Biomedical subjects

M C Weiss

Publications and source records attributed to M C Weiss.

At least 55 records · Page 3Linked to original sources

PubMed1992

Assignment of the rat genes coding for alpha 1-antitrypsin (PI), phosphoenolpyruvate carboxykinase (PEPCK), alcohol dehydrogenase (ADH), and fructose-1,6-bisphosphatase (FDP).

The chromosomal localization of four genes which are expressed mainly in the liver has been undertaken for the rat. Using a panel of hybrid clones segregating rat chromosomes, and Southern blot analysis, alpha 1-AT (PI), PEPCK, ADH and FDP are assigned to rat Chromosomes (Chr) 6, 3, 2 and 17, respectively. Groups of synteny among rat, mouse and human species are discussed in relationship to the new assignments.

Alcohol Dehydrogenase↗

PubMed1992

Breast recurrence and survival related to primary tumor location in patients undergoing conservative surgery and radiation for early-stage breast cancer.

Between 1977 and 1986, 886 pts with Stage I and II breast cancer underwent excisional biopsy, axillary dissection and radiation. Median follow-up was 5 years (range 2 months-13 years). The patients were divided into four groups according to the primary tumor location: 1) outer (495 patients), 2) inner (202 patients), 3) central (119 patients), and 4) subareolar (70 patients). Subareolar tumors were defined as those immediately beneath the nipple-areolar complex or within 2 cm of the areolar margin. The comparability of the groups was assed in terms of clinical T stage, patient age, histology, final pathologic margin status, estrogen and progesterone receptor status, pathologic nodal status, and use of adjuvant chemotherapy. There were no significant differences among the four groups in the distribution of these factors except for the pathologic nodal status (outer 38% positive nodes, inner 24%, central 23%, subareolar 31%) p = .0004. There were no significant differences in 5 year actuarial overall survival (91% vs 86% vs 92% vs 91%, p = .34), relapse-free (75% vs 74% vs 80% vs 79%, p = .77), or NED survival (82% vs 78% vs 87% vs 84%, p = .29) for the four groups. A separate analysis for pathologic node negative and node positive patients revealed similar findings. For node-negative patients, the 5 year actuarial overall survival was 93% vs 88% vs 94% vs 91% (p = .20), the relapse-free survival was 78% vs 76% vs 82% vs 79% (p = .49), and the NED survival was 86% vs 81% vs 88% vs 86% (p = .46). For node-positive patients, the 5 year actuarial overall survival was 87% vs 82% vs 84% vs 90% (p = .59), relapse-free survival was 69% vs 66% vs 77% vs 80% (p = .78), and NED survival was 75% vs 68% vs 85% vs 80% (p = .66). Patterns of first failure were also not significantly different among the four groups: local only first failure (7% vs 4% vs 5% vs 8%, p = .49), any local first failure, i.e., +/- simultaneous distant metastases (8% vs 5% vs 5% vs 9%, p = .61), regional only (2% vs 1% 1% vs 0%, p = .65), any regional (4% vs 3% vs 3% vs 3%), or distant metastases (11% vs 17% vs 9% vs 10%, p = .16). A separate analysis of node negative and node positive patients revealed similar findings.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1992

Outcome of conservative therapy for invasive breast cancer by histologic subtype.

