Biomedical subjects

R M Hoffman

Publications and source records attributed to R M Hoffman.

At least 127 records · Page 7Linked to original sources

PubMed1994

"Patient-like" nude mouse metastatic model of advanced human pleural cancer.

Pleural cancer in humans is a frequently occurring tumor. Recently, clinical trials have suggested that chemotherapy and immunotherapy administered intrapleurally may elicit responses in early-stage diseases. However, at radiological and pleural endoscopic evaluation, most of the patients are found to have a visceral pleural involvement that is generally refractory to therapy and leads to a poor prognosis. The goal of this study was to construct a nude mouse model of human parietal- and visceral-pleural cancer that could reflect the clinical picture for this disease. The model could then be useful for drug discovery for pleural cancer. A well-differentiated human lung adenocarcinoma was used as intact tissue for implantation. Ten mice underwent parietal-pleural implantation and ten mice visceral-pleural implantation via a novel thoracotomy procedure we have developed. Symptoms of tumor growth were determined from weight loss, respiratory distress, or debilitation. Actual tumor growth and spread were measured at autopsy. The mouse survival curves of each group were estimated by the Kaplan-Meier method and the difference of the median survival times was assessed by the Log-rank test. The slopes of mean-mouse weight curves were compared using a standard two-sample t-test. A 100% take rate was achieved in constructing the pleural cancer models. Tumor growth was initially assessed by symptomatology and survival: the median survival time was, respectively, 27.9 days and 31 days for visceral-pleural and parietal-pleural implanted groups (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMed1994

In vivo and in vitro effects of androgen on fibroblast growth factor-2 concentrations in the human prostate.

Prostatic growth is primarily regulated by dihydrotestosterone (DHT). Recent studies have demonstrated that a large number of growth factors are present in the human benign prostatic hyperplasia (BPH) prostate, including epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), transforming growth factor beta (TGF-beta), insulin-like growth factor (IGF), and basic fibroblast growth factor (bFGF) (FGF-2). DHT may mediate its mitogenic effects in the prostate by regulating growth factors. To test this hypothesis, we have utilized a histoculture androgen sensitivity assay (HASA) in which 3H-thymidine incorporation is measured in aliquots of BPH tissue in histoculture with either added DHT or hydroxyflutamide (HF). The resulting DHT/HF ratio is an expression of the androgen sensitivity of the tissue. In this study, we have compared the DHT/HF ratio for 3H-thymidine incorporation to the DHT/HF ratio for FGF-2 measured in the histocultured prostates. The DHT/HF ratio for the HASA studies of 3H-thymidine incorporation averaged 2.68 compared to the DHT/HF ratio for FGF-2 in the same specimens of 1.01. These values were significantly different, therefore indicating no relationship between DHT stimulation and FGF-2 levels. In addition, FGF-2 levels were measured in human BPH prostates from patients medically castrated with megesterol acetate and estradiol 17-beta prior to surgery. These values were not significantly different, and therefore do not suggest any effect of DHT on the concentration of prostatic FGF-2. Although these studies did not show any effect of DHT on the regulation of prostatic FGF-2, they do indicate that the HASA assay is feasible and appropriate to use in the study of relationships between DHT and various growth factors.

Androgen Antagonists↗

PubMed1994

The three-dimensional question: can clinically relevant tumor drug resistance be measured in vitro?

In vivo-like drug responses are observed in three-dimensional culture but frequently not in two-dimensional culture, indicating that drug response may be a function of tissue architecture. Alexis Carrel introduced that in vitro culture of tissues in the beginning of the century utilizing a culture system that allowed the three-dimensional growth of tissues. Leighton improved upon this system by developing a substrate of sponge matrices. Other methods of three-dimensional culture include collagen gels and what are known as organ culture systems on filters or meshes. In addition, cell suspensions can be converted into multicellular spheroids, another form of three-dimensional culture. Comparison of the three-dimensional culture methods with two-dimensional culture methods has shown critical differences in drug response. The in vivo mechanism of drug resistance may involve alterations in cell-cell interaction which may occur in three-dimensional culture as opposed to monolayer culture.

Animals↗

PubMed1994

Correlation of proteolytic activities of organ cultured intact mouse skin with defined hair cycle stages.

