2009-12-06
The goal of the Minority Medical Student Award Program
(MMSAP) is to increase the number of medical students in hematology from
under-represented minority groups by introducing them to hematology in their
early years of medical school. ASH News Daily is pleased to share a summary of
the research conducted by current MMSAP participant Steven Ovu. His research
mentor was Dr. Felipe Samaniego, M.
D. Anderson
Cancer Center.
Raised in Lagos, Nigeria until high school, Steven Ovu moved to
the United States
to continue his education. He received his undergraduate degree from Prairie
View A&M University (PVAMU), in Prairie View, TX, where he was involved in
a number of research experiences. Prior
to the MMSAP, Steven also participated in two summer programs at NHLBI, and he
shadowed a pediatric hematologist-oncologist at the Texas Children’s Hospital.
Background
Nucleolin is a major nucleolar protein of exponentially
growing eukaryotic cells directly involved in the regulation of ribosome
biogenesis and maturation. This highly conserved protein contains three major
RNA binding domains through which it controls the organization of nucleolar
chromatin, packaging of pre-RNA, rDNA transcription, and ribosome assembly.
This is significant because the nucleoli of rapidly dividing cells are
functionally hyperactive compared to non-dividing cells, and increases in
nucleolar activities, such as ribosome biogenesis, are prerequisites for cell
proliferation. Additionally, during proliferation nucleolin is trafficked out
of the nucleus and performs multiple survival functions in the cytoplasm and on
the plasma membrane. We have found it to be a protein of interest in lymphoma
development via Fas-mediated apoptosis regulation.
Method
The following techniques were used: 1) immunoprecipitation
and immunoblot studies in cultured solid tumors and lymphomas to measure their
expression levels of nucleolin in comparison to peripheral blood mononuclear
cells (PBMC) control; 2) in vivo
treatment and immunohistochemistry (IHC) analysis to measure the outcome of
overexpression of nucleolin in mice livers as a protective role
(anti-apoptotic) versus normal expression levels; and 3) propidium iodide (PI)
staining in flow cytometry for dead cell quantification in HEK-293 cells and
the PBMC control.
Conclusion
Results from #1
confirmed a significantly higher expression level of nucleolin in 99 percent of
the various cancer cell lines than normal PBMCs in an approximate 2:1 ratio.
Outcome from #2 indicated the protective abilities of nucleolin overexpression
against Fas-mediated liver hemorrhaging induced by jo2 challenge versus
increased destruction of liver and lower survival score in vector control
infected mice. IHC results depicted shrinkage of nuclei from increased
apoptosis in vector mice versus nucleolin overexpressing livers. TUNEL staining
for apoptotic cells also correlated with greater apoptosis in vector-control
groups than in nucleolin-infected mice. Flow data from #3 obtained from
transfected HEK-293 cell lines did not
show statistically significant protective effect against apoptosis versus PBMC
controls.
Future studies will
involve nucleolin knockdown to further investigate in vivo activities,
PI studies in solid tumor/lymphoma cells, functional
studies to test for active caspase 8 cleavage in mice, and designing and
testing peptides that will interfere with nucleolin-Fas binding.
The MMSAP is sponsored in part by Amgen, Inc.,
and Genentech BioOncology.
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