Biomedical subjects

H C Pitot

Publications and source records attributed to H C Pitot.

At least 73 records · Page 4Linked to original sources

PubMed1997

Regression of metastatic carcinoid tumor after valvular surgery for carcinoid heart disease.

BACKGROUND: The carcinoid syndrome is a common sequela in patients with carcinoid tumor metastatic to the liver. Cardiac involvement occurs in 19-56% of patients with symptomatic carcinoid syndrome and, in some patients, leads to valvular surgery to relieve symptoms due to progressive right-sided heart failure. Reports of these patients have emphasized amelioration of cardiac symptoms, but postoperative tumor status rarely has been discussed. METHODS: This report describes four patients who underwent valvular heart surgery for severe carcinoid heart disease and had regression of their metastatic carcinoid tumor postoperatively. RESULTS: All four patients had definite clinical improvement in cardiac function and relief of symptoms related to congestive heart failure postoperatively. Unexpectedly, they also had regression of their metastatic disease, as reflected in decreased levels of urinary 5-hydroxyindoleacetic acid, and objective evidence of a reduction in the size of hepatic metastases. CONCLUSIONS: To the authors' knowledge, these four patients represent the first reported cases of metastatic disease regression after valvular surgery for carcinoid heart disease. Further descriptions of tumor status in patients having undergone a heart operation for this disease would be valuable in determining the clinical significance of this finding.

Adult↗

PubMed1997

Cell lines with heterogeneous phenotypes result from a single isolation of albumin-sv40 T-antigen transgenic rat hepatocytes.

Several immortalized cell lines were established from the livers of two transgenic rats expressing the simian virus protein large T antigen under the control of the albumin promoter. Hepatocytes from transgenic rats were isolated by a two-step perfusion procedure from a normal-appearing liver and from a liver that contained a single neoplasm. Cells were also isolated from the dissociated liver neoplasm. After 5 weeks in culture, cell colonies were isolated and subcloned as individual cell lines. Electron microscopy revealed that all cell lines had a high nuclear-to-cytoplasmic ratio compared with normal hepatocytes. The cytoplasm contained numerous organelles, including smooth and rough endoplasmic reticulum, Golgi, mitochondria, peroxisomes, and annulate lamellae. However, the lines exhibited a variety of different cell morphologies. All cell lines, including those derived from neoplastic cells, exhibited a similar doubling time of 26 hours and the ability to grow in soft agar. Northern blot analysis revealed that the cell lines differentially expressed hepatocyte markers. Large T antigen was expressed in the cultured cell lines at much higher levels than was observed in transgenic hepatocytes in vivo. This suggests that the viral protein is required to maintain cell viability in culture. In addition, the tumor suppressor proteins, p53 and Rbp105, were detected in all cultured cell lines. In contrast, these same proteins were not detected by Western blot in transgenic hepatocytes in vivo. All cell lines expressed the oncogene c-myc, yet growth factor-dependent and independent growth were observed. The data presented show for the first time the establishment and characterization of a number of cell lines derived from hepatocytes isolated from an alb-SV40 large T-antigen transgenic rat. These cell lines exhibited varied morphological and biochemical hepatocellular characteristics in vitro, suggesting that the expression of the transgene in hepatocytes leads to considerable phenotypic diversity analogous to that seen in hepatocellular carcinomas induced by chemical carcinogenesis.

Animals↗

PubMed1997

Phase I study of immunotherapy of hepatic metastases of colorectal carcinoma by direct gene transfer of an allogeneic histocompatibility antigen, HLA-B7.

