14-3-3sigma gene silencing during melanoma progression and its role in cell cycle control and cellular senescence

Background

The family of 14-3-3 proteins plays an important role in cancer biology by interfering with intracellular signalling pathways and cell cycle checkpoints. The 14-3-3σ isoform acts as a tumor suppressor and is often inactivated during tumor development.

Results

Here, we demonstrate enhanced CpG methylation of the 14-3-3σ gene in lymph node and cutaneous melanoma metastases compared with primary tumors, associated with dramatically reduced mRNA expression. In line with this, treatment of different metastatic melanoma cell lines with 5-aza-2'-deoxycytidine (5-Aza-CdR), a potent inhibitor of cytosine methylation, significantly induces 14-3-3σ protein expression. Additional treatment with histone deacetylase inhibitor 4-phenylbutyric acid (Pba) further enhances 14-3-3σ expression. Induction of 14-3-3σ expression by 5-Aza-CdR/Pba treatment leads to almost complete inhibition of cell proliferation, with cells predominantly arrested in G2-M. The antiproliferative effect of 5-Aza-CdR/Pba was reversed in 14-3-3σ knockdown cells. Similarly, melanoma cell lines stably overexpressing 14-3-3σ show dramatically reduced cell proliferation rates. Moreover, synchronous 14-3-3σ stably overexpressing cells do not progress through cell cycle, but display a permanent increase in the population of 4n DNA containing cells. Interestingly, overexpression of 14-3-3σ induces senescence of melanoma cells and is involved in melanoma cell senescence under genotoxic stress. Finally, 14-3-3σ knockdown supports migratory capacity of melanoma cells in vitro, while 14-3-3σ overexpression has opposing effects.

Conclusion

Taken together, the present report indicates that epigenetic silencing of 14-3-3σ might contribute to tumor progression in malignant melanoma via loss of cell cycle control, impaired cellular senescence program and support of migratory capacity.

In vivo wireless ethanol vapor detection in the Wistar rat

Traditional alcohol studies measure blood alcohol concentration to elucidate the biomedical factors that contribute to alcohol abuse and alcoholism. These measurements require large and expensive equipment, are labor intensive, and are disruptive to the subject. To alleviate these problems, we have developed an implantable, wireless biosensor that is capable of measuring alcohol levels for up to six weeks. Ethanol levels were measured in vivo in the interstitial fluid of a Wistar rat after administering 1 g/kg and 2 g/kg ethanol by intraperitoneal (IP) injection. The data were transmitted wirelessly using a biosensor selective for alcohol detection. A low-power piezoresistive microcantilever sensor array was used with a polymer coating suitable for measuring ethanol concentrations at 100% humidity over several hours. A hydrophobic, vapor permeable nanopore membrane was used to screen liquid and ions while allowing vapor to pass to the sensor from the subcutaneous interstitial fluid.

Effects of exercise on glucose tolerance and insulin resistance. Brief review and some preliminary results

With aging, glucose tolerance (GT) declines, plasma insulin concentration increases, and sensitivity to the action of insulin declines. Evidence is accumulating that this decline in glucose tolerance and insulin sensitivity can be prevented by regularly performed vigorous exercise. Preliminary results are presented in this paper showing that prolonged, strenuous and frequent exercise can also completely normalize GT by decreasing resistance to insulin in some patients with mild non insulin dependent diabetes mellitus (NIDDM) and in some individuals with impaired glucose tolerance (IGT). Exercise appears to be effective in normalizing GT only in patients who still have an adequate capacity to secrete insulin, and in whom insulin resistance is the major cause for abnormal GT. The amount of exercise required to normalize GT in such patients appears to be in the range of 25 to 35 km per week of running, or a comparable amount of another form of exercise, performed on a regular basis.

