Determination of genotoxicity by the Comet assay applied to murine precision-cut lung slices

Precision-cut lung slices (PCLSs) are an organotypic lung model that is widely used in pharmacological, physiological, and toxicological studies. Genotoxicity testing, as a pivotal part of early risk assessment, is currently established in vivo in various organs including lung, brain, or liver, and in vitro in cell lines or primary cells. The aim of the present study was to provide the three-dimensional organ culture PCLS as a new ex vivo model for determination of genotoxicity using the Comet assay. Murine PCLS were exposed to increasing concentrations of ethyl methane sulfonate 'EMS' (0.03-0.4%) and formalin (0.5-5mM). Tissue was subsequently dissociated, and DNA single-strand breaks were quantified using the Comet assay. Number of viable dissociated lung cells was between 4×10(5) and 6.7×10(5)cells/slice. Even treatment with EMS did not induce toxicity compared to untreated tissue control. As expected, DNA single-strand breaks were increased dose-dependently and significantly after exposure to EMS. Here, tail length rose from 24μm to 75μm. In contrast, formalin resulted in a significant induction of DNA cross-links. The effects induced by EMS and formalin demonstrate the usefulness of PCLS as a new ex vivo lung model for genotoxicity testing in the early risk assessment of airborne substances in the future.

Defective diacylglycerol-induced Ca2+ entry but normal agonist-induced activation responses in TRPC6-deficient mouse platelets

BACKGROUND

Platelet adhesion, activation and aggregation at sites of vascular injury are essential processes for primary hemostasis. Elevation of the intracellular Ca(2+) concentration is a central event in platelet activation but the underlying mechanisms are not fully understood. Store-operated calcium entry (SOCE) through Orai1 was shown to be the main Ca(2+) influx pathway in murine platelets, but there are additional non-store-operated Ca(2+) (non-SOC) and receptor operated Ca(2+) (ROC) channels expressed in the platelet plasma membrane.

OBJECTIVE

Canonical transient receptor potential (TRPC) channel 6 is found both in human and murine platelets and has been proposed to mediate diacylglycerol (DAG) activated ROCE but also a role in the regulation of SOCE has been suggested.

METHODS

To investigate the function of TRPC6 in platelet Ca(2+) signaling and activation, we analyzed platelets from mice deficient in TRPC6 using a wide range of in vitro and in vivo assays.

RESULTS

In the mutant platelets, DAG activated Ca(2+) influx was found to be abolished. However, this did not significantly affect SOCE or agonist induced Ca(2+) responses. Platelet function in vitro and in vivo was also unaltered in the absence of TRPC6.

CONCLUSION

Our results indicate that DAG activated ROCE is mediated exclusively by TRPC6 in murine platelets, but this Ca(2+) influx has no major functional relevance for hemostasis and thrombosis. Further, in contrast to previous suggestions, based on studies with human platelets, TRPC6 appears to play an insignificant role in the regulation of SOCE in murine platelets.

P4-13-01: Pain Severity and Analgesic Use Associated with Skeletal-Related Events in Patients with Advanced Breast Cancer and Bone Metastases

Background: Skeletal-related events (SREs), which include pathologic fracture (PF), radiation to bone (RB), surgery to bone (SB), and spinal cord compression (SCC), occur frequently in patients with bone metastases and can lead to debilitating clinical consequences such as functional impairment and bone pain. Denosumab (XGEVA®) is a fully human monoclonal antibody against RANKL, shown to be superior to zoledronic acid (ZA; Zometa®) for the prevention of SREs in patients with solid tumors. Denosumab also delayed the onset of moderate or severe pain compared with ZA. The pain severity and analgesic use associated with each type of SRE were assessed in patients with advanced breast cancer and bone metastases.

