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N E Davidson

Publications and source records attributed to N E Davidson.

At least 73 records · Page 4Linked to original sources
PubMed1996

Polyamine analogue induction of programmed cell death in human lung tumor cells.

The naturally occurring polyamines putrescine, spermidine, and spermine are required for cell growth. Based on this requirement, several polyamine analogues that interfere with polyamine function and metabolism have been synthesized as antineoplastic agents. The symmetrically substituted N1,N12-bis(ethyl)spermine (BESpm), and unsymmetrically substituted N1-ethyl-N11-[(cyclopropyl)methyl]-4, 8-diazaundecane (CPENSpm) have previously been shown to cause rapid cytotoxicity of NCI H157 cells, with concurrent high induction of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase. However, the precise mechanism(s) of the cytotoxic action of the compounds is not known. We now demonstrate that treatment with either BESpm or CPENSpm results in morphological and biochemical changes consistent with the activation of programmed cell death pathways, and that the unsymmetrically substituted CPENSpm more rapidly activates the death program. These studies suggest that the cell type-specific cytotoxicity of these polyamine analogues may be a result of their ability to selectively activate the cell death pathway in sensitive phenotypes and indicate that the relationship between the structure of the polyamine analogues and the ability to induce programmed cell death should be investigated.

Antineoplastic Agents↗
PubMed1996

Methylation of estrogen and progesterone receptor gene 5' CpG islands correlates with lack of estrogen and progesterone receptor gene expression in breast tumors.

Hormonal factors have a profound influence on the development, treatment, and outcome of breast cancer. The absence of steroid hormone receptors is highly correlated with resistance to antihormonal treatments. Work in cultured human breast cancer cell lines has shown that the absence of estrogen receptor (ER) gene expression in ER- cells is associated with extensive methylation of the ER gene 5' CpG island, and treatment with agents that demethylate the ER gene CpG island results in the production of functional ER protein. The current study shows that CpG islands in the 5' region of the ER and progesterone receptor (PR) genes are methylated in a significant fraction of primary human breast cancer tissues. The ER CpG island is methylated at the methylation-sensitive NotI restriction site in 9 of 39 (25%) of primary ER- breast cancers but remains unmethylated in 53 ER+ breast cancers and 9 normal breast specimens. Three methylation-sensitive restriction sites in the PR gene CpG island are not methylated in normal breast specimens and PR+ human breast cancers but are hypermethylated in 40% of PR- human breast tumors. These data demonstrate that methylation of the ER and PR gene CpG islands is associated with the lack of ER and PR gene expression in a significant fraction of human breast cancers.

Breast Neoplasms↗
PubMed1996

Paclitaxel induces programmed cell death in MDA-MB-468 human breast cancer cells.

The ability of paclitaxel, one of the most active chemotherapeutic agents against breast cancer, to induce programmed cell death in hormone-independent MDA-MB-468 human breast cancer cells was assessed. Treatment of MDA-MB-468 cells led to growth inhibition, high-molecular-weight and oligonucleosomal DNA fragmentation, and apoptosis-associated morphological changes after either 3- or 24-h exposure to paclitaxel concentrations >/=10 nM. Additionally, cleavage products of poly(ADP-ribose) polymerase and lamin B1, two proteins that are cleaved early in the execution phase of programmed cell death, were detected. Quantitative studies indicated that exposure to paclitaxel for 24 h resulted in more DNA fragmentation than did 3-h exposure. Rapid induction of the early-response gene c-jun but not c-myc was associated with paclitaxel treatment. The ability of paclitaxel to induce high-molecular-weight DNA fragmentation and apoptosis-associated morphological changes in three other breast cancer cell lines was also established. These data suggest that paclitaxel, an agent known to stabilize microtubules and prevent cell division but not to act directly on DNA, induces programmed cell death in breast cancer cells.

Antineoplastic Agents, Phytogenic↗
PubMed1995

E-cadherin expression is silenced by DNA hypermethylation in human breast and prostate carcinomas.

