Dual anticancer activity of 8-Cl-cAMP: inhibition of cell proliferation and induction of apoptotic cell death

8-Cl-cAMP induces apoptotic cell death in human cancer cells. To look at this more closely, we examined the changes in the levels of Bcl-2 family proteins during 8-Cl-cAMP-induced apoptosis of SH-SY5Y human neuroblastoma cells. Following the treatment with 8-Cl-cAMP, Bcl-2 was transiently down-regulated and Bad was increased continuously up to day 5. In addition, overexpression of Bcl-2 efficiently blocked the 8-Cl-cAMP-induced apoptosis, suggesting Bcl-2 family proteins may be involved in the 8-Cl-cAMP-induced apoptosis. The contribution of the apoptotic cell death and the inhibition of cell proliferation in the 8-Cl-cAMP-induced growth inhibition was closely monitored in the Bcl-2-overexpressing cells. Though the apoptosis was reduced significantly, no significant difference was observed in the inhibition of cell proliferation up to day 2 of 8-Cl-cAMP treatment. These results suggest that 8-Cl-cAMP exerts anticancer activity by two distinct mechanisms, i.e. , through the inhibition of cell proliferation as well as the induction of apoptosis. Supporting this notion was the observations that (1) suppression of apoptosis by zVAD did not abrogate 8-Cl-cAMP-induced inhibition of cell proliferation, and (2) 8-Cl-cAMP did not show additive inhibition of cell proliferation in RIIbeta-overexpressing cells.

Molecular design of novel metal-binding oligomeric human metallothioneins

Genes for dimeric and tetrameric human metallothionein (hMT) were designed and successfully overexpressed in Escherichia coli to generate functional oligomeric hMTs. An hMT synthesized with prokaryotic codons, a linker encoding a gly-gly-gly tripeptide, and Met-deficient hMT-II was ligated to create a dimeric hMT, from which a tetrameric hMT was then constructed. The increased molecular size of the constructs resulted in improved stability and productivity in E. coli. The oligomeric proteins formed inclusion bodies which were dissolved with dithiothreitol, and the purified apometallothioneins were reconstituted with Cd or Zn ions in a reducing condition. The oligomeric hMT proteins incubated with Cd ions showed a typical Cd-thiolate absorbance peak at 245-255 nm. The dimeric and tetrameric hMT proteins exhibited both Cd and Zn binding activities that were respectively two and four times higher than those of the hMT-II monomer protein. These novel oligomeric hMTs may be useful in bioremediation for heavy metals.

Indirect signs of anterior cruciate ligament injury on SPET: comparison with MRI and arthroscopy

Indirect signs of anterior cruciate ligament (ACL) injury on magnetic resonance imaging (MRI) include bony contusions in the lateral femoral condyle and the posterior portion of the lateral tibial plateau. This study was undertaken to assess the value of single photon emission tomography (SPET) in the diagnosis of ACL injury by examining the uptake pattern in the distal femur and the proximal tibia. Thirty-five patients were examined using SPET, MRI and arthroscopy. Seventeen patients were found to have ACL tears on arthroscopy. The duration of symptoms was 4 days to 10 years (mean 26.4 months). MRI and SPET images were analysed retrospectively without information from arthroscopic examination. Radionuclide uptake in the lateral femoral condyle and the posterior lateral tibial plateau was considered an indirect sign of ACL injury on SPET. We evaluated the diagnostic value of indirect signs of ACL injury obtained on SPET by comparing these findings with arthroscopic and MRI results. Fifteen of 17 patients with ACL injury showed indirect signs on SPET. The sensitivity, specificity, positive predictive value and negative predictive value for indirect signs of ACL injury were 88%, 56%, 65% and 83% on SPET and 59%, 94%, 91% and 71% on MRI, respectively. However, despite the higher sensitivity of indirect signs on SPET than on MRI, the overall diagnostic value of MRI is better than that of SPET. In the clinical setting, indirect signs of ACL injury may be of value in interpreting incidental findings on SPET.

