Biomedical subjects

K L Rudolph

Publications and source records attributed to K L Rudolph.

16 recordsLinked to original sources

PubMed2003

Telomere shortening impairs organ regeneration by inhibiting cell cycle re-entry of a subpopulation of cells.

Telomere shortening limits the regenerative capacity of primary cells in vitro by inducing cellular senescence characterized by a permanent growth arrest of cells with critically short telomeres. To test whether this in vitro model of cellular senescence applies to impaired organ regeneration induced by telomere shortening in vivo, we monitored liver regeneration after partial hepatectomy in telomerase-deficient mice. Our study shows that telomere shortening is heterogeneous at the cellular level and inhibits a subpopulation of cells with critically short telomeres from entering the cell cycle. This subpopulation of cells with impaired proliferative capacity shows senescence-associated beta-galactosidase activity, while organ regeneration is accomplished by cells with sufficient telomere reserves that are capable of additional rounds of cell division. This study provides experimental evidence for the existence of an in vivo process of cellular senescence induced by critical telomere shortening that has functional impact on organ regeneration.

Animals↗

PubMed2003

Telomere shortening of epithelial cells characterises the adenoma-carcinoma transition of human colorectal cancer.

BACKGROUND: and aims: Chromosomal instability is one of the most consistent markers of sporadic colorectal cancer in humans. There is growing evidence that telomere shortening is one of the mechanisms leading to chromosomal instability and cancer initiation. METHODS: To test this hypothesis, the telomere length of colorectal epithelial cells and cells from connective tissue was determined at the adenoma-carcinoma transition at the cellular level by quantitative fluorescence in situ hybridisation. RESULTS: Our study showed that the telomere fluorescence intensity of epithelial cells was significantly weaker at the earliest morphologically definable stage of carcinoma-high grade dysplasia with minimal invasive growth-compared with the surrounding adenoma. In contrast, cells from connective tissue had a similar telomere signal intensity at the carcinoma stage compared with the adenoma, and in turn cells from connective tissue had overall significantly stronger telomere fluorescence signals compared with epithelial cells. CONCLUSIONS: These results demonstrate that short telomeres of epithelial cells characterise the adenoma-carcinoma transition during human colorectal carcinogenesis, suggesting that carcinomas arise from cells with critical short telomeres within the adenoma. Since the adenoma-carcinoma transition in colorectal cancer is characterised by an increase in chromosomal instability and anaphase bridges, our data support the hypothesis that short telomeres initiate colorectal cancer by induction of chromosomal instability.

Adenoma↗

PubMed2002

Telomerase activity, telomere length, and apoptosis: a comparison between acquired cholesteatoma and squamous cell carcinoma.

BACKGROUND: Cholesteatoma disease is characterized by accumulation of keratinizing epithelium. Several molecular markers of tumor formation have been found in cholesteatoma (e.g. upregulation of matrix metalloproteinases, c and activation of angiogenesis). Other molecular findings clearly distinguish between cholesteatoma and malignant tumors (e.g., lack of chromosomal instability, intact checkpoint responses). To further distinguish the molecular mechanisms in cholesteatoma from malignant tumors, the authors determined telomerase activity and telomere length in both tissue types. METHODS: To evaluate the role of telomerase activation and telomere length in cholesteatoma, 29 cholesteatoma samples and 9 squamous cell carcinomas were analyzed for telomerase activity and telomere length. In addition, the rate of apoptosis was determined in both groups, using the TdT-mediated dUTP nick end labeling technique. RESULTS: As previously described, a high proportion of squamous cell carcinoma exhibited telomerase activity (6/9, 66%). By contrast, a significantly lower rate of telomerase activity was found in cholesteatoma samples (1/29, 3.4%, p = 0.0002). Despite the differences in telomerase activity, the telomere length was similar in cholesteatoma (mean length 7.43 kb) and in squamous cell carcinoma (mean length 7.99 kb; difference not significant, p = 0.1364). The low rate of telomerase activity in cholesteatoma was accompanied by significantly higher rates of apoptosis in cholesteatoma (mean 30%) compared with squamous cell carcinoma tissue (mean 3%, p = 0.0031). CONCLUSIONS: Taken together, these data show that telomerase activation is a rare event in cholesteatoma and that the absence of telomerase activity is accompanied by high rates of apoptosis in cholesteatoma. It is proposed that the absence of telomerase limits the proliferative capacity of cholesteatoma by induction of apoptosis, whereas the presence of telomerase allows immortal growth of squamous cell carcinoma.

