The Fish Sexual Development Test (FSDT) is a non-reproductive test to assess adverse effects of endocrine disrupting chemicals. With the present study it was intended to evaluate whether gene expression endpoints would serve as predictive markers of endocrine disruption in a FSDT. For proof-of-concept, a FSDT according to the OECD TG 234 was conducted with the non-steroidal aromatase inhibitor fadrozole (test concentrations: 10μg/L, 32μg/L, 100μg/L) using zebrafish (Danio rerio). Gene expression analyses using quantitative RT-PCR were included at 48h, 96h, 28days and 63days post fertilization (hpf, dpf). The selection of genes aimed at finding molecular endpoints which could be directly linked to the adverse apical effects of aromatase inhibition. The most prominent effects of fadrozole exposure on the sexual development of zebrafish were a complete sex ratio shift towards males and an acceleration of gonad maturation already at low fadrozole concentrations (10μg/L). Due to the specific inhibition of the aromatase enzyme (Cyp19) by fadrozole and thus, the conversion of C19-androgens to C18-estrogens, the steroid hormone balance controlling the sex ratio of zebrafish was altered. The resulting key event is the regulation of directly estrogen-responsive genes. Subsequently, gene expression of vitellogenin 1 (vtg1) and of the aromatase cyp19a1b isoform (cyp19a1b), were down-regulated upon fadrozole treatment compared to controls. For example, mRNA levels of vtg1 were down-regulated compared to the controls as early as 48 hpf and 96 hpf. Further regulated genes cumulated in pathways suggested to be controlled by endocrine mechanisms, like the steroid and terpenoid synthesis pathway (e.g. mevalonate (diphospho) decarboxylase (mvd), lanosterol synthase (2,3-oxidosqualene-lanosterol cyclase; lss), methylsterol monooxygenase 1 (sc4mol)) and in lipid transport/metabolic processes (steroidogenic acute regulatory protein (star), apolipoprotein Eb (apoEb)). Taken together, this study demonstrated that the existing Adverse Outcome Pathway (AOP) for aromatase inhibition in fish can be translated to the life-stage of sexual differentiation. We were further able to identify MoA-specific marker gene expression which can be instrumental in defining new measurable key events (KE) of existing or new AOPs related to endocrine disruption.

3050 Background: Bevacizumab added to chemotherapy (CRx) prolongs PFS in pts with MBC. Data suggest that estrogen (E2) modulates VEGF-induced angiogenesis in physiologic and pathologic conditions. E2-induced VEGF expression may promote breast cancer growth therefore combination therapy with an aromatase inhibitor (AI) and an antibody to VEGF may be more effective than either agent alone. We performed a feasibility study testing B with L for the treatment (tx) of hormone receptor-positive MBC. Methods: Eligible pts have MBC and are candidates for AI therapy. Prior non-steroidal AI (NSAI) use without progression is permitted. Premenopausal pts undergo ovarian suppression/oophorectomy prior to tx. Therapy consists of L (2.5 mg daily) and B (15 mg/kg IV q3 weeks). The primary endpoint is frequency of Grade (Gr) 4 toxicity. Secondary endpoints include response rate, stable disease (SD) ≥ 6 mo and time to tumor progression. Using a two-stage design, 19 pts were accrued. Because <3 pts had Gr 4 toxicity, the 2nd stage is now enrolling an additional 23 pts. If <5 of the 42 pts have Gr 4 toxicity, the regimen will be considered feasible. Results: Thirty two pts are currently accrued and 28 are now evaluable. Medians: Age 49.5 yrs (32–77) and ECOG PS 0 (0–1). Sites of MBC: bone only 11/28, visceral 16/28, chest wall/soft tissue/lymph nodes 11/28. All are ER and/or PR (+); none are HER2 (+). Prior therapy: adjuvant CRx 20; adjuvant tamoxifen 14. Twenty five pts received an NSAI as first-line tx of MBC, starting a median of 23 wks (1–213) before B. Three pts received first-line tamoxifen; one pt had prior CRx for MBC. After a median of 8 cycles (1–20), tx-related toxicities: Gr 2: hypertension (HTN) 4, headache (HA) 4, proteinuria 3, fatigue 6, joint pain 5, hot flashes 1, epistaxis 1; Gr 3: HTN 5, HA 1, proteinuria 1. There has been no tx-related Gr 4/5 toxicity. Tx-related withdrawals: HTN 1 and headache 1. Twenty five pts are evaluable for response: PR 2, SD ≥ 6 mo 13, SD 4, progression 6. Conclusions: Combination L and B is well tolerated and will be studied in a randomized CALGB trial. Circulating endothelial and tumor cell data is reported separately. Supported in part by Genentech and Novartis. [Table: see text]

3039 Background: Antiangiogenic therapy has demonstrated efficacy in the treatment (tx) of metastatic breast cancer. Mechanism-based biomarkers of antiangiogenic therapy, if clinically validated, offer the potential to optimize this novel therapy. CECs have been proposed as a marker of tumor progression and/or response to antiangiogenic therapy with B. We performed a feasibility study testing B combined with L for the tx of hormone receptor-positive MBC. To explore markers of activity and response, we assayed CECs and circulating tumor cells (CTCs) at weeks (wks) 0 (baseline), 3, 12, and then Q 12 wks. Methods: CECs were defined as CD34/31+, CD45-. Progenitor (CD133+) (CECp) and activation markers (CD106+) were also measured. For CECs, 50 ul of blood was stained with the indicated MAbs; after RBC lysis, flow cytometry (FC) was performed for total CEC and CECp. For CTCs, 20 ml of blood was subjected to immunomagnetic capture using anti-EpCAM ferrofluid, followed by FC for EpCAM, CD45, and nucleic acid content. The log rank test was used to test for significant differences related to response. Results: 32 of 42 pts have been enrolled. As separately reported, prior non-steroidal AI (NSAI) use without progression is permitted; median (med) time on L before start of B was 6 mo (1–52). 28 pts have at least baseline and week 3 CEC and CTC along with clinical response data. Med CEC level at baseline was 10.4 CEC/ul (4–38); the peak value at any time point was 107. CTC levels were much less frequent with a med of 0.3 CTC/ml (0–95, and highest value 1153). An increase in CECs at wk 3 compared to wk 0 predicted worse PFS (p = 0.015). CTCs were ≤ 0.1 at study start in 40% of pts and ≥ 1.0 in only 17%, likely due to length of prior L; change in values at wk 3 did not correlate with PFS in this pretreated group. Conclusions: Consistent with our previous results in a separate trial of B containing treatment in MBC, changes in CEC levels appear to be a biomarker of response/progression on antiangiogenic therapy. CTCs did not reflect response or progression in this population of patients, likely due to lengthy prior exposure to letrozole. Supported in part by Genentech and Novartis. [Table: see text]

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