Epithelial cell-specific laminin 5 is required for survival of early thymocytes

The gene LamC2 encoding the gamma2 chain of laminin 5, an epithelial cell-specific extracellular matrix protein, was identified in a PCR-based subtracted cDNA library from mouse thymic stromal cells. The mRNA existed in two alternative forms (5.1 and 2.4 kb). The full-length message was highly expressed in SCID thymus and in a nurse cell line, but not in other thymic epithelial cell lines, while the short form was more widely expressed. In situ hybridization and immunohistochemical staining revealed laminin 5 expression mostly in the subcapsular region of the adult thymus. Addition to fetal thymic organ cultures of a cell adhesion-blocking mAb to the alpha3 chain of laminin 5 interrupted T cell development. There was a 40% reduction in the total yield of thymocytes, and the most profound decrease (75-90%) was seen in the CD25+CD44+ and CD25+CD44-subsets of the CD4-CD8- double negative fraction. Most of the surviving double negative thymocytes expressed Sca-1, and there were significant increases in the number of cells with CD69 expression and in the fraction of annexin V-stained cells. None of these changes were observed with a nonblocking anti-laminin alpha3 chain mAb. These results suggest that the interaction between double negative thymoctyes and laminin 5 made by subcapsular epithelial cells is required for the survival and differentiation of mouse thymocytes.

Imposex in the rock shell, Thais clavigera, as evidence of organotin contamination in the marine environment of Korea

Imposex was measured in the rock shell, Thais clavigera, from the coast of the Korean peninsula. Frequency of imposex was 0% at two reference sites, but at 47 out of 61 sites, frequency of imposex was recorded as 100%. The degree of imposex was relatively high at the sites near a harbor and a shipyard. Tributyltin (TBT) and triphenyltin (TPT) concentrations in T. clavigera ranged from 5 to 508 ng/g and from 3 to 2460 ng/g, respectively. A significant positive relationship was found between degree of imposex and organotin concentration, whereas a significant negative relationship was obtained between female-to-male sex ratio and the degree of imposex. During a field transplantation of T. clavigera from a pristine area to a port, TBT and TPT were accumulated in T. clavigera, and imposex was induced. T. clavigera shows considerable potential as a bioindicator species of the adverse effects of TBT and TPT contamination.

Genetic variations of the hepatic lipase gene in Korean patients with coronary artery disease

OBJECTIVES

To investigate the association between the HL gene (LIPC) polymorphism, plasma lipid levels and coronary artery disease (CAD).

DESIGN AND METHODS

One hundred thirty-seven subjects with CAD and 124 age-matched controls were examined by polymerase chain reaction (PCR). The PCR products were analyzed for LIPC genotyping by enzyme digestion.

RESULTS

The allele frequencies of the three polymorphisms in the LIPC gene were not significantly different between the controls and CAD patients. The + allele of the -514 promoter polymorphism was associated with higher total cholesterol (p = 0.05), apolipoprotein (apo) AI (p = 0.04) levels in the men of the normal group, and the apoB level (p = 0.03) in the women of the CAD group without allele effect. The allele frequencies of the -250 and -514 promoter polymorphisms of Koreans were significantly different from those of the white and African American populations studied (p < 0.05).

CONCLUSIONS

The -514 promoter polymorphism may fluctuate on the lipid levels due to linkage disequilibria with other polymorphisms of the LIPC gene or nearby genes. The difference of the -250 promoter allele frequencies among the different populations may partially explain the variation of the HDL levels in ethnic groups. To elucidate the more exact associations of LIPC polymorphism with the plasma lipid levels, the precise biochemical mechanisms of the LIPC alleles are required.

Narrow internal auditory canal syndrome: parasaggital reconstruction

Narrow internal auditory canal (IAC) syndrome is a malformation of the temporal bone, that is defined as an IAC diameter of only 1-2 mm on high-resolution computed tomographic scans (HRCT). This syndrome is known to be caused by the absence (aplasia or hypoplasia) of the vestibulocochlear nerve. We present a case of unilateral narrow IAC syndrome which was diagnosed by HRCT. The aplasia of the vestibulocochlear nerve was confirmed using parasigittal reconstruction magnetic resonance image (MRI). The IAC was composed of two separate canals, one of which contained a facial nerve and the other was empty with aplasia of the vestibulocochlear nerve.

