The human trithorax protein hASH2 functions as an oncoprotein.

Regulation of chromatin is an important aspect of controlling promoter activity and gene expression. Posttranslational modifications of core histones allow proteins associated with gene transcription to access chromatin. Closely associated with promoters of actively transcribed genes, trimethylation of histone H3 at lysine 4 (H3K4me3) is a core histone mark set by several protein complexes. Some of these protein complexes contain the trithorax protein ASH2 combined with the MLL oncoproteins. We identified human ASH2 in a complex with the oncoprotein MYC. This finding, together with the observation that hASH2 interacts with MLL, led us to test whether hASH2 itself is involved in transformation. We observed that hASH2 cooperates with Ha-RAS to transform primary rat embryo fibroblasts (REF). Furthermore, transformation of REFs by MYC and Ha-RAS required the presence of rAsh2. In an animal model, the hASH2/Ha-RAS-transformed REFs formed rapidly growing tumors characteristic of fibrosarcomas that, compared with tumors derived from MYC/Ha-RAS transformed cells, were poorly differentiated. This finding suggests that ASH2 functions as an oncoprotein. Although hASH2 expression at the mRNA level was generally not deregulated, hASH2 protein expression was increased in most human tumors and tumor cell lines. In addition, knockdown of hASH2 inhibited tumor cell proliferation. Taken together, these observations define hASH2 as a novel oncoprotein.

The vasoactive intestinal peptide receptor turnover in pulmonary arteries indicates an important role for VIP in the rat lung circulation.

Vasoactive intestinal peptide (VIP) is a potent vasorelaxing peptide that plays a role in lung physiology and possibly in pulmonary hypertension. We investigated the turnover of the VIP receptors on rat pulmonary arteries ex vivo. There was evidence for a fast receptor turnover in pulmonary arteries, which underlines the important role of VIP for the regulation of pulmonary circulation and pulmonary pathology.

Reduced cisplatin sensitivity of head and neck squamous cell carcinoma cell lines correlates with mutations affecting the COOH-terminal nuclear localization signal of p53.

PURPOSE: Head and neck squamous cell carcinomas (HNSCC) are the most frequent malignancies of the upper aerodigestive tract. Cisplatin resistance is a major problem in the treatment of a large number of HNSCC cancer patients. In this study, nine randomly selected HNSCC cell lines were investigated regarding expression, presence of mutations, nucleocytoplasmic distribution of p53, and sensitivity to cisplatin. EXPERIMENTAL DESIGN: Protein expression was evaluated by Western blot analysis. The whole open reading frame of p53 was determined by reverse transcription-PCR sequencing. Nucleocytoplasmic distribution was evaluated by confocal laser scanning microscopy. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay was used to test for cisplatin sensitivity. RESULTS: p53 mutations were found in all nine investigated HNSCC cell lines. Nuclear p53 signal was detected in six cell lines, whereas three cell lines exhibited total loss of nuclear p53 signal. Nuclear signal depended on the presence or absence of the COOH-terminal nuclear localization signal in p53. Cisplatin sensitivity was highly reduced in the group with loss of nuclear p53 signal compared with those with detectable nuclear signal. Transfection of wild-type and mutant p53 into a rat embryonic cell system showed highly reduced activity of the nuclear localization signal mutant p53 protein. CONCLUSION: Taken together, these data suggest that "loss of nuclear p53 signal" correlates with cisplatin resistance in HNSCC. If these results can be validated on a larger number of tumor samples, including fresh tumor tissues, it potentially could help in sparing a subgroup of HNSCC patients the side effects associated with unnecessary chemotherapy by identifying cisplatin nonresponders before chemotherapy induction.

PARP-10, a novel Myc-interacting protein with poly(ADP-ribose) polymerase activity, inhibits transformation.

The proto-oncoprotein c-Myc functions as a transcriptional regulator that controls different aspects of cell behavior, including proliferation, differentiation, and apoptosis. In addition, Myc proteins have the potential to transform cells and are deregulated in the majority of human cancers. Several Myc-interacting factors have been described that mediate part of Myc's functions in the control of cell behavior. Here, we describe the isolation of a novel 150 kDa protein, designated PARP-10, that interacts with Myc. PARP-10 possesses domains with homology to RNA recognition motifs and to poly(ADP-ribose) polymerases (PARP). Molecular modeling and biochemical analysis define a PARP domain that is capable of ADP-ribosylating PARP-10 itself and core histones, but neither Myc nor Max. PARP-10 is localized to the nuclear and cytoplasmic compartments that is controlled at least in part by a Leu-rich nuclear export sequence (NES). Functionally, PARP-10 inhibits c-Myc- and E1A-mediated cotransformation of rat embryo fibroblasts, a function that is independent of PARP activity but that depends on a functional NES. Together, our findings define a novel PARP enzyme involved in the control of cell proliferation.

Caspase-9 plays a marginal role in serum starvation-induced apoptosis.

Serum withdrawal represents a potent trigger to induce caspase-dependent apoptosis in a series of cell culture models. In rat 423-cells, caspase-8 and caspase-3 were apparently sufficient to initiate and proceed apoptosis without involving the intrinsic amplification loop via caspase-9. To assess the reasons for this inactivity of an otherwise crucial initiator caspase, we examined the ability for apoptosome assembly in 423-cells. Caspase-9 and Apaf-1 were expressed and cytochrome c released from mitochondria upon serum withdrawal. Although functional apoptosomes were assembled successfully in vitro, caspase-9 processing was found essentially refrained during apoptosis in 423-cells. Cell fractionation experiments revealed that sequestration of caspase-9 to cytoskeletal structures in 423-cells contributed to the observed impairment of apoptosome formation. Altogether, these findings provide evidence that serum starvation-induced apoptosis may occur independently of the intrinsic pathway and that caspase-9 sequestration potentially represents a novel biological antiapoptotic strategy.

bFGF rescues 423-cells from serum starvation-induced apoptosis downstream of activated caspase-3.