Adult↗

PubMed2001

Rescue of a telomere length defect of Nijmegen breakage syndrome cells requires NBS and telomerase catalytic subunit.

Nijmegen breakage syndrome (NBS) is a rare human disease displaying chromosome instability, radiosensitivity, cancer predisposition, immunodeficiency, and other defects [1, 2]. NBS is complexed with MRE11 and RAD50 in a DNA repair complex [3-5] and is localized to telomere ends in association with TRF proteins [6, 7]. We show that blood cells from NBS patients have shortened telomere DNA ends. Likewise, cultured NBS fibroblasts that exhibit a premature growth cessation were observed with correspondingly shortened telomeres. Introduction of the catalytic subunit of telomerase, TERT, was alone sufficient to increase the proliferative capacity of NBS fibroblasts. However, NBS, but not TERT, restores the capacity of NBS cells to survive gamma irradiation damage. Strikingly, NBS promotes telomere elongation in conjunction with TERT in NBS fibroblasts. These results suggest that NBS is a required accessory protein for telomere extension. Since NBS patients have shortened telomeres, these defects may contribute to the chromosome instability and disease associated with NBS patients.

Catalytic Domain↗

PubMed2001

Telomere dysfunction alters the chemotherapeutic profile of transformed cells.

Telomerase inhibition has been touted as a novel cancer-selective therapeutic goal based on the observation of high telomerase levels in most cancers and the importance of telomere maintenance in long-term cellular growth and survival. Here, the impact of telomere dysfunction on chemotherapeutic responses was assessed in normal and neoplastic cells derived from telomerase RNA null (mTERC(-/-)) mice. Telomere dysfunction, rather than telomerase per se, was found to be the principal determinant governing chemosensitivity specifically to agents that induced double-stranded DNA breaks (DSB). Enhanced chemosensitivity in telomere dysfunctional cells was linked to therapy-induced fragmentation and multichromosomal fusions, whereas telomerase reconstitution restored genomic integrity and chemoresistance. Loss of p53 function muted the cytotoxic effects of DSB-inducing agents in cells with telomere dysfunction. Together, these results point to the combined use of DSB-inducing agents and telomere maintenance inhibition as an effective anticancer therapeutic approach particularly in cells with intact p53-dependent checkpoint responses.

Animals↗

PubMed2001

Telomere dysfunction and evolution of intestinal carcinoma in mice and humans.

Telomerase activation is a common feature of advanced human cancers and facilitates the malignant transformation of cultured human cells and in mice. These experimental observations are in accord with the presence of robust telomerase activity in more advanced stages of human colorectal carcinogenesis. However, the occurrence of colon carcinomas in telomerase RNA (Terc)-null, p53-mutant mice has revealed complex interactions between telomere dynamics, checkpoint responses and carcinogenesis. We therefore sought to determine whether telomere dysfunction exerts differential effects on cancer initiation versus progression of mouse and human intestinal neoplasia. In successive generations of ApcMin Terc-/- mice, progressive telomere dysfunction led to an increase in initiated lesions (microscopic adenomas), yet a significant decline in the multiplicity and size of macroscopic adenomas. That telomere dysfunction also contributes to human colorectal carcinogenesis is supported by the appearance of anaphase bridges (a correlate of telomere dysfunction) at the adenoma-early carcinoma transition, a transition recognized for marked chromosomal instability. Together, these data are consistent with a model in which telomere dysfunction promotes the chromosomal instability that drives early carcinogenesis, while telomerase activation restores genomic stability to a level permissive for tumor progression. We propose that early and transient telomere dysfunction is a major mechanism underlying chromosomal instability of human cancer.

