PubMed Health⌕ Search

Biomedical subjects

S Rockwell

Publications and source records attributed to S Rockwell.

At least 19 recordsLinked to original sources
PubMed1998

Scatter factor protects epithelial and carcinoma cells against apoptosis induced by DNA-damaging agents.

Scatter factor (SF) (hepatocyte growth factor) is a cytokine that may play a role in human breast cancer invasiveness and angiogenesis. We now report that SF can block the induction of apoptosis by various DNA damaging-agents, including cytotoxic agents used in breast cancer therapy. SF protected MDA-MB-453 human breast cancer cells, EMT6 mouse mammary tumor cells and MDCK renal epithelial cells against apoptosis induced by adriamycin (ADR), X-rays, ultraviolet radiation, and other agents. Protection was observed in assays of DNA fragmentation, cell viability (MTT), and clonogenic survival. Protection of MDA-MB-453 cells against ADR was dose- and time-dependent; maximal protection required pre-incubation with 75-100 ng/ml of SF for 48 h or more. Protection required functional SF receptor (c-Met), but was not dependent on p53. Western blotting analysis revealed that pre-treatment of MDA-MB-453 cells with SF inhibited the ADR-induced decreases in the levels of Bcl-XL, an anti-apoptotic protein related to Bcl-2; and the dose-response and time course characteristics for SF-mediated increases in the Bcl-XL protein levels of ADR-treated cells were consistent with the degrees of protection against apoptosis observed under the same conditions. Furthermore, Bcl-XL levels were not down-regulated by ADR in MDA-MB-231 breast cancer cells, consistent with the finding that SF failed to protect these cells against ADR, despite the fact that they contain functional c-Met receptor. In contrast to Bcl-XL, SF blocked ADR-induced increases in c-Myc and inhibited the expression of p21WAF1/CIP1 and of the BRCA1 protein in MDA-MB-453 cells. However, SF did not cause significant changes in the cell cycle distribution of ADR-treated cells. These findings suggest that SF-mediated protection of human breast cancer cells may involve inhibition of one or more pathways required for the activation of apoptosis and may particularly target the anti-apoptotic mitochondrial membrane pore-forming protein Bcl-XL as a component of the protective mechanism. By implication, the accumulation of SF within human breast cancers may contribute to the development of a radio- or chemoresistant phenotype.

Animals↗
PubMed1998

The intracellular location of NADH:cytochrome b5 reductase modulates the cytotoxicity of the mitomycins to Chinese hamster ovary cells.

NADH:cytochrome b5 reductase activates the mitomycins to alkylating intermediates in vitro. To investigate the intracellular role of this enzyme in mitomycin bioactivation, Chinese hamster ovary cell transfectants overexpressing rat NADH:cytochrome b5 reductase were generated. An NADH:cytochrome b5 reductase-transfected clone expressed 9-fold more enzyme than did parental cells; the levels of other mitomycin-activating oxidoreductases were unchanged. Although this enzyme activates the mitomycins in vitro, its overexpression in living cells caused decreases in sensitivity to mitomycin C in air and decreases in sensitivity to porfiromycin under both air and hypoxia. Mitomycin C cytotoxicity under hypoxia was similar to parental cells. Because NADH:cytochrome b5 reductase resides predominantly in the mitochondria of these cells, this enzyme may sequester these drugs in this compartment, thereby decreasing nuclear DNA alkylations and reducing cytotoxicity. A cytosolic form of NADH:cytochrome b5 reductase was generated. Transfectants expressing the cytosolic enzyme were restored to parental line sensitivity to both mitomycin C and porfiromycin in air with marked increases in drug sensitivity under hypoxia. The results implicate NADH:cytochrome b5 reductase in the differential bioactivation of the mitomycins and indicate that the subcellular site of drug activation can have complex effects on drug cytotoxicity.

Animals↗
PubMed1997

Bioreductive alkylating agent porfiromycin in combination with radiation therapy for the management of squamous cell carcinoma of the head and neck.

