CXCR4 and B-cell chronic lymphocytic leukemia: Comparable as in our previous study on HSPCs [13], three different cell polarization states of CLL cells could be discriminated (Fig 3): i) cells with a spherical appearance and a diffuse subcellular distribution of CD50 and CXCR4 (Fig 3B), ii) CLL cells with a spherical appearance and a polarized distribution of CD50 and CXCR4 (Fig 3C) and iii) CLL cells with CD50 being enriched at the rear and CXCR4 at the front (Fig 3A).