We have completed a phase I study to test feasibility and toxicity of immunotherapy of hepatic metastases from colorectal carcinoma by direct gene transfer of HLA-B7, a MHC class I gene. Eligible patients were HLA-B7 negative, immunocompetent by PHA lymphocyte stimulation and had at least two measurable hepatic lesions on CT scan for measurement of response of the injected lesion, as well as evaluation of possible distant response. Under ultrasonographic guidance the hepatic lesions were injected with Allovectin-7, a liposomal vector containing the combination of the HLA-B7 gene with beta 2-microglobulin formulated with the lipid DMRIE-DOPE. Eligible patients were injected on two schedules. On the first schedule patients received an injection on day 1 and the injected lesion was biopsied to determine transfection every 2 weeks for 8 weeks. Doses were escalated from 10 micrograms to 50 micrograms to 250 micrograms with three patients treated at each level. The second schedule included multiple injections of 10 micrograms. Three patients received injections on days 1 and 15. Three patients received injections on days 1, 15 and 29. A total of 15 patients have completed treatment. The plasmid DNA was detected in 14 of 15 patients (93%) by PCR. In five of 15 patients (33%) mRNA was also detected. The HLA-B7 protein was detected in five of eight patients (63%) by immunohistochemistry and in seven of 14 patients (50%) tested by fluorescence activated cell sorting (FACS) analysis. There has been no serious toxicity directly attributable to allovectin-7. Our results suggest that liposomal gene transfer by direct injection is feasible and non-toxic. Further studies will be necessary in order to establish the therapeutic efficacy.

Adult↗

PubMed1997

Quantitative stereological studies of a 'selection' protocol of hepatocarcinogenesis following initiation in neonatal male and female rats.

A modified initiation-selection procedure for neonatal male and female rat hepatocarcinogenesis were examined utilizing the methods of quantitative stereology. In this study, diethylnitrosamine (10 mg DEN/kg) was given a few days after birth. At weaning, the rats were fed 0.02% 2-acetylaminofluorene (AAF) for 2 weeks with a mitotic stimulus [70% partial hepatectomy (PH)] after 1 week on the diet. Quantitative stereological analyses in conjunction with the use of several enzyme markers were used to determine the number and volume of altered hepatic foci (AHF) detected at 1 week, 3 months and 7 months after the selection procedure. This format resulted in an equivalent number of AHF in male and female rats. The AHF were three times larger in males than in females 1 week after discontinuation of AAF administration. Three months after the selection procedure, the number of AHF had decreased by at least a third and their volume percentage was the same in male and female rats. After 7 months, the number and volume fraction of detectable AHF in females were comparable to those which had been observed at 1 week after selection. In the male, the number but not the volume fraction were similar at 7 months compared with 1 week after selection. Both initiation with DEN and selection with AAF/PH contribute independently to the total population of AHF in male and female rats. At least half of the AHF detected 7 months after the selection protocol were due to DEN administration alone. Rats receiving only the AAF/PH selection exhibited one third of the number of AHF observed with the complete protocol. Administration of a non-necrogenic dose of DEN to neonatal rats when coupled with the AAF/PH selection procedure resulted in a significant promotion of the growth of initiated hepatocytes at 1 week, 3 months or 7 months after the selection procedure. These studies demonstrated that (i) the number of AHF detected after a non-necrogenic dose of DEN during the first week of life with subsequent AAF/PH selection after weaning decreases within the first 3 months after the selection procedure, but can re-develop with a promotion stimulus; (ii) the AAF/PH selection procedure itself may initiate hepatocytes in the absence of DEN administration; (iii) the AAF/PH selection procedure is equally effective with respect to the number of AHF observed after phenobarbital promotion in weaning male and female rats initiated near birth.

2-Acetylaminofluorene↗

PubMed1997

The effect of two periods of short-term fasting during the promotion stage of hepatocarcinogenesis in rats: the role of apoptosis and cell proliferation.

The loss of body and liver weight caused by chronic caloric restriction and its effects on carcinogenesis are well known; however, the effects of acute fasting on carcinogenesis have not been intensively investigated. We have studied some parameters of rat liver during short-term fasting and its effect on the stage of promotion in hepatocarcinogenesis in rats. During two fasting periods, body and liver weight decreased remarkably. Bromodeoxyuridine (BrdU) labeling indices (LI) decreased, and cell density increased prominently in liver sections. Hematoxylin and eosin-stained and nick end labeling (TUNEL)-stained sections showed an increase of apoptotic bodies in the absence of necrosis during the fasting period. Moreover, gel electrophoresis of DNA isolated from whole liver revealed ladder formation indicative of nucleosomal DNA cleavage. At the beginning of the fasting period livers exhibited a small but definite number of altered hepatic foci (AHF) expressing glutathione S-transferase, placental form (GST-P), but at the end of the fasting period no AHF were discernible in all livers of animals subjected to the fasting period. After refeeding, cell density and the incidence of apoptotic bodies decreased prior to a transient increase of BrdU LI. The percentage volume of liver occupied by AHF of fasted rats was significantly greater than that of control rats at 140 days after initiation. These results suggest that both the liver weight loss and the complete loss of discernible AHF from short-term fasting was caused by (i) decrease of cell volume, (ii) cell loss by apoptosis, and (iii) a decrease of hepatocyte proliferation. Furthermore, this relatively transient liver weight loss enhanced the promotion of hepatocarcinogenesis, possibly by enhanced cell proliferation compensatory to the fasting cycles.

