Annual Meeting Proceedings Part 1 - American Society of Clinical ...

38s Breast Cancer—HER2/ER
626 General Poster Session (Board #12E), Sat, 8:00 AM-12:00 PM
Efficacy of INK128, an mTORC1/mTORC2 kinase inhibitor, in breast
cancer models driven by HER2-PI3K-AKT-mTOR pathway. Presenting
Author: Pradip De, Department of Medicine, Emory University, Atlanta, GA
Background: Downstream of the PI3K-AKT pathway, the mTOR has been
shown to be essential effector in promoting cell proliferation, survival,
mRNA translation and tumor susceptibility. Aberrant activation of the
PI3K-AKT-mTOR pathway occurs frequently in breast tumor (BT) and
contributes to resistance to trastuzumab (T). Using a HER2 amplified BT
model; we investigated the antitumor efficacy of the dual mTORC1/
mTORC2 kinase inhibitor INK128 alone and in combination with T.
Methods: The antiproliferative and HER2-mediated cellular signaling (pAKT,
pP70S6K, pS6RP, p4EBP1 and p-ERK) effects of INK128 alone and in
combination with T were evaluated in HER2 amplified T-sensitive (BT474),
T-resistant (BT474HR), and HER2 amplified/PIK3CA mutated (HCC1954,
UACC893) BT cell lines by MTT assay and Western blots. Athymic mice
bearing BT474 and BT474HR xenograft tumors were treated with INK128
and T (alone and in combination). Results: (1)INK128 exhibited excellent
in vitro cell killing activity in MTT assay with IC50’s below 50nM. INK128
was more potent when combined with T, (2) INK128 blocked mTORC1,
mTORC2 and thus did not cause the mTORC2 activation of AKT observed
with rapalogues, (3) inhibition of phosphorylation of AKT(S473), P70S6K,
S6RP, and 4EBP1(T37/46, T70) was observed following INK128 treatment,
and the combination of INK128 and T more effectively blocked the
PI3K-AKT-mTOR pathway, (4) INK128 dose-dependently blocked 3D-ON-
TOP clonogenic growth of HER2� cells. This effect was potentiated in the
presence of T and (5) xenograft data show that the combination of INK128
and T has strongly enhanced anti-tumor effect in both sensitive and
resistant models, something that cannot be achieved by either monotherapy.
Conclusions: Our data suggest that 1) therapeutic targeting of the
PI3K-AKT-mTOR signaling should be effective in abrogating resistance to T
therapy in HER2� BT, 2) INK128 mitigates the feedback activation of AKT
caused by selective inhibition of mTORC1 and 3) targeting both the HER2
and the mTORC1/2 signaling pathways is an attractive strategy to enhance
the clinical activity of T therapy, as well as to prevent or delay the
development of resistance.
629 General Poster Session (Board #12H), Sat, 8:00 AM-12:00 PM
Impact of PIK3CA mutations and p95HER2 expression on the outcome of
HER2-positive metastatic breast cancer patients treated with a trastuzumabbased
therapy. Presenting Author: Andrea Fontana, Division of Medical
Oncology 2, Azienda Ospedaliero-Universitaria Pisana, Istituto Toscano
Tumori, Pisa, Italy
Background: Currently, no biomarkers of trastuzumab (T) clinical resistance
have been validated. The aim of this pilot study was to evaluate the impact
of PIK3CA mutations and p95HER2 (pHER2 truncated form) expression
on the efficacy of a T based-therapy in a HER2-positive metastatic breast
cancer (MBC) patients (pts). Methods: 107 HER2-positive MBC pts, treated
in the last 10 years, were evaluated. Median age was 54 years (25-79);
ECOG performance status was 0 in 56% of pts; all pts received several lines
of treatment including T; biomarkers molecular analysis was performed in
70 tumor specimens. The IHC expression of p95HER2 was evaluated by a
monoclonal antibody that specifically recognizes only the HER2 external
domain; the HER2 integrity was defined by the presence of a homogeneous
membrane staining (moderate or intense) in at least 30% of the cells,
otherwise the HER2 was defined as p95HER2 positive. PIK3CA mutations
in exons 9 and 20 were detected by automated sequencing. The molecular
data were correlated to Time to progression (TTP) of the first line treatment
including T and the Overall Survival (OS) by using the Kaplan-Meir method
and the log-rank-test. Results: p95HER2 positive pts and PIK3CA mutations
in exon 9 or 20 were detected in 42% and 22% of tumor specimens,
respectively. p95HER2 positive tumors showed a shorter TTP and OS that
did not reach statistical significance; PIK3CA mutations correlated with a
worse TTP (median 7,6 vs 11,3 months) and OS (median 20,1 vs 41,0
months, p� 0,046). Conclusions: These preliminary results suggest a
possible role of PIK3CA mutational status in predicting the outcome of
MBC pts treated with T.