Expression of the Ca(2+)-dependent, homotypic cell:cell adhesion molecule, E-cadherin (E-cad), suppresses tumor cell invasion and metastasis in experimental tumor models. Decreased E-cad expression is common in poorly differentiated, advanced-stage carcinomas. These data implicate E-cad as an "invasion suppressor" gene. The mechanism by which E-cad is silenced in advanced stage carcinomas is unclear. In this report, we show that: (a) the 5' CpG island of E-cad is densely methylated in E-cad-negative breast and prostate carcinoma cell lines and primary breast carcinoma tissue but is unmethylated in normal breast tissue; (b) treatment with the demethylating agent, 5-aza-2'-deoxycytidine, partially restores E-cad RNA and protein levels in E-cad-negative breast and prostate carcinoma cell lines; and (c) and E-cad promoter/CAT construct is expressed in both E-cad-positive and -negative breast and prostate carcinoma cell lines, indicating that these cells have the active transcriptional machinery necessary for E-cad expression. Our data demonstrate that frequent loss of E-cad expression in human breast and prostate carcinomas results from hypermethylation of the E-cad promoter region.

Base Sequence↗
PubMed1995

Inactivation of the CDKN2/p16/MTS1 gene is frequently associated with aberrant DNA methylation in all common human cancers.

The tumor suppressor gene CDKN2/p16/MTS1, located on chromosome 9p21, is frequently inactivated in many human cancers through homozygous deletion. Recently, we have reported another pathway of inactivation that involves loss of transcription associated with de novo methylation of a 5' CpG island of CDKN2/p16 in lung cancers, gliomas, and head and neck squamous cell carcinomas. We now show that this aberrant CpG island methylation also occurs frequently in cell lines of breast cancer (33%), prostate cancer (60%), renal cancer (23%), and colon cancer (92%) and is associated with loss of transcription. Primary tumors of the breast (31%) and colon (40%) also displayed de novo methylation of this CpG island. This alteration of p16 in colon cancer was particularly striking, since inactivation does not occur through homozygous deletion in this tumor type. Our data show that in tumors, de novo methylation of the 5' CpG island is a frequent mode of inactivation of CDKN2/p16 and also firmly demonstrate that CDKN2/p16 is one of the most frequently altered genes in human neoplasia.

Carrier Proteins↗
PubMed1995

Induction of programmed cell death in human breast cancer cells by an unsymmetrically alkylated polyamine analogue.

The need for antineoplastic compounds with novel mechanisms of action is great. One such agent is the recently synthesized polyamine analogue N1-ethyl-N11-((cyclopropyl)methyl)-4,8-diazaundecane (CPENSpm). Exposure of hormone-dependent and -independent human breast cancer cells to 0.1-10 microM CPENSpm led to both growth inhibition and induction of programmed cell death. Fragmentation of DNA to high molecular weight fragments and oligonucleosomal-sized fragments, both characteristic of programmed cell death, was determined to be time and concentration dependent. Depletion of natural polyamine pools and accumulation of the analogue was also demonstrated. These data provide the first evidence that a polyamine analogue induces programmed cell death.

Acetyltransferases↗
PubMed1995

Demethylation of the estrogen receptor gene in estrogen receptor-negative breast cancer cells can reactivate estrogen receptor gene expression.

Approximately one third of breast cancers grow independently of estrogen, lack detectable estrogen receptor (ER) protein, and rarely respond to hormonal treatment. Previous studies correlated the lack of ER gene expression in ER-negative breast tumor cells with hypermethylation of a CpG island in the 5' region of the ER gene. In order to determine whether demethylation of the ER gene in the ER-negative human breast cancer cell line MDA-MB-231 could affect ER transcription, cells were treated with two inhibitors of DNA methylation, 5-azacytidine or 5-aza-2'-deoxycytidine. DNA from cells treated with either drug became partially demethylated at several methylation-sensitive restriction enzyme sites, including HhaI, NotI, and SacII, within the ER CpG island. This demethylation correlated with reexpression of the ER gene as detected by reverse transcriptase-PCR and production of ER protein as detected by Western blot analysis. ER produced in drug-treated cells was functionally active as demonstrated by its ability to activate transcription of estrogen-responsive genes. These results suggest that DNA methylation of the ER CpG island may play a role in suppression of ER gene expression in ER-negative breast cancer cells.

