Lack of cytotoxic response to CEP-701 in a FLT3/PM sample is associated with lack of inhibition of activated p44/42 MAPK (ERK1/2). Whole-cell lysates from the 2 FLT3/PM samples shown in Figure 5B were examined by Western blotting for STAT5 and MAPK phosphorylation status. The blots were then stripped and reprobed to determine the STAT5 and MAPK protein expression. Patient numbers (from Tables 1, 2 and 3) are noted for each sample.