication. The observed responses provide a system for identifying cellular processes which are involved in the induced terminal differentiation of human colon cancer cells.

Topics: Bryostatins; Cell Differentiation; Cell Division; Cell Line; Colonic Neoplasms; DNA Replication; Humans; Lactones; Macrolides; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured