Complex effects of inhibiting hepatic apolipoprotein B100 synthesis in humans

Mipomersen is a 20mer antisense oligonucleotide (ASO) that inhibits apolipoprotein B (apoB) synthesis; its low-density lipoprotein (LDL)-lowering effects should therefore result from reduced secretion of very-low-density lipoprotein (VLDL). We enrolled 17 healthy volunteers who received placebo injections weekly for 3 weeks followed by mipomersen weekly for 7 to 9 weeks. Stable isotopes were used after each treatment to determine fractional catabolic rates and production rates of apoB in VLDL, IDL (intermediate-density lipoprotein), and LDL, and of triglycerides in VLDL. Mipomersen significantly reduced apoB in VLDL, IDL, and LDL, which was associated with increases in fractional catabolic rates of VLDL and LDL apoB and reductions in production rates of IDL and LDL apoB. Unexpectedly, the production rates of VLDL apoB and VLDL triglycerides were unaffected. Small interfering RNA-mediated knockdown of apoB expression in human liver cells demonstrated preservation of apoB secretion across a range of apoB synthesis. Titrated ASO knockdown of apoB mRNA in chow-fed mice preserved both apoB and triglyceride secretion. In contrast, titrated ASO knockdown of apoB mRNA in high-fat-fed mice resulted in stepwise reductions in both apoB and triglyceride secretion. Mipomersen lowered all apoB lipoproteins without reducing the production rate of either VLDL apoB or triglyceride. Our human data are consistent with long-standing models of posttranscriptional and posttranslational regulation of apoB secretion and are supported by in vitro and in vivo experiments. Targeting apoB synthesis may lower levels of apoB lipoproteins without necessarily reducing VLDL secretion, thereby lowering the risk of steatosis associated with this therapeutic strategy.

Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA

We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) μg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.

Abstract P3-07-08: Quantitative HER family proteins assessment as prognostic and predictive biomarkers in the EGF30008 clinical trial

Background

Combined targeted strategy with letrozole (Le) and lapatinib (La) improves progression-free survival (PFS) in patients with metastatic breast cancer (MBC) co-expressing hormone receptor-positive (HR+) and HER2+ but not in HR+/HER2-negative (HER-) disease (Johnston J Clin Oncol 2009). However, among HER2+ tumors, quantitative levels of HER2 are heterogeneous with a broad dynamic range corresponding to approximately 163.7 to 17446.7 amol/µg as previously reported (Nuciforo SABCS 2014). In addition, within HER2- tumors, quantitative measurement of HER family proteins may identify those patients most likely to benefit from the addition of La to Le. In this retrospective study, we tested the prognostic and predictive ability of HER proteins quantification in clinically HER2+ tumor samples from the EGF30008 study.

Methods

Formalin-fixed paraffin-embedded primary tumor tissues sections from HER2+ MBC population were used. After laser microdissection, tissue lysates were prepared for selected reaction monitoring mass spectrometry (SRM-MS) analysis. Absolute quantitation was accomplished through simultaneous detection of endogenous target and synthetic labeled heavy peptide identical to analytical targets (EGFR, HER2, HER3). HER2 protein levels were correlated with PAM50 molecular subtypes, ERBB2 and ESR1 genes by nCounter. PFS and overall survival (OS) were analyzed by Kaplan–Meier and log-rank test. To determine whether HER2 protein levels were predictive of La benefit, we tested the interaction term of HER2 protein as a continuous variable by treatment arm in a Cox model.

Results

Within the HER2+ study cohort (n=219), 107 had an available tumor block; 84 cases had sufficient material for HER expression measurement by SRM-MS. Average HER2 levels were

2321.1 amol/ug (median, 817.6). HER2 levels were lower in Le+La (n=43; mean, 1761 amol/ug) compared to Le (n=41; mean, 2908 amol/ug) arms, although the difference was non-significant (p=0.108). No expression of EGFR and HER3 was observed. HER2 protein levels were significantly different among PAM50 subtypes with HER2-enriched (HER2E) tumors showing the highest expression followed by Basal-like, Luminal A, Luminal B, and Normal-like (p&lt;0.001). A correlation between HER2 protein, ERBB2 (r=0.5, p&lt;0.001) and ESR1 (r=-0.5, p=0.001) gene expression was found. In patients with disease that expresses HER2 protein levels above the median a trend towards worse PFS (2.9 vs 7.7 months, p=0.092) and OS (21 vs 39 months, p=0.071) were observed. A statistically significant interaction was observed between HER2 protein levels and La treatment for both PFS (p=0.049) and OS (p&lt;0.001). HER2+ tumors with lower expression of HER2 benefited more from La than those with higher expression.

