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R M Hoffman

Publications and source records attributed to R M Hoffman.

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

Survival efficacy of the combination of the methioninase gene and methioninase in a lung cancer orthotopic model.

We have previously demonstrated the antitumor efficacy of recombinant methioninase (rMETase) derived from Pseudomonas putida. To enhance the efficacy of rMETase, we have constructed the pLGFP-METSN retrovirus encoding the P. putida methioninase (MET) gene fused with the green fluorescent protein (GFP) gene. pLGFP-METSN or control vector pLGFPSN was introduced into the human lung cancer cell line H460. The methionine level of H460-GFP-MET cells was reduced to 33% of that of H460-GFP cells. rMETase (0.08 U/mL) in the medium resulted in 10% survival of H460-GFP-MET cells compared with untreated cells in vitro. In contrast, rMETase-treated H460-GFP cells survived at 90% of control. Tissue fragments harvested from subcutaneous tumors of H460-GFP-MET or H460-MET were implanted by surgical orthotopic implantation into the lungs of nude mice. A suboptimal dose of rMETase was administered intraperitoneally daily to mice in each group. Overall survival of rMETase-treated animals with H460-GFP-MET tumors was significantly longer than either rMETase-treated or -untreated animals with H460-GFP tumors (P < .05 in log-rank test). In two repeat experiments, rMETase-treated animals with H460-GFP-MET tumors had a 30-day survival of 80% and 83%, respectively. Untreated animals with H460-GFP-MET tumors had a 30-day survival of 40% and 58%, respectively. rMETase-treated animals with H460-GFP tumors had a 30-day survival of 0% and 33%, respectively. Untreated animals with H460-GFP tumors had a 30-day survival of 0% and 33%, respectively. The retrovirus-mediated gene transfer of METase decreased the intracellular methionine level of tumor cells and consequently enhanced the efficacy of treatment with the rMETase protein. We have thus demonstrated a new strategy of combination tumor therapy with the gene and gene product of MET.

Animals↗
PubMed2000

In vivo tumor delivery of the green fluorescent protein gene to report future occurrence of metastasis.

The green fluorescent protein (GFP) gene was administered to intraperitoneally (i.p.) growing human stomach cancer in nude mice to visualize future regional and distant metastases. GFP retroviral supernatants were injected i.p. from day 4 to day 10 after i.p. implantation of the cancer cells. Tumor and metastasis fluorescence was visualized every other week with the use of fluorescence optics via a laparotomy on the tumor-bearing animals. At 2 weeks after retroviral GFP delivery, GFP-expressing tumor cells were observed in gonadal fat, greater omentum, and intestine, indicating that these primary i.p. growing tumors were efficiently transduced by the GFP gene and could be visualized by its expression. At the second and third laparotomies, GFP-expressing tumor cells were observed to have spread to lymph nodes in the mesentery and other regional sites. At the fourth laparotomy, widespread tumor growth was visualized by GFP expression, inducing liver metastasis. No normal tissues were found to be transduced by the GFP retrovirus. Thus, reporter gene transduction of the primary tumor enabled detection of its subsequent metastasis. This gene therapy model could be applied to primary tumors before resection or other treatment to have a fluorescent early detection system for metastasis and recurrence.

3T3 Cells↗
PubMed2000

Using the free-to-total prostate-specific antigen ratio to detect prostate cancer in men with nonspecific elevations of prostate-specific antigen levels.

BACKGROUND: Prostate-specific antigen (PSA) levels between 4.0 to 10.0 ng/ml have poor specificity in prostate cancer screening, leading to unnecessary biopsies. OBJECTIVE: To determine whether the free-to-total PSA ratio (F/T PSA) improved the diagnostic accuracy of these nonspecific PSA levels. MEASUREMENTS AND MAIN RESULTS: MEDLINE searchedwas from 1986 to 1997. Additional studies were identified from article bibliographies and by searching urology journals. Two investigators independently identified English-language studies providing F/T PSA ratio test-operating characteristics data on > or = 10 cancer patients with PSA values between 2.0 and 10.0 ng/ml. Twenty-one of 90 retrieved studies met selection criteria. Two investigators independently extracted data on methodology and diagnostic performance. Investigator-selected cut points for the optimal F/T PSA ratio had a median likelihood ratio of 1.76 (interquartile range, 1.40 to 2.11) for a positive test and 0.27 (0.20 to 0.40) for a negative test. Assuming a 25% pretest probability of cancer, the posttest probabilities were 37% following a positive test and 8% following a negative test. The summary receiver operating characteristic curve showed that maintaining test sensitivity above 90% was associated with false positive rates of 60% to 90%. Methodologic problems limited the validity and generalizability of the literature. CONCLUSIONS: A negative test reduced the posttest probability of cancer to approximately 10%. However, patients may find that this probability is not low enough to avoid undergoing prostate biopsy. The optimal F/T PSA ratio cut point and precise estimates for test specificity still need to be determined.