Porfiromycin (methyl mitomycin C) has been shown in laboratory studies to have increased preferential cytotoxicity to hypoxic cells and therefore may provide enhanced therapeutic efficacy over mitomycin C when used in combination with radiation therapy (RT). The purpose of the two clinical studies reported here is to evaluate the concomitant use of porfiromycin with RT in the management of squamous cell carcinoma of the head and neck. Between October 1989 and July 1992, 21 patients presenting with locally advanced stage III/IV squamous cell carcinoma of the head and neck were entered into a phase I toxicity trial evaluating porfiromycin as an adjunct to RT. Patients were eligible if they had biopsy documented squamous cell carcinoma of the head and neck with a low probability of cure by conventional means. Patients were treated with standard fractionated daily RT to a total median dose of 63 Gy, with porfiromycin administered on days 5 and 47 of the course of RT. Upon completion of this phase I trial, a phase III trial was initiated in November 1992 randomizing patients with squamous cell carcinoma of the head and neck to RT with mitomycin C vs. RT with porfiromycin. There is no radiation only arm in this current trial. To date, 75 patients have been entered on this trial and acute toxicity data are available on 67 patients (34 porfiromycin, 31 mitomycin C) who have completed their entire course of treatment. Median follow-up of the 21 patients enrolled in the phase I porfiromycin trial is 58.5 months. Of the 21 patients, 5 were treated at a dose of 50 mg/M2, 4 at 45 mg/M2, and the final 12 at 40 mg/M2, which appeared to result in acceptable acute hematological and nonhematological toxicities. As of December 1995, 14 of the 21 patients have died with disease and 7 remain alive and free of disease, resulting in a 5-year actuarial survival of 32%. Of the patients enrolled to date in the phase III randomized trial of mitomycin C vs. porfiromycin, there have been no statistically significant differences between the two arms with respect to white blood cell count (WBC), platelet, or hemoglobin nadirs. Acute nonhematological toxicities including mucositis, epidermitis, odynophagia, and nausea have also been comparable. Two patients in this current randomized trial died during treatment, apparently of nondrug-related causes. We conclude that the bioreductive alkylating agent porfiromycin has demonstrated an acceptable toxicity profile to date. Final analysis of the phase I trial, which revealed a 5-year no evidence of disease survival rate of 32% in patients with locally advanced disease and a low probability of cure, appears encouraging. We anticipate completion of the current ongoing trial comparing mitomycin C to porfiromycin in the next 2 years. Further investigations, including large-scale multiinstitutional trials employing bioreductive alkylating agents or other hypoxic cell cytotoxins as adjuncts to RT, are warranted.

Antibiotics, Antineoplastic↗
PubMed1997

Chemotherapy as an adjunct to radiation in the treatment of squamous cell carcinoma of the head and neck: results of the Yale Mitomycin Randomized Trials.

PURPOSE: Two consecutive randomized trials were run at our institution using the bioreductive alkylating agent mitomycin as an adjunct to radiation therapy in an effort to improve outcome in patients with squamous cell carcinoma of the head and neck. METHODS: Between 1980 and 1992, two consecutive randomized trials using mitomycin (trial 1) and mitomycin with dicumarol (trial 2) as an adjunct to radiation therapy in patients with squamous cell carcinoma of the head and neck were conducted at our institution. The patients were stratified by intent of therapy, extent of disease, and primary tumor site. Within each strata, patients were randomized to receive radiation therapy with or without mitomycin (trial 1) or mitomycin/dicumarol (trial 2). RESULTS: A total of 203 patients were enrolled onto both trials, 195 of whom were eligible for analysis. Patients were equally balanced with respect to sex, age, extent of disease, primary site, radiation dose, and total duration of radiation treatment. Hematologic toxicities were more frequently noted in the drug-treated arms, but were acceptable with no drug-related treatment deaths. Nonhematologic toxicities were acceptable and not significantly different between the two arms. As of September 1995, with a median follow-up of 138 months, a statistically significant benefit occurred in the mitomycin arms with respect to cause-specific survival (0.74 +/- 0.05 v 0.51 +/- 0.05; P = .005), local recurrence-free survival (0.85 +/- 0.04 v 0.66 +/- 0.05; P = .002), and local regional recurrence-free survival (0.76 +/- 0.05 v 0.54 +/- 0.05; P = .003). No statistically significant difference in overall survival was obtained (0.48 +/- 0.05 mitomycin arms v 0.42 +/- 0.05 radiation alone). CONCLUSION: The bioreductive alkylating agent mitomycin is a safe and effective adjunct to radiation therapy in the treatment of squamous cell carcinoma of the head and neck. The statistically and clinically significant improvement in local regional relapse and cause-specific survival obtained support the use of mitomycin as an adjunct to radiation therapy in the management of squamous cell carcinoma of the head and neck.

