Figure 7.

Pbx2 and Pbx3 are required for maintenance of MLL-mediated transformation. (A) The relative expression levels of Pbx1, Pbx2, and Pbx3 transcripts were determined by real-time PCR analysis of MLL-transformed cells (indicated below) from the fourth round of serial replating (error bars indicate standard deviations of triplicate analyses). Results are expressed relative to levels observed in cells transformed by E2A-HLF. (B) Bar graph indicates the total relative levels of Pbx transcripts expressed in cells transformed by various oncogenes (indicated at bottom) from the fourth round of plating in methylcellulose cultures. The relative abundance of Pbx transcripts was determined using the Ct value method, assuming that all primers were optimized to generate equal PCR efficiencies. (C) Pbx2^−/− myeloid progenitors transformed by various oncogenes (indicated on left) were secondarily transduced with lentiviral vectors encoding shRNAs specific for Pbx3 (P3 #1 or P3 #2). Colony numbers are shown relative to cells secondarily transduced with lentiviral vector alone. Error bars indicate standard deviations of at least two independent experiments.