Figure 4. SRR2 reporter activity is a novel marker to enrich for a more tumorigenic cell subset within the CD44/CD24 population.

A. FACS dot plot showing the sorting scheme of the RU CD44^High/CD24^Neg and RR CD44^High/CD24⁻ subsets. Percentages of gated populations from the live single cell population are reported. Cells were subsequently collected and seeded at 2500 cells/well in a 96-well Matrigel colony formation assay. Photographs were taken at 5X objective on Day 7. B. Purified RU CD44^High/CD24⁻ and RR CD44^High/CD24⁻ cell subsets as described above from MDA-MB-231 SRR2 cells were resuspended in 1:1 Matrigel/PBS. 4000 cells were injected with 200 μL of Matrigel/PBS solution subcutaneously bilaterally into 6-8 week old SCID/Beige females. Photographs depict representative tumors at Day 40. Resultant tumors were dissociated and analyzed by flow cytometry for GFP and CD44 expression. Representative 2 of 6 mice shown. C. Fresh TNBC patient tumors were dissociated, infected with the lentiviral SRR2 reporter, and assessed for GFP by flow cytometry.