Purpose: Circulating tumor cells (CTC) in peripheral blood of patients potentially represent a fraction of solid tumor cells available for more frequent pharmacodynamic assessment of drug action than is possible using tumor biopsy. However, currently available CTC assays are limited to cell membrane antigens. Here, we describe an assay that directly examines changes in levels of the nuclear DNA damage marker γH2AX in individual CTCs of patients treated with chemotherapeutic agents.Experimental Design: An Alexa Fluor 488-conjugated monoclonal γH2AX antibody and epithelial cancer cell lines treated with topotecan and spiked into whole blood were used to measure DNA damage-dependent nuclear γH2AX signals in individual CTCs. Time-course changes in both CTC number and γH2AX levels in CTCs were also evaluated in blood samples from patients undergoing treatment.Results: The percentage of γH2AX-positive CTCs increased in a concentration-dependent manner in cells treated with therapeutically relevant concentrations of topotecan ex vivo. In samples from five patients, percent γH2AX-positive cells increased post-treatment from a mean of 2% at baseline (range, 0-6%) to a mean of 38% (range, 22-64%) after a single day of drug administration; this increase was irrespective of increases or decreases in the total CTC count.Conclusions: These data show promise for monitoring dynamic changes in nuclear biomarkers in CTCs (in addition to CTC count) for rapidly assessing drug activity in clinical trials of molecularly targeted anticancer therapeutics as well as for translational research.

This study was conducted to evaluate a strategy of using feeding stalls to protect low-ranking sows in group-housing systems. Sows (n = 150, parity 1–9) were mixed at weaning in pens of 15 sows. Control pens allowed sows to access feeding stalls for 1 h of feeding daily during the initial 2 d after mixing. Treatment pens allowed sows to access feeding stalls continuously. Social rank was determined based on outcomes of aggressive interactions among sows after mixing. Low-ranking sows used the feeding stalls more frequently (P < 0.01) than high-ranking sows during the initial 6 h after mixing. Continuous stall access reduced frequency of aggressive interactions (P = 0.05) and, consequently, reduced skin lesions (P = 0.05) of sows in the pen. Neither continuous access to stalls nor social rank affected performance of sows. These results suggest that low-ranking sows used feeding stalls as hiding spaces to escape from aggressive interactions during mixing, which reduced skin lesions caused by aggression and improved the welfare of sows in the group-housing system studied.