Adenocarcinoma↗

PubMed2001

Telomere dysfunction triggers developmentally regulated germ cell apoptosis.

Telomere dysfunction results in fertility defects in a number of organisms. Although data from fission yeast and Caenorhabditis elegans suggests that telomere dysfunction manifests itself primarily as defects in proper meiotic chromosome segregation, it is unclear how mammalian telomere dysfunction results in germ cell death. To investigate the specific effects of telomere dysfunction on mammalian germ cell development, we examined the meiotic progression and germ cell apoptosis in late generation telomerase null mice. Our results indicate that chromosome asynapsis and missegregation are not the cause of infertility in mice with shortened telomeres. Rather, telomere dysfunction is recognized at the onset of meiosis, and cells with telomeric defects are removed from the germ cell precursor pool. This germ cell telomere surveillance may be an important mechanism to protect against the transmission of dysfunctional telomeres and chromosomal abnormalities.

Animals↗

PubMed2001

K-ras mutations in the bile of patients with primary sclerosing cholangitis.

BACKGROUND AND AIMS: The development of cholangiocarcinoma (CCC) is a complication of primary sclerosing cholangitis (PSC). To date, no reliable factors have been described which can define those PSC patients at high risk for the development of CCC and the clinical diagnosis of CCC in PSC patients is difficult. Therefore, molecular markers of cholangiocarcinogenesis, such as K-ras mutations, may improve the early diagnosis of CCC or the timing of liver transplantation. METHODS: K-ras mutations were analysed by enriched polymerase chain reaction/restriction fragment length polymorphism in the bile fluid of 56 PSC patients and 20 patients with other cholestatic diseases. To assess the value of K-ras mutations as a risk factor for cholangiocarcinogenesis, patients were prospectively investigated over a mean period of 31.5 months. RESULTS: In contrast with the control group, 17 (30%) patients with PSC revealed K-ras mutations in bile fluid. The mean Mayo score was not significantly different between PSC patients with (mean score 0.70) and without (mean score 0.13; p=0.2) K-ras mutations. In contrast with the group of PSC patients without K-ras mutations, four CCCs and two dysplasia were diagnosed in the group of patients with K-ras mutations during the follow up investigation (p<0.001). CONCLUSIONS: Our results indicate that K-ras mutations in bile fluid of PSC patients represent frequent early events during cholangiocarcinogenesis. However, most of the PSC patients with K-ras mutations remained tumour free after a long follow up investigation which is in agreement with the fact that these mutations are not specific for malignancy but may also occur in normal bile duct mucosa or in dysplasias. Therefore, analysis of K-ras mutations in bile should not be used for diagnosis of CCC in PSC patients. However, the results of our prospective follow up investigation indicate that K-ras mutations in bile fluid of PSC patients have to be considered as risk factors for the development of CCC which may have implications for the timing of liver transplantation.

Adult↗

PubMed2000

Inhibition of experimental liver cirrhosis in mice by telomerase gene delivery.

Accelerated telomere loss has been proposed to be a factor leading to end-stage organ failure in chronic diseases of high cellular turnover such as liver cirrhosis. To test this hypothesis directly, telomerase-deficient mice, null for the essential telomerase RNA (mTR) gene, were subjected to genetic, surgical, and chemical ablation of the liver. Telomere dysfunction was associated with defects in liver regeneration and accelerated the development of liver cirrhosis in response to chronic liver injury. Adenoviral delivery of mTR into the livers of mTR(-/-) mice with short dysfunctional telomeres restored telomerase activity and telomere function, alleviated cirrhotic pathology, and improved liver function. These studies indicate that telomere dysfunction contributes to chronic diseases of continual cellular loss-replacement and encourage the evaluation of "telomerase therapy" for such diseases.