628 General Poster Session (Board #12G), Sat, 8:00 AM-12:00 PM
Detection of trastuzumab (T) level in human serum using quartz crystal
microbalance (QCM) piezo-immunosensors by immobilization of a HER2
mimotope-derived synthetic peptide and its potential application in breast
cancer. Presenting Author: Mohammad Muhsin Chisti, Oakland University
William Beaumont School of Medicine, Royal Oak, MI
Background: Varied clinico-pathological response to monoclonal antibodies
like T has been reported either due to presence of antibodies, rapid
clearance or low density of target receptor/antigens. This demands need for
an assay to monitor serum T therapeutic levels to ensure appropriate
dosage. Enzyme-linked immunosorbent assay (ELISA) is still the most
widely used technique to detect T level in human serum which is expensive
and time consuming. For the first time, we established a platform to detect
T level by using a small (�2.2 kDa), inexpensive, highly stable HER2
mimotope-derived synthetic peptide immobilized on the surface of a gold
quartz electrode. Methods: HER2 mimotope was used as a substitute for the
HER2 receptor protein in QCM assays to detect T level. The validation
samples were prepared from the standard T solution in 10% human serum
at three concentrations (10, 20 and 40 ug/ml). The changes in frequencies
(�F) of sera from 3 female patients , 61, 32 and 44 years old , with ER/PR
positive, HER2/neu positive metastatic breast cancer were obtained by
calculating the differences between frequency shifts in pre and post T
infusion.T level was calculated by equation, (�F �1.0022) ÷ 0.9997 �g /
ml. Results: We showed that assay sensitivity was dependent upon the
amino acids used to tether and link the peptide to the sensor surface and
the buffers used. QCM assay was capable of detecting T serum level as low
as 0.038 nM (linear operating range of 0.038–0.859 nM). T levels of 3
patients were 43.34, 121.96 and 193.18 �g /ml corresponding to pre and
post infusion �F of 3.33, 11.19 and 18.31 respectively. The time frame of
assay was 20-30 minutes. These results were in concordance with
previously published results using ELISA. Conclusions: For the first time, we
have established a low cost, highly sensitive, fast, synthetic peptide based
QCM assay which could be used as a basis for developing a new generation
of affinity-based Immunosensor assays to monitor serum levels of T and
other monoclonal antibodies, helping physicians to determine the clinical
efficacy of these drugs and ensuring appropriate dosages.
630 General Poster Session (Board #13A), Sat, 8:00 AM-12:00 PM
Impact of single/dual HER2 inhibition and chemotherapy (CT) backbone
upon pathologic complete response (pCR) in patients receiving neoadjuvant
CT for operable/locally advanced breast cancer (O/LABC): A treatmentinteraction
analysis of randomized trials. Presenting Author: Jenny
Furlanetto, Medical Oncology, University of Verona, Verona, Italy
Background: Although the addition of trastuzumab to neoadjuvant CT for
O/LABC have dramatically increased pCR, clinical research is moving
forward to further improve the overall outcome. In this regard, the DUAL
inhibition of the HER-2 pathway and the choice of the best CT backbone
may represent an issue to be addressed. Methods: Phase II randomized/
Phase III trials were considered. pCR events/rates were extracted from
papers/presentation and cumulated (R[pCR]) according to a random-effect
model; 95% confidence intervals (CI) were derived. A sensitivity analysis
according to SINGLE/DUAL HER-2 inhibition and to administered CT
(anthracyclines-taxanes: anthra-TAX; TAX alone) was accomplished, in
order to test for interaction. Results: 7 trials (2155 pts) were gathered;
1855 pts were enrolled in arms where anti-HER-2 targeted therapy was
administered. HER-2 inhibition was obtained with trastuzumab, lapatinib
and pertuzumab (alone or combined). Results according to HER-2 inhibition
follow in the table below. With regard to CT, a significant interaction
(p�0.0001) in favour of the addition of Anthra to TAX was found in the
context of SINGLE HER-2 inhibition subgroup (R[pCR] 46.5%, 95% CI
37-51, vs 26.9%, 95% CI 23-31), while no significant interaction was
determined in the context of the DUAL subgroup (R[pCR] 49.0%, 95% CI
26-72, vs 49.0%, 95% CI 43-55). A significant interaction (p�0.0001) in
favour of the addition of Anthra to TAX was found for pts receiving
trastuzumab (R[pCR] 45.5%, 95% CI 37-53, vs 26.5%, 95% CI 21-32) as
well. Conclusions: Although biases in the pCR definition, the DUAL
inhibition of HER-2 pathway may significantly increase pCR, regardless of
the CT backbone; if confirmed, this strategy allows to reduce toxicities by
sparing Anthra. For pts receiving SINGLE HER-2 inhibition, Anthra-TAXbased
CT should be still considered the best treatment option.
Anthra-TAX TAX
Single Dual Single Dual
pCR (n°)/pts 259/591 139/390 136/506 127/259
R[pCR] (95% CI) 46.5% (37-51) 49.0% (26-72) 26.9% (23-31) 49.0% (43-55)
Interaction test p�0.67 p�0.0001
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