Remnant-like particle cholesterol levels in Korean patients with coronary artery disease and non-insulin dependent diabetes mellitus

Several studies have provided evidence that the remnants of lipoproteins may be the atherogenic components of triglyceride-rich lipoproteins. The purpose of this study was to investigate whether the remnant-like particle cholesterol (RLP-C) is an independent risk factor for coronary artery disease (CAD) and non-insulin dependent diabetes mellitus (NIDDM) in the Korean population and to explore the relationship between RLP-C and other biochemical markers as well as the apolipoprotein (apo) E genotypes. Lipid and lipoproteins including RLP-C and apo E genotypes were analyzed in 98 normal adults (control group), 68 patients with CAD (CAD group), 88 patients with NIDDM (DM group), and 19 patients with both CAD and NDDM (CAD + DM group). RLP-C levels were significantly higher in the DM (p < 0.0001), CAD (p = 0.0012) and the CAD + DM groups (p = 0.0184) than in the controls. To determine which variable could discriminate most effectively and independently among the different groups, stepwise linear discriminant analysis was performed for all the variables that showed p < 0.15 by univariate analysis. RLP-C was selected as an independent discriminator between the control and patient groups. RLP-C levels showed a strong positive correlation with trigylceride levels in the control, CAD and DM groups (r = 0.783, r = 0.610 and r = 0.746, respectively). In overall groups, apo epsilon4 and epsilon2 carrier genotypes showed a significant increase in RLP-C levels compared with epsilon3/3 wild-type (p = 0.0085). After adjusting for the effect of apo E genotypes, a significant increase of the RLP-C levels in the disease groups remained. In conclusion, RLP-C was determined to be an independent risk factor in Korean patients with CAD and NIDDM and showed a strong correlation with triglyceride levels. We suggest that the increased cardiovascular risk associated with the epsilon4 and epsilon2 allele may be mediated by more atherogenic RLP-C.

Fission yeast hrp1, a chromodomain ATPase, is required for proper chromosome segregation and its overexpression interferes with chromatin condensation

Hrp1 of Schizosaccharomyces pombe is a member of the CHD protein family, characterized by a chromodomain, a Myb-like telobox-related DNA-binding domain and a SNF2-related helicase/ATPase domain. CHD proteins are thought to be required for modification of the chromatin structure in transcription, but the exact roles of CHD proteins are not known. Here we examine the sub-cellular localization and biochemical activity of Hrp1 and the phenotypes of hrp1 Delta and Hrp1-overexpressing strains. Fluorescence microscopy revealed that Hrp1 protein is targeted to the nucleus. We found that Hrp1 exhibited DNA-dependent ATPase activity, stimulated by both single- and double-stranded DNA. Overexpression of Hrp1 caused slow cell growth accompanied by defective chromosome condensation in anaphase resulting in a 'cut' (celluntimelytorn) phenotype and chromosome loss. The hrp1 Delta mutation also caused abnormal anaphase and mini-chromosome loss phenotypes. Electron micrographs demonstrated that aberrantly shaped nucleoli appeared in Hrp1-overexpressing cells. Therefore, these results suggest that Hrp1 may play a role in mitotic chromosome segregation and maintenance of chromatin structure by utilizing the energy from ATP hydrolysis.

Retinoid receptors and the induction of apoptosis in canine osteosarcoma cells

Retinoids, all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid (9-cis-RA), induced morphological changes and apoptosis-like cell death characterized by cell shrinkage, chromatin condensation and nuclear disintegration in three canine osteosarcoma cells, OOS, HOS and POS, at a concentration of 10(-5) M. Both retinoid receptors, RARs and RXRs, were identified in these cells. 9-cis-RA bound to both the RXRs and the RARs, whereas ATRA bound to only the RARs in these cells. Those results indicate that the induction of apoptosis in canine osteosarcoma cells may be mediated by the specific control of RARs and RXRs.

