CGH alterations in medullary thyroid carcinomas in relation to the RET M918T mutation and clinical outcome

Apart from the RET proto-oncogene (RET) no other genes have been found to be involved in medullary thyroid carcinoma (MTC) tumorigenesis. Germline RET mutations are seen virtually in all familial forms of MTC and somatic RET mutations are often detected in sporadic MTC. In sporadic MTCs the RET gene is mutated in codon 918, where a methionine is substituted to a threonine (M918T). In this study 24 MTCs were analyzed by comparative genomic hybridization (CGH) for chromosomal imbalances. Overall, alterations were detected in approximately 60% of the samples. The most common aberrations were gains on chromosome 19q (29%), 19p (21%), 11c-q12 (12.5%), and 22q (12.5%) and losses on 13q21 (21%) and 3q23-qter (12.5%). Gain of chromosome 11c-q12 was only detected in samples from patients whom died of MTC (p=0.001). These MTCs also harbored the somatic RET M918T mutation and also showed the highest numbers of CGH alterations in the series (p<0.003). Although there was a tendency towards a higher number of CGH imbalances in the tumors with RET M918T mutation, this difference was not significant. The results indicate that MTC is a comparatively genetically stable tumor, and that chromosomal regions 19q, 19p, 13q and 11q may be involved in MTC carcinogenesis.

Preparation and application of antibodies to phosphoamino acid sequences

In this review, we describe methods to generate and characterize sequence-specific phosphoamino acid antibodies. Several of the early contributions regarding the utility of such antibodies are summarized. Three antiphosphopeptide antibodies derived from sequences of the Bcr protein are described. They are anti-Bcr pSer-354, anti-Bcr pTyr-328, and anti-Bcr pTyr-360. These anti-Bcr phosphopeptide antibodies are directed toward phosphorylated sequences encoded by the first exon of the BCR gene, which is the critical portion of the Bcr sequence present in the Bcr-Abl oncoprotein. Using these antibodies, we established/confirmed the in vivo phosphorylation of Ser-354, Tyr-328, and Tyr-360 in Bcr and Bcr-Abl proteins. The cross-reactivity of these antibodies, which is a common problem with antipeptide antibodies, was also investigated and discussed.

Expression of heparanase, Mdm2, and erbB2 in ovarian cancer

Ovarian cancer is the most lethal of gynecological malignancies. Yet early diagnosis and prognosis are far from being satisfactory. Degradation of heparan sulfate proteoglycans by heparanase appears to play an important role in the invasiveness of tumor cells through the basement membrane and into the extracellular matrix. Recent cloning of the heparanase gene and generation of monoclonal antibodies against the enzyme permit to examine tumor cell expression of the enzyme. The aim of the present study was to assess heparanase activity and localization in various subtypes of epithelial ovarian cancer in correlation with oncogene expression. Histologically confirmed malignant ovarian tissue from ten women and tissue from 2 benign ovarian tumors and 4 normal ovaries were assessed for heparanase presence, activity and localization, incidence of apoptosis and expression of the oncogenes erbB2 and Mdm2. Heparanase immunohistostaining and activity were present in mucinous carcinomas and were more intense than in endometrioid and in serous carcinomas. The lowest activity was observed in benign ovarian tumors and normal ovaries. In ovarian carcinomas the enzyme was intensely concentrated in the cytoplasm of the cancerous cells. In contrast, in normal ovaries and benign tumors the enzyme was predominantly localized in endothelial cells lining blood capillaries. The rate of apoptosis was considerably higher in mucinous and endometrioid carcinomas, and was lower in serous and primary peritoneal carcinomas. Extremely high concentration of heparanase was often demonstrated in apoptotic cells. Endometrioid and serous carcinomas showed high expression of Mdm2 and erbB2 while mucinous carcinomas showed low expression. In benign ovarian tumors and normal ovaries the expression of both oncoproteins was extremely low. In conclusion ovarian carcinomas demonstrate higher levels of heparanase than benign tumors and normal ovaries suggesting that the enzyme may play an important role in metastatic spread of the cancerous cells. Apoptosis may be a significant part of the mechanism of the enzyme release into the extracellular space. Although heparanase activity seems to play an essential role in tumor progression, expression of oncogenes, such as erbB2 and Mdm2 seems to play the dominant role in the development of ovarian cancer.