Data Interpretation, Statistical↗
PubMed2000

Crystallization and preliminary crystallographic characterization of recombinant L-methionine-alpha-deamino-gamma-mercaptomethane lyase (methioninase).

L-Methionine-alpha-deamino-gamma-mercaptomethane lyase (rMETase) is involved in the alpha,gamma-elimination of methionine to alpha-ketobutyrate, methanethiol and ammonia. The reaction catalyzed by rMETase reduces the methionine concentration of methionine-dependent tumor cells, arresting their growth. Towards the goal of developing rMETase into an effective antitumor therapeutic and also to understand the catalytic mechanism of this enzyme, rMETase from Pseudomonas putida has been expressed, purified and crystallized. The crystals belong to space group P2(1)2(1)2 and diffract X-rays to at least 2.68 A resolution at 100 K using synchrotron radiation. The unit cell has parameters a = 152.8, b = 154.6, c = 80.8 A and contains four molecules in the asymmetric unit.

Carbon-Sulfur Lyases↗
PubMed2000

How common are various causes of dizziness? A critical review.

BACKGROUND: Although dizziness is a common symptom in both primary care and referral practices, the relative frequency of various causes has not been well delineated. METHODS: A MEDLINE search identified 12 articles containing original data on the etiology of dizziness in consecutive patients. Study sites included primary care offices (n = 2), emergency room (n = 4), and referral clinics (n = 6). Each study's strength of design was graded using nine quality criteria. RESULTS: Dizziness was attributed to a peripheral vestibulopathy in 44% of patients, a central vestibulopathy in 11%, psychiatric causes in 16%, other conditions in 26%, and an unknown cause in 13%. Certain serious causes were relatively uncommon, including cerebrovascular disease (6%), cardiac arrhythmia (1.5%), and brain tumor (<1%). CONCLUSIONS: Dizziness is due to vestibular or psychiatric causes in more than 70% of cases. Since serious treatable causes appear uncommon, diagnostic testing can probably be reserved for a small subset of patients.

Adult↗
PubMed2000

Antimetastatic intraoperative chemotherapy of human colon tumors in the livers of nude mice.

We have developed a new antimetastatic chemotherapeutic strategy for combination with hepatic resection of human colon cancers in a high-metastasis nude mouse model. The new procedure involves i.p. administration of 5-fluorouracil (5-FU) 2 h before hepatic resection of the human colon tumors, with therapy continued postoperatively for 4 consecutive days. We termed this strategy neo-neoadjuvant chemotherapy. The regime significantly prolonged animal survival compared with preoperative 5-FU neoadjuvant therapy, 5-FU postoperative adjuvant therapy, surgery alone, 5-FU without surgery, or the untreated control. The median survival of neo-neoadjuvant i.p. 5-FU-treated group was 81 days, compared with 27 days for the control group (P < 0.009). The median survival of animals in the neoadjuvant group was 37 days (P < 0.021 compared with the control group). There was also a significant difference between the median survival of neo-neoadjuvant, and the neoadjuvant group (P < 0.031). When all animals in the control group had died, 70% of animals with neo-neoadjuvant and 60% of animals with neoadjuvant 5-FU were still alive (P < 0.003 and P < 0.011, respectively). When all animals with neoadjuvant 5-FU treatment had died, 70% of animals with neo-neoadjuvant treatment were still alive (P < 0.003). Survival of all other treatment groups, including 5-FU without surgery, surgery alone, and adjuvant postoperative chemotherapy, was not significantly different from the untreated control group. Two animals in the neo-neoadjuvant group were free of tumors when sacrificed at days 154 and 165 post surgery. Whereas 100% of animals in the control, 90% in the 5-FU alone, 70% in the surgery alone, 60% in the 5-FU adjuvant, and 40% in the neoadjuvant groups had metastases in the lymph nodes draining the liver, only 10% of animals in the neo-neoadjuvant group had metastases. These data suggest that the neo-neoadjuvant therapy increased survival by preventing metastasis of cancer cells not removed in the liver resection procedure. The results of this study indicate that the neo-neoadjuvant treatment strategy for resection of colon cancer liver metastasis should be explored clinically.

Animals↗
PubMed2000

An orthotopic mouse model of remetastasis of human colon cancer liver metastasis.