Between 1977 and 1986, 879 patients with Stage I and II breast cancer underwent excisional biopsy, axillary dissection, and radiation. Median follow-up was 61 months (range 2-159 months). The patients were divided into seven groups based on histologic subtype: (a) 368 patients with both infiltrating and intraductal ductal carcinoma, (b) 389 infiltrating ductal carcinoma, (c) 41 infiltrating lobular carcinoma, (d) 23 combined infiltrating ductal and lobular carcinoma, (e) 28 medullary carcinoma, (f) 12 colloid carcinomas, and (g) 18 tubular carcinomas. Significant differences in clinical T status, pathologic nodal involvement, administration of chemotherapy, estrogen receptor positivity, progesterone receptor positivity, and age were observed between some histologic subgroups. Tubular and colloid carcinomas were more likely to present with T1 lesions, hormone receptor positivity, and node negative status than the other histologic subtypes. Most medullary carcinomas were hormone receptor negative and were younger than 50 years old. Infiltrating lobular carcinoma patients were more frequently lymph node negative, older, node negative, and estrogen receptor positive compared to the other groups (except for tubular and colloid patients). Differences in the administration of chemotherapy primarily reflected differences in lymph node involvement. Location of the tumor in the breast and menopausal status did not correlate with histologic subtype. There were no significant differences in 5-year actuarial overall survival, cause-specific survival, or relapse-free survival between the histologic categories. In addition, patterns of first failure were not significantly different among the histologic groups in terms of local-only first failure, any local component of first failure, regional-only first failure, or any regional component of first failure. There was, however, a difference among the seven groups in distant metastasis-only at first failure with invasive ductal carcinomas having the highest rate. Despite this difference, histologic subtype had no impact on survival. The site of in-breast failure relative to the location of the original tumor was not significantly different between groups. The histologic subtype of invasive breast cancer is not an independent risk factor in predicting survival or pattern of failure. Conservative surgery and radiation therapy is effective treatment of ductal, lobular, medullary, colloid, and tubular invasive breast cancer.

Adenocarcinoma↗

PubMed1992

Microinvasive ductal carcinoma of the breast treated with breast-conserving surgery and definitive irradiation.

An analysis was performed of 39 consecutive women with microinvasive ductal carcinoma of the breast treated with breast-conserving surgery and definitive irradiation during the period 1977 to 1988. Microinvasive ductal carcinoma was defined as predominantly intraductal carcinoma with microscopic or early invasion. Surgical treatment of the primary tumor included excisional biopsy or wide resection. Axillary lymph node staging showed that 37 patients were pathologically node negative and two patients were pathologically node positive, each with only one positive lymph node. The median follow-up was 55 months (mean = 65 months; range = 25-135 months). The 5-year actuarial rate of overall and cause-specific survival were both 97%. The 5-year actuarial rate of freedom from distant metastases was 93%. Nine patients developed a recurrence in the breast; eight of the nine patients had isolated local only first failures, and one of the nine patients had a local recurrence simultaneously with distant metastases. The median time to local failure was 42 months (mean = 53 months; range = 20-116 months). Of the eight patients with local only first failure, seven patients have been salvaged with further treatment and remain free of disease at the time of last follow-up, and one patient has died of subsequent distant metastatic disease. Median follow-up after salvage treatment was 29 months (mean = 27 months; range = 0-54 months). Comparison of the patients with microinvasive ductal carcinoma with two control groups of intraductal carcinoma and invasive ductal carcinoma was performed. Although the rate of local failure was significantly higher for patients with microinvasive ductal carcinoma as compared to the two control groups, the rates of survival and freedom from distant metastases for patients with microinvasive ductal carcinoma were intermediate to the two control groups. Because of the high rates of survival and freedom from distant metastases and because of the ability to salvage patients with local recurrence, breast-conserving surgery and definitive irradiation should continue to be considered as an alternative to mastectomy for appropriately selected and staged patients with microinvasive ductal carcinoma of the breast.

Adult↗

PubMed1992

Cell phenotype, binding affinity and promoter structure modulate transactivation by HNF1 and LAP.

To evaluate the importance of the transcription factors known to bind to the albumin promoter as well as the parameters involved in their activity, we have used cotransfections with an albumin promoter-cat plasmid combined with expression vectors driving the expression of cDNAs coding for liver-enriched factors known to interact with this promoter. We describe the characteristics of a set of clones of hepatic origin: well differentiated, partial variants or pleiotropic dedifferentiated variants. These lines have been characterized for the accumulation of RNAs corresponding to each of the albumin promoter-binding factors. Only HNF1, and to a lesser extent C/EBP, show differences depending upon the differentiation state of the cells. Overexpression of exogenous HNF1 in these cells reveals that this factor is able to transactivate the albumin promoter only in variant cells where the endogenous protein is limiting. By contrast, if the HNF1-binding site is of weak affinity, overexpression of exogenous HNF1 stimulates the albumin promoter even in the HNF1-rich differentiated cells. Overexpression of exogenous LAP strongly transactivates an artificial promoter containing one LAP-binding site, but surprisingly in all the cell lines, it has little effect upon the albumin promoter. These results demonstrate that the transactivation potential of a given transcription factor depends on the degree of differentiation of the recipient cells, on the promoter structure, and on the affinity of the binding site for this factor.