Antineoplastic Agents↗
PubMed1995

Absence of breast cancer cells in a single-day peripheral blood progenitor cell collection after priming with cyclophosphamide and granulocyte-macrophage colony-stimulating factor.

The effect of priming on occult tumor cell involvement of peripheral blood (PB) and PB progenitor cell (PBPC) collections is poorly characterized. Using sensitive immunocytochemistry (ICC) and tumor clonogenic assays (TCA) specific for epithelial-derived tumor cells, hematopoietic specimens were analyzed for PBPC and occult tumor cell involvement in 28 patients with chemotherapy-sensitive stage IIIB or IV breast cancer. Before PBPC priming, tumor was detected by ICC in PB of 1 of 23 (4%) patients and in bone marrow (BM) harvests of 4 of 27 (15%) patients. Fifteen days after cyclophosphamide and granulocyte-macrophage colony-stimulating factor (GM-CSF) priming, 2 of 28 (7%) patients had ICC-positive PBPC collections. The median amplification of CD34+ PBPC during this time was over 19-fold (range, < 1 to 199). One patient had pretreatment tumor involvement of both PB and BM. One patient grew tumor colonies in TCA; the PB and BM were ICC- and TCA-positive, but the PBPC collection was ICC-positive and TCA-negative. After cytoreduction with conventional-dose chemotherapy, patients with advanced breast cancer and histologically negative BM biopsy specimens have rare tumor cell involvement of PB and BM. Despite effective PBPC priming with cyclophosphamide and GM-CSF, clonogenic breast cancer cells were not found in the PBPC collection performed on day 15.

Adult↗
PubMed1995

Predictive factors for peripheral-blood progenitor-cell collections using a single large-volume leukapheresis after cyclophosphamide and granulocyte-macrophage colony-stimulating factor mobilization.

PURPOSE: (1) To study the ability of mobilized peripheral-blood progenitor cells (PBPC) collected in a single large-volume leukapheresis performed on a predetermined date to accelerate engraftment after high-dose cyclophosphamide and thiotepa; (2) to establish the minimum dose of PBPC associated with early engraftment; and (3) to identify parameters predictive of collection of large numbers of PBPC. PATIENTS AND METHODS: Twenty-three patients with breast cancer received cyclophosphamide (4 g/m2) and granulocyte-macrophage colony-stimulating factor ([GM-CSF] 5 micrograms/kg/d x 15 days) for PBPC mobilization. A single leukapheresis was performed 15 days after cyclophosphamide administration. Then, patients received high-dose cyclophosphamide and thiotepa followed by reinfusion of PBPC and 4-hydroperoxycyclophosphamide (4HC)-purged bone marrow. PBPC concentration was measured in serial peripheral-blood samples and in the leukapheresis product. Correlation analysis between PBPC dose and engraftment and between leukapheresis yield and patient characteristics was attempted. RESULTS: A single leukapheresis processed a median 36 L (range, 24 to 46) blood and collected 5 x 10(6) CD34+ cells/kg (< 0.3 to 24) and 6.2 x 10(5) colony-forming units granulocyte-macrophage (CFU-GM)/kg (< 0.001 to 29). All sixteen patients (70%) reinfused with > or = 2.9 x 10(6) CD34+ cells/kg reached a level of greater than 1,000 leukocytes/microL by day 13 and greater than 50,000 platelets/microL by day 15. All of these patients had a percentage of peripheral-blood CD34+ cells > or = 0.5%, and all but one, a level of greater than 100,000 platelets/microL, on the day of leukapheresis. The bone marrow CD34+ cell percentage at study entry predicted the number of CD34+ cells collected after PBPC mobilization (R2 = .42, P = .002). All patients with > or = 2.5% bone marrow CD34+ cells experienced early engraftment. CONCLUSION: Reinfusion of PBPC collected in a single leukapheresis accelerates engraftment in the majority of patients. Pretreatment bone marrow CD34+ cell content determines PBPC mobilization capacity and may help select hematopoietic rescue strategies.