Evidence for the involvement of Gi2 in activation of extracellular signal-regulated kinases in hepatocytes

BACKGROUND

Activation of the extracellular signal-regulated kinases ERK1 and ERK2 in hepatocytes by prostaglandin (PG)F2alpha was recently found to be inhibited by pertussis toxin (PTX) suggesting a role for Gi proteins.

RESULTS

Targeting the Gi2alpha expression by a specific ribozyme inhibited the PGF2alpha -induced ERK1/2 activation in hepatocytes. On the other hand a non-cleaving form of the Gi2alpha ribozyme did not significantly decrease the ERK1/2 activation. In ribozyme-treated cells the Gi2alpha protein level was reduced, while the Gqalpha level was not affected thus confirming the specificity of the ribozyme.

CONCLUSION

The present data suggest an important role of Gi2 in PGF2alpha -induced ERK1/2 signaling in hepatocytes.

Expression patterns of Notch1, Notch2, and Notch3 suggest multiple functional roles for the Notch-DSL signaling system during brain development

The Notch-DSL signaling system consists of multiple receptors and ligands, and plays many roles in development. The function of Notch receptors and ligands in mammalian brain, however, is poorly understood. In the current study, we examined the expression patterns for three receptors of this system, Notch1, 2, and 3, in late embryonic and postnatal rat brain by in situ hybridization. The three receptors have overlapping but different patterns of expression. Messenger RNA for all three proteins is found in postnatal central nervous system (CNS) germinal zones and, in early postnatal life, within numerous cells throughout the CNS. Within zones of cellular proliferation of the postnatal brain, Notch1 mRNA is found in both the subventricular and the ventricular germinal zones, whereas Notch2 and Notch3 mRNAs are more highly localized to the ventricular zones. Both Notch1 and Notch3 mRNAs are expressed along the inner aspect of the dentate gyrus, a site of adult neurogenesis. Notch2 mRNA is expressed in the external granule cell layer of the developing cerebellum. In several brain areas, Notch1 and Notch2 mRNAs are relatively concentrated in white matter, whereas Notch3 mRNA is not. Neurosphere cultures (which contain CNS stem cells), purified astrocyte cultures, and striatal neuron-enriched cultures express Notch1 mRNA. However, in these latter cultures, Notch1 mRNA is produced by nestin-containing cells, rather than by postmitotic neurons. Taken together, these results support multiple roles for Notch1, 2, and 3 receptor activation during CNS development, particularly during gliogenesis.

Promiscuity of pre-mRNA spliceosome-mediated trans splicing: a problem for gene therapy?

Trans splicing of messenger RNA has been used in experimental settings to replace mutant RNA sequences. We investigated the feasibility of utilizing trans splicing to replace a mutant RET protooncogene sequence known to inappropriately activate this tyrosine kinase receptor. We constructed a pre-trans-splicing molecule (PTM) consisting of a binding domain complementary to the target intron, the 3' splicing signal sequence (3'ss), derived from adenovirus major late transcript intron 1 and a molecular tag sequence. Accurately targeted trans splicing between the human RET exons and the PTM was demonstrated in NIH 3T3 cells cotransfected with the human RET minigene and the PTM. The efficiency of specific trans splicing was estimated to be no more than 15% in the cotransfection experiment. However, in addition to the targeted trans splicing, nontargeted trans splicing to RET exons was observed. Furthermore, the rapid amplification of 5' cDNA ends (5' RACE) analysis demonstrated that nontargeted trans splicing occurred with endogenously expressed pre-mRNAs in TT cells and that specific trans splicing to RET was a rare event. Attempts to reduce nonspecificity by the addition of a stem-loop to the trans-splicing construct designed to suppress nonspecific splicing failed to have the desired effect. These observations suggest that overexpression of a trans-splicing construct containing a 3'ss results in promiscuous trans splicing and raise significant questions about the specificity and usefulness of currently used trans-splicing approaches. In addition, these findings raise the possibility that nonspecific spliced products may be produced by a variety of gene therapy constructs.

