Human embryonic stem cells derived by somatic cell nuclear transfer.

Reprogramming somatic cells into pluripotent embryonic stem cells (ESCs) by somatic cell nuclear transfer (SCNT) has been envisioned as an approach for generating patient-matched nuclear transfer (NT)-ESCs for studies of disease mechanisms and for developing specific therapies. Past attempts to produce human NT-ESCs have failed secondary to early embryonic arrest of SCNT embryos. Here, we identified premature exit from meiosis in human oocytes and suboptimal activation as key factors that are responsible for these outcomes. Optimized SCNT approaches designed to circumvent these limitations allowed derivation of human NT-ESCs. When applied to premium quality human oocytes, NT-ESC lines were derived from as few as two oocytes. NT-ESCs displayed normal diploid karyotypes and inherited their nuclear genome exclusively from parental somatic cells. Gene expression and differentiation profiles in human NT-ESCs were similar to embryo-derived ESCs, suggesting efficient reprogramming of somatic cells to a pluripotent state.

Abnormalities in human pluripotent cells due to reprogramming mechanisms.

Human pluripotent stem cells hold potential for regenerative medicine, but available cell types have significant limitations. Although embryonic stem cells (ES cells) from in vitro fertilized embryos (IVF ES cells) represent the 'gold standard', they are allogeneic to patients. Autologous induced pluripotent stem cells (iPS cells) are prone to epigenetic and transcriptional aberrations. To determine whether such abnormalities are intrinsic to somatic cell reprogramming or secondary to the reprogramming method, genetically matched sets of human IVF ES cells, iPS cells and nuclear transfer ES cells (NT ES cells) derived by somatic cell nuclear transfer (SCNT) were subjected to genome-wide analyses. Both NT ES cells and iPS cells derived from the same somatic cells contained comparable numbers of de novo copy number variations. In contrast, DNA methylation and transcriptome profiles of NT ES cells corresponded closely to those of IVF ES cells, whereas iPS cells differed and retained residual DNA methylation patterns typical of parental somatic cells. Thus, human somatic cells can be faithfully reprogrammed to pluripotency by SCNT and are therefore ideal for cell replacement therapies.

Towards germline gene therapy of inherited mitochondrial diseases.

Mutations in mitochondrial DNA (mtDNA) are associated with severe human diseases and are maternally inherited through the egg's cytoplasm. Here we investigated the feasibility of mtDNA replacement in human oocytes by spindle transfer (ST; also called spindle-chromosomal complex transfer). Of 106 human oocytes donated for research, 65 were subjected to reciprocal ST and 33 served as controls. Fertilization rate in ST oocytes (73%) was similar to controls (75%); however, a significant portion of ST zygotes (52%) showed abnormal fertilization as determined by an irregular number of pronuclei. Among normally fertilized ST zygotes, blastocyst development (62%) and embryonic stem cell isolation (38%) rates were comparable to controls. All embryonic stem cell lines derived from ST zygotes had normal euploid karyotypes and contained exclusively donor mtDNA. The mtDNA can be efficiently replaced in human oocytes. Although some ST oocytes displayed abnormal fertilization, remaining embryos were capable of developing to blastocysts and producing embryonic stem cells similar to controls.

Generation of iPSCs from cultured human malignant cells.

Induced pluripotent stem cells (iPSCs) can be generated from various differentiated cell types by the expression of a set of defined transcription factors. So far, iPSCs have been generated from primary cells, but it is unclear whether human cancer cell lines can be reprogrammed. Here we describe the generation and characterization of iPSCs derived from human chronic myeloid leukemia cells. We show that, despite the presence of oncogenic mutations, these cells acquired pluripotency by the expression of 4 transcription factors and underwent differentiation into cell types derived of all 3 germ layers during teratoma formation. Interestingly, although the parental cell line was strictly dependent on continuous signaling of the BCR-ABL oncogene, also termed oncogene addiction, reprogrammed cells lost this dependency and became resistant to the BCR-ABL inhibitor imatinib. This finding indicates that the therapeutic agent imatinib targets cells in a specific epigenetic differentiated cell state, and this may contribute to its inability to fully eradicate disease in chronic myeloid leukemia patients.

CDX2 in the formation of the trophectoderm lineage in primate embryos.

