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Biomedical subjects

S H Kaufmann

Publications and source records attributed to S H Kaufmann.

At least 37 records · Page 2Linked to original sources
PubMed2001

Clinical and biologic activity of the farnesyltransferase inhibitor R115777 in adults with refractory and relapsed acute leukemias: a phase 1 clinical-laboratory correlative trial.

R115777 is a nonpeptidomimetic enzyme-specific inhibitor of farnesyl protein transferase (FT) that was developed as a potential inhibitor of Ras protein signaling, with antitumor activity in preclinical models. This study was a phase 1 trial of orally administered R115777 in 35 adults with poor-risk acute leukemias. Cohorts of patients received R115777 at doses ranging from 100 mg twice daily (bid) to 1200 mg bid for up to 21 days. Dose-limiting toxicity occurred at 1200 mg bid, with central neurotoxicity evidenced by ataxia, confusion, and dysarthria. Non-dose-limiting toxicities included reversible nausea, renal insufficiency, polydipsia, paresthesias, and myelosuppression. R115777 inhibited FT activity at 300 mg bid and farnesylation of FT substrates lamin A and HDJ-2 at 600 mg bid. Extracellular signal-regulated kinase (ERK), an effector enzyme of Ras-mediated signaling, was detected in its phosphorylated (activated) form in 8 (36.4%) of 22 pretreatment marrows and became undetectable in 4 of those 8 after one cycle of treatment. Pharmacokinetics revealed a linear relationship between dose and maximum plasma concentration or area under the curve over 12 hours at all dose levels. Weekly marrow samples demonstrated that R115777 accumulated in bone marrow in a dose-dependent fashion, with large increases in marrow drug levels beginning at 600 mg bid and with sustained levels throughout drug administration. Clinical responses occurred in 10 (29%) of the 34 evaluable patients, including 2 complete remissions. Genomic analyses failed to detect N-ras gene mutations in any of the 35 leukemias. The results of this first clinical trial of a signal transduction inhibitor in patients with acute leukemias suggest that inhibitors of FT may have important clinical antileukemic activity. (Blood. 2001;97:3361-3369)

Adult↗
PubMed2001

Effect of P-glycoprotein on flavopiridol sensitivity.

Flavopiridol is the first potent inhibitor of cyclin-dependent kinases (CDKs) to enter clinical trials. Little is known about mechanisms of resistance to this agent. In order to determine whether P-glycoprotein (Pgp) might play a role in flavopiridol resistance, we examined flavopiridol sensitivity in a pair of Chinese hamster ovary cell lines differing with respect to level of Pgp expression. The IC(50)s of flavopiridol in parental AuxB1 (lower Pgp) and colchicine-selected CH(R)C5 (higher Pgp) cells were 90.2 +/- 6.6 nM and 117 +/- 2.3 nM, respectively (P< 0.01), suggesting that Pgp might have a modest effect on flavopiridol action. Consistent with this hypothesis, pretreatment with either quinidine or verapamil (inhibitors of Pgp-mediated transport) sensitized CH(R)C5 cells to the antiproliferative effects of flavopiridol. Because of concern that colony forming assays might not accurately reflect cytotoxicity, we also examined flavopiridol-treated cells by trypan blue staining and flow cytometry. These assays confirmed that flavopiridol was less toxic to cells expressing higher levels of Pgp. Further experiments revealed that flavopiridol inhibited the binding of [3H]-azidopine to Pgp in isolated membrane vesicles, but only at high concentrations. Collectively, these results identify flavopiridol as a weak substrate for Pgp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Loss of expression of a new member of the DNAJ protein family confers resistance to chemotherapeutic agents used in the treatment of ovarian cancer.