Animals↗

PubMed1997

Phase II trial of irinotecan in patients with metastatic colorectal carcinoma.

PURPOSE: To evaluate the objective tumor response rate and toxicities of patients with metastatic colorectal carcinoma treated with irinotecan hydrochloride (CPT-11). PATIENTS AND METHODS: A total of 121 patients with advanced colorectal carcinoma--90 with prior fluorouracil (5-FU) exposure and 31 chemotherapeutically naive patients--were enrolled between May 1993 and June 1994. Patients were treated with CPT-11 at 125 mg/m2 intravenously weekly for 4 weeks followed by a 2-week rest. RESULTS: Among 90 patients with prior 5-FU chemotherapy, 12 partial responses were observed (response rate, 13.3%; 95% confidence interval [CI], 7.1% to 22.1%). Among 31 chemotherapy-naive patients, eight had partial responses (response rate, 25.8%; 95% CI, 11.9% to 44.6%). The median response duration as measured from time of initial treatment for the two groups was 7.7 months and 7.6 months, respectively. The major adverse reactions were gastrointestinal and hematologic. The incidence of grade 3 or 4 diarrhea was 36.4%, while the overall incidence of grade 3 or 4 leukopenia was 21.5% of patients. Only four of 121 patients (3.3%) developed neutropenic fever (grade 4 neutropenia with > or = grade 2 fever). The incidence of grade 4 leukopenia was higher in patients with prior pelvic radiotherapy (chi2 test P = .04), while the incidence of grade 3 or 4 diarrhea demonstrated no association with previous pelvic irradiation. CONCLUSION: According to the study design, CPT-11 showed promising activity in chemotherapy-naive patients with advanced colorectal carcinoma and modest activity in patients with prior 5-FU exposure. The toxicity with this schedule appears manageable with appropriate dose modification for individual patient tolerance and an intensive loperamide regimen for the management of diarrhea. Care should be taken when treating patients with prior pelvic radiotherapy because of the increased risk of neutropenia.

Adenocarcinoma↗

PubMed1997

Octreotide inhibition of flushing and colonic motor dysfunction in carcinoid syndrome.

OBJECTIVES: Previous studies showed increased plasma motilin and substance P concentrations and accelerated motor function in the small bowel and colon in patients with carcinoid diarrhea. Octreotide is beneficial in patients with carcinoid syndrome. Our hypothesis was that octreotide inhibits accelerated motility and gut neuropeptides in carcinoid syndrome. METHODS: In 12 patients with metastatic carcinoid syndrome, we investigated the effect of octreotide 50 microg s.c. t.i.d (n = 6) or placebo (n = 6) on postprandial symptoms, GI transit, colonic motility, and circulating levels of selected circulating peptides and amines. RESULTS: Octreotide reduced postprandial flushing (p = 0.03) but not pain. Octreotide significantly retarded overall colonic transit and proximal colonic emptying (p < 0.05); it tended to prolong small bowel transit time (p = 0.13) and to reduce postprandial colonic tone (p = 0.08) compared with placebo. Octreotide also reduced circulating levels of peptide YY, neurotensin, vasoactive intestinal polypeptide, and substance P but had no effect on plasma motilin, neuropeptide Y, calcitonin gene-related peptide, or histamine after meal ingestion. CONCLUSION: Octreotide ameliorates gut motor dysfunctions that characterize carcinoid diarrhea; the potential role of specific antagonism of serotonin, substance P, and vasoactive intestinal polypeptide alone or in combination with agents that inhibit their release in carcinoid diarrhea deserves further study.

Aged↗

PubMed1997

Phase I trial of temozolomide (NSC 362856) in patients with advanced cancer.