The first lineage decision during mammalian development is the establishment of the trophectoderm (TE) and the inner cell mass (ICM). The caudal-type homeodomain protein Cdx2 is implicated in the formation and maintenance of the TE in the mouse. However, the role of CDX2 during early embryonic development in primates is unknown. Here, we demonstrated that CDX2 mRNA levels were detectable in rhesus monkey oocytes, significantly upregulated in pronuclear stage zygotes, diminished in early cleaving embryos but restored again in compact morula and blastocyst stages. CDX2 protein was localized to the nucleus of TE cells but absent altogether in the ICM. Knockdown of CDX2 in monkey oocytes resulted in formation of early blastocyst-like embryos that failed to expand and ceased development. However, the ICM lineage of CDX2-deficient embryos supported the isolation of functional embryonic stem cells. These results provide evidence that CDX2 plays an essential role in functional TE formation during primate embryonic development.

YAP1 increases organ size and expands undifferentiated progenitor cells.

The mechanisms that regulate mammalian organ size are poorly understood. It is unclear whether the pathways that control organ size also impinge on stem/progenitor cells. A highly expressed gene in stem cells is YAP1, the ortholog of Drosophila Yorkie, a downstream component of the Hippo pathway. Mutations in components of this pathway produce tissue overgrowth phenotypes in the fly whereas mammalian orthologs, like salvador, merlin, LATS, and YAP1, have been implicated in tumorigenesis. We report here that YAP1 increases organ size and causes aberrant tissue expansion in mice. YAP1 activation reversibly increases liver size more than 4-fold. In the intestine, expression of endogenous YAP1 is restricted to the progenitor/stem cell compartment, and activation of YAP1 expands multipotent undifferentiated progenitor cells, which differentiate upon cessation of YAP1 expression. YAP1 stimulates Notch signaling, and administration of gamma-secretase inhibitors suppressed the intestinal dysplasia caused by YAP1. Human colorectal cancers expressing higher levels of YAP1 share molecular aspects with YAP1-induced dysplastic growth in the mouse. Our data show that the Hippo signaling pathway regulates organ size in mammals and can act on stem cell compartments, indicating a potential link between stem/progenitor cells, organ size, and cancer.

Discovery of a novel imprinted gene by transcriptional analysis of parthenogenetic embryonic stem cells.

BACKGROUND: Parthenogenetic embryonic stem cells (PESCs) may have future utilities in cell replacement therapies since they are closely related to the female from which the activated oocyte was obtained. Furthermore, the avoidance of parthenogenetic development in mammals provides the most compelling rationale for the evolution of genomic imprinting, and the biological process of parthenogenesis raises complex issues regarding differential gene expression. METHODS AND RESULTS: We describe here homozygous rhesus monkey PESCs derived from a spontaneously duplicated, haploid oocyte genome. Since the effect of homozygosity on PESCs pluripotency and differentiation potential is unknown, we assessed the similarities and differences in pluripotency markers and developmental potential by in vitro and in vivo differentiation of homozygous and heterozygous PESCs. To understand the differences in gene expression regulation between parthenogenetic and biparental embryonic stem cells (ESCs), we conducted microarray analysis of genome-wide mRNA profiles of primate PESCs and ESCs derived from fertilized embryos using the Affymetrix Rhesus Macaque Genome array. Several known paternally imprinted genes were in the highly down-regulated group in PESCs compared with ESCs. Furthermore, allele-specific expression analysis of other genes whose expression is also down-regulated in PESCs, led to the identification of one novel imprinted gene, inositol polyphosphate-5-phosphatase F (INPP5F), which was exclusively expressed from a paternal allele. CONCLUSION: Our findings suggest that PESCs could be used as a model for studying genomic imprinting, and in the discovery of novel imprinted genes.

DNMT3B expression might contribute to CpG island methylator phenotype in colorectal cancer.

PURPOSE: DNA methyltransferase-3B (DNMT3B) plays an important role in de novo CpG island methylation. Dnmt3b can induce colon tumor in mice with methylation in specific CpG islands. We hypothesized that cellular DNMT3B level might influence the occurrence of widespread CpG island methylation (i.e., the CpG island methylator phenotype, CIMP) in colon cancer. EXPERIMENTAL DESIGN: Utilizing 765 colorectal cancers in two cohort studies, we detected DNMT3B expression in 116 (15%) tumors by immunohistochemistry. We assessed microsatellite instability, quantified DNA methylation in repetitive long interspersed nucleotide element-1 (LINE-1) by Pyrosequencing, eight CIMP-specific promoters [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1], and eight other CpG islands (CHFR, HIC1, IGFBP3, MGMT, MINT1, MINT31, p14, and WRN) by real-time PCR (MethyLight). RESULTS: Tumoral DNMT3B overexpression was significantly associated with CIMP-high [> or =6/8 methylated CIMP-specific promoters; odds ratio (OR), 3.34; 95% confidence interval, 2.11-5.29; P < 0.0001]. The relations between DNMT3B and methylation in 16 individual CpG islands varied substantially (OR, 0.80-2.96), suggesting variable locus-to-locus specificities of DNMT3B activity. DNMT3B expression was not significantly related with LINE-1 hypomethylation. In multivariate logistic regression, the significant relation between DNMT3B and CIMP-high persisted (OR, 2.39; 95% confidence interval, 1.11-5.14; P = 0.026) after adjusting for clinical and other molecular features, including p53, beta-catenin, LINE-1, microsatellite instability, KRAS, PIK3CA, and BRAF. DNMT3B expression was unrelated with patient outcome, survival, or prognosis. CONCLUSIONS: Tumoral DNMT3B overexpression is associated with CIMP-high in colorectal cancer. Our data support a possible role of DNMT3B in nonrandom de novo CpG island methylation leading to colorectal cancer.

