698 research outputs found
Increased microtubule assembly rates influence chromosomal instability in colorectal cancer cells
No full textChromosomal instability (CIN) is defined as the perpetual missegregation of whole chromosomes during mitosis and represents a hallmark of human cancer. However, the mechanisms influencing CIN and its consequences on tumour growth are largely unknown. We identified an increase in microtubule plus-end assembly rates as a mechanism influencing CIN in colorectal cancer cells. This phenotype is induced by overexpression of the oncogene AURKA or by loss of the tumour suppressor gene CHK2, a genetic constitution found in 73% of human colorectal cancers. Increased microtubule assembly rates are associated with transient abnormalities in mitotic spindle geometry promoting the generation of lagging chromosomes and influencing CIN. Reconstitution of proper microtubule assembly rates by chemical or genetic means suppresses CIN and thereby, unexpectedly, accelerates tumour growth in vitro and in vivo. Thus, we identify a fundamental mechanism influencing CIN in cancer cells and reveal its adverse consequence on tumour growth
The putative oncogene CEP72 inhibits the mitotic function of BRCA1 and induces chromosomal instability
No full textBRCA1 is a tumor-suppressor gene associated with, but not restricted to, breast and ovarian cancer and implicated in various biological functions. During mitosis, BRCA1 and its positive regulator Chk2 are localized at centrosomes and are required for the regulation of microtubule plus end assembly, thereby ensuring faithful mitosis and numerical chromosome stability. However, the function of BRCA1 during mitosis has not been defined mechanistically. To gain insights into the mitotic role of BRCA1 in regulating microtubule assembly, we systematically identified proteins interacting with BRCA1 during mitosis and found the centrosomal protein Cep72 as a novel BRCA1-interacting protein. CEP72 is frequently upregulated in colorectal cancer tissues and overexpression of CEP72 mirrors the consequences of BRCA1 loss during mitosis. In detail, the overexpression of CEP72 causes an increase in microtubule plus end assembly, abnormal mitotic spindle formation and the induction of chromosomal instability. Moreover, we show that high levels of Cep72 counteract Chk2 as a positive regulator of BRCA1 to ensure proper mitotic microtubule assembly. Thus, CEP72 represents a putative oncogene in colorectal cancer that might negatively regulate the mitotic function of BRCA1 to ensure chromosomal stability.Deutsche Forschungsgemeinschaft; DF
Phosphorylation of AKT(Ser473) serves as an independent prognostic marker for radiosensitivity in advanced head and neck squamous cell carcinoma
No full textHead and neck squamous cell carcinoma (HNSCC) is frequently characterized by high resistance to radiotherapy, which critically depends on both altered signaling pathways within tumor cells and their dynamic interaction with the tumor microenvironment. This study evaluated the prognostic value of the phosphorylation status of AKT on Ser473 and Thr308 for the clinical outcome of patients with advanced HNSCC on radiotherapy. Furthermore, we investigated the impact of AKT(Ser473) phosphorylation [p-AKT(Ser473)] in the context of radioresistance using ex vivo tissue cultures that resemble the complex tissue architecture and paracrine interaction with the tumor microenvironment. In a cohort of 120 patients with advanced HNSCC, who were treated with primary or adjuvant radiotherapy, a significant association was found between relative p-AKT(Ser473) levels and overall survival (p = 0.006) as well as progression-free survival (p = 0.021), while no significant correlation was revealed for relative p-AKT(Thr308) levels. In ex vivo tissue cultures p-AKT(Ser473) levels were increased upon irradiation and treatment with the PI3K inhibitor LY294002 inhibited both basal and irradiation induced AKT(Ser473) phosphorylation. Strikingly, pretreatment with LY294002 sensitized tissue cultures derived from primary and recurrent tumors to radiotherapy as determined by impaired tumor cell proliferation and enhanced DNA damage. In conclusion, phosphorylation status of AKT(Ser473) in tumor specimens serves as a novel biomarker to identify patients with advanced HNSCC at high risk for treatment failure following radiotherapy, and our data from ex vivo tissue cultures support the assumption that pharmacological inhibition of AKT(Ser473) phosphorylation might circumvent radioresistance to improve efficiency and reduce toxicity of current treatment modalities
