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Biomedical subjects

J A Roth

Publications and source records attributed to J A Roth.

At least 235 records · Page 13Linked to original sources
PubMed1994

Effect of manganese on tyrosylprotein sulfotransferase activity in PC12 cells.

Recent studies in our laboratory have revealed that Mn2+ is capable of promoting cell spreading and neurite outgrowth in PC12 cells, a process which is dependent on Mn2+ stimulation of the interaction between extracellular matrix (ECM) components and their corresponding integrin receptors. Since the major ECM proteins implicated in the Mn(2+)-induced morphogenesis, fibronectin and vitronectin, are both tyrosine sulfated, it was of interest to determine whether Mn2+ can regulate the activity of the enzyme responsible for tyrosine sulfation, tyrosylprotein sulfotransferase (TPST). Results of the present studies demonstrated that Mn2+ can suppress TPST activity in PC12 cells in both a time and concentration-dependent manner at concentrations of Mn2+ (0.1 to 1 mM) that promote morphological changes in PC12 cells. Since uptake of Mn2+ may occur via the Ca2+ channel, LaCl3, an inhibitor of Ca2+ transport, was examined and found not to prevent the suppression of TPST activity induced by Mn2+, suggesting that Mn2+ may function at an extracellular site. Suppression of TPST activity occurred with cells plated in serum-free medium on a substrata consisting of either serum or polylysine, suggesting that attachment to extracellular matrix was not an absolute requirement for regulation of activity. Consistent with this is the fact that an RGD-containing pentapeptide did not prevent suppression of TPST activity. Results from the present study demonstrated that Mn2+ is capable of promoting the suppression of TPST activity in PC12 cells at concentrations that have been shown to induce cell spreading and neurite outgrowth. However, unlike the Mn(2+)-induced morphological changes, the presence of ECM proteins is not an absolute requirement for suppression of TPST activity.

2-Chloroadenosine↗
PubMed1994

Retroviral-mediated transduction of p53 gene increases TGF-beta expression in a human glioblastoma cell line.

Transforming growth factor-beta (TGF-beta) has been implicated as a potent growth regulator; the degree of responses to it, whether positive or negative, generally correlates with the stage of cell differentiation in various cell types. We examined the effect of the p53 gene, which participates in the control of cell-cycle progression, on the expression of human TGF-beta. The human glioblastoma cell line SNB-19, which expresses the latent form of TGF-beta, was transfected with a retroviral vector containing wild-type p53 (wt-p53) or p53 with a mutation (mut-p53) at codon 273. Stable G418-resistant SNB-19 clones were isolated. The growth kinetics of wt-p53 transfectants were suppressed compared with those of parental cells, vector transfectants, or mut-p53 transfectants, as assayed by growth-curve measurements and 3H-thymidine incorporation; however, RNA dot blot and Western blot analyses demonstrated that wt-p53 and mut-p53 transfectants expressed higher amounts of TGF-beta 1 and TGF-beta 2 mRNA and intracellular TGF-beta isoform proteins, respectively, than parental cells. By means of the biological assay for active TGF-beta (Mv1Lu cell-growth-inhibition assay), we observed that both transfectants produced active TGF-beta, whereas the parental cells produced only the latent form. These results suggest that, while only the wt-p53 gene inhibits tumor-cell progression, both wt-p53 and codon 273-mutated p53 can cause increased TGF-beta expression.

Base Sequence↗
PubMed1994

Activation of p53 gene expression in premalignant lesions during head and neck tumorigenesis.

With the goal of identifying a potential intermediate biomarker in the multistep process of head and neck cancer development, we conducted immunohistochemical analyses for p53 expression in 33 patients with head and neck squamous cell carcinomas whose tissue sections contained adjacent normal epithelium, hyperplastic, and/or dysplastic lesions. Fifteen of 33 (45%) squamous cell carcinomas of the head and neck expressed p53, but none of four normal control patients (cancer-free nonsmokers) expressed detectable p53 in oral mucosa specimens. To determine when p53 expression is initiated during head and neck tumorigenesis, we examined the normal and premalignant lesions adjacent to the tumors. Five of 24 (21%) samples of normal epithelium adjacent to tumors, 7 of 24 (29%) samples of hyperplasia, and 9 of 20 (45%) samples of dysplasia expressed p53. Quantitative image analysis demonstrated not only a gradual increase in the amount of p53 expression as tissue abnormalities progressed but also a topological change in expression. Whereas p53 expression, when present, was limited to the basal layer in normal epithelium adjacent to tumor, the expression of p53 expanded into the parabasal and superficial layers in hyperplasia and dysplasia. We conclude that p53 expression can be altered in very early phases of head and neck tumorigenesis. Thus, it may be an excellent candidate for risk assessment and may serve as an intermediate biomarker in chemoprevention trials.

