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Biomedical subjects

J W Freeman

Publications and source records attributed to J W Freeman.

At least 19 recordsLinked to original sources
PubMed2004

NF-kappa B inhibition markedly enhances sensitivity of resistant breast cancer tumor cells to tamoxifen.

Studies show that high Akt activity in breast carcinoma is associated with endocrine therapy resistance. Breast cancer cell lines expressing a constitutively active Akt are able to proliferate under reduced estrogen conditions, and are resistant to the growth inhibitory effects of tamoxifen. Understanding the targets of Akt signaling mediating tamoxifen resistance is of clinical significance. One possible target is nuclear factor kappa B (NF-kappa B), a transcription factor that plays a critical role in resistance to apoptosis and the induction of angiogenesis and invasion. In the present study, we found that Akt activity correlated with phosphorylation of I kappa B (the negative regulator of NF-kappa B), NF-kappa B DNA binding and tamoxifen resistance in vivo. Importantly, we found that co-treatment with the NF-kappa B inhibitor, parthenolide, or overexpression of I kappa B superrepressor restored tamoxifen sensitivity to our refractory Akt MCF-7 cells. These data suggest that activation of NF-kappa B via the PI3K/Akt signaling pathway may be a significant mechanism for development of endocrine therapy resistance in breast cancer, and that inhibition of NF-kappa B may be an effective treatment strategy to limit the progression of this disease.

Antineoplastic Agents, Hormonal↗
PubMed2001

Aberrant expression and activation of insulin-like growth factor-1 receptor (IGF-1R) are mediated by an induction of IGF-1R promoter activity and stabilization of IGF-1R mRNA and contributes to growth factor independence and increased survival of the pancreatic cancer cell line MIA PaCa-2.

In the present study we investigated the mechanisms responsible for and the biological consequences of the constitutive activation of the insulin-like growth factor-1 receptor (IGF-1R) in the MIA PaCa-2 cells. An aberrant increase in the expression and activation of the IGF-1R was observed during the transition of growth states from exponential to quiescent. The increase in IGF-1R expression is preceded by an increase in IGF-1R mRNA transcript and is associated with an increase in the IGF-1R promoter activity. Inhibition of de novo transcription by actinomycin D increased the stability of IGF-1R mRNA in exponentially growing cells, thereby increasing the expression of IGF-1R to a level similar to that seen in quiescent cells. Increased IGF-1R signaling mediated the growth factor independence of quiescent MIA PaCa-2 cells through the constitutive activation of mitogen-activated protein kinase (MAPK). Exogenous IGF-1 increased cell proliferation and activated MAPK and AKT signaling pathways. The resistance of cells to apoptosis by IGF-1R signaling was mediated through MAPK and phosphatidylinositol 3-kinase (PI3K) pathways and a yet unidentified pathway(s). Thus, aberrant regulation of IGF-1R signaling is required for resistance to apoptosis and growth factor independence of MIA PaCa-2 cells. This likely protects cells from unfavorable conditions and allows cells to rapidly re-enter the cell cycle when conditions are favorable.

Apoptosis↗
PubMed2001

Effect of chemopreventive agents on DNA adduction induced by the potent mammary carcinogen dibenzo[a,l]pyrene in the human breast cells MCF-7.

Over 1500 structurally diverse chemicals have been identified which have potential cancer chemopreventive properties. The efficacy and mechanisms of this growing list of chemoprotective agents may be studied using short-term bioassays that employ relevant end-points of the carcinogenic process. In this study, we have examined the effects of eight potential chemopreventive agents, N-acetylcysteine (NAC), benzylisocyanate (BIC), chlorophyllin, curcumin, 1,2-dithiole-3-thione (D3T), ellagic acid, genistein, and oltipraz, on DNA adduction of the potent mammary carcinogen dibenzo[a,l]pyrene (DBP) using the human breast cell line MCF-7. Bioactivation of DBP by MCF-7 cells resulted in the formation of one predominant (55%) dA-derived and several other dA- or dG-derived DNA adducts. Three test agents, oltipraz, D3T, and chlorophyllin substantially (>65%) inhibited DBP-DNA adduction at the highest dose tested (30 microM). These agents also significantly inhibited DBP adduct levels at a lower dose of 15 microM, while oltipraz was effective even at the lowest dose of 5 microM. Two other agents, genistein and ellagic acid were moderate (45%) DBP-DNA adduct inhibitors at the highest dose tested, while NAC, curcumin, and BIC were ineffective. These studies indicate that the MCF-7 cell line is an applicable model to study the efficacy of cancer chemopreventive agents in a human setting. Moreover, this model may also provide information regarding the effect of the test agents on carcinogen bioactivation and detoxification enzymes.

