ABSTRACTS OF THE 21st ANNUAL MEETING OF THE ITALIAN ...

Furthermore, compared to either agent alone, FK228/docetaxel
and FK228/cisplatin combinations resulted in increased
caspase cleavage and histone hyperacetylation. In vivo, this
agent caused tumor growth delay without complete regression
in xenograft systems. FK228 sensitized PC3 and 22rv1
xenografts to docetaxel and cisplatin treatments. These
combinations were also tolerable in mice and superior to the
use of either agent alone. Conclusion: As docetaxel and
platinum derivatives are the standard first- and second-line
chemotherapy for hormone-refractory prostate cancer, the
development of chemotherapy-based combination therapies is
of great interest for this disease stage. Our results provide a
rationale for clinical trials on combination treatments with
FK228 in patients with hormone-refractory and chemoresistant
prostate tumors.
21
THE TORC1/TORC2 INHIBITOR, PALOMID 529
(P529), REDUCES TUMOR GROWTH AND
SENSITIZES AGGRESSIVE HORMONE-
REFRACTORY PROSTATE CANCER CELLS
TO CHEMOTHERAPY AND RADIOTHERAPY
BOTH IN VITRO AND IN VIVO
Claudio Festuccia1 , Giovanni Luca Gravina2 , Francesco
Marampon3 , Leda Biordi4 , David Sherris5 and Vincenzo
Tombolini3 1Ricerca Di Base, 2Urologia, 3Radioterapia, and
4Department of Experimental Medicine, Università
dell’Aquila, L’Aquila, Italy;
5Paloma Pharmaceuticals, Inc. , Jamaica Plain, MA, U.S.A.
Background: The AKT-mediated survival-signaling pathway
is an attractive target for cancer therapy. This pathway is
relatively inactive in resting cells and amplification of the AKT
gene occurs in some tumors. The loss of the tumor suppressor
gene PTEN (phosphatase and tensin homolog deleted on
chromosome 10), present in about 30% of prostate primary
tumors and in more than 50% of aggressive castrate-resistant
prostate tumors, constitutively activates AKT, stimulating local
invasion and neo-angiogenesis and reducing sensitivity to
chemotherapeutics and radiotherapy. A novel PI3K/AKT
/mTOR inhibitor, Palomid 529 (P529), shows inhibition of
both AKT and mTOR signaling, as well as inhibiting tumor
cell proliferation. Materials and Methods: We analyzed the in
vitro effects of P529 on a panel of prostatic cancer cell lines
with or without basal activation of AKT, as well as its in vivo
effects on aggressive castrate-resistant PC3 and 22rv1 cell
lines xenografted in nude mice. Results: P529 inhibited cell
proliferation, with IC 50 values ranging between 5 and 30 μM
for 48 hours of treatment. These values seem to be scarcely
related to basal AKT activity, since cells expressing low levels
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ANTICANCER RESEARCH 31: 1807-1956 (2011)
of AKT are also sensitive to P529. However, the re-expression
of PTEN in the PTEN-negative PC3 cell line significantly
reduced the effects of P529, and siRNA for PTEN sensitized
DU145 and 22rv1 PTEN-positive cells to P529. However, we
observed that the effects of P529 treatment were more marked
when this drug was added to culture in clonogenic assays,
suggesting that over longer periods of time, prostate cancer
cells are able to increase AKT activity in an autocrine manner.
For example, secretion of EGFR/Her2 ligands and exogenous
addition of EGF (50 ng/ml) was indeed able to increase P529
efficacy. In this study, we showed that the inhibition of AKT
pathway by P529 (Palomid) enhanced the sensitivity of both
PTEN-positive and -negative prostate cancer cells to docetaxel
and cisplatin in vitro and in vivo. We also demonstrated that
P529 was able to reduce cell proliferation and to induce cell
death, increasing the activity of death receptors TRAILR-5
and FAS and down-modulating the expression of cellular-
FLICE-inhibitory protein (c-FLIP), BCL 2 and survivin.
Conclusion: These combinatorial treatments may open a
promising therapeutic approach for the elimination of
hormone-refractory prostate cancer, which is largely resistant
to conventional therapies.
22
HISTONE DEACETYLASE INHIBITOR,
MS275, INCREASES RADIATION RESPONSES
OF PROSTATE CANCER CELLS
IN VITRO AND IN VIVO
Claudio Festuccia 1 , Giovanni Luca Gravina 2 ,
Francesco Marampon 1 , Mariolina Angelini 3 ,
Vincenzo Tombolini 1 , Corrado Ficorella 4
and Enrico Ricevuto 4
1Radioterapia Oncologica, 2 Urologia, 3 Biologia and
4 Oncologia Medica, Department of Experimental Medicine,
Università dell’Aquila, L’Aquila, Italy
Background: Histone deacetylase (HDAC) inhibitors, which
modulate chromatin structure and gene expression, represent a
class of anticancer agents that hold particular potential as
radiation sensitizers. This study examined the capacity of the
HDAC inhibitor MS275 to modulate radiation response in
human prostate tumor cell lines and explored potential
mechanisms underlying these interactions. Materials and
Methods: We analyzed cell proliferation and apoptosis in the
presence of different doses of MS275 and for different culture
times. In addition, we analyzed the effects of MS275 (0.2 M),
radiation (2-6 Gy), or their combination, in order to define
radiation survival by counting the number of colonies stained
with crystal violet at different incubation intervals of 14±21
days. Results: MS275 induced a dose-dependent inhibition of
proliferation in human prostate cancer cell lines. Exposure to