Biomedical subjects

M Dewhirst

Publications and source records attributed to M Dewhirst.

11 recordsLinked to original sources

PubMed2006

Apoptotic DNA fragmentation factor maintains chromosome stability in a P53-independent manner.

DNA fragmentation factor (DFF)/caspase-activated DNase (CAD) is responsible for DNA fragmentation, a hallmark event during apoptosis. Although DNA fragmentation is an evolutionarily conserved process across species, its biological function is not clearly understood. In this study, we constructed cell lines expressing a mutant ICAD (inhibitor of CAD) protein that is resistant to caspase cleavage and therefore constantly binds to DFF/CAD and inhibits DNA fragmentation. We found that irradiation of these cells led to increased chromosome aberrations and aneuploidy when compared with their parental controls. The increased chromosome instability is observed irrespective of cellular P53 status, suggesting that the effect of DFF/CAD is independent of P53. Inhibition of apoptotic DNA fragmentation resulted in increased clonogenic survival of irradiated cells and a delay in removal of cells with DNA damages induced by radiation, an effect similar to that in cells with p53 mutations. Consistent with DFF/CAD's effect on clonogenic survival, tumors established from cells deficient in DNA fragmentation showed enhanced growth in nude mice. Therefore, our results suggest that DFF/CAD plays an important and P53-independent role in maintaining chromosome stability and suppressing tumor development.

Aneuploidy↗

PubMed2000

Plasma D-dimer levels in operable breast cancer patients correlate with clinical stage and axillary lymph node status.

PURPOSE: To investigate the relationship between preoperative plasma D-dimer levels and extent of tumor involvement in operable breast cancer patients. PATIENTS AND METHODS: A total of 140 preoperative plasma specimens were obtained from women scheduled to undergo diagnostic breast biopsies. Ninety-five patients in the initial group went on to undergo axillary lymph node dissection. Of the 140 patients from whom plasma samples were obtained, 102 were subsequently diagnosed with invasive breast carcinoma, nine were subsequently diagnosed with ductal carcinoma-in-situ, and 20 were subsequently diagnosed with benign breast disease. Plasma D-dimer levels were quantitated using a commercially available immunoassay kit (DIMERTEST; American Diagnostica, Greenwich, CT). The relationships between plasma D-dimer and other prognostic variables (tumor size, estrogen receptor, progesterone receptor, nuclear grade, histologic grade, lymphovascular invasion, and clinical stage grouping) were then examined using univariate and multivariate linear and logistic regression analyses. RESULTS: Median plasma D-dimer levels were significantly higher in patients with invasive carcinoma than those patients with either benign breast disease or carcinoma-in-situ (P =.0001). A significant relationship existed between the presence of elevated D-dimer (> 100 ng/mL) and involved axillary lymph nodes (chi(2) test; P =.001). Elevated D-dimer levels predicted positive lymph node involvement in both univariate regression (P =.0035) and multivariate linear regression (P =.012) models. In addition, elevated D-dimer levels predicted the presence of lymphovascular invasion in univariate logistic regression (P =. 0025) and multivariate logistic regression analysis (P =.0053). Quantitative D-dimer levels were highly correlated with clinical stage grouping (analysis of variance test; P =.002). CONCLUSION: Plasma D-dimer levels were markers of lymphovascular invasion, clinical stage, and lymph node involvement in operable breast cancer. This correlation suggests that detectable fibrin degradation, as measured by plasma D-dimer, is a clinically important marker for lymphovascular invasion and early tumor metastasis in operable breast cancer.

Adult↗

PubMed1999

The treatment of high-grade soft tissue sarcomas with preoperative thermoradiotherapy.