Binding of BAZF and Bc16 to STAT6-binding DNA sequences

BAZF, a family member of Bcl6, can function as a sequence-specific transcriptional repressor. We determined BAZF-binding DNA sequence. The consensus binding sequence (CBS) of BAZF is almost the same as those of Bcl6 previously described. Three nucleotides of T, G and A at position 6, 8, and 9 in the CBS (5'-ATTCCTAGAAAG-3') are important nucleotides for binding of both BAZF and Bcl6. Since a part (5'-TTC-CTA-GAA-3') of the CBS resembled the sequence motif (5'-TTC-(N3-4)-GAA-3') bound by STAT factors, BAZF and Bcl6 can bind to the CD23b-STAT6-binding sequence (5'-TTTC-TTA-GAAAT-3'), the immunoglobulin germline epsilon-STAT6-binding sequence (5'-CTTC-CCAA-GAAC-3'), and the IL4-STAT6-binding sequence (5'-TTTC-CCA-GAAAA-3') with weak affinity. However, a mutation of C nucleotide to T nucleotide in the IL4-STAT6-binding sequence (5'-TTTC-CTA-GAAAA-3') strongly increased the binding activity of BAZF and Bcl6. These results suggest that BAZF and Bcl6 can repress some of STAT-induced transcription by binding to DNA sequences recognized by STAT factors.

Reactive oxygen species up-regulates cyclooxygenase-2, p53, and Bax mRNA expression in bovine luteal cells

Reactive oxygen species (ROS) are well-established modulators of luteal cell apoptosis in the estrous cycle. The objective of this study was to clarify the molecular mechanisms of luteolysis by characterizing the levels and regions of mRNAs involved in ROS-induced luteal cell apoptosis. Stimulation of bovine luteal cells by H2O2 resulted in the induction of apoptotic nuclear condensation and Caspase-3 activation. In addition, a marker for oxidative stress-damaged DNA, 8-hydroxy-2'-deoxyguanosine, was highly accumulated in the large luteal cells prepared from the late estrous stage. Reverse transcription polymerase chain reaction and Northern blot analysis demonstrated that mRNAs of cyclooxygenase (COX)-2, p53, and Bax were highly accumulated in the H2O2-treated cells. In situ hybridization revealed that these mRNAs were most abundantly expressed in the large luteal cells. These findings suggest that enhancement of ROS in the bovine corpus luteum induces expression of COX-2, p53, and Bax mRNAs, resulting in activation of the signaling pathway for luteal-cell apoptosis.

Oncogenic transformation induced by membrane-targeted Akt2 and Akt3

The kinases Akt2, Akt3 and their myristylated variants, Myr-Akt2 and Myr-Akt3 were expressed by the RCAS vector in chicken embryo fibroblasts (CEF). Myr-Akt2 and Myr-Akt3 were strongly oncogenic, inducing multilayered foci of transformed cells. In contrast, wild-type Akt2 and Akt3 were only poorly transforming, their efficiencies of focus formation were more than 100-fold lower; foci appeared later and showed less multilayering. Addition of the myristylation signal not only enhanced oncogenic potential but also increased kinase activities. Myr-Akt2 and Myr-Akt3 also induced hemangiosarcomas in the animal, whereas wild type Akt2 and Akt3 were not oncogenic in vivo. Furthermore, Akt2, driven by the lck (lymphocyte specific kinase) promoter in transgenic mice, induced lymphomas. The oncogenic effects of Akt2 and Akt3 described here are indistinguishable from those of Akt1. The downstream targets relevant to oncogenic transformation are therefore probably shared by the three Akt kinases.

The translesion DNA polymerase zeta plays a major role in Ig and bcl-6 somatic hypermutation

Ig somatic mutations would be introduced by a polymerase (pol) while repairing DNA outside main DNA replication. We show that human B cells constitutively express the translesion pol zeta, which effectively extends DNA past mismatched bases (mispair extender), and pol eta, which bypasses DNA lesions in an error-free fashion. Upon B cell receptor (BCR) engagement and coculture with activated CD4+ T cells, these lymphocytes upregulated pol zeta, downregulated pol eta, and mutated the Ig and bcl-6 genes. Inhibition of the pol zeta REV3 catalytic subunit by specific phosphorothioate-modified oligonucleotides impaired Ig and bcl-6 hypermutation and UV damage-induced DNA mutagenesis, without affecting cell cycle or viability. Thus, pol zeta plays a critical role in Ig and bcl-6 hypermutation, perhaps facilitated by the downregulation of pol eta.

Akt activation preserves cardiac function and prevents injury after transient cardiac ischemia in vivo

BACKGROUND

The serine-threonine kinase Akt is activated by several ligand-receptor systems previously shown to be cardioprotective. Akt activation reduces cardiomyocyte apoptosis in models of transient ischemia. Its role in cardiac dysfunction or infarction, however, remains unclear.

