Page 252 - 2014 Printable Abstract Book
P. 252
shown therapeutic effects in NE tumors and might be one option to enhance the effect from 177Lu-
octreotate therapy. The aim of this study was to determine the therapeutic effect on GOT1 tumors when
combining 177Lu-octreotate and the hedgehog signaling pathway inhibitor LDE225.
Methods: GOT1 bearing BALB/c nude mice were divided into 3 groups (5 mice/group). The groups were
treated with either LDE225 (80 mg/kg twice a week via oral gavage), or 30 MBq 177Lu-octreotate i.v., or
a combination of both. Tumor size was measured twice a week using calipers. Animals were killed 41 days
after injection and tumors were excised. Samples from each tumor were snap frozen and total RNA was
extracted and examined by microarray analysis. Gene expression patterns and associated biological
functions were compared to that of untreated controls using Nexus Expression, IPA and Gene Ontology
terms. Results: The mean tumor volume was clearly reduced after 177Lu-octreotate and combination
treatment, while LDE225 treatment alone resulted in a stable mean tumor volume with time. This
difference was statistically significant up to more than 20 days after injection, when the tumors in the
177Lu-octreotate and combination treatment groups began to re-grow. The re-growth-rate seemed to be
faster in the 177Lu-octreotate treatment group. The microarray analysis showed that the combination
treatment had a more profound impact on transcription regulation than the other treatment groups.
Conclusions: Combination therapy using 177Lu-octreotate and LDE225 could be beneficial to patients with
NE-tumors. Significant differences in transcript regulation suggest substantial effects on tumor function
at late time points following combination therapy. Further studies should be performed to determine
optimal treatment protocol.
(PS4-29) Evaluating the effect of metronomic dosing and the radiosensitizing potential of
1
1
nanoliposomal topotecan on the tumor and its microenvironment. Amar Jyoti, PhD ; Pallavi Sethi, PhD ;
2
1
2
2
Kyle Fugit, PhD ; Ulrich Langner, PhD, DABR ; William St. Clair, MD, PhD ; Ronald C. McGarry, MD, PhD ;
1
1
Bradley D. Anderson, PhD ; and Meenakshi Upreti, PhD, Department of Pharmaceutical Sciences,
1
University of Kentucky, Lexington, KY and Department of Radiation Medicine, University of Kentucky,
2
Lexington, KY
Topotecan (TPT) a DNA Topoisomerase I inhibitor and radiosensitizer is currently being used in
the treatment of various localized cancers from different tissue origin including the breast. Despite its
known anticancer and antiangiogenic properties the clinical use of TPT is limited owing to its rapid
clearance and hematological toxicity. Nanoliposomal TPT (NTPT) can potentially increase its efficacy by
shielding it from systemic clearance, allowing greater uptake in solid tumors. However, our studies
utilizing an in-vitro 3D co-culture tumor model incorporating the stromal elements indicate that the
extended or controlled release of TPT by the nanoparticle in the tumor microenvironment is responsible
for increased cytotoxicity in the tumor. TPT is actively loaded in the nanoliposomes via a pH gradient in
the unilamellar (100 nm) DSPC and DSPE-PEG2K liposomes. A spectroscopic method has been developed
to non-invasively monitor release of entrapped TPT in situ. Effective dose of radiation and TPT were
determined by cell viability and clonogenic assays. MTT assays show that endothelial cells are more
sensitive to TPT treatment than tumor cells. Interestingly, half or one fourth of TPT IC50 dose prior to
radiation exposure (3Gy) was effective in decreasing the surviving fraction of both tumor and endothelial
cells confirming the radiosensitizing potential of TPT. We have developed a 3D in-vitro murine tumor
model of triple negative breast cancer where GFP labeled tumor cells are co-cultured with endothelial
cells. Combinatorial treatment with NTPT and radiation of tumor-endothelial spheroid (TES) reveals a
decrease in spheroid size and severe disruption of the peripheral layers with time. NTPTs based low dose
250 | P a g e
octreotate therapy. The aim of this study was to determine the therapeutic effect on GOT1 tumors when
combining 177Lu-octreotate and the hedgehog signaling pathway inhibitor LDE225.