Plasminogen activator inhibitor-1 4G/5G promoter polymorphism and coagulation factor VII Arg353-->Gln polymorphism in Korean patients with coronary artery disease

An increased risk for arterial thrombosis is associated with high plasma levels of coagulation and fibrinolytic factors such as PAI-1 and FVII. In this study, the 4G/5G polymorphism in the promoter of PAI-1 gene and Arg353-->Gln polymorphism in the FVII gene were analysed in 139 normal adults and 158 patients with coronary artery disease (CAD), and their association with plasma lipid traits was investigated. There were no significant differences in the allele frequencies of PAI-1 and FVII polymorphisms between control and patient groups. The allelic distributions of both polymorphisms in Koreans were similar to those in Japanese but significantly different from those in Caucasians. In the CAD group, the 4G homozygotes of PAI-1 polymorphism showed significantly higher levels of total (p=0.0250) and LDL cholesterol (p=0.0335) with individuals having other genotypes. However, FVII polymorphism showed no association with lipid levels. In conclusion, the 4G/5G PAI-1 promoter polymorphism and Arg353-->Gln FVII polymorphism are not major genetic risk factors for CAD in Koreans. However, 4G allele of PAI-1 polymorphism revealed to be associated with the levels of cholesterol, especially LDL cholesterol levels in CAD patients.

Participation of type II protein kinase A in the retinoic acid-induced growth inhibition of SH-SY5Y human neuroblastoma cells

To examine the role of protein kinase A (EC 2.7.1.37) isozymes in the retinoic acid-induced growth inhibition and neuronal differentiation, we investigated the changes of protein kinase A isozyme patterns in retinoic acid-treated SH-SY5Y human neuroblastoma cells. Retinoic acid induced growth inhibition and neuronal differentiation of SH-SY5Y cells in a dose- and time-dependent manner. Neuronal differentiation was evidenced by extensive neurite outgrowth, decrease of N-Myc oncoprotein, and increase of GAP-43 mRNA. Type II protein kinase A activity increased by 1.5-fold in differentiated SH-SY5Y cells by retinoic acid treatment. The increase of type II protein kinase A was due to the increase of RIIbeta and Calpha subunits. Since type II protein kinase A and RIIbeta have been known to play important role(s) in the growth inhibition and differentiation of cancer cells, we further investigated the role of the increased type II protein kinase A by overexpressing RIIbeta in SH-SY5Y cells. The growth of RIIbeta-overexpressing cells was slower than that of parental cells, being comparable to that of retinoic acid-treated cells. Retinoic acid treatment further increased the RIIbeta level and further inhibited the growth of RIIbeta-overexpressing cells, showing strong correlation between the level of RIIbeta and growth inhibition. However, RIIbeta-overexpressing cells did not show any sign of neuronal differentiation and responded to retinoic acid in the same way as parental cells. These data suggest that protein kinase A participates in the retinoic acid-induced growth inhibition through the up-regulation of RIIbeta/type II protein kinase A.

Leukemia initiated by PMLRARalpha: the PML domain plays a critical role while retinoic acid-mediated transactivation is dispensable

