Abstract P3-04-02: Absence of PTEN facilitates the anti-tumor efficacy of GDC-0980 in combination with ABT888 plus carboplatin in BRCA1-competent triple negative breast cancer

Introduction: PI3K pathway, in addition to its pro-proliferative and anti-apoptotic effects on tumor cells, is known to contribute to DNA-damage repair (DDR). We hypothesized that GDC-0980, a dual PI3K-mTOR inhibitor, will induce an efficient anti-tumor effect in BRCA-competent PTEN-null TNBC cells when combined with PARP inhibitor, ABT888 and carboplatin. We propose that in PTEN-null BRCA-competent TNBC model, the growth of TNBC tumor will be blocked due to the inhibition of (1) HR and NHEJ and (2) PI3K-mTOR pathway mediated survival signals following treatment with GDC-0980, when combined with PARP inhibitor (impaired DNA-SSB-repair) and carboplatin (increased DNA-DSB). Purpose: Here we tested the efficacy of a combination of GDC-0980 with ABT888 plus carboplatin in BRCA-competent PTEN-null model of TNBC. Methods: Athymic mice bearing PTEN-null TNBC xenograft tumors were treated with GDC-0980 alone or in combination with ABT888 and carboplatin. Results: Dual inhibition of PI3K and mTOR by GDC-0980 alone as well as in the presence of carboplatin plus ABT888 changed the state of the repair of DNA-damage in BRCA-competent PTEN null TNBC cells, which led to increased cellular apoptotic signals in addition to decreased survival/proliferative signals. GDC-0980 treatment led to DNA damage (increased pgH2AX), gain in PAR and a subsequent sensitization of BRCA-competent PTEN-null MDA-MB468 TNBC cells to ABT888 plus carboplatin with a time-dependent (1) decrease in proliferation signals (pAKT T308/S473, pP70S6K, pS6RP), PAR/PARP ratios, PAR/pgH2AX ratios, live/dead cell ratios, cell-cycle progression and clonogenic 3D growth and (2) increase in apoptosis markers (cleaved-caspase 3, 9, BIM, cleaved-PARP and annexinV positivity). These effects are more pronounced in MDA-MB468 than in RAS/RAF mutated MDA-MB231 cells. GDC-0980 alone and in combination with ABT888 plus carboplatin inhibited cell cycle progression, increased apoptosis, and decreased live/dead cell ratios in BRCA-competent PTEN null TNBC cells. GDC-0980 alone and in combination with ABT888 plus carboplatin attenuated anchorage -dependent and -independent clonogenic 3D growth comparatively more in BRCA-competent PTEN-null cells TNBC cells than MDA-MB231 cells. GDC-0980 in combination with ABT888 plus carboplatin blocked the growth of established PTEN-null TNBC tumors as compared to vehicle control(s) with a concomitant decrease in tumor Ki67 and CD31 IHC-stains. Conclusion: This is the first mechanism-based study to demonstrate that in BRCA-competent PTEN-null TNBC model, GDC-0980 enhanced antitumor activity of ABT888, in the presence of carboplatin by inhibiting DDR system in conjunction with the inhibition of PI3K-mTOR pathway-mediated proliferative, and anti-apoptotic signals. Considering (1) the importance of PARP as the target in TNBC, (2) the existence of a large percentage of BRCA-competent TN and/or basal type BC patients and (3) the high frequency of PTEN-null-ness in this subset of BC, this combination merits further investigation.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-04-02.

Abstract P6-05-09: Development of a predictive biomarker gene expression signature for the PIK3CA inhibitor, GDC-0032, in breast cancer cells

Introduction

The PI3-Kinase pathway is one of the most commonly mutated pathways in cancer and plays a major role in cell proliferation and survival. Mutations in PIK3CA, the gene encoding the p110 subunit of PI3K, are among the most common alterations in breast cancer, occurring in approximately 45% of luminal A, 30% of luminal B, 30% of HER2 positive and 8% of triple negative breast cancers. Additional pathway activating alterations include loss of PTEN, AKT mutations and overexpression of PIK3CA and HER2. Development of a pharmacodynamic biomarker is challenging with the more isoform specific PI3K inhibitors as multiple upstream pathways can funnel into common downstream immunohistochemical evaluable endpoints. In addition, phosphorylated epitopes are often labile and do not always lend themselves to immunohistochemical evaluation in the clinical setting. GDC-0032, which is currently under clinical investigation, is a class I PI3K inhibitor with 30-fold less inhibition on PI3K beta relative to PI3K alpha, and the development of a predictive and on-study pharmacodynamic signature may prove informative as compared to traditional IHC endpoints.

