In the first 3 quarters of FY 2011, the FACS Core Lab provided service to 25 NCI labs or branches and 2 other institutes. From these labs, there were 77 principal investigators using the FACS Core Facility. These labs, with the number of principal investigators and the number of individuals using the FACS Core in parentheses, are: ATC-Gaithersburg (1 principal investigator, 1 user), CCBB (5,20), Dermatology Branch (1,1), Genetics Branch (3,13), HAMB (1,1), LBMB (3,7), LCB (4,7), LCBG (11,33), LCMB (5,17), LCO (3,12), LCB (1,4), LEC (3,11), LHC (3,13), LICB (2,16), LM (2,2), LMB (5,14), LMP (5,12), LP (3,4), LRBGE (1,1), MBTL (4,5), Medical Oncology Branch (5,15), Pediatric Oncology Branch (1,3), Radiation Oncology Branch (3,6), Surgery Branch (2,2), Urologic Oncology Branch (1,1), NHLBI (1,1), and NIDCR (2,4). From these labs, 211 scientists have used the FACS Core in the first 9 months of FY 2011 and of these, 83 were new to the Core lab this past year and received training from the core staff. 189 people used the flow cytometers and sorting was provided by the core lab staff to 89 users. Identifying and studying cancer stem cells is one of the major research areas of the FACS Core Lab users. A number of NCI labs are using flow cytometry and fluorescence-activated cell sorting to identify and sort the cancer stem cell by membrane antigen expression using monoclonal antibodies or with a functional assay involving active membrane substrate transport. Investigators in CCBB, MBTL, LEC, LHC, and LCBG are studying cancer stem cells from breast, ovarian, hepatic, thyroid, pancreatic, and lung carcinomas. The LSRII flow cytometer, the FACS Vantage cell sorter, and the new special order FACS Aria, because each is equipped with a UV laser, are frequently used for these assays. Transfection of cells with genes expressing fluorescent reporters is a technique used by the majority of the labs using the FACS Core. The FACS Core cytometers and cell sorters have been equipped with specific lasers to allow detection and sorting of cells labeled with any of the green, yellow, blue, red, and UV fluorescent proteins or with combinations of these fluorescent reporters. Sorted transfected cells are used to prepare protein, DNA, and RNA that can be used in Western blotting and microarrays. Sorted cells are also used to determine effects of siRNA, to look at signaling proteins, or may be further passaged to create stable cell lines. Fluorescent reporter proteins may also be linked to luciferase. Tumor cell lines have then been sorted based on their expression of green or red fluorescent protein to establish cell lines with high levels of luciferase. These cells have then been used to establish tumors in mice and to image metastasis. Flow cytometry is also frequently used for looking at cell growth (cell cycle analysis) and mechanisms of cell death (apoptosis) to examine actions of cancer drugs. In addition to 1 co-authored publication, 17 additional publications this year have included work done in the FACS Core and, of these, 5 acknowledged the assistance of the FACS Core staff. These publications were authored by investigators in CCBB, Genetics Branch, LBMB, LCBG, LCMB, LEC, LICB, LMB, and Radiation Oncology Branch.