Whether liver metastases from colon cancer are capable of metastasizing to other sites is an important question in surgical oncology. To answer this question, we have developed a highly metastatic orthotopic transplant model of a liver metastasis from a human colon cancer patient in nude mice that targets the liver and lymph nodes. The metastatic human tumor was transplanted in athymic nude mice by surgical orthotopic implantation (SOI) of a liver metastasis from a colon cancer patient. The human colon tumor was then subsequently implanted in the colon by SOI or, in an additional series of nude mice, in the liver by surgical hepatic implantation (SHI). The mice were then explored over time for lymph node involvement beginning 10 days after implantation. After SOI, 100% of the animals had liver metastasis within 10 days, and subsequently, 19 days after SOI, all lymph nodes draining the liver were involved with metastasis without any retroperitoneal or lung tissue involvement. After SHI, all sites of lymphatic drainage of the liver, including portal, celiac, and mediastinal lymph nodes, were massively involved by metastasis in 100% of the animals as early as 10 days after tumor implantation on the liver. The results of this study demonstrate that liver metastases from colon cancer are capable of remetastasizing to other sites. This study thus suggests that in colon cancer patients with liver metastasis, mediastinal, celiac, and portal lymph node metastases originate from the liver metastasis and not, as previously thought, from primary colon cancer.

Adenocarcinoma↗
PubMed1999

High-malignancy orthotopic nude mouse model of human prostate cancer LNCaP.

BACKGROUND: An animal model of human prostate cancer LNCaP demonstrating high rates of spontaneous metastasis from the orthotopic site after tumor implantation would be very valuable for mechanistic and drug discovery studies. We previously developed microsurgical techniques to implant histologically intact tumor tissues orthotopically in nude mice in order to develop high metastatic mouse models of human cancer. METHODS: Intact tissue of the androgen-dependent human prostate cancer cell line, LNCaP, was implanted on the ventral lateral lobes of the prostate gland by surgical orthotopic implantation (SOI) in a series of 20 nude mice. Mice were autopsied, and histopathological examination of primary tumors and relevant organs was done to identify and quantitate micrometastasis. RESULTS: Eighteen of 20 animals transplanted with LNCaP by SOI had tumor growth. Mean primary tumor weight in the prostate was 9.24 g at time of necropsy. Sixty-one percent of the transplanted animals had lymph node metastasis. Forty-four percent had lung metastasis. Mean survival time was 72 days, indicating a high degree of malignancy of the tumor. CONCLUSIONS: The extensive and widespread lung metastasis as well as lymph node metastasis following orthotopic implantation of LNCaP in nude mice and the short survival time provide a high-malignancy nude model of the LNCaP human prostate tumor.

Animals↗
PubMed1999

A fluorescent orthotopic bone metastasis model of human prostate cancer.

Here, we report a fluorescent spontaneous bone metastatic model of human prostate cancer developed by surgical orthotopic implantation of green fluorescent protein (GFP)-expressing prostate cancer tissue. Human prostate cancer PC-3 cells were transduced with the pLEIN expression retroviral vector containing the enhanced GFP and neomycin resistance genes. Stable GFP high-expression PC-3 clones were selected in vitro with G418, which were then combined and injected s.c. in nude mice. For metastasis studies, fragments of a single highly fluorescent s.c. growing tumor were implanted by surgical orthotopic implantation in the prostate of a series of nude mice. Subsequent micrometastases and metastases were visualized by GFP fluorescence throughout the skeleton, including the skull, rib, pelvis, femur, and tibia The central nervous system, including the brain and spinal cord, was also involved with tumor, as visualized by GFP fluorescence. Systemic organs, including the lung, plural membrane, liver, kidney, and adrenal gland, also had fluorescent metastases. The metastasis pattern in this model reflects the bone and other metastatic sites of human prostate cancer. Thus, this model should be very useful for the study and development of treatment for metastatic androgen-independent prostate cancer.

Animals↗
PubMed1999

Alpha-tocopherol supplementation for men with existing coronary artery disease: a feasibility study.

BACKGROUND: Recent studies have suggested that alpha-tocopherol supplementation can help reduce the incidence of coronary disease. Our objectives were to determine the feasibility of providing alpha-tocopherol supplements to male veterans with existing coronary artery disease and determine its effects on alpha-tocopherol levels and the susceptibility of low-density lipoprotein (LDL) to oxidation. METHODS: Fifty-seven percent of 138 coronary disease patients were willing to participate in a placebo-controlled trial -25% were already taking antioxidants. Thirty-nine men were randomly assigned to either 400 mg/day of alpha-tocopherol (n = 27) or placebo (n = 12). alpha-Tocopherol levels and LDL oxidation (measured by formation of thiobarbituric acid-reactive substance) were measured at baseline and at 6 months. RESULTS: Thirty-three subjects (22 alpha-tocopherol, 11 placebo) completed the study; 3 subjects withdrew after suffering coronary disease events. Supplement compliance exceeded 90% and alpha-tocopherol was well tolerated. The alpha-tocopherol group had a significantly greater mean increase in lipid-adjusted alpha-tocopherol levels (73% vs. -4.6%, P < 0.0001), but oxidized LDL did not change significantly. CONCLUSIONS: A secondary prevention trial among veterans would be feasible because the rates of enrollment, completion, compliance, and clinical events were high. alpha-Tocopherol supplements did not decrease the susceptibility of LDL to oxidation, suggesting that higher dosages or longer duration of supplementation may be required for secondary prevention.