Differential display-PCR between ovarian tumor cell lines and short-term cultures of normal ovarian epithelial cell brushings was used to isolate a differentially expressed transcript and its corresponding gene. The gene, which mapped to 13q14.1, has partial homology in the DNAJ domain to a number of proteins with a similar domain and was designated as methylation-controlled J protein (MCJ). MCJ has the highest similarity to a functionally undefined protein from Caenorhabditis elegans. MCJ is expressed as a 1.2-kb transcript in several adult tissues, with testis showing the highest level of expression. Expression of MCJ was absent in three of seven ovarian cancer cell lines. Similarly, expression analysis using semiquantitative reverse transcription-PCR indicated that 12 of 18 primary ovarian tumors examined had either a complete absence or lower levels of expression of this gene. 5-Aza-2'-deoxycytidine treatment of the OV202 cell line induced MCJ expression in a dose-dependent manner, implicating methylation in this induction. Loss of heterozygosity and methylation-specific PCR analysis revealed that the loss of MCJ expression in primary tumors and cell lines was attributable to deletion of one allele and methylation of the other. To assess the potential functional significance of MCJ down-regulation, the sensitivity of parental (MCJ-nonexpressing) and MCJ-transfected OV167 cells to antineoplastic agents was evaluated. MCJ expression was associated with enhanced sensitivity to paclitaxel, topotecan, and cisplatin, suggesting that MCJ loss may play a role in de novo chemoresistance in ovarian carcinoma. These observations raise the possibility that MCJ loss may: (a) have potential prognostic significance in ovarian cancer; and (b) contribute to the malignant phenotype by conferring resistance to the most commonly used chemotherapeutic agents for ovarian cancer.

Amino Acid Sequence↗
PubMed2001

Contribution of MHC class I-dependent immune mechanisms induced by attenuated recombinant Salmonella typhimurium secreting superoxide dismutase to protection against murine listeriosis.

A recombinant (r)Salmonella typhimurium aroA strain secreting the naturally non-secreted superoxide dismutase (SOD) of Listeria monocytogenes controls murine listeriosis dependent on 'transporter associated with antigen processing' (TAP)-mediated immune mechanisms. TAP1-deficient mice (devoid of most CD8 T cells) vaccinated with this rSalmonella SODs strain succumbed to lethal L. monocytogenes challenge, whereas C57BL/6 mice were protected by this vaccine. Moreover, vaccination of H-2I-Abeta-deficient mice (lacking major histocompatibility class (MHC) II molecules and thus devoid of mature CD4 TCR-alphabeta cells), of TAP1-deficient as well as of beta2microglobulin-deficient mice (devoid of conventional CD8 T cells) with a sublethal dose of L. monocytogenes and subsequent challenge with rSalmonella control or SODs strain revealed contribution of both MHC class I- and MHC class II-dependent immune mechanisms to the control of secondary Salmonella infection. Finally, the clearance of rSalmonella SODs bacteria was achieved in TAP1-deficient animals vaccinated with L. monocytogenes. Our data suggest a role of TAP-dependent mechanisms in priming of protective immunity by rSalmonella micro-organisms secreting SOD.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

CD40 signaling converts a minimally immunogenic antigen into a potent vaccine against the intracellular pathogen Listeria monocytogenes.

Conventional vaccination strategies have failed for numerous pathogens, and the development of novel approaches to vaccine development is a major public health priority. Killed or subunit vaccines represent an attractive approach due to their safety, but they suffer from low immunogenicity and generally require adjuvants. In this study, the possibility of harnessing CD40 signaling for enhancing the immunogenicity of killed vaccines was investigated. Intravenous immunization of C57BL/6 mice with heat-killed Listeria monocytogenes (HKL) induced minimal immunity, but HKL administered together with an agonistic anti-CD40 mAb induced high levels of both CD4(+) and CD8(+) T cells capable of producing IFN-gamma following in vitro HKL stimulation. HKL/anti-CD40 vaccination elicited robust protection against subsequent Listeria challenge. Approximately 1000-fold fewer bacteria were detected in the liver and spleen of vaccinated mice, and vaccinated mice were also able to resist a normally lethal Listeria challenge. CD40-mediated adjuvant activity required endogenous IL-12 at the time of vaccination, and protection was mediated by both CD8(+) and CD4(+) T cells. Thus, CD40 signaling can deliver potent adjuvant activity for vaccination against intracellular pathogens and is particularly effective for pathogens requiring both CD4(+) and CD8(+) T cells for effective control.

Adjuvants, Immunologic↗
PubMed2001

Recombinant attenuated bacteria for the delivery of subunit vaccines.