Base Sequence↗
PubMed1994

Loss of alpha 1 beta 1 and reduced expression of other beta 1 integrins and CAM in lung adenocarcinoma compared with pneumocytes.

Alterations in expression of various cell-adhesion molecules have been reported in a variety of malignant tissues. However, little is known about how lung adenocarcinomas differ in CAM expression from the normal lung. We analyzed the expression of integrins alpha 1 beta 1 through alpha 6 beta 1, intercellular adhesion molecule (ICAM)-1, neural cell adhesion molecule (NCAM), and lymphocyte function antigen (LFA)-3, CD44, and the two carbohydrate antigens, Lewisx (Le(x)) and sialosyl-Le-Le(x) of lung adenocarcinoma cells, and compared them with autologous pneumocytes. CAM expression was studied by an immunohistochemical method using monoclonal antibodies, and computerized image analysis was used to quantify the immunoperoxidase-staining intensity. The normal lung alveolar cells strongly expressed the integrins alpha 1 beta 1 and alpha 3 beta 1, and fairly expressed alpha 2 beta 1, alpha 4 beta 1, alpha 5 beta 1, and alpha 6 beta 1. ICAM-1, LFA-3, and CD44 were strongly expressed, whereas NCAM, the Le(x) and sialosyl-Le-Le(x) antigens, were expressed weakly. In contrast, we did not detect expression of the alpha 1 beta 1 integrin on any autologous lung adenocarcinoma cells, and they showed on average a 50% reduction in labeling relative intensity units for the integrin common chain marker beta 1, the specific integrins alpha 3 beta 1, alpha 5 beta 1, and alpha 6 beta 1, and ICAM-1, and LFA-3. Examination of the adjacent small blood vessel endothelium in malignant lung tissues did not reveal any major alterations in CAM expression, the small vessel endothelium of the normal and malignant lung tissues appeared with a similar CAM profile. These results suggest that lung adenocarcioma cells have a lack of alpha 1 beta 1 expression and significant reduction in some other integrin beta 1 and CAM expression in comparison with their autologous pneumocytes. This aberration in CAM expression by the lung adenocarcinoma cells may be involved in their loss of proliferation control and may interfere with leukocyte adhesion to tumor cells, enabling the tumor to escape immunodestruction.

Adenocarcinoma↗
PubMed1994

Modulation of oncogene and tumor-suppressor gene expression: a novel strategy for cancer prevention and treatment.

BACKGROUND: Advances in our understanding of the molecular biology of cancer have the potential for translation into clinical cancer prevention and treatment strategies. Oncogenes and tumor suppressor genes have been implicated in the development of human cancers Mutations in gene families occur in both premalignant lesions and invasive tumors. CONCLUSION: Recombinant DNA constructs can be made that eliminate expression of a mutant oncogene protein or provide a normal copy of a tumor suppressor gene to the cancer cell. Reversal of a single genetic lesion is sufficient to inhibit cancer cell proliferation and tumorigenicity. Viral vectors are now being evaluated for direct delivery of these constructs to human tumors.

Genes, Tumor Suppressor↗
PubMed1994

Clinical implications of p53 gene mutation in the progression of Barrett's epithelium to invasive esophageal cancer.

The p53 tumor suppressor gene has been implicated in human esophageal tumorigenesis, and mutations are reported in primary esophageal adenocarcinomas and associated Barrett's epithelium. To evaluate the potential clinical significance of this molecular genetic marker in the progression of Barrett's epithelium to invasive esophageal cancer, we studied 20 patients with Barrett's epithelium, 10 of whom had an associated adenocarcinoma. p53 gene mutations were screened using polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) analysis and p53 oncoprotein distribution by immunohistochemistry. Point mutations were localized to exons 5 and 7 of the p53 gene, previously recognized as "hot spots." p53 gene mutations and immunoreactivity were detected in 7 of 10 patients with primary esophageal adenocarcinomas and in 6 patients with associated Barrett's epithelium, 3 of whom had high-grade dysplasia. Little correlation was observed between p53 positivity and clinicopathologic findings or outcome, although two patients with p53 mutations subsequently developed second primary cancers. Of 10 patients with Barrett's epithelium alone, 6 had p53 mutations, with mild or no dysplasia histologically, suggesting that p53 gene mutation may be an early event in progression to invasive cancer. No patient has developed invasive cancer to date, with a median follow-up of 8 years. These studies further implicate the p53 gene in the Barrett's epithelium-to-carcinoma sequence. Prospective surveillance studies incorporating molecular analysis of the p53 gene are warranted to further evaluate p53 as a predictor of patients at high risk for developing malignancy.