Proliferation of mitochondria in chronically stimulated rabbit skeletal muscle--transcription of mitochondrial genes and copy number of mitochondrial DNA

Mitochondrial proliferation was studied in chronically stimulated rabbit skeletal muscle over a period of 50 days. After this time, subunits of COX had increased about fourfold. Corresponding mRNAs, encoded on mitochondrial DNA as well as on nuclear genes, were unchanged when related to total tissue RNA, however, they were elevated two- to fivefold when the massive increase of ribosomes per unit mass of muscle was taken into account. The same was true for the mRNA encoding mitochondrial transcription factor A. Surprisingly, tissue levels of mtTFA protein were reduced about twofold, together with mitochondrial DNA. In conclusion, mitochondria are able to maintain high rates of mitochondrial transcription even in the presence of reduced mtTFA protein and mtDNA levels. Therefore, stimulated mtTFA gene expression accompanies stimulated mitochondrial transcription, as in other models, but it is not sufficient for an increase of mtDNA copy number and other, yet unknown, factors have to be postulated.

Germinal center B cell-like (GCB) and activated B cell-like (ABC) type of diffuse large B cell lymphoma (DLBCL): analysis of molecular predictors, signatures, cell cycle state and patient survival

Aiming to find key genes and events, we analyze a large data set on diffuse large B-cell lymphoma (DLBCL) gene-expression (248 patients, 12196 spots). Applying the loess normalization method on these raw data yields improved survival predictions, in particular for the clinical important group of patients with medium survival time. Furthermore, we identify a simplified prognosis predictor, which stratifies different risk groups similarly well as complex signatures. We identify specific, activated B cell-like (ABC) and germinal center B cell-like (GCB) distinguishing genes. These include early (e.g. CDKN3) and late (e.g. CDKN2C) cell cycle genes. Independently from previous classification by marker genes we confirm a clear binary class distinction between the ABC and GCB subgroups. An earlier suggested third entity is not supported. A key regulatory network, distinguishing marked over-expression in ABC from that in GCB, is built by: ASB13, BCL2, BCL6, BCL7A, CCND2, COL3A1, CTGF, FN1, FOXP1, IGHM, IRF4, LMO2, LRMP, MAPK10, MME, MYBL1, NEIL1 and SH3BP5. It predicts and supports the aggressive behaviour of the ABC subgroup. These results help to understand target interactions, improve subgroup diagnosis, risk prognosis as well as therapy in the ABC and GCB DLBCL subgroups.

Imported and indigenous BSE cases in Germany

Bovine spongiform encephalopathy (BSE) is a transmissible fatal neurodegenerative disease in cattle with an average incubation time of five years. The first BSE case in an indigenous cow was detected in Germany in November 2000. This was almost eight years after the huge BSE epidemic in the United Kingdom had peaked, and several years after many EU member states had seen their first BSE case. In the 1990s, BSE had been diagnosed in six imported animals in Germany. However, after the implementation of an active surveillance programme using BSE rapid testing systems, 399 indigenous German BSE cases have been found up to the end of July 2006. The birth cohorts of 1995-1997 contribute to the vast majority of the first 250 German cases that were diagnosed between 2000 and 2003. However, the most recent German BSE cases belong primarily to the birth cohorts 1998-2000 which is indicative of a recycling of BSE infectivity at that time. Moreover, there were two BSE cases in cattle born in spring 2001, i.e. after the meat and bone meal feed ban had come into effect on 2nd December 2000. In this article, we describe the dynamics of the German BSE epidemic and compare these data with those of other countries that observed larger numbers of cases.

Safety and efficacy of first-line irinotecan/fluoropymidine combinations in mCRC patients >65 years compared with those ≤65: The BICC-C study

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Background: BICC-C was a multicenter, randomized study that assessed efficacy & safety of irinotecan/fluoropyrimidines combinations in previously untreated mCRC patients. This study showed that FOLFIRI or FOLFIRI+bev were superior to their comparators (Proc ASCO 2006). We conducted a secondary analysis of efficacy & safety among all patients >65 years compared with those =65. Methods: Pts were randomized to: infusional FOLFIRI, modified bolus IFL (mIFL), or CapeIri; and concurrent celecoxib or placebo in a double-blind fashion. The protocol was amended in April 2004 and bevacizumab (bev) was added to the FOLFIRI and mIFL arms whereas CapeIri was discontinued. Period 1 (P1) and Period 2 (P2) designate subjects enrolled before or after the amendment. Results: Of 430 pts enrolled in P1, 150 were age >65 (median 71; range, 66–87) and 280 were = 65 (median, 56; 20–65). Of 117 pts in P2, 75 were >65 (median, 73; 66–84) and 42 were = 65 (median, 54; 32–65). No significant differences in efficacy or safety were observed between the two age groups. Results for P1: median progression free survival (PFS) was 6.5 and 6.7 mos; and median overall survival (OS) was 18.8 and 19.2 for >65 and =65, respectively. For the FOLFIRI regimen specifically median PFS was 7.5 and 7.6 mos, and median OS was 20.1 and 24.3 mos for >65 and =65, respectively. Results for P2: median PFS was 10.3 and 10.6 mos; and median OS was 19.8 and 23 mos for >65 and =65, respectively. For the FOLFIRI+bev regimen specifically median PFS was 11.1 and 11.2 mos for >65 and =65 respectively, and median OS has not yet been reached for either subgroup at time of analysis. Common grade = 3 AEs are listed below. Conclusions: Efficacy and safety for first line irinotecan/fluoropyrimidine regimens and for FOLFIRI & FOLFIRI+bev, specifically, did not differ for older and younger mCRC patients.

