In situ Search for Breast Cancer Stem Cells and Their Niche: The Film Sheet Epoxy Resin Embedding Method and Breast Cancer Stem Cells

Because of the significant increase in the number of cases, breast cancer has attracted much attention in Japan. Breast cancer now kills more than 10,000 Japanese women each year. Recent reports of small subgroup of cells called “cancer stem cells” that have self-renewal and differentiating abilities and are capable of forming tumors have caused a paradigm shift in our understanding of cancer1. For example, because cancer stem cells contain a type of ATP-binding cassette transporter, they are highly resistant to anticancer agents2. Furthermore, cancer stem cells are greatly affected by their “niche”, and/or microenvironment3. We believe that by focusing on cancer stem cells and their niches, new treatments to suppress the recurrence and metastasis of tumor cells can be developed. Both CD44+/CD24-/low and aldehyde dehydrogenase 1 are candidate markers for identifying cancer stem cells in breast cancer4, 5. However, the location of breast cancer stem cells has not been identified. Therefore, we are using a new technology for in situ identification of breast cancer stem cells, the film sheet epoxy resin embedding method (FSEM)6.