METHODS AND RESULTS

We examined the effects of a constitutively active Akt mutant (myr-Akt) in a rat model of cardiac ischemia-reperfusion injury. In vivo gene transfer of myr-Akt reduced infarct size by 64% and the number of apoptotic cells by 84% (P<0.005 for each). Ischemia-reperfusion injury decreased regional cardiac wall thickening as well as the maximal rate of left ventricular pressure rise and fall (+dP/dt and -dP/dt). Akt activation restored regional wall thickening and +dP/dt and -dP/dt to levels seen in sham-operated rats. To better understand this benefit, we examined the effects of myr-Akt on hypoxic cardiomyocyte dysfunction in vitro. myr-Akt prevented hypoxia-induced abnormalities in cardiomyocyte calcium transients and shortening. Akt activation also enhanced sarcolemmal expression of Glut-4 in vivo and increased glucose uptake in vitro to the level seen with insulin treatment.

CONCLUSIONS

Akt activation exerts a powerful cardioprotective effect after transient ischemia that probably reflects its ability to both inhibit cardiomyocyte death and improve function of surviving cardiomyocytes. Akt may represent an important nodal target for therapy in ischemic and other heart disease.

Elimination of Bax expression in mice increases cerebellar purkinje cell numbers but not the number of granule cells

Cerebellar Purkinje cells and granule cells have been studied extensively as models for investigating neuron-target interactions and the regulation of cell numbers in the developing central nervous system. Recent studies of transgenic mice that overexpress a human Bcl-2 transgene in Purkinje cells suggest both that programmed cell death plays an unexpected role in regulating Purkinje cell number and that Purkinje cells influence the number of granule cells. The role of cell death-related proteins and Purkinje-granule cell interactions in cerebellar development was investigated further in this study by counting the number of Purkinje and granule cells in knockout mutants with a deletion in the proapoptotic gene, Bax. The total number of Purkinje cells was estimated using stereological counting principles in six adult wild type mice, four hemizygous Bax +/- controls, and six Bax -/- knockout mutants. The total number of granule cells per cerebellum was estimated in three adult wild type mice, three hemizygous Bax +/- controls, and three Bax -/- knockout mutants. The number of Purkinje cells increased significantly by over 30% in the Bax -/- knockout mutants compared with wild type and hemizygote controls, whereas the number of granule cells was unchanged in the Bax -/- mutants. There was no change in the volume of the cerebellar cortex or in the size of Purkinje cell bodies in the Bax -/- mutants, implying that Purkinje cell density was increased in the Bax -/- mutants. The increase in Purkinje cell numbers in the Bax -/- knockout mice supports previous evidence that Purkinje cells undergo a period of naturally occurring cell death that is mediated at least in part by the cell death proteins Bcl-2 and Bax. The lack of an effect of Bax gene expression on granule cell numbers indicates that Bax is not an obligate participant in naturally occurring cell death in granule cells.

The casein kinase I family in Wnt signaling

The canonical Wnt-signaling pathway is critical for many aspects of development, and mutations in components of the Wnt pathway are carcinogenic. Recently, sufficiency tests identified casein kinase Iepsilon (CKIepsilon) as a positive component of the canonical Wnt/beta-catenin pathway, and necessity tests showed that CKIepsilon is required in vertebrates to transduce Wnt signals. In addition to CKIepsilon, the CKI family includes several other isoforms (alpha, beta, gamma, and delta) and their role in Wnt sufficiency tests had not yet been clarified. However, in Caenorhabditis elegans studies, loss-of-function of a CKI isoform most similar to alpha produced the mom phenotype, indicative of loss-of-Wnt signaling. In this report, we examine the ability of the various CKI isoforms to activate Wnt signaling and find that all the wild-type CKI isoforms do so. Dishevelled (Dsh), another positive component of the Wnt pathway, becomes phosphorylated in response to Wnt signals. All the CKI isoforms, with the exception of gamma, increase the phosphorylation of Dsh in vivo. In addition, CKI directly phosphorylates Dsh in vitro. Finally, we find that CKI is required in vivo for the Wnt-dependent phosphorylation of Dsh. These studies advance our understanding of the mechanism of Wnt action and suggest that more than one CKI isoform is capable of transducing Wnt signals in vivo.

Expression of vascular endothelial growth factor and its receptors Flt-1 and KDR/Flk-1 in chronic cyclosporine nephrotoxicity

BACKGROUND

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen involved in angiogenesis, wound healing, and inflammation.

