While significant progress has been made in the fight against cancer largely due to drastic improvements in diagnostic techniques and treatment methods, therapies have been much less effective in combating those tumors that have spread to other organs, or metastasized. Specific subsets of cancer cells, known as cancer stem cells, may be primarily responsible for establishing these metastatic colonies, but the exact mechanisms are unknown, in no small part due to a lack of a universal molecular definition for cancer stem cells, through which these cells can be isolated and studied. For this research project, the research team hypothesizes that cancer stem cells possess inherent rheological and viscoelastic properties that facilitate metastatic invasion and growth, and that these mechanical properties may be used to specifically identify cancer stem cells in complement to the molecular phenotype. The team will test this hypothesis by conducting studies that aim (1) to determine correlations between cellular mechanical properties and the CD44+/CD24- breast cancer stem cell phenotype, and (2) to identify regulatory crosstalk between cellular mechanical properties and the CD44+/CD24- breast cancer stem cell phenotype. Intellectual Merit: This research seeks to address complex issues at the interface of the physical sciences and oncology. Therefore, principles and techniques from chemical engineering, biophysics, and medical sciences will be employed to achieve the study goals. The transformative studies and novel methodologies in this project will ultimately reveal molecular pathways regulating mechanical properties of cancer stem cells, subject matter that remains unaddressed by the scientific community to date. Broader impacts: This project integrates multidisciplinary research with education and will have broader impacts on engineering and the life sciences, training of the next generation of bioengineering researchers, biotechnology development, and public health. The PI and co-PIs will mentor students participating in this research project through experiences that allow them to advance their own scientific knowledge as well as contribute to the wider scientific body, gain employment in engineering or biological fields, or pursue advanced degrees in these disciplines. This project will also have a significant impact on society and public health, as the research findings can be used to develop diagnostics, prognostics, and therapeutics to more specifically target deadly breast cancer stem cells.