The cyclic growth activity of the hair follicle is characterized by substantial remodelling of the extracellular matrix, yet, little is known about the proteolytic activities regulating this process. In murine skin, hair cycling is highly synchronized and is associated with dramatic remodeling of all skin compartments. We therefore have assessed, in this pilot study, proteolytic activities of murine skin from various stages of the depilation-induced hair cycle. We show that the defined proteolytic activities displayed by organ cultured intact mouse skin differ between hair cycle stages. Skin with all follicles in telogen or mid anagen displayed only minimal lysis of collagen type I gels, while early anagen skin had significant collagenase activity. Skin cultured on gelatin gels at the air-liquid interphase ('histoculture') completely lysed the gel within 5 days when all follicles were in early anagen, while this was not observed with mid and very late-anagen skin. Zymography of conditioned medium from these cultures revealed the secretion of activated interstitial collagenase and of gelatinases of 72 and 92 kDa, with the maximum of interstitial collagenase activity secreted by anagen IV skin. Addition of TPA or TNF-alpha to the culture medium stimulated secreted collagenase type I activity. The C 57 BL-6 mouse offers an attractive model for dissecting and manipulating hair cycle-associated proteolysis in a physiologically relevant system.

Animals↗

PubMed1993

Therapeutic tumor-specific cell cycle block induced by methionine starvation in vivo.

The ability to induce a specific cell cycle block selectively in the tumor could have many uses in chemotherapy. In the present study we have achieved this goal of inducing a tumor-specific cell cycle block in vivo by depriving Yoshida sarcoma-bearing nude mice of dietary methionine. Further, we demonstrate that methionine depletion also causes the tumor to eventually regress. The antitumor effect of methionine depletion resulted in the extended survival of the tumor-bearing mice. The mice on the methionine-deprived diets maintained their body weight for the time period studied, indicating that tumor regression was not a function of body weight loss. The data reported here support future experiments utilizing methionine depletion as a target for tumor-selective cell cycle-dependent therapy.

Animals↗

PubMed1993

A novel "patient-like" treatment model of human pancreatic cancer constructed using orthotopic transplantation of histologically intact human tumor tissue in nude mice.

Pancreatic cancer is a disease with essentially no effective treatment. To increase the potential for discovering effective treatment, we have developed a new treatment model whereby a human pancreatic cancer line, PANC-4, was orthotopically transplanted to the pancreas of nude mice as histologically intact tumor tissue. The tumor grew with subsequent invasive local tumor growth and liver and peritoneal metastases. The antitumor activity of 5-fluorouracil (5-FU) and mitomycin C (MMC) against PANC-4 was initially determined in the in vitro collagen-sponge-gel supported histoculture drug-response assay with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide end point. Inhibition rates were 5.6% for 5-FU and 39.4% for MMC indicating higher efficacy of MMC than 5-FU against PANC-4. When the antitumor activities of 5-FU and MMC against PANC-4 were determined in vivo using the nude mouse orthotopic transplant treatment model, slight local tumor growth inhibition with equivalent incidence of metastases to the liver and the peritoneum as the control were observed in the mice treated with 5-FU, while those treated with MMC had considerably reduced local tumor growth without liver and peritoneal metastases. Thus the histoculture drug-response assay in combination with the orthotopic transplant metastatic models provides for the first time a paradigm for evaluation of agents which may be effective against not only locally growing human pancreatic cancer but resulting metastases as well.

Animals↗

PubMed1993

Expression of the biochemical defect of methionine dependence in fresh patient tumors in primary histoculture.

Methionine dependence is a metabolic defect that occurs in many human tumor cell lines but not normal in unestablished cell strains. Methionine-dependent tumor cell lines are unable to proliferate and arrest in the late S/G2 phase of the cell cycle when methionine is replaced by its immediate precursor homocysteine in the culture medium (MET-HCY+ medium). However, it is not known whether methionine dependence occurs in fresh patient tumors as it does in cell lines. In order to determine whether methionine dependence occurs in fresh patient tumors as well as whether methionine dependence occurs in fresh patient tumors as well as in cell lines we took advantage of the technique of sponge-gel-supported histoculture to grow tumors directly from surgery. We then measured nuclear DNA content by image analysis to determine the cell cycle position in MET-HCY+ compared to MET+HCY- medium in 21 human patient tumors. Human tumor cell lines found to be methionine dependent by cell count were used as positive controls and were found to have marked reduction of cells in G1 compared to total cells in the cell cycle in MET-HCY+ medium with respect to the G1: total cell ratio in MET+HCY- medium. Therefore late cell cycle arrest was used as a marker of methionine dependence for histocultured patient tumors. We found that 5 human tumors of 21, including tumors of the colon, breast, ovary, prostate, and a melanoma, were methionine dependent based on cell cycle analysis. These data on fresh human tumors indicate that methionine dependence may frequently occur in the cancer patient population. Implications for potential therapy based on methionine dependence are discussed.

