David A. Frank, M.D., Ph.D.
&=
nbsp; Summary
of proposal. The focus of=
this
proposal is to utilize our increased understanding of the molecular
abnormalities that underlie CLL to develop rational molecular therapeutic
approaches for the treatment of this disease. In previous research, we had deter=
mined
that abnormalities in the phosphorylation of the transcription factor STAT1=
on
a unique serine residue was a ubiquitous feature of CLL. Furthermore, biological therapies =
used
to treat CLL result in the activation of STAT1, and clinical response
correlates with the activation of this protein. Based on these findings, and
confirmatory in vitro work, we initiated experiments to identify potential
drugs that could activate STAT1 and enhance its function. Through this approach, we identifi=
ed a compound (referred to as “2-NP”), that =
can
enhance STAT1 function in CLL cells.
We thus proposed to determine the effects of 2-NP on the biology of =
CLL
cells, alone and in combination with other therapies for CLL, in cell cultu=
re
systems and animal models.
&=
nbsp; Research
progress. Using samples f=
rom
untreated patients with CLL cultured in vitro, we have shown that 2-NP
increases STAT1 target gene expression alone, and enhances the activation of
these genes when used in conjunction with the biological agent bryostatin
1. Furthermore, 2-NP increase=
s the
degree of differentiation of CLL cells when used in conjunction with bryost=
atin
1, as assessed by CD22 expression.
When CLL cells are treated with the combination of 2-NP and fludarab=
ine
or the monoclonal antibody rituximab, enhanced cell killing can be seen when
assessed at 72 hours. Notably,
peripheral blood mononuclear cells from normal donors are unaffected by
addition of 2-NP to any of these therapies, reflecting the fact that abnorm=
al
STAT1 phosphorylation is restricted to CLL cells. These results strongly support the
hypothesis that pharmacological activation of STAT1 may be an extremely
effective therapy for CLL.
&=
nbsp; The
second aim of the proposal focused on the use of 2-NP in a transgenic mouse
model of CLL. In collaboratio=
n with
several of our colleagues at Dana-Farber, we have been developing a system =
to
propagate human CLL cells in immunodeficient mice. As this system seems more benefici=
al for
modeling human CLL, we have deferred initiation of this aim pending validat=
ion
of this model. However, we are
fully committed to proceeding with the pre-clinical studies necessary to
introduce STAT1-directed molecular therapy into clinical trials for patients
with CLL.
&=
nbsp; Future
directions. We are taking=
a
three-pronged approach to following up on this research. First, as noted, we are planning on
initiating studies of 2-NP in an animal model of CLL, to determine the
potential of this approach for treating CLL patients. Second, to accelerate the introduc=
tion
of STAT1-directed therapy of CLL, we are identifying drugs that are already
known to be safe in humans that enhance STAT1 function, and which can be
introduced into clinical trials in patients with CLL in the near term. An integral part of such a study w=
ould
be recovery of CLL cells from treated patients to assess and optimize the
activation of STAT1 for therapeutic purposes. This pharmacodynamic component of =
these
studies would be essential to optimizing this strategy for clinical use.
&=
nbsp; We
are extremely grateful for the generous support of the CLL Foundation. As noted above, it has been instru=
mental
in moving forward our translational research whose goal is to introduce new
molecular therapies for CLL that will be more effective and less toxic. We believe several publications and
presentations will emanate from this work, and we will, of course, acknowle=
dge
support from the CLL Foundation in those.&=
nbsp;
I would also welcome the opportunity to assist the CLL Foundation in=
any
of its activities that will enhance the therapy of this common though incur=
able
disease.