Cortactin expression: Association with disease progression and survival in oral squamous cell carcinoma
No full textCortactin (CTTN) is located on chromosome 11q13 and is associated with invasiveness in various cancer entities. CTTN protein expression could be a prognosticator of oral squamous cell carcinoma (OSCC) in terms of recurrence and survival
Somatostatin receptor expression related to TP53 and RB1 alterations in pancreatic and extrapancreatic neuroendocrine neoplasms with a Ki67-index above 20⁒
No full textSomatostatin receptor 2A expression is a feature of well-differentiated neuroendocrine neoplasms and is important for their diagnosis and therapy. Little is known about somatostatin receptor 2A expression in poorly differentiated neuroendocrine neoplasms in relation to TP53 and RB1 status and how these features may contribute to the separation of well from poorly differentiated neuroendocrine neoplasms with a proliferation index above 20%. This study investigates the expression of somatostatin receptors, p53 and Rb1, and TP53 alterations in pancreatic and extrapancreatic well and poorly differentiated neuroendocrine neoplasms (Ki67-index >20%). Thirty-seven poorly differentiated neuroendocrine neoplasms of pancreatic (n=12) and extrapancreatic origin (n=25) as well as 10 well-differentiated neuroendocrine neoplasms of the pancreas (n=9) and rectum (n=1) with a Ki67-index >20% were immunostained for synaptophysin, chromogranin A, Ki67, CD56, p53, Rb1, ATRX, DAXX, progesterone receptor, somatostatin receptor 2A, somatostatin receptor 5, and cytokeratin 20, and sequenced for TP53, exons 5-9. Somatostatin receptor 2A was positive in 6/37 of poorly differentiated and in 8/10 of well-differentiated neuroendocrine neoplasms. One well-differentiated and two poorly differentiated neuroendocrine neoplasms expressed somatostatin receptor 5. Abnormal nuclear p53 and Rb1 staining was found in 29/37 and 22/37 poorly differentiated neuroendocrine neoplasms, respectively, whereas all well-differentiated neuroendocrine neoplasms showed normal p53 and Rb1 expression. TP53 gene alterations were restricted to poorly differentiated neuroendocrine neoplasms (24/34) and correlated well with p53 expression. All cases were progesterone receptor negative. Somatostatin receptor 2A expression is not limited to well-differentiated neuroendocrine neoplasms but also occurs in 16% of poorly differentiated neuroendocrine neoplasms from various sites. Most poorly differentiated neuroendocrine neoplasms are characterized by TP53 alterations and Rb1 loss, usually in the absence of somatostatin receptor 2A expression. In the pancreas, these criteria contribute to separate well-differentiated neuroendocrine neoplasms with a Ki67-index above 20% from poorly differentiated neuroendocrine neoplasms.Modern Pathology advance online publication, 6 January 2017; doi:10.1038/modpathol.2016.217
Fokal segmentale Glomerulosklerose und juxtaglomerulärer Apparat der hypertensiven "fawn-hooded" Ratte
No full textIn dieser Arbeit wurden 8 und 16 Wochen alte, hypertensive "fawn-hooded" Ratten (FHH8, FHH16) mit genetisch ähnlichen 16 Wochen alten "fawn-hooded" Ratten mit nur geringgradiger Blutdruckerhöhung (FHL16, Kontrollgruppe) hinsichtlich der pathologisch-anatomischen Veränderungen der Nierenmorphologie und hinsichtlich der Expression von NO-Synthase-1 (NOS1), Cyclooxygenase-2 (COX-2) und Renin am juxtaglomerulären Apparat (JGA) verglichen. Die histopathologischen Veränderungen bei FHH16 umfassten die klassischen Schädigungszeichen der fokal segmentalen Glomerulosklerose (FSGS) mit fokaler Überexpression von Kollagen IV und eine moderate Arteriolopathie. Bei FHH8 ließen sich, wie bei FHL16 keine morphologischen Schädigungen nachweisen. Die NOS1-Aktivität an der Macula densa, untersucht mittels der NADPH-Diaphorasereaktion und die NOS1 mRNA Expression waren bei FHH8 (+153 and +88%; P < 0.05) und FHH16 (+93 and +98%; P < 0.05) im Vergleich zu FHL16 signifikant erhöht. Eine gleichgerichtete signifikante Erhöhung zeigte sich für die COX-2-Expression an der Macula densa von FHH8 (+166%; P < 0.05) und FHH16 (+157%; P < 0.05) im Vergleich zu FHL16. Des weiteren ließ sich eine signifikante, ebenfalls gleichgerichtete Überexpression von Renin in der afferenten