Defining the populations of tumor-initating cells that are present in tumors is a first step in developing therapeutics to target these cells. We show here that both CD44posCD24neg and CD44posCD24pos cell populations in estrogen receptor (ER) α–negative breast tumors are tumorigenic in murine xenograft models. We also describe a third population of xenograft-initiating cells (XIC) enriched in CD44posCD49fhiCD133/2hi cells that display heightened tumorigenicity, self-renewal in vivo, and the capacity to give rise to functional and molecular heterogeneity. Consistent with their capacity for self-renewal, these cells express elevated levels of Sox2, Bmi-1, and/or Nanog and their CpG islands are hypermethylated relative to nontumorigenic cells. These differences in methylome regulation may be responsible for the dramatic functional differences between the two populations. The identification of CD44posCD49fhiCD133/2hi XIC in ER-negative tumors may lead to expanded understanding of these tumors and ultimately the development of therapeutics designed to specifically target the cells.

Purpose: To use swept-source optical coherence tomography and swept-source optical coherence tomography angiography to investigate potential relationships between choroidal vascular hyperpermeability (CVH) seen with indocyanine green angiography (ICGA), choriocapillaris flow density, and choroidal thickness in eyes with pachychoroid pigment epitheliopathy. Methods: Patients with pachychoroid pigment epitheliopathy were prospectively imaged with 12-mm × 12-mm swept-source optical coherence tomography, 12-mm × 12-mm swept-source optical coherence tomography angiographyA, and ICGA. Binarized choriocapillaris OCTA images were superimposed with ICGA images in which CVH area had been isolated. Choriocapillaris flow density within or outside the quadrants of CVH was calculated and the ratio of these two values was determined. The presence of CVH and choroidal thickness was evaluated at 9 locations within a central 3-mm × 3-mm area to explore the relationship between these 2 factors. Results: Ten eyes from 10 patients were enrolled in the present study. Choriocapillaris flow density within quadrants of CVH area was significantly lower compared with quadrants without CVH (P < 0.001). The mean choriocapillaris flow density ratio was 0.86 ± 0.10 (range: 0.65–0.99). From among the 90 locations in 10 study eyes, 48 were within areas of CVH. Choroidal thickness was greater in quadrants of CVH compared with areas without CVH (P < 0.001, 455 ± 122 µm vs. 297 ± 93 µm). Conclusion: Reduced choriocapillaris flow density, increased choroidal thickness, and CVH appear to co-localize in eyes with pachychoroid pigment epitheliopathy.