Temozolomide (TMZ) is a new imidazotetrazine derivative with early clinical activity in glioma and melanoma. The purpose of this Phase I study is to characterize the toxicity, pharmacokinetics, and antitumor activity of TMZ administered on an oral 5-day schedule to patients with or without prior exposure to nitrosourea (NU). Thirty-six eligible patients received a total of 77 cycles of therapy with TMZ administered p.o. at doses ranging from 50 mg/m2/day to 250 mg/m2/day for 5 days, every 4 weeks. Separate dose escalations were carried out in patients, with or without prior exposure to NU. Pharmacokinetic studies were performed during the first cycle of treatment on days 1 and 5. Dose-limiting toxicity was thrombocytopenia, and the maximally tolerated doses for patients with and without prior exposure to NU were 150 mg/m2/day for 5 days (total dose, 750 mg/m2) and 250 mg/m2/day for 5 days (total dose, 1250 mg/m2), respectively. Significant (grade 3 or higher) thrombocytopenia was observed in six patients during cycle 1. The median times to nadir and recovery were 17 and 15 days, respectively. Nonhematological toxicity was generally manageable and consisted of fatigue, nausea, and vomiting. There were two complete responses (one glioma and one melanoma) in patients without prior NU. No objective responses were seen in patients with prior NU treatment. Pharmacokinetic studies showed rapid absorption with a mean time to peak concentration of 60 min and mean t1/2 of 109 min (range, 80-121 min). The area under the curve and the peak plasma concentrations were linear over the dose range of 50-250 mg/m2/day. The mean apparent oral clearances on day 1 for patients with and without prior NU exposure were 102+/- 27 and 115+/- 22 ml/min/m2, respectively. Apparent oral clearances on days 1 and 5 were found to differ with respect to NU exposure (P = 0.047). Renal clearance of the parent drug and its metabolism to 3-methyl-2, 3-dihydro-4-oxoimidazo[5,1-d]tetrazine-8-carboxylic acid were minor pathways of TMZ elimination. We conclude that TMZ is well tolerated in this oral 5-day schedule with dose-limiting thrombocytopenia and that it has promising activity in glioma and melanoma. The recommended doses for Phase II studies in patients with and without prior NU are 125 mg/m2/day for 5 days and 225 mg/m2/day for 5 days, respectively.

Administration, Oral↗

PubMed1996

Characterization of the rat Class 3 aldehyde dehydrogenase gene promoter.

The Class 3 aldehyde dehydrogenase gene (ALDH-3) is differentially expressed. Expression is either constitutive or xenobiotic inducible via an aromatic hydrocarbon (Ah) receptor-mediated pathway, depending upon the tissue. A series of studies were performed to examine the regulation of rat ALDH-3 basal expression. DNase I footprint analysis identified four DNA regions within the proximal 1 kb of the 5' flanking region of rat ALDH-3 which interact with regulatory proteins. Reporter gene and gel mobility shift assays indicate that Sp1-like proteins interact with two proximal DNase I footprinted sites to confer strong promoter activity. Two distal DNase I footprinted sites are found within a region that inhibits rat ALDH-3 promoter activity. This negative region is bound by NF1-like proteins and/or unique proteins. This 1 kb 5' flanking region of rat ALDH-3 may act constitutively in many cell types. In contrast with other Ah receptor regulated genes, no DNA elements or transcription factors acting within this region appear to be involved in regulating xenobiotic-inducible expression of rat ALDH-3.

Aldehyde Dehydrogenase↗

PubMed1996

Phase II enzyme expression in rat liver in response to the antiestrogen tamoxifen.