The most common chromosomal translocation in acute promyelocytic leukemia (APL), t15;17(q22;q21), creates PMLRARalpha and RARalphaPML fusion genes. We previously developed a mouse model of APL by expressing PMLRARalpha in murine myeloid cells. In order to examine the mechanisms by which PMLRARalpha can initiate leukemia, we have now generated transgenic mice expressing PMLRARalpham4 and RARalpham4, proteins that are unable to activate transcription in response to retinoic acid. PMLRARalpham4 transgenic mice developed myeloid leukemia, demonstrating that transcriptional activation by PMLRARalpha is not required for leukemic transformation. The characteristics of the leukemias arising in the PMLRARalpham4 transgenic mice varied from those previously observed in our PMLRARalpha transgenic mice, indicating that ligand responsiveness may influence the phenotype of the leukemic cells. The leukemias that arose in PMLRARalpham4 transgenic mice did not differentiate in response to retinoic acid therapy. This result supports the hypothesis that a major therapeutic effect of retinoic acid is mediated directly through the PMLRARalpha protein. However, a variable effect on survival suggested that this agent may be of some benefit in APL even when leukemic cells are resistant to its differentiative effects. Transgenic mice expressing high levels of RARalpham4 have not developed leukemia, providing evidence that the PML domain of PMLRARalpha plays a specific and critical role in the pathogenesis of APL. (Blood. 2000;95:1541-1550)

Differentiation induction of canine osteosarcoma cell lines by retinoids

The effect of two retinoids, all- trans and 9- cis retinoic acid, on the differentiation of three canine osteosarcoma cells (OOS, HOS, and POS) was examined using markers specifically expressed by phenotypic osteoblasts. Both retinoids induced morphologic differentiation in all the canine osteosarcoma cells. Retinoids enhanced cell flattening and spreading, as well as reduction in cell overlapping. Alkaline phosphatase (ALP) activity and ALP staining was enhanced in OOS, and HOS cells, but decreased in POS cells. These results may suggest that OOS and HOS cells have immature osteoblastic properties and POS cells have mature osteoblastic properties. Retinoids decreased osteocalcin production in all the osteosarcoma cells. They induced an increase in production of type I collagen in HOS and POS cells, but a decrease in OOS cells. These results indicate that retinoids induce differentiation of canine osteosarcoma cells, resulting in an altered expression of their malignant phenotype.

The visible man: three-dimensional interactive musculoskeletal anatomic atlas of the lower extremity

A personal computer-based interactive musculoskeletal anatomic atlas of the lower extremity has been created by using the Visible Human Male data set. A semiautomatic segmentation program was developed by using an intelligent scissors approach and shape-based interpolation, thus considerably reducing the laborious work of the segmentation and labeling process. Manual contour extractions at 3-mm section intervals and shape-based interpolations of intervening sections of the musculoskeletal structures of the lower extremity were performed. For interactive and realistic three-dimensional display, an efficient binary volume rendering method was developed that introduces the concept of shear-warp factorization and applies a newly developed normal calculation technique. Binary volume rendering reconstructs various structures from a series of two-dimensional sections in a few seconds, thus enabling real-time manipulations of the computerized atlas. All of the muscles, tendons, and bones of the lower extremity have been segmented and labeled. The volume-based three-dimensional interactive atlas supports various interactions including rotation, removal, highlighting with artificial colors, arbitrary cutting operation, transparent view, and descriptive knowledge representation. In addition, browsing through the two-dimensional images of transverse, coronal, and sagittal views with labeling and segmentation information is possible.

In vitro retinoid-induced growth inhibition and morphologic differentiation of canine osteosarcoma cells

OBJECTIVE

To determine differentiation and growth inhibition effects of retinoids on canine osteosarcoma cells.

SAMPLE POPULATION

3 osteosarcoma cell lines established from osteosarcomas in dogs.

PROCEDURE

Osteosarcoma cells were incubated with various concentrations of all-trans-retinoic acid and 9-cis-retinoic acid or control medium, counted daily for 10 days, and evaluated for morphologic changes. Synthesis of DNA was measured by use of a cell proliferation ELISA. To analyze effect of retinoids on colony formation on plastic dishes, cells were cultured for 14 days, fixed, and stained; number of colonies was counted.

RESULTS

In a dose-dependent manner, both retinoids induced morphologic differentiation and growth inhibition in the 3 osteosarcoma cell lines and inhibited each cell's ability to form anchorage-dependent colonies.

CONCLUSION AND CLINICAL RELEVANCE

Retinoids induced differentiation of osteosarcoma cells of dogs, resulting in altered expression of their malignant phenotype. Induction of differentiation by retinoids may have potential as an adjunctive treatment for osteosarcoma in dogs.