Methods

We screened a panel of 53 breast cancer cell lines, incorporating all subtypes, to GDC-0032 using the cell proliferation assay cell titer glo. To determine if there was a relationship between pathway activation and sensitivity to GDC-0032, we correlated response to PIK3CA mutations, loss of PTEN and HER2 overexpression. Using RNA sequencing, we compared the baseline gene expression between the sensitive and refractory cell lines. Next, to identify an on-study pharmacodynamic gene expression signature, we treated both sensitive and refractory cell lines with GDC-0032 and ran an in-house custom designed 800 gene NanoString breast cancer gene set that incorporated published PI3K pathway signatures, intrinsic subtyping genes and immunological related genes. Finally, the GDC-0032 signature was applied to a set of 160 FFPE breast cancer samples and overlaid with relevant biomarkers.

Results and Conclusions

Sensitivity to GDC-0032 correlated strongly with PI3K pathway activation including PIK3CA mutations and HER2 overexpression in breast cancer cells. Comparing baseline whole genome RNA expression of GDC-0032 sensitive and refractory cell lines, we identified 293 genes that were differentially expressed. Applying a more stringent statistical cutoff (greater than 2 fold difference and t-test less than 0.01) refined the gene list to 51 genes, which defined the baseline GDC-0032 sensitivity signature. Applying the 800 gene breast cancer NanoString panel to a set of 160 FFPE breast cancer samples, the GDC-0032 sensitivity signature correlated with luminal status and was enriched in PIK3CA mutant tumors. In conclusion, our in-house designed GDC-0032 sensitivity signature correlated strongly with PIK3CA mutations in clinical specimens. However the lack of complete correlation may identify tumors that have an activated PI3K pathway outside of PIK3CA mutations and/or HER2 amplification that may derive clinical benefit from GDC-0032.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-05-09.

Abstract P5-06-01: The PI3K inhibitor GDC-0941 combines with trastuzumab for superior anti-tumor efficacy in HER2+ breast cancer models

Background: PI3K-AKT-mTOR pathway signaling is important for the oncogenic function of HER2. Activating alterations of this pathway are frequently observed in HER2-enriched breast cancer and generally herald a poor response and resistance to trastuzumab (T). Purpose: Targeting the PI3K-AKT-mTOR pathway is an attractive strategy in HER2+ breast cancer that is refractory to trastuzumab. The hypothesis is that the suppression of this pathway by pan-PI3K inhibitor, GDC-0941 may lead to overcome trastuzumab-resistance. Experimental Design: The antiproliferative and HER2-mediated cellular signaling (pAKT, pP70S6K, pS6RP, p4EBP1 and p-ERK) effects of GDC-0941 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. Clonogenic growth was tested by 3D ON-TOP assay and apoptosis markers were also tested. Athymic mice bearing BT474 and BT474HR xenograft tumors were treated with GDC-0941 and T (alone and in combination). Results: (1) GDC-0941 exhibited in vitro cell killing activity in MTT assay with IC50's ranging from 0.35 μM to 1 μm and potency was augmented by the addition of T, (2) inhibition of phosphorylation of AKT(S473, T308), P70S6K, S6RP, and 4EBP1(T37/46, T70) was observed following GDC-0941 treatment, and the combination of GDC-0941 and T more effectively blocked the PI3K-AKT-mTOR pathway, (3) GDC-0941 treatment increased apoptosis markers (CL-CASPASE3 and annexinV positivity), (4) GDC-0941 dose-dependently blocked 3D-ON-TOP clonogenic growth of HER2+ cells. This effect was potentiated in the presence of T and (5) in vivo, the combination of GDC-0941 and T significantly reduced established tumor growth in both sensitive (82%) and resistant (79%) models with concomitant decrease of different PD markers. 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, and 2) targeting both the HER2 and the PI3K signaling pathways is an attractive strategy to enhance the clinical efficacy of T therapy, as well as to prevent or delay the development of resistance.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-06-01.