Conclusions

Levels of HER2 protein in HER2+ MBC are extremely heterogeneous. An association between HER2 protein and gene expression by nCounter was observed. HER2E tumors by PAM50 showed the highest levels of HER2 protein. Within the group of HER2+ MBC by standard IHC/FISH, tumors with high HER2 protein had a statistically non-significant worse outcome and do not seem to benefit from La. Further validation of these findings is warranted.

Citation Format: Nuciforo P, Thyparambil S, Galván P, Vilaro M, Jimenez J, Liao W-L, Cecchi F, Blackler A, Press MF, Gagnon R, Ellis C, Hembrough T, Johnston S, Prat A. Quantitative HER family proteins assessment as prognostic and predictive biomarkers in the EGF30008 clinical trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-08.

Abstract P4-09-02: Concordance in fibroblast growth factor receptor 1 (FGFR1) and 2 (FGFR2) status in breast cancer during tumor progression

BACKGROUND: In recent years, changes in HER2 and hormone receptor (HR) status between primary and metastatic breast cancer (BC) have been extensively reported. Additionally, current advances in BC biology have identified emerging biomarkers with clinical and prognostic implications, particularly the PI3K-AKT-mTOR and the FGF/FGFR pathways. FGFR1 and FGFR2 gene amplifications represent the most frequent genomic aberrations in BC. The 8p11-12 chromosomal region harboring the FGFR1 gene locus is amplified in about 10-18% of human BC, mainly in HR-positive/HER2-negative subtype, whereas the FGFR2 gene, located on chromosome 10q26, is amplified in approximately 4% of triple negative BC. To our knowledge, there is a lack of data regarding the concordance of FGFR1 and FGFR2 status between primary and metastatic tumors.

METHODS: Tumor samples from 205 and 67 advanced BC patients diagnosed at our institution between 2010 and 2014 were screened for FGFR1 and FGFR2 amplification by FISH using the ZytoLight SPEC FGFR1/CEN8 and FGFR2/CEN10 probes, respectively. FGFR1 and FGFR2 amplification were defined as a ratio of FGFR1/CEN8 and FGFR2/CEN10 ≥ 2.2. We investigated the correlation of FGFR1 and FGFR2 status between primary and metastatic tumors in 16 and 13 patients, respectively, for whom paired samples were available.

RESULTS: A total of 47 FGFR1-amplified patients (22.9%) and 3 FGFR2-amplified patients (4.5%) were identified. Patients with paired samples were classified according to FGFR1 and FGFR2 status in primary tumor. Regarding FGFR1 amplification, eight patients were FGFR1-amplified and eight were FGFR1-non-amplified. One patient in each group showed discordance in FGFR1 status in the metastatic tumor. Overall rate of concordance between primary and metastatic tumors was 87.5% (14/16). In relation to FGFR2 status, two patients were FGFR2-amplified and 11 were FGFR2-non-amplified with a 100% overall rate of concordance between paired samples (13/13). These data are summarized in Table 1.

Table 1  Metastases PrimaryAmplifiedNon-amplifiedFGFR1Amplified (n=8)71 Non-amplified (n=8)17FGFR2Amplified (n=2)20 Non-amplified (n=11)011

CONCLUSIONS: Results suggest a high concordance in FGFR1 and FGFR2 status between primary and metastatic BC. The potential impact of these findings on the development of FGFR inhibitors merits further investigation.

Citation Format: Zamora E, Aura C, Perez-Garcia J, Prudkin L, Meire A, Muñoz Cosuelo E, Jimenez J, Diaz-Delgado M, Ortega V, Soberino J, Farinas L, Salva F, Bellet M, Cruz C, Gomez P, Oliveira M, Vidal MJ, Saura C, Cortes J, Nuciforo P. Concordance in fibroblast growth factor receptor 1 (FGFR1) and 2 (FGFR2) status in breast cancer during tumor progression. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-02.

Benefit to neoadjuvant anti-human epidermal growth factor receptor 2 (HER2)-targeted therapies in HER2-positive primary breast cancer is independent of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) status

BACKGROUND

Assessment of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) might be an important tool in identifying human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients unlikely to derive benefit from anti-HER2 therapies. However, studies to date have failed to demonstrate its predictive role in any treatment setting.

PATIENTS AND METHODS

Prospectively collected baseline core biopsies from 429 early-stage HER2-positive breast cancer patients treated with trastuzumab, lapatinib, or their combination in the Neo-ALTTO study were stained using two anti-PTEN monoclonal antibodies (CST and DAKO). The association of PTEN status and PI3K pathway activation (defined as either PTEN loss and/or PIK3CA mutation) with total pathological complete response (tpCR) at surgery, event-free survival (EFS), and overall survival (OS) was evaluated.