Cell Count↗

PubMed1993

Differential chemosensitivity of local and metastatic human gastric cancer after orthotopic transplantation of histologically intact tumor tissue in nude mice.

We have established a metastatic model of human gastric cancer using orthotopic transplantation of histologically intact tissue in nude mice, and have used this model to evaluate the effects of immunochemotherapy using OK-432, 5-fluorouracil (5-FU) and mitomycin C (MMC) against SC-I-NU, a human stomach cancer line. One-quarter or one-half maximum tolerated doses (MTDs) of 5-FU or MMC resulted in a significant reduction of stomach tumor growth, while liver metastases were not reduced, possibly due to suppression of natural killer (NK)-cell activity by both drugs. On the other hand, when combined with OK-432, half MTDs of 5-FU and MMC significantly reduced liver metastases, with synergistic reduction of stomach tumor growth, possibly reflecting a rescue of NK-cell activity by treatment with OK-432. This metastatic model of human stomach cancer shows that locally growing and metastatic tumors may have different chemosensitivities, and provides the opportunity to test both with various treatment regimens.

Adenocarcinoma↗

PubMed1993

Nude mouse metastatic models of human stomach cancer constructed using orthotopic implantation of histologically intact tissue.

Nude mice have been used to develop s.c. growing human stomach tumors, but these rarely metastasize. Recently, I. J. Fidler and others have developed orthotopic implantation metastatic models using cell suspensions which are inoculated into the corresponding organ of nude mice from which the tumor cells were originally derived in the human. However, recent work has indicated that disaggregated cell suspensions may not always express their full metastatic potential. In this light, we have recently developed an orthotopic implant model utilizing intact tissue such as that obtained directly from surgery. This approach has yielded high take rates and frequent metastases in colon cancer, bladder cancer, lung cancer, pancreatic cancer, and prostate cancer. We report here the application of this intact tissue orthotopic implant technique to stomach cancer resulting in the formation of metastases in 100% of the mice with extensive primary growth to the regional lymph nodes, liver, and lung. In contrast, when cell suspensions were used to inject stomach cancer cells at the same site, metastases occurred in only 6.7% of the mice with local tumor formation, emphasizing the importance of using intact tissue to allow full expression of metastatic potential. Injuring the serosa similar to that occurring in intact tissue transplantation did not increase the metastatic rate after orthotopic injection of cell suspensions of stomach tumor cells. This intact tissue orthotopic implantation model should allow development of new treatment modalities and further study of the biology of human stomach cancer.

Animals↗

PubMed1993

Orthotopic transplantation of histologically intact clinical specimens of stomach cancer to nude mice: correlation of metastatic sites in mouse and individual patient donors.

Fresh surgical specimens derived from 36 patients with advanced stomach cancer were orthotopically transplanted in nude mice using histologically intact tissue. Twenty of 36 patient tumors gave rise to locally growing tumors in the mice. All 20 patients whose stomach tumors resulted in local growth in the nude mice had clinical lymph-node involvement, whereas 8 of the other 16 patients whose tumors were rejected had lymph-node involvement. There was a statistical correlation (p < 0.01) between local tumor growth in nude mice and clinical lymph-node involvement. Of the 20 cases resulting in local growth in the nude mice, 5 had clinical liver metastases and all 5 cases resulted in liver metastases in the nude mice. Of the 20 cases, 6 had clinical peritoneal involvement of their tumor, and of these 5 resulted in peritoneal metastasis in the nude mice. There were statistical correlations (p < 0.01) for both liver metastases and peritoneal involvement between patients and mice. These results indicate that, after orthotopic transplantation of histologically intact stomach cancers from patients to nude mice, the subsequent metastatic behavior of the tumors in the mice closely correlated with the course of the tumors in the patients.