Abstract P5-19-02: Selective PI3K and dual PI3K/mTOR inhibitors enhance the efficacy of endocrine therapies in breast cancer models

Purpose: Phosphoinositide 3-kinases (PI3K) are lipid kinases that can regulate breast tumor cell growth, migration and survival. Standard of care drugs such as estrogen receptor (ER) antagonists including fulvestrant and tamoxifen, and aromatase inhibitors such as letrozole are indicated for the treatment of hormone receptor positive breast cancer. The current study is focused on investigating preclinical activity in breast cancer models, for GDC-0941, a class I PI3K inhibitor, GDC-0032, a PI3K inhibitor, and GDC-0980, a dual mTOR kinase and class I PI3K inhibitor. Investigation into PI3K inhibitor efficacy in combination with endocrine therapies is also explored.

Experimental Design: A panel of ER+ breast cancer cell lines were treated with GDC-0941, GDC-0032 and GDC-0980 either as single agents or in combination with fulvestrant or tamoxifen and assayed for cellular effects. MCF-7 cells ectopically expressing aromatase were utilized to test the efficacy of aromatase inhibitors in combination with PI3K inhibitors in vitro. In addition, human xenografts of breast cancer cell lines were employed to assess combination efficacy of PI3K inhibitors with fulvestrant and tamoxifen in vivo.

Results: Combination of GDC-0941, GDC-0032 or GDC-0980 with endocrine therapies resulted in a decrease in cellular viability and an increase in cell death. Synergy of PI3K inhibitor combinations with fulvestrant or tamoxifen was assessed using Combination Index (C.I.), and C.I. values as low as 0.1 indicated strong synergy in some contexts. Combination activity of PI3K inhibitors and letrozole was also observed in MCF7 cells expressing aromatase. In MCF-7 xenografts, the combination of GDC-0980, GDC-0032 and GDC-0941 enhanced activity of fulvestrant resulting in tumor regressions and tumor growth delay (116% tumor growth inhibition (TGI) for GDC-0980 and 91% TGI for GDC-0941 and GDC-0032). In addition, the combination of GDC-0941 or GDC-0032 with tamoxifen enhanced the efficacy of tamoxifen in vivo (83%TGI for GDC-0941 and 102%TGI for GDC-0032). Mechanism of action and biomarker studies are underway.

Conclusion: Collectively, the non-clinical efficacy data provide a strong rationale to evaluate the combination of PI3K inhibitors with anti-estrogen therapy in hormone receptor positive breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-19-02.

"Cluster-ion" bombardment of biological macromolecules: Morphological evidence for disassembly of single tobacco mosaic virus particles

Cluster ions containing 50, 100, or 200 water molecules and one proton are accelerated to over 275 kV and impacted on thin carbon films on which tobacco mosaic virus has been dispersed. After bombardment the films are examined with a transmission electron microscope to study induced morphological alterations with respect to the energy transfer processes that take place during and after single cluster-ion impact. Observations on tobacco mosaic virus indicate that a single cluster impact results in the removal of a cylindrical segment of the virus. No fragments from the excised TMV segment were observed on the carbon foil. We speculate that cluster-ion bombardment may become a useful analytical technique for structural studies of large biological macromolecular complexes.

Non-pharmacologic management of sleep disturbance in Alzheimer's disease

Sleep and wake in Alzheimer's disease (AD) are often fragmented as manifested by bouts of wakefulness at night and napping during the day. Management of sleep disturbances in AD is important because of their negative impact on both patients and caregivers. Pharmacological treatments, mainly sedative-hypnotics and antipsychotics, are often used but can be associated with significant adverse effects. Non-pharmacological treatments represent a beneficial alternative approach to the management of sleep disturbances in AD since they are associated with fewer adverse effects and their efficacy can be sustained after treatment has been completed. The aim of this article is to review non-pharmacological treatments, such as sleep hygiene, sleep restriction therapy (SRT), cognitive behavioral therapy (CBT), light therapy, and continuous positive airway pressure (CPAP), for the management of sleep/wake disturbances in AD.