Methods: GOT1 bearing BALB/c nude mice were divided into 3 groups (5 mice/group). The groups were
treated with either LDE225 (80 mg/kg twice a week via oral gavage), or 30 MBq 177Lu-octreotate i.v., or
a combination of both. Tumor size was measured twice a week using calipers. Animals were killed 41 days
after injection and tumors were excised. Samples from each tumor were snap frozen and total RNA was
extracted and examined by microarray analysis. Gene expression patterns and associated biological
functions were compared to that of untreated controls using Nexus Expression, IPA and Gene Ontology
terms. Results: The mean tumor volume was clearly reduced after 177Lu-octreotate and combination
treatment, while LDE225 treatment alone resulted in a stable mean tumor volume with time. This
difference was statistically significant up to more than 20 days after injection, when the tumors in the
177Lu-octreotate and combination treatment groups began to re-grow. The re-growth-rate seemed to be
faster in the 177Lu-octreotate treatment group. The microarray analysis showed that the combination
treatment had a more profound impact on transcription regulation than the other treatment groups.
Conclusions: Combination therapy using 177Lu-octreotate and LDE225 could be beneficial to patients with
NE-tumors. Significant differences in transcript regulation suggest substantial effects on tumor function
at late time points following combination therapy. Further studies should be performed to determine
optimal treatment protocol.
(PS4-29) Evaluating the effect of metronomic dosing and the radiosensitizing potential of
1
1
nanoliposomal topotecan on the tumor and its microenvironment. Amar Jyoti, PhD ; Pallavi Sethi, PhD ;
2
1
2
2
Kyle Fugit, PhD ; Ulrich Langner, PhD, DABR ; William St. Clair, MD, PhD ; Ronald C. McGarry, MD, PhD ;
1
1
Bradley D. Anderson, PhD ; and Meenakshi Upreti, PhD, Department of Pharmaceutical Sciences,
1
University of Kentucky, Lexington, KY and Department of Radiation Medicine, University of Kentucky,
2
Lexington, KY
Topotecan (TPT) a DNA Topoisomerase I inhibitor and radiosensitizer is currently being used in
the treatment of various localized cancers from different tissue origin including the breast. Despite its
known anticancer and antiangiogenic properties the clinical use of TPT is limited owing to its rapid
clearance and hematological toxicity. Nanoliposomal TPT (NTPT) can potentially increase its efficacy by
shielding it from systemic clearance, allowing greater uptake in solid tumors. However, our studies
utilizing an in-vitro 3D co-culture tumor model incorporating the stromal elements indicate that the
extended or controlled release of TPT by the nanoparticle in the tumor microenvironment is responsible
for increased cytotoxicity in the tumor. TPT is actively loaded in the nanoliposomes via a pH gradient in
the unilamellar (100 nm) DSPC and DSPE-PEG2K liposomes. A spectroscopic method has been developed
to non-invasively monitor release of entrapped TPT in situ. Effective dose of radiation and TPT were
determined by cell viability and clonogenic assays. MTT assays show that endothelial cells are more
sensitive to TPT treatment than tumor cells. Interestingly, half or one fourth of TPT IC50 dose prior to
radiation exposure (3Gy) was effective in decreasing the surviving fraction of both tumor and endothelial
cells confirming the radiosensitizing potential of TPT. We have developed a 3D in-vitro murine tumor
model of triple negative breast cancer where GFP labeled tumor cells are co-cultured with endothelial
cells. Combinatorial treatment with NTPT and radiation of tumor-endothelial spheroid (TES) reveals a
decrease in spheroid size and severe disruption of the peripheral layers with time. NTPTs based low dose
250 | P a g e