METHODS

Rats placed on low salt diet (LSD) or normal salt diet (NSD) were treated with cyclosporine (CsA) or vehicle (VH) and killed at 7 or 28 days. We studied the expression of VEGF and its receptors Flt-1 and KDR/Flk-1 mRNA by Northern and that of VEGF protein by Western blot.

RESULTS

CsA induced VEGF mRNA and protein expressions at 7 and 28 days in LSD rats. At 7 days, CsA up-regulated the expression of Flt-1 and KDR/Flk-1 receptors; however, at 28 days, Flt-1 remained unchanged whereas KDR/Flk-1 expression declined. In NSD rats, in which the lesion did not develop, the expression of VEGF and its receptors remained similar to control.

CONCLUSIONS

What causes VEGF to be up-regulated remains unclear. Further studies are needed to study the role of hypoxia and other cytokines in relation to VEGF in this model.

Translocation (2;14) associated with complex rearrangements of the Ig heavy chain in non-Hodgkin lymphoma

Cytogenetic analysis of a patient with non-Hodgkin lymphoma revealed the following karyotype: 49,XXX,t(2;14)(q21;q32),+4,+8,del(13)(q14q21). Southern blot analysis with an Ig region probe showed non-productive rearrangements indicative of a translocation involving the Ig locus. However, molecular cloning of the abnormal rearrangements did not show novel sequences derived from chromosome 2 but showed that the BCL-6 gene was juxtaposed to the IgH enhancer. Three further clones with abnormal rearrangements involving the Ig locus, particularly Iggamma3, were isolated. This suggests that the mature lymphoid cells, in this patient, were capable of undergoing indiscriminate switch cleavage and religation.

The role of protein kinase B (PKB) in modulating heat sensitivity in a human breast cancer cell line

PURPOSE

Protein kinase B (PKB) is a critical mediator of phosphoinositide 3-kinase-dependent survival signals in mammalian cells. Its activity is induced after heat shock, and is inhibited in cells undergoing apoptosis. We hypothesized that PKB may be an important modulator for heat-induced apoptosis in human cancer cells.

METHODS AND MATERIALS

MCF-7 cells were transfected using four different plasmids, encoding a kinase-dead mutant PKB-AAA, a constitutively activated mutant PKB-DD, wild-type PKB, and the neomycin-resistant selection gene. These stable transfectants were subjected to heat shock, and assessed for PKB phosphorylation, PKB activity, and likelihood of undergoing apoptosis.

RESULTS

After heating to 45 degrees C x 30 mins, 25% of MCF-7/neo transfectants underwent apoptosis, which increased to 38% in the presence of wortmannin (WT), an inhibitor of phosphoinositide 3-kinase. In contrast, 23% of the constitutively activated MCF-7/DD transfectants underwent apoptosis, minimally affected by WT. Heat-induced apoptosis occurred in 34% of the kinase-dead MCF-7/AAA transfectants, which increased further to 58% with the addition of WT. This in turn was associated with a two-fold reduction in clonogenic survival compared to the MCF-7/neo transfectants.

CONCLUSION

Heat shock activation of PKB in human MCF-7 cells appears to be a significant modulator of heat-induced apoptosis and survival. Further understanding of this important pathway may offer potential in developing novel strategies in cancer therapy.

The EGF receptor and notch signaling pathways control the initiation of the morphogenetic furrow duringDrosophilaeye development

The onset of pattern formation in the developing Drosophila retina begins with the initiation of the morphogenetic furrow, the leading edge of a wave of retinal development that transforms a uniform epithelium, the eye imaginal disc into a near crystalline array of ommatidial elements. The initiation of this wave of morphogenesis is under the control of the secreted morphogens Hedgehog (Hh), Decapentaplegic (Dpp) and Wingless (Wg). We show that the Epidermal Growth Factor Receptor and Notch signaling cascades are crucial components that are also required to initiate retinal development. We also show that the initiation of the morphogenetic furrow is the sum of two genetically separable processes: (1) the ‘birth’ of pattern formation at the posterior margin of the eye imaginal disc; and (2) the subsequent ‘reincarnation’ of retinal development across the epithelium.

