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Biomedical subjects

K M McMasters

Publications and source records attributed to K M McMasters.

At least 55 records · Page 3Linked to original sources
PubMed2000

Sentinel lymph node biopsy for breast cancer: a suitable alternative to routine axillary dissection in multi-institutional practice when optimal technique is used.

PURPOSE: Previous studies have demonstrated the feasibility of sentinel lymph node (SLN) biopsy for nodal staging of patients with breast cancer. However, unacceptably high false-negative rates have been reported in several studies, raising doubt about the applicability of this technique in widespread surgical practice. Controversy persists regarding the optimal technique for correctly identifying the SLN. Some investigators advocate SLN biopsy using injection of a vital blue dye, others recommend radioactive colloid, and still others recommend the use of both agents together. PATIENTS AND METHODS: A total of 806 patients were enrolled by 99 surgeons. SLN biopsy was performed by single-agent (blue dye alone or radioactive colloid alone) or dual-agent injection at the discretion of the operating surgeon. All patients underwent attempted SLN biopsy followed by completion level I/II axillary lymph node dissection to determine the false-negative rate. RESULTS: There was no significant difference (86% v 90%) in the SLN identification rate among patients who underwent single- versus dual-agent injection. The false-negative rates were 11.8% and 5.8% for single- versus dual-agent injection, respectively (P <.05). Dual-agent injection resulted in a greater mean number of SLNs identified per patient (2. 1 v 1.5; P <.0001). The SLN identification rate was significantly less for patients older than 50 years as compared with that of younger patients (87.6% v 92.6%; P =.03). Upper-outer quadrant tumor location was associated with an increased likelihood of a false-negative result compared with all other locations (11.2% v 3. 9%; P <.05). CONCLUSION: In multi-institutional practice, SLN biopsy using dual-agent injection provides optimal sensitivity for detection of nodal metastases. The acceptable SLN identification and false-negative rates associated with the dual-agent injection technique indicate that this procedure is a suitable alternative to routine axillary dissection across a wide spectrum of surgical practice and hospital environments.

Axilla↗
PubMed2000

Adenovirus-mediated E2F-1 gene transfer induces an apoptotic response in human gastric carcinoma cells that is enhanced by cyclin dependent kinase inhibitors.

E2F -1 is a transcription factor that regulates cell cycle progression into S-phase. Deregulation of E2F-1 activity has been associated with cellular commitment to apoptosis. Also critical in the regulation of S-phase are the actions of the cyclin dependent kinases, Cdk2 and cdc2. Inhibition of these cyclin dependent kinases has been similarly associated with disrupting orderly S-phase progression and causing subsequent apoptosis in certain cancer cells. In this study, we examine the ability of adenovirus-mediated E2F-1 overexpression to induce apoptosis in human gastric carcinoma cells. Furthermore, we investigate the effect of the cyclin dependent kinase inhibitors, olomoucine and roscovitine, on E2F-1-mediated apoptosis in human gastric carcinoma cells. AGS and SNU-1 gastric adenocarcinoma cells were infected with adenoviral vectors expressing E2F-1 (Ad5CMVE2F-1) or control viruses expressing beta-galactosidase (Ad5CMVLacZ) or lacking a transgene (Ad5). Gastric adenocarcinoma cells were then independently treated with roscovitine or olomoucine. Finally, gastric adenocarcinoma cells were infected with the various adenoviral vectors in combination with roscovitine or olomoucine. E2F-1 overexpression resulted in an 85% reduction in cell viability at 72 h compared to controls. Combining E2F-1 overexpression with roscovitine resulted in >99% reduction in cell viability by 72 h. Overexpression of E2F-1 resulted in premature S-phase entry and G2/M arrest at 24 h, followed by apoptosis by 72 h. Combining E2F-1 overexpression with roscovitine resulted in an earlier G2/M arrest, followed by a more complete, widespread apoptotic response by 24 h. Caspase 3/CPP32 activation and PARP cleavage in response to E2F-1 overexpression, alone and in combination with roscovitine, implicate the caspase cascade in E2F-1-mediated apoptosis of gastric cancer cells. Bax levels also increased in response to E2F-1 gene transfer, alone and in combination with roscovitine. E2F-1 overexpression induces widespread apoptosis in human gastric carcinoma cells. Combining E2F-1 overexpression with cyclin-dependent kinase inhibitors results in an enhanced apoptotic response, causing nearly complete gastric tumor cell death within 72 h. E2F-1 gene therapy in combination with cyclin dependent kinase inhibitors is a potentially active chemogene therapy strategy for the treatment of human gastric cancer.