Aged↗
PubMed1999

Evaluating dizziness.

PURPOSE: To conduct a structured literature synthesis on the etiology, prognosis, and diagnostic evaluation of dizziness, and to suggest a primary-care approach to evaluating this symptom. METHODS: Studies were identified from MEDLINE searches (1966 through 1996) and a manual search of bibliographies from retrieved articles. Two investigators independently abstracted study data. RESULTS: The most common etiologies for dizziness were peripheral vestibulopathies (35% to 55% of patients) and psychiatric disorders (10% to 25% of patients). Cerebrovascular disease (5%) and brain tumors (<1%) were infrequent. The history and physical examination led to a diagnosis in about 75% of patients. At least 10% of patients eluded diagnosis. Symptoms were usually self-limited and not associated with an increased risk of mortality. The diagnostic testing literature, which was often methodologically flawed, suggested that routine laboratory tests as well as cardiovascular and neurologic testing had a low yield in unselected patients. We could not derive evidence-based guidelines for using specialized vestibular function tests such as electronystagmography. CONCLUSIONS: Dizziness is usually a benign, self-limited complaint. When a diagnosis can be made, a careful history and physical examination will usually identify the probable cause. Cardiovascular, neurologic, and laboratory testing should be guided by the clinical evaluation. Rigorous studies are needed to determine the accuracy and utility of specialized vestibular testing.

Audiometry↗
PubMed1999

Oxygen-dependent chronic obstructive pulmonary disease does not prohibit aortic aneurysm repair.

BACKGROUND: Severe oxygen-dependent chronic obstructive pulmonary disease (COPD) is considered by many to be a contraindication to open abdominal aortic aneurysm (AAA) repair. We reviewed our own experience with this patient population. METHODS: From July 1995 to March 1999, 14 consecutive patients limited by home oxygen-dependent COPD underwent elective open infrarenal AAA repair. Their medical records were reviewed. RESULTS: The mean aortic aneurysm size was 6.3 cm. The mean PaO2 = 70 mm Hg, PaCO2 = 45 mm Hg, forced expiratory volume in 1 second (FEV1) = 34% of predicted, and forced vital capacity (FVC) = 67% of predicted. All 14 patients were extubated within 24 hours, mean length of hospital stay was 5.9 days, and there were no perioperative deaths. CONCLUSIONS: Severe home oxygen-dependent COPD is not a contraindication to safe elective open AAA repair.

Aged↗
PubMed1999

Orthotopic metastatic mouse models for anticancer drug discovery and evaluation: a bridge to the clinic.

Currently used rodent tumor models, including transgenic tumor models, or subcutaneously-growing human tumors in immunodeficient mice, do not sufficiently represent clinical cancer, especially with regard to metastasis and drug sensitivity. In order to obtain clinically accurate models, we have developed the technique of surgical orthotopic implantation (SOI) to transplant histologically-intact fragments of human cancer, including tumors taken directly from the patient, to the corresponding organ of immunodeficient rodents. It has been demonstrated in 70 publications describing 10 tumor types that SOI allows the growth and metastatic potential of the transplanted tumors to be expressed and reflects clinical cancer. Unique clinically-accurate and relevant SOI models of human cancer for antitumor and antimetastatic drug discovery include: spontaneous SOI bone metastatic models of prostate cancer, breast cancer and lung cancer; spontaneous SOI liver and lymph node ultra-metastatic model of colon cancer, metastatic models of pancreatic, stomach, ovarian, bladder and kidney cancer. Comparison of the SOI models with transgenic mouse models of cancer indicate that the SOI models have more features of clinical metastatic cancer. Cancer cell lines have been stably transfected with the jellyfish Aequorea victoria green fluorescent protein (GFP) in order to track metastases in fresh tissue at ultra-high resolution and externally image metastases in the SOI models. Effective drugs can be discovered and evaluated in the SOI models utilizing human tumor cell lines and patient tumors. These unique SOI models have been used for innovative drug discovery and mechanism studies and serve as a bridge linking pre-clinical and clinical research and drug development.

Animals↗