Adult↗
PubMed1997

Oxygen delivery: implications for the biology and therapy of solid tumors.

Solid malignancies develop areas of hypoxia during the earliest phase of their development, while they are still microscopic in size and before they have initiated angiogenesis. The physiologic effects of hypoxia and the associated microenvironmental inadequacies increase mutation rates, select for cells deficient in normal pathways of programmed cell death, and contribute to the development of an increasingly invasive, metastatic phenotype. Hypoxic tumor cells are also resistant to radiation and to many antineoplastic drugs, and can limit the curability of solid tumors by radiotherapy and chemotherapy. This article reviews several approaches to improving tumor oxygenation and discusses the results of laboratory and clinical studies examining their efficacy in improving the outcome of radiation therapy. Past clinical trials, using nonoptimal agents and regimens to circumvent the protective effects of hypoxia, improved local control rates by approximately 10%. Greater improvements should be possible when the new agents now undergoing laboratory testing are used in optimally designed clinical regimens.

Antineoplastic Agents↗
PubMed1996

Independent regulation of invasion and anchorage-independent growth by different autophosphorylation sites of the macrophage colony-stimulating factor 1 receptor.

Invasion of tissue by macrophages and implantation into the uterine wall by placental trophoblasts are known to be regulated by the macrophage colony-stimulating factor (CSF-1) and its receptor (CSF-1R, the product of the c-fms proto-oncogene). Recently, the clinical importance of CSF-1 and CSF-1R in invasive breast carcinoma has been recognized, but the significance of coexpression of CSF-1 and CSF-1R in mammary epithelial cell invasion has not been explored. In the present study, we investigated the invasive potential of a noninvasive, CSF-1R-negative, mouse mammary epithelial cell line (HC11) expressing a high level of CSF-1, which was stably transfected with the mouse wild-type CSF-1R. Compared with parental cells, transfected cells expressing a wild-type CSF-1R invaded 100-fold more efficiently through a barrier of reconstituted basement membrane (Matrigel) and formed colonies in soft agar, whereas the cellular growth rate was only slightly increased. Analysis of cell-conditioned medium by zymography and quantitative enzyme activity assays showed that clones transfected with a wild-type CSF-1R expressed significantly higher levels of urokinase-type plasminogen activator than did untransfected clones. Furthermore, after injection into the tail veins of BALB/c mice, CSF-1R-expressing clones also produced a 10-fold higher incidence of lung tumors than the parental cell line. We also analyzed HC11 clones transfected with CSF-1R mutated at two major autophosphorylation sites (Tyr-->Phe807 and Tyr-->Phe721). Mutation at Tyr807 eradicated the stimulatory effect of Fms expression on the invasive ability of HC11 cells and substantially reduced the metastatic potential of the transfected clones but did not alter the Fms-induced anchorage-independent growth in soft agar. In contrast, mutation at Tyr721 of Fms had no effect on invasion as measured in the in vitro assay but markedly abolished Fms-induced colony formation in soft agar and eradicated the metastatic potential of the transfected clones. Our results suggest that expression of CSF-1R can facilitate cellular invasion and anchorage-independent growth in mammary epithelial cells, and these two processes are independently regulated by separate phosphotyrosine sites of CSF-1R.

3T3 Cells↗
PubMed1996

Genetic instability induced by the tumor microenvironment.

The tumor microenvironment is characterized by regions of fluctuating hypoxia, low pH, and nutrient deprivation. To determine the genetic consequences of growth under these conditions, we used a tumorigenic cell line carrying a recoverable, chromosomally based lambda phage shuttle vector designed to report mutations without the need for genetic selection of mutant cells. The cells were grown in parallel either in culture or as tumors in nude mice. The frequency of mutations arising in cells within the tumors was found to be 5-fold higher than that in otherwise identical cells grown in culture. A distinct pattern of mutation was also seen, with significantly more deletions and transversions in the tumors than in the cell cultures. Furthermore, exposure of the cultured cells to hypoxia produced an elevated mutation frequency and a mutation pattern similar to that seen in the tumors. These results indicate that the conditions within solid tumors are mutagenic and suggest that a fundamental mechanism of tumor progression in vivo is genetic instability induced by the tumor microenvironment.