Scottish court dismisses a historic smoker's suit

The decision in a Scottish smoker's case, McTear v. Imperial Tobacco Limited, that there was no scientific proof of causation between the plaintiff's smoking and his death from lung cancer, accepted all of the traditional arguments that the tobacco industry has made throughout the history of tobacco litigation, including that epidemiology is not an adequate branch of science to draw a conclusion of causation, that the tobacco industry has no knowledge that its products are dangerous to consumers, and that, despite this lack of knowledge, the plaintiff had sufficient information to make an informed decision about the dangers of smoking. This case relied on outmoded methods of reasoning and placed too great a faith in the tobacco industry's timeworn argument that "everybody knew, nobody knows". Further, the judge found it prejudicial that the plaintiff's expert witnesses were not paid for their services because she was indigent, believing that the lack of payment placed in doubt their credibility and claiming that the paid tobacco expert witnesses had more motive to testify independently because they had been paid, a perverse and novel line of reasoning. The McTear case contrasts unfavourably with the recent decision in United States v. Philip Morris, a United States decision that found the tobacco industry defendants to be racketeers, based both on the weight of a huge amount of internal tobacco industry documents showing that the tobacco industry knew their products were addictive and were made that way purposely to increase sales, and on the testimony of expert witnesses who, like those who testified in McTear, have made the advancement of the public health their life's work and are not "hired guns". The McTear case's reasoning seems outdated and reminiscent of early litigation in the United States. Hopefully, it will not take courts outside of the United States 40 more years to acknowledge the current scientific knowledge about smoking and health.

Adherence to anemia treatment guidelines in U.S. community oncology practices

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Background: Adherence to anemia guidelines may improve patient outcomes including health-related quality of life. This analysis presents baseline guideline adherence among community-based oncology practices prior to an educational intervention targeted to health care providers to improve adherence to anemia guidelines. Methods: Medical records of a sequential sample of adult cancer patients receiving chemotherapy from 47 participating sites during the year prior to site randomization to an educational intervention were abstracted. Each chart was analyzed to determine (1) whether or not the patient met the criteria for anemia treatment with an erythropoiesis- stimulating agent (ESA) or a blood transfusion, and (2) whether the patient received anemia treatment. A complex algorithm was developed to evaluate whether treatment adhered to guideline recommendations. Results: This baseline analysis included 2463 patient charts. Most patients were female (66%); with a mean duration of cancer of 14.5 months and a mean age of 61.8 years. According to guidelines, 523 patients (21%) met the criteria for anemia treatment and of these, 286 (55%) received an ESA or transfusion. In 1103 patients (45%), guidelines suggested that anemia treatment may be inappropriate. However, 216 (20%) of the 1103 patients for whom guidelines recommend against treatment received an ESA or transfusion. For 837 patients (34%), the guidelines did not provide a definitive recommendation and 242 (29%) of such patients received an ESA or transfusion. Conclusions: Baseline assessment found that many patients did not receive treatment consistent with anemia guidelines. This study will evaluate whether a year long educational intervention can improve clinician adherence to guideline recommendations, thereby improving patient outcomes.

No significant financial relationships to disclose.

Prophylaxis of chemotherapy-induced neutropenia: Patterns of care in U.S. community oncology practices

9123

Background: Adherence to neutropenia guidelines may improve patient outcomes and decrease costs associated with febrile neutropenia (FN). This analysis presents baseline data on patterns of colony-stimulating factor (CSF) use among community-based oncology practices prior to an educational intervention targeted to health care providers to improve adherence to CSF guidelines from the National Oncology Alliance (NOA). Methods: Medical records were identified from 47 participating sites. Abstractors collected data from a sequential sample of adult cancer patients receiving chemotherapy during the year prior to site randomization to an educational intervention (June and August 2006). A complex algorithm was developed to identify patients for whom the NOA guidelines recommend primary prophylaxis with a CSF including (1) patients receiving a chemotherapy regimen with a >20% expected risk of FN and (2) patients receiving chemotherapy with a 10–20% risk of FN and who have one of the following risk factors present: diminished performance status or non-Hodgkin's lymphoma with low serum albumin or high serum LDH or spread to bone marrow. Results: 2594 patients were evaluated for this analysis. Most were female (66%) and the mean age was 61.7 years (± 13.1). During this period (2005–06), 423 (16%) patients received chemotherapy regimens with an FN risk >20% and 143 (6%) received chemotherapy regimens with an FN risk of 10–20% and had a risk factor. Of patients receiving chemotherapy with a >20% risk of FN, 176 (42%) received CSF primary prophylaxis. Of patients receiving chemotherapy with a 10–20% risk FN with a risk factor present, 40 (28%) received CSF primary prophylaxis. Conclusions: Many patients for whom guidelines recommend treatment did not receive CSF primary prophylaxis. After the year-long educational intervention, we will re-evaluate CSF patterns of care and assess whether adherence to guidelines improved patient outcomes.

No significant financial relationships to disclose.