Receptor specificity in the self-renewal and differentiation of primary multipotential hemopoietic cells

To determine whether cytokine-induced signals generate unique responses in multipotential hemopoietic progenitor cells, the signaling domains of 3 different growth factor receptors (Mpl, granulocyte-colony-stimulating factor [G-CSF] receptor, and Flt-3) were inserted into mouse primary bone marrow cells. To circumvent the activation of endogenous receptors, each signaling domain was incorporated into an FK506 binding protein (FKBP) fusion to allow for its specific activation using synthetic FKBP ligands. Each signaling domain supported the growth of Ba/F3 cells; however, only Mpl supported the sustained growth of transduced marrow cells, with a dramatic expansion of multipotential progenitors and megakaryocytes. These findings demonstrate that the self-renewal and differentiation of multipotential progenitor cells can be influenced through distinct, receptor-initiated signaling pathways.

Pharmacogenomic dissection of resistance to thymidylate synthase inhibitors

Chemoresistance is a major obstacle for successful cancer treatment. Gene amplification and altered expression are the main genetic mechanisms of tumor chemoresistance. Previously, only a limited number of genes were analyzed in each individual study using traditional molecular methods such as Northern and Southern blotting. In this study, the global gene expression patterns of 1176 genes in a panel of five thymidylate synthase (TS) inhibitor [raltitrexed (TDX) and 5-fluorouracil (5-FU)] resistant and sensitive parent cell lines were investigated using cDNA array technology. Only 28 of 1176 genes were altered >1.5-fold among resistant cells, with 2 genes (TS and YES1) consistently higher in the panel. TS mRNA and protein were consistently overexpressed in all drug-resistant tumor cell lines compared with the sensitive parent cell lines. Southern blot and FISH analysis demonstrated that the TS gene was amplified in 5-FU- and TDX-resistant cell lines. YES1 mRNA and protein were overexpressed in four drug-resistant tumor cell lines but were not overexpressed in the lymphoblast cell line W1L2(TDX), although the YES1 gene was highly amplified in these cells. The fact that W1L2 has high level (>10-fold) resistance to TS inhibitor in the absence of high YES1 expression leads to a conclusion that YES1 has no direct role in this drug resistance process. By narrowing the search from 1176 to 2 genes, the analysis of in vitro TDX and 5-FU resistance becomes more straightforward for confirmatory studies. These data provide encouragement that comprehensive transcript analysis will aid the quest for more enlightened therapeutics.

Zebrafish fgf3 and fgf8 encode redundant functions required for otic placode induction

Members of the fibroblast growth factor (FGF) family of peptide ligands have been implicated in otic placode induction in several vertebrate species. Here, we have functionally analyzed the roles of fgf3 and fgf8 in zebrafish otic development. The role of fgf8 was assessed by analyzing acerebellar (ace) mutants. fgf3 function was disrupted by injecting embryos with antisense morpholino oligomers (MO) specifically designed to block translation of fgf3 transcripts. Disruption of either fgf3 or fgf8 causes moderate reduction in the size of the otic vesicle. Injection of fgf3-MO into ace/ace mutants causes much more severe reduction or complete loss of otic tissue. Moreover, preplacode cells fail to express pax8 and pax2.1, indicating disruption of early stages of otic induction in fgf3-depleted ace/ace mutants. Both fgf3 and fgf8 are normally expressed in the germring by 50% epiboly and are induced in the primordium of rhombomere 4 by 80% epibloy. In addition, fgf3 is expressed during the latter half of gastrulation in the prechordal plate and paraxial cephalic mesendoderm, tissues that either pass beneath or persist near the prospective otic ectoderm. Conditions that alter the pattern of expression of fgf3 and/or fgf8 cause corresponding changes in otic induction. Loss of maternal and zygotic one-eyed pinhead (oep) does not alter expression of fgf3 or fgf8 in the hindbrain, but ablates mesendodermal sources of fgf signaling and delays otic induction by several hours. Conversely, treatment of wild-type embryos with retinoic acid greatly expands the periotic domains of expression of fgf3, fgf8, and pax8 and leads to formation of supernumerary and ectopic otic vesicles. These data support the hypothesis that fgf3 and fgf8 cooperate during the latter half of gastrulation to induce differentiation of otic placodes.