Adenocarcinoma↗
PubMed1994

Resection of lung cancer is justified in high-risk patients selected by exercise oxygen consumption.

The medical criteria for inoperability have been difficult to define in patients with lung cancer. Sixty-six patients with non-small cell lung cancer and radiographically resectable lesions were evaluated prospectively in a clinical trial. The patients were considered by cardiac or pulmonary criteria to be high risk for pulmonary resection. If exercise testing revealed a peak oxygen uptake of 15 mL.kg-1.min-1 or greater, the patient was offered surgical treatment. Of the 20 procedures performed, nine were lobectomies, two were bilobectomies, and nine were wedge or segmental resections. All patients were extubated within 24 hours and discharged within 22 days after operation (median time to discharge, 8 days). There were no deaths, and complications occurred in 8 (40%) of the 20 patients. Five patients whose peak oxygen uptake was lower than 15 mL.kg-1.min-1 also underwent surgical intervention; there was one death. Thirty-four patients whose peak oxygen uptake was less than 15 mL.kg-1.min-1 and 7 who declined operation underwent radiation therapy alone (35 patients) or radiation therapy and chemotherapy (6 patients). There were no treatment-related deaths, and the morbidity rate was 12% (5/41). The median duration of survival was 48 +/- 4.3 months for the patients treated surgically and 17 +/- 2.7 months for those treated medically (p = 0.0014). We conclude that a subgroup of patients who would be considered to have inoperable disease by traditional medical criteria can be selected for operation on the basis of oxygen consumption exercise testing. There is a striking survival benefit to an aggressive surgical approach in these patients.

Adenocarcinoma↗
PubMed1994

Comparison of three techniques of esophagectomy within a residency training program.

Residency training programs commonly emphasize a single technique of esophagectomy, as the safety and the efficacy of teaching or performing more than one type of esophagectomy are unclear. Between 1986 and 1992, 248 patients were explored for possible esophageal resection. Thoracic surgical residents or fellows performed major components of all resections. Two hundred twenty-one patients (adenocarcinoma, 146; squamous cell carcinoma, 72; and other, 3) underwent transthoracic esophagectomy (n = 134), transhiatal esophagectomy (n = 42), or total thoracic esophagectomy (n = 45), a resectability rate of 89.1% (221/248). Complications occurred in 75% of patients with transthoracic esophagectomy, in 69% with transhiatal esophagectomy, and in 80% with total thoracic esophagectomy. The overall operative mortality rate was 6.8% (15/221). Patients with a cervical anastomosis had a higher leak rate (13%) than those with an intrathoracic anastomosis (6%). Median survival was 22 months (19% 5-year survival) and did not differ by operation type or stage. No patient with unresectable disease (n = 27) survived longer than 10 months. Survival for patients with adenocarcinoma stages 3 and 2a suggested a trend toward improved survival after transthoracic esophagectomy despite similar rates of local and distant recurrence. Transthoracic esophagectomy, transhiatal esophagectomy, and total thoracic esophagectomy performed within a residency training program have similar morbidity, mortality, and recurrence rates as those in other modern series. A specific technique of esophagectomy can be selected for individual patients. Survival and sites of recurrence primarily reflect disease stage, not the technique of esophagectomy used.

Adenocarcinoma↗
PubMed1994

ICD implantation via thoracoscopy, "mailslot" thoracotomy, and subxiphoid incision.

An improved method of thoracoscopic implantable cardioverter defibrillators implantation is described. "Mailslot" thoracotomy is more expeditious than thoracoscopic implantation via multiple ports. If required for adequate defibrillation thresholds, subxiphoid, subdiaphragmatic implantation of a defibrillator patch may be performed.

Aged↗
PubMed1994

Gene therapeutics and gene therapy for cancer.

