Recently biomechanics of cancer cells, in particular stiffness or elasticity, has been identified as an important factor relating to cancer cell function, adherence, motility, transformation and invasion. We report on the nanomechanical responses of metastatic cancer cells and benign mesothelial cells taken from human body cavity fluids using atomic force microscopy. Following our initial study (Cross et al 2007 Nat. Nanotechnol. 2 780-3), we report on the biophysical properties of patient-derived effusion cells and address the influence of cell morphology on measured cell stiffness. Using a cytocentrifugation method, which yields morphologically indistinguishable cells that can be prepared in 1 min and avoids any possible artifacts due to 12 h ex vivo culture, we find that metastatic tumor cells are more than 80% softer than benign cells with a distribution over six times narrower than that of normal cells. Consistent with our previous study, which yielded distinguishable cell populations based on ex vivo growth and morphological characteristics, our results show it is unlikely that morphology alone is sufficient to explain the difference in elastic moduli for these two cell types. Moreover, analysis of non-specific cell adhesion inherent to tumor and normal cells collected from patients show surface adhesion of tumor cells is ∼33% less adhesive compared to that of normal cells. Our findings indicate that biomechanical-based functional analysis may provide an additional platform for cytological evaluation and diagnosis of cancer in the future.

The injection of lidocaine directly into the nipple greatly increases the feasibility of duct cannulation and improves subject comfort. Confirmation of duct cannulation and lavage can be documented with ductoscopy and ultrasound imaging. These procedures can be added to ductal lavage to facilitate its use as a research tool.

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B65 Background The majority of breast cancers originate in the ductal epithelium of the breast. Ductal lavage provides a minimally invasive tool for assessing epithelial cells and their microenvironment. Previous studies of pathological atypical hyperplasia on biopsy, and cytological aypia in nipple aspirate fluid (NAF) and random fine needle aspiration (FNA) have suggested that these cells are precancerous because of the subsequent increased risk of cancer. It has therefore been hypothesized that serial ductal lavage could be used to identify atypia and monitor the effects of chemoprevention over time. This report is part of a larger study examining the differences in hormone levels and cytology between ducts and their reproducibility. This report presents a cohort of women unselected for risk who voluntarily underwent ductal lavage of the same ducts on two occasions six months apart. Samples were analyzed for epithelial cells and macrophages. Methods A total of 107 women were recruited in this IRB-approved prospective study to undergo ductal lavage of three fluid or non-fluid-yielding ducts within a breast. Women were unselected for risk: the average Gail score was 1.67 and ten women had a history of contralateral breast cancer. The average age was 51 years. Fifty-four women were premenopausal, 4 were perimenopausal and 49 were postmenopausal. Samples were submitted in a blinded fashion to a central laboratory and were analyzed by duct for both macrophage and epithelial cell number on Papanicolaou-stained slides. If adequate epithelial cells were present (>10), a diagnosis of each duct (benign, mild atypia, or marked aytpia) was made by an experienced cytopathologist. Results Of the 107 women, 317 (99%) ducts were successfully cannulated without regard to nipple aspirate fluid (NAF) production. Thirty ducts in 23 women were diagnosed with mild or marked atypia on either of the two visits. Of these ducts, 16 were diagnosed at the initial visit and 13 at the second visit. Only one duct was diagnosed with mild atypia on both visits, in a woman with a Gail score of 1.4. Cellular atypia in ductal lavage was not reproducible at a six month interval (p=0.45). This absence of reproducibility was seen in women at all risk levels. Macrophage and epithelial cell numbers also showed a lack of reproducibility at the six month interval (p=0.31 and p=0.22, respectively). Conclusion Atypia on cytology in ductal lavage in women unselected for risk was not reproducible at a six month interval, suggesting that a single diagnosis of atypia on lavage should not be used as a marker for the identification of women at risk. Further studies are necessary to indicate whether persistent atypia over an extended interval could represent an elevated risk for breast cancer. In addition, ongoing studies are being performed to identify better cellular markers of premalignancy and subsequent risk. Citation Information: Cancer Prev Res 2008;1(7 Suppl):B65.