Arteriole auf Protein- und mRNA-Ebene bei FHH8 (+51 and +166%; P < 0.05) und FHH16 (+105 and +136%; P < 0.05) im Vergleich zu FHL16 nachweisen. Somit konnte gezeigt werden, dass die gleichgerichtete Überexpression von NOS1, COX-2 und Renin am JGA bei der FHH-Ratte der Entwicklung einer fokal segmentalen Glomerulosklerose vorausgeht und damit möglicherweise pathogenetische Bedeutung für die Entstehung der Nierenschädigung bei diesem Rattenstamm hat.This study describes elevated histochemical signals for nitric oxide synthase-1 (NOS1) and cyclooxygenase-2 (COX-2) in juxtaglomerular apparatus (JGA) and adjacent thick ascending limb of the kidney of fawn-hooded hypertensive rats (FHH). Two different age groups of FHH (8 and 16 wk; FHH8 and FHH16, respectively) were compared with genetically related fawn-hooded rats with close to normal blood pressure (FHL) that served as controls. Histopathological changes in FHH16 comprised focal segmental glomerulosclerosis (FSGS), focal matrix overexpression (mainly of collagen IV), and a moderate arteriolopathy with hypertrophy of the media, enhanced immunoreactivity for alpha-smooth muscle actin, and altered distribution of myofibrils. Macula densa NOS activity, as expressed by NADPH-diaphorase staining, and NOS1 mRNA abundance were significantly elevated in FHH8 (+153 and +88%; P < 0.05) and FHH16 (+93 and +98%; P < 0.05), respectively. Even higher elevations were registered for COX-2 immunoreactivity in FHH8 (+166%; P < 0.05) and FHH16 (+157%; P < 0.05). The intensity of renin immunoreactivity and renin mRNA expression in afferent arterioles was also elevated in FHH8 (+51 and +166%; P < 0.05) and FHH16 (+105 and +136%; P < 0.05), respectively. Thus we show that coordinate upregulation of tubular NOS1, COX-2, and renin expression precedes, and continues after, the manifestation of glomerulosclerotic damage in FHH. These observations may have implications in understanding the role of local paracrine mediators in glomerular disease
Impaired aldehyde dehydrogenase 1 subfamily member 2A-dependent retinoic acid signaling is related with a mesenchymal-like phenotype and an unfavorable prognosis of head and neck squamous cell carcinoma
No full textBackground: An inverse correlation between expression of the aldehyde dehydrogenase 1 subfamily A2 (ALDH1A2) and gene promoter methylation has been identified as a common feature of oropharyngeal squamous cell carcinoma (OPSCC). Moreover, low ALDH1A2 expression was associated with an unfavorable prognosis of OPSCC patients, however the causal link between reduced ALDH1A2 function and treatment failure has not been addressed so far. Methods: Serial sections from tissue microarrays of patients with primary OPSCC (n = 101) were stained by immunohistochemistry for key regulators of retinoic acid (RA) signaling, including ALDH1A2. Survival with respect to these regulators was investigated by univariate Kaplan-Meier analysis and multivariate Cox regression proportional hazard models. The impact of ALDH1A2-RAR signaling on tumor-relevant processes was addressed in established tumor cell lines and in an orthotopic mouse xenograft model. Results: Immunohistochemical analysis showed an improved prognosis of ALDH1A2high OPSCC only in the presence of CRABP2, an intracellular RA transporter. Moreover, an ALDH1A2highCRABP2high staining pattern served as an independent predictor for progression-free (HR: 0.395, p = 0.007) and overall survival (HR: 0.303, p = 0.002), suggesting a critical impact of RA metabolism and signaling on clinical outcome. Functionally, ALDH1A2 expression and activity in tumor cell lines were related to RA levels. While administration of retinoids inhibited clonogenic growth and proliferation, the pharmacological inhibition of ALDH1A2-RAR signaling resulted in loss of cell-cell adhesion and a mesenchymal-like phenotype. Xenograft tumors derived from FaDu cells with stable silencing of ALDH1A2 and primary tumors from OPSCC patients with low ALDH1A2 expression exhibited a mesenchymal-like phenotype characterized by vimentin expression. Conclusions: This study has unraveled a critical role of ALDH1A2-RAR signaling in the pathogenesis of head and neck cancer and our data implicate that patients with ALDH1A2low tumors might benefit from adjuvant treatment with retinoids
Aberrant DNA methylation patterns in microsatellite stable human colorectal cancers define a new marker panel for the CpG island methylator phenotype