Using attenuated intracellular bacteria as carriers, we have developed two different approaches for the delivery of subunit vaccines encoding heterologous antigens. The first system is based on the direct secretion of the heterologous antigens in Gram-negative bacteria via the hemolysin secretion system of Escherichia coli into either phagosome or cytosol of infected cells. The second approach is based on the transport of eukaryotic antigen expression vectors by intracellular bacteria like Listeria and Salmonella into the host cell and here, preferably, into the cytosolic compartment. After release of the plasmid DNA from the bacteria, the plasmid-encoded antigens can be expressed directly by the host cell. Finally, we combined both types of subunit vaccines in one live vector - we equipped Salmonella strains with a phagosomal escape function by utilization of the hemolysin secretion system and used this recombinant vaccine strain for the delivery of a eukaryotic antigen expression vector into the cytosol of macrophages.

Animals↗
PubMed2001

The HER tyrosine kinase inhibitor CI1033 enhances cytotoxicity of 7-ethyl-10-hydroxycamptothecin and topotecan by inhibiting breast cancer resistance protein-mediated drug efflux.

Because the activities of HER family members are elevated and/or aberrant in a variety of human neoplasms, these cell surface receptors are receiving increasing attention as potential therapeutic targets. In the present study, we examined the effect of combining the HER family tyrosine kinase inhibitor CI1033 (PD 183805) with the topoisomerase (topo) I poison 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan, in a number of different cell lines. Colony-forming assays revealed that the antiproliferative effects of simultaneous treatment with CI1033 and SN-38 were synergistic in T98G glioblastoma cells and HCT8 colorectal carcinoma cells, whereas sequential treatments were additive at best. In additional studies examining the mechanistic basis for these findings in T98G cells, immunoblotting revealed that the inhibitory effects of CI1033 on epidermal growth factor receptor autophosphorylation were unaffected by SN-38. Likewise, CI1033 had no effect on topo I polypeptide levels, localization, or activity. Nonetheless, CI1033 markedly enhanced the number of covalent topo I-DNA complexes stabilized by SN-38 or the related agent topotecan (TPT). Analysis of intracellular SN-38 levels by high-performance liquid chromatography and intracellular TPT levels by flow microfluorometry revealed that CI1033 increased the steady-state accumulation of SN-38 and TPT by 9.4 +/- 1.9- and 1.8 +/- 0.2-fold, respectively. Further evaluation revealed that the initial rate of TPT uptake was unaffected by CI1033, whereas the rate of efflux was markedly diminished. Additional studies demonstrated that T98G and HCT8 cells express the breast cancer resistance protein (BCRP), a recently cloned ATP binding cassette transporter. Moreover, CI1033 enhanced the uptake and cytotoxicity of SN-38 and TPT in cells transfected with BCRP but not empty vector. Conversely, CI1033 accumulation was diminished in cells expressing BCRP, suggesting that CI1033 is a substrate for this efflux pump. These results indicate that CI1033 can modulate the accumulation and subsequent cytotoxicity of two widely used topo I poisons in cells that have no history of previous exposure to these agents.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2001

MHC class Ia-restricted T cells partially account for beta2-microglobulin-dependent resistance to Mycobacterium tuberculosis.

Recent studies have highlighted the heterogeneous nature of the CD8(+) T cell response during human Mycobacterium tuberculosis infection; MHC class Ia, MHC class Ib and CD1 have all been identified as significant restriction elements. Here we have attempted to define the role of MHC class Ia in resistance to M. tuberculosis infection in mice. The course of M. tuberculosis infection in mice deficient in a single MHC class Ia molecule, either H2-K(b) or H2-D(b), was essentially identical to that observed in wild-type mice. In contrast, mice fully deficient in MHC class Ia molecules (H2-K(b) / H2-D(b) double knockout mice) were substantially more susceptible to M. tuberculosis infection. However, the double knockout mice were not as susceptible as beta 2-microglobulin-deficient mice, which have a broader phenotypic deficit. Thus, antigen presentation via MHC class Ia is an important component in resistance to M. tuberculosis, but its absence only partially accounts for the increased susceptibility of beta 2-microglobulin-deficient mice.

