In order to investigate the effect of long-term exposure to LDE225 ± nilotinib on CP-CML within a more complex microenvironment, we performed in vitro stromal co-culture in which CD34+ CP-CML cells were directly inoculated into supportive stromal co-cultures with incremental concentrations of LDE225 (10–100 nM) ± nilotinib 1 μM added to the stromal co-culture media. Here, CD34 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.