The genotoxicity and carcinogenicity of tamoxifen have been attributed to metabolic activation of tamoxifen to an electrophile. Phase II enzymes are known to be involved in the metabolism of the drug and possibly in the formation or elimination of the active metabolite. To determine the effects of tamoxifen on phase II enzyme expression, the drug was administered to F344 rats, and hepatic glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), and sulfotransferase (ST) expression was evaluated. Some of the tamoxifen-induced effects, including dramatic suppression of selected GST enzymes and activity, were observed at a dose in rats that is directly equivalent, on a mg/kg b.w. basis, to the doses used for breast cancer treatment. Most of the observed responses are not consistent with the previously described phenobarbital-like properties of tamoxifen and could be the result of the partial agonist activity of tamoxifen at the estrogen receptor. Northern blot analysis was performed with isozyme-specific oligonucleotide probes for rat GST, ST, and UGT. In addition, GST subunit protein levels were assayed by high-performance liquid chromatography. In females, tamoxifen treatment resulted in a 60% suppression of GST Ya1 mRNA and protein levels and a 40% suppression of GST Ya2 levels. In males, tamoxifen treatment suppressed GST Ya1 expression approximately 60%, and GST Ya2 expression was suppressed at low doses but induced above control at high doses. Male GST Yc1 was induced approximately 80% over control. The expression of all other major forms of rat hepatic GST subunit protein, including GST Yb1, Yb2, Yb3, Yp, and Yl, was unaffected by tamoxifen treatment. GST conjugation activity toward delta 5-androstene-3,17-dione, a GST Ya1- and Ya2-specific substrate, was suppressed approximately 40% in both sexes, consistent with our protein and mRNA data. Total GST activity, as measured by the rate of chlorodinitrobenzene conjugation, was not changed. Tamoxifen also produced a dose-dependent increase in UGT2B1 mRNA, a phenobarbital-inducible enzyme; mRNA levels reached 210 and 420% of control in females and males, respectively. In addition, mRNA levels for ST2A2, a female-specific ST gene, were suppressed 50% in females and induced 120% over control in males. mRNA expression for all other forms of rat liver UGT and ST isozymes that were tested was not significantly affected by tamoxifen treatment. Overall, these results demonstrate that tamoxifen has significant effects on hepatic phase II enzyme expression that may have implications for the carcinogenicity and/or therapeutic activity of the drug.

Animals↗

PubMed1996

Karyotypic changes in a multistage model of chemical hepatocarcinogenesis in the rat.

Karyotypic analysis of the stages of rat hepatocarcinogenesis has been facilitated by the development of an initiation-promotion-progression (IPP) protocol that permits separation and characterization of morphologically normal and altered hepatocytes in each of these three stages. The expression of the membrane antigen gamma-glutamyl transpeptidase (GGT) during the promotion and progression stages of rat hepatocarcinogenesis permits the isolation, culture, analysis, and comparison of hepatocytes in the two stages, which express this marker of carcinogenesis. Female rats were administered 10 mg diethylnitrosamine/kg at 5 days of age. One group of initiated rats was maintained on dietary phenobarbital admixed into a laboratory chow diet at 0.05% for 9 months after weaning (promotion protocol). This initiation-promotion (IP) group was compared with one subjected to the complete IPP protocol. The IPP group was initiated with diethylnitrosamine, maintained on phenobarbital for 6 months after weaning, and then subjected to a 70% partial hepatectomy and administered 100 mg ethylnitrosourea/kg 24 h later. These rats on the IPP protocol were then maintained on phenobarbital for an additional 3 months prior to sacrifice. At sacrifice, single hepatocyte suspensions were obtained and separated into populations of cells expressing or not expressing GGT. These hepatocyte populations were cultured separately and subjected to standard cytogenetic analysis. At least five animals per treatment and 100 metaphase spreads of good morphology per animal were examined. Although GGT- cells from the IP protocol were 80% tetraploid and 20% diploid, the GGT+ hepatocytes were greater than 90% diploid. The GGT+ cells from this protocol had a low rate of random aneuploidy (4.0 +/- 1.3%) compared with corresponding cells from the IPP protocol, but a higher level of background aneuploidy compared with GGT- cells from the IP protocol. The GGT+ hepatocytes from animals on the IPP protocol had a 35% incidence of aneuploidy. In addition, the GGT+ population had a 28 +/- 5% incidence of chromosomal breakage and a 17 +/- 5% incidence of chromosomal rearrangements. The primary nonrandom chromosomal changes observed in cells from the IPP protocol included duplication of all or part (1q37-43) of chromosome 1 and the loss of chromosomes 3p and/or 6q. These studies indicate that rat hepatocytes in the stage of promotion are euploid, whereas those in the stage of progression exhibit considerable genetic instability. The presence of multiple copies of chromosome 1 or a duplication of a region of this chromosome indicates that alteration of gene dosage for one or more of the genes present in this region is critical to the neoplastic conversion of rat hepatocytes, whereas the loss of all of 3p and the last light band of 6q may indicate the presence of tumor suppressor genes. Thus, the IP and IPP protocols coupled with the ability to isolate GGT+ and GGT- hepatocytes permit the differential cytogenetic characterization of the stages of promotion and progression in rat hepatocarcinogenesis.