Anticarcinogenic Agents↗
PubMed2001

Reversion of transcriptional repression of Sp1 by 5 aza-2' deoxycytidine restores TGF-beta type II receptor expression in the pancreatic cancer cell line MIA PaCa-2.

The pancreatic cancer cell line, MIA PaCa-2 is not responsive to transforming growth factor beta (TGF-beta) because of a lack of expression of the TGF-beta type II receptor (RII). We show that the lack of RII expression is caused by a deficit of the transcription factor Sp1. Nuclear run-off assays and Western immunoblot showed low levels of transcription and protein levels of Sp1, respectively. Treatment of MIA PaCa-2 cells with the DNA methyl transferase inhibitor, 5-aza-2'-deoxycytidine, resulted in an increase in the rate of Sp1 transcription, in Sp1 protein expression, and in the binding of Sp1 to the RII promoter. Ectopic expression of Sp1 cDNA in MIA PaCa-2 cells led to an increase in RII promoter-chloramphenicol acetyltransferase activity and RII expression. Expression of Sp1 cDNA also caused a reduction in both growth and clonogenicity that was associated with restoration of responsiveness to TGF-beta. Conversely, cells that express RII (BxPC-3 and MIA PaCa-2 Sp1 transfectants) when treated with mithramycin, an inhibitor of Sp1 binding, showed a reduction in RII mRNA expression. The reduction of RII mRNA was attributed to a decrease in RII promoter-chloramphenicol acetyltransferase activity that was associated with a decrease in Sp1 binding to the RII promoter. These data indicate that transcriptional repression of the Sp1 gene in MIA PaCa-2 cells plays a role in the transcriptional inactivation of the RII gene and thus lack of responsiveness to TGF-beta.

Antibiotics, Antineoplastic↗
PubMed2001

Molecular basis for elastic energy storage in mineralized tendon.

Animals store elastic energy in leg and foot tendons during locomotion. In the turkey, much of the locomotive force generated by the gastrocnemius muscle is stored as elastic energy during tendon deformation. Little energy storage occurs within the muscle. During growth of some avians, including the turkey, leg tendons mineralize in the portions distal to the attached muscle and show increased tensile strength and modulus as a result. The purpose of this study is to test the hypothesis that the degree of elastic energy storage in mineralizing turkey tendon is directly related to the tendon mineral content. To test this hypothesis, the stress-strain behavior of tendons was separated into elastic and viscous components. Both the elastic spring constant and the elastic energy stored, calculated up to a strain of 20%, were found to be proportional to tendon mineral content. It is concluded that mineralization is an efficient means for increasing the amount of elastic energy storage that is required for increased load-bearing ability needed for locomotion of adult birds. Examination of molecular models of the hole region, where mineralization is initiated within the collagen fibril, leads to the hypothesis that elastic energy is stored in the tendon by direct stretching of the flexible regions. Flexible regions within the collagen molecule fall within the positively stained bands of the collagen D period. It is proposed that mineralization increases the stored elastic energy by preventing flexible regions within the positively stained bands from stretching. These observations suggest that mineralization begins in the hole region due to the large number of charged amino acid residues found in the d and e bands.

Animals↗
PubMed2001

Viscoelastic properties of human skin and processed dermis.

BACKGROUND/AIMS: The purpose of this work is to attempt to determine the elastic spring constant for collagen and elastic fibers (elastin) in skin and to determine if the values of these elastic constants are similar to those reported for other tissues. METHODS: We studied the viscoelastic mechanical properties of human skin and dermis by measuring the incremental stress-strain behavior. Elastic stress-strain curves were used to obtain the elastic spring constant of elastin and collagen while the collagen fibril length was obtained from the slope of viscous stress-strain curves. RESULTS: Our results suggest that the elastic spring constant for elastin is about 4.0 MPa while that for collagen is about 4.4 GPa. The former value is similar to that calculated for ligamentum nuchae while the latter value is about 70% of the value found for tendon and self-assembled type I collagen fibers. The differences between the elastic constants for collagen molecules in tendon and skin is hypothesized to reflect the higher molecular tilt angle and lower D period found in skin compared to tendon as well as a shorter fibril length. CONCLUSION: The differences in the collagen types present in skin and tendon may influence collagen self-assembly and the resulting viscoelastic properties.

Aged↗
PubMed2001

Morbidity and mortality associated with large-bore percutaneous venovenous bypass cannulation for 312 orthotopic liver transplantations.

The aim of this study is to establish the incidence of serious morbidity and mortality associated with the placement of large-bore (18 to 20 F) percutaneous bypass cannulae for venovenous bypass (VVBP) during orthotopic liver transplantation (OLT). This technique has been reported to be rapid, simple, and safe. We reviewed the case notes of 312 patients who underwent OLT in our center using this technique. We describe 4 cases of serious morbidity (incidence, 1.28%) and 1 death (incidence, 0.32%) related directly to percutaneous placement of the bypass cannula. We conclude that percutaneous cannula placement for VVBP during OLT has the potential for life-threatening complications, and this must be considered when electing to use this technique. When percutaneous cannulae are to be used, we recommend the use of the right internal jugular vein for return cannulation and the use of ultrasound guidance, particularly in those patients in whom cannulation is predictably difficult.