Adult↗
PubMed1995

Phase I and pharmacologic study of the alkylating agent modulator novobiocin in combination with high-dose chemotherapy for the treatment of metastatic breast cancer.

PURPOSE: Resistance to alkylators may potentially be overcome by drugs that inhibits DNA repair, thus improving the efficacy of high-dose chemotherapy. This trial was performed to determine if novobiocin, an agent that inhibits DNA repair, could be given with high-dose alkylators. Study aims were to define the toxicities and maximal-tolerated dose (MTD) of novobiocin and the pharmacokinetics of novobiocin and high-dose cyclophosphamide and thiotepa. PATIENTS AND METHODS: Thirty-eight women with responsive metastatic breast cancer received high-dose cyclophosphamide (3 to 6 g/m2 over 4 days), thiotepa (400 to 800 mg/m2), and novobiocin (0.5 to 5.0 g/d x 7, orally) with autologous marrow support. Toxicity was monitored. The pharmacology of novobiocin, cyclophosphamide, and thiotepa was evaluated. RESULTS: There were no toxic deaths. The MTD of novobiocin was 4 g/d. All seven patients treated at 5 g/d developed grade III/IV mucositis and vomiting. The severity of mucositis correlated with the plasma levels of novobiocin. Other severe toxicities were not observed. Plasma novobiocin levels > or = 100 micrograms/mL, which are associated with reversal of drug resistance in animal models, were consistently seen at dose levels greater than 2 g. The dispositions of cyclophosphamide and thiotepa were not altered by novobiocin. CONCLUSION: Novobiocin may be given with high-dose alkylators in doses that produce plasma levels that augment the activity of these cytotoxics in experimental models. The pharmacology of high-dose cyclophosphamide and thiotepa is unaffected. Novobiocin 4 g/d orally for 7 days is recommended for future study.

Adult↗
PubMed1994

Interleukin-3 and bryostatin-1 mediate hyperphosphorylation of BCL2 alpha in association with suppression of apoptosis.

Using murine myeloid factor-dependent FDC-P1/ER cells, we demonstrate that the hematopoietic growth factors interleukin-3 and erythropoietin and bryostatin-1, a macrocyclic lactone natural product and potent activator of protein kinase C (PKC), suppress apoptosis and induce the rapid serine phosphorylation of Bc12 alpha. Expression of recombinant wild type Bc12 alpha in NFS/N1.H-7 cells confirms that murine Bc12 alpha is phosphorylated following PKC activation. The PKC inhibitors H-7 and staurosporine, but not the protein kinase A inhibitor HA1004, block not only interleukin-3- and bryostatin-1-induced hyperphosphorylation of Bc12 alpha but also their anti-apoptotic effect on growth factor-dependent cells, suggesting a role for activated PKC in both processes. A potential direct role for a classic isoform of PKC is indicated by the Ca(2+)-dependent nature of phosphorylation of Bc12 alpha mediated by purified PKC in vitro. Comparative phosphopeptide maps confirm that Bc12 alpha phosphorylation occurs on identical serine site(s) whether phosphorylation occurs in cells following agonist treatment or directly by PKC in vitro. These findings strongly support a role for activated PKC in growth factor-induced Bc12 alpha phosphorylation as well as suppression of apoptosis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Epidermal growth factor-mediated apoptosis of MDA-MB-468 human breast cancer cells.