[Table: see text]

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Updated results of BICC-C study comparing first-line irinotecan/fluoropymidine combinations with or without celecoxib in mCRC: Updated efficacy data

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Background: This multicenter, randomized study assessed efficacy & safety for irinotecan/fluoropyrimidines combinations in previously untreated mCRC. Methods: Pts were randomized to: infusional FOLFIRI, modified bolus IFL (mIFL), or CapeIri; and concurrent celecoxib or placebo in a double-blind fashion. The protocol was amended in April 2004: bevacizumab (bev) was added to the FOLFIRI and mIFL arms, whereas CapeIri was discontinued. Period 1 (P1) and Period 2 (P2) designate subjects enrolled before or after the amendment. Initial efficacy & safety analyses were reported at ASCO ’06. We now report follow-up of 46 months for P1 and 31 months for P2. Results: 430 pts were treated in P1 and 117 pts in P2. Baseline characteristics and post-study treatment were balanced. P1 results: Median progression free survival (PFS) was 7.6 mos for FOLFIRI; 5.9 mos for mIFL (p=0.004); and 5.8 mos for CapeIri (p=0.015). Median overall survival (OS) was 23.1 mos for FOLFIRI; 17.6 mos for mIFL (p=0.087); and 18.9 mos for CapeIri (p=0.27). One-year survival rate favored FOLFIRI (75%) compared to either mIFL (65%) or CapeIri (66%). Overall Response Rate (ORR) was 47% in FOLFIRI, 43% in mIFL, 39% in CapeIri (not significantly different). P2 results: Median PFS was 11.2 mos for FOLFIRI+bev and 8.3 mos for mIFL+bev (p=0.28). Median OS was not reached for FOLFIRI+bev but was 19.2 mos for mIFL+bev (p=0.007). One-year survival rate favored FOLFIRI+bev (87%) when compared to mIFL+bev (61%). ORR was 58% for FOLFIRI+bev and 54% for mIFL+bev (p=0.73). Common grade = 3 AEs are listed below. Celecoxib did not impact safety or efficacy. Conclusions: First line FOLFIRI or FOLFIRI+bev were superior to their comparators and show favorable results in survival and tolerability in untreated mCRC. Median survival for FOLFIRI+bev has not been reached.

[Table: see text]

No significant financial relationships to disclose.

Unchanged scrapie pathology in brain tissue of tyrosine kinase Fyn-deficient mice

Fyn is a 59-kDa member of the Src family of tyrosine kinases synthesized on cytosolic polysomes and then targeted to the plasma membrane where it clusters in caveolae-like membrane microdomains. The cellular isoform of the prion protein (PrP) has also been identified to be a caveolar constituent and to participate in signal transduction events concerning cell survival and differentiation via recruitment of Fyn. We studied the scrapie infection of mice deficient for Fyn (Fyn(-/-)) to clarify the role of Fyn in an in vivo model of transmissible spongiforme encephalopathies. Fyn(-/-) mice died on average 9 days earlier than wild-type control mice, but no differences were seen regarding activation of astrocytes, vacuolization of the neuropil, and accumulation of misfolded prion protein. The experimental model suggests that a deficiency for Fyn is detrimental in prion diseases, although it has no major effect on the clinical course of an experimental prion infection of the CNS.