Heterozygous embryonic stem cell lines derived from nonhuman primate parthenotes.

Monoparental parthenotes represent a potential source of histocompatible stem cells that should be isogenic with the oocyte donor and therefore suitable for use in cell or tissue replacement therapy. We generated five rhesus monkey parthenogenetic embryonic stem cell (PESC) lines with stable, diploid female karyotypes that were morphologically indistinguishable from biparental controls, expressed key pluripotent markers, and generated cell derivatives representative of all three germ layers following in vivo and in vitro differentiation. Interestingly, high levels of heterozygosity were observed at the majority of loci that were polymorphic in the oocyte donors. Some PESC lines were also heterozygous in the major histocompatibility complex region, carrying haplotypes identical to those of the egg donor females. Expression analysis revealed transcripts from some imprinted genes that are normally expressed from only the paternal allele. These results indicate that limitations accompanying the potential use of PESC-derived phenotypes in regenerative medicine, including aberrant genomic imprinting and high levels of homozygosity, are cell line-dependent and not always present. PESC lines were derived in high enough yields to be practicable, and their derivatives are suitable for autologous transplantation into oocyte donors or could be used to establish a bank of histocompatible cell lines for a broad spectrum of patients.

Assessment of two automated imaging systems in evaluating estrogen receptor status in breast carcinoma.

Immunohistochemical staining for estrogen receptor (ER) status is widely used in the management of breast cancer. These stains have traditionally been scored manually, which results in generally good agreement among observers when the cases are strongly positive. However, significant interobserver and intraobserver differences in scoring can occur in borderline or weakly staining cases. Recently, automated systems have been proposed to provide a more sensitive and objective method of ER quantification. The ChromaVision Automated Cellular Imaging System and the Applied Imaging Ariol SL-50 quantify the color intensity of the immunoreactive product. To assess the accuracy of these 2 automated systems and to compare them to one another and to manual scoring, we performed immunostaining for ER on 64 cases of breast cancer. The percentages of positive cells were scored manually by 4 pathologists and by the 2 imaging systems. A discrepancy in scoring was defined as that which resulted in the reclassification of a case from negative to positive or vice versa. Our results showed significant agreement between the 2 automated systems. When automated scores were compared with the manual scores, only 5 of the 64 cases (7%) were discrepant. In 4 of these, the percentage of cells staining for ER was low (0% to 20%). Overall, the 2 systems were comparable, and discrepant results were most frequently seen when analyzing tumors with low levels of ER positive cells.

Pulmonary hypertension in sickle cell hemoglobinopathy: a clinicopathologic study of 20 cases.

Pulmonary hypertension is one of the major causes of morbidity and mortality of patients with sickle cell hemoglobinopathy (SCH). Although a clinically recognized complication of sickle cell disease (SCD), there are few published pathologic studies of pulmonary findings in these patients. The aim of this study was to define the pulmonary pathologic changes and to investigate correlation between the pathologic changes, the antemortem diagnosis of pulmonary hypertension, and the severity of SCH. Cases of SCH were identified from the autopsy database using Snomed codes. Clinical and echocardiograph data were collected for correlation with the pathologic data. A total of 20 adult patients (12 males and 8 females) were identified. Hemoglobin electrophoresis results were available for 16 patients, with hemoglobin S fraction percentages ranging from 23% to 97.8%. Eleven patients had SCD, 5 patients had sickle cell trait (SCT), and the remaining 4 patients without hemoglobin electrophoresis were included in the SCT group. The mean age of the SCT group was higher than that of the SCD group (P = 0.03). Histologically, all 20 patients demonstrated changes in pulmonary vasculature considered diagnostic of pulmonary hypertension grade I to grade IV, associated with plexiform lesions in 60% of patients. Medial hypertrophy and intimal hyperplasia/fibrosis, considered potentially reversible lesions, were seen in all patients. A weak association was found between SCD and plexiform lesions. Fibroelastic degeneration of small arteries, arterioles, and venules was identified in almost all (95%) cases. Clinically, tricuspid regurgitation was detected by echocardiogram in 10 of 20 (50%) patients; 6 of these 10 had significant regurgitation to allow estimation of systolic pressure. Sudden death occurred in 8 patients, with males having a significantly higher incidence. Cardiomegaly was present in 95% of patients, however, autosplenectomy and hepatic cirrhosis/hemochromatosis were observed almost exclusively in patients with SCD. Cirrhosis was found to have a strong positive association with SCD. This study demonstrates pulmonary hypertensive changes in all 20 autopsied patients who had SCH but died from various causes. We conclude that a high prevalence of pulmonary hypertension is associated with SCH with consequent high mortality. Therefore, patients with SCH would benefit from a regular periodic assessment for pulmonary hypertension regardless of age, sex, and severity of hemoglobinopathy.

