CAL-101 inhibits CLL cell chemotaxis toward CXCL12 and CXCL13 and migration beneath MSCs (pseudoemperipolesis). (A) CLL cells were incubated in medium alone (control) or medium containing 5μM CAL-101, and then allowed to migrate towards 200 ng/mL CXCL12 or 1 μg/mL CXCL13; or control cells without chemokine. The bar diagram represents the mean chemotaxis (± SEM) of CLL cells from 10 different patients in the presence or absence of CAL-101. Chemotaxis toward both CXCL12 and CXCL13 was significantly inhibited by CAL-101, with P < .05, as indicated by the asterisks. (B) Representative phase-contrast photomicrographs displaying CLL cell migration beneath TSt-4 or 9-15C stromal cells when CLL were either untreated (control) or pretreated with 5μM CAL-101 (CAL-101). Pseudoemperipolesis is characterized by the dark appearance of CLL cells that have migrated into the same focal plane as the stromal cells. There are numerous migrated CLL cells in the control wells (on the left), as indicated by the arrows, but only a few such cells in wells containing CLL cells pretreated with CAL-101 (on the right). (C) The bar diagram represents the mean pseudoemperipolesis (± SEM) of CLL cells from 9 different patients beneath of each of the 2 types of stromal cells in the presence or absence of CAL-101. Pseudoemperipolesis beneath TSt-4 or 9-15C stromal cells was significantly inhibited by CAL-101, with P < .05, as indicated by the asterisks.