Animals↗

PubMed1993

To do tissue culture in two or three dimensions? That is the question.

Alexis Carrel introduced the in vitro culture of tissues in the beginning of the century utilizing a culture system that allowed the three-dimensional growth of tissues. Leighton improved upon this system by developing a substrate of sponge matrices. Other methods of three-dimensional culture include collagen gels and what are known as organ culture systems on filters or meshes. In addition, cell suspensions can be converted into multicellular spheroids, another form of three-dimensional culture. Comparison of the three-dimensional culture methods with two-dimensional culture methods has shown critical differences in the behavior of biological systems in culture. For example, in vivo-like drug responses are observed in three-dimensional but frequently not in two-dimensional cultures, indicating that drug response may be a function of tissue architecture. The in vivo mechanism of drug resistance may involve alterations in cell-cell interaction which may occur in three-dimensional culture as opposed to monolayer culture. Practical applications of three-dimensional culture include the development of a drug-response assay that correlates not only with drug resistance but also with drug sensitivity and survival of cancer patients. It has been shown that gene expression may be more in vivo-like in three-dimensional cultures than in two-dimensional monolayer cultures. For example, tumor antigens may be expressed in three-dimensional culture and not in monolayer culture. Thus, future studies utilizing three-dimensional cultures may significantly enhance our understanding of gene expression and resistance to drugs and enhance the efficacy of cancer chemotherapy by correctly predicting active drug regimens for individual patients.

Animals↗

PubMed1993

The preparation of endotoxin-free L-methionine-alpha-deamino-gamma-mercaptomethane-lyase (L-methioninase) from Pseudomonas putida.

Many types of human and animal tumors have an absolute requirement for methionine. This requirement can be satisfied by homocysteine only in normal cells and tissues. Therefore, methionine may be an important target in cancer therapy. To attack this target we have purified endotoxin-free methioninase from Pseudomonas putida by a novel and simple procedure. This procedure involves (1) a heat step of the cell extract at 60 degrees C for 8 min, (2) DEAE-Toyopearl ion-exchange chromatography, (3) DEAE-Sephadex A50 ion-exchange gel filtration chromatography, and (4) affinity chromatography on Acticlean to remove the endotoxin bound to the enzyme. The yield for this purification was up to 80%. The methioninase has four subunits of approximate molecular weight 43 kDa. This is the first methodology for methioninase that allows rapid purification with high yield and separation from endotoxin suitable for in vivo efficacy testing against methionine-dependent tumors in animal models.

Carbon-Sulfur Lyases↗

PubMed1993

Surgery for herniated lumbar discs: a literature synthesis.

OBJECTIVE: To assess the risks and benefits of surgery for herniated lumbar discs (discectomy) and to evaluate the methodologic quality of the literature. DESIGN: Literature synthesis. STUDY SELECTION AND DATA ANALYSIS: A structured MEDLINE search identified studies of standard, microsurgical, or percutaneous discectomy. Eligible studies had adult subjects, sample sizes of > or = 30, clinical outcome data for > or = 75% of patients, and follow-up of > or = 1 year. Summary rates of successful outcomes, reoperations, and complications were obtained by a random-effects logistic regression model. Methodologic quality was assessed using established study design criteria. RESULTS: Eighty-one studies met inclusion criteria. Most had substantial design flaws and/or omitted important clinical data. Randomized trials of standard discectomy showed better short-term sciatica relief following surgery; 65% to 85% of patients reported no sciatica one year after surgery, compared with only 36% of conservatively treated patients. No data from randomized trials were available for microdiscectomy or percutaneous discectomy, although most outcomes appeared comparable to those of standard discectomy. Approximately 10% of discectomy patients underwent further back surgery, and rates increased over time. The rate of serious complications, including death and permanent neurologic damage, was less than 1%. CONCLUSIONS: Most studies were poorly designed and reported. Standard discectomy appears to offer better short-term outcomes than does conservative treatment, but long-term outcomes are similar. Discectomies are relatively safe procedures, though reoperations are common and increase over time. Decisions for elective surgery must balance faster pain relief against the risks and costs of surgery.

Diskectomy↗

PubMed1993