Animals↗
PubMed1996

IL-11 enhances survival and decreases TNF production after radiation-induced thoracic injury.

We hypothesized that IL-11 would protect against radiation-induced thoracic injury. To test this hypothesis, we compared the survival of rIL-11 and vehicle-treated control mice after 25 Gy of thoracic irradiation, and initiated studies to elucidate the mechanism of the observed protection. This dose of radiation killed 50% of the control mice during the first 2 wk after irradiation. In contrast, the s.c. administration of rIL-11 resulted in significant radioprotection with 89% of the rIL-11-treated animals surviving the study interval (p < 0.001). This radioprotection was at least partially specific for normal thoracic structures since rIL-11 did not alter the development or radiosensitivity of EMT6 tumor cells growing as lung metastases. TNF mRNA was not detected in normal lungs but was impressively induced after thoracic irradiation. Treatment with rIL-11 abrogated this increase. Parallel in vitro studies demonstrated that rIL-11 inhibits LPS and radiation-induced macrophage TNF protein production and mRNA accumulation. These studies demonstrate that rIL-11 reduces the mortality following thoracic irradiation, without enhancing the development or diminishing the radiosensitivity of pulmonary metastatic tumors. They also demonstrate that rIL-11 inhibits both radiation-induced TNF mRNA expression in vivo and macrophage TNF protein production and mRNA accumulation in vitro, suggesting that the radioprotective effects of rIL-11 may be mediated, at least in part, via the modulation of TNF production.

Animals↗
PubMed1996

The immunophilin FKBP12 functions as a common inhibitor of the TGF beta family type I receptors.

The immunophilin FKBP12 is an evolutionarily conserved abundant protein; however, its physiological roles remain poorly defined. Here we report that FKBP12 is a common cytoplasmic interactor of TGF beta family type I receptors. FKBP12 binds to ligand-free TGF beta type I receptor, from which it is released upon a ligand-induced, type II receptor mediated phosphorylation of the type I receptor. Blocking FKBP12/type I receptor interaction with FK506 nonfunctional derivatives enhances the ligand activity, indicating that FKBP12 binding is inhibitory to the signaling pathways of the TGF beta family ligands. Overexpression of a myristylated FKBP12 in Mv1Lu cell specifically inhibits two separate pathways activated by TGF beta, and two point mutations on FKBP12 (G89P, I90K) abolish the inhibitory activity of FKBP12, suggesting that FKBP12 may dock a cytoplasmic protein to the type I receptors to inhibit TGF beta family mediated signaling.

Activin Receptors, Type I↗
PubMed1996

Bioactivation of mitomycin antibiotics by aerobic and hypoxic Chinese hamster ovary cells overexpressing DT-diaphorase.

DT-Diaphorase catalyzes a two-electron reduction of mitomycin C (MC) and porfiromycin (POR) to reactive species. Many cell lines that overexpress DT-diaphorase and are sensitive to the mitomycins are protected from the aerobic cytotoxicity of these drugs by the DT-diaphorase inhibitor dicumarol. The cytoprotective properties of this relatively non-specific inhibitor, however, vanish under hypoxic conditions. To ascertain the role of DT-diaphorase in mitomycin bioactivation and cytotoxicity in living cells, a rat liver DT-diaphorase cDNA was transfected into Chinese hamster ovary cells. MC was equitoxic to the parental cells under oxygenated and hypoxic conditions. In contrast, POR was less toxic than MC to these cells under aerobic conditions, but significantly more toxic than MC under hypoxia. Two DT-diaphorase-transfected clones displayed increases in DT-diaphorase activity of 126- and 133-fold over parental cells. The activities of other oxidoreductases implicated in mitomycin bioreduction were unchanged. MC was more toxic to both DT-diaphorase-transfected lines than to parental cells; the toxicity of MC to the transfected lines was similar in air and hypoxia. POR was also more toxic to the DT-diaphorase-elevated clones than to parental cells under oxygenated conditions. Under hypoxia, however, the toxicity of POR to the transfected clones was unchanged from that of parental cells. The findings implicate DT-diaphorase in mitomycin bioactivation in living cells, but suggest that this enzyme does not contribute to the differential toxicity of MC or POR in air and hypoxia.