Recent advances in molecular biology have opened new avenues of basic genetic engineering technology and have made possible the application of this technology in clinical human gene therapy. Replication-defective viral vectors and biocompatible materials, eg, liposomes, have been developed as vehicles to introduce potentially therapeutic genes into mammalian cells. Over the past 2 years, this technology has increased the possibilities for therapy in numerous genetic diseases. Approaches at the molecular level have also demonstrated that one of the mechanisms of human cancer development is overexpression of dominant oncogenes, expression of mutant oncogenes, or specific chromosomal deletions or mutations that induce inactivation of tumor-suppressor activity. This concept suggests that the introduction of antisense oncogenes and wild-type tumor-suppressor genes, eg, p53, could halt or reverse these mechanisms, thus having a therapeutic effect in cancer. Moreover, evidence that the immune system is capable of eliminating tumor cells in numerous animal models has suggested gene therapy approaches for the delivery of cytokines, which promote the activation of cytotoxic immune responses against the malignant tissue. The efficacy of these gene therapy protocols is now being evaluated in both animal model systems and clinical trials. This article reviews recent highlights in this rapidly evolving field.

Cytokines↗
PubMed1994

Programmed ventricular stimulation using tandem versus simple sequential protocols.

UNLABELLED: The objective was to determine whether two commonly used ventricular stimulation protocols, one more complex than the other, produced concordant results. If such were the case, the simpler protocol would streamline activities in clinical electrophysiology laboratories. BACKGROUND: Two programmed ventricular stimulation protocols were compared. (1) With the tandem method, the first extrastimulus (S2) is moved stepwise to the effective refractory period and then moved out 50 msec; the second extrastimulus (S3) is then decremented until it fails to capture; S2 and S3 are then decremented in a semialternating (tandem) fashion so that both continue to capture. When S2 reaches the refractory period + 10 msec and S3 fails to capture, S3 is then moved out 50 msec, and S4 is decremented as described for S3. (2) With the simple sequential method, the first extrastimulus (S2) is decremented stepwise to the refractory period, and then moved out 10 msec to assure capture; S3 is then similarly decremented to the refractory period and then moved out 10 msec; and S4 is then similarly decremented. METHODS: This was a prospective, randomized, crossover, consecutive series study. Both protocols were tested in each patient on the same day in randomized order. RESULTS: There were 84 matched studies. Fifty-six patients provided data from baseline electrophysiological studies, and 28 of these provided additional data during drug trials. There was a 93% concordance between the two methods, including the primary outcomes of inducibility of clinical arrhythmias, inducibility of nonclinical arrhythmias, and noninducibility (P < 0.001). Discordances were few and evenly distributed between the two protocols (P = NS). Results were similar for baseline studies and drug trials. The simple sequential method required less time to perform (P < or = 0.01). CONCLUSIONS: Tandem and simple sequential protocols provide concordant results. No advantage could be demonstrated for the more complex tandem method.

Adolescent↗
PubMed1994

Posttranslational regulation of p53 tumor suppressor protein function.

Alteration of the p53 gene by deletion and mutation is the most common denominator yet identified among human cancers (Hollstein et al., 1991; Caron de Fromental and Soussi, 1992). The involvement of the p53 gene in such a broad scope of human cancers warrants further investigation into its mechanism of action in regulating cell growth. The wild-type p53 protein restricts cell growth in the G1 phase of the cell cycle by regulating the transcription of genes and possibly, by influencing DNA replication. Elucidating the cell growth restriction of p53 will require identification and characterization of the genes whose expression is regulated by p53 and the proteins that interact with p53 to regulate its DNA-binding and transactivation functions. A model for the regulation of p53 biochemical function is proposed that extends further and builds on the conformational hypothesis for regulation of p53 function hypothesized by Milner (1991) and Ullrich et al. (1992a). The conformational hypothesis of regulation of p53 function states that the conformation of p53 determines whether it expresses growth-suppressing or growth-promoting biological activity. Mutations observed in human cancer lock p53 in a growth-promoting conformation. We expand the conformational hypothesis in a regulatory model that includes binding proteins, kinases/phosphatases, redox modifier proteins, and homo/hetero-oligomerization, which modulate the tertiary structure of the protein. Different conformational modes of p53 interact differently with initiation complexes at gene promoters and at origins of DNA replication. Each form of p53, depending on its interaction with proteins and gene transcription-initiation complexes, will mediate distinct biological effects on cells ranging from growth suppression to growth promotion. Furthermore, depending on its conformational state, p53 can repress or activate other transcription factors thus indirectly affecting gene regulation. We propose that each cell and tissue type expresses unique quantities and types of p53-binding proteins and modifying enzymes that regulate the interaction of p53 with promoters of genes necessary for control of growth of a specific cell or tissue. It is anticipated that defects in the expression of p53 regulatory proteins are involved in a portion of those tumors expressing normal p53. Defects in the p53 biochemical pathway may thus be even more prevalent in human cancers than is now realized.

Allosteric Regulation↗