Methods: Eligible patients received denosumab 120 mg SC or ZA 4 mg (adjusted for renal function) IV every 4 weeks in a randomized, multinational, double-blind, double-dummy trial. Patient-reported pain was assessed with the Brief Pain Inventory (BPI; 0 no pain to 10 severe pain) at baseline (BL) and at each monthly visit. Opioid and non-opioid analgesic use was recorded and scored using the Analgesic Quantification Algorithm (AQA; 0 no analgesic use to 7 > 600mg oral morphine equivalent/day). Data from the two treatment arms were pooled for this analysis. Pain and analgesic use were evaluated from 6 months prior to and 6 months after the first on-study SRE for each patient. The comparator group included patients without an SRE and was centered at the median time from randomization to first SRE by SRE type, with corresponding 12 month assessments. The proportion of patients with moderate/severe pain (BPI worst pain score > 4) and proportion of patients shifting from no/low analgesic use (AQA ≤ 2) at baseline to strong opioid use (AQA ≥ 3) were reported by month and by SRE type, and are summarized by mean relative change (%) across the time period.

Results: In total, 687 patients with first on-study SRE occurrences (PF=450, RB=201, SCC=16, SB=20) were analyzed. A similar proportion of patients with and without a PF had moderate/severe pain, but a higher proportion of patients with a PF shifted from no/low analgesic use to strong opioid use (mean relative increase 80%). Starting 3 months prior to the event, more patients with RB than those without had moderate/severe pain (27% mean relative increase) and shifted from no/low analgesic use to strong opioid use (mean relative increase 269%). Similar pain and analgesic use patterns were noted for patients with SCC (mean relative increase in pain: 63%; in AQA shift: 913%). More patients with SB than those without had moderate/severe pain in the 6 months leading on to SB (mean relative increase 51%). The difference was attenuated after SB, but during this time a much higher proportion of patients with SB shifted from no/mild opioid use to strong opioid use (mean relative increase 220%).

Discussion: SREs are associated with increased pain severity and analgesic use in patients with advanced breast cancer and bone metastasis. Patterns of pain severity and analgesic use differed by SRE type. Effective treatments to prevent SREs can decrease pain and the need for treatment with opioid analgesics.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-13-01.

OT1-01-03: A Phase 3 Randomized, Double-Blind, Placebo-Controlled Multicenter Study Comparing Denosumab with Placebo as Adjuvant Treatment for Women with Early-Stage Breast Cancer Who Are at High Risk of Disease Recurrence (D-CARE)

Background

Bone is a common site of distant recurrence in women with early-stage breast cancer. Cancer cells are thought to stimulate osteoclast-mediated bone resorption, which releases growth factors and cytokines that promote tumor growth. RANK Ligand (RANKL) is the key mediator of osteoclast-induced bone destruction. In preclinical studies, RANKL inhibition reduced the incidence of bone and lung metastases, suppressed tumor progression, and prolonged survival of tumor-bearing mice. Effects were additive with hormonal, chemotherapy, or targeted therapies. Denosumab is a fully human monoclonal antibody against RANKL, approved in the U.S. for the prevention of skeletal-related events in patients with bone metastases from solid tumors. In patients with castrate-resistant prostate cancer, denosumab significantly improved bone metastasis-free survival (BMFS) compared to placebo. The D-CARE trial evaluates BMFS effects of denosumab in women with stage II or III breast cancer.

Methods: Women with node-positive or locally advanced (T3 or T4) disease, and known hormone and HER-2 receptor status are eligible. Standard-of-care adjuvant or neoadjuvant chemo-, endocrine, or HER-2 targeted therapy, alone or in combination must be planned with curative intent. Women with a prior history of breast cancer (other than ductal carcinoma in situ [DCIS] or lobular carcinoma in situ [LCIS]) or distant metastasis, oral bisphosphonate (BP) use within 1 year or any intravenous BP use are excluded. Patients are randomized 1:1 to receive denosumab 120 mg or placebo subcutaneously monthly for 6 mos, then every 3 mos, for a total of 5 yrs treatment. All patients receive vitamin D (≥ 400 IU) and calcium (≥ 500 mg) supplements. Primary endpoint of this event-driven trial is BMFS. Secondary endpoints include disease-free (DFS) and overall survival. The study is powered for both, BMFS and DFS. Safety, quality of life assessments and biomarkers are additional endpoints. The trial, sponsored by Amgen Inc. and registered with the ClinicalTrials.gov identifier NCT01077154 began enrolling patients in June 2010. PG and DF are supported in part by the Avon Foundation, NY.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT1-01-03.