Animals↗
PubMed1996

Differential toxicity of mitomycin C and porfiromycin to aerobic and hypoxic Chinese hamster ovary cells overexpressing human NADPH:cytochrome c (P-450) reductase.

Purified NADPH:cytochrome c (P-450) reductase (FpT; NADPH-ferrihemoprotein oxidoreductase, EC 1.6.2.4) can reductively activate mitomycin antibiotics through a one-electron reduction to species that alkylate DNA. To assess the involvement of FpT in the intracellular activation of the mitomycins, transfectants overexpressing a human FpT cDNA were established from a Chinese hamster ovary cell line deficient in dihydrofolate reductase (CHO-K1/dhfr-). The parental cell line was equisensitive to the cytotoxic action of mitomycin C under oxygenated and hypoxic conditions. In contrast, porfiromycin was considerably less cytotoxic to wild-type parental cells than was mitomycin C in air and markedly more cytotoxic under hypoxia. Two FpT-transfected clones were selected that expressed 19- and 27-fold more FpT activity than the parental line. Levels of other oxidoreductases implicated in the activation of the mitomycins were unchanged. Significant increases in sensitivity to mitomycin C and porfiromycin in the two FpT-transfected clones were seen under both oxygenated and hypoxic conditions, with the increases in toxicity being greater under hypoxia than in air. These findings demonstrate that FpT can bioreductively activate the mitomycins in living cells and implicate FpT in the differential aerobic/hypoxic toxicity of the mitomycins.

Aerobiosis↗
PubMed1996

Interactions of BMS-181174 and radiation: studies with EMT6 cells in vitro and in solid tumors.

N-7[2-(4-nitrophenyldithio)-ethyl] mitomycin C, (BMS-181174; previously designated as BMY25067) is a mitomycin C analog now in initial clinical trials. The experiments described in this report were performed to assess whether BMS-181174, like mitomycin C and porfiromycin, was selectively toxic to the hypoxic cells in solid tumors and might therefore prove valuable in combination with radiotherapy. In contrast to mitomycin C and porfiromycin, BMS-181174 was more toxic to aerobic EMT6 cells in vitro than to cells made acutely hypoxic. In vitro, BMS-181174 and radiation produced cytotoxicity compatible with either additive or slightly supra-additive cytotoxicity. In vivo, BMS-181174 was effective in killing cells in solid EMT6 tumors. The effects of regimens combining BMS-181174 and radiation in vivo were complex. Combinations of low doses of BMS-181174 plus a large dose of radiation were very effective in killing cells in solid tumors. However, the survival curve plateaued at high doses of BMS-181174, providing evidence for a subpopulation of tumor cells which were resistant to both BMS-181174 and radiation; this was hypothesized to be a hypoxic cell population.

Aerobiosis↗
PubMed1996

Hearing what cannot be seen: a psychoanalytic research group's inquiry into female sexuality.

Advances in the theoretical understanding of female psychology are not easily integrated into psychoanalytic practice. This paper reports on a study of female psychology and clinical practice by a group of seven female psychoanalysts. Through discussing the literature and case vignettes, we discovered a lag between current theoretical ideas and our clinical practice. The group identified an anachronistic emphasis on penis envy functioning as "bedrock." This report addresses how the group facilitated individual members' integration of theory and practice, and how this integration affected work with patients. We found that as we became open to considering a wider range of potential dynamic meanings of penis envy and female bodily concerns, we were able to explore a richer, and often surprising unfolding of vicissitudes. The discussion highlights some technical issues with this approach.

Fantasy↗
PubMed1995

Cytotoxicity of BMS-181174. Effects of hypoxia, dicoumarol, and repair deficits.

