مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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THE
ROLES OF SPHINGOSINE KINASES 1 AND 2 IN REGULATING THE WARBURG EFFECT IN
PROSTATE CANCER CELLS
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رابط البحث:
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Link
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تاريخ النشر:
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June
2013
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موجز عن البحث:
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We
have previously shown that treatment of androgen-sensitive LNCaP cells with
the sphingosine kinase (SK) inhibitor SKi
(2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole) induces the proteasomal
degradation of two N-terminal variants of SK1 (SK1a and SK1b), increases
C22:0-ceramide and diadenosine 5′,5′′′-P1,P3-triphosphate (Ap3A) and reduces
S1P levels, and promotes apoptosis. We have now investigated the effects of
three SK inhibitors (SKi, (S)-FTY720 vinylphosphonate, and (R)-FTY720 methyl
ether) on metabolite and sphingolipid levels in androgen-sensitive LNCaP and
androgen-independent LNCaP-AI prostate cancer cells. The 51 kDa N-terminal
variant of SK1 (SK1b) evades the proteasome in LNCaP-AI cells, and these
cells do not exhibit an increase in C22:0-ceramide or Ap3A levels and do not
undergo apoptosis in response to SKi. In contrast, the SK inhibitor
(S)-FTY720 vinylphosphonate induces degradation of SK1b in LNCaP-AI, but not
in LNCaP cells. In LNCaP-AI cells, (S)-FTY720 vinylphosphonate induces a
small increase in C16:0-ceramide levels and cleavage of polyADPribose
polymerase (indicative of apoptosis). Surprisingly, the level of S1P is
increased by 7.8- and 12.8-fold in LNCaP and LNCaP-AI cells, respectively, on
treatment with (S)-FTY720 vinylphosphonate. Finally, treatment of
androgen-sensitive LNCaP cells with the SK2-selective inhibitor (R)-FTY720
methyl ether increases lysophosphatidylinositol levels, suggesting that SK2
may regulate lyso-PI metabolism in prostate cancer cells.
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البحث (2):
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عنوان البحث:
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The
roles of Sphingosine Kinases 1 and 2 in regulating the Warburg effect in
prostate cancer cells
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رابط البحث:
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Link
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تاريخ النشر:
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April
2013
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موجز عن البحث:
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Two
isoforms of sphingosine kinase, SK1 and SK2, catalyze the formation of the
bioactive lipid sphingosine 1-phosphate (S1P) in mammalian cells. We have
previously shown that treatment of androgen-sensitive LNCaP prostate cancer
cells with a non-selective SK isoform inhibitor,
2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole (SKi), induces the
proteasomal degradation of SK1. This is concomitant with a significant
increase in C22:0-ceramide and sphingosine levels and a reduction in S1P
levels, resulting in the apoptosis of LNCaP cells. In contrast, we show here
that a SK2-selective inhibitor, (R)-FTY720 methyl ether (ROME), increases
sphingosine and decreases S1P levels but has no effect on ceramide levels and
does not induce apoptosis in LNCaP cells. We also show that several
glycolytic metabolites and (R)-S-lactoylglutathione are increased upon
treatment of LNCaP cells with SKi, which induces the proteasomal degradation
of c-Myc. These changes reflect an indirect antagonism of the Warburg effect.
LNCaP cells also respond to SKi by diverting glucose 6-phosphate into the
pentose phosphate pathway to provide NADPH, which serves as an antioxidant to
counter an oxidative stress response. SKi also promotes the formation of a
novel pro-apoptotic molecule called diadenosine
5′,5”’-P(1),P(3)-triphosphate (Ap3A), which binds to the tumor suppressor
fragile histidine triad protein (FHIT). In contrast, the SK2-selective
inhibitor, ROME, induces a reduction in some glycolytic metabolites and does
not affect oxidative stress. We conclude that SK1 functions to increase the
stability of c-Myc and suppresses Ap3A formation, which might maintain the
Warburg effect and cell survival, while SK2 exhibits a non-overlapping
function.
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البحث (3):
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عنوان البحث:
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The
sphingosine kinase inhibitor 2-(p-hyroxyanilino)-4-(p-chlorophenyl)thiazole
reduces androgen receptor expression via an oxidative stress-dependent
mechanism
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رابط ابحث:
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Link
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تاريخ النشر:
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February
2013
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موجز عن البحث:
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Background and Purpose
Sphingosine kinase catalyses the
formation of sphingosine 1-phosphate and is linked with androgen receptor
signalling in prostate cancer cells. Therefore, we investigated the effect of
sphingosine kinase inhibitors on androgen receptor expression.
Experimental Approach
Androgen-sensitive LNCaP cells
were treated with SKi (2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole), which inhibits sphingosine
kinases 1 and 2 activity, and the effect on androgen receptor expression was
measured.
Key Results
Treatment of cells with SK1
inhibitors reduced the expression of the androgen receptor and
prostate-specific antigen, while (R)-FTY720 methyl
ether (a sphingosine-kinase-2-selective inhibitor), at a concentration that
eliminates sphingosine kinase 2 from cells, had no significant effect on
androgen receptor expression. The effect of SKi on androgen receptor
expression was independent of the SKi-induced proteasomal degradation of SK1
and was post translational, although androgen receptor mRNA transcript was
reduced. Fumonisin B1 (a ceramide synthase inhibitor) also failed to reverse
the effect of SKi on androgen receptor expression, thereby excluding a role
for ceramide derived from the salvage pathway. The effect of SKi on androgen
receptor expression was reversed by N-acetylcysteine, which was used to
scavenge reactive oxygen species.
Conclusion and Implications
Inhibition of sphingosine kinase
1 activity abrogates androgen receptor signalling via an oxidative
stress-induced, p53-independent mechanism in prostate cancer cells.
Therefore, SK1 inhibitors may offer therapeutic potential in promoting the
removal of AR receptors from prostate cancer cells, resulting in an increased
efficacy, which is likely to be superior to inhibitors that simply reversibly
inhibit AR signalling.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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Metabolomics
2013 9th Annual International Conference of
the Metabolomics Society
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تاريخ الإنعقاد:
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1-4/07/2013
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بلد
ومكان الإنعقاد:
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Glasgow,
Scotland, UK
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طبيعة المشاركة:
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عرض
نتائج بحث
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عنوان المشاركة
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OPTIMIZATION
AND VALIDATION OF A METABOLOMIC METHOD FOR ANALYSIS OF PROSTATE CANCER CELL CULTURES
(LNCaP) USING EXACTIVE-ORBITRAP MASS SPECTROMETER
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موجز عن المشاركة
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A
method for carrying out metabolomics profiling of tissue cultures with an
optimized extraction procedure and validation of an analytical method using
LC/MS. Cell culturing, quenching, metabolite extraction, and the LC/MS
settings were optimized aiming at a reliable,
unbiased, sensitive, and high throughput metabolomics protocol.
This approach was validated using ~ 200 standard compounds and LNCaP. An
MS/MS library was obtained for both. Effects of storage conditions on
metabolite profiles and stability study were
assessed.
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