Adenoviridae↗

PubMed2000

Impact of the simultaneous administration of the (+)- and (-)-forms of formyl-tetrahydrofolic acid on plasma and intracellular pharmacokinetics of (-)-tetrahydrofolic acid.

PURPOSE: To detect possible interactions between (-)-formyl-tetrahydrofolic acid (leucovorin, (-)-fTHF) and (+)-formyl-tetrahydrofolic acid ((+)-fTHF) on the plasma and intracellular pharmacokinetics following their simultaneous administration. METHODS: Plasma levels of (-)-fTHF, (-)-methyl-THF, and (+)-fTHF were determined in samples from four volunteers following the administration of both (-)-fTHF and (+/-)-fTHF and in seven patients during a 5-fluorouracil (5-FU)/fTHF combination chemotherapy. In addition, the intracellular uptake of (14)C-(-)-mTHF in the presence of (+)-mTHF at increasing concentrations was measured in vitro. Analyses were performed using a highly specific high-performance liquid chromatography procedure. RESULTS: The pharmacokinetic parameters obtained for (-)-fTHF following the administration of (-)-fTHF only were: terminal half-life, 1.2 h; area under the curve, 10 microg. h/ml; maximum concentration, 12 microg/ml; clearance, 305 ml/min; volume of distribution, 19 l. The parameters did not differ significantly as compared with those obtained following the administration of (+/-)-fTHF to both volunteers and patients. There were no differences in the pharmacokinetics of (-)-mTHF or in the protein binding of both substances with the different forms of administration. The intracellular uptake of (14)C-(-)-mTHF did not depend on the presence of (+)-mTHF at either concentration. CONCLUSIONS: These data suggest that (-)-fTHF is not therapeutically superior to (+/-)-fTHF and that the latter is appropriate during combination chemotherapy with 5-FU/fTHF in patients with colorectal cancers.

Adult↗

PubMed2000

Hepatocellular carcinoma in Germany: a retrospective epidemiological study from a low-endemic area.

AIMS/BACKGROUND: This study was undertaken in order to assess the main features of hepatocellular carcinoma in Germany, a country with low incidences of this tumor. METHODS: Two hundred and eighty consecutive patients with hepatocellular carcinomas admitted to the Medical School Hannover between 1993-1997 were retrospectively studied. RESULTS: Reliable data for the assessment of the etiology and the tumor stage of HCC were available for 268 patients. The female/male ratio was 1/4. In 51.9% of the patients, HCC was associated with hepatitis virus B or C (HBV, HCV) infection: 35.1% with HBV, 26.9%) with HCV and 10% coinfection with HBV/HCV This result emphasizes the major impact of HBV and HCV infection in liver cancer in Germany. Of all patients with HCC 74.6%) had liver cirrhosis. The predominant majority of the HCC (87%) were restricted to the liver: in only 5.9% could regional lymph node metastases as well as 8.5%) metastases in other organs be clinically diagnosed by chest X-ray, computed tomography scan or sonography. Data to asses the Okuda tumor stage were available for 166 patients: 47% were classified as stage I, 47% as stage II and only 6% as stage III. Serum AFP were determined in 195 patients. In 66% of the patients, the AFP value was elevated, but only in 30% did the AFP level reach the value of 500 microg/l, which is considered to be significant for HCC diagnosis in patients with liver cirrhosis. The proportion of liver cirrhosis was higher in HCV (97.8%) versus HBV (80.6%) associated HCC, which was the only significant (p<0.05) difference in the characteristics of HCC according to the etiology. CONCLUSION: Our study shows that liver cirrhosis is the prime risk factor for hepatocarcinogenesis in Germany. However, the very high proportion of hepatitis virus related HCC, in particular the high proportion of HBV infections, contradicts the common view that alcohol is by far the most important etiological factor for hepatocarcinogenesis in low hepatitis virus endemic areas such as Germany.

Adult↗

PubMed2000

Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation.