Effect of decalcification on the immunohistochemical expression of ABH blood group isoantigens.

Immunohistochemical stains for ABH blood group antigens were recently shown to be useful ancillary tools for sorting out specimen mix-ups in surgical pathology, irrespective of the fixatives used. However, the effects of decalcification on the expression of these antigens are not known. Therefore, to examine the validity of using ABH blood group immunohistochemistry in decalcified tissues, we studied the immunohistochemical expression of ABH blood group antigens in B5-fixed, decalcified, paraffin-embedded archival bone marrow specimens from 43 consecutive patients (13 blood group A, 6 group B, 20 group O, and 4 group AB). Immunohistochemical staining for A, B, and H blood group antigens was performed with monoclonal antibodies and an avidin-biotin detection method with citrate antigen retrieval. The results of immunohistochemistry were correlated with patients' blood groups as determined by serology. Immunohistochemical expression of the A and B blood group antigens with good staining intensity was detected in erythrocytes and endothelial cells. The immunoreactivity for H blood group antigen was attenuated by the decalcification process and could not be enhanced with citrate antigen retrieval. However, in all 43 cases, the A and B antigen staining pattern was concordant with patients' blood groups as determined with serology. These results show that decalcification does not have adverse effects on immunohistochemical expression of the A and B blood group antigens in tissue sections but may nullify the expression of H isoantigen. However, based on A and B immunoreactivity patterns, immunostaining for ABH blood group antigens can be helpful in resolving problems of specimen mix-ups and tissue floaters in decalcified specimens.

Effect of tissue fixatives on the immunohistochemical expression of ABH blood group isoantigens.

Immunohistochemical analysis of ABH blood group isoantigens has been shown to be a useful ancillary technique for resolving problems associated with specimen mix-ups in the daily practice of surgical pathology. However, the effects of different fixatives on the expression of these antigens in paraffin-embedded tissues are not known. Therefore, the effects of seven different fixatives on the immunohistochemical expression of ABH blood group isoantigens were studied in tissues from several organs. The following fixatives were used: acetone, 70% ethanol, B5, Bouin, Carnoy, methanol, and 10% formalin. After fixation for 6, 12, and 72 hours, the tissue blocks were embedded in paraffin, and immunohistochemistry was performed on 4 microm-thick tissue sections using monoclonal antibodies to blood group isoantigens (A, B, and H) and the avidin-biotin detection method. Also, immunostaining was performed on step tissue sections with and without antigen retrieval using citrate buffer at pH 6.0. The expression of the blood group isoantigens was concordant with the blood group of the patient in all the cases studied, irrespective of the fixative and time of fixation. However, in the absence of antigen retrieval, the intensity of the staining reaction was diminished. These results showed that irrespective of the fixative used, immunohistochemical staining of paraffin-embedded tissue sections with ABH blood group antibodies is a rapid, reliable, and cost-effective method for sorting out interpretative problems of tissue contaminants (floaters) and specimen mix-ups in surgical pathology.

Wegener's granulomatosis diagnosed by testicular biopsy.

Urogenital involvement, other than the kidneys, is extremely rare in Wegener's granulomatosis (WG) and occurs in less than 1% of the cases. When encountered it is confined to prostate, bladder, urethra, cervix, and vagina. Granulomatous infiltration of the testis from WG has not been cited in the medical literature. We report a case of WG in a Hispanic male who presented with sensorineural hearing loss and hemoptysis. He had a pulmonary lesion and a painless right testicular mass, which was found to have necrotizing granulomas on excisional biopsy. This may be the first reported case of WG diagnosed by testicular biopsy as testicular involvement is rare in WG. We believe that the actual incidence of testicular involvement in WG may be higher as genital examination may be ignored during routine physical examinations.