Adenoviridae↗
PubMed2000

Caspase activation and changes in Bcl-2 family member protein expression associated with E2F-1-mediated apoptosis in human esophageal cancer cells.

The prognosis for patients with esophageal cancer remains poor, prompting the search for new treatment strategies. Overexpression of E2F-1 has been shown to induce apoptosis in several cancer cell types. In the present study, the effect of adenovirus-mediated E2F-1 overexpression on human esophageal cancer cell lines Yes-4 and Yes-6 was evaluated. Cells were treated by mock infection, infection with an adenoviral vector expressing beta-galactosidase (Ad5CMV-LacZ), or E2F-1 (Ad5CMVE2F-1). Western blot analysis confirmed marked overexpression of E2F-1 in Ad5CMVE2F-1-infected cells. Overexpression of E2F-1 resulted in marked growth inhibition and rapid loss of cell viability due to apoptosis, although Yes-6 cells were somewhat more resistant to E2F-1-mediated growth inhibition than Yes-4 cells. Cell cycle analysis revealed that overexpression of E2F-1 led to G2 arrest, followed by apoptotic cell death. p53 expression remained undetectable in both cell lines after E2F-1 overexpression. The apoptosis inhibitor proteins of the Bcl-2 gene family, Bcl-2, Mcl-1, and BcI-XL, decreased at 48 h after infection in Yes-4 cells, but remained unchanged in Yes-6 cells. Levels of retinoblastoma gene product (pRb) declined at 48 h after E2F-1 infection in Yes-4 cells, at which apoptosis predominated, whereas pRb expression remained constant in Yes-6 cells. Expression of p14ARF did not change after E2F-1 infection in either cell line. Involvement of caspase 3 and caspase 6 in E2F-1-mediated apoptosis was demonstrated by cleavage of caspase 3/CPP32 and poly-ADP-ribose polymerase, as well as fragmentation of the caspase 6 substrate, lamin B. These results indicate that the sensitivity of esophageal cancer cells to E2F-1-mediated apoptosis may be related to differential expression of Bcl-2 family member proteins and suggest that the adenovirus-mediated E2F-1 gene therapy may be a promising treatment strategy for the treatment of this disease.

Adenoviridae↗
PubMed2000

The role of the ultrasonically activated shears and vascular cutting stapler in hepatic resection.

Hemorrhage and liver failure are the two greatest concerns for patients undergoing major liver resection. Inflow occlusion (Pringle maneuver) is often used to minimize blood loss, but hepatic ischemia results in an increased risk of postoperative hepatic dysfunction. We report our experience with the Harmonic Scalpel ultrasonically activated shears (UAS; Ethicon Endo-Surgery, Cincinnati, OH) and a vascular stapler for hepatic resection as technological advances that aid in minimizing blood loss and thereby reduce the need for inflow occlusion. We retrospectively reviewed liver resections performed from September 1997 through July 1998, in which the UAS and articulating vascular endoscopic linear cutting stapler were used. The vascular stapler was used to divide the appropriate portal vein branch and hepatic vein(s) before parenchymal transection. Parenchymal dissection was performed with UAS to a depth of approximately 2 to 3 cm, and the remainder of the liver parenchyma was divided by a clamp crush and clip and suture ligate technique. Patients underwent segmental resection (n = 12), lobectomy (n = 13), or extended lobectomy (n = 11). Resection was performed for metastatic disease, primary liver tumors, or benign disease in 21, 8, and 7 patients, respectively. A Pringle maneuver was performed in 7 of 36 patients (mean clamp time, 8 minutes). The median required intraoperative blood transfusion was 0 units of packed red blood cells. Major and minor complications occurred in 12 and 3 patients, respectively. Two deaths were related to pneumonia and abdominal infection. The vascular stapler safely and securely divides portal vein branches and hepatic veins. The UAS initiates parenchymal transection with minimal blood loss. These two technologies facilitate the surgeon's aim of liver resection without blood transfusion or Pringle maneuver.

Blood Loss, Surgical↗
PubMed1999

Adenovirus-mediated E2F-1 gene transfer efficiently induces apoptosis in melanoma cells.