Animals↗
PubMed2001

Identification of proteins from Mycobacterium tuberculosis missing in attenuated Mycobacterium bovis BCG strains.

A proteome approach, combining high-resolution two-dimensional electrophoresis (2-DE) with mass spectrometry, was used to compare the cellular protein composition of two virulent strains of Mycobacterium tuberculosis with two attenuated strains of Mycobacterium bovis Bacillus Calmette-Guerin (BCG), in order to identify unique proteins of these strains. Emphasis was given to the identification of M. tuberculosis specific proteins, because we consider these proteins to represent putative virulence factors and interesting candidates for vaccination and diagnosis of tuberculosis. The genome of M. tuberculosis strain H37Rv comprises nearly 4000 predicted open reading frames. In contrast, the separation of proteins from whole mycobacterial cells by 2-DE resulted in silver-stained patterns comprising about 1800 distinct protein spots. Amongst these, 96 spots were exclusively detected either in the virulent (56 spots) or in the attenuated (40 spots) mycobacterial strains. Fifty-three of these spots were analyzed by mass spectrometry, of which 41 were identified, including 32 M. tuberculosis specific spots. Twelve M. tuberculosis specific spots were identified as proteins, encoded by genes previously reported to be deleted in M. bovis BCG. The remaining 20 spots unique for M. tuberculosis were identified as proteins encoded by genes that are not known to be missing in M. bovis BCG.

Bacterial Proteins↗
PubMed2001

Identification of acidic, low molecular mass proteins of Mycobacterium tuberculosis strain H37Rv by matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry.

Matrix-assisted laser desorption/ionization-mass spectrometry peptide mass mapping and nano-electrospray ionization tandem mass spectrometry were used to identify acidic, low molecular mass proteins of Mycobacterium tuberculosis strain H37Rv. Proteins were extracted from whole cell lysates of mycobacteria, separated by high resolution two-dimensional electrophoresis (2-DE) and analysed by mass spectrometry (MS). Silver-stained 2-DE patterns resolved about 1800 distinct protein species, 190 of which had an observed isoelectric point and molecular mass in the range of pH 4 to 6 and 6 to 15 kDa, respectively. Seventy-six spots from this range were excised from Coomassie Brilliant Blue G250-stained gels and analysed by MS, from which 72 were identified. These spots were shown to represent products of as many as 50 different protein-coding genes. Ten genes gave rise to more than one protein species. Eleven spots contained more than one protein. The present study led to the identification of 15 mycobacterial proteins with assigned putative functions, 28 conserved hypothetical proteins and one unknown protein. Most proteins of the latter two groups had previously been predicted at the DNA level only. Six additional spots were shown to comprise proteins encoded by open reading frames that have not been predicted for M. tuberculosis H37Rv by genomic investigations.

Antigens, Bacterial↗
PubMed2001

Human INCENP colocalizes with the Aurora-B/AIRK2 kinase on chromosomes and is overexpressed in tumour cells.

The inner centromere protein (INCENP), which has previously been described in chicken, frog and mouse, is required for correct chromosome segregation and cytokinesis. We have identified the human INCENP gene by library screening and reverse transcription-polymerase chain reaction (RT-PCR) and localized it to chromosomal region 11q12. HsINCENP is a single-copy gene that consists of 17 exons and covers 25 kb of genomic DNA. The gene is expressed at highest levels in the colon, testis and prostate, consistent with its likely role in cell proliferation. HsINCENP encodes a highly basic protein of 915 amino acids that localizes to metaphase chromosomes and to the mitotic spindle and equatorial cortex at anaphase. Recently we showed that INCENP is stockpiled in a complex with the Aurora-B/XAIRK2 kinase in Xenopus eggs. Here we demonstrate that, consistent with such an interaction, the two proteins colocalize on human metaphase chromosomes. Levels of Aurora-B are increased in several human cancers, and we show here that HsINCENP protein levels are also significantly increased in several colorectal cancer cell lines.

Amino Acid Sequence↗
PubMed2001

Immune responses to intracellular bacteria.