Adult↗
PubMed2001

Risk taking.

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Decision Making↗
PubMed2000

Characterization of a newly established human pancreatic carcinoma cell line, UK Pan-1.

BACKGROUND: A highly tumorigenic cell line designated as UK Pan-1 was established in a surgically removed human pancreatic adenocarcinoma and characterized as having many of the genotypic and phenotypic alterations commonly found in pancreatic tumors. METHODS: The cell line was characterized by its morphology, growth rate in monolayer culture and soft agar, tumorigenicity in nude mice, and chromosomal analysis. Furthermore, the status of p53, Ki-ras mutation and transforming growth factor (TGF)-/receptor expression were determined. The characteristics of UK Pan-1 were compared with those of other commonly used pancreatic carcinoma cell lines. RESULTS: Quiescent UK Pan-1 cells could be stimulated to proliferate in growth factor free nutrient media, indicating a growth factor independent phenotype. UK Pan- 1 cells grew in soft agar and rapidly formed tumors in nude mice. This cell line possesses a mutation at codon 12 of the c-Ki-ras-2 gene that is commonly found in pancreatic carcinoma. Fluorescence in situ hybridization showed that two alleles of p53 tumor suppressor gene were present in UK Pan-1. However, sequencing analysis revealed a mutation in one allele at exon 8, codon 273 (G to A; Arg to His). Additional growth assays indicated that the cell line was insensitive to negative growth regulation induced by exogenous TGF-beta. Molecular analysis of the TGF-beta signaling pathway showed that UK Pan-1 did not express appreciable levels of the TGF-beta receptor type I, II, or III mRNAs, but did express DPC4 mRNA. Karyotype analysis revealed an 18q21 deletion indicating a possible loss of heterozygosity for DPC4, as well as other chromosomal deletions and rearrangements. CONCLUSIONS: This study indicates that UK Pan-1 is a highly tumorigenic cell line possessing a molecularly complex pattern of mutations that may be used as a model to further the understanding of the mechanisms responsible for the development of pancreatic carcinoma.

Adenocarcinoma↗
PubMed2000

Being there.

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Humans↗
PubMed2000

By any other name.

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Ethics, Medical↗
PubMed1999

Outcome of liver retransplantation in children.

Irreversible liver graft failure is a life-threatening complication. We reviewed the first 200 pediatric liver transplantations in Birmingham. Forty-one children developed primary graft failure, 9 of whom developed secondary graft failure. The main indications for graft failure were primary nonfunction (PRNF; 8 patients), vascular complications (VASC; 23 patients), and chronic rejection (CHRE; 19 patients). Thirty-two children underwent retransplantation (ReTx) (21 children received reduced grafts; 11 children, whole hepatic grafts). Patient survival was significantly worse for retransplant recipients compared with children receiving a single graft (63% v 76. 5% actuarial patient survival at 1 year; P <.05). Primary graft 1-year actuarial survival was 74% in first grafts compared with 47% for regrafts (P <.05), but improved with time. The graft 1-year survival rate was 55% for whole grafts and 45% for reduced and/or split grafts in the first 100 grafts compared with 83% and 66% in the second 100 grafts, respectively (P <.01). Emergency ReTx within a month of transplantation was associated with more complications and a worse outcome (1-year survival rate, 37%) compared with patients who underwent ReTx later (1-year survival rate, 72%; P <. 01). The incidence of primary graft failure decreased from 33% in the first 100 grafts to 16% in the second 100 grafts (P <.01), as did the incidence of PRNF, which decreased from 8% to 0% (P <.05). Although the rates of graft failure from VASC decreased from 15% to 8% (P =.2) and CHRE decreased from 11% to 8% (P =.6), neither reached statistical significance. The improved results overall are because of advances in surgical techniques, intensive care management, and graft preservation and refinements in immunosuppression. We conclude that ReTx for a child with primary graft failure is justified.

Adolescent↗
PubMed1999

Practical wisdom.

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Complementary Therapies↗
PubMed1999

Case report: hemiballismus with unusual MRI findings.

A 90-year-old male experienced the abrupt onset of hemiballismus. He had an unusual MRI picture with bright signal in the right basal ganglia on T1-weighted imaging with no significant signal abnormality identified on T2-weighted imaging. This appearance has been described in diabetic patients who sustain ischemia in the basal ganglia region and prior cases are cited.

Aged↗
PubMed1999

Wishful thinking.

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Attitude to Health↗