AML:
In the era of personalized medicine, we are developing targeted
drug combinations for acute myeloid leukemia patients harboring mutations in
the H3K4 methyltransferase, MLL (myeloid/lymphoid or mixed lineage leukemia)
and the receptor tyrosine kinase FLT3 (FMS-like tyrosine kinase 3). Preclinical studies utilize a mouse model of acute
myeloid leukemia that harbors these two genetic mutations. We
are targeting the downstream effects of both mutations by testing the
efficacy of epigenetic modifiers as well as tyrosine kinase inhibitors in drug
trials. We hope to find a combinatorial
effect that gives MLL-PTD; FLT3-ITD pts a potentially better therapeutic
outcome. Future experiments will address epigenetic changes that
occur in response to the drugs with the goal of finding yet
more therapeutic targets to help these patients survive
longer and eventually be cured of cancer.
Additional areas of research in AML include study of the role of the Axl/Gas6 pathway in the pathogenesis
of acute myeloid leukemia (AML). The
Axl/Gas6 pathway is a receptor tyrosine kinase (RTK) known to be involved in a
variety of biological functions. As it
was previously published, the Axl/Gas6 pathway is crucial for signaling of
another RTK c-Kit, which is highly homologous to RTK FLT3. As FLT3 is the most well-known prognostic marker
for AML, my work has been to test the hypothesis that the Axl/Gas6 pathway may
contribute to AML through regulating FLT3 and its biological functions. Current data has demonstrated that the
Axl/Gas6 pathway promotes the growth and survival of leukemic cells and blocks
myeloid differentiation. Furthermore,
the Axl/Gas6 pathway is crucial for FLT3 signaling. Ongoing and future study is to test whether
inhibiting the Axl/Gas6 pathway can suppress the occurrence of AML in vivo in mouse leukemia model.
NK Cell Biology:
Research efforts are
directed to define the molecular mechanisms regulating the immunoregulatory and
cytotoxicity functions of Natural Killer cells and their subsets. To achieve this goal we are currently dissecting
the activatory and inhibitory pathways that regulate Natural killer (NK) cell
activity. In particular, we’ve
discovered that the inositol-phosphatase SHIP-1 and the PP2A inhibitor SET are,
respectively, a negative and a positive regulator of Interferon gamma
production which is induced in NK cells by different monokines. We also have
evidences that SET regulates NK cell cytotoxicity by effecting expression of
granules components like the Granzyme B. In addition, we also investigated the
role of anti-inflammatory cytokines TGF-β in regulating Fc Receptor Functions.
We reported that the anti-inflammatory cytokine TGF-β utilizes SMAD3 to inhibit
CD16-mediated IFN-γ production, antibody dependent cytotoxicity, Granzyme B and
Perforin expression in NK cells. Based on these findings we are also
investigating the role of microRNAs (miRs) in the regulation of NK cell
activation and/or development. The final
goal of my studies is the identification of activatory and inhibitory molecules
which can be used to enhance NK cell anti-tumor activity.
EBV associated disease:
EBV associated post-transplant
lymphoproliferative disorder (PTLD) is a common and often fatal malignancy in
organ transplant patients. The incidence of PTLD has been shown to be
directly related to a low frequency of EBV-specific cytotoxic T lymphocytes
(CTLs) in patients receiving immunosuppressive therapy to prevent organ
rejection. Using a chimeric mouse-human model of human PTLD and
subsequently in PTLD patients, we have identified that the expression an EBV
lytic gene, BZLF1, plays an important role in controlling the development of
PTLD. We hypothesize that at least one component of the increased
incidence of PTLD in this patient population is a cellular immune deficiency
against EBV lytic and latent antigens. A corollary to this hypothesis is
that vaccine-enhanced, EBV-specific immunity will restore the protection from
this malignancy. We recently reported a
novel strategy for vaccination against the EBV-associated PTLD using a chimeric
rAdF35/BZLF1 viral vector or a highly purified EBV BZLF1 protein.
Approximately 75% of normal human donor cells show a moderate to strong immune
responses to rAdF35/BZLF1 viral vector stimulation assayed by an IFN-
ELISpot. Moreover, rAdF35BZLF1 viral vector transduced dendritic cell
vaccination greatly improve survival rate in a Hu-PBL-SCID animal model. We
have cloned the lytic EBV BZLF1 protein into a prokaryotic vector expression
cassette name pET26b+ system, expressed in E. Coli BL26 cells. From this
system, large quantities of highly purified and endotoxin-free BZLF1 protein
(>95% by SDS-PAGE) have been obtained by ion exchange and subsequent size
column chromatography. We’ve shown that
the highly purified BZLF1-loaded human antigen presenting cells (APCs) can
promote the expansion of the EBV BZLF1 specific memory CD8+ CTLs in vitro. We are currently
evaluating the efficacy of highly purified BZLF1 protein-mediated vaccination
in a chimeric mouse-human model of human PTLD.