Animals↗

PubMed1996

Cytogenetic analysis of three rat liver epithelial cell lines (WBneo, WBHa-ras, and WBrasIIa) and correlation of an early chromosomal alteration with insulin-like growth factor II expression.

Cytogenetic changes that occur during the progression of rat hepatocarcinogenesis were assessed with three rat liver epithelial cell lines derived from WB cells. Previously characterized WBneo, WBras, and WBrasIIa cells were grown in culture and analyzed for structural and numerical chromosomal integrity by banded karyotype analysis. The WBneo cells had a low level of aneuploidy with a consistent loss of the Y chromosome by passage 7. The ras-transfected cell line selected for growth in soft agar, WBras, had acquired a loss of chromosome 3 (12%) or 3p (34%), a trisomy of chromosome 1, as well as the chromosome Y loss. The cell line produced from tumors generated by injection of the WBras cells into a syngeneic F344 rat, WBrasIIa, contained additional chromosomal changes. The WBrasIIa line comprised cells retaining a trisomy of chromosome 1 (55%) and cells with two copies of chromosome 1, with a minimal duplication of 1q3.7 to 1q4.3 (45%). This tumor-derived cell line contained, in addition, a higher percentage of cells with a loss of all or part of chromosomes 3 and 6, indicating the possible presence of tumor suppressor genes in this region. The smallest region of duplication of chromosome 1 was bands 1q3.7-4.3. The insulin-like growth factor II (IGF-II) gene is located within the region of duplication on chromosome 1. Because IGF-II is both a rat liver mitogen and an inhibitor of apoptosis, its expression was examined in these three rat liver epithelial cell lines. Northern blot analysis demonstrated an increase in IGF-II mRNA expression in the WBras and WBrasIIa cell lines relative to the WBneo control cell line. Several IGF-II transcripts analogous to those detected in fetal rat liver were observed. An additional IGF-II transcript that migrates above the 28S ribosomal marker was also observed. These results were confirmed at the protein level by immunohistochemical and Western blot analysis. This increased expression of IGF-II may confer a selective growth advantage to rat liver epithelial cells with a duplication of 1q3.7-4.3. This growth advantage may be enhanced by the further sequential loss of putative tumor suppressor genes on chromosomes 3 and 6.

Animals↗

PubMed1996

The translational inhibitor cycloheximide represses growth factor depletion-induced apoptosis in an alb-SV40T transgenic rat liver cell line.

A transgenic rat line carrying the alb-SV40A transgene has been described by this laboratory. Several cell lines have been established from the livers of two of these rats. One of these cell lines, L37, exhibits a large nuclear/cytoplasmic ratio and a well-differentiated cytoplasm containing numerous organelles. When L37 cells are placed into culture medium lacking necessary growth factors, cellular proliferation continues for 48 hours after medium change. Subsequent to the initial 48 hours, cells begin to shrink and lose contact with adjacent cells, eventually sloughing off the culture plate surface, with most cell deaths occurring between 48 and 96 hours after medium change. Microscopic examination of sloughing cells indicates they possess highly convoluted and blebbed plasma membranes, a morphological characteristic of apoptosis. Ultrastructural studies demonstrate the ubiquitous presence of apoptotic bodies. When DNA isolated from growth factor-depleted cells is resolved on agarose gels, DNA fragmentation ladders are observed at times of maximum apoptotic change. Quantitative analysis of L37 cells between 48 and 96 hours after the removal of the culture medium shows that 59% +/- 2% of the cells undergo apoptosis. When cycloheximide, puromycin, or actinomycin D is added to the L37 cultures, only cycloheximide is able to repress apoptosis, indicating that the mechanism of apoptosis in the L37 liver-derived cell line requires a cycloheximide-sensitive translational event. The extremely high rate of apoptosis, together with the maintenance of hepatocellular characteristics, indicates the usefulness of this cell line as a model in which to study the mechanisms of hepatocellular apoptosis.

Albumins↗

PubMed1996

Stage-specific gene expression during hepatocarcinogenesis in the rat.