PURPOSE: To explore the use of a novel program of preoperative radiation and hyperthermia in the management of high-grade soft tissue sarcomas (STS). METHODS AND MATERIALS: Eligible patients were adults over 18 with Grade 2 or 3 STS, surgically resectable without a local excision prior to referral to Duke University Medical Center and without distant metastases. Patients were staged generally with CT and/or MR imaging. The diagnosis was established with fine needle aspiration or incisional biopsy. Patients were then treated with 5000 to 5040 cGy, 180-200 cGy per fraction. Chemotherapy was usually not employed. Generally two hyperthermia treatments per week were given with a planned thermal dose of 10-100 CEM 43 degrees T90. Invasive thermometry and thermal mapping were done in all patients. Surgical resection was planned 4-6 weeks after the completion of radiation and hyperthermia. RESULTS: Ninety-seven patients were treated on study between 1984 and 1996. Follow-up ranged from 12 to 155 months (median 32). All tumors were high-grade in nature, 44 greater than 10 cm in size (maximum tumor diameter), 43 5-10 cm in size, 10 less than 5 cm. Seventy-eight of the 97 tumors were located in an extremity. Of the 97 patients, 48 remain alive and continually free of disease following initial therapy. Of the remaining 49 patients, 44 have relapsed (34 dead, 10 living with disease), 3 have died secondary to complications of therapy, and 2 have died of unrelated causes. Ten-year actuarial overall survival, cause-specific survival, and relapse-free survival are 50, 47, and 47% respectively. The predominant pattern of failure has been distant metastases with only 2 patients developing local failure alone. Ten-year actuarial local control for extremity tumors is 94%, 63% for the 19 patients with tumors at sites other than the extremity. Of the 78 patients with extremity lesions, 63 have had limb preservation and remain locally controlled. Overall 38 patients experienced 57 major complications. There were 3 deaths, one due to adriamycin cardiomyopathy and two secondary to wound infections. Four patients required amputation secondary to postoperative wound healing problems. Complications directly attributable to hyperthermia occurred in 15 patients with 11 instances of second- or third-degree burns and two instances of subcutaneous fat necrosis. The hyperthermia complications were generally not severe and either healed readily or were excised at the time of surgical resection of the primary tumor. CONCLUSIONS: For these aggressive high-grade soft tissue sarcomas, this treatment program of preoperative thermoradiotherapy provided excellent local regional control for extremity lesions (95%) and satisfactory local regional control (63%) of nonextremity sarcomas, but did not appear to influence the rate of distant metastases or survival. Complications were frequent but apart from the direct thermal burns, not too different from those reported for preoperative radiotherapy alone. More effective adjuvant systemic therapy is necessary to impact favorably on survival.

Adult↗

PubMed1999

Ascaris haemoglobin is a nitric oxide-activated 'deoxygenase'.

The parasitic nematode Ascaris lumbricoides infects one billion people worldwide. Its perienteric fluid contains an octameric haemoglobin that binds oxygen nearly 25,000 times more tightly than does human haemoglobin. Despite numerous investigations, the biological function of this molecule has remained elusive. The distal haem pocket contains a metal, oxygen and thiol, all of which are known to be reactive with nitric oxide. Here we show that Ascaris haemoglobin enzymatically consumes oxygen in a reaction driven by nitric oxide, thus keeping the perienteric fluid hypoxic. The mechanism of this reaction involves unprecedented chemistry of a haem group, a thiol and nitric oxide. We propose that Ascaris haemoglobin functions as a 'deoxygenase', using nitric oxide to detoxify oxygen. The structural and functional adaptations of Ascaris haemoglobin suggest that the molecular evolution of haemoglobin can be rationalized by its nitric oxide related functions.

Anaerobiosis↗

PubMed1997

Inhibition of tumor angiogenesis using a soluble receptor establishes a role for Tie2 in pathologic vascular growth.

Tie2 is a novel receptor tyrosine kinase that is expressed almost exclusively by vascular endothelium. Disruption of Tie2 function in transgenic mice resulted in embryonic lethality secondary to characteristic vascular defects; similar defects occurred after disruption of the Tie2 ligand. These findings indicate that the Tie2/Tie2 ligand pathway plays important roles during development of the embryonic vasculature. To determine whether the Tie2 pathway was involved in pathologic angiogenesis in adult tissues, a soluble form of the extracellular domain of murine Tie2 (ExTek.6His) was developed and used as a Tie2 inhibitor. After a single application of the ExTek.6His protein into a rat cutaneous window chamber, growth of a mammary tumor inside the chamber was reduced by > 75% (P < 0.005), and tumor vascular length density was reduced by 40% when compared with control-treated tumors (P < 0.01). In the rat cornea, ExTek.6His blocked angiogenesis stimulated by tumor cell conditioned media. ExTek.6His protein did not affect the viability of cultured tumor cells, indicating that the antitumor effect of ExTek.6His was due to the inhibition of tumor angiogenesis. These data demonstrate a role for the Tie2 pathway in pathologic angiogenesis, suggesting that targeting this pathway may yield effective antiangiogenic agents for treatment of cancer and other angiogenic diseases.

Animals↗

PubMed1993

Development of a model of melphalan-induced gastrointestinal toxicity in mice.