FISH for HER-2/neu in breast cancer: standardization makes the difference!

CONTEXT: Overexpression of HER-2/neu oncogene in breast cancer patients is correlated with disease free survival (DFS) and overall survival (OS). The most commonly used methods for the detection of HER-2/neu status are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). However, therse is a lot of controversy with regard to the best method. Most of the FISH studies chose arbitrary cut-off levels for positive results (10%) and had no validation. AIM: In order to address these issues, we designed a pilot study of 38 samples with known IHC status representing all 4 categories. SETTINGS AND DESIGN: FISH was performed using Vysis Pathvysion probe. For validation, 5 cases of reduction mammoplasty were analyzed using same protocols. RESULTS: Our results showed significant discordance between FISH and IHC. The rate of discordance was much higher in the 0, 1+, and 2+ categories compared to published literature. This could be due to the lower cut-off rates for positive amplification established by validation in our study (5.7% vs 10%). Our analysis showed that FISH positive and IHC negative patients have a poor prognosis in terms of DFS and OS compared to FISH negative and IHC negative patients. Further, our results also showed that IHC in comparison to FISH has a comparable specificity (98%), but has a very low sensitivity (46%). CONCLUSION: Based on these results, we consider FISH to be the gold standard for detecting HER-2/neu status in breast cancer.

Oct4 expression is not required for mouse somatic stem cell self-renewal.

The Pou domain containing transcription factor Oct4 is a well-established regulator of pluripotency in the inner cell mass of the mammalian blastocyst as well as in embryonic stem cells. While it has been shown that the Oct4 gene is inactivated through a series of epigenetic modifications following implantation, recent studies have detected Oct4 activity in a variety of somatic stem cells and tumor cells. Based on these observations it has been suggested that Oct4 may also function in maintaining self-renewal of somatic stem cells and, in addition, may promote tumor formation. We employed a genetic approach to determine whether Oct4 is important for maintaining pluripotency in the stem cell compartments of several somatic tissues including the intestinal epithelium, bone marrow (hematopoietic and mesenchymal lineages), hair follicle, brain, and liver. Oct4 gene ablation in these tissues revealed no abnormalities in homeostasis or regenerative capacity. We conclude that Oct4 is dispensable for both self-renewal and maintenance of somatic stem cells in the adult mammal.

Dnmt3b promotes tumorigenesis in vivo by gene-specific de novo methylation and transcriptional silencing.

Increased methylation of CpG islands and silencing of affected target genes is frequently found in human cancer; however, in vivo the question of causality has only been addressed by loss-of-function studies. To directly evaluate the role and mechanism of de novo methylation in tumor development, we overexpressed the de novo DNA methyltransferases Dnmt3a1 and Dnmt3b1 in Apc Min/+ mice. We found that Dnmt3b1 enhanced the number of colon tumors in Apc Min/+ mice approximately twofold and increased the average size of colonic microadenomas, whereas Dnmt3a1 had no effect. The overexpression of Dnmt3b1 caused loss of imprinting and increased expression of Igf2 as well as methylation and transcriptional silencing of the tumor suppressor genes Sfrp2, Sfrp4, and Sfrp5. Importantly, we found that Dnmt3b1 but not Dnmt3a1 efficiently methylates the same set of genes in tumors and in nontumor tissues, demonstrating that de novo methyltransferases can initiate methylation and silencing of specific genes in phenotypically normal cells. This suggests that DNA methylation patterns in cancer are the result of specific targeting of at least some tumor suppressor genes rather than of random, stochastic methylation followed by clonal selection due to a proliferative advantage caused by tumor suppressor gene silencing.

Panhemispheric infarction: a complication of cuffed catheter.

The need for reliable vascular access remains the Achilles heel of hemodialysis. Complications of vascular access are a leading cause of morbidity and mortality in patients who undergo hemodialysis, especially in those patients with end-stage renal disease. Among methods of vascular access, arteriovenous fistulae have the lowest rate of infection and should be the access of choice when vascular anatomy permits. Also, the incidence of staphylococcal infections in patients infected with human immunodeficiency virus is increasing. To emphasize the need to use arteriovenous fistula access for hemodialysis whenever possible, we report the case of a patient with end-stage renal disease and human immunodeficiency virus infection who died as a result of panhemispheric infarction and uncal herniation as a result of fulminant staphylococcal bacteremia caused by central venous catheter sepsis.