Albumins↗

PubMed1991

Increased G2 delay in radiation-resistant cells obtained by transformation of primary rat embryo cells with the oncogenes H-ras and v-myc.

Cell cycle perturbation after irradiation was studied in five cell lines transfected with oncogenes. Two immortalized, radio-sensitive cell lines with D0s of 1.06 and 1.08 Gy were compared to three radioresistant cell lines with D0s of 1.68-2.17 Gy. The sensitive cell lines were transfected with the v-myc or c-myc oncogenes, the resistant cell lines with the v-myc plus H-ras oncogenes. Exponentially growing populations were exposed to 5, 10, or 15 Gy of orthovoltage radiation. The percentage of cells in each phase of the cell cycle was determined at various times after irradiation using flow cytometry. All cell lines underwent a dose-dependent arrest in G2 phase after irradiation, but the resistant cell lines underwent a significantly longer arrest in G2 phase after irradiation than did the sensitive cell lines. In conjunction with other results from our laboratories, we suggest that this difference in G2 arrest may be the basis for the increased resistance of cells transfected with oncogenes to irradiation.

Animals↗

PubMed1990

Synergistic effect of the v-myc oncogene with H-ras on radioresistance.

Resistance of tumors to irradiation or chemotherapeutic agents is thought to be one of the reasons why patients who present with early malignancies may not be cured. Much is now known about the molecular mechanisms that underlie drug resistance, but until recently little was known about genetic contributions to radiation resistance. Some evidence now links oncogenes, particularly the ras family of oncogenes, to radiation resistance but heterogeneity between tumors and cell lines has complicated this analysis. Primary rat embryo cells have been chosen as a model system in which the effects on radiation resistance of the H-ras oncogene could be studied on a uniform genetic background. These cells offer several useful advantages. The cells prior to transformation are diploid, and because they have been in culture only for a few passages prior to transformation with the oncogene it is unlikely that any preexisting mutation affecting radiation response could be present. Additionally, the use of rat embryo cells permitted the study of the effects of a second oncogene on the appearance of the radioresistant phenotype. The results show that the activated H-ras oncogene is associated with radiation resistance in primary rat cells after transformation but that the effect of the oncogene by itself is small. However, the oncogene v-myc, which has no effect on radiation resistance by itself, has a synergistic effect on radiation resistance with H-ras. There appear to be differences in the phenotype of radiation resistance associated with these two forms of transfectants. Thus, radiation resistance seen with H-ras by itself is characterized by a change in the slope of the radiation survival curve at high radiation doses but little or no change within the should region of the radiation survival curve. Radiation resistance seen in H-ras plus v-myc transformants is also characterized by an increase in the slope of the curve at high doses but there is also a large effect within the shoulder region of the radiation survival curve. These studies led to the following conclusions: (a) the radioresistant phenotype is not due to preexisting genetic heterogeneity in the cells prior to transfection; (b) the radiation resistant phenotype of cells transformed by H-ras is seen to a greater degree in cells which also contain the v-myc oncogene; (c) the v-myc oncogene may play an important role in the phenotype of radiation resistance at low doses that is within the range most critical for clinical practice.

Animals↗

PubMed1990

Genetic analysis of aflatoxin B1 activation in rat hepatoma cells.