The mitomycin C (MC) analog BMS-181174 (previously designated as BMY25067) has been shown to be active against a variety of solid tumors in mice. The activity of this compound against tumor cell lines resistant to MC and the different toxicity profiles of BMS-181174 and MC suggested that there may be significant differences in the metabolism and the mechanisms of action of these two compounds. Our studies with a mouse mammary tumor cell line (EMT6), a wild-type Chinese hamster cell line (AA8), and three repair-deficient Chinese hamster cell lines (UV4, UV5, and EM9) supported this concept. BMS-181174 was more toxic to all five cell lines in air than in hypoxia; in contrast, MC is more toxic in hypoxia. Dicoumarol (which increases the cytotoxicity of MC in hypoxia and reduces the cytotoxicity of this drug in air) did not alter the cytotoxicity of BMS-181174. This finding suggests that neither DT-diaphorase nor cytochrome b5 reductase is involved in the activation of BMS-181174. Studies with the repair-deficient cell lines suggest that DNA strand breaks are not important to the cytotoxicity of BMS-181174, and that cross-links and adducts may be the critical lesions; these studies also suggest that the lethal lesions produced by BMS-181174 are the same under aerobic and hypoxic conditions.

Animals↗
PubMed1995

Preferential kill of hypoxic EMT6 mammary tumor cells by the bioreductive alkylating agent porfiromycin.

Hypoxic cells in solid tumors represent a therapeutically resistant population that limits the curability of many solid tumors by irradiation and by most chemotherapeutic agents. The oxygen deficit, however, creates an environment conducive to reductive processes; this results in a major exploitable difference between normal and neoplastic tissues. The mitomycin antibiotics can be reductively activated by a number of oxidoreductases, in a process required for the production of their therapeutic effects. Preferential activation of these drugs under hypoxia and greater toxicity to oxygen-deficient cells than to their oxygenated counterparts are obtained in most instances. The demonstration that mitomycin C and porfiromycin, used to kill the hypoxic fraction, in combination with irradiation, to eradicate the oxygenated portion of the tumor, produced enhanced cytodestructive effects on solid tumors in animals has led to the clinical evaluation of the mitomycins in combination with radiation therapy in patients with head and neck cancer. The findings from these clinical trials have demonstrated the value of directing a concerted therapeutic attack on the hypoxic fraction of solid tumors as an approach toward enhancing the curability of localized neoplasms by irradiation.

Animals↗
PubMed1995

Administration of a perfluorochemical emulsion plus carbogen breathing does not alter radiation pneumonitis.

The effects of treatment with a perfluorochemical emulsion plus carbogen on radiation pneumonitis were examined in a rat model system. Rats received thoracic irradiation (15 Gy) and radiation reactions in the lungs were assessed 25 and 35 days later using bronchoalveolar lavage and histologic assessments. The irradiated lungs showed the expected evidence of acute radiation pneumonitis, including protein leaks and also alveolar infiltrates and interstitial infiltrates. Administration of a perfluoro-chemical emulsion (Fluosol; 15 ml/kg) plus carbogen breathing for 30 min before and during irradiation did not enhance the reactions seen in the irradiated lungs.

Animals↗
PubMed1995

Cytotoxic potential of monoalkylation products between mitomycins and DNA: studies of decarbamoyl mitomycin C in wild-type and repair-deficient cell lines.

Hypoxic regions in solid neoplasms have been associated with tumor recurrence and resistance to several cancer treatment modalities including radiation therapy. Various strategies have been designed to target these resistant cells, including the use of the bioreductive alkylating agent mitomycin C (MC), which exerts preferential cytotoxicity under hypoxic conditions in most cell lines. Analyses of the mechanism of action of MC indicate that this drug can form cross-links with DNA; it is currently thought that this bisadduct is the critical lesion responsible for inhibiting DNA synthesis. Computer-generated models suggest that the MC adduct fits snugly into the minor groove of B-DNA without imposing major distortion on the structure of the DNA molecule. To gain additional insight into the role of cross-linkage in the cytotoxicity of MC, we studied the analogue, decarbomoyl mitomycin C (DMC). The structure of DMC is identical to that of MC with the exception of the substitution of the carbamoyl group at the C-10 position by a nonalkylating hydroxyl group (-OH); this alteration would be expected to prevent DMC from forming bisadducts with DNA. In chemical systems, DMC produces only DNA monoadducts. If indeed it is the MC-DNA cross-links which are responsible for cell kill, one would predict DMC to be less cytotoxic than MC. However, tissue culture studies using DMC revealed that DMC is at least as toxic as MC to EMT6 mouse mammary tumor cells and to wild-type AA8 Chinese hamster ovary (CHO) cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