The tolerated dose of melphalan is limited by bone marrow suppression; when this complication is ameliorated by bone marrow transplantation, the dose-limiting toxicity becomes gastrointestinal mucositis. No intervention to date has been successful in modulating this life-threatening complication of melphalan. We conducted studies to develop a murine model of melphalan-induced gastrointestinal toxicity to facilitate the preclinical identification of effective strategies for reducing this toxicity. Melphalan given at the 90% lethal dosage produced severe gastrointestinal mucositis and mortality (13 of 23 treated mice). Syngeneic bone marrow transplantation, effective in preventing the myeloablation produced by total-body irradiation, was ineffective in preventing melphalan-induced mortality (16 of 23 treated mice), indicating that gastrointestinal mucositis was the dose-limiting toxicity. On the basis of the results of previous studies, which revealed that depletion of glutathione enhances the antineoplastic activity of melphalan and that glutathione is required for murine intestinal function, we attempted to modulate melphalan-induced gastrointestinal toxicity by the administration of glutathione (8-10 mmol/kg given in 1 ml sterile water by gavage at 12-h intervals for 4-8 doses). Glutathione therapy failed to produce a significant increase in mucosal glutathione content in animals treated with melphalan plus glutathione gavage as compared with those receiving melphalan alone (P > 0.05), and histologic mucosal injury secondary to melphalan was not reduced. The administration of glutathione in the presence or absence of concomitant bone marrow transplantation did not decrease melphalan-induced mortality (melphalan alone, 16/26 deaths; melphalan plus glutathione, 14/25 deaths; melphalan plus glutathione plus bone marrow transplantation, 20/26 deaths). Studies using a reduced melphalan dose (50% lethal dosage) produced similar results, with no survival benefit being seen following glutathione administration. Our studies suggest that melphalan-induced mucositis can be studied in a mouse model in which this complication is dose-limiting. Although glutathione administration at the dose and schedules initially studied is not effective in reducing this damage, other therapeutic strategies such as the use of alternative glutathione regimens or other thiols can be effectively studied in this system.

Animals↗

PubMed1992

Relationships among tumor temperature, treatment time, and histopathological outcome using preoperative hyperthermia with radiation in soft tissue sarcomas.

The lack of an unambiguous thermal dosimetry continues to impede progress in clinical hyperthermia. In an attempt to define better this dosimetry, a model based on the cumulative minutes during which arbitrary percentages of measured tumor temperature points exceeded an index temperature was tested in patients with soft tissue sarcomas treated with preoperative hyperthermia and conventional radiation therapy. Patients received 5000-5040 cGy at 180-200 cGy per fraction. Hyperthermia was delivered 30-60 minutes after radiation therapy and given for 60 minutes. Patients were randomized between one and two hyperthermia treatments per week for a total of five or 10 treatments, respectively. Lesions were excised 4-6 weeks after completion of hyperthermia/radiation therapy. Successful treatment outcome was considered to be the finding of greater than 80% necrosis of the sarcoma upon histopathologic examination of the resected specimen. Forty-five patients were eligible with thermometry data available in 44 patients. An average of 19 interstitial sites were monitored each treatment per tumor. Sixty percent of tumors had a successful histopathologic outcome. Univariate analysis demonstrated that several descriptors of the temperature distribution were strongly related to treatment outcome; more strongly than nonthermometric factors, such as the number of treatments per week, tumor volume and patient age and more strongly than the commonly used temperature descriptors Tmin and Tmax. Descriptors that incorporated both temperature and time were also superior to the more commonly used descriptors Tmin and Tmax. Multivariate stepwise logistic regression analysis revealed that a descriptor of both the hyperthermia treatment time and the frequency distribution of intratumoral temperatures was the strongest predictor of histopathologic outcome and that the best predictive model combined this time/temperature descriptor and one versus two treatment per week grouping. The more conventional temperature descriptor, minimum measured tumor temperature, did not significantly enhance the predictive power of treatment group. Based on these results, we recommend that descriptors based on both the frequency distribution of intratumoral temperatures and hyperthermia treatment time be tested for relationships with treatment outcome in other clinical data bases. Furthermore, we recommend that temperature descriptors that are less sensitive to catheter placement and tumor boundary identification than Tmin and Tmax (such as T90, T50, and T10) be tested prospectively along with other important thermal variables in Phase II trials in further efforts to define a thermal dosimetry for spatially nonuniform temperature distributions.

Combined Modality Therapy↗

PubMed1991

Accelerated repopulation: friend or foe? Exploiting changes in tumor growth characteristics to improve the "efficiency" of radiotherapy.