The multifaceted dialogue between intracellular bacteria and the mammalian host continues to be an exciting issue from both the scientific and public-health viewpoint. The recent year has witnessed some particularly impressive progress in knowledge about the two major culprits affecting the health of mankind, Mycobacterium tuberculosis and Salmonella typhi - the causative agents of tuberculosis and typhoid fever.

Adaptation, Physiological↗
PubMed2001

Programmed cell death: alive and well in the new millennium.

Research performed over the past decade has transformed apoptosis from a distinctive form of cell death known only by its characteristic morphology and genomic destruction to an increasingly well understood cellular disassembly pathway remarkable for its complex and multifaceted regulation. Here, we summarize current understanding of apoptotic events, note recent advances in this field and identify questions that might help guide research in the coming years.

Animals↗
PubMed2001

From evil to good: a cytolysin in vaccine development.

Current vaccination strategies mainly target antigens into the phagosomal, major histocompatibility complex class II antigen-processing pathway and thus lead predominantly to humoral immune responses. The elicitation of cytotoxic T-cell responses instead requires introduction of antigens into the cytosol of professional antigen-presenting cells (APCs). The intracellular bacterium Listeria monocytogenes gains access to the host cell cytosol by means of a cytolysin, listeriolysin O. Vaccine researchers have successfully employed listeriolysin in novel vaccination approaches to provide access to the cytosol of professional APCs for purified protein antigens, attenuated bacterial vaccine strains, DNA vaccines and liposome contents.

Animals↗
PubMed2001

Prospects for better tuberculosis vaccines.

Tuberculosis remains one of the top three infectious disease killers. Treatment is long and expensive and drug resistant strains of Mycobacterium tuberculosis are already on the rise. The current vaccine, BCG, is ineffective in parts of the world where the disease is most widespread and therefore the search for a novel, more effective vaccine is paramount. In this review we discuss the current state of vaccine research, including the identification of candidate antigens and the current methods used for their evaluation.

Animals↗
PubMed2001

Phase I trial of gemcitabine and CPT-11 given weekly for four weeks every six weeks.

BACKGROUND: Our previous studies have shown that the in vitro cytotoxicity of gemcitabine and SN-38, the active metabolite of irinotecan (CPT-11), is synergistic in human tumor cell lines. PATIENTS AND METHODS: Twenty-four patients with solid tumors, refractory to standard chemotherapy or for whom no effective therapy existed (age range 31-74; 7 female, 17 male; ECOG PS 0 = 12, 1 = 11, 2 = 1), received gemcitabine and CPT-11 weekly for four weeks out of every six weeks. Fifty courses of treatment (median 2, range 1-8) were given through five dose levels of gemcitabine/CPT-11 (600/75, 800/75, 800/100, 1000/100, 1000/125 mg/m2). RESULTS: Grade 3 and 4 neutropenia occurred in eight and two patients, respectively. Grade 3 and 4 thrombocytopenia occurred in one and three patients, respectively. Hematologic toxicity resulted in > or = 2 missed doses of treatment in two out of six patients and was therefore dose limiting at gemcitabine 1000 mg/m2 and CPT-11 125 mg/m2. Grade 3 and 4 diarrhea occurred in two and one patients, respectively. Other moderate non-hematologic toxicities included alopecia, anorexia, fatigue, nausea, vomiting, and weight loss. CONCLUSIONS: The maximum tolerated dose for this study recommended for phase II testing is gemcitabine 1000 mg/m2 and CPT-11 100 mg/m2. A partial response was seen in transitional cell carcinoma.

Adult↗
PubMed2001

How can immunology contribute to the control of tuberculosis?

Tuberculosis poses a significant threat to mankind. Multidrug-resistant strains are on the rise, and Mycobacterium tuberculosis infection is often associated with human immunodeficiency virus infection. Satisfactory control of tuberculosis can only be achieved using a highly efficacious vaccine. Tuberculosis is particularly challenging for the immune system. The intracellular location of the pathogen shields it from antibodies, and a variety of T-cell subpopulations must be activated to challenge the bacterium's resistance to antibacterial defence mechanisms. A clear understanding of the immune responses that control the pathogen will be important for achieving optimal immunity, and information provided by functional genome analysis of M. tuberculosis will be vital in the design of a future vaccine.

Animals↗