RESULTS

PTEN loss was observed in 27% and 29% of patients (all arms, n = 361 and n = 363) for CST and DAKO, respectively. PTEN loss was more frequently observed in hormone receptor (HR)-negative (33% and 36% with CST and DAKO, respectively) compared with HR-positive tumours (20% and 22% with CST and DAKO, respectively). No significant differences in tpCR rates were observed according to PTEN status. PI3K pathway activation was found in 47% and 48% of patients (all arms, n = 302 and n = 301) for CST and DAKO, respectively. Similarly, tpCR rates were not significantly different for those with or without PI3K pathway activation. Neither PTEN status nor PI3K pathway activation were predictive of tpCR, EFS, or OS, independently of treatment arm or HR status. High inter-antibody and inter-observer agreements were found (>90%). Modification of scoring variables significantly affected the correlation between PTEN and HR status but not with tpCR.

CONCLUSION

These data show that PTEN status determination is not a useful biomarker to predict resistance to trastuzumab and lapatinib-based therapies. The lack of standardization of PTEN status determination may influence correlations between expression and relevant clinical end points.

CLINICAL TRIALS

This trial is registered with ClinicalTrials.gov: NCT00553358.

Abstract 634: Treatment with Mipomersen Reduces Levels of ApoB-Containing Lipoproteins by Increasing Fractional Removal of VLDL and LDL-apoB Without Reducing VLDL-apob Secretion

Objectives: Mipomersen (MIPO), a second generation antisense oligonucleotide, targets apoB mRNA, thereby inhibiting apolipoprotein B (apoB) synthesis. In humans, MIPO reduces plasma levels of low density lipoprotein-cholesterol (LDL-C), and plasma triglycerides (TG). We hypothesized that these changes are due to reduced assembly and secretion of very low density lipoproteins (VLDL) and lower production of LDL.

Methods: Healthy volunteers (HVs) (9M, 8F), mean age 43.5 ± 14.2 yr, completed a single-blind, fixed-sequence, phase I study. They received sc-placebo injections once weekly for 3-wks followed by 200mg sc-MIPO injections once weekly for 7-9 wks. Stable isotope turnover studies were performed after each treatment. Blood samples were collected over 48-hrs to determine fractional catabolic rates (FCRs) and production rates (PRs) of apoB in VLDL, IDL, and LDL, and of TG in VLDL. Rates of de novo lipogenesis (DNL) were also measured.

Results: MIPO treatment resulted in significant reductions in plasma LDL-C (45%), TG (29%), and apoB (40%). VLDL, IDL, and LDL apoB levels fell by 29%, 25%, and 42%, respectively. These changes were associated with increases in FCRs of VLDL apoB (42%) and LDL apoB (30%), and by reductions in PRs of IDL apoB (15%) and LDL apoB (27%). The PR of VLDL apoB was unaffected. The FCR of VLDL-TG increased 46% without change in PR. DNL did not change.

Conclusion: In summary, 7 wks of MIPO significantly reduced levels of all apoB-lipoproteins in HVs by increasing the FCRs of VLDL and LDL apoB. The absence of a reduction in VLDL apoB secretion is consistent with many studies in isolated hepatocytes demonstrating both intracellular degradation and secretion of newly synthesized apoB. Thus, if MIPO submaximally inhibited apoB synthesis in this study, the liver could have compensated by increasing the efficiency of VLDL assembly and secretion. The basis of increases in VLDL and LDL FCRs requires further investigation.

Electromagnetic interaction between a laser beam and semiconductor nanowires deposited on different substrates: Raman enhancement in Si Nanowires

Raman scattering of Si nanowires (NWs) presents antenna effects. The electromagnetic resonance depends on the electromagnetic coupling of the system laser/NW/substrate. The antenna effect of the Raman signal was measured in individual NWs deposited on different substrates, and also free standing NWs in air. The one phonon Raman band in NWs can reach high intensities depending on the system configuration; values of Raman intensity per unit volume more than a few hundred times with respect to bulk substrate can be obtained.

Abstract PD1-7: Phosphatase and tensin homolog deleted from chromosome 10 (PTEN) evaluation in the NeoALTTO trial (BIG 01-06)

Introduction

Assessment of PTEN might be an important tool in identifying patients unlikely to derive substantial benefit from trastuzumab and lapatinib-based therapies. Current studies failed to demonstrate an unequivocal predictive role of PTEN in human epidermal growth factor receptor-2 (HER2)-positive breast cancer both in neo-adjuvant and adjuvant settings. Lack of standardization of PTEN status determination in formalin fixed paraffin embedded (FFPE) tissue samples together with the small datasets analyzed in previous studies may have contributed to conflicting PTEN results and high variability of PTEN loss rates reported (22%-64%).