Accelerated repopulation (rapid multiplication of surviving clonogens) during a course of radiation therapy may contribute to local failure. This possibility has prompted accelerated treatment programs in an attempt to reduce overall treatment time, thereby minimizing the impact of repopulation. However, accelerated dose delivery at the start of treatment may not be advantageous since many of the tumor cells are likely to be hypoxic (non-cycling cells) and therefore relatively radioresistant. Conversely, accelerated treatment is likely to be most helpful later in treatment when the tumor has shrunk and accelerated repopulation of clonogens is a dominant factor. A series of calculations are presented that stimulate changes in tumor size, clonogen number, clonogen repopulation, and growth fraction during a course of fractionated radiation treatments for an idealized 2 cm diameter spherical tumor. The efficiency of each fraction of radiation is calculated for different radiation fractionation schemes. Efficiency is defined as the change in Log clonogen number (reflecting cell death due to radiation minus repopulation that has occurred during the interval between fractions) per Gy. These calculations suggest that relatively low total daily doses (approximately 2 Gy) are most efficient early in treatment. Higher daily doses are less efficient since the growth fraction is relatively low at the start of treatment. Later in treatment, as the tumor shrinks and the growth fraction approaches 1, accelerated repopulation becomes a major problem and higher total daily doses are more efficient. At this point, accelerated hyperfractionation should be used to increase the daily dose without exposing normal tissues to high fraction sizes. Thus, changes in tumor growth characteristics are exploited and dose delivery can be optimized by escalating daily irradiation doses during a course of fractionated irradiation. Strict interpretation of these conclusions must be tempered by the various assumptions and uncertainties included in this model. The concept of efficiency is useful since it reflects the competing effects of clonogen repopulation and radiation induced clonogen sterilization.

Cell Division↗

PubMed1990

Soft-tissue sarcomas: detection of metabolic heterogeneity with P-31 MR spectroscopy.

Regional variations in metabolic parameters derived with multivoxel, localized phosphorus-31 magnetic resonance (MR) spectroscopy in spontaneous human-soft-tissue sarcomas were compared with variations in the same parameters in normal human legs. In addition, multivoxel P-31 MR spectroscopy of transplanted rodent sarcomas and microelectrode measurement of pH and PO2 in several locations within them were performed, and, when appropriate, results were compared with the clinical data. Striking voxel-voxel variability in parameters derived with P-31 spectroscopy was found in tumors, with less marked variability seen in normal legs. In the rodent tumors, spatial variations also were found in pH and PO2 measured by means of microelectrodes. These data are consistent with the results of regional measurements in tumors by means of other methods and suggest that clinical MR spectroscopic studies of tumors may need to consider the variability within malignant lesions.

Animals↗

PubMed1989

Hyperthermia quality assurance guidelines.

These Hyperthermia Quality Assurance guidelines are a result of a joint workshop of the Hyperthermia Committee of the American College of Radiology and the Hyperthermia Physics Center, which is the national quality assurance program under Contract No. N01-CM-37512 with the National Cancer Institute. Hyperthermia technology presently lacks the kind of standardization in equipment, treatment procedures, patient monitoring, and treatment documentation available in radiotherapy. Therefore, preventing unacceptable variability in treatment data demands a strong commitment to in-house quality control procedures and to centralized quality assurance reviews in cooperative multi-institutional trials. This paper presents a set of test procedures necessary to ensure proper operation of equipment, suggests a frequency for such tests, and also includes guidelines on quality control procedures to be used during treatment to improve the safety, effectiveness, and reproducibility of hyperthermia treatments. A set of forms are presented to indicate the minimum data, albeit incomplete, that must be collected for acceptable documentation of treatment. These guidelines should be valuable not only to the new entrants in the field but also to those participating in multi-institutional cooperative hyperthermia trials. They have been approved by the Hyperthermia Committees of American College of Radiology, American Society for Therapeutic Radiology and Oncology, Radiation Therapy Oncology Group and the American Association of Physicists in Medicine.

Forms and Records Control↗

PubMed1984

The effect of rate of heating or cooling prior to heating on tumor and normal tissue microcirculatory blood flow.

Single vessel responses to hyperthermia were studied in tumor and normal tissues using a transparent access window chamber. Rates of heating less than or equal to .68 degrees C/minute preserved relatively better vascular function in normal than tumor tissue. A rate of heating of 1.0 degrees C/minute lowered normal tissue statis temperatures so they were no different from tumor. Cooling to 30 degrees C prior to heating slowed normal arteriolar flows to less than 5% of 38 degrees C controls. Heating resulted in increased flow in those vessels, but maximum flows never exceeded 5% of flows achieved in similar vessels which were not cooled first. The implications of this work are that rate of heating and cooling prior to heating can alter normal tissue vascular response to heat in a way that could prove deleterious to maintaining efficient vascular function in that tissue relative to tumor.

Adenocarcinoma↗