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Name of Student:
Soojin Kim
Research Supervisor: Dr. Amina Zoubeidi
Title of Presentation: Elucidation of AR impact on the Paternally expressed gene 10 (PEG10) in
Enzalutamide-resistant prostate cancer
Abstract
Background: Despite advances in therapeutics, castration resistant prostate cancer (CRPC)
continues to be a major problem. Resistance to second generation androgen receptor (AR)
inhibitors such as Enzalutamide inevitably occurs, and CRPC patients can progress to
neuroendocrine prostate cancer (NEPC) which is highly metastatic and lethal. The
mechanisms of progression are yet to be elucidated, and currently there is no effective
treatment. Paternally expressed gene 10 (PEG10) is a retrotransposon-derived gene which has
been reported to be elevated in response to androgen deprivation, and also significantly upregulated in NEPC. We have developed a unique model of Enzalutamide-resistant CRPC cell
lines, 42D, which express genes involved in neuroendocrine transdifferentiation. Apart from
these markers, high levels of PEG10 expression have also been observed. PEG10 contributes
to pro-survival and anti-apoptotic ability in NEPC. Understanding the mechanisms by which
PEG10 is regulated and whether it plays role in driving the Enzalutamide-resistant CRPC to
NEPC would provide an important insight into the development of effective therapeutic
regime.
Hypothesis: We hypothesize that AR negatively regulates PEG10 to drive NEPC progression
by transcriptional suppression, and that PEG10 drives NEPC through regulation on the
neuroendocrine genes.
Method: AR and PEG10 activity were manipulated in LNCaP cells and Enzalutamideresistant 42D cells using small molecule inhibitors, synthetic androgens, and differential
media. The expression of PEG10 and NE markers such as NCam1 and Chromogranin A were
observed through qRT-PCR and western blot. Luciferase activity was measured using the
PEG10 plasmid transfection. siRNA for PEG10 were transfected and NE markers were
monitored using western blot, qRT-PCR.
Result: Upon suppression of AR activity using Enzalutamide and charcoal stripped serum
(CSS) on LNCaP and 42D, we observed that PEG10 expression increases followed by an
increase in the NE differentiation markers. Inversely, stimulating the AR activity using
synthetic androgen (R1881), we found a decrease of PEG10 and NE markers’ expression in a
time and dose-dependent manner. These observations indicate that AR activity negatively
regulates PEG10 expression. PEG10 emergence occurs before than of NE markers, which
suggest that it may be a driver of NEPC progression. Targeting PEG10 knockout using siRNA,
we have observed so far a reduction in the expression of NE markers involved in the
transdifferentiation.
Conclusion: Our data suggest that PEG10 could be a potential target in NEPC; further
elucidating the PEG10 target pathway will provide strong support for the development of
therapeutic target against NEPC and ultimately lead to improved survival outcomes of the
patients.