The alteration of genetic expression ubiquitously seen in both preneoplastic and neoplastic tissues has been investigated for many years in the hope that the critical molecular changes resulting in cancer can be elucidated. The alteration of the expression of specific genes has already been employed in diagnostic and even screening procedures for this disease. In the past many observations of such alterations have led to a variety of theories but not definitive generalizations. Studies of the alteration of genetic expression may now be viewed in the light of our understanding of the multistage nature of neoplastic development. This brief review describes a number of genes the expressions of which are altered during the stages of initiation and promotion, in contrast to the alteration of expression of genes during the stage of progression. The promotion stage is concerned primarily with the chronic interaction of promoting agents in the environment with the genetic apparatus of the cell, played out on the altered genetic background resulting from the stage of initiation. In contrast, the progression stage is characterized primarily by an evolving karyotypic instability resulting in continual genetic changes during this stage. On the basis of these distinctions it is possible to identify genes the altered expression of which is unique to the stage of progression. The identification of these genes and an understanding of mechanisms resulting in their altered expression will allow not only a better molecular characterization of the progression stage but also the quantitative analysis of neoplastic development in several model animal systems as well as eventually in the human.

Animals↗

PubMed1996

Relation between fat malabsorption and transit abnormalities in human carcinoid diarrhea.

BACKGROUND & AIMS: Fat and complex carbohydrates in the distal bowel activate "brakes" inhibiting upper gut motility. The hypothesis of this study was that rapid transit carcinoid diarrhea in association with steatorrhea results in impairment of gastric emptying. METHODS: Fifteen patients with carcinoid diarrhea without prior gastrointestinal resection or whose small bowel resection was limited to < 100 cm of ileum were studied. Gastrointestinal transit was measured scintigraphically with a standardized meal. Percentage of ingested fat excretion was calculated. RESULTS: Mean length of small bowel resected was 33 cm, and mean 24-hour urine 5-hydroxyindoleacetic acid was 120 mg. Fourteen patients had increased daily stool weights, and 10 had increased stool fat excretion (mean, 13%). Transit was accelerated in the small bowel in 14 and in the colon in all patients. The lag time for gastric emptying was prolonged in 2 patients who had no previous resection. Gastric emptying rate was accelerated in 5, normal in 7, and delayed in 3 patients. CONCLUSIONS: Ileal and colonic brakes do not seem to delay gastric emptying in patients with carcinoid diarrhea associated with rapid transit and mild to moderate steatorrhea.

Aged↗

PubMed1996

The effect of tamoxifen and two of its non-isomerizable fixed-ring analogs on multistage rat hepatocarcinogenesis.

Long-term treatment of breast cancer patients with tamoxifen has prompted concern over potential toxicity of this drug with chronic administration. Since tamoxifen has estrogenic action in the rat liver and estrogenic agents can increase hepatoma incidence in rats, tamoxifen and two non-isomerizable, fixed-ring analogs (FRT1 and FRT2) were evaluated as promoting agents in a two-stage model of hepatocarcinogenesis in female Fischer F344 rats. The rats were subjected to 70% partial hepatectomy and half of the animals were administered the initiating agent, diethylnitrosamine (DEN; 10 mg/kg body wt), while the other half were not initiated. Groups of initiated and uninitiated animals were allowed to recover for 2 weeks and were then administered tamoxifen or one of the fixed-ring analogs admixed into AIN-76A diet at 25, 100 or 250 mg/kg diet. After 6 months of anti-estrogen administration the rats were sacrificed and uterine weights, blood levels of anti-estrogen, and liver histopathology were assessed. Uterine weights were decreased 2- to 3-fold by each of the agents, consistent with an anti-estrogenic action in the rat. The serum levels in rats administered 250 mg anti-estrogen/kg diet for 6 months were 320+/-20 ng/ml for tamoxifen, 320+/-10 for FRT1 and 350+/-20 for FRT2. The liver levels after a 6 month administration of 250 mg anti-estrogen/kg diet were 13 870+/-860 ng/g for tamoxifen, 13 300 +/-860 for FRT1 and 26 900+/-1900 for FRT2. A dose-dependent increase in serum and liver level of each compound was noted when measured at the 6 month time period. The number and percentage of the liver occupied by altered hepatic foci (AHF) were determined by quantitative stereology. A dose-dependent increase above initiated controls was observed in the initiated, tamoxifen-treated rats. Both fixed-ring analogs also increased the number and size of AHF compared with initiated controls, but were less potent than tamoxifen, suggesting that tamoxifen has an intrinsic promoting action in the liver that is independent of its ability to isomerize to more potent estrogenic compounds. In addition, the fixed-ring analogs have a weaker promoting activity in the rat liver than does tamoxifen. This may be due to pharmacokinetic differences at the lower two doses, but it is independent of achieved serum level at the highest dose and hence may reflect differences in intrinsic activity of these compounds. Thus tamoxifen and the two fixed-ring analogs promote the development of rat hepatocarcinogenesis.