BACKGROUND: E2F-1 is a transcription factor that stimulates cellular proliferation and cell cycle progression from G(1) to S-phase. Somewhat paradoxically, E2F-1 also has the properties of a tumor suppressor. Overexpression of E2F-1 has been shown to induce apoptosis in some cancer cells. In the current study, the effect of adenovirus-mediated E2F-1 gene transfer on human melanoma cell growth was investigated. METHODS: Two human melanoma cell lines, SK-MEL-28 (wild-type p53) and SK-MEL-2 (mutant p53), were treated by mock infection, infection with a control vector expressing the beta-galactosidase gene (Ad5CMV-LacZ), or infection with a vector expressing E2F-1 (Ad5CMV-E2F-1) at a multiplicity of infection of 100. Cell proliferation and viability were determined by WST-1 assay and trypan blue exclusion, respectively. Apoptosis was assessed by cell flow cytometry and confirmed by cell morphology, in situ terminal deoxynucleotidyl nick end labeling assay, and poly(ADP-ribose) polymerase cleavage assay. RESULTS: Marked overexpression of E2F-1 was evident in both cell lines 24 hours after infection with Ad5CMVE2F-1 by Western blot analysis. E2F-1 overexpression resulted in growth inhibition and rapid loss of cell viability. Overexpression of E2F-1 also resulted in premature S-phase entry and G(2) arrest at 24 hours followed by apoptotic cell death at 48 hours. After Ad5CMVE2F-1 infection, expression of Bax and Bak was unchanged, whereas Mcl-1 levels decreased markedly. In SK-MEL-28 cells, Bcl-XL levels also declined after E2F-1 expression. Bcl-2 was undetectable in SK-MEL-28 cells but was increased in SK-MEL-2 cells in response to E2F-1 overexpression. CONCLUSIONS: Adenovirus-mediated E2F-1 gene transfer efficiently induces widespread apoptosis in human melanoma cells. E2F-1 overexpression induced apoptosis in cell lines containing wild-type and mutant p53, suggesting that this effect does not require wild-type p53 function. Anti-apoptotic proteins of the Bcl-2 family, notably Mcl-1 and Bcl-XL, may be involved in mediating the response to E2F-1. These data suggest that adenovirus-mediated E2F-1 gene therapy may be effective in the treatment of melanoma.

Adenovirus E2 Proteins↗
PubMed1999

Acceptable regret in medical decision making.

When faced with medical decisions involving uncertain outcomes, the principles of decision theory hold that we should select the option with the highest expected utility to maximize health over time. Whether a decision proves right or wrong can be learned only in retrospect, when it may become apparent that another course of action would have been preferable. This realization may bring a sense of loss, or regret. When anticipated regret is compelling, a decision maker may choose to violate expected utility theory to avoid regret. We formulate a concept of acceptable regret in medical decision making that explicitly introduces the patient's attitude toward loss of health due to a mistaken decision into decision making. In most cases, minimizing expected regret results in the same decision as maximizing expected utility. However, when acceptable regret is taken into consideration, the threshold probability below which we can comfortably withhold treatment is a function only of the net benefit of the treatment, and the threshold probability above which we can comfortably administer the treatment depends only on the magnitude of the risks associated with the therapy. By considering acceptable regret, we develop new conceptual relations that can help decide whether treatment should be withheld or administered, especially when the diagnosis is uncertain. This may be particularly beneficial in deciding what constitutes futile medical care.

Brain Ischemia↗
PubMed1999

Adenovirus-mediated E2F-1 gene transfer inhibits MDM2 expression and efficiently induces apoptosis in MDM2-overexpressing tumor cells.

The oncoprotein MDM2 binds and inactivates p53. MDM2 also binds to the tumor suppressor pRB, as well as E2F-1. E2F-1 is a transcription factor that regulates S phase entry and has been shown to cause apoptosis in some cell types when overexpressed. To investigate the effect of adenovirus-mediated E2F-1 overexpression, MDM2-overexpressing tumor cell lines were treated by mock infection, infection with an adenoviral vector expressing beta galactosidase, or E2F-1 (Ad5CMV-E2F-1). Western blot analysis confirmed significant overexpression of E2F-1 in Ad5CMV-E2F-1-infected cells. E2F-1 overexpression resulted in marked growth inhibition and rapid loss of cell viability. Ad5CMV-E2F-1 infection resulted in early S phase entry, followed by apoptotic cell death. E2F-1 overexpression was associated with a marked decrease in MDM2 levels and no evidence of increased Bax levels, whereas p53 and Bcl-2 levels remained undetectable. Cleavage of poly-ADP-ribose polymerase and caspase 3/CPP32 implicated activation of the caspase cascade in E2F-1-mediated apoptosis. These results indicate that adenovirus-mediated E2F-1 overexpression in MDM2-overexpressing tumor cells results in decreased MDM2 expression and widespread apoptosis. Because MDM2-overexpressing tumors are often resistant to p53 gene therapy, adenovirus-mediated E2F-1 gene therapy may be a promising alternative strategy.

Adenoviridae↗
PubMed1999

Management issues regarding hepatic adenomatosis.