Sp1 mediates cell proliferation-dependent regulation of rat DNA topoisomerase IIalpha gene promoter

DNA topoisomerase IIalpha (topo IIalpha) is an essential nuclear enzyme required for chromosome segregation during mitosis. Consistent with its critical role in cell division is the fact that the expression of the gene for topo IIalpha is strongly regulated by the proliferation state of cells. Using a transient expression system, we determined the contribution of putative cis-acting elements in its promoter region to its basal level and cell proliferation-dependent transcription. Experiments with 5' and/or 3' serial deletion and site-directed mutation revealed that (1) maximal promoter activity resides in the fragment extending to position -663 bp from the ATG initiation codon, (2) minimal promoter activity is harboured at -195 bp, (3) the defined minimal promoter contains only two putative elements, inverted CCAAT box 4 (ICB4) (-166 to -162 bp) and the most proximal GC-rich box in the promoter (GC2) (-149 to -143 bp), and (4) ICB4 is most important in the basal-level transcription of the gene for rat topo IIalpha. The luciferase activities of the mutated reporter plasmids in G(0)-arrested and exponentially growing cells showed that proliferation-specific regulation is controlled mainly by GC2. Electrophoretic mobility-shift assays indicated that Sp1 binds specifically to the GC2 site. The extent of DNA-protein complex formation increases after the stimulation of cells to proliferate. These results indicate that the increased binding activity of Sp1 to GC2 is important in the up-regulation of the gene for topo IIalpha in growing cells.

The antihypertensive effect of the berberine derivative 6-protoberberine in spontaneously hypertensive rats

Berberine is a natural isoquinoline alkaloid found in plants of the Ranunculaceae and Berberidaceae families. Extracts from berberine-containing plants have been used as traditional Chinese folk remedies for centuries. The antihypertensive effects of the berberine derivative 6-protoberberine (PTB-6) were studied in spontaneously hypertensive rats (SHRs). In conscious SHRs, PTB-6 lowered the systolic blood pressure in a dose-dependent manner (6-PTB: 5 mg/kg, -31.1 +/- 1.6 mm Hg; 10 mg/kg, -42.4 +/- 3.1 mm Hg). Cardiac output using the thermodilution method was reduced in PTB-6-treated anesthetized SHRs with a tendency to decrease in heart rate. Injection of PTB-6 into the intracerebral ventricles of SHRs lowered the systolic arterial blood pressure and heart rate. The berberine derivative PTB-6 is an effective antihypertensive agent. The mechanism of the antihypertensive effect of PTB-6 is probably through a central sympatholytic effect.

Insulin-induced oxidative neuronal injury in cortical culture: mediation by induced N-methyl-D-aspartate receptors

While effectively attenuating neuronal apoptosis in mouse cortical culture, insulin paradoxically induced neuronal necrosis with 48 h of exposure. The insulin neurotoxicity was blocked by an antioxidant but not by caspase inhibitors. Exposure to insulin led to tyrosine phosphorylation of the insulin receptor and the insulin-like growth factor-1 (IGF-1) receptor and activation of protein kinase C (PKC) and phosphoinositide 3-kinase (PI3-kinase). Inhibitors of tyrosine kinase and PKC, but not PI3-kinase, attenuated the insulin neurotoxicity. Conversely, the inhibitor of PI3-kinase but not PKC reversed the antiapoptotic effect of insulin. Suggesting that the gene activity-dependent emergence of excitotoxicity contributed to insulin neurotoxicity, macromolecule synthesis inhibitors and N-methyl-D-aspartate (NMDA) antagonists blocked it. Consistently, exposure to insulin increased the level of the NR2A subunit of the NMDA receptor without much altering NR1 or NR2B levels. The present study suggests that insulin can be both neuroprotective and neurotoxic in the same cell system but by way of different signaling cascades.