Telomeres are specialized nucleoprotein complexes that serve as protective caps of linear eukaryotic chromosomes. Loss of telomere function is associated with rampant genetic instability and loss of cellular viability and renewal potential. The telomere also participates in processes of chromosomal repair, as evidenced by the 'capture' or de novo synthesis of telomere repeats at double-stranded breaks and by the capacity of yeast telomeres to serve as repositories of essential components of the DNA repair machinery, particularly those involved in non-homologous end-joining (NHEJ). Here we used the telomerase-deficient mouse, null for the essential telomerase RNA gene (Terc), to assess the role of telomerase and telomere function on the cellular and organismal response to ionizing radiation. Although the loss of telomerase activity per se had no discernable impact on the response to ionizing radiation, the emergence of telomere dysfunction in late-generation Terc-/- mice imparted a radiosensitivity syndrome associated with accelerated mortality. On the cellular level, the gastrointestinal crypt stem cells and primary thymocytes showed increased rates of apoptosis, and mouse embryonic fibroblasts (MEFs) showed diminished dose-dependent clonogenic survival. The radiosensitivity of telomere dysfunctional cells correlated with delayed DNA break repair kinetics, persistent chromosomal breaks and cytogenetic profiles characterized by complex chromosomal aberrations and massive fragmentation. Our findings establish a intimate relationship between functionally intact telomeres and the genomic, cellular and organismal response to ionizing radiation.

Animals↗

PubMed1999

p53 represses CAAT enhancer-binding protein (C/EBP)-dependent transcription of the albumin gene. A molecular mechanism involved in viral liver infection with implications for hepatocarcinogenesis.

p53 is a transcription factor that is activated by genotoxic stress and mediates cell cycle arrest and apoptosis. Here we demonstrate that infection of mouse liver with recombinant E1/E3-deleted adenovirus leads to p53 activation and simultaneously to the down-regulation of albumin gene expression. In vitro transcription assays indicate that transcriptional mechanisms mediated through the albumin promoter are responsible for reduced albumin mRNA levels during viral infection. Albumin expression is maintained in the liver by a combination of liver-enriched transcription factors such as CAAT enhancer-binding protein (C/EBP)alpha and C/EBPbeta. We show that p53 wild type and tumor-derived p53 mutations repress C/EBP-mediated transactivation of the albumin promoter. The binding of C/EBPalpha or -beta to its cognate sequence in the albumin promoter is not inhibited by p53 expression. Deletion analysis and domain swapping experiments show that repression of C/EBPbeta-mediated transactivation is dependent on the N-terminal domain of p53 and the transactivation domain, leucine zipper domain, and the inhibitory domain II (amino acids 163-191) of C/EBPbeta. Our results provide a molecular explanation for the p53-mediated down-regulation of liver-specific gene expression after viral infection. Additionally, as overexpression of p53 mutants is frequently found in undifferentiated hepatocellular carcinomas, the same mechanisms may contribute to the lack of liver-specific gene transcription in these tumors.

Albumins↗

PubMed1999

Longevity, stress response, and cancer in aging telomerase-deficient mice.

Telomere maintenance is thought to play a role in signaling cellular senescence; however, a link with organismal aging processes has not been established. The telomerase null mouse provides an opportunity to understand the effects associated with critical telomere shortening at the organismal level. We studied a variety of physiological processes in an aging cohort of mTR-/- mice. Loss of telomere function did not elicit a full spectrum of classical pathophysiological symptoms of aging. However, age-dependent telomere shortening and accompanying genetic instability were associated with shortened life span as well as a reduced capacity to respond to stresses such as wound healing and hematopoietic ablation. In addition, we found an increased incidence of spontaneous malignancies. These findings demonstrate a critical role for telomere length in the overall fitness, reserve, and well being of the aging organism.

Aging↗

PubMed1999

Differential regulation of extracellular matrix synthesis during liver regeneration after partial hepatectomy in rats.