Hepatic adenomatosis is a rare disease defined by multiple hepatic adenomas. There is controversy with regard to the optimal treatment for this disease because the potential for intraperitoneal hemorrhage or malignant transformation of the tumors is difficult to estimate. Furthermore, the technical difficulties of complete resection of all adenomas present unique operative challenges. We report experience with two patients and reviewed all reported cases from 1977. We define hepatic adenomatosis as five or more hepatic adenomas not associated with a medical history of glycogen storage disease, anabolic steroid use, or oral contraceptive use. The incidence of hepatic adenomatosis was preponderate among women [20 of 32 patients (63%)]. Thirteen of 32 patients (41%) had intratumoral bleeding, including four patients with intraperitoneal hemorrhage. Ten of 13 patients (77%) with intratumoral bleeding complained of abdominal pain; overall, 19 of 32 patients (59%) had abdominal pain. Twelve patients underwent hepatic resection, 6 patients underwent liver transplantation with no reported mortality, and 14 patients had no surgical treatment. Hepatocellular carcinoma was histologically confirmed in 2 of 32 patients (6%). Larger symptomatic adenomas exposed to liver surface have a bleeding propensity and should be surgically resected. Routine biopsy of other small nodules suspected as adenomas is recommended for definitive diagnosis.

Adenoma↗
PubMed1999

Primary squamous cell carcinoma of the breast presenting as a breast abscess.

Primary squamous cell carcinoma (SCC) of the breast is a very rare neoplasm, with only 75 cases reported in the English literature. Herein, we report four new cases and discuss the diagnostic and therapeutic challenges of this unusual tumor in a retrospective review of all cases of SCC of the breast at our institution from 1990 to 1998. Four patients with breast SCC were identified, with a mean age of 70 years. Two patients with "pure" SCC (no features of ductal carcinoma) were initially treated for breast abscess. Two other patients with features of both SCC and ductal carcinoma had skin erythema associated with an underlying mass, and infectious etiology was considered in each case. Mean tumor size was 4.9 cm. Both patients with pure SCC underwent extensive evaluation for primary tumors at other sites. Two patients developed early systemic metastasis. SCC of the breast is often diagnosed at an advanced stage and may be confused with breast abscess. For this reason, breast biopsy should be considered in cases of breast abscess. Treatment of primary SCC of the breast is similar to that of more common types of breast cancer (i.e., breast conservation is possible and lymph node dissection is recommended). Because metastasis to the breast from other primary tumor sites has been reported (lung, cervix, skin, and esophagus), patients with pure SCC should undergo evaluation to exclude this possibility.

Abscess↗
PubMed1998

Exclusion of a p53 germline mutation in a classic Li-Fraumeni syndrome family.

Li-Fraumeni syndrome (LFS) is characterized by a high risk of sarcomas, early onset of breast cancer, and a diversity of other cancers occurring as multiple primary tumors in multiple family members. In many families with LFS, germline mutations within the tumor-suppressor gene p53 have been identified. However, mutations in p53 have not been detected in approximately 30% of LFS families. To address the possibility either that p53 mutations were being missed or that another predisposing gene is altered in LFS, we used a variety of methods to accurately determine the p53 status in a large LFS kindred. A transcriptional activation assay on exons 4-10 of p53 excluded a mutation within the DNA-binding domain of p53. Single-stranded conformational-polymorphism analysis, using intronic primers and sequencing of all the coding exons and intron/exon junctions, also yielded no mutations. Finally, linkage analysis excluded potential mutations in the noncoding regions of p53. Our findings exclude the presence of a p53 germline mutation in a classic LFS family.

Adult↗
PubMed1997

Oral presentations for surgical meetings.

Each year the Association for Academic Surgery sponsors the "Fundamentals of Surgical Research" course which is established for residents who are beginning research training. A lecture outlining various aspects of effective scientific presentations, such as that delivered at a national or regional surgical meeting, is part of the course. Faculty from our institution have organized this lecture for several years. The lecture content has been revised each year to reflect the recommendations of the participating residents and faculty. Herein, we summarize the requirements for composing and delivering a scientific surgical presentation that is noted for its clarity, easily understood methods, interpretable data, and scientific and/or clinical implications.

Communication↗
PubMed1997

Neoadjuvant chemoradiation for extrahepatic cholangiocarcinoma.