No full textA distinct group of colorectal carcinomas (CRCs) referred to as the "CpG island methylator phenotype" (CIMP) shows an extremely high incidence of de novo DNA methylation and may share common pathological, clinical or molecular features. However, there is limited consensus about which CpG islands (CGIs) define a CIMP, particularly in microsatellite stable (MSS) carcinomas. To study this phenotype in a systematic manner, we analyzed genome-wide CGI DNA methylation profiles of 19 MSS CRC using methyl-CpG immunoprecipitation (MCIp) and hybridization on 244K CGI oligonucleotide microarrays, determined KRAS and BRAF mutation status and compared disease-related DNA methylation changes to chromosomal instability as detected by microarray-based comparative genomic hybridization. Results were validated using mass spectrometry analysis of bisulfite-converted DNA at a subset of 76 individual CGIs in 120 CRC and 43 matched normal tissue samples. Both genome-wide profiling and CpG methylation fine mapping segregated a group of CRC showing pronounced and frequent de novo DNA methylation of a distinct group of CGIs that only partially overlapped with previously established classifiers. The CIMP group defined in our study revealed significant association with colon localization, either KRAS or BRAF mutation, and mostly minor chromosomal losses but no association with known histopathological features. Our data provide a basis for defining novel marker panels that may enable a more reliable classification of CIMP in all CRCs, independently of the MS status
Characterization of paraganglioma-like neuroendocrine tumors of the pancreas
No full textDas Ziel dieser Doktorarbeit ist die ausführliche Charakterisierung von paragangliomartigen neuroendokrinen Tumoren des Pankreas. Dabei soll untersucht werden, inwiefern ein paragangliomartiges Wachstumsmuster von pankreatischen neuroendokrinen Tumoren (PanNETs) mit der Produktion von Hormonen assoziiert ist. Es handelt sich um eine experimentelle Studie mit insgesamt 68 Fällen. Zusammenfassend kann gesagt werden, dass PanNETs mit einem paragangliomartigen Wachstumsmuster statistisch signifikant mit der Produktion von Somatostatin assoziiert sind.The aim of this thesis is to present a detailed characterization of paraganglioma-like neuroendocrine tumors of the pancreas, and to investigate to what extent a paraganglioma-like growth pattern of pancreatic neuroendocrine tumors (PanNETs) is associated with the production of hormones. It is an experimental study with a total of 68 cases. In summary, PanNETs with a paraganglioma-like growth pattern are statistically significantly associated with the production of somatostatin
Pancreatic neuroendocrine carcinomas reveal a closer relationship to ductal adenocarcinomas than to neuroendocrine tumors G3
No full textPancreatic neuroendocrine carcinoma is a rare aggressive tumor commonly harboring TP53 and RB1 alterations and lacking neuroendocrine related genetic changes such as mutations in MEN1 and ATRX/DAXX. Little is known about its genetic profile with regard to that of pancreatic ductal adenocarcinoma. We therefore conducted a detailed genetic study in 12 pancreatic neuroendocrine carcinomas of large cell (n=9) and small cell type (n=3) using massive parallel sequencing applying a 409 gene panel on an Ion Torrent system. The genetic data were compared with known data of pancreatic ductal adenocarcinoma and correlated with exocrine lineage marker expression. A similar analysis was performed in 11 pancreatic neuroendocrine tumors G3. Neuroendocrine carcinomas harbored 63 somatic mutations in 45 different genes, affecting most commonly TP53 (8/12 cases), KRAS (5/12 cases) and RB1 (loss of expression with or without deletion in 4/12 cases). Five carcinomas had both TP53 and KRAS mutations. Neuroendocrine tumors G3 only shared singular mutations in five different genes with neuroendocrine carcinomas, including TP53, CDKN2A, ARID1A, LRP1B and APC, affecting five different cases. Most KRAS positive neuroendocrine carcinomas also expressed MUC1 (4/5) and carcinoembryonic antigen (3/5) as markers of ductal differentiation. Our data indicate that almost half of the pancreatic neuroendocrine carcinomas are genetically and phenotypically related to pancreatic ductal adenocarcinoma, and might therefore respond to chemotherapies targeting the latter carcinomas
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