Little is known about the modulation of the extracellular matrix (ECM) during liver regeneration. We studied the temporospatial expression of procollagens and of matrix metalloproteinases (MMPs) and their physiological antagonists, the tissue inhibitors of metalloproteinases (TIMPs) after two-thirds partial hepatectomy (PH) by Northern blot analysis and in situ hybridization. The entry of hepatocytes into the S-phase at 24 hours after PH was accompanied by a peak (sixfold induction) of hepatic TIMP-1 RNA levels that steadily declined thereafter to reach normal levels 144 hours after PH. Moderate MMP-2 and TIMP-2 RNA levels remained constant up to 144 hours after PH, and MMP-1 and -13 RNA were always undetectable. In situ hybridization showed a dramatic upregulation of TIMP-1 RNA transcripts in mesenchymal cells of portal, perisinusoidal and, to a lesser extent, pericentral areas. In contrast, scattered hepatocytes represented only a minor fraction (below 10%) of TIMP-1 RNA positive cells. When hepatocytes stopped DNA synthesis at 72 hours after PH, an upregulation of procollagen alpha1(I) and alpha2(III) transcripts was observed paralleled by threefold increased PIIINP levels in the sera. Our data reveal a tightly regulated program of de novo matrix synthesis after PH. Whereas interstitial procollagens appear to participate in the induction and maintenance of the quiescent hepatocyte phenotype, the early and localized expression of TIMP-1 indicates a role unrelated to its function as a general MMP-antagonist, e.g., as a growth promoting agent for hepatocytes.

Animals↗

PubMedDate not supplied

Phase II study of systemic gemcitabine chemotherapy for advanced unresectable hepatobiliary carcinomas.

BACKGROUND/AIMS: Patients with advanced unresectable hepatobiliary carcinomas have a dismal prognosis. The efficacy of systemic chemotherapy in these patients is negligible and often, in particular in patients with hepatocellular carcinomas, the toxicity of chemotherapy outweighs the potential palliative effect of antineoplastic agents. Gemcitabine is a new anticancer agent with a mild toxicity profile, which has demonstrated antineoplastic activity in many solid tumors. Therefore we investigated the effect of gemcitabine in patients with advanced nonresectable hepatocellular and cholangiocellular carcinomas in a phase II study. METHODOLOGY: Twenty-three patients with cholangiocellular carcinoma and 20 patients with hepatocellular carcinoma were enrolled into the study. Eighteen of the 20 patients with hepatocellular carcinomas had liver cirrhosis. Gemcitabine was administered once weekly over 30 min for 3 consecutive weeks out of every 4 weeks. Patients with cholangiocellular carcinomas received gemcitabine also in the forth week of the first cycle with no rest to the following cycle. Disease status was assessed every 4 weeks. RESULTS: Overall the regimen was well tolerated. The median number of gemcitabine administration was 15 (range, 3-37) in the group of patients with cholangiocellular carcinomas and 7.6 (range, 3-21) in the group of patients with hepatocellular carcinomas. In the group of patients with hepatocellular carcinomas thrombocytopenia was the most frequent side effect (30% grade 3/4). Among the patients with cholangiocellular carcinomas nausea and neutropenia were the most commonly observed side effects. The overall response rate of hepatocellular carcinomas was only 5% and chemotherapy generally did not improve the tumor symptoms of the patients in this group. In contrast, in the group of cholangiocellular carcinomas, seven patients achieved a partial response (overall response rate 30%). Eleven patients with cholangiocellular carcinomas revealed tumor symptoms before the onset of gemcitabine treatment. Seven of these patients developed a treatment related clinical benefit as defined as a relief of tumor symptoms or gain of weight. CONCLUSIONS: Our results indicate that the treatment of cholangiocarcinomas with gemcitabine is effective and should be further evaluated in phase III studies. In contrast, palliative chemotherapy with gemcitabine cannot be recommended in patients with hepatocellular carcinoma and liver cirrhosis.

Adult↗