Serum withdrawal rapidly induces apoptosis in rat 423-cells, while addition of bFGF results in cell survival. However, surviving cells initially display morphological changes characteristic for apoptotic cells and even process caspases. Active caspase-3 was detected at the single-cell level in those finally bFGF-rescued cells, while mitochondrial integrity was maintained. Generation of cleavage products of caspase targets was confirmed in surviving cells. Proteome analysis indicated multi-faceted survival activities of bFGF including upregulation of inhibitor-of-apoptosis and heat shock protein family members directly interfering with caspases. Our data suggest that the "point-of-no-return" in death-induced cells has to be moved downstream of activated caspase-3.

Inhibitor of apoptosis protein (IAP) survivin is upregulated by oncogenic c-H-Ras.

Among the inhibitors of apoptosis proteins (IAPs), survivin has attracted special attention through its involvement in human cancer. The mechanism underlying tumour-associated survivin re-expression is not known. We found a correlation between exogenous c-H-Ras oncoprotein and endogenous survivin in a series of rat cell lines, which expressed defined oncogenes. Moreover, human HaCat cells, transfected with a constitutively activated c-H-ras gene, had significantly increased survivin levels. To study the interdependence of the two proteins, we generated a rat cell line that expressed a dexamethasone-inducible c-H-ras construct. Induction of c-H-Ras expression was followed by rapid upregulation of survivin. Conversely, downregulation of the oncoprotein resulted in prompt reduction of survivin to baseline value. c-H-Ras-induced survivin was expressed constitutively and independent of cell cycle progression or proliferation. Compromising Ras-stimulated PI3-K activity and MEK1 by chemicals abolished survivin expression and was associated with apoptotic cell death. Upregulation of survivin appeared to be an important activity of c-H-Ras oncoprotein, since cotransfection of a survivin-antisense construct into c-myc/c-H-ras-transfected primary rat embryo cells resulted in profound reduction of transformed clones. It is tempted to speculate that the frequent presence of survivin in human cancer cells might be a consequence of activated Ras-signalling pathways.

["Screening" in special situations. Assessing predictive genetic screening for hereditary breast and colorectal cancer]. / "Screening" in speziellen Situationen. Prädiktive humangenetische Diagnostik bei hereditärem Mamma- und Kolorektalkarzinom.

AIMS AND METHODS: The aim of this health technology assessment was to analyse the current scientific and genetic counselling on predictive genetic testing for hereditary breast and colorectal cancer. Predictive genetic testing will be available for several common diseases in the future and questions related to financial issues and quality standards will be raised. This report is based on a systematic/nonsystematic literature search in several databases (e.g. EmBase, Medline, Cochrane Library) and on a specific health technology assessment report (CCOHTA) and review (American Gastroenterological Ass.), respectively. Laboratory test methods, early detection methods and the benefit from prophylactic interventions were analysed and social consequences interpreted. BACKGROUND: Breast and colorectal cancer are counted among the most frequently cancer diseases. Most of them are based on random accumulation of risk factors, 5-10% show a familial determination. A hereditary modified gene is responsible for the increased cancer risk. In these families, high tumour frequency, young age at diagnosis and multiple primary tumours are remarkable. RESULTS AND REFLECTION: GENETIC DIAGNOSIS: Sequence analysis is the gold standard. Denaturing high performance liquid chromatography is a quick alternative method. The identification of the responsible gene defect in an affected family member is important. If the test result is positive there is an uncertainty whether the disease will develop or not, when and in which degree, which is founded in the geno-/phenotype correlation. The individual risk estimation is based upon empirical evidence. The test results affect the whole family. PREVENTION/EARLY DETECTION: Currently, primary prevention is possible for familial adenomatous polyposis (celecoxib, prophylactic colectomy) and for hereditary mamma carcinoma (prophylactic mastectomy). The so-called preventive medical check-ups are early detection examinations. The evidence about early detection methods for colorectal cancer is better than for breast cancer. PROPHYLACTIC SURGICAL INTERVENTIONS: Prophylactic mastectomy (PM) reduces the relative breast cancer risk by approximately 90%. The question is if PM has an impact on mortality. The acceptance of PM is culture-dependent. Colectomy can be used as a prophylactic (FAP) and therapeutic method. After surgery, the cancer risk remains high and so early detection examinations are still necessary. EVIDENCE-BASED STATEMENTS: The evidence is often fragmentary and of limited quality. For objective test result presentation information about sensitivity, specificity, positive predictive value, and number needed to screen and treat, respectively, are necessary. REFLECTIONS: New identification of mutations and demand will lead to an increase of predictive genetic counselling and testing. There is a gap between predictive genetic diagnosis and prediction, prevention, early detection and surgical interventions. These circumstances require a basic strategy. Since predictive genetic diagnosis is a very sensitive issue it is important to deal with it carefully in order to avoid inappropriate hopes. Thus, media, experts and politicians need to consider opportunities and limitations in their daily decision-making processes.