Acute lymphoblastic leukemia (ALL) with translocation t(4;11) is found in 60–85% of infants with ALL and is often refractory to conventional chemotherapeutics after relapse. Using the t(4;11) ALL line SEM, we evaluated chemotherapy resistance in NOD.CB17-Prkdcscid/J mice. SEM cells were injected into the tail vein and engraftment was monitored by flow cytometry. Once engraftment was observed, mice were injected intraperitoneally with phosphate-buffered saline (PBS), or vincristine (0.5mg/kg body...