Tumor-cocultured monocytes promote invasion of BCP-ALL cells via CXCL10. Normal monocytes and patient (cALL or pre-B ALL) blasts were either cultured alone or together for 24 hours. Thereafter, the cell-free culture supernatants were used for an in vitro invasion assay with (A) patient cALL, (B) REH, (C) RS4;11, and (D) NALM6 cells in the presence or absence of anti-CXCL10 (10 μg/mL; left panels of the respective figure). Cells invading through the Matrigel-coated transwell membranes were counted as described in “Tumor cell invasion and migration assay.” In some cases, supernatants from monocytes treated with LPA (100 ng/mL) for 24 hours, after coculture with patient blasts were also assayed. CM indicates conditioned media. *P < .05, versus Mo + cALL or Mo + pre-B ALL (with or without LPA). Right panels of each figure represent the invasion capacity of the BCP-ALL cells (ie, patient cALL, REH, RS4;11, or NALM6) in the presence of the indicated doses of recombinant human CXCL10. *P < .05 with respect to media. Data are mean ± SEM of a representative experiment.