The beta-subunit of human choriogonadotropin interacts with the exodomain of the luteinizing hormone/choriogonadotropin receptor and changes its interaction with the alpha-subunit

Human CG (hCG) consists of a common alpha-subunit and a hormone-specific beta-subunit. Similarly, its receptor is also composed of two domains, an extracellular N-terminal half (exodomain) and a membrane-associated C-terminal half (endodomain). hCG initially binds the exodomain of the receptor after which the resulting hCG/exodomain complex is thought to interact with the endodomain. This secondary interaction is considered responsible for signal generation. Despite the importance, it is unclear which hormone subunit interacts with the exodomain or the endodomain. As a step to determine the mechanisms of the initial and secondary interactions and signal generation, we investigated the interaction of the hormone-specific beta-subunit in hCG with the receptor's exodomain. A photoactivable hCG derivative consisting of the wild-type alpha-subunit and a photoactivable beta-subunit derivative was prepared and used to label the exodomain. The analysis and immunoprecipitation of photoaffinity labeled exodomain demonstrate that the beta-subunit in hCG makes the direct contact with the exodomain.

APOBEC-2, a cardiac- and skeletal muscle-specific member of the cytidine deaminase supergene family

APOBEC-1, which mediates the editing of apolipoprotein (apo) B mRNA, is the only known member of the C (cytidine)-->U (uridine) editing enzyme subfamily of the cytidine deaminase supergene family. Here we report the cloning of APOBEC-2, another member of the subfamily. Human and mouse APOBEC-2 both contain 224 amino acid residues, and their genes are mapped to syntenic regions of human chromosome 6 (6p21) and mouse chromosome 17. By phylogenetic analysis, APOBEC-2 is shown to be evolutionarily related to APOBEC-1, and analysis of substitution rates indicates that APOBEC-2 is a much better conserved gene than APOBEC-1. APOBEC-2 mRNA and protein are expressed exclusively in heart and skeletal muscle. APOBEC-2 does not display detectable apoB mRNA editing activity. Like other editing enzymes of the cytidine deaminase superfamily, APOBEC-2 has low, but definite, intrinsic cytidine deaminase activity. The identification of APOBEC-2 indicates that APOBEC-1 is not the only member of the C-->U editing enzyme subfamily, which, like the A (adenosine)-->I (inosine) subfamily of editing enzymes, must encompass at least two and possibly more different deaminase enzymes. It suggests that the C-->U editing affecting apoB mRNA and other RNAs is not an isolated event mediated by a single enzyme but involves multiple related proteins that have evolved from a primordial gene closely related to the housekeeping enzyme cytidine deaminase.

Dysplastic nodules of the liver: imaging findings

BACKGROUND

To verify characteristic features of hepatic dysplastic nodules at different imaging modalities.

METHODS

Twenty-eight patients with 37 dysplastic nodules of the liver (0.8-3.0 cm) underwent sonography (28 patients), computed tomography (CT; 24 patients), magnetic resonance (MR; 11 patients), and angiography (12 patients). Each nodule was analyzed for echogenicity, attenuation, signal intensity, and vascularity.

RESULTS

Echogenicity of nodules was high in 16 (43%), homogeneous in two (6%), and low in 19 (51%) of 37 nodules. Attenuation of nodules was high in one (7%), homogeneous in four (26%), and low in 10 (67%) of 15 nodules on the arterial-phase CT images; homogeneous in five (33%) and low in 10 (67%) of 15 nodules on the portal-phase CT images; and high in four (17%), homogeneous in six (26%), and low in 13 (57%) of 23 nodules on the delayed-phase CT images. Signal intensity of nodules was high in 15 (94%) and homogeneous in one (6%) of 16 nodules on T1-weighted MR images and was homogeneous in seven (44%) and low in nine (56%) of 16 nodules on T2-weighted MR images. Vascularity of nodules was avascular in 14 (88%) and slightly vascular in two (12%) of 16 nodules.

CONCLUSIONS

Hepatic dysplastic nodules show diverse imaging characteristics with different imaging techniques; however, common imaging findings of hepatic dysplastic nodules are low echo, low attenuation, and high, low, or homogeneous intensity on T1- and T2-weighted MR, and avascularity.