Cyclin-dependent kinases and P53 pathways are activated independently and mediate Bax activation in neurons after DNA damage

DNA damage has been implicated as one important initiator of cell death in neuropathological conditions such as stroke. Accordingly, it is important to understand the signaling processes that control neuronal death induced by this stimulus. Previous evidence has shown that the death of embryonic cortical neurons treated with the DNA-damaging agent camptothecin is dependent on the tumor suppressor p53 and cyclin-dependent kinase (CDK) activity and that the inhibition of either pathway alone leads to enhanced and prolonged survival. We presently show that p53 and CDKs are activated independently on parallel pathways. An increase in p53 protein levels, nuclear localization, and DNA binding that result from DNA damage are not affected by the inhibition of CDK activity. Conversely, no decrease in retinoblastoma protein (pRb) phosphorylation was observed in p53-deficient neurons that were treated with camptothecin. However, either p53 deficiency or the inhibition of CDK activity alone inhibited Bax translocation, cytochrome c release, and caspase-3-like activation. Taken together, our results indicate that p53 and CDK are activated independently and then act in concert to control Bax-mediated apoptosis.

Molecular approaches to cerebral laterality: development and neurodegeneration

Little is understood about the genetic or epigenetic mechanisms that underlie brain asymmetry. Because higher cognitive functions such as language, constructional and spatial abilities, and attention are organized along the left/right axis, understanding the underpinnings of this process has significant implications for both developmental biology and cognitive neuroscience. However, scientists have begun to explore, in only the most preliminary manner, the influences of subtle biologically inherited brain asymmetries on human behavior and disease. Because brain asymmetry develops prenatally, the recognition of asymmetry in neurodegeneration implies a possible relationship between the development of cerebral laterality and regional vulnerability in neurodegenerative diseases. This suggests that the study of cerebral asymmetry and laterality is likely to be relevant to a number of degenerative conditions that were previously considered to be only diseases of aging. In this article, I will outline our perspective and some of the approaches that my laboratory has begun to take to characterize the molecular basis of cerebral asymmetry. Most of these data are preliminary and the models presented are highly speculative, reflecting the primitive stage of work defining the molecular basis of cerebral asymmetry.

DNA mismatch repair enzyme activity and gene expression in prostate cancer

Microsatellite instability (MSI) of short repetitive sequences in human chromosomal DNA can result from defective DNA mismatch repair function in tumor cells. We hypothesize that DNA mismatch repair (MMR) activity is down-regulated during prostatic carcinogenesis. To test this hypothesis, MMR activities and mismatch repair-related genes were analyzed in five different prostate cancer cell lines. Our results demonstrate that MMR activities were decreased as compared to MMR proficient HeLa cells. Interestingly, LNCaP, PC-3 and DU145 had much lower MMR activities as compared to DUPro and TSUPr1. The MMR-related genes (hMLH1, hPMS1, hPMS2, hMSH2, hMSH3, hMSH6) showed mRNA transcripts in all prostate cancer cell lines. However, Western blotting showed decreased or absent hMLH1 protein expression in PC-3, DU145, DUPro and TSUPr1 cells. Similarly, the hMSH2 protein expression was low or absent in DU145 and LNCaP cells. This is the first report that demonstrates decreased MMR activities is associated with low expression of hMLH1, hMSH2 and other MMR-related proteins in prostate cancer.

Diagnosis of papillary thyroid carcinoma is facilitated by using an RT-PCR approach on laser-microdissected archival material to detect RET oncogene activation

OBJECTIVE

The purpose of this study was to investigate the value of the expression of the RET oncogene (rearranged during transfection) in papillary thyroid carcinomas (PTC) and its variants in the differential diagnosis of thyroid neoplasias. According to the literature RET oncogene activation by chromosomal rearrangements has been exclusively implicated in PTCs.

METHODS

To establish the incidence of RET activation in PTCs we used 5- to 10-microm sections from archival paraffin blocks. Either parts of the tissue slices were manually dissected or a few distinct cells were microdissected by laser-mediated manipulation with the Robot-MicroBeam system. RNA was extracted from paraffin-embedded thyroid tumors and the corresponding normal tissue. RT and nested PCR were performed using primers for RET/PTC1, PTC2 and PTC3, or for RET exons 12 and 13. PCR products were resolved by gel electrophoresis.

RESULTS

We detected RET transcription in approximately 85% of the PTCs including follicular variants and in isolated cells of the same tissues, but not in nonmalignant thyroid tissue.

CONCLUSIONS

Our method may serve as an additional diagnostic tool to characterize ambiguous neoplasias and to identify especially nonpapillary, i.e. follicular tumors, as papillary carcinomas. Additionally, this study has demonstrated that expressed genes can be analyzed from routine histopathological tissue slides or pooled single cells. Large retrospective studies can also be performed with this method.