MDA-MB-468 human breast cancer cells lack estrogen receptors, overexpress epidermal growth factor (EGF) receptors, and are growth inhibited by EGF. We show that treatment of MDA-MB-468 cells with EGF leads to inhibition of cell proliferation, fragmentation of DNA into nucleosomal oligomers, and the development of apoptotic morphology. This treatment is associated with increased expression of c-myc, c-fos, jun family members, and transforming growth factor beta 1 mRNA and with partial proteolytic cleavage of poly(ADP-ribose) polymerase and lamin B. The observation that EGF can mediate apoptosis in EGF receptor-overexpressing cells has important implications for clinical efforts directed at the EGF receptor.

Apoptosis↗
PubMed1994

Methylation of the estrogen receptor gene CpG island marks loss of estrogen receptor expression in human breast cancer cells.

Breast cancer is the most common malignancy in women and hormone resistance is a challenging problem in its treatment. Loss of estrogen receptor expression is an important means of hormone resistance, but the mechanisms involved are poorly understood. We now demonstrate a potential role for abnormal DNA methylation in transcriptional inactivation of the estrogen receptor gene. Estrogen receptor-negative human breast cancer cells growing in culture lack estrogen receptor mRNA, have a higher capacity to methylate DNA, and display extensive methylation of the CpG island in the 5' promoter region of the estrogen receptor gene, which would correlate with silencing of expression. These results suggest that abnormal methylation could account for transcriptional inactivation of the estrogen receptor gene and subsequent hormone resistance in some human breast cancers.

Breast Neoplasms↗
PubMed1994

Bone marrow micrometastases in chemotherapy-responsive advanced breast cancer: effect of ex vivo purging with 4-hydroperoxycyclophosphamide.

Tumor contamination of hematopoietic stem cell grafts may influence the outcome of breast cancer patients treated with high-dose chemotherapy. The goals of this study were: (a) to evaluate the prevalence of tumor contamination of bone marrow (BM) harvests in patients responding to systemic chemotherapy; (b) to evaluate reduction of BM tumor contamination by ex vivo purging with 4-hydroperoxycyclophosphamide (4HC); and (c) to compare the tumor contamination of peripheral blood progenitor cell collections and BM in advanced-stage breast cancer patients designated for peripheral blood progenitor cell infusion. We evaluated pre- and post-4HC purge BM specimens from 20 patients for tumor contamination using immunocytochemistry and for in vitro growth potential of tumor cells using a tumor cell clonogenic assay. Pre-4HC purge BM specimens from 15 of 20 (75%) patients were immunocytochemistry and tumor cell clonogenic assay negative. The remaining 5 BM specimens were immunocytochemistry positive, but only 3 of 5 specimens were tumor cell clonogenic assay positive. In vitro tumor colony growth was not observed in any post-4HC purge BM specimens. We also evaluated nine patients with bone or BM metastases from the start of induction chemotherapy. We found less tumor involvement of peripheral blood progenitor cell collections than of simultaneously obtained bone marrow aspirates. We conclude that bone marrow micrometastases occur with low frequency in women with chemotherapy-sensitive breast cancer and that ex vivo purging with 4HC may render tumor cells nonviable.

Adult↗
PubMed1994

Methylation of the oestrogen receptor CpG island links ageing and neoplasia in human colon.

We report that CpG island methylation, an epigenetic modification of DNA known to correlate closely with silencing of gene transcription, appears in the oestrogen receptor (ER) gene in a subpopulation of cells which increases as a direct function of age in human colonic mucosa. This same methylation change characterizes virtually all cells in all 45 colorectal tumours examined, including the earliest stages of tumour formation. ER gene expression is diminished or absent in colorectal tumours, and introduction of an exogenous ER gene in cultured colon carcinoma cells resulted in marked growth suppression. Our data suggest that methylation associated inactivation of the ER gene in ageing colorectal mucosa could be one of the earliest events that predispose to sporadic colorectal tumorigenesis.

Aging↗