Animals↗

PubMed1996

Induction of hepatic aneuploidy in vivo by tamoxifen, toremifene and idoxifene in female Sprague-Dawley rats.

Since tamoxifen is efficacious for the prevention of second primary breast neoplasms in humans and has a low reported incidence of acute side effects, several structurally related compounds have been developed for the treatment of breast cancer including toremifene and idoxifene. We have compared the karyotypic alterations that occur after a single per os administration of 35 mg/kg of tamoxifen, toremifene or idoxifene to female Sprague-Dawley rats. One day following treatment, the rats were sacrificed and the hepatocytes isolated and cultured. After 47 h in culture, colcemid was added for 3 h prior to harvest of the hepatocytes for karyotypic evaluation. At least 100 metaphase spreads were examined for each of five rats per treatment. Toremifene resulted in aneuploidy in 50 +/- 7% of the cells examined and idoxifene induced a 57 +/- 4% aneuploidy compared with the 85 +/- 7% level induced by tamoxifen. Since the level of aneuploidy in solvent-treated rats was 3 +/- 3 %, the induction of aneuploidy in at least 50% of the cells from rats treated with tamoxifen, toremifene or idoxifene was highly significant. Analysis of electron micrographs of cultures treated with these antiestrogens demonstrated a range of phenotypes including multipolar spindles in toremifene-treated rats and condensed chromosomes in the presence of an intact nuclear envelope in occasional idoxifene-treated rat hepatocytes. The exclusion of chromosomes from the spindle apparatus and the lagging of some chromosomes on the metaphase plate correlate with the high rate of induction of aneuploidy in the rat liver as determined by karyotypic analysis of hepatocytes from rats treated with these triphenylethylenes.

Aneuploidy↗

PubMed1996

Effect of the separate and combined administration of mestranol and phenobarbital on the development of altered hepatic foci expressing placental form of glutathione S-transferase in the rat.

The stages in the carcinogenesis process include initiation, promotion and progression. Although many characteristics of tumor promotion and promoting agents have been reported, relatively few studies on the effects of combinations of promoting agents have been detailed. For study of the combined effects of phenobarbital (PB) and mestranol (MS) in multistage rat hepatocarcinogenesis, an initiation-promotion protocol was developed. Female rats were injected i.p. at 5 days of age with either diethylnitrosamine (DEN) (10 mg/kg) or the solvent tricaprilyn. At weaning, approximately 10 rats from both the DEN-initiated and the solvent control groups were provided basal diet alone, PB (10, 100 or 500 mg/kg diet), MS (0.02 or 0.2 mg/kg diet) or various combinations of both PB and MS in the basal diet. At 8 months of age, the rats were killed and the livers removed, sectioned and fixed in ice-cold acetone. Sections of 5 microgram thickness were stained for placental glutathione S-transferase (PGST) expression, and the volume fraction of liver occupied by altered hepatic foci was determined by stereology. In addition, incorporation of bromodeoxyuridine into nuclei of PGST-expressing (focal) and non-PGST-expressing (non-focal) hepatocytes was determined. Administration of the highest dose of PB resulted in a significant decrease in non-focal hepatocyte labeling index, with a 4-fold differential between the focal and non-focal hepatocyte labeling index. Administration of 0.2 mg/kg diet MS resulted in effective promotion. The non-focal labeling index was increased and the focal labeling index was further enhanced (3-fold) relative to the non-focal index by this dose of MS. Combination of the lower MS dose with PB resulted in at least an additive promoting effect; however, a lower volume fraction was noted for the combination of low MS dose plus the highest PB dose. Combination of the higher MS dose with PB resulted in an elevation of volume fraction only for the middle PB dose. These findings indicate that the potency of promotion by mixtures is modulated by the dose of each component as well as by pharmacodynamic and pharmacokinetic properties of each component of the mixture.

Animals↗