We present a strategy to elucidate the rate-limiting steps in activation of carcinogenic compounds by cytochromes P450. The principle was to select Reuber rat hepatoma cells for resistance to a procarcinogen. The hypothesis was that resistant cells should be systematically deficient in the P450 enzyme(s) involved in the activation process. Here we present an example of the use of this approach using aflatoxin B1 (AFB1), a potent hepatocarcinogen, as the selective agent. Parental cells as well as individual and pooled colonies selected for AFB1 resistance from three independent rat hepatoma lines were characterized for their content of 1) mRNA hybridizing to cDNA and/or oligonucleotide probes for cytochromes P450IIB1, P450IIB2 and albumin; and 2) aldrin epoxidase activity. Parental aflatoxin B1-sensitive cells were shown to express P450IIB1 but not P450IIB2. The majority of the aflatoxin B1-resistant clones failed to accumulate cytochrome P450IIB1 mRNA and expressed no or only very low aldrin epoxidase activity. Albumin mRNA levels remained unchanged, demonstrating that loss of expression of cytochrome P450IIB1 was not a consequence of a general dedifferentiation event. A revertant population showing restoration of both cytochrome P450IIB1 mRNA accumulation and aldrin epoxidase activity was fully sensitive to aflatoxin B1. The correlation between expression of cytochrome P450IIB1 and sensitivity to aflatoxin B1 in both parental cells and revertants strongly suggests that cytochrome P450IIB1 is a major contributor to the activation of aflatoxin B1 in rat hepatoma cells. The kind of strategy described here could be applied to other compounds that become cytotoxic for hepatoma cells following activation by cytochromes P450.

Aflatoxin B1↗

PubMed1990

The role of the H-ras oncogene in radiation resistance and metastasis.

The sensitivity of tumor cells to the killing effects of ionizing radiation is thought to be one of the major determinants of curability of tumors in patients treated with radiation therapy. This paper reviews the evidence from our laboratory and other groups which supports a role for oncogenes in the induction of radioresistance in cultured mammalian cells. Primary rat embryo cells (REC) were chosen as a model system in which the effects on radiation resistance of the H-ras oncogene could be studied on a uniform genetic background. These cells offered several useful advantages. The cells prior to transformation are diploid and because they have been in culture only for a few passages prior to transformation with the oncogene it is unlikely that any preexisting mutation affecting radiation response could be present. Additionally, the use of REC permitted the study of the effects of synergism between oncogenes on the induction of the radioresistant phenotype. The results show that the activated H-ras oncogene induces radiation resistance in primary rat cells after transformation, but that the effect of the oncogene itself is small. However, the myc oncogene, which has no effect on radiation resistance by itself, appears to have a synergistic effect on the induction of radiation resistance by H-ras. Radiation resistance induced by H-ras plus myc is characterized by an increase in the slope of the curve at high doses but there is also a large effect within the shoulder region of the radiation survival curve. The AdenoE1A oncogene which will also act synergistically with ras in transformation assays plays a less clear-cut role in assays of radiation resistance. The H-ras oncogene is also known not only to transform cells but also to induce metastatic behavior in the tumors which form after these transformed cells are injected into syngeneic animals or nude mice. We have also shown in our primary rat embryo cell system that the induction of metastatic behavior in transformed cells, like the induction of radioresistance depends on a complex interaction between oncogenes and the cellular background. This evidence will be reviewed to demonstrate some of the analogies between radiation resistance and metastasis as examples of the complex alterations in cellular phenotype which occur after oncogene transfection.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Activation of phenylalanine hydroxylase expression following genomic DNA transfection of hepatoma cells.

Genomic DNA from cells producing the liver-specific enzyme phenylalanine hydroxylase (PAH) should contain, in active form, genes encoding regulators of PAH expression. We have transfected genomic DNA from PAH-producing rat hepatoma cells to PAH-deficient mouse hepatoma cells, and selected in tyrosine-deficient medium for cells producing the enzyme. The frequency of colonies obtained was similar to that for transfer of a single-copy gene. Genomic DNA from the primary transfectants permitted the isolation in tyrosine-free medium of secondary transfectants. Control experiments, using donor DNA from PAH-negative rat or mouse hepatoma cells also permitted the isolation of PAH-expressing cells, but at a frequency 10-30 times lower. The transfectants isolated in tyrosine-deficient selective medium all produced PAH mRNA. This transcript was from the previously silent mouse gene, which had not undergone amplification or gross rearrangement. Most of the transfectants contained less than 0.1% rat DNA. A search for other functions that might have been simultaneously activated was negative. It is concluded that the mouse transfectants acquired from the PAH+ rat donor some sequences whose presence permits activity of the previously silent PAH gene.

Animals↗

PubMed1990

Assignment of the rat genes coding for phenylalanine hydroxylase (PAH), tyrosine aminotransferase (TAT), and pyruvate kinase (PKL) to chromosomes 7, 19, 2, respectively.