Ala99ser mutation in RI alpha regulatory subunit of protein kinase A causes reduced kinase activation by cAMP and arrest of hormone-dependent breast cancer cell growth

Expression of the RIalpha regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RIalpha was replaced with Ser (RIalpha-p) for the structure-function analysis of RIalpha. MCF-7 hormone-dependent breast cancer cells were transfected with an expression vector for the wild-type RIalpha or mutant RIalpha-p. Overexpression of RIalpha-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RIalpha overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RIIbeta, suppressed RIalpha and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I.

Relationship of arachidonic acid metabolizing enzyme expression in epithelial cancer cell lines to the growth effect of selective biochemical inhibitors

Arachidonic acid (AA) metabolizing enzymes are emerging as significant mediators of growth stimulation for epithelial cells. The relative contribution of the various family members of AA metabolizing enzymes to epithelial cancer cell growth is not known. To study this question, we first analyzed a series of epithelial cancer cells to establish the relative frequency of expression for the various enzymes. We analyzed the expression of five AA metabolizing enzymes as well as 5-lipoxygenase activating protein (FLAP) in a panel of human epithelial cancer cell lines (n = 20) using reverse transcription-PCR. From this analysis, we found that cyclooxygenase-1 (COX-1), 5-lipoxygenase (5-LOX), and FLAP were universally expressed in all cancer cell lines tested. For the remaining enzymes, the expression of COX-2, 12-LOX, and 15-LOX varied among cell lines, 60, 35, and 90%, respectively. Although the pattern of expression varied among the different cell types, all of the enzymes were expressed in all major cancer histologies. Using a panel of selective biochemical AA metabolizing enzyme inhibitors, we then evaluated the effect of these agents on cell lines with known expression status for the AA metabolizing enzymes. For the enzymes that were not universally expressed, growth inhibition by selective biochemical inhibitors did not closely correlate with the expression status of specific enzymes (P > 0.05). For the universally expressed enzymes, the LOX inhibitors were more potent growth inhibitors than the COX inhibitors. The frequent expression of the AA metabolizing enzymes suggests that AA metabolism pathway may be modulated in response to xenobiotic exposure during carcinogenesis. Although establishing a priori AA metabolizing enzyme status was not consistently informative about what AA metabolizing enzyme inhibition would be most growth inhibitory, the frequent inhibition of many epithelial cancers by these biochemical inhibitors opens a new avenue for cancer therapy and intervention in carcinogenesis.

Isolation of developmentally regulated novel genes based on sequence identity and gene expression pattern

Based on the surmise that a variety of genes might play important roles in embryonic development and tissue differentiation, and that some of them are likely to be expressed in undifferentiated ES cells, we attempted to identify new genes from the ES cell cDNA library. The modified method of expressed sequence tags (ESTs) and the examination of the expression patterns in adult tissues and in vitro differentiated ES cells were utilized in this study. We have isolated and identified several novel cDNA clones with interesting developmental expression pattern. Among the 83 clones randomly chosen, 23 clones (27.7%) have no homology to any sequences in public databases. The rest contain limited or complete sequence homology to the previously reported mammalian genes or ESTs, yet some clones have not been previously identified in the mouse. To examine the expression profile of clones during development and differentiation, sets of slot blots were hybridized with developmental stage specific or tissue specific probes. Out of 40 novel clones tested (21 totally unknown clones and 19 unidentified clones in mouse), most of them were up- or down-regulated as differentiation proceeded, and some clones showed differentiation-stage specific expression profiles. Surprisingly, a majority of genes were also expressed in adult tissues, and some clones even revealed tissue specific expression. These results demonstrate that not only was the strategy we employed in this study quite efficient for screening novel genes, but that the information gained by such studies would also be a useful guide for further analysis of these genes. It also suggests the feasibility of this approach to explore the genomewide network of gene expression during complicated biological processes, such as embryonic development and tissue differentiation.