TY  - JOUR
A1  - von Bueren, André O.
A1  - Oehler, Christoph
A1  - Shalaby, Tarek
A1  - von Hoff, Katja
A1  - Pruschy, Martin
A1  - Seifert, Burkhardt
A1  - Gerber, Nicolas U.
A1  - Warmuth-Metz, Monika
A1  - Stearns, Duncan
A1  - Eberhart, Charles G.
A1  - Kortmann, Rolf D.
A1  - Rutkowski, Stefan
A1  - Grotzer, Michael A.
T1  - c-MYC expression sensitizes medulloblastoma cells to radio- and chemotherapy and has no impact on response in medulloblastoma patients
JF  - BMC Cancer
N2  - Background: 

To study whether and how c-MYC expression determines response to radio-and chemotherapy in childhood medulloblastoma (MB). 

Methods: 

We used DAOY and UW228 human MB cells engineered to stably express different levels of c-MYC, and tested whether c-MYC expression has an effect on radio-and chemosensitivity using the colorimetric 3-(4,5-dimethylthiazol- 2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay, clonogenic survival, apoptosis assays, cell cycle analysis, and western blot assessment. In an effort to validate our results, we analyzed c-MYC mRNA expression in formalin-fixed paraffin-embedded tumor samples from well-documented patients with postoperative residual tumor and compared c-MYC mRNA expression with response to radio-and chemotherapy as examined by neuroradiological imaging. 

Results: 

In DAOY -and to a lesser extent in UW228 -cells expressing high levels of c-MYC, the cytotoxicity of cisplatin, and etoposide was significantly higher when compared with DAOY/UW228 cells expressing low levels of c-MYC. Irradiation-and chemotherapy-induced apoptotic cell death was enhanced in DAOY cells expressing high levels of c-MYC. The response of 62 of 66 residual tumors was evaluable and response to postoperative radio-(14 responders (CR, PR) vs. 5 non-responders (SD, PD)) or chemotherapy (23 CR/PR vs. 20 SD/PD) was assessed. c-MYC mRNA expression was similar in primary MB samples of responders and non-responders (Mann-Whitney U test, p = 0.50, ratio 0.49, 95% CI 0.008-30.0 and p = 0.67, ratio 1.8, 95% CI 0.14-23.5, respectively). 

Conclusions: 

c-MYC sensitizes MB cells to some anti-cancer treatments in vitro. As we failed to show evidence for such an effect on postoperative residual tumors when analyzed by imaging, additional investigations in xenografts and larger MB cohorts may help to define the exact function of c-MYC in modulating response to treatment.
KW  - Induced apoptosis
KW  - Down-regulation
KW  - Childhood medulloblastoma
KW  - Melanoma-cells
KW  - Cisplatin
KW  - Lines
KW  - Gene
KW  - Radiotherapy
KW  - Fibroblasts
KW  - Activation
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134185
VL  - 11
IS  - 74
ER  - 
TY  - JOUR
A1  - Bergmiller, Tobias
A1  - Pena-Miller, Rafael
A1  - Boehm, Alexander
A1  - Ackermann, Martin
T1  - Single-cell time-lapse analysis of depletion of the universally conserved essential protein YgjD
JF  - BMC Microbiology
N2  - Background: 

The essential Escherichia coli gene ygjD belongs to a universally conserved group of genes whose function has been the focus of a number of recent studies. Here, we put ygjD under control of an inducible promoter, and used time-lapse microscopy and single cell analysis to investigate the phenotypic consequences of the depletion of YgjD protein from growing cells. 

Results: 

We show that loss of YgjD leads to a marked decrease in cell size and termination of cell division. The transition towards smaller size occurs in a controlled manner: cell elongation and cell division remain coupled, but cell size at division decreases. We also find evidence that depletion of YgjD leads to the synthesis of the intracellular signaling molecule (p) ppGpp, inducing a cellular reaction resembling the stringent response. Concomitant deletion of the relA and spoT genes - leading to a strain that is uncapable of synthesizing (p) ppGpp abrogates the decrease in cell size, but does not prevent termination of cell division upon YgjD depletion. 

Conclusions: 

Depletion of YgjD protein from growing cells leads to a decrease in cell size that is contingent on (p) ppGpp, and to a termination of cell division. The combination of single-cell time-lapse microscopy and statistical analysis can give detailed insights into the phenotypic consequences of the loss of essential genes, and can thus serve as a new tool to study the function of essential genes.
KW  - Transfer-RNA modification
KW  - Escherichia-coli K-12
KW  - Gene
KW  - Division
KW  - Expression
KW  - Inactivation
KW  - Maintenance
KW  - Growth
KW  - Level
KW  - Ftsz
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-142324
VL  - 11
IS  - 118
ER  -