A panel of hybrid clones segregating rat chromosomes in a mouse background was used to determine the chromosomal localization of three genes specifically expressed in hepatocytes. The phenylalanine hydroxylase, tyrosine aminotransferase, and pyruvate kinase genes were assigned to rat chromosomes 7, 19, and 2, respectively.

Animals↗

PubMed1990

Interaction of trans-acting factors and re-expression of liver functions in hepatoma hybrid cells.

The specific functions expressed by differentiated cells are extinguished when these cells are crossed with somatic cells of another histotype or with cells of the same differentiation that fail to express these functions: in rat hepatoma x mouse fibroblast hybrids, tyrosine aminotransferase (TAT) and phosphoenolypyruvate carboxykinase (PEPCK) activities are extinguished as they are in hybrids between the same rat hepatoma cell line and mouse hepatoma cells that do not express these two enzymes. The locus Tse-1 (tissue-specific extinguisher) on mouse chromosome 11 is responsible for the extinction of TAT and PEPCK in rat hepatoma x mouse fibroblast hybrids and loss of mouse chromosome 11 leads to re-expression of these two enzymes. We report here an analysis of rat hepatoma x mouse hepatoma hybrids that demonstrates that loss of mouse chromosome 11 is not necessary for re-expression of TAT and PEPCK. In view of the facts that Tse-1 is active in mouse hepatoma cells that do not express TAT and PEPCK and that the presence of only one active Tse-1 locus is sufficient to extinguish these functions in 2s rat hepatoma cells, we conclude that re-expression of TAT and PEPCK in rat hepatoma x mouse hepatoma hybrids is due to the epistatic action of tissue-specific trans-acting activators that override the Tse-1 effect.

Animals↗

PubMed1990

An exogenous albumin promoter can become silent in dedifferentiated hepatoma variants as well as intertypic hybrids.

In order to evaluate the ability of an exogenous tissue-specific promoter to undergo the same dynamic changes in activity as the endogenous one, a 400-base pair fragment of the rat albumin proximal promoter, upstream of the bacterial gpt gene, has been introduced into rat hepatoma cells. Four clones containing a single integrated copy of the construct and producing substantial amounts of albumin and of xanthine phosphoribosyltransferase were isolated. These clones were subjected to two treatments known to result in silencing of the albumin gene: selection for dedifferentiated variants, and fusion with L-cell fibroblasts. In most cases, the albumin-negative progeny obtained no longer expressed the gpt gene: the exogenous promoter of 400 base pairs must contain the sequences required to respond to the mechanisms that block activity of the endogenous gene. However, exceptions were observed: the albumin-deficient variants of one clone remained xanthine phosphoribosyltransferase positive, and some of the albumin-negative hybrids from a different clone continued to produce xanthine phosphoribosyltransferase. These cases of dissociation in expression of the endogenous and the exogenous genes indicate that the site of integration of the alb-gpt construct in one clone renders the sequences insensitive to the mechanisms responsible for albumin gene silencing in dedifferentiated variants, and in the other clone to the mechanism of extinction. Consequently, the mechanisms causing gene silencing in variants and in intertypic hybrids must be different.

Aflatoxin B1↗

PubMed1989

Establishment of mouse and rat hepatoma cell clones showing stable expression of rabbit cytochrome P450 IA2.

Cytochrome P450 IA2, a liver-specific member of the 3-methylcholanthrene-inducible family, is never detected in established cell lines. With the aim of isolating cells stably producing this protein, we have used rat and mouse hepatoma cells as recipients in transfection experiments involving rabbit cytochrome P450 IA2 cDNA. We report here the isolation of five hepatoma cell clones expressing functional P450 IA2. The level of expression is comparable to that found in COS cells transiently transformed by other P450 cDNAs. It ranges between 0.4 and 1.6 pmol P450 IA2/mg total cell protein.

Animals↗

PubMed1989

Biochemical and genetic analysis of the nifUSVWZM cluster from Azotobacter vinelandii.