Methods

In the present study we have conducted a preliminary analysis investigating the influence of the antibodies, scoring methods and cutoff criteria used, together with the impact of inter-observer variability on PTEN status determination. Core biopsies from 429 FFPE baseline samples from early-stage HER2-positive breast cancer patients prospectively collected in the neoALTTO trial were stained with two widely used anti-PTEN monoclonal antibodies (clone 6H2.1 from DAKO and clone 138G6 from Cell Signaling Technology-CST). Two different pathologists independently scored the slides using the H-score system. Two different cut-off criteria were used to define PTEN loss of expression: H-score &lt; 50 and ≤10% positive staining (any level of intensity).

Results

Out of 429 processed samples, 363 and 369 were evaluable for observer 1 (CST and DAKO, respectively) and 367 were evaluable for observer 2, with an average missing rate of 15%. A strong linear correlation was observed between CST and DAKO antibodies for both observers (R2 &gt; 0.7). After setting a cutoff for PTEN loss, the observed discordance rate was below 10%, with the number of discordant cases ranging from 28 to 33 (depending on the cut-off criteria and observer). Inter-observer correlation was strong with both antibodies (R2 = 0.8). Based on the cutoff criteria and antibodies used, inter-observer discordance rates ranged between 6% and 10%; the lowest rate observed at ≤10% cutoff threshold with CST antibody. PTEN was classified as “loss” in 23%, 19%, 16%, and 13% of cases by observer 1 and in 32%, 29%, 24%, 19% of cases by observer 2 using DAKO H-score&lt;50, CST H-score&lt;50, DAKO≤10%, and CST≤10% criteria, respectively.

Conclusion

Our preliminary analysis showed high inter-antibody and inter-observer concordant rates for PTEN status determination by IHC. However, the lack of a standardized definition of PTEN cutoff thresholds for defining negativity and positivity generated loss call rates ranging from 13% to 32% within the same dataset. Correlative analyses with pCR and PIK3CA status are ongoing to determine the impact of PTEN expression and its variability in predicting response to single-agent or dual HER2 targeting.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD1-7.

Abstract P1-07-19: Mass Spectrometry Based Quantitative Analysis of the HER Family receptors in FFPE Breast Cancer Tissue

The human EGF receptor family (HER's) consists of two clinically validated drug targets (EGFR and HER2), a third (HER3) currently under investigation for its possible role in the acquisition of multidrug resistance and a fourth (HER4), the role of which is still matter of debate. Drugs inhibiting EGFR or HER2 show significant antitumor activity in the clinic, however, acquisition of resistance is a hallmark of these and most targeted therapies. In the case of EGFR and HER2, one of the emerging resistance mechanisms is the co-expression of HER3. Indeed, recent reports show that inhibition of the PI3K pathway leads to upregulation of HER3, and subsequent resistance. Clinical analysis of protein levels in formalin fixed paraffin embedded (FFPE) tissues is limited to immunohistochemistry (IHC), which is semi-quantitative and requires significant amounts of tissue. Moreover, the vast majority of research groups consider specific HER3 staining by IHC particularly challenging. However, accurate measurement of these targets is critical both for properly defining treatment groups and predicting patterns of resistance.

In order to address these issues, we used trypsin digestion mapping and stable isotope labeled peptides to develop a panel of quantitative mass spectrometric (MS) assays to measure the levels of EGFR, HER2, HER3 and other clinically relevant targets in FFPE breast cancer tissue. These quantitative MS assays were then multiplexed to analyze 1μg of tumor protein.

In this study, we multiplexed HER family analysis on 31 HER2 positive breast cancers. Tumor tissue was microdissected from FFPE sections, and subjected to quantitative MS analysis of EGFR, HER2, HER3 as well as IGF1R and cMET. Quantitation of HER2 showed a broad range of HER2 expression in these tissues. The highest expresser measured 26 fmol/ug tumor tissue, representing amplification and massive protein over expression. In contrast, five tissues showed low levels of HER2 expression, below 1 fmol/ug, similar to HER2 non-amplified cell lines. This suggests that MS quantitation can identify patients with low expression of HER2 who are unlikely to respond to trastuzumab therapy. As a matter of fact, 3 of these 5 low expressing patients had outcome data and showed no response to trastuzumab treatment.

In 28 of 31 patient tissue samples, HER3 showed low levels of expression (100–300 amol/ug tumor tissue) similar to HER3 expression in cell lines, and comparable to low expressing EGFR and HER2 cell lines. The remaining 3 patients had no detectable HER3. This study demonstrates the feasibility of measuring HER3 in multiplex in FFPE breast cancer tissue. Based on the low but widespread expression of HER3 in this cohort, it may be most useful to assess HER3 expression after initial treatment as a marker of potential resistance to targeted therapies.

Taken together, these data demonstrate that a sensitive and quantitative assay to measure oncoproteins in FFPE clinical samples may help stratify patients with variable expression of these targets. Our quantitation of oncogene expression from clinical samples uses a small amount of tissue, is clinically applicable and alleviates the problem of scoring either positive or negative for the expression of a given protein.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-19.