BACKGROUND: The prognosis for patients with extrahepatic bile duct cancer remains poor. The purpose of this study was to evaluate our initial results with preoperative chemoradiation for extrahepatic cholangiocarcinoma, in the context of our experience with conventional treatment of this disease over the past 13 years. METHODS: From 1983 through 1996, analysis of all patients treated for extrahepatic cholangiocarcinoma was performed. RESULTS: Of 91 total patients, 51 had unresectable disease and 40 underwent resection. Median survival was significantly different for patients who underwent resection (22.2 months) versus those treated palliatively (10.7 months; P <0.0001). Nine patients underwent preoperative chemoradiation (5 perihilar, 4 distal) prior to resection. Three patients in the preoperative chemoradiation group had a pathologic complete response, while the remainder showed varying degrees of histologic response to treatment. The rate of margin-negative resection was 100% for the preoperative chemoradiation group versus 54% for the group who did not receive preoperative chemoradiation (P <0.01). There were no major intra-abdominal complications in the patients treated with preoperative chemoradiation. CONCLUSIONS: These results suggest that preoperative chemoradiation for extrahepatic bile duct cancer can be performed safely, produces significant antitumor response, and may improve the ability to achieve tumor-free resection margins. Additional trials of preoperative chemoradiation are warranted.

Adult↗
PubMed1997

En bloc pancreaticoduodenectomy and colectomy for duodenal neoplasms.

Duodenal malignancy is rare and generally considered to have both a low resectability rate and a poor prognosis. Historically, the involvement of the colon or its mesentery has been considered a criterion for unresectability by many surgeons because of the overall magnitude of surgery involved with an en bloc colectomy and pancreaticoduodenectomy. In the past few years, several reports have noted a decrease in morbidity and mortality rates for pancreaticoduodenectomy. The current safety of the procedure suggests that the classical criteria for resectability can now be reevaluated for certain neoplasms. We report two cases of pancreaticoduodenectomy with en bloc colectomy done as attempted curative resections for primary duodenal malignancies. The procedure was well tolerated by both patients; there were no major complications, and it provided both prolonged survival and effective palliation.

Adenocarcinoma↗
PubMed1996

mdm2 deletion does not alter growth characteristics of p53-deficient embryo fibroblasts.

The mdm2 gene encodes a protein that is necessary for the negative regulation of p53 function in vivo. Deletion of the mdm2 gene in mice results in early embryonic death while concomitant mdm2 and p53 deletion results in viable offspring. The viability of these mice prompted us to ask if MDM2 had an important growth regulatory function independent of p53. We established mouse embryo fibroblasts null for both p53 and mdm2 and compared them with p53-null fibroblasts. The cells did not differ in their growth rates or their ability to bypass a G1 arrest. Both cell lines formed colonies efficiently when plated at low density and showed a similar degree of genetic instability. Thus, the analysis of several growth parameters indicated no difference between p53-null and p53/mdm2-null cell lines.

Animals↗
PubMed1996

Liver cryosurgery.

Liver cryosurgery is a relatively new form of treatment for unresectable liver cancer that involves in situ ablation of liver tumors by freezing them with liquid nitrogen. Cryosurgery has been used mainly to treat liver metastases from colorectal cancer, but other types of metastases and primary liver cancers have been treated as well. Results of liver cryosurgery over the past decade have demonstrated that it is a safe and effective treatment for malignant liver tumors. Because only a small percentage of primary and metastatic liver tumors are resectable, cryosurgery offers a potentially curative treatment option for patients with unresectable disease.

Chemotherapy, Adjuvant↗
PubMed1994

Tissue tumor necrosis factor mRNA expression following cecal ligation and puncture or intraperitoneal injection of endotoxin.

Tumor necrosis factor (TNF) has been implicated as a key mediator of the septic response. Although very high serum levels of TNF are detected in animal models of endotoxemia or gram-negative bacteremia, human patients with sepsis rarely have greatly elevated TNF serum levels. It has therefore been postulated that TNF may act in a paracrine fashion to cause local injury. In order to examine the role of locally produced TNF in sepsis, we compared serum TNF levels and TNF messenger RNA (mRNA) expression in various tissues following cecal ligation and puncture (CLP) or intraperitoneal injection of a sublethal dose of endotoxin. TNF mRNA expression was determined by the reverse transcription differential polymerase chain reaction using beta-actin as an internal standard. Serum levels of TNF were threefold higher after endotoxin administration compared to CLP. TNF mRNA in peritoneal macrophages rose fourfold after both endotoxin injection and CLP, with rapid return to normal in endotoxin-treated animals. There was a significant increase in TNF mRNA in the liver and lung, but not the spleen, during the first 24 hr after CLP. An increase in TNF mRNA was seen in all three tissues after injection of endotoxin. These results support the concept of locally produced TNF as a contributing factor in tissue damage and multiple organ failure during sepsis.

Animals↗