Azotobacter vinelandii genes contained within the major nif-cluster and designated orf6, nifU, nifS, nifV, orf7, orf8, nifW, nifZ, nifM, and orf9 are organized into at least two overlapping transcriptional units. Nitrogenase derepressed crude extracts of Azotobacter vinelandii mutant strains having individual deletions located within nifU, nifS, nifV, nifW, nifZ, or nifM were examined for nitrogenase component protein activities. The results of these experiments indicated that, in A. vinelandii, the nifU, nifS and nifM gene products are required for the full activation or the catalytic stability of the nitrogenase Fe protein. Deletion of the nifV gene resulted in lower MoFe protein activity, probably resulting from the accumulation of an altered FeMo-cofactor. The nifW and nifZ gene products were required for the full activation or catalytic stability of the MoFe protein. Deletion of nifZ alone or nifM alone did not appear to affect FeMo-cofactor biosynthesis. However, deletion of both nifZ and nifM eleminated either FeMo-cofactor biosynthesis or the insertion of FeMo-cofactor into the apo-MoFe protein. Other genes contained within the nifUSVWZM gene cluster (orf6, orf7, orf8, and orf9) were not required for Mo-dependent diazotrophic growth.

Azotobacter↗

PubMed1989

The rat albumin promoter is composed of six distinct positive elements within 130 nucleotides.

No fewer than six different positive regulatory elements concentrated within 130 base pairs constitute the rat albumin promoter, which drives highly tissue specific transcription in rat hepatoma cells in culture. Inactivation of each element led to a decrease in transcriptional efficiency: from upstream to downstream, 3- to 4-fold for distal elements III and II, 15-fold for distal element I, and 50-fold for the CCAAT box and the proximal element (PE). Three of these elements, distal elements III and II and, more crucially, the PE, were found to be involved in the tissue-specific character of transcription, with an additional negative regulation possibly superimposed at the level of the PE. Finally, our mapping of these regulatory elements in vivo entirely coincided with footprint data obtained in vitro, thereby allowing the tentative assignment of specific factors to the effects observed in vivo.

Albumins↗

PubMed1989

The rat albumin promoter: cooperation with upstream elements is required when binding of APF/HNF1 to the proximal element is partially impaired by mutation or bacterial methylation.

We have characterized in the accompanying paper (P. Herbomel, A. Rollier, F. Tronche, M.-O. Ott, M. Yaniv, and M. C. Weiss, Mol. Cell. Biol. 9:4750-4758, 1989) six different elements in the albumin promoter. One of them, the proximal element (PE), is the binding site for a strictly liver specific factor, APF/HNF1. This binding site contains a bacterial DAM DNA methylase methylation target sequence which, when methylated, decreases the affinity of the protein for this element. When the different albumin promoter constructions were prepared in an Escherichia coli deoxyadenosine methylase-negative strain, the respective contributions of the elements to the overall promoter activity were strikingly different. An intact proximal element plus the TATA box gave almost full transcriptional activity in transient transfection experiments and only in differentiated hepatoma cells of line H4II, whereas the distal elements (distal element III [DEIII], the NF1-binding site DEII, and the E/CBP-binding site DEI) had become essentially dispensable. Mutations affecting the CCAAT box showed only a two- to threefold decrease. When PE was methylated, mutated, or replaced by the homologous element from the alpha-fetoprotein gene, activity in the context of the short promoter (PE plus the TATA box) was abolished. However, activity was restored in the presence of the upstream elements, showing that cooperation with factors binding to the CCAAT box and distal elements favors the functional interaction of the liver-specific APF/HNF1 factor with lower-affinity binding sites.

Albumins↗

PubMed1988

Phenobarbital, dexamethasone and benzanthracene induce several cytochrome P450 mRNAs in rat hepatoma cells.

Hepatoma cells derived from the Reuber H35 rat hepatoma express cytochrome P450 enzymes of two major families: polycyclic aromatic hydrocarbon-inducible forms are found in both differentiated and dedifferentiated cells while phenobarbital (PB)-inducible forms are found only in differentiated cells. We report here that (i) benzanthracene and PB induce P450 c mRNA in differentiated and dedifferentiated cells and (ii) dexamethasone and PB induce P450 b/e and/or P450 PB1